Applanation tonometry and central corneal thickness

The effect of different eyelid speculums compared to manual eyelid opening on intraocular pressure in children under general anesthesia

PURPOSE

To evaluate the effect of 4 commonly used eyelid speculums on intraocular pressure (IOP) among children undergoing examination under anesthesia.

METHODS

In this comparative cross-sectional study, IOP of children undergoing EUA at Soroka Medical Center was measured by manually opening the eyelids and the result was compared to measurements taken with 4 commonly-used speculums. Barraquer and Alfonso speculums were used in patients of all ages, whereas V- and U-shaped speculums were used in patients older than 6 months of age only. All measurements were taken using a Tono-Pen tonometer.

RESULTS

Data were collected from 41 eyes of 21 patients (8 eyes ≤ 6 months of age). Mean age was 3.6 years (range 10 days-14 years), and 52% were male. Mean IOP without an eyelid speculum was 14.3 ± 4.7 mmHg. In comparison to manual eyelid opening, the mean IOP measurement with the Barraquer speculum did not differ significantly (14.7 vs. 14.3 mmHg, respectively, p = 0.139). However, all other types of speculums significantly increased IOP measurements (14.3 vs. 18.9 mmHg, p < 0.001) for Alfonso speculum, (15.0 vs. 19.0 mmHg, p < 0.001) for V-shape speculum, and (15.0 vs. 18.8 mmHg, p < 0.001) for the U-shape speculum. The results were the same when the data from each eye were analyzed separately.

CONCLUSIONS

The Barraquer speculum did not affect IOP measurements under general anesthesia among children up to age 14 years. IOP measurements obtained with other types of speculums are expected to be overestimated.

KEY MESSAGES

What is known: • Obtaining accurate IOP measurements in children with glaucoma is important to assess disease progression and guide treatment decisions.

WHAT IS NEW

• The Barraquer speculum did not affect IOP measurements under general anesthesia among children up to 14 years. • IOP measurements obtained with other types of speculums are usually overestimated.

Comparison of Efficacy and Ocular Surface Assessment Between Preserved and Preservative-Free Brimonidine/Timolol Fixed-Combination Eye Drops in Glaucoma Patients: A Parallel-Grouped, Randomized Trial

The objectives of the study were to compare the efficacy and safety using ocular surface assessment between preserved and preservative-free brimonidine/timolol fixed-combination eye drops in glaucoma or ocular hypertension patients. Methods: This study was designed as a prospective, multicenter (three institutions), investigator-masked, parallel-grouped randomized clinical trial. The primary outcomes were corneal and conjunctival staining score, ocular surface disease index (OSDI) score, drug tolerance, and adherence rates at 12-week visits. The secondary outcomes were corneal and conjunctival staining score, OSDI score at 4-week visits and intraocular pressure (IOP), tear-film break-up time (TBUT), and bulbar/limbal hyperemia score at the 4- and 12-week visits. For safety assessment, best-corrected visual acuity (BCVA), systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), and physical examination at 4 and 12 weeks and adverse events during the whole study period were analyzed. Results: Overall, 59 patients were enrolled and randomized into each group (29 preserved and 30 preservative-free). At the endpoint, 5 patients in the preserved group and 2 patients in the preservative-free group dropped out, leaving 24 and 28 patients in the preserved and preservative-free groups, respectively. Baseline characteristics showed no significant difference between the groups including age and sex. At the 12-week visit, intra-group change of OSDI scores did not change significantly compared to the baseline scores in both preserved and preservative-free groups (p = 0.791, 0.478, respectively). On the contrary, the corneal staining score and the conjunctival staining score showed a significant increase compared to the baseline score in the preserved group (p = 0.015, 0.009, respectively). Regarding drug satisfaction, higher proportions of patients in the preservative-free group reported convenience of installation (p = 0.002). Also, stinging and burning sensations in drug tolerance showed better results in the preservative-free group with a significant difference (p = 0.011). Safety assessment regarding systemic side effects such as SBP, DBP, and HR showed similar results between the preserved and preservative-free groups (p = 0.711, 0.232, 0.666, respectively). Conclusions: Preservative-free brimonidine/timolol showed comparable efficacy and safety, better corneal and conjunctival staining score with convenience of installation, and lower stinging and burning sensation. It is expected to be a proper treatment option for patients with glaucoma or ocular hypertension.

Immediate Effects of Goldmann Applanation Tonometry on Central Corneal Thickness Measurements Using Contact and Non-contact Pachymetry Methods

PURPOSE

The objective was to evaluate the immediate impact of Goldmann Applanation Tonometry (GAT), a gold-standard intraocular pressure measurement technique, on the reliability of central corneal thickness (CCT) measurements and to compare the outcomes between contact and non-contact pachymetry methods.

METHODS

Fifty-one adult participants without ocular pathology were enrolled. Serial CCT measurements were conducted using three different pachymetry modalities across three days, both at baseline and post-GAT: Day 1 with an ultrasound pachymeter (USP), Day 2 using optical low-coherence reflectometry (OLCR), and Day 3 via anterior segment optical coherence tomography (AS-OCT). The study involved comparing mean CCT and CCT standard deviation at baseline and post-GAT using one-way analysis of variance (ANOVA) and paired t-tests.

RESULTS

In the 610 CCT measurements performed, mean CCT did not show significant changes post-GAT overall or by modality (USP: +2.20 microns, p=0.63; OLCR: +1.0 microns, p=0.93; AS-OCT: +0.40 microns, p=0.95). However, contact USP consistently produced thicker corneal readings than non-contact OLCR and AS-OCT both at baseline and post-GAT (p < 0.0001). Notably, there was a significant increase in CCT standard deviation (+51.1%) and a decrease in adherence to technical repeatability specifications with contact USP following GAT (from 55% to 33%, p < 0.05).

CONCLUSIONS

The study suggests that contact intraocular pressure measurement methods like GAT may influence the reliability and repeatability of CCT measurements, as observed in our increased CCT measurement standard deviations. This could have important implications for accurate diagnosis and treatment planning for various ocular conditions. Given the study's limited sample size, further research may be warranted.

Corneal stromal mapping characteristics in normal corneas using anterior segment SD-OCT

This study investigated how normal corneal stromal profiles change with age, sex, and corrected intraocular pressure (IOP). A retrospective observational analytical study was conducted in Jordan, employing anterior segment spectral-domain optical coherence tomography AS-OCT, a measured corneal stromal thickness (CST) in 134 eyes across the central 6-mm corneal diameter. People between the ages of 18 and 79 were included, and the mean CST values were linked to age groups, IOP, and cis-gender populations, with the exclusion of certain eye conditions. The central stroma was thinnest at 484.6 (±32.6) μm, contrasting with the outer peripheral superior zone's maximum thickness at 549.3 (±40.6) μm. A positive correlation between CST and the 30-49 age group was noted. In conclusion, this study highlights a centrifugal CST distribution, with the central stroma being the thinnest and the superior stroma being the thickest. AS SD-OCT, employing novel algorithms, proves vital in refractive surgery planning and corneal disease diagnosis. The research offers valuable insights into age, gender, and IOP interactions with corneal stromal characteristics, enhancing clinical strategies for corneal pathologies in the Jordanian population.

Advanced bioengineering strategies broaden the therapeutic landscape for corneal failure

The cornea acts as the eye foremost protective layer and is essential for its focusing power. Corneal blindness may arise from physical trauma or conditions like dystrophies, keratitis, keratoconus, or ulceration. While conventional treatments involve medical therapies and donor allografts-sometimes supplemented with keratoprostheses-these options are not suitable for all corneal defects. Consequently, the development of bioartificial corneal tissue has emerged as a critical research area, aiming to address the global shortage of human cornea donors. Bioengineered corneas hold considerable promise as substitutes, with the potential to replace either specific layers or the entire thickness of damaged corneas. This review first delves into the structural anatomy of the human cornea, identifying key attributes necessary for successful corneal tissue bioengineering. It then examines various corneal pathologies, current treatments, and their limitations. Finally, the review outlines the primary approaches in corneal tissue engineering, exploring cell-free, cell-based, and scaffold-based options as three emerging strategies to address corneal failure.

The relationship between intraocular pressure and glaucoma: An evolving concept

Intraocular pressure (IOP) is the most important modifiable risk factor for glaucoma and fluctuates considerably within patients over short and long time periods. Our field's understanding of IOP has evolved considerably in recent years, driven by tonometric technologies with increasing accuracy, reproducibility, and temporal resolution that have refined our knowledge regarding the relationship between IOP and glaucoma risk and pathogenesis. The goal of this article is to review the published literature pertinent to the following points: 1) the factors that determine IOP in physiologic and pathologic states; 2) technologies for measuring IOP; 3) scientific and clinical rationale for measuring diverse IOP metrics in patients with glaucoma; 4) the impact and shortcomings of current standard-of-care IOP monitoring approaches; 5) recommendations for approaches to IOP monitoring that could improve patient outcomes; and 6) research questions that must be answered to improve our understanding of how IOP contributes to disease progression. Retrospective and prospective data, including that from landmark clinical trials, document greater IOP fluctuations in glaucomatous than healthy eyes, tendencies for maximal daily IOP to occur outside of office hours, and, in addition to mean and maximal IOP, an association between IOP fluctuation and glaucoma progression that is independent of mean in-office IOP. Ambulatory IOP monitoring, measuring IOP outside of office hours and at different times of day and night, provides clinicians with discrete data that could improve patient outcomes. Eye care clinicians treating glaucoma based on isolated in-office IOP measurements may make treatment decisions without fully capturing the entire IOP profile of an individual. Data linking home blood pressure monitors and home glucose sensors to dramatically improved outcomes for patients with systemic hypertension and diabetes and will be reviewed as they pertain to the question of whether ambulatory tonometry is positioned to do the same for glaucoma management. Prospective randomized controlled studies are warranted to determine whether remote tonometry-based glaucoma management might reduce vision loss and improve patient outcomes.

The lack of causal link between myopia and intraocular pressure: Insights from cross-sectional analysis and Mendelian randomization study

OBJECTIVE

This study aimed to explore the potential causal relationship between intraocular pressure (IOP) and myopia.

METHODS

The study included 3,459 patients who underwent corneal refractive surgery at our institution between 2021 and 2023. Preoperative data on IOP, spherical equivalent (SE), axial length (AL), and corneal thickness (CCT) were collected. The association between IOP and myopia was investigated through rank correlation analysis, and causal inference was examined using Mendelian randomization (MR) methods, including MR-Egger, weighted median, mode-based estimation, simple mode, and inverse variance weighted (IVW) approaches. Utilizing summary statistics from genome-wide association studies (GWAS), IOP was considered as the exposure, with myopia as the outcome variable. IVW method was employed for the primary analysis, supplemented by sensitivity analyses.

RESULTS

Cross-sectional analysis revealed a non-significant association between corrected IOP (cIOP) and myopia (r = -0.019, P = 0.12). MR analysis indicated a non-significant genetic causal relationship between cIOP and myopia under the IVW method (OR = 1.001; 95 % CI [0.999-1.003], P = 0.22), a finding corroborated in replication samples (OR = 0.98; 95 % CI [0.96-1.00], P = 0.099).

CONCLUSION

This study did not find a direct causal link between IOP and the development of myopia. These findings challenge the traditional role attributed to IOP in the progression of myopia and highlight the complex, multifactorial process of myopia development. This provides a new perspective on understanding the intricate mechanisms behind myopia progression.

Intraocular Pressure (IOP) in Patients with Acromegaly versus Healthy Controls: A Systematic Review and Meta-Analysis

PURPOSE

Acromegaly is an uncommon condition but affects numerous organ systems. It has been found that patients with acromegaly can experience ocular changes, such as raised intraocular pressure (IOP). Numerous studies have since been carried out to determine whether there is a significant difference between IOP in patients with acromegaly and healthy controls and there is much disagreement in the literature. This study aims to perform a systematic review and meta-analysis to establish whether there is a significant difference in IOP between the two groups in a larger population.

METHODS

A systematic literature search was performed using PubMed, Scopus, and Web of Science to access relevant databases and to locate outcome studies. Eligibility criteria included type of publication, participant characteristics, and report of outcomes. Data analysis was conducted with a fixed-effects model.

RESULTS

Three articles were included in the final analysis. The mean value of IOP corrected for central corneal thickness (IOPcc) for the group of 102 patients with acromegaly was 15.33 with confidence levels of 13.05-17.62 [mmHg]. The mean difference between the control and acromegaly group was 1.17 with confidence levels of 0.64 to 1.70 [mmHg], which was found to be statistically significant (p < 0.001).

CONCLUSION

The results of the meta-analysis indicate that acromegaly is associated with increased IOP. As raised IOP is a risk factor for the development of glaucoma, detailed IOPcc evaluation should be an important procedure in the follow-up visits of patients with acromegaly.

A comparison of iCare and Goldmann applanation tonometry measurements during the COVID-19 pandemic: a retrospective study

PURPOSE

To evaluate factors associated with differences in intraocular pressure (IOP) readings between iCare and Goldmann applanation tonometry (GAT) in established glaucoma patients.

METHODS

This retrospective comparative study included clinical data of 350 eyes from 350 established glaucoma patients who had iCare and GAT IOP measured by an ophthalmic technician and a glaucoma specialist, respectively. The main outcome measure was the difference in IOP measurements of the right eyes with iCare and GAT.

RESULTS

The intraclass correlation coefficient (ICC) between GAT and iCare was 0.90. The mean IOP difference between tonometers was - 0.18 ± 2.89 mmHg. Bland-Altman plots indicated a 95% limit of agreement of - 5.8 to 5.5 mmHg. Central corneal thickness (CCT) and age were significantly correlated with the difference in IOPs of the iCare and GAT. GAT-IOP and age were significantly associated with the absolute difference in measured IOP of the two tonometers. The difference in measurements was not significantly associated with prior glaucoma surgery, average global index of optical coherence tomography, axial length, technician years of experience and certification, and IOP range.

CONCLUSION

Although there is good agreement between the iCare and GAT mean values, these devices are not interchangeable in glaucoma patients due to the wide range of the limit of agreement.

Acta Ophthalmologica 100 years-Overview of selected articles during Acta Ophthalmologica history

We selected and discussed 10 articles in Acta Ophthalmologica since 1923 that changed clinical ophthalmology and treatment protocols, or provided novel findings and perspectives. We are aware that the selection of articles may be debatable and we invite readers to suggest other significant Acta articles. For historians, the article archive of Acta Ophthalmologica is located in Copenhagen.

The influence of altitude on the differences between Goldmann tonometry and Pascal dynamic contour tonometry: An ecological meta-analysis

PURPOSE

A meta-analysis found that including atmospheric pressure as altitude in generalized linear models reveals higher differences between Goldmann tonometry and Pascal dynamic contour tonometry at higher altitudes, with the difference increasing in thinner corneas. To examine the difference in intraocular pressure (IOP) measurements by using Goldman applanation tonometry (GAT) and dynamic contour tonometer (DCT) tonometry in published literature and determine the influence of central corneal thickness (CCT), age, and altitude on that difference.

METHODS

Articles that compare GAT and DCT were selected for an extensive literature review, and the location and altitude of the research centers were found online. CCT and age were analyzed as covariates, when available.

RESULTS

A total of 157 studies including 24,211 eyes of 20,214 patients were included in the study. The results showed that the difference between DCT and GAT was higher at higher altitudes above sea level and increased with thinner corneas. However, the results were different in eyes with corneal transplants, where altitude and CCT had less influence, and in those post-refractive surgery where age was found to influence the difference. Theoretical correction formulas using altitude, CCT, and age were derived from this meta-analysis, but their accuracy and usefulness in clinical practice need validation.

CONCLUSION

The findings suggest that there is a higher risk of underestimating IOP when the Goldmann tonometer is used at a higher altitude, particularly in eyes with glaucoma, thinner corneas, or corneal refractive surgery. Further research is needed to validate the accuracy of the correction formulas derived from this meta-analysis in clinical practice.

Scheimpflug-Based Corneal Biomechanical Analysis As A Predictor of Glaucoma in Eyes With High Myopia

Purpose

To address if corneal biomechanical behavior has a predictive value for the presence of glaucomatous optical neuropathy in eyes with high myopia.

Patients and Methods

This observational cross-sectional study included 209 eyes from 108 consecutive patients, divided into four groups: high myopia and primary open-angle glaucoma (POAG) - HMG, n = 53; high myopia without POAG - HMNG, n = 53; non-myopic with POAG - POAG, n = 50; non-myopic and non-POAG- NMNG, n = 53. Biomechanical assessment was made through a Scheimpflug-camera-based technology. Receiver operating characteristic curves were made for the discrimination between groups. Multivariable logistic regression models were performed to address the predictive value of corneal biomechanics for the presence of glaucoma.

Results

Areas Under the Receiver Operating Characteristic (AUROCs) above 0.6 were found in 6 parameters applied to discriminate between HMG and HMNG and six parameters to discriminate between POAG and NMNG. The biomechanical models with the highest power of prediction for the presence of glaucoma included 5 parameters with an AUROC of 0.947 for eyes with high myopia and 6 parameters with an AUROC of 0.857 for non-myopic eyes. In the final model, including all eyes, and adjusted for the presence of high myopia, the highest power of prediction for the presence of glaucoma was achieved including eight biomechanical parameters, with an AUROC of 0.917.

Conclusion

Corneal biomechanics demonstrated differences in eyes with glaucoma and mainly in myopic eyes. A biomechanical model based on multivariable logistic regression analysis and adjusted for high myopia was built, with an overall probability of 91.7% for the correct prediction of glaucomatous damage.

The ocular mathematical virtual simulator: A validated multiscale model for hemodynamics and biomechanics in the human eye

We present our continuous efforts from a modeling and numerical viewpoint to develop a powerful and flexible mathematical and computational framework called Ocular Mathematical Virtual Simulator (OMVS). The OMVS aims to solve problems arising in biomechanics and hemodynamics within the human eye. We discuss our contribution towards improving the reliability and reproducibility of computational studies by performing a thorough validation of the numerical predictions against experimental data. The OMVS proved capable of simulating complex multiphysics and multiscale scenarios motivated by the study of glaucoma. Furthermore, its modular design allows the continuous integration of new models and methods as the research moves forward, and supports the utilization of the OMVS as a promising non-invasive clinical investigation tool for personalized research in ophthalmology.

Characterization of intraocular pressure variability in conscious rats

Elevation of mean intraocular pressure (IOP) has long been recognized as a leading risk factor for glaucoma. Less is known about the possible contribution of moment-to-moment variations in IOP to disease development and progression due to limitations of tonometry, the prevailing method of IOP measurement. Tonometry provides good estimates of mean IOP but not IOP variance. The aim of this study was to quantitatively characterize IOP variability via round-the-clock IOP telemetry in conscious unrestrained rats. The anterior chamber of one eye was implanted with a microcannula connected to a wireless backpack telemetry system, and IOP data were collected every 4 s for one week. The cannula was then repositioned under the conjunctiva, and control data were collected for an additional week. IOP statistics were computed in 30-min intervals over a 24-h period and averaged across days. All animals exhibited a diurnal variation in mean IOP, while deviations about the mean were independent of time of day. Correlation analysis of the deviations revealed transient and sustained components, which were respectively extracted from IOP records using an event detection algorithm. The amplitude and interval distributions of transient and sustained events were characterized, and their energy content was estimated based on outflow tissue resistance of rat eyes. Transient IOP events occurred ∼231 times per day and were typically ≤5 mmHg in amplitude and 2-8 min in duration, while sustained IOP events occurred ∼16 times per day and were typically ≤5 mmHg in amplitude and 20-60 min in duration. Both persisted but were greatly reduced in control recordings, implying minor contamination of IOP data by motion-induced telemetry noise. Sustained events were also often synchronous across implanted animals, indicating that they were driven by autonomic startle and stress responses or other physiological processes activated by sensory signals in the animal housing environment. Not surprisingly, the total daily fluidic energy applied to resistive outflow pathways was determined primarily by basal IOP level. Nevertheless, transient and sustained fluctuations collectively contributed 6% and diurnal fluctuations contributed 9% to daily IOP energy. It is therefore important to consider the cumulative impact of biomechanical stress that IOP fluctuations apply over time to ocular tissues.

[Influence of corneal curvature and peripheral thickness on tonometry readings]

PURPOSE

This study investigates the influence of peripheral corneal thickness (PCT) and its curvature on tonometry readings.

MATERIAL AND METHODS

The study included 49 patients (49 eyes) who were indicated for glaucoma surgery. Using bidirectional applanation tonometry, the following parameters were obtained: IOPcc, IOPg - intraocular pressure (IOP) corrected for corneal compensation, taken as the most reliable indicator; IOP converted to Goldmann measurement, taken as the result of applanation tonometry, ΔIOP (IOPcc-IOPg), CH and CRF (corneal hysteresis and corneal resistance factor). During corneal topography, the corneal thickness was studied in the center, PCT at 1.5; 2, 3, 4 and 5 mm from the center in four meridians, as well as ΔPCT (PCT 3 mm - PCT 1.5 mm), the curvature of the anterior and posterior surfaces of the cornea and the depth of the anterior chamber. Aberrometry was used to obtain refractometry data and the curvature of the anterior surface of the cornea. The influence of the studied parameters on ΔIOP was evaluated.

RESULTS

ΔIOP correlated with CRF (r= -0.652), CH (r= -0.873), central corneal thickness (r= -0.293), PCT at all distances except 5 mm (r= -0.297; -0.287; -0.302; -0.303), with the strong and weak meridians of the anterior surface of the cornea (r=0.328; r=0.315), with the strong and weak meridians of the posterior surface, as well as the average curvature of the posterior surface (r=0.307; r=0.332; r=0.328). After step-by-step selection of the above parameters for creating a linear regression model for ΔIOP calculation, CH, CRF and PCT1.5mm remained in the model. The model describes ΔIOP with high accuracy (R2=0.974).

CONCLUSION

Biomechanical parameters of the cornea are the leading factor of applanation tonometry error. Individual linear dimensions of the cornea (thickness, curvature) have a lesser effect.

Comparison of intraocular pressure measurements obtained by icare pro tonometer, non-contact tonometer and Goldmann applanation tonometer in healthy individuals

PURPOSE

The goal of this paper was to compare the intraocular pressure (IOP) measurements obtained via iCare Pro rebound (IRT), non-contact tonometry (NCT), and Goldmann applanation (GAT) tonometry in healthy subjects.

MATERIALS AND METHODS

One hundred and twenty-five healthy individuals were included in this study. The participants' IOP measurements were obtained via non-contact tonometry. After routine ophthalmic examination, central corneal thickness (CCT) was measured with a topography device. Intraocular pressure was measured via iCare Pro rebound tonometry. After waiting for 5minutes, three measurements were taken with GAT under topical anaesthesia, and their means were recorded. Interdevice agreement was evaluated with the intraclass correlation coefficient (ICC) and Bland-Altman analysis.

RESULTS

The mean IOP measurements for NCT, IRT, and GAT were 15.97±2.99, 17.47±2.86, and 16.46±2.68mmHg, respectively. The mean difference between NCT and GAT was -0.49± 1.89mmHg, the mean difference between IRT and GAT was 1.01±1.90mmHg, and the mean difference between NCT and IRT was -1.50±2.02mmHg. Agreement between devices was found to be >0.8 for each tonometry ICC. There were significant positive correlations between the measurements obtained via these three instruments and CCT.

CONCLUSION

In this study, IOP was measured slightly lower with NCT than GAT, but it was about 1mmHg higher with IRT than GAT on average. All three devices appeared to be affected by CCT, with NCT being the most affected in this regard. The three instruments can be used for routine inspection and screening. However, considering the differences in the measurements obtained by using them, it is clear that following up IOP measurements with GAT measurements is beneficial in advanced glaucoma patients.

Easyton® transpalpebral versus Perkins applanation tonometry in different populations

OBJECTIVE

 To compare intraocular pressure (IOP) measurements obtained using the new transpalpebral Easyton® tonometer and Perkins applanation tonometer (PAT) in three different clinical populations.

METHODS

The participants of this prospective study were 84 subjects divided into the groups: 22 healthy children (G1), 42 healthy adults (G2), and 20 adult patients with primary open angle glaucoma (G3). The data recorded in 84 eyes of these subjects were age, sex, gender, central corneal thickness (CCT), and axial length (AL). In all eyes, IOP was determined in the same examination room by the same experienced examiner using Easyton® and PAT in random order.

RESULTS

 Mean differences in IOP readings between Easyton® and PAT were 0.45 ± 1.97 (p = 0.295), - 0.15 ± 2.13 (p = 0.654), - 1.65 ± 3.22 (p = 0.033), and - 0.018 ± 2.50 mmHg (p = 0.500) in the groups G1, G2, G3, and whole sample (G4), respectively. Correlations between Easyton® and PAT IOP values were 0.668 (p = 0.001) for G1, 0.463 (p = 0.002) for G2, 0.680 (p < 0.001) for G3, and 0.605 (p < 0.001) for G4. Moderate to good agreement between the two tonometers was found in all groups according to intraclass correlation coefficients, which were 0.794 (p < 0.001) for G1, 0.632 (p < 0.001) for G2, 0.809 (p < 0.001) for G3, and 0.740 (p < 0.001) for G4. The lower and upper limits of agreement between the devices were - 5.1 and 4.7 mmHg, respectively, in the complete group. No correlation was noted between CCT or AL and the Easyton® IOP measurements.

CONCLUSION

IOP measurements obtained with Easyton® and PAT show an acceptable level of agreement mainly in healthy individuals, recommending it for IOP screening in children and in patients in which PAT measurement may be impared as patients with hemifacial spasms, corneal irregularities, or reduced mobility. It is not recommended for glaucoma patients follow-up.

Assessment of corneal sublayer thickness changes in glaucoma patients using optical coherence tomography and correlation of epithelial layer thinning with dry eye monitoring

BACKGROUND

In this study, we aimed to assess the central corneal epithelial thickness (CET), central corneal stromal thickness (CST), and total central corneal thickness (CCT) thinning relationships with dry eye development monitoring and underestimated measurement of intraocular pressure (IOP) in primary open-angle glaucoma (POAG) patients treated with timolol, dorzolamide, and brimonidine.

METHODS

This longitudinal cohort study included 106 patients with POAG. All patients underwent a detailed ophthalmic examination. In addition, CET, CST, and CCT were measured using anterior segment optical coherence tomography (AS-OCT). Subsequently, the cohort was divided into three groups based on the therapy administered. The Tomec group received monotherapy with benzalkonium chloride (BAK)-preserved timolol + dorzolamide fixed combination. The Alphagan group received monotherapy with purite-preserved brimonidine, and the Combigan group received monotherapy with BAK-preserved timolol + brimonidine fixed combination.

RESULTS

CET, CST, and CCT did not show a statistically significant decrease in the Alphagan group (p>0.05). However, the Tomec and Combigan groups showed significantly reduced measurements, except for stromal thickness (p<0.05). Finally, a significant positive correlation was found between changes in tear break-up time (TBUT) and CET during the follow-up period (r = 0.637, p = 0.001).

CONCLUSIONS

CET and CCT thinning were higher in the Tomec and Combigan groups than in the Alphagan group. Furthermore, although CCT reduction was significant in the Tomec and Combigan groups, its effect on IOP underestimation was approximately 1%. Furthermore, the positive correlation between CET and TBUT suggests that CET measurement with AS-OCT may also be useful in dry eye monitoring.

Impact of Small Incision Lenticule Extraction for High Myopia on Intraocular Pressure Measurements With Pneumotonometry

PURPOSE

To evaluate the medium-term impact of small incision lenticule extraction (SMILE) on air-puff tonometry (APT) and how it may be corrected.

METHODS

In this controlled prospective study, 69 eyes from 69 patients treated with SMILE for high myopia (mean: -7.22 diopters) were included. Central corneal thickness (CCT), spherical equivalent refraction (SEQ), corneal power, and intraocular pressure (IOP) (assessed by APT) were measured before and 3 months after surgery.

RESULTS

The measured IOP decreased significantly after SMILE surgery (mean: -6.43 mm Hg), indicating a significant underestimation of the true IOP by APT. There was a significant correlation between change in SEQ, CCT, and apparent IOP. Correcting the apparent IOP measurement by applying a multiple regression correction did not provide significantly better estimates compared to adding 6.4 mm Hg to the measurement.

CONCLUSIONS

This study showed that previous SMILE surgery should be considered when interpreting APT measurements, because the measurements underestimate the true IOP. Multiple regressions cannot estimate the true IOP with certainty. For screening purposes, adding 6.4 mm Hg to the apparent IOP of a patient treated for high myopia may be sufficient. [J Refract Surg. 2023;39(9):606-611.].

A Comparison Between Ultrasound Pachymetry and CASIA2 (Anterior-Segment Optical Coherence Tomography) in the Measurement of Central Corneal Thickness

Background and objective Due in part to its effect on intraocular pressure (IOP) measurements, the assessment of central corneal thickness (CCT) is recognized as an essential part of the initial glaucoma assessment. The most widely utilized clinical technique to measure CCT is ultrasound pachymetry (USP). In recent years, many dedicated anterior-segment optical coherence tomography scanners (AS-OCTs) have been developed. Previous studies have compared CCT measurements between USP and various AS-OCTs. This study aimed to assess the degree of agreement between USP and CASIA2 (Tomey Corporation, Nagoya, Japan), a second-generation swept-source AS-OCT developed in Japan. Methodology The data on CCT screening measurements of 156 eyes (88 patients) performed over a period of three months, from January to March 2020, on glaucoma patients attending the Royal Hallamshire Hospital (RHH) in Sheffield, UK were collected retrospectively and statistically analyzed. Results The average age of the 88 patients included in the study was 66 years (range: 20-86 years). Our findings show that when compared to CASIA2 measurements, USP measurement of the CCT resulted in significantly thicker values (paired t-test: t=23.15,p<2.2 x 10^-16). The average difference between the two methods was 19.98 ± 10.78 μm. It is hypothesized that this difference may be due in part to inaccurate probe placement during ultrasound probe measurement, resulting in thicker CCT values. Conclusion The observed difference may be clinically significant as it could induce clinical discrepancy in terms of perceived glaucoma risk in patients. Therefore, USP and CASIA2 should not be used interchangeably, and clinicians should take into account the significant difference between these methods.

Effects of topical prostaglandin therapy on corneal layers thickness in primary open-angle glaucoma patients using anterior segment optical coherence tomography

PURPOSE

To evaluate the effects of latanoprost, bimatoprost, and travoprost eye drops and their preservatives on each corneal layer thickness in patients with primary open-angle glaucoma (POAG).

METHODS

We retrospectively analyzed 79 eyes of 79 patients with POAG who were receiving prostaglandin therapy. Patients were divided into three subgroups according to monotherapy with latanoprost, bimatoprost, and travoprost during a mean of 43.14 ± 19.12 months follow-up period. In addition, the central corneal epithelial thickness (CET), central corneal stromal thickness (CST), and total central corneal thickness (CCT) were measured by anterior segment optical coherence tomography (AS-OCT) at baseline and every six months after treatment initiation at each visit between 9 and 12 o'clock in the morning. Furthermore, intraocular pressure (IOP) was measured with Goldmann applanation tonometry (GAT) after AS-OCT measurements at each visit.

RESULTS

All three groups were not significantly different in age, gender, follow-up period, and mean intraocular pressure values (p > 0.05 for all). The reduction of CCT in the latanoprost, bimatoprost, and travoprost groups was 6.53 ± 3.17, 18.59 ± 8.42, and 10.1 ± 1.13 µm, respectively. The decrease in CST values was 4.65 ± 1.54, 15.84 ± 7.47, 9.69 ± 1.45 µm, and CET values were 1.88 ± 1.66, 2.75 ± 0.73, 0.41 ± 0.54 µm in all groups, respectively. A statistically significant thinning was observed in all corneal layers (p < 0.05) except the CST values in the latanoprost group and CET values in the travoprost group. However, no significant difference was found in the average reduction of CET, CST, and CCT values among the three groups (p > 0.05).

CONCLUSION

Topical treatment with latanoprost, bimatoprost, and travoprost affects each layer of the cornea separately according to the active and protective substances contained in these eye drops. On the other hand, the thinning effect on the corneal layers was similar in these three drugs because there was no significant difference between the three groups in the total amount of thinning of the corneal layers during the follow-up period.

Development and validation of an intuitive biomechanics-based method for intraocular pressure measurement: a modal analysis approach

BACKGROUND

Current intraocular pressure (IOP) measurements based on non-contact tonometry are derived from statistics-driven equations and lack biomechanical significance, which often leads to under-estimation in post-refractive surgery cornea. This study aims to introduce and validate modal analysis-derived intraocular pressure (mIOP) as a novel method generated through Legendre-based modal decomposition of the anterior corneal contour; it provides an accurate and intuitive IOP measurement from an energy-based perspective.

METHODS

This retrospective study included 680 patients. Healthy participants were divided into reference (n = 385) and validation (n = 142) datasets, and the others underwent either femtosecond-assisted laser in situ keratomileusis (FS-LASIK, n = 58) or transepithelial photorefractive keratectomy (TPRK, n = 55). Corneal curvature of the right eyes was extracted from raw serial cross-sectional images of the cornea generated by Corvis ST, a noncontact tonometer with a high-speed Scheimpflug-camera. Legendre expansion was then applied to the corneal curvature to obtain the modal profiles (i.e., temporal changes of the coefficient for each basis polynomial [modes]). Using the reference dataset, feature selection on the modal profiles generated a final mIOP model consisting of a single parameter: total area under curve (frames 1-140) divided by the area under curve of the rising phase (frames 24-40) in the fourth mode, i.e. the M₄ ratio. Validation was performed in both the healthy validation and postoperative datasets. IOP-Corvis, pachymetry-corrected IOP, biomechanically corrected IOP, and mIOP values were compared. For the FS-LASIK and TPRK groups, pairwise postoperative IOP changes were analyzed through repeated measures analysis of variance, and agreement was examined through Bland-Altman analysis. Using a finite element analysis based three-dimensional model of the human cornea, we further compared the M₄ ratio with the true intraocular pressure within the physiological range.

RESULTS

The M₄ ratio-based mIOP demonstrated weak to negligible association with age, radius of corneal curvature, and central corneal thickness (CCT) in all validation analyses, and performed comparably with biomechanically corrected IOP (bIOP) in the refractive surgery groups. Both remained nearly constant postoperatively and were not influenced by CCT changes. Additionally, M₄ ratio accurately represented true intraocular pressure in the in silico model.

CONCLUSIONS

mIOP is a reliable IOP measurement in healthy and postrefractive surgery populations. This energy-based, ratio-derived approach effectively filters out pathological, rotational, misaligned movements and serves as an interpatient self-calibration index. Modal analysis of corneal deformation dynamics provides novel insights into regional corneal responses against pressure loading.

Corneal Biomechanical Properties of Various Types of Glaucoma and Their Impact on Measurement of Intraocular Pressure

INTRODUCTION

Corneal biomechanical properties could affect intraocular pressure (IOP) measurement. The aim of this study was to evaluate the differences in corneal biomechanical properties of various types of glaucoma, assess their effect on IOP measurements.

METHODS

This is an observational clinical study of 486 subjects including 102 normal subjects, 104 ocular hypertension (OHT), 89 normal tension glaucoma (NTG), and 191 high tension glaucoma (HTG). Corneal biomechanical parameters were measured using an ocular response analyzer. The main parameters assessed were corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated pressure measurement (IOPg), and corneal-compensated intraocular pressure (IOPcc). Ultrasound pachymetry was used to measure central corneal thickness (CCT). IOP was measured by a Goldmann applanation tonometer (GAT) and a noncontact tonometer (NCT). Visual field (VF) and refractive status were also recorded. Results were analyzed by one-way analysis of variance, univariate and multivariate linear regression analyses, and Bland-Altman plots.

RESULTS

Multiple comparison by analysis of variance showed significantly lower CH and CRF in NTG compared to HTG, OHT, and normal subjects (CH: 0.011, 0.015, and 0.033; CRF: 0.001, <0.001, and 0.042, respectively). CRF and CH associated with IOP were measured using either GAT, NCT and IOPcc-GAT, IOPcc-NCT, yet CCT was not. GAT correlated strongly with IOPg (r = 0.79; p < 0.001) and IOPcc (r = 0.77; p < 0.001), but limits of agreement between the measurements were poor. CH and CRF were both negatively correlated with VF change (p < 0.01).

CONCLUSION

CH and CRF affect the measurement of IOP and were related to types of glaucoma or severity of glaucoma. Pure CCT should not be used to correct IOP values or estimate the risk of disease.

Central corneal thickness and its associations in a Russian population. The Ural eye and Medical Study

BACKGROUND

To assess central corneal thickness (CCT) and its associations in a Russian population.

METHODS

The population-based Ural Eye and Medical Study included 5899 (80.5%) out of 7328 eligible individuals. As part of an ophthalmological and general examination, CCT was measured by Scheimflug imaging.

RESULTS

The study included 5792 (98.2%) participants (age:58.8 ± 10.6 years;range: 40-94 years) with available bilateral CCT measurements. Mean CCT was larger in Russians than non-Russians (549.5 ± 32.8 µm versus 539.2 ± 33.9 µm; P < 0.001). In multivariable analysis, thicker CCT was associated (regression coefficient r:0.43) with younger age (standardized regression coefficient beta:-0.09; non-standardized regression coefficient B:-0.29;95% confidence interval (CI):-0.39,-0.20; P < 0.001), male sex (beta:0.05; B:3.10; 95%CI:1.18,5.03; P = 0.002), urban region of habitation (beta:0.10; B:6.83; 95%CI:4.61, 9.05; P < 0.001), Russian ethnicity (beta:0.04; B:3.48; 95%CI:1.04, 5.91; P = 0.005), higher level of education (beta:0.04; B:0.97;95%CI:0.29,1.66; P = 0.006), higher serum bilirubin concentration (beta:0.05;B:0.15; 95%CI:0.07,0.23;P < 0.001), lower corneal refractive power (beta:-0.09;B:11.92; 95%CI:-2.50,-1.35; P < 0.001), smaller anterior chamber angle (beta:-0.07;B:-0.38;95%CI:-0.52,-0.24;P < 0.001), higher IOP readings (beta:0.38; B:3.47; 95%CI:3.21,3.73; P < 0.001), and higher rise in IOP readings by medical mydriasis (beta:0.07; B:0.88;95%CI:0.54,1.22;P < 0.001). In that model, CCT was not associated with body height (P = 0.14), previous cataract surgery (P = 0.10), axial length (P = 0.18) or prevalence of glaucoma (P = 0.11). The mean inter-eye difference in CCT was 8.52 ± 13.9 µm (median:6.0;95CI:8.16,8.88). A higher inter-eye CCT difference was associated with older age (beta:0.08; B:0.11;95%CI:0.07,0.15; P = 0.01), lower level of education (beta:-0.04;B:-0.34; 95%CI:-0.60,-0.08; P < 0.001) and status after cataract surgery (beta:0.04; B:2.92;95%CI:1.02,4.83; P = 0.003).

INTRODUCTION CONCLUSIONS

In this ethnically mixed population from Russia with an age of 40+ years, mean CCT (541.7 ± 33.7 µm) was associated with parameters such as younger age, male sex, Russian ethnicity, and higher educational level. These associations may be taken into account when the dependence of IOP readings on CCT are considered. Glaucoma prevalence was unrelated to CCT.

Eye Dynamics and Engineering Network Consortium: Baseline Characteristics of a Randomized Trial in Healthy Adults

PURPOSE

To improve understanding of intraocular pressure (IOP) and its variance, this project identifies systemic and ocular characteristics of healthy eyes of adult volunteers including IOP variation, ocular biometrics, and aqueous humor dynamics (AHDs). These data serve as baseline controls for further studies from the Eye Dynamics and Engineering Network (EDEN) Consortium.

DESIGN

Multicenter open-label clinical trial in healthy adults randomized to 1 week treatment with 2 approved glaucoma drugs in a crossover design.

PARTICIPANTS

Among 135 healthy participants, 122 participants (aged 55.2 ± 8.8 years; 92 females, 30 males) completed the protocol.

METHODS

Participants from the University of Michigan, Mayo Clinic, and University of Nebraska Medical Center underwent measurements of ocular biometrics, AHD, and IOP using 4 tonometers. Intraocular pressure data during 3 study visits without glaucoma medications were used in the analysis. The PhenX Toolkit survey acquired standardized data on medical history, surgical history, medications, smoking and alcohol exposures, and physical measures.

MAIN OUTCOME MEASURES

The variability of IOP measurements within eyes was assessed as visit-to-visit IOP variation, within-visit IOP variation, and within-visit positional IOP variation. The concordance (or correlation) between eyes was also assessed.

RESULTS

Average positional change of > 4.7 mmHg was detected with a range of 0.5-11.0 mmHg. Pearson correlation of IOP between eyes within a visit was 0.87 (95% confidence interval [CI], 0.82-0.91) for Goldmann applanation tonometry, 0.91 (95% CI, 0.88-0.94) for Icare rebound tonometry, and 0.91 (95% CI, 0.88-0.94) for pneumatonometry. There was a 4% to 12% asymmetric fluctuation of 3 mmHg or more between eyes between visits using rebound tonometry, 9% with Goldmann applanation tonometry, and 3% to 4% by pneumotonometry. The coefficient of variation between visits for the same eye ranged from 11.2% to 12.9% for pneumatonometry, from 13.6% to 17.4% for rebound tonometry, and 15.8% to 16.2% for Goldmann applanation tonometry.

CONCLUSIONS

The current study from the EDEN Consortium describes measurement methods and data analyses with emphasis on IOP variability. Future papers will focus on changes in ocular biometrics and AHD with timolol or latanoprost treatment.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Visual field progression in open-angle glaucoma after refractive corneal ablation surgery

This study aimed to investigate visual field (VF) progression in open-angle glaucoma (OAG) subjects who had a history of refractive corneal ablation surgery (RCAS). Retrospective study. The medical records of 21 subjects who had a history of refractive corneal ablation surgery (RCAS group) and 36 patients who had myopia without a history of RCAS (non-RCAS group) were reviewed. VF progression was determined by the non-parametric progression analysis (NPA) method. VF progression and clinical characteristics were compared between the two groups. For the RCAS group, refractive regressions were analysed. The mean follow-up periods were 4.5 years and 5.5 years for the RCAS and non-RCAS groups, respectively. More glaucoma subjects in the RCAS group (57.1%) had likely VF progression than in the non-RCAS group (25.0%) (p = 0.01). The RCAS group had a significantly lower percentage of IOP reduction with anti-glaucoma medication than the non-RCAS group (p = 0.037). Eyes with likely VF progression had a higher incidence of refractive regression (91.7%, 11/12) than eyes without it (33.3%, 3/9). Among subjects whose eyes had refractive regression, 78.6% (11/14) had likely VF progression, and 21.4% (3/14) did not (p = 0.016). The VF progression in OAG after RCAS was faster than that of myopic OAG without RCAS. Anti-glaucoma treatment should be actively enhanced in clinical practice.

Racial Disparities Affecting Black Patients in Glaucoma Diagnosis and Management

Black patients are more affected by glaucoma and suffer from more advanced disease. Diagnostic challenges among black patients with glaucoma include lower rates of diagnostic testing and thinner average central corneal thickness, the latter of which affects intraocular pressure measurement. Treatment challenges include poor follow-up, medication adherence, and trust in providers. Black patients undergoing trabeculectomy have higher rates of failure compared to white patients. Race is not a definitive factor affecting success for tube shunts, laser trabeculoplasty, cyclophotocoagulation, and micro-invasive glaucoma surgeries, but the body of evidence is limited by low inclusion of black patients in these studies. Future steps should include increased attention toward improving trust between patients and providers, improving access to care, and increased representation of black patients in glaucoma research to better understand factors affecting racial disparities in glaucoma management and outcomes in this population disproportionately affected by the disease.

Analysis of Various Modalities for Intraocular Pressure Measurement in Relation to Keratoconus Severity in 246 Eyes of the Homburg Keratoconus Center

PURPOSE

Intraocular pressure (IOP) measurement may be difficult in keratoconus (KC) due to corneal protrusion and irregular astigmatism. This study aimed to assess which IOP measurement modality is least affected by KC severity.

METHODS

Data from 246 corneas of 246 patients with KC were retrospectively analyzed. KC stages were determined using the Topographic KC (TKC) and ABCD KC classifications derived from Pentacam (Oculus, Germany). IOP was measured using Goldmann applanation tonometry (GAT), Ocular Response Analyzer (ORA, Reichert Instruments, USA), and Corvis ST (CST, Oculus, Germany). Cronbach alpha (CA), analysis of variance with Bonferroni correction, Dunnett T3, and Pearson correlation were performed.

RESULTS

Using CA, the reliability of measurements using various modalities increased to 0.764 to 0.943 when excluding IOP Goldmann overall and in each KC stage (TKC and ABCD). Analysis of variance revealed significant differences between TKC and ABCD stages for almost all IOP modalities. The Bonferroni post hoc test showed significant differences between the measured IOP in earlier and advanced KC stages, except for the biomechanically CST-corrected IOP (bIOP). Pearson correlation analysis showed a significant correlation between IOP and thinnest corneal thickness (TCT) for all IOP modalities except bIOP.

CONCLUSIONS

CST-based bIOP seems to be best suited for IOP measurement in KC because it did not correlate with TCT in contrast to IOP measurements by ORA or GAT. The measurement results from GAT in patients with KC should be interpreted with care and always in view of corneal thickness. As a thumb rule, we suggest to add at least 2 mm Hg to the measured GAT value.

Racial Disparities Affecting Black Patients In Glaucoma Diagnosis And Management

Black patients are more affected by glaucoma and suffer from more advanced disease. Diagnostic challenges among black patients with glaucoma include lower rates of diagnostic testing and thinner average central corneal thickness, the latter of which affects intraocular pressure measurement. Treatment challenges include poor follow-up, medication adherence, and trust in providers. Black patients undergoing trabeculectomy have higher rates of failure compared to white patients. Race is not a definitive factor affecting success for tube shunts, laser trabeculoplasty, cyclophotocoagulation, and micro-invasive glaucoma surgeries, but the body of evidence is limited by low inclusion of black patients in these studies. Future steps should include increased attention toward improving trust between patients and providers, improving access to care, and increased representation of black patients in glaucoma research to better understand factors affecting racial disparities in glaucoma management and outcomes in this population disproportionately affected by the disease.

The Effect of Prostaglandin Analogs on Central Corneal Thickness of Patients with Glaucoma or Ocular Hypertension: A Systematic Review

BACKGROUND

Prostaglandin analogs (PGAs) are first-line antiglaucoma agents that appear to either decrease or increase central cornea thickness (CCT), creating controversy regarding the benefits of PGAs in treating CCT.

PURPOSE

We performed the first meta-analysis of observational studies to evaluate the effects of PGAs on CCT in patients with glaucoma or ocular hypertension (OHT).

METHODS

This systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement. A literature search was performed of the PubMed, Embase, Cochrane Library, System for Information on Grey Literature in Europe (Open Grey), and ClinicalTrials.gov databases and the references of retrieved studies. Only observational studies were included in the meta-analysis. The final CCT of patients and 95% confidence interval (CI) of each study were extracted. Study quality was assessed using the Newcastle-Ottawa Scale (NOS) and the Agency for Healthcare Research and Quality (AHRQ). A fixed-effects model was used to calculate the weighted mean difference (WMD) and 95% CI. Subgroup analyses based on several stratified factors such as public bias (Begg's test) and sensitivity analyses were performed.

RESULTS

Five cohort, 5 case-control, and three cross-sectional studies including 2,722 subjects were included. The pooled effect of all thirteen studies showed that PGAs reduced the CCT of patients with glaucoma or OHT slightly but significantly (WMD = -9.37; 95% CI [-12.18, -6.57]; p = 0.00; I2 = 45.5%). Significant effects were also observed in all three study designs: cohort (WMD = -5.17; 95% CI [-9.52, -0.82]), case-control (WMD = -15.31; 95% CI [-22.66, -7.97]), and cross-sectional (WMD = -8.65; 95% CI [-17.30, -0.01]). In addition, subgroup analysis of exposure time showed the effect of PGAs to be more obvious in the first (WMD = -5.81; 95% CI [-9.49, -2.14]) and second (WMD = -13.73; 95% CI [-20.19, -7.28]) years.

CONCLUSIONS

The pooled effects of previously reported studies suggest that PGA use can reduce the CCT of patients with glaucoma or OHT slightly but significantly, with this effect more pronounced in the first 2 years. These findings suggest that clinicians must closely monitor changes in CCT in the first 2 years of PGA use to identify cases of intraocular pressure misestimation and the efficacy of PGAs.

Comparison between dynamic contour tonometry and Goldmann applanation tonometry correcting equations

In order to investigate the reliability of correcting GAT formulas in comparison with dynamic contour tonometry (DCT), this study included 112 right eyes of 112 healthy subjects aged from 21 to 77 years, whose eyes underwent to a full ophthalmologic exam. IOP was measured in each eye with DCT and then with GAT. IOP values obtained with GAT were corrected with 10 equations and then compared with those provided by DCT. Participants mean age was 42.24 ± 14.08 years; mean IOP measured with DCT was 17.61 ± 2.87 and 15.50 ± 2.47 mmHg, measured with GAT. The mean discordance between DCT and GAT measurements was 2.11 ± 2.24 mmHg. All the correcting formulas, but Srodka one (p ˂ 0.001), tend to increase the difference between GAT and DCT. According to these results Śródka equation provides the best correction, reducing the difference between the two IOP measurement methods of - 0.03 ± 0.85 mmHg. Other equations do not provide a valid improvement of the agreement between the two methods or they provide a worsening of the agreement.

Comparison of different correction formulas and measurement methods for the accurate determination of intraocular pressure after SMILE and FS-LASIK surgery

Background

To compare the accuracy of non-contact tonometry, Pentacam, and corneal visualization Scheimpflug technology (Corvis ST) for the measurement of intraocular pressure (IOP) after small incision lenticule extraction (SMILE) or femtosecond laser-assisted in situ keratomileusis (FS-LASIK) surgery.

Methods

A total of 49 patients (98 eyes) undergoing FS-LASIK or SMILE surgery at West China Hospital, Sichuan University from January to March 2021 were enrolled in this prospective, comparative, self-controlled study. IOP values were measured with non-contact tonometer, Pentacam, and Corvis ST before surgery and 1 month after surgery. Pentacam-derived postoperative IOP values were corrected using five correction formulas (Ehlers, Shah, Dresden, Orssengo-Pye, and Kohlhaas), while Corvis ST-derived values were corrected using a single formula.

Results

In the SMILE group, no significant differences were observed between the IOP values corrected with the Shah formula before and after surgery (t = 0.17, P = 0.869), whereas postoperative IOP values corrected with the other formulas were significantly different from the corresponding preoperative measurements (P < 0.05). In the FS-LASIK group, postoperative IOP values corrected with the Ehlers, Shah, or Corvis ST formulas were significantly different from the corresponding preoperative IOP measurements (P < 0.05), but no significant differences were observed between pre- and postoperative IOP values corrected with the Dresden (t =  − 0.08, P = 0.941), Orssengo-Pye (t =  − 0.52, P = 0.604), or Kohlhaas (t = 1.22, P = 0.231) formulas.

Conclusions

Pentacam’s Shah correction formula seemed to be the most appropriate method for accurately measuring postoperative IOP in patients undergoing SMILE surgery, while the Dresden, Orssengo-Pye, and Kohlhaas correction formulas of Pentacam were identified as the most reliable methods for estimating IOP in patients after FS-LASIK surgery.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02620-7.

Effect of prostaglandin analogues on the biomechanical corneal properties in patients with open-angle glaucoma and ocular hypertension measured with dynamic scheimpflug analyzer

PURPOSE

The aim of the study is to evaluate the effect of topical prostaglandin (PG) treatment on the corneal biomechanical properties in treatment-naïve patients with either primary open-angle glaucoma (POAG) or ocular hypertension (OHT) using the Corvis ST device.

METHODS

This is an observational study. We analyzed the Corvis ST dynamic corneal response parameters of our database using the newest software available. Thirty-four eyes of 34 patients were included. They were all newly diagnosed and treatment-naïve. Patients were evaluated at baseline and after 6 months of treatment with prostaglandin analogues. Ultrasound pachymetry, Optical Coherence Tomography (OCT) and a 24-2 visual field test were performed in baseline visit. Goldman Applanation Tonometry (GAT-IOP) and Corvis ST dynamic corneal response parameters were registered at baseline and at the 6-month visit.

RESULTS

After 6 months of treatment, the IOP decrease (Δ) values obtained with the different tonometers were ΔGAT -6.5 ± 3.7, ΔIOPnct -4.4 ± 5.7 and ΔbIOP -3.8 ± 5.4. The differences between ΔGAT vs ΔIOPnct, ΔGAT vs ΔbIOP, and ΔIOPnct vs ΔbIOP, were statistically significant (p < 0.05 for all comparisons). Statistically significant lower values of the stress-strain index (SSI) (1.77 ± 0.3 at baseline vs 1.54 ± 0.27 at the 6-month visit) were found (p = 0.0002).

CONCLUSION

The SSI provided by the Corvis ST seems to decrease significantly after topical prostaglandin therapy. We believe that our results support the hypothesis that topical PG therapy does decrease the corneal stiffness and thus, that the ocular hypotensive effect of these drugs is overestimated if GAT is used for IOP measurement.

Association of Metabolic Syndrome With Glaucoma and Ocular Hypertension in a Midwest United States Population

PRCIS

For patients with glaucoma, metabolic syndrome was associated with higher intraocular pressure and greater central corneal thickness. Patients with metabolic syndrome were more likely to have ocular hypertension.

PURPOSE

The purpose of this study was to determine whether glaucomatous optic neuropathy, also known as glaucoma, and ocular hypertension are more likely to occur in patients with metabolic syndrome.

PATIENTS AND METHODS

Patients in Olmsted County, MN, were identified as having metabolic syndrome based on diagnosis codes, laboratory values, and/or medication use to meet 3 or more of the 5 standard criteria for diagnosing metabolic syndrome: systemic hypertension, hyperglycemia, hypertriglyceridemia, reduced high-density lipoprotein cholesterol, and central adiposity defined by increased body mass index. Patients with glaucoma, including primary open angle, low tension, pigment dispersion, and pseudoexfoliation, were identified using diagnostic codes. The charts of patients with glaucoma were individually reviewed to collect visual acuity, intraocular pressure, cup to disc ratio, central corneal thickness, visual field mean deviation, retinal nerve fiber layer thickness, and treatment of intraocular pressure. Patients with ocular hypertension were separately identified and similarly evaluated.

RESULTS

For patients with glaucoma, those with metabolic syndrome had higher intraocular pressure and greater central corneal thickness compared with those without metabolic syndrome. After adjustment for central corneal thickness, there was no longer a significant difference in intraocular pressure between groups. Metabolic syndrome was also associated with the diagnosis of ocular hypertension, and although central corneal thickness trended higher in patients with metabolic syndrome, it did not attain statistical significance.

CONCLUSION

In Olmsted County, though metabolic syndrome was associated with ocular hypertension and higher intraocular pressure in patients with glaucoma, the results were likely related to a thicker central corneal in this patient population.

Normal intraocular pressure in Egyptian children and meta-analysis

OBJECTIVE

To determine the normal intraocular pressure in a sample of Egyptian children 0-12 years of age, and compare it to that recorded in previous studies.

METHODS

This is a prospective cross-sectional study, including 345 eyes. All children underwent complete history taking and ophthalmic examination. Any glaucomatous patients or glaucoma suspects were excluded. Intraocular pressure was measured using Haag Streit Perkins M2 handheld applanation tonometer under topical or general anaesthesia. Three readings were recorded for each eye and the average was calculated. Central corneal thickness was measured, using handheld pachymeter (Pachmate 2), whenever possible.

RESULTS

The study included 345 eyes of 187 children (101 males and 86 females), aged 2 months to 12 years (mean: 5.69 ± 3.42 years). The recorded IOP was 5-20 mm Hg (mean: 11.5 ± 2.34 mm Hg). Central corneal thickness was 469-742 μm (mean: 564.8 ± 42.72 μm). The mean recorded intraocular pressure showed positive correlation with increased age (p = 0.026) and increased central corneal thickness (p = 0.037), with a difference of 1 mm Hg for every 100-μm change in central corneal thickness. The mean IOP was significantly lower than that recorded by most previous studies. A detailed comparative analysis is presented comparing our findings with other studies including grouped analysis, by country, ethnicity and tonometers used.

CONCLUSIONS

The mean IOP in a group of normal Egyptian children was 11.5 ± 2.34 mm Hg, with positive correlation to age and central corneal thickness. This mean intraocular pressure was lower than that previously reported in any other population.

Intraocular Pressure Measurement in Childhood Glaucoma under Standardized General Anaesthesia: The Prospective EyeBIS Study

Objective: We aimed to compare intraocular pressure (IOP) measurements using iCare® PRO rebound tonometry (iCare) and Perkins applanation tonometry (Perkins) in childhood glaucoma subjects and healthy children and the influence of anaesthesia depth, age and corneal thickness. Material: Prospective clinical, case-control study of children who underwent an ophthalmologic examination under general anaesthesia according to our protocol. Children were 45.45 ± 29.76 months old (mean ± SD (standard deviation)). Of all children, 54.05% were female. IOP was taken three times (T1−T3), according to duration and the depth of anaesthesia. The order of measurement alternated, starting with iCare. Agreement between the device measurements was evaluated using Bland−Altman analysis. Results: 53 glaucoma subjects and 22 healthy controls. Glaucoma subjects: IOP measured with iCare was at T1: 27.2 (18.1−33.8), T2: 21.6 (14.8−30.6), T3: 20.4 mmHg (14.5−27.0) and Perkins 17.5 (12.0−23.0), 15.5 (10.5−20.5), 15.0 mmHg (10.5−21.0) (median ± IQR (interquartile range)). Healthy controls: IOP with iCare: T1: 13.3 (11.1−17.0), T2: 10.6 (8.1−12.4), T3: 9.6 mmHg (7.7−11.7) and Perkins 10.3 (8.0−12.0), 7.0 (5.5−10.5), 7.0 mmHg (5.5−8.5) (median ± IQR). The median IOP was statistically significantly higher with iCare than with Perkins (p < 0.001) in both groups. The mean difference (iCare and Perkins) was 6.0 ± 6.1 mmHg for T1−T3, 7.3 at T1, 6.0 at T2, 4.9 mmHg at T3. Conclusion: The IOP was the highest in glaucoma subjects and healthy children at T1 (under sedation), independently of the measurement method. iCare always leads to higher IOP compared to Perkins in glaucoma and healthy subjects, regardless of the duration of anesthesia.

Accuracy of Intraocular Pressure Measurements of Eyes with Therapeutic Contact Lenses after Vitrectomy

Purpose: To evaluate the accuracy of intraocular pressure (IOP) measurements obtained by a rebound and non-contact tonometer in eyes with a therapeutic contact lens (CL) after vitrectomy.Methods: In 60 eyes of 60 patients who underwent vitrectomy for vitreoretinal disease, IOP was measured using a rebound tonometer (iCare ic200®; IOPRT) and non-contact computerized air puff tonometer (CT-80, IOPNCT), before and after wearing a CL (Purevision2®, +0.0 diopter). The mean IOP of three consecutive measurements were analyzed, and a comparative analysis with IOP measured by a Goldman applanation tonometer (IOPGAT) was performed.Results: The mean IOPRT without and with the CL was 12.55 ± 5.43 and 13.12 ± 5.13 mmHg, respectively, showing a statistically significant difference (p = 0.02) and strong positive correlation (r = 0.90, p < 0.001). The mean IOPNCT with and without the CL was 12.18 ± 3.24 and 12.17 ± 3.14 mmHg, showing no statistically significant difference (p = 0.17). The consistency with IOPGAT (12.57 ± 5.22 mmHg) was highest in IOPRT without the CL, followed by IOPRT with the CL, IOPNCT without the CL, and IOPNCT with the CL (intraclass correlation coefficients = 0.955, 0.945, 0.856, and 0.850, respectively). In addition, the rebound tonometer successfully measured IOP, regardless of whether the CL was worn; however, the non-contact tonometer failed to measure IOP in seven eyes without the CL and nine with the CL. No difference was observed according to intraocular tamponade type.Conclusions: A rebound tonometer can be used as an alternative IOL measuring method in eyes for which it is difficult to use a Goldman applanation tonometer due to the postoperative presence of a therapeutic CL.

Noncontact Intraocular Pressure Measurement over Bandage Contact Lens and the Effect of Pentacam and Corvis ST's IOP Correction System

Purpose

To evaluate the influence of intraocular pressure (IOP) measurement while wearing bandage contact lens (BCL) and the effect of Pentacam and Corvis ST's correction systems.

Methods

It was a prospective comparative study. Forty healthy subjects (40 eyes) were included in this study. Eyes were measured using noncontact tonometer (NCT), Corvis ST, and Pentacam before and after wearing BCL. Pentacam's five correction formulas (Ehlers formula, Shah formula, Dresden formula, Kohlhaas formula, Orssengo/Pye formula) and Corvis ST's correction formulas (Ehlers formula and biomechanical corrected formula) were used to correct the IOP values before and after BCL wearing. The IOP values were compared, and the correction effect of different systems were evaluated.

Results

The mean age of the subjects was 24.4 ± 0.60 years. The mean IOP obtained by NCT was 14.8 ± 3.2 mmHg before BCL wearing and was 15.7 ± 3.4 mmHg after BCL wearing. The mean IOP was significantly increased after BCL wearing (0.9 ± 2.9 mmHg, P=0.05). Four of the five Pentacam's correction formulas (except Kohlhaas formula) showed no significant difference in the mean corrected IOP values before and after BCL wearing (all P > 0.05). The mean IOP obtained by Corvis ST was 13.7 ± 2.8 mmHg before BCL wearing and was 15.0 ± 4.0 mmHg after BCL wearing. The mean IOP was significantly increased after BCL wearing (1.3 ± 2.4 mmHg, P < 0.05). Corvis ST's correction formula (Ehlers formula other than biomechanical corrected formula) showed no significant difference in the mean corrected IOP values before and after BCL wearing (P > 0.05).

Conclusion

The IOP measurements over BCL by NCT and Corvis ST was found to be increased. The correction systems of Pentacam (Ehlers formula, Shah formula, Dresden formula, and Orssengo/Pye formula) and Corvis ST (Ehlers formula) are useful in correcting the IOP measuring deviation induced by BCL wearing.

Comparison of Three Tonometers in Measuring Intraocular Pressure in Eyes That Underwent Myopic Laser in situ Keratomileusis and Photorefractive Keratectomy

Objective

Methods

Results

Conclusion

A stochastic approach to estimate intraocular pressure and dynamic corneal responses of the cornea

IntraOcular Pressure (IOP) is one of the most informative factors for monitoring the eye-health. This is usually measured by tonometers. However, the outputs of the tonometers depend on the physical and geometrical properties of the cornea. Therefore, the common practice is to develop a numerical model to generate some correction factors. The main challenge here is the accuracy and efficiency of a numerical model in predicting the IOP and Dynamic Corneal Response (DCR) of each patient. This study addresses this issue by developing a two-step surrogate model based on adaptive sparse Polynomial Chaos Expansion (PCE) for fast and accurate prediction of the IOP. In this regard, first, an FE model of the cornea has been developed to predict the DCR parameters. This FE model has been replaced with a PCE-based surrogate model to speed up the simulation step. The uncertainties in the geometry and material model of the cornea have been propagated through the surrogate model to estimate the distributions of the DCR parameters. In the second step, the combination of DCR parameters and the input parameters provide a proper parameter space for developing an efficient data-driven PCE model to predict the IOP. Moreover, sensitivity analysis by using PCE-based Sobol indices has been performed. The results demonstrate the accuracy and efficiency of the proposed method in predicting the IOP. Sensitivity analysis revealed that IOP measurement was influenced mostly by deflection amplitude and applanation time. The analysis indicates the importance of the interactions between the parameters.

The influence of corneal density and thickness on tonometry measurement with goldmann applanation, non-contact and iCare tonometry methods

PURPOSE

To evaluate the effect of corneal density and thickness on the accuracy of tonometry readings obtained via three most used techniques.

METHOD

Intraocular pressures of 45 patients' right eyes were measured using Goldmann Applanation, iCare, and non-contact tonometry methods. Corneal parameters were obtained using the Pentacam Camera System. Data obtained were analyzed using Paired t Test, Pearson's correlation coefficient, multiple linear regression analysis, and Bland-Altman plots.

RESULTS

The mean corneal thickness was 545.4 ± 3.93 μm. The mean corneal density of total, stromal, 0-2 mm, and 2-6 mm zones were 27.85 ± 6.23 GSU, 24.61 ± 6.05 GSU, 20.76 ± 2.96 GSU, and 20.81 ± 3.51 GSU respectively. IOP readings had a statistically significant correlation with corneal stromal thickness, as well as with total and stromal density. The stromal density, however, showed higher correlation with the three tonometry methods than did the total density (iCare:  - .482 (0.001) stromal density versus- .464 (0.001) total density, NCT: - .376 (0.011) versus - .353 (0.017), GAT: - .306 (0.041) versus - .296 (0.048)). Statistical differences were found in comparing the iCare readings with GAT (P < 0,00) and with NCT (P < 0,00), with mean differences of 1.8 mmHg ± 2.6 and 2.0 mmHg ± 2.6 respectively. GAT and NCT measurements showed no statistical difference (P > 0.05).

CONCLUSION

This study shows that both central corneal thickness and stromal density are significant influential factors of reliable IOP readings. It is necessary to consider more corneal biomechanical properties, as well as exercise a high degree of caution in any new attempts towards adjusting an IOP-correction equation.

Corneal Biomechanics for Ocular Hypertension, Primary Open-Angle Glaucoma, and Amyloidotic Glaucoma: A Comparative Study by Corvis ST

BACKGROUND

To evaluate biomechanical parameters of the cornea provided by Corvis ST in patients with ocular hypertension, primary open-angle glaucoma, and amyloidotic glaucoma and to compare with healthy controls.

METHODS

This was a cross-sectional study of patients with ocular hypertension, primary open-angle glaucoma, and amyloidotic glaucoma that underwent Corvis ST imaging. Primary outcome was the comparison of corneal biomechanical parameters between study groups after adjusting for age, gender, Goldmann intraocular pressure (GAT-IOP), and prostaglandin analogues medication. Secondary outcome was the comparison of different IOP measurements in each group.

RESULTS

One hundred and eighty-three eyes from 115 patients were included: 61 with primary open-angle glaucoma, 32 with amyloidotic glaucoma, 37 with ocular hypertension and 53 were healthy controls. Amyloidotic glaucoma group had smaller radius (p=0.025), lower deflection amplitude at highest concavity (p=0.019), and higher integrated radius (p=0.014) than controls. Ocular hypertension group had higher stiffness parameter at first applanation (p=0.043) than those with primary open-angle glaucoma, and higher stress-strain index (p=0.049) than those with amyloidotic glaucoma. Biomechanically corrected intraocular pressure was significantly lower than Goldmann intraocular pressure in group with primary open-angle glaucoma (p=0.005) and control group (p=0.013), and Goldmann intraocular pressure adjusted for pachymetry in group with primary open-angle glaucoma (p=0.01).

CONCLUSION

Eyes with amyloidotic glaucoma have more deformable corneas, while eyes with ocular hypertension have less deformable corneas. These findings may be linked to the susceptibility to glaucomatous damage and progression. There were significant differences between Goldmann applanation tonometry and biomechanically corrected intraocular ocular pressure provided by Corvis ST.

Choroidal Thickness in Advanced Glaucoma Patients

Purpose: We investigated choroidal thickness according to the classification of glaucoma and related factors in patients with advanced glaucoma.Methods: The present study included 133 eyes of 133 advanced glaucoma patients with a mean deviation of <-12 dB. Patients were classified into primary open angle glaucoma (POAG) and normal-tension glaucoma (NTG) groups. Factors related to the subfoveal and peripapillary choroidal thickness were analyzed using linear regression analysis.Results: The mean peripapillary choroid thickness was 99.20 ± 46.85 µm in the NTG group, which was significantly thinner than in the POAG group (121.85 ± 45.39 µm, p = 0.006). Additionally, in the sectoral comparison, the NTG group had thinner choroids than the POAG group in all areas (p < 0.05 for all). In the linear regression analysis, glaucoma class (p = 0.007), age (p = 0.005), and intraocular pressure (IOP) (p = 0.024) significantly affected the peripapillary choroid thickness. Moreover, age (p = 0.029) and macular thickness (p = 0.002) were significantly associated with subfoveal choroid thickness.Conclusions: In advanced glaucoma, low baseline IOP, NTG, and old age were significantly associated with a thin peripapillary choroid, suggesting an association between thin peripapillary choroid and the etiology of NTG. Further studies are needed to clarify the significance of a thin choroid in the pathogenesis of glaucoma.

Peripheral corneal thickness and associated factors - results from the population-based German Gutenberg Health Study

PURPOSE

Changes in peripheral corneal thickness are described in various corneal diseases such as corneal ectasia. However, few data exist describing the increase in corneal thickness from central to peripheral and reporting the normal distribution of corneal thickness in rings around the corneal centre. The aim of this study was to report these cornea characteristics and investigate associated factors in a population-based setting.

METHODS

The Gutenberg Health Study is a prospective, population-based study examining participants in a 5-year follow-up (age range 40-80 years) using Scheimpflug imaging. Corneal thickness was assessed in each participant at the apex, as well as in the corneal centre (thinnest corneal thickness) and in rings with 2, 4, 6, 8 and 10 mm diameter around the corneal centre, and the increase in corneal thickness towards the periphery. The relationship between corneal thickness at these locations and possible associated factors was determined using linear regression models. For this purpose, general and ocular parameters were included.

RESULTS

A total of 9729 participants were included in the present analysis (4874 women, age 59.2 ± 10.8 years). Multivariable analysis showed a correlation between the increase in corneal thickness in the circles from 0 to 10 mm (diameter) and the following parameters: age (B = -0.24 µm per year, p < 0.001); body height (B = -0.04 µm, p = 0.005); smoking (B = -0.72 µm, p < 0.001); spherical equivalent (B = -0.70 µm per dioptre, p < 0.001); white-to-white distance (B = -0.75 µm/mm, p < 0.001); mean corneal radius (B = -3.61 µm/mm, p < 0.001); intraocular pressure (B = -0.12 µm/mmHg, p < 0.001); glaucoma (B = -1.94 µm, p < 0.001); and pseudophakia (B = 0.89 µm, p < 0.001).

CONCLUSION

The results of the present study suggest that several general and ocular parameters are associated with peripheral corneal thickness. In the context of diagnosing glaucoma, a smaller increase in corneal thickness towards the periphery might be a new additional marker.

[Central corneal thickness and intraocular pressure in children with congenital glaucoma]

Purpose - to determine the values of central corneal thickness (CCT) in children depending on the level of intraocular pressure (IOP) and the stage of congenital glaucoma (CG).

MATERIAL AND METHODS

Clinical studies were carried out in the eye department of the clinic at the Tashkent Pediatric Medical Institute. The study involved 18 patients (36 eyes) aged 9 to 11 years (mean age 9.3±1.6 years) with confirmed diagnosis of CG. All patients underwent basic ophthalmologic examination prior to surgical and conservative treatment. In addition to basic methods, axial eye length and CCT were determined using an automatic non-contact tonometer/pachymeter manufactured by NIDEK (USA).

RESULTS

Analysis of the obtained data showed that in initial, moderate and advanced stages of glaucoma, the CCT values were significantly lower than the age norm values. This indicates stretching of the fibrous capsule and thinning of the cornea in glaucoma. In terminal stage CG, the CCT values practically did not differ from the age norm, but were higher than in initial, moderate and advanced stages of the disease. The noted thickening of the corneal membrane in terminal stage may be explained by edema of the corneal tissue as a result of elevated IOP.

CONCLUSION

The age norm values of CCT should be taken into account when characterizing the severity of glaucomatous process in children. Compared to the age norm, the cornea is significantly thinner in children aged 9 to 11 years with initial, moderate and advanced stages of CG, and becomes significantly thicker in terminal stage, which is associated with edema caused by elevated IOP.

Effect of Prostaglandin Analogues on Corneal Biomechanical Parameters Measured With a Dynamic Scheimpflug Analyzer

PRCIS

Treatment with topical prostaglandin analogues (PGAs) induces increased corneal compliance in glaucoma eyes measured with a dynamic Scheimpflug analyzer.

PURPOSE

The purpose of this study was to evaluate the effect of topical PGAs on the corneal biomechanical properties.

METHODS

We retrospectively studied the biomechanical parameters of 31 eyes of 19 consecutive patients with glaucoma measured using a dynamic Scheimpflug analyzer (Corvis ST) before and after initiation of treatment with topical PGAs. No patients had a history of glaucoma treatment before the study and no other antiglaucoma medication was used during the study period. Nine biomechanical parameters were evaluated before and 61.6±28.5 days (range: 21 to 105 d) after initiation of the treatment. The changes in the corneal biomechanical parameters before and after treatment were analyzed using multivariable models adjusting for intraocular pressure and central corneal thickness. The Benjamini-Hochberg method was used to correct for multiple comparison.

RESULTS

In multivariable models, PGA treatment resulted in shorter inward applanation time (P=0.016, coefficient=-0.151) and larger deflection amplitude (P=0.023, coefficient=0.055), peak distance (P=0.042, coefficient=0.131), and deformation amplitude ratio at 1 mm (P=0.018, coefficient=0.028). These associations consistently indicated increased corneal compliance (deformability) after PGA treatment.

CONCLUSION

Topical PGAs resulted in greater corneal compliance, suggesting that the changes in the corneal biomechanical properties may lead to overestimation of the intraocular pressure-lowering effects.

A prospective study on effectiveness of elevated intraocular pressure as a criterion for glaucoma referrals by optometric practitioners in Sweden

PURPOSE

To evaluate the outcome of referrals for suspected glaucoma based on elevated intraocular pressure (IOP) made by optometric practitioners in Sweden.

METHODS

This prospective study included 95 individuals referred to the Skåne University Hospital Malmö, Sweden, during 2019, by optometric practitioners, based on elevated IOP. Positive outcome was defined as a diagnosis of glaucoma, or a diagnosis of suspected glaucoma. Referral accuracy was analysed. Positive predictive values (PPV) of different hypothetical IOP and age thresholds were calculated.

RESULTS

In 34% (95% CI: 24-43%) of the referrals, no eye disease was found. Intraocular pressure (IOP) was the only referral criterion in 77% (73/95). The PPV was 35% (95% CI: 25-45%) for all referrals, 27% (95% CI: 16-38%) for IOP-only referrals and 59% (95% CI: 36-82%) for referrals including additional findings. In IOP-only referrals, no definite diagnosis of glaucoma was made in any patients <45 years of age. Applying a theoretical age limit of ≥45 years with a hypothetical IOP limit of ≥25 mmHg in patients 45-69 years and of ≥22 mmHg in patients ≥70 years increased the PPV to 42% (95% CI: 27-57%). IOP-only referrals would have been reduced by 27% without missing any glaucoma cases.

CONCLUSION

The overall predictive value of the referrals was poor. Glaucoma resources would have been used more effectively by increasing the required age for IOP-only referrals to ≥45 years in combination with different IOP thresholds for certain age groups.

Changes in anterior segment parameters and presence of dry eye disease in patients with acromegaly: A Sirius topography study combined with meibography

PURPOSE

To investigate anterior segment parameters (ASPs) and dry eye disease (DED), including the status of the meibomian glands, in patients with acromegaly.

METHODS

In this cross-sectional, comparative study, 36 acromegaly patients and 40 healthy sex- and age-matched controls were included. Participants received a comprehensive ophthalmological examination, including intraocular pressure measurements with Goldmann applanation tonometry (IOP_GAT) and central corneal thickness corrected intraocular pressure (IOP_CCT) measurements, and were evaluated for ASPs and DED. For ASPs, white-to-white (WTW), apical (ACT) and thinnest corneal thickness (TCT), corneal volume (CV), keratometry readings (K₁, K₂, and K_mean), anterior chamber depth (ACD) and volume (ACV), and iridocorneal angle (ICA) were obtained via Sirius topography. DED was assessed with Schirmer's test, tear breakup time (TBUT), and Ocular Surface Disease Index (OSDI) scores. Meibography scores (MSs) were obtained with the Sirius topography device.

RESULTS

Patients had higher mean IOP_GAT (P = .006), IOP_CCT (P = .01), ACT (P = .024), and TCT (P = .005) but narrower ICA (P = .014) than controls. Although Schirmer's test did not differ between the groups (P = .442), patients had higher OSDI (P < .001), higher MS (P = .001), and shorter TBUT (P = .002).

CONCLUSION

Patients with acromegaly have greater IOP, greater corneal thickness, but narrower ICA than healthy individuals, as well as DED with increased MSs, which suggests meibomian gland dysfunction.

Repeatability, reproducibility, and agreement of three tonometers for measuring intraocular pressure in rabbits

The aim of this study was to evaluate repeatability, reproducibility, and agreement of three commonly used tonometers in animal research (TonoLab, TonoVet, and TonoPEN AVIA) in a cohort of 24 rabbits. Additionally, the impact of sedation on IOP was investigated in 21 New Zealand White rabbits with the TonoVet tonometer. Repeatability was determined using the coefficient of variation (CoV) for two observers. For the TonoLab (6.55%) and TonoVet (6.38%) the CoV was lower than for the TonoPEN AVIA (10.88%). The reproducibility was highest for the TonoVet (0.2 ± 3.3 mmHg), followed by the TonoLab (0 ± 12.89 mmHg) and lowest for the TonoPEN AVIA (− 1.48 ± 10.3 mmHg). The TonoLab and TonoVet showed the highest agreement (r = 0.85, R² = 0.73). After sedation, a significant IOP reduction (often > 25%) was observed. Our results show that among the three tonometers tested, the TonoVet tonometer is best for use in rabbits while the TonoLab should be avoided. The impact of sedation on IOP was substantial and should be taken into account during experimentation.

Intraocular Pressure, Age, and Central Corneal Thickness in a Healthy Chinese Children Population: The Handan Offspring Myopia Study

PURPOSE

To assess the distribution and factors related to intraocular pressure (IOP) in a Chinese children population in Northern China.

METHODS

1,238 offspring aged 6 to 18 years, residing in six villages, were recruited for this current study, the Handan Offspring Myopia Study. Participants underwent an interviewer-administered questionnaire and a complete ocular examination, including standardized measurement of IOP with Perkins applanation tonometry.

RESULTS

1,648 eyes of 828 children were included in the analysis. The mean IOP was 13.9 ± 1.6 mmHg. The mean IOP for the study population increased from 13.0 ± 1.5 mmHg for those 6 to 7 years of age to 14.2 ± 1.4 mmHg for those 15 years of age or older (P < .001). The mean central corneal thickness (CCT) was 548.7 ± 32.1 μm, and had no difference among different age groups and gender. In univariate regression analysis, age (0.12 mmHg per 1 year old), height (0.09 mmHg per 5 cm), weight (0.02 mmHg per kg), body mass index (0.07 mmHg per 1 m/kg2), systolic blood pressure (0.06 mmHg per 5 mmHg), CCT (0.06 mmHg per 5 μm), and SE (-0.11 mmHg per 1 D) were correlated with IOP. In multivariate regression analysis, higher IOP was only associated with older ages (p = .002) and thicker CCT (p = .001).

CONCLUSION

The mean IOP in healthy rural Chinese children aged 6-18 years is about 14 mmHg, which is lower than in adults in the same locality. The mean IOP is slightly increasing with age during childhood, which is opposite to the result among adults. Age and CCT are the major independent factors associated with IOP.