The effect of contact lens induced corneal edema on Goldmann applanation tonometry measurements

Advances and Challenges in Wearable Glaucoma Diagnostics and Therapeutics

Glaucoma is a leading cause of irreversible blindness, and early detection and treatment are crucial for preventing vision loss. This review aims to provide an overview of current diagnostic and treatment standards, recent medical and technological advances, and current challenges and future outlook for wearable glaucoma diagnostics and therapeutics. Conventional diagnostic techniques, including the rebound tonometer and Goldmann Applanation Tonometer, provide reliable intraocular pressure (IOP) measurement data at single-interval visits. The Sensimed Triggerfish and other emerging contact lenses provide continuous IOP tracking, which can improve diagnostic IOP monitoring for glaucoma. Conventional therapeutic techniques include eye drops and laser therapies, while emerging drug-eluting contact lenses can solve patient noncompliance with eye medications. Theranostic platforms combine diagnostic and therapeutic capabilities into a single device. Advantages of these platforms include real-time monitoring and personalized medication dosing. While there are many challenges to the development of wearable glaucoma diagnostics and therapeutics, wearable technologies hold great potential for enhancing glaucoma management by providing continuous monitoring, improving medication adherence, and reducing the disease burden on patients and healthcare systems. Further research and development of these technologies will be essential to optimizing patient outcomes.

Comparison of the iCare, Tono-Pen, non-contact airpuff, and Goldmann applanation tonometers in eyes with corneal edema after penetrating keratoplasty

BACKGROUND

To compare the utility of the iCare, Tono-Pen, and non-contact airpuff (NCT) tonometers with the Goldmann applanation tonometer (GAT) for measuring intraocular pressure (IOP) in patients with corneal edema after penetrating keratoplasty (PKP) and to assess the effects of central corneal thickness (CCT) and corneal curvature (CC) on IOP measurements.

METHODS

Thirty-two eyes of 27 patients with corneal edema after PKP due to corneal abnormalities and 43 control eyes of 30 patients with normal corneas were recruited. Before IOP measurements, all patients underwent a baseline examination, including auto-refraction, keratometry, slit lamp biomicroscopy, and CCT measurement. IOP was measured using the devices in the same order: first the NCT, followed by the iCare, Tono-Pen, and GAT. The differences between the iCare, Tono-Pen, NCT, and GAT were calculated with repeated-measures analysis of variance. The Bland-Altman method was used to assess the agreement between the iCare, Tono-Pen, and NCT versus the GAT. The influences of CCT and CC on IOP measurement were evaluated by correlation analysis using Pearson's correlation coefficient.

RESULTS

Mean IOP measurements were significantly higher with the NCT and Tono-Pen than with the GAT in the PKP and control groups. When compared with GAT, iCare showed significantly higher IOP readings in the control group, but the IOP readings did not differ between the iCare and GAT in the PKP group. Poor agreement was noted between the NCT and GAT in both groups. The Tono-Pen showed clinically acceptable agreement with GAT in control eyes and poor agreement in PKP eyes. The agreement between the iCare and GAT appeared to be clinically acceptable in both groups. Correlation analysis of the results from control eyes showed that the IOP measurements with the GAT and NCT were weakly related to CCT and moderately correlated with CC. The iCare IOP readings were weakly correlated with CCT and CC.

CONCLUSION

In the PKP group, the NCT and Tono-Pen significantly overestimated IOP, whereas the iCare IOP readings were similar to those obtained using the GAT. Poor agreement was noted between the NCT and GAT as well as between the Tono-Pen and GAT, but the iCare showed clinically acceptable agreement with GAT. In normal corneas, the GAT, NCT, and iCare were affected by CCT and CC. The iCare tonometer was less affected by corneal edema than were the NCT and the Tono-Pen. The iCare appears to be a useful device for IOP measurement in eyes with corneal edema after PKP.

Variations of Intraocular Pressure Measured by Goldmann Applanation Tonometer, Tono-Pen, iCare Rebound Tonometer, and Pascal Dynamic Contour Tonometer in Patients With Corneal Edema After Phacoemulsification

PRCIS

Edematous corneas had lower Goldmann applanation tonometer (GAT) intraocular pressure (IOP) compared with other tonometers. A significant, mild negative correlation between central corneal thickness (CCT) and GAT IOP was found in a group of significant edematous corneas with CCT increases of >100 µm.

PURPOSE

To compare the IOP that was randomly obtained with the GAT, Tono-Pen, iCare, and Pascal dynamic contour tonometer in patients with corneal edema after phacoemulsification.

MATERIALS AND METHODS

Corneal edema was quantified by CCT measurement. The agreement between IOP measurements assessed by different instruments was evaluated using Bland-Altman plots. The relationship between CCT and IOP was investigated using the coefficient of correlation. The CCT and IOP were compared between the periods of postsurgical edema and after its resolution.

RESULTS

The mean age of 60 patients was 75.9±7.8 years. CCT increased significantly after surgery, by an average of 96.1±39.9 µm (P<0.001). Relative to the IOPs measured with the GAT in edematous eyes: the mean difference in Tono-Pen IOPs was 4.7 mm Hg; 95% limits of agreement (LOA), -0.3 to 9.6 mm Hg. For iCare, was 2.3 mm Hg; 95% LOA, -2.2 to 6.8 mm Hg. For Pascal dynamic contour tonometer, was 3.0 mm Hg; 95% LOA, -0.4 to 6.5 mm Hg. Edematous corneas had significantly lower GAT IOP than Tono-Pen IOP; 12.3±3.2 versus 16.9±3.1 (P=0.02). Pearson correlation coefficients (r) showed a high correlation between the 4 tonometers in eyes without edema. There was a significant, mild negative correlation between CCT and GAT IOP (r=-0.25, P=0.02) in a group of significant edematous corneas with CCT increases of >100 µm: GAT IOP decreased by 3.1 mm Hg for every 10-µm increase in CCT.

CONCLUSIONS

IOP readings with GAT tended to be lower than those obtained with the other tonometers, especially the Tono-Pen. GAT IOP readings in cases of severe corneal edema should be interpreted with caution.

Goldmann Applanation Tonometry versus Dynamic Contour Tonometry after Vitrectomy with Silicone Oil Endotamponade

PURPOSE

To evaluate the agreement of intraocular pressure (IOP) measurements using dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) in eyes after vitrectomy with silicone oil endotamponade and controls.

METHODS

In this prospective comparative study, IOP was measured with GAT and DCT in 30 eyes with oil endotamponade 1-3 days after vitrectomy and 40 untreated controls. In addition, ocular pulse amplitude (OPA), corneal pachymetry (CCT), and axial length (AL) were measured.

RESULTS

GAT values in the oil group were significantly higher compared to control eyes (mean GAT oil 13.6 ± 5.1 mmHg; mean GAT control 10.8 ± 2.1 mmHg; p = 0.003). There was no significant difference in DCT measurements (mean DCT oil 12.0 ± 4.1 mmHg; mean DCT control 11.9 ± 2.9 mmHg; p = 0.9). This led to a significant difference of GAT-DCT between the oil and control group (mean difference of GAT-DCT oil 1.6 ± 4.7 mmHg; mean difference of GAT-DCT control -1.1 ± 2.6 mmHg; p = 0.004). The difference between GAT and DCT was negatively correlated with the mean IOP measured by both methods (r = -0.36, p = 0.02) and positively correlated with CCT only in the control group (r = 0.36, p = 0.02), as well as to AL only in the oil group (r = 0.46, p = 0.01). The OPA did not differ significantly between groups.

CONCLUSION

GAT and DCT showed a good agreement in control eyes. The difference of GAT and DCT is significantly changed in eyes after vitrectomy with silicone oil endotamponade. Our findings suggest that GAT overestimates IOP in this situation.

A retrospective analysis of intraocular pressure changes after cataract surgery with the use of prednisolone acetate 1% versus difluprednate 0.05%

Purpose

To compare the effect of topical prednisolone acetate 1% (PA) used after routine cataract surgery to the effect of difluprednate 0.05% (DFBA) used for the same indication on intraocular pressure (IOP).

Methods

An electronic query was created to gather information from all cataract surgeries between January 2010 and January 2015 within the electronic health record database at Barnet Dulaney Perkins, a multicenter, multiphysician private practice in Phoenix, Arizona. Information collected included age, sex, diabetes status, glaucoma history, medication regimen (use of PA or DFBA), and IOP before surgery, 5–10 days postoperatively (TP1) and 3–6 weeks postoperatively (TP2). Postoperative IOP measurements were compared to baseline IOP measurement in each patient.

Results

Regardless of steroid used, all patients in this study experienced an increase in IOP within TP1 and returned to baseline IOP (±2.0 mmHg) by TP2. Patients who received DFBA showed a statistically significant increase in IOP at TP1 compared to those on PA (P<0.001) with the mean IOP an average 0.60 mmHg higher (95% CI =0.3, 0.9). The odds ratio of a clinically significantly increased IOP at TP1 (defined as overall IOP ≥21 mmHg and an increase of ≥10 mmHg) in DFBA-treated patients was 1.84 (95% CI =1.4, 2.6). In patients treated with PA, 3% reached a significantly increased IOP, compared to 4.4% of patients in the DFBA group (P<0.05). Risk factors for increased IOP were identified, and include advanced age (>75) (P<0.005) and a history of glaucoma (P<0.001).

Conclusion

In postoperative cataract patients, use of DFBA increased the risk of a clinically significant IOP increase.

Visual, Keratometric and Corneal Biomechanical Changes after Intacs SK Implantation for Moderate to Severe Keratoconus

Purpose:

To report visual outcomes and corneal biomechanical changes after femtosecond-assisted Intacs SK implantation in keratoconic eyes.

Methods:

This prospective interventional case series is comprised of 32 keratoconic eyes of 25 patients with mean age of 23.8 ± 5.4 years. Uncorrected (UDVA) and corrected (CDVA) distance visual acuity, refraction, manifest refraction spherical equivalent (MRSE), keratometry, central corneal thickness (CCT), corneal hysteresis (CH) and corneal resistance factor (CRF) were measured preoperatively, and 1, 3 and 6 months postoperatively.

Results:

Mean UDVA improved from 0.81 ± 0.3 LogMAR preoperatively to 0.53 ± 0.2 LogMAR six months postoperatively (P < 0.001). At 6 months, MRSE was significantly reduced only in eyes with moderate KCN (mean change, +2.61 ± 0.54 diopter [D]; P< 0.001). A significant improvement in sphere (mean change, +1.92 ± 0.37 D; P< 0.001) and mean keratometry (mean change, -3.34 ± 0.47D; P< 0.001) were observed. CCT increased from 446.1 ± 38 μm preoperatively to 462.2 ± 50 μm at six months (P < .001). CRF decreased from 6.5 ± 1.6 mmHg to 5.9 ± 1.1 mmHg six months after surgery (P = 0.02). CDVA, refractive cylinder and CH did not change significantly (P = 0.48, 0.203 and 0.55, respectively). Linear regression analysis disclosed that a decrease in CCT and moderate KCN are associated with higher CRF (standardized B,-0.513 and 0.314;P= 0.004 and 0.024, respectively; Adjusted R square = 0.353).

Conclusion:

Visual, refractive and keratometric indices remarkably improved in a parallel fashion. CRF was inversely associated with CCT. Changes in CRF represent the trend of changes in corneal biomechanics and thickness during the early postoperative months.

Intraocular pressure and corneal biomechanics in Fuchs' endothelial dystrophy and after posterior lamellar keratoplasty

PURPOSE

  To evaluate the precision of techniques for measuring intraocular pressure (IOP) in corneas with presumably altered biomechanical properties.

METHODS

  Intraocular pressure was measured with a Goldmann applanation tonometer (GAT), ocular response analyzer (ORA) and dynamic contour tonometer (DCT) in 70 eyes. Thirty-five eyes were normal corneas, 18 eyes had Fuchs' endothelial dystrophy, and 17 eyes had undergone Descemet's stripping automated endothelial keratoplasty (DSAEK) surgery. Corneal hysteresis (CH), corneal resistance factor (CRF) as well as central corneal thickness (CCT) were recorded with the ORA.

RESULTS

  The measured cornea-corrected IOP using ORA was significantly higher than GAT in all three groups (p< 0.001). The DCT differed significantly from the Goldmann only in the Fuchs' group (p= 0.04). The Goldmann and DCT showed no significant between-group differences, whereas IOP measured with the ORA was different between groups (p< 0.001). CH in the DSEAK group differed significantly from the controls (p< 0.001), but there was no significant difference between the DSEAK and Fuchs' groups (p= 0.21). CCT did not differ significantly between the DSAEK and Fuchs' group (p= 0.47). However, both these groups differed significantly from the controls (p< 0.001).

CONCLUSION

  Corneal hysteresis and CRF are reduced in Fuchs' endothelial dystrophy as well as after posterior lamellar keratoplasty. GAT and DCT seem to measure IOP correctly in patients with Fuchs' endothelial dystrophy as well as after posterior lamellar keratoplasty. Corneal-corrected IOP as measured with the ORA appears to overestimate IOP in patients with Fuchs' endothelial dystrophy as well as after posterior lamellar keratoplasty.

Correction factors for Goldmann Tonometry

PURPOSE

The purpose of the study was to evaluate the in vitro accuracy of correction factors in decreasing the error in the intraocular pressure (IOP) measurements obtained using the Goldmann Applanation Tonometer (GAT).

METHODS

Nineteen donor corneas, from individuals aged between 57 and 99 years (mean 75.7 years, standard deviation±11.4 years) were subjected to posterior pressure simulating in vivo true IOP (IOPT) using an inflation test rig. Central corneal thickness and corneal curvature were measured. The posterior pressure was set at 25 different pressure levels between 5 and 45 mm Hg and IOP was measured using the GAT. Five different correction equations were applied to the IOP measurements obtained using the GAT to determine corrected IOP. The multiparameter correction equations applied were derived by Elsheikh, Ehlers, Chihara, Shimmyo et al, and Orssengo and Pye. The differences between IOPT and the IOP measured using the GAT were recorded as uncorrected errors, whereas the differences between IOPT and each of the corrected IOP were the tonometry errors after correction.

RESULTS

The mean and standard deviation of error in tonometry before correction was +2.25±0.62 mm Hg. The mean errors in tonometry after correction using the Elsheikh and Chihara equations were +0.78±0.62 and +1.08±0.61 mm Hg, respectively. The mean errors in tonometry for the Ehlers, Shimmyo et al, and Orssengo and Pye equations were negative, indicating an overcorrection; the values were -0.75±2.28, -1.27±1.85, and -0.77±1.83 mm Hg, respectively.

CONCLUSIONS

The Elsheikh and the Chihara et al's equations considerably decreased error in IOP measurements obtained by the GAT when compared with IOPT and were more consistent than other correction equations. The 2 equations may be of clinical utility in obtaining estimates of IOPT.

Susanna R. Intraocular pressure profile during the modified diurnal tension curve using Goldman applanation tonometry and dynamic contour tonometry

The aim of this study was to compare the intraocular pressure (IOP) profile during the modified diurnal tension curve (mDTC) using Goldman applanation tonometry (GAT) and dynamic contour tonometry (DCT) in treated glaucomatous eyes. Eligible subjects were submitted to the mDTC using GAT and DCT in this sequence. IOP measurements were performed at 8 a.m., 10 a.m., 2 p.m., and 4 p.m.. Central corneal thickness was measured using ultrasound pachymetry in the morning. Statistical analysis was performed using paired Student’s t test and Bland–Altman plot. The mean difference between DCT and GAT measurements was 0.9 mmHg. The mean ± SD IOP measurements during the mDTC were 19.68 ± 4.68, 17.63 ± 4.44, 17.25 ± 5.41, and 17.32 ± 4.25 mmHg using GAT and 19.97 ± 4.75, 18.79 ± 4.61, 19.53 ± 5.30, and 19.43 ± 5.45 mmHg using DCT. IOP measurements were higher in the morning (8 a.m.) and decreased throughout the day using both tonometers. The difference between IOP measurements using GAT and DCT was smaller in the morning and increased throughout the day. The IOP variability using GAT was higher than using DCT. Corneal biomechanical properties might help explain our findings.

Effects of aging on corneal biomechanical properties and their impact on 24-hour measurement of intraocular pressure

PURPOSE

To study the effects of aging on corneal biomechanical properties and their impact on 24-hour measurement of intraocular pressure (IOP).

DESIGN

Experimental study.

METHODS

Fifteen older volunteers with healthy eyes (age range, 50 to 80 years) were housed for one day in a sleep laboratory with a 16-hour diurnal or wake period and an eight-hour nocturnal or sleep period. Every two hours, sitting corneal hysteresis, corneal resistance factor, and IOP were measured. Central corneal thickness (CCT) was measured using an ultrasound pachymeter. Data were compared with previous observations in 15 healthy younger volunteers (age range, 20 to 25 years).

RESULTS

Variations in 24-hour corneal hysteresis and corneal resistance factor were not significant in the older subjects, but there were time-dependent variations in CCT and IOP. The nocturnal CCT was thicker than the diurnal CCT, but the IOP difference between the diurnal and nocturnal periods was not significant. Cosine-fits of CCT and IOP showed synchronized 24-hour rhythms. The phase timing of CCT rhythm appeared significantly earlier than the phase timing of IOP rhythm. Compared with younger subjects, older subjects had a lower mean 24-hour corneal hysteresis and corneal resistance factor, but not a lower CCT. Phase timings of 24-hour rhythms of CCT and IOP were significantly delayed by aging.

CONCLUSIONS

Aging may lower corneal hysteresis and corneal resistance factor, but neither parameter shows a significant 24-hour variation. Aging may not change CCT significantly, but can shift its 24-hour rhythm. The 24-hour IOP pattern in this group of older subjects is not an artifact resulting from a variation in corneal hysteresis, corneal resistance factor, or CCT.

The effect of contact lens induced oedema on the accuracy of Goldmann tonometry in a mature population

AIM

To determine the effect of contact lens induced oedema on the accuracy of Goldmann tonometry measurements of intraocular pressure (IOP) in mature subjects.

METHODS

22 healthy subjects aged between 50 and 60 years were recruited. Corneal curvature, IOP, and central corneal thickness (CCT) were measured before and after two hours of monocular closed eye wear of a thick hydroxyethyl methacrylate (HEMA) contact lens. Measurements were then repeated at 20 minute intervals for one hour after lens removal.

RESULTS

Both CCT (+54.1 mum) and IOP (+2.7 mm Hg) increased significantly after lens wear (p<0.001, paired t test with Bonferroni correction). For the hour following lens removal, the measured IOP was correlated to the increase in CCT (r = 0.84, p<0.001), at a rate of 1.0 mm Hg/10 mum (95% confidence interval, 0.8 to 1.2 mm Hg/10 mum, linear mixed model analysis).

CONCLUSIONS

A relatively small increase in CCT from contact lens induced corneal oedema caused an overestimation error in Goldmann tonometry measurements of IOP in healthy mature subjects.