Comparison of central corneal thickness measurements in corneal edema using ultrasound pachymetry, Visante anterior-segment optical coherence tomography, Cirrus optical coherence tomography, and Pentacam Scheimpflug camera tomography

Corneal Edema after Cataract Surgery

This systematic review investigates the prevalence and underlying causes of corneal edema following cataract surgery employing manual phacoemulsification. A comprehensive search encompassing databases such as PubMed, Embase, ProQuest, Cochrane Library, and Scopus was conducted, focusing on variables encompassing cataract surgery and corneal edema. Two independent reviewers systematically extracted pertinent data from 103 articles, consisting of 62 theoretical studies and 41 clinical trials. These studies delved into various aspects related to corneal edema after cataract surgery, including endothelial cell loss, pachymetry measurements, visual performance, surgical techniques, supplies, medications, and assessments of endothelial and epithelial barriers. This review, encompassing an extensive analysis of 3060 records, revealed significant correlations between corneal edema and endothelial cell loss during phacoemulsification surgery. Factors such as patient age, cataract grade, and mechanical stress were identified as contributors to endothelial cell loss. Furthermore, pachymetry and optical coherence tomography emerged as valuable diagnostic tools for assessing corneal edema. In conclusion, this systematic review underscores the link between corneal edema and endothelial cell loss in manual phacoemulsification cataract surgery. It highlights the relevance of factors like patient demographics and diagnostic modalities. However, further research is essential to unravel the complexities of refractive changes and the underlying mechanisms.

Comparison of corneal measurements in normal and keratoconus eyes using Anterior Segment Optical Coherence Tomography (AS-OCT) and Pentacam HR topographer

BACKGROUND

Keratoconus (KC) is easily recognized by its unique topographic pattern, but it can be difficult to distinguish subclinical form of the disease from the normal cornea. Optovue anterior segment optical coherence tomography (AS-OCT) helps diagnose KC.

AIM OF THE WORK

To assess and the level of agreement of Keratometry-readings (K), Central Corneal Thickness (CCT) and Thinnest Corneal Thickness (TCT) measurements obtained by Optovue AS-OCT and Wavelight Oculyzer Pentacam HR in two groups: KC eyes and normal eyes.

PATIENTS AND METHODS

This is a prospective clinical observational study. The study included 110 eyes divided into two groups. The study group included 62 eyes with topographic evidence of KC. The control group included 48 eyes of normal subjects with no topographic evidence of KC. All of the participants underwent full cycloplegic refraction, spectacle best-corrected distance visual acuity, comprehensive slit-lamp biomicroscopy and fundoscopy. All participants underwent corneal topography by Pentacam HR and AS-OCT.

RESULTS

There were highly significant differences between the studied groups as regarding BCVA, intraocular pressure and CCT measurements which were found to be lower among KC group compared to the control one. There were highly significant differences between the studied groups regarding TCT measurement detected by Pentacam HR and AS-OCT which was found to be lower among the keratoconus group compared to the control one (470.9, 455.7 versus 541.9 and 518.7 respectively).

CONCLUSION

Both Scheimpflug-based imaging and AS-OCT provide comparable readings with a good agreement regarding corneal pachymetry in keratoconus group with accurate identification of KC eyes and healthy ones. However, there was a significant difference in K readings between both devices in Keratoconus and control group.

Comparison of central corneal thickness in corneal edema by ultrasound pachymetry, specular microscopy, and anterior segment optical coherence tomography

PURPOSE

The purpose of this study was to compare ultrasound pachymetry Ultrasound pachymetry (UP), specular microscopy (SM), and anterior segment optical coherence tomography (ASOCT) in the measurement of central corneal thickness (CCT) in cases of corneal edema before and after uncomplicated phacoemulsification.

METHODS

Preoperative pachymetric measurements were performed in all patients before cataract surgery. Sixty -seven patients who developed corneal edema after routine faoemulsification surgery were included in the study. CCT measurements were made the day before surgery and on the 1^st, 7^th, and 14^th days after surgery. Correlation and agreement between the devices were quantified with the intraclass correlation coefficient (ICC), limits of agreement, and Bland-Altman plots.

RESULTS

The mean age of the patients was 70.99 ± 9.56 (36-92) years. While CCT could be measured in all eyes with ASOCT after surgery, the number of eyes measured with UP and SM were 24 (11.7%) and 27 (16.1%), 55 (82.1%) and 52 (77.6%), and 46 (88.8%) and 45 (86.9%) on postoperative days 1, 7, and 14, respectively. ICC values between UP and SM, UP and ASOCT, and SM and ASOCT, respectively, were: preoperative 0.91, 0.94, and 0.92; 1^st postoperative day 0.93, 0.86, and 0.93; 7^th postoperative day 0.94, 0.85, and 0.96; and 14^th postoperative day 0.95, 0.92, and 0.96.

CONCLUSION

In all eyes with corneal edema, CCT measurements can be taken with ASOCT; however, in some cases, CCT measurements with SM and UP cannot be taken. However, there is a good correlation between measurements taken with these devices.

Comparison of central corneal thickness measurements obtained by OrbscanIIz® and ultrasound pachymetry: A concordance study in the usual clinical practice

PURPOSE

The objective of this study was to assess the concordance between the values obtained in measuring central corneal thickness using the OrbscanIIz^® and the contact ultrasonic pachymeter available in our public ophthalmology service.

METHODS

Measurements were taken from 88 eyes of 44 patients using the two instruments. The data obtained were statistically analyzed using version 22 of the IBM SPSS^® program.

RESULTS

The mean of central corneal thickness measurements obtained from OrbscanIIz^® was significantly higher than that obtained from ultrasound pachymetry. However, the mean of differences between both instruments was only 7.22 μ, which could be considered a clinically insignificant result when considering the good concordance obtained between both systems.

CONCLUSION

OrbscanIIz^® and ultrasound pachymetry can be interchangeable in the usual public clinical practice when measuring central corneal thickness. This is the first research found in the literature that uses a concordance study to compare the data resulting from central corneal thickness measurements obtained by an OrbscanIIz^® and an OcuScan^® pachymeter in our environment.

Correlation between radial peripapillary vascular density and reduced central corneal thickness in glaucoma suspect patients

Background

Optical coherence tomography (OCT) angiography (OCTA) provides a quantitative assessment of the microcirculation of the retina and choroid. It may precede the retinal nerve layer (RNFL) and optic disc head defects. Retinal nerve fiber layer defects and reduced central corneal thickness (CCT) are important parameters in the assessment of a glaucoma suspect patients. The aim of this study is to investigate any possible relationship between the reduced central corneal thickness and the radial peripapillary capillary (RPC) density defect in glaucoma suspect.

Methods

In this cross sectional study, 92 eyes were incorporated. Peripapillary OCT angiography (4.5 mm) and Anterior segment OCT for corneal pachymetry were done. C/D Ratio, thickness of nerve fiber layer, the blood flow indices and central corneal thickness also were evaluated.

Results

In eyes of glaucoma suspect patients; a significant positive correlation between CCT and total RPC density was detected (r = 0.38, P < 0.001). A strong positive correlation was also found between total RPC and peripapillary RNFL thickness (r = 0.55, P < 0.001).

Conclusion

Reduced central corneal thickness and peripapillary capillary density are two screening parameters for glaucoma suspect patients. The radial peripapillary capillary density is a valid diagnostic tool for glaucoma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02628-z.

Inter-changeability Between Anterior Segment Optical Coherence Tomography and Scheimpflug Imaging in the Evaluation of Corneal Opacity

Purpose

To compare the results of corneal evaluation, either the total corneal thickness and corneal opacity depth by both technologies AS- OCT and Scheimpflug imaging by Sirius Scheimpflug placido topography.

Methods

sixty-eight eyes of sixty- eight consecutive patients with corneal opacities were examined by both AS-OCT and Sirius Scheimpflug imaging. Corneal thickness and corneal opacity depth were measured and compared determining the interchangeability using Bland–Altman plotting.

Results

Total corneal thickness was (470.32±62.10) and (463.47±56.47) by AS. OCT and Sirius Scheimpflug imaging, respectively (P value = 0.8).

While the actual measurement of corneal opacity, corneal opacity depth was (135.39±119) and (85.45±128) by AS-OCT and Siris Scheimpflug imaging respectively with P value (0.004).

Conclusion

AS-OCT and Scheimpflug imaging Sirius may be used interchangeably for measuring both total corneal thickness, while in the determination of corneal opacity depth. the AS-OCT is superior to Scheimpflug imaging in the accuracy of determination of actual boundaries of the corneal opacity.

Refractive changes and visual quality in patients with corneal edema after cataract surgery

BACKGROUND

To assess visual quality and stabilization of refractive changes in corneal edema patients after cataract surgery, using visual acuity (VA) and contrast sensitivity measurements.

METHODS

Sixty-one eyes were analysed, twenty-three with and thirty-eight without corneal edema. Uncorrected and corrected distance VA (UDVA and CDVA) were determined with an EDTRS chart, the contrast sensitivity function (CSF) under photopic and mesopic illumination conditions with a CVS-1000e chart, clinical refraction, and corneal topography. Measurements were taken preoperatively, 1-2 days, 1 and 3-months after surgery. Clinical refraction was converted to vector notation (M, J0, J45) and SPSS v26.0 was used for data analysis.

RESULTS

An improvement of VA was observed through the postoperative period; changes between visits were significant for CDVA in both groups and for UDVA in the edema sample. Significant astigmatic changes (J0,J45) between visits were not observed, but M values showed a hyperopic tendency in the edema group and a myopic shift in the control group that did not change between visits, with statistically significant differences between groups. Controls had significantly better contrast sensitivity at high spatial frequencies. Under mesopic conditions, global contrast sensitivity losses were observed in the edema group, which improved between visits in the middle frequency range.

CONCLUSION

Corneal edema patients had a significant reduction of CDVA, and frequency-selective sensitivity losses that evidence a visual quality loss. Clinical refraction may improve visual quality, but in edema patients these losses are related to corneal changes, which did not change at three months after surgery.

Longitudinal Changes in Corneal Epithelial Thickness and Reflectivity following Simple Limbal Epithelial Transplantation: An Optical Coherence Tomography-Based Study

PURPOSE

To describe the changes in corneal epithelial thickness and reflectivity following simple limbal epithelial transplantation (SLET) using anterior segment optical coherence tomography (ASOCT).

METHODS

This was a prospective imaging study of 31 eyes of 29 patients who had undergone autologous or allogeneic SLET for limbal stem cell deficiency and had stable, avascular surfaces postoperatively. ASOCT scans of all four quadrants were taken preoperatively and at 1-week, 1-month, 3-month, 6-month, and 1-year postoperative time points in the eyes undergoing SLET. Baseline scans were also taken from the normal eye in unilateral cases. The following parameters were obtained from the scans: (i) epithelial thickness (ET), (ii) stromal thickness, (iii) total corneal thickness, (iv) epithelial reflectivity (ER), (v) stromal reflectivity, and (vi) epithelial/stromal (ES) reflectivity ratio.

RESULTS

Chemical injury (24 eyes, 77.4%) was the most common indication for surgery. There was a significant improvement in the ET (184.8 ± 117.1 vs 60.3 ± 10 µm, p < .0001) and ER (144.5 ± 26.4 vs 120.9 ± 28.9, p < .0001) within the initial postoperative period following SLET, which remained stable at the end of 1 year follow-up. There was no difference in the ET of the post-SLET and normal eyes after the 3-month timepoint and this normalization was maintained until the end of the first year. A significant normalization was also noted in the ES reflectivity ratio at the end of 1 year (2.1 ± 0.8 vs 1 ± 0.2, p < .001). A significant correlation was found between the final visual acuity and the total corneal thickness (r = 0.942, p = .005).

CONCLUSION

There is a significant improvement in the epithelial thickness and reflectivity of the cornea in eyes undergoing SLET. ASOCT provides a reliable objective measure of these changes and can be used to monitor the outcomes in these eyes postoperatively.

Corneal Edema Visualization With Optical Coherence Tomography Using Deep Learning: Proof of Concept

PURPOSE

Optical coherence tomography (OCT) is essential for the diagnosis and follow-up of corneal edema, but assessment can be challenging in minimal or localized edema. The objective was to develop and validate a novel automated tool to detect and visualize corneal edema with OCT.

METHODS

We trained a convolutional neural network to classify each pixel in the corneal OCT images as "normal" or "edema" and to generate colored heat maps of the result. The development set included 199 OCT images of normal and edematous corneas. We validated the model's performance on 607 images of normal and edematous corneas of various conditions. The main outcome measure was the edema fraction (EF), defined as the ratio between the number of pixels labeled as edema and those representing the cornea for each scan. Overall accuracy, sensitivity, specificity, and area under the receiver operating characteristic curve were determined to evaluate the model's performance.

RESULTS

Mean EF was 0.0087 ± 0.01 in the normal scans and 0.805 ± 0.26 in the edema scans (P < 0.0001). Area under the receiver operating characteristic curve for EF in the diagnosis of corneal edema in individual scans was 0.994. The optimal threshold for distinguishing normal from edematous corneas was 6.8%, with an accuracy of 98.7%, sensitivity of 96.4%, and specificity of 100%.

CONCLUSIONS

The model accurately detected corneal edema and distinguished between normal and edematous cornea OCT scans while providing colored heat maps of edema presence.

Simultaneously Monitoring Whole Corneal Injury with Corneal Optical Density and Thickness in Patients Undergoing Cataract Surgery

To pursue the least corneal implication during cataract surgery, this study aimed to monitor corneal wound injury after cataract surgery with a novel method. The prospective cohort study involved thirty-two patients, who were assessed by a Scheimpflug tomography AxL^® (Oculus GmbH, Wetzlar, Germany) via the following two kinds of indices: whole corneal optical density (COD) and corneal thickness (CT), two weeks before and one month after cataract surgery. The results of the COD revealed that corneal annuli 0.0–2.0 mm and 2.0–6.0 mm, and the average and maximal values at the incisional site significantly increased postoperatively. Also, the anterior and central stroma of 0.0–2.0 mm, and all three depths of 2.0–6.0 mm, increased remarkably after the operation. For the CT, all ranges of diameters plus incisional sites showed significant increases postoperatively. Furthermore, we analyzed the differences (delta) of COD and CT between pre- and post-operation, and found significant correlations between the delta of COD and the delta of CT, regarding annuli 0.0–2.0 mm, 2.0–6.0 mm, and 6.0–10.0 mm, but no correlation at the incisional site, with either average density or maximal density, was detected. We concluded that whole COD and CT, especially at the central zones of the cornea (annulus < 6 mm), are both valuable parameters in the assessment of corneal damage post-cataract surgery, and are independent indices at the incisional site.

Accelerated versus Standard Corneal Cross-linking for Progressive Keratoconus in Syria

Purpose

To compare the outcomes of accelerated versus standard corneal cross-linking for the treatment of progressive keratoconus.

Methods

In this retrospective comparative study, 63 eyes of 40 patients with progressive keratoconus were divided into two groups; 27 eyes in group one were treated with an accelerated protocol (10 mW/cm 2 , 9 min) and 36 eyes in group two were treated with the standard method (3 mW/cm 2 , 30 min). Visual acuity, refraction, corneal topography, corneal tomography, and anterior and posterior corneal higher-order aberrations (HOAs) were assessed preoperatively and 18-30 months postoperatively.

Results

The LogMAR uncorrected and corrected distance visual acuity values were improved in both groups postoperatively. However, the improvement was significantly higher in group one (P < 0.05, all). The flattening in the anterior keratometry readings, flat K, steep K, and average K were significantly higher in group two (P < 0.001, all). The maximum anterior keratometry (AKf) values significantly decreased in both groups, whereas the maximum posterior keratometry (AKb) values increased. The reduction in the minimum corneal thickness (ThKmin) was significantly greater (36.49um) in group two, compared to 10.85um in group one. There was a significant increase in the posterior average keratometry, and a significant decrease in the posterior astigmatism, along 3 mm meridian in S-CXL (P = 0.03, P = 0.008, respectively), while the corresponding values showed no statistical significance in group one (P > 0.05). The anterior corneal trefoil was significantly reduced in group one (P = 0.002), whereas anterior total HOAs and coma were significantly improved in group two (P < 0.0014, all). The posterior corneal spherical aberration decreased significantly in group one (P = 0.02), while group two revealed significant reduction in the posterior trefoil values (P = 0.011). The change in the anterior maximum keratometry was significantly and positively correlated to the preoperative maximum keratometry in group two (P = 0.53, P = 0.003).

Conclusion

An accelerated cross-linking protocol using 10 mW/cm 2 for 9 min showed more visual improvement and less pachymetric reduction when compared to the standard protocol, however, anterior corneal flattening, posterior corneal steepening, and the change in the posterior astigmatism were significantly higher in the standard protocol; while corneal HOAs were improved in both protocols.

Central Corneal Thickness Among Filipino Patients in an Ambulatory Eye Surgery Center Using Anterior Segment Optical Coherence Tomography

Objective

The purpose of the study was to determine the central corneal thickness (CCT) among Filipino patients that may contribute to different glaucoma diagnosis using the anterior segment optical coherence tomography in an ambulatory eye surgery center.

Methods

A single-center retrospective, cross-sectional study design including 1232 eyes of 641 patients of the Asian Eye Institute, Makati, Philippines from January 2019 to December 2019 who had their CCT measured with Visante anterior segment optical coherence tomography (AS-OCT). CCT was correlated with age, sex, presence of diabetes and/or hypertension, and glaucoma diagnosis.

Results

Among 641 patients who had their CCT measured by Visante AS-OCT, 723 eyes of 369 patients were included. Nearly half of the study population were normal or glaucoma suspects. The mean CCT among Filipino patients was 535.59 ± 34.06 µm. Ocular hypertensive patients had the thickest CCT, while normal tension glaucoma patients had the thinnest CCT. After adjusting for multiple variables, CCT had a direct relationship with the presence of diabetes, IOP level and the diagnosis of ocular hypertension, while inverse relationship with age. Most of the patients presenting with angle closure glaucoma were females aged 60 and above.

Conclusion

Visante AS-OCT is a non-contact and non-aerosol generating instrument allaying the fear of disease transmission from contact or aerosolization of tears. Our study confirms similar relationships of CCT with age, presence of diabetes, IOP level, and diagnosis of ocular hypertension or normal tension glaucoma among Filipino patients with the available literature from other ethnicities.

Dose-dependent emergence of acute and recurrent corneal lesions in sulfur mustard-exposed rabbit eyes

Sulfur mustard (SM) is a lipid soluble alkylating agent that causes genotoxic injury. The eye is highly sensitive to SM toxicity and exposures exceeding 400 mg min/m³ can elicit irreversible corneal pathophysiologies. Development of medical countermeasures for ocular SM exposure has been hindered by a limited understanding of dose-dependent effects of SM on corneal injury. Here, clinical, histological and ultrastructural analyses were used to characterize the effects of SM dose on corneal injury progression. Corneas were evaluated for up to 20 wk following exposure to saturated SM vapor for 30-150 s, which corresponds to 300-1,500 mg min/m³. In acute studies, a ceiling effect on corneal edema developed at doses associated with full-thickness corneal lesions, implicating endothelial toxicity in corneal swelling. Recurrent edematous lesions (RELs) transiently emerged after 2 wk in a dose-dependent fashion, followed by the development of secondary corneal pathophysiologies such as neovascularization, stromal scarring and endothelial abnormalities. RELs appeared in 96 % of corneas exposed for ≥ 90 s, 52 % of corneas exposed for 60 s and 0 % of corneas exposed for 30 s. While REL latency was variable in corneas exposed for 60 s, REL emergence was synchronized at exposures ≥ 90 s. Corneas did not exhibit more than one REL, suggesting RELs are part of a programmed pathophysiological response to severe alkylating lesions. In post-mortem studies at 12 wk, corneal edema was positively correlated to severity of endothelial pathologies, consistent with previous findings that endothelial toxicity influences long-term outcomes. These results provide novel insight into long-term corneal pathophysiological responses to acute toxicity and identify exposure conditions suitable for therapeutic testing.

Comparison of Anterior Ocular Biometric Measurements Using Swept-Source and Time-Domain Optical Coherence Tomography

Purpose

To compare central corneal thickness (CCT), aqueous depth (AQD), and anterior chamber depth (ACD) measurements using the swept-source (CASIA SS-1000, Tomey, Japan) and time-domain (Visante, Carl Zeiss Meditec, USA) anterior segment optical coherence tomographers (OCT) in normal eyes.

Methods

Sixty-eight eyes of 68 subjects were included. Three consecutive scans of each subject were obtained using both devices in a random order by one experienced operator. Standard deviation (S _w), coefficient of repeatability (CoR), coefficients of variation (CoV), and intraclass correlation coefficients (ICC) were used to evaluate the intraoperator repeatability. Agreement was assessed using the Bland-Altman plots and 95% limits of agreement (LoA).

Results

All measurements of the swept-source OCT (SS-OCT) and time-domain OCT (TD-OCT) showed high repeatability with low CoR (CCT: 2.34 μm and 6.16 μm; AQD: 0.05 mm and 0.09 mm; ACD: 0.06 mm and 0.09 mm), low CoV (CCT: 0.16% and 0.42%; AQD: 0.61% and 0.97%; ACD: 0.53% and 0.83%), and high ICC (>0.98). The mean CCT with SS-OCT was slightly thicker than the results with TD-OCT (difference = 4.55 ± 2.62 μm, P < 0.001). There was no statistically significant difference in AQD or ACD measurements between the two devices (0.01 ± 0.05 mm, P=0.111; 0.02 ± 0.05 mm, P=0.022, respectively). The 95% LoA between the SS-OCT and TD-OCT were -0.59 to 9.69 μm for CCT, -0.10 to 0.12 mm for AQD, and -0.09 to 0.12 mm for ACD.

Conclusions

High levels of repeatability and agreement were found between the two devices for all three parameters, suggesting interchangeability. SS-OCT demonstrated superior repeatability compared with TD-OCT.

Comparative Evaluation of Central Corneal Thickness in Cross-Linked Keratoconic Eyes

PURPOSE

To compare the central corneal thickness (CCT) measurements measured by using the Pentacam Scheimpflug system with the CCT measured using ultrasound pachymetry (UP) and to compare the compatibility between the methods in normal, keratoconic, and cross-linked keratoconic corneas.

METHODS

The study included 50 eyes of 50 patients with keratoconus (keratoconus group), 50 eyes of 50 patients with progressive keratoconus who underwent corneal cross-linking treatment (CCL group), and 50 eyes of 50 healthy subjects (control group). Patients in the keratoconus and CCL groups were further classified into mild (mean keratometry [Km] ≤ 47 D) and moderate keratoconus subgroups (47.0 < Km < 52.0 D). CCT values were noted from the Pentacam Scheimpflug and UP.

RESULTS

The difference between the Pentacam and UP values was largest in the CCL group (-20.9 0.21.5 μm), followed by the keratoconus and control groups (-10.6 0.20.3 and 0.4 0.6.8 μm). The Pentacam and UP measurements were not comparable in the keratoconus and CCL groups (P = 0.001 and P < 0.001), whereas they were comparable in the control group (P = 0.62). In subgroup analysis, the 2 methods were comparable in the mild keratoconus subgroup (P = 0.12) and not comparable in the moderate keratoconus subgroup and in both mild and moderate subgroups of the CCL group (P = 0.001, P < 0.001 and P < 0.001).

CONCLUSIONS

Pentacam Scheimpflug tomography and UP can be used interchangeably in normal and mild keratoconic eyes, but not in moderate keratoconic and cross-linked keratoconic eyes. Pachymetry measurements from Scheimpflug must be interpreted with extreme caution with different methods before planning an invasive procedure in these eyes.

Reproducibility and reliability of central corneal thickness determination in more and less profound corneal edema using ultrasound pachymetry, a Scheimpflug camera and anterior segment OCT

PURPOSE

The purpose of this study is to determine the influence of different degrees of corneal edema on the reliability and reproducibility of central corneal thickness(CCT) measurements by a Scheimpflug camera (Pentacam), anterior segment optical coherence tomography(AS-OCT) and ultrasound pachymetry(USP).

METHODS

Forty-four patients undergoing ophthalmic surgery were included in this prospective study. All measurements were acquired by two investigators. The Pentacam and AS-OCT measurements were performed in randomized order followed by USP. Two measurements were taken by each investigator with each device. CCT was evaluated by using the apex value provided by the Pentacam, the corneal apex cut in the AS-OCT and averaging 2 cycles of 4 measurements for USP. Coefficients of variation (COV) and intraclass correlation coefficients (ICC) were determined. To investigate the reproducibility in different degrees of corneal edema, patients were subdivided into edema more/less than 10% of CCT, ≥/< 600 μm and > 650 μm CCT.

RESULTS

No significant differences were recorded for each individual investigator and measuring device. However, overall the devices differed significantly in the < 600 μm group (ANOVA p < 0.04). The reproducibility decreased with higher degrees of corneal edema in particular for investigator 1 and USP measurements. No significant overestimation of corneal thickness by the Pentacam was recorded in higher degrees of corneal edema.

CONCLUSION

USP measurements are highly user dependent especially in higher degrees of corneal edema. Nevertheless, all methods were able to reach a high level of agreement in CCT measurement in higher degrees of corneal edema. Interestingly lower degrees of corneal edema revealed the only significant differences in-between the 3 devices.

Scheimpflug Camera and Swept-Source Optical Coherence Tomography in Pachymetry Evaluation of Diabetic Patients

Aim

The comparative analysis of the central and peripheral corneal thicknesses using two different imaging systems: Scheimpflug camera and swept-source OCT was performed to investigate the differences in corneal thickness analysis in diabetic patients.

Materials and Methods

The study group consisted of the 147 eyes of 107 diabetic patients who were examined and compared with 138 eyes of 89 nondiabetic cataract patients. The inclusion criteria for the study group was diabetes mellitus type II identified no less than 10 years ago, with NPDR not requiring prior laser treatment. The control group was recruited from nondiabetic patients. Measurements were obtained on the Pentacam Scheimpflug imaging system and Casia swept-source OCT. All study parameters from anterior chamber images were processed for five different zones, the central zone and four peripherals—superior, inferior, nasal, and temporal. A fit zone diameter of 4 mm was applied for both instruments.

Results

The Pentacam system overestimated corneal measurements in the DM group when compared with the Casia OCT in superior corneal zone (p=0.04), inferior corneal zone (p=0.02), nasal corneal zone (p < 0.001), and temporal corneal zone (p=0.01). In the control group, there were also statistically significant differences between the Pentacam and Casia OCT measured values in inferior corneal zone (p=0.001), nasal corneal zone (p=0.04), and temporal corneal zone (p < 0.001).

Conclusion

Scheimpflug camera pachymetry measurements showed statistically higher CCT values when compared with swept-source OCT measurements.