Longitudinal changes in central corneal thickness and their relation to glaucoma status: an 8 year follow up study

Corneal thickness and endothelial change after use of ocular hypotensive agents

Corneal transplantation can restore visual function when visual impairment is caused by a corneal disease. However, this treatment is associated with the scarcity of cornea donors. The suitability of corneal donation from patients with glaucoma using ocular hypotensive agents (OHAs) is controversial. This study aimed to elucidate changes in corneal thickness, corneal endothelial cell density, and corneal endothelial cell hexagonality after OHA use in patients with primary open-angle glaucoma. We retrospectively reviewed the data of 53 glaucoma suspect eyes without OHA use and 106 primary open-angle glaucoma eyes under OHA use. All participants underwent corneal parameter assessment using SP-3000P (Topcon Corp., Tokyo, Japan) at the time of diagnosis and the final visit. The OHA dose and timing of use were recorded. The ocular hypotensive agents score (OHAS) was determined based on the number, formula, frequency, and duration of OHA use. Baseline data showed no significant differences between the two groups with and without OHA use. At the final visit, the OHA-treated group showed significantly lower corneal thickness and corneal endothelial cell density than those of the control group. A weak positive correlation between the OHAS and changes in corneal endothelial cell hexagonality was noted. However, no correlation was observed between the OHAS and changes in corneal thickness or endothelial cell density. In conclusion, patients with glaucoma and using OHAs should undergo the corneal structural properties examinations before donation to ensure the quality of donor cornea.

Central corneal thickness and its determinants in a geriatric population: a population-based study

PURPOSE

To determine the distribution of central corneal thickness (CCT) and its determinants in an Iranian geriatric population.

METHODS

This population-based study was conducted in 2019 in Tehran, the capital of Iran, using stratified multistage random cluster sampling. The study population was all residents ≥60 years of age. First, preliminary optometric and ocular health examinations were performed including the measurement of uncorrected and best-corrected visual acuity, objective and subjective refraction, anterior and posterior segment examination. The study participants then underwent corneal imaging using Pentacam HR.

RESULTS

Out of 3791 invitees, 3310 participated in this study (response rate: 87.3%). The mean CCT and apex corneal thicknesses were 528 µ (95% CI: 526-529) and 529 µ (95% CI: 527-530), respectively. The highest and lowest mean corneal thickness was related to the superior (620 µ: 95% CI: 618-622) and the temporal (591 µ: 95% CI: 590-592) paracentral points, respectively. According to the multiple linear regression model, the CCT was significantly inversely related to keratometry readings (K1 and K2) and had a statistically significant direct relationship with intraocular pressure (IOP), corneal eccentricity (ECC), and corneal volume (CV) (all p values <0.05). The CCT was significantly higher in diabetic patients (p = 0.043).

CONCLUSION

The CCT values in the geriatric Iranian population were lower than the values reported in most previous studies. The CCT is mostly influenced by IOP and corneal parameters (curvature, shape factor, and volume) and is not affected by demographic factors, refractive error, and ocular biometric components.

Clinical Ocular Biomechanics: Where Are We after 20 Years of Progress?

Purpose: Ocular biomechanics is an assessment of the response of the structures of the eye to forces that may lead to disease development and progression, or influence the response to surgical intervention. The goals of this review are (1) to introduce basic biomechanical principles and terminology, (2) to provide perspective on the progress made in the clinical study and assessment of ocular biomechanics, and (3) to highlight critical studies conducted in keratoconus, laser refractive surgery, and glaucoma in order to aid interpretation of biomechanical parameters in the laboratory and in the clinic.Methods: A literature review was first conducted of basic biomechanical studies related to ocular tissue. The subsequent review of ocular biomechanical studies was limited to those focusing on keratoconus, laser refractive surgery, or glaucoma using the only two commercially available devices that allow rapid assessment of biomechanical response in the clinic.Results: Foundational studies on ocular biomechanics used a combination of computer modeling and destructive forces on ex-vivo tissues. The knowledge gained from these studies could not be directly translated to clinical research and practice until the introduction of non-contact tonometers that quantified the deformation response of the cornea to an air puff, which represents a non-destructive, clinically appropriate load. The corneal response includes a contribution from the sclera which may limit corneal deformation. Two commercial devices are available, the Ocular Response Analyzer which produces viscoelastic parameters with a customized load for each eye, and the Corvis ST which produces elastic parameters with a consistent load for every eye. Neither device produces the classic biomechanical properties reported in basic studies, but rather biomechanical deformation response parameters which require careful interpretation.Conclusions: Research using clinical tools has enriched our understanding of how ocular disease alters ocular biomechanics, as well as how ocular biomechanics may influence the pathophysiology of ocular disease and response to surgical intervention.

Discordance between Anterior Segment Anatomy and Axial Length in Cataract Surgery Candidates in France

INTRODUCTION

The aims of this study were to study ocular biometric data and their association with age and sex in a population of cataract surgery candidates and to assess the proportion of inhomogeneous eyes and the ratio anterior segment (AS) to axial length (AL). Multicentric cross-sectional analysis was conducted between April 2008 and May 2021 in public and private ophthalmic institutions in Montpellier, France. Individuals ≥40 years old who underwent ocular biometry before cataract surgery were included.

METHODS

Right phakic eyes were included. Ocular biometrics were measured by using the Lenstar LS900 device. We defined AS as anterior chamber depth (ACD) plus lens thickness (LT) and calculated the ratio of AS to AL. We defined inhomogeneous eyes as those with deep AS (≥4th quartile) and short AL (≤1st quartile) (AS+) or with short AS and high AL (AL+).

RESULTS

We included 11,650 individuals (11,650 eyes) (mean [SD] age 71.64 [10.50] years; 54.51% women). Older age was associated with shorter AL (p < 0.01), shallower ACD (p < 0.01), thinner central corneal thickness (p < 0.01), and larger LT (p < 0.001). Women had shorter AL, shallower ACD, and thinner central corneal thickness than men (p < 0.001). In total, 778 (6.68%) eyes were inhomogeneous (3.22% AS+ and 3.46% AL+), for a mean (SD) AS/AL ratio of 0.36 (0.01) and 0.28 (0.01), respectively, as compared with 0.32 (0.02) for homogeneous eyes (p < 0.001).

CONCLUSION

The AS/AL ratio could be useful to screen inhomogeneous eyes before cataract surgery and justify the use of new generation formulas in these eyes to avoid the risk of refractive error.

Rate of central corneal thickness changes in primary angle closure eyes: long-term follow-up results

Background

Central corneal thickness (CCT) and its association with intraocular pressure, which is a pivotal parameter in glaucoma management, has previously been reported. In this study, we intended to investigate the long-term change of CCT in terms of rate in eyes with primary angle-closure (PAC). Additionally, we aimed to analyze events that could affect CCT.

Methods

In this retrospective study, 26 patients with PAC who had a follow-up period of more than 5 years were analyzed. The rate of CCT changes from baseline was evaluated from the serial CCT measurements over the average follow-up period. The pattern of CCT change rate according to modes of treatment and history of angle-closure attack was analyzed using the repeated linear mixed model analysis.

Results

A total of 52 eyes were enrolled. The CCT reduction rate of the entire study population was − 0.72 ± 0.22 μm/yr (P = 0.001) with statistical significance. The CCT thinning rate of the laser peripheral iridotomy (PI) group was − 0.53 ± 0.25 μm/yr (P = 0.034) and that of the surgical trabeculectomy group was − 1.32 ± 0.43 μm/yr (P = 0.002), and it was not statistically significant (P = 0.112). The rate of CCT thinning in patients with a history of acute angle-closure attack was − 0.81 ± 0.31 μm/yr (P = 0.009) and that in patients without an attack was − 0.63 ± 0.30 μm/yr (P = 0.001), and it was not statistically significant (P = 0.680). Baseline CCT appeared to be the only significant factor affecting the rate of CCT changes (P < 0.001).

Conclusions

We found a significant reduction in CCT over a long observation period in PAC eyes. We also found that the rates of CCT reduction were not affected by different treatment modalities or acute angle-closure attacks. The analysis of long-term CCT changes in conjunction with baseline CCT would also be helpful in the clinical evaluation of the PAC patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-021-01908-4.

Corneal thickness evaluation in healthy eyes: Comparison between two different Scheimpflug devices

Purpose

To evaluate the correlation between corneal thickness (CT) measurements obtained with two Scheimpflug devices, Pentacam HR and Precisio, and to elaborate, if necessary, a regression formula which could make these results comparable.

Design

Retrospective, Comparative, Observational study.

Setting

Department of Medicine, Surgery and Dentistry, “Scuola Medica Salernitana” University of Salerno, Italy

Methods

One hundred twenty four healthy eyes of 124 volunteers (65 males; range: 20–32 years; mean age of 24.8 ± 1.7) were included in this study. CT was measured using Pentacam HR and Precisio in three different points: the pupil center (PC), the corneal apex (CA) and the thinnest point (TP).

Results

CT obtained with both devices at the PC, at the CA and at the TP showed a good correlation (r = 0.97, r = 0.97, r = 0.97, respectively), but Pentacam HR measurements were significantly thicker than those provided by Precisio (p < 0.01). The differences between Pentacam HR and Precisio were 21.9 ± 8.8 μm at the PC, 21.9 ± 8.9 μm at the CA, 19.1 ± 9.0 μm at the TP. The calculated regression formulas were: y = 0.9558x + 2.3196 for the PC, y = 0.9519x + 4.5626 for the CA, y = 0.9364x + 15.436 for the TP, where x is the CT measured with Pentacam HR and y is the Precisio measurement.

Conclusions

The findings provided by this study highlight that Precisio measures thinner corneas compared to Pentacam HR. The identified regression formulas could be utilized to make interchangeable the results obtained with these two devices.

Effects of aging on corneal parameters measured with Pentacam in healthy subjects

Our purpose was to prospectively analyze the age-related changes of corneal Scheimpflug parameters in healthy subjects. Thirty-five eyes of 35 volunteers (age 14-67 years) were investigated with an average interval of 3.6 years. Changes of corneal parameters (flattest keratometric reading at anterior (K1F) and posterior surface (K1B), steepest keratometric reading at anterior (K2F) and posterior surface, anterior astigmatism, posterior astigmatism (AstigB), flat axis of anterior and posterior astigmatism (AxisB), thinnest pachymetric value (PachyMin), corneal volume (CV10-mm)) were analyzed. K1F and K2F decreased significantly during observation and showed stronger decrease in younger than in older individuals. Higher values proved to be more stable. K1B decreased significantly and the degree of decrease was dependent on its baseline value and age: in young subjects low values increased, high values decreased. AstigB decreased significantly and showed a baseline-dependent significant increase from lower and a significant decrease from higher initial values. Over time, the mean AxisB shifted significantly. PachyMin and CV decreased significantly with age, especially from higher baseline values in younger subjects. The results of this longitudinal study suggest that both corneal surfaces change significantly with age. We demonstrate for the first time that age and baseline values influence age-related changes of corneal parameters.

Longitudinal Change in Central Corneal Thickness in the Tema Eye Survey

PURPOSE

To determine the change and rate of change in central corneal thickness (CCT) and their determinants.

DESIGN

Longitudinal observational population-based study.

METHODS

A total of 758 normal and 58 glaucomatous subjects underwent complete eye examination, with CCT measurements at 2 separate visits. Change and rate of change in CCT were determined. Univariate and multivariate linear regression analyses were performed to determine the factors associated with change and rate of change.

RESULTS

The mean follow-up duration was 8.4 ± 0.7 years. The overall change was -8.9 ± 16.7 μm in OD and -9.8 ± 16.2 μm in OS, both P < .0001. Changes in glaucomatous and normal subjects were -14.1 ± 2.2 μm vs -8.6 ± 0.6 μm in OD (P = .02) and -14.5 ± 2.2 μm vs -9.5 ± 0.6 μm in OS (P = .03), respectively. The overall rate of thinning was -1.1 μm/year (OD) and -1.2 μm/year (OS). Rates in glaucomatous and normal eyes were -1.7 ± 0.3 μm/year vs -1.0 ± 0.1 μm/year in OD (P = .02) and -1.7 ± 0.3 μm/year vs -1.1 ± 0.1 μm/year in OS (P = .03), respectively. Change and rate of change were associated with baseline CCT (ß = -0.1 to -0.09 and -0.011, respectively, all P < .001) and glaucoma (ß = -6.8 to -5.6, P ≤ .009, and -0.75 to -0.69, P ≤ .007, respectively).

CONCLUSION

CCT decreased significantly over time. The change and rate of change were greater in glaucomatous than normal eyes, and were greater than described in cross-sectional studies.

Correlation between central corneal thickness and myopia

PURPOSE

To analyze the correlation between central corneal thickness (CCT) and myopia in refractive surgery candidates.

MATERIALS AND METHODS

Patients that underwent myopic laser refractive surgery between January 2000 and December 2014 were included. Preoperative CCT was measured by ultrasonic pachymetry, and refractive status determined by manifest and cycloplegic refraction.

RESULTS

A total of 30,245 individuals were included. Mean age was 28.2 ± 8.6 years, and 45.9% were female. Mean refractive error was 4.02 ± 2.17 D (range 0.25-19.5), and the mean CCT measurement was 533.5 ± 35.5 µm (range 404-794). Younger individuals showed higher degree of myopia (p = 0.006). No difference in CCT was found between women and men (533.0 ± 35.1 and 533.6 ± 35.9 µm, respectively, p = 0.19). Though CCT showed no correlation with age (p = 0.226) participants above age 40 expressed higher CCT values (p < 0.001). No significant correlation was found between the CCT and cylinder (p > 0.05). An increase in mean keratometry was associated with a decrease in CCT (p < 0.001). There was a direct correlation between the degree of myopia and CCT (r = 0.94, p < 0.001). The result remained the same after adjusting for age group and gender in stepwise backward regression analysis (p < 0.001).

CONCLUSION

Central corneal thickness is correlated with the degree of myopia among adults undergoing refractive surgery.

Central Corneal Thickness and its Associations With Ocular and Systemic Factors in an Urban West African Population

PURPOSE

To assess the associations of central corneal thickness (CCT) with ocular and systemic factors in a West African population.

DESIGN

Population-based cross-sectional study.

METHODS

Participants aged ≥40 years in the Tema Eye Survey who had clinically normal corneas were included in this study. CCT was determined bilaterally using handheld ultrasound pachymetry. The association between CCT and ocular or systemic factors was analyzed with univariable linear regression. Multivariable linear regression analysis was performed for variables significantly associated with CCT in the univariable analysis. Main outcome measures were CCT (μm) and its associations with age, sex, IOP, cup-to-disc ratio (CDR), glaucoma, hypertension, and diabetes.

RESULTS

A total of 6806 eligible subjects were identified, of whom 5603 (82.3%) participated in the Tema Eye Survey. A total of 4737 participants (84.5% of participants) of West African descent and clinically normal corneas were included. The mean age ± standard deviation (SD) of participants was 51.2 ± 9.7 years and 38.7% were male. The mean ± SD CCT in the population was 533.9 ± 34.0 μm. In the multivariable linear regression analysis, increased CCT was significantly associated with younger age, male sex, and higher IOP (all P < .001). There were no significant associations between CCT and CDR, glaucoma, hypertension, and diabetes.

CONCLUSIONS

This population-based cross-sectional survey of West African adults found a significant association between increased CCT and younger age, male sex, and higher IOP but not glaucoma or CDR. Variations in corneal thickness may influence the accuracy of IOP measurements in African persons.

Longitudinal Evaluation of Central Corneal Thickness in Patients With Systemic Sclerosis

PURPOSE

To investigate the longitudinal change of central corneal thickness (CCT) in patients with systemic sclerosis (SSc) and to elucidate whether it contributes to misinterpretation of intraocular pressure (IOP) in this group of patients.

METHODS

Twenty patients with SSc and 20 sex- and age-matched controls were examined at 2 visits 5 years apart. Age, sex, race, subtype of SSc, disease duration, autoantibody profile, use of disease-modifying antirheumatic drugs (DMARDs), best-corrected visual acuity, spherical equivalent refraction, IOP, and CCT were recorded. IOP was assessed by applanation tonometry and CCT by ultrasonic pachymetry.

RESULTS

CCT decreased by 7.2 μm [95% confidence interval (CI), -2.1 to -12.2 μm] between the first and second measurements (P = 0.008) in patients with SSc and by 2.4 μm (P = 0.39, 95% CI, -8.0 to 3.3 μm) in the control group. Considering patients with SSc, CCT decreased by a mean of 11.6 μm [95% CI, -4.3 to -19.0 μm (P = 0.007)] among those taking DMARDs at the second visit and by 4.2 μm [95% CI, -3.0 to -11.5 μm (P = 0.2)] in patients not taking any DMARDs. There was no statistically significant change in IOP between the 2 visits for either the SSc group (P = 0.84) or the control group (P = 0.29). Mean change in CCT was not associated with either IOP at first visit or with change in IOP in SSc patients.

CONCLUSIONS

CCT decreased with time in SSc. However, the slight rates of thinning observed are unlikely to considerably influence applanation tonometry or clinical decision-making over the short to intermediate term.

Long-term change in central corneal thickness from a glaucoma perspective

AIM

To investigate the longitudinal change in central corneal thickness (CCT) over 3 years in patients with glaucoma.

MATERIALS AND METHODS

The Chennai Glaucoma Follow-up Study, an offshoot of the Chennai Glaucoma Study, was designed to evaluate the progression of glaucoma. A cohort of participants in the Chennai Glaucoma Study that were suffering from glaucoma or were at a higher risk for glaucoma underwent comprehensive ophthalmic evaluation at the base hospital at 6-month intervals during the years 2004 to 2007. The CCT (average of 10 readings) was measured between 11 am and 1 pm on any given day using an ultrasonic pachymeter. Patients with a history of ocular surgery, corneal disease and usage of topical carbonic anhydrase inhibitor were excluded. No patient was a contact lens wearer.

RESULTS

One hundred and ninety-six patients (84 male, 112 female) met the inclusion criteria. We analyzed data from the right eye. The mean age of the patients was 59.97 ± 9.06 years. Fifty-nine (30.1%) of the patients were diabetic. The mean change in CCT (CCT at first patient visit--CCT at last patient visit) was 3.46 ± 7.63 μm. The mean change in CCT was 0.75 μm per year (R² = 0.00). Age, gender, intraocular pressure at the first patient visit and diabetic status had no significant influence on the magnitude of change in CCT.

CONCLUSION

A carefully obtained CCT reading by a trained examiner need not be repeated for at least 3 years as long as the ocular and systemic factors known to affect the measurement of CCT are constant.

Orbscan topography in primary open-angle glaucoma

PURPOSE

To compare anterior and posterior corneal curvatures between eyes with primary open-angle glaucoma (POAG) and healthy eyes.

METHODS

This is a prospective, cross-sectional, observer-masked study. A total of 138 white subjects (one eye per patient) were consecutively recruited; 69 eyes had POAG (study group), and the other 69 comprised a group of healthy control eyes matched for age and central corneal pachymetry with the study ones. Exclusion criteria included any corneal or ocular inflammatory disease, previous ocular surgery, or treatment with carbonic anhydrase inhibitors. The same masked observer performed Goldmann applanation tonometry, ultrasound pachymetry, and Orbscan II topography in all cases. Central corneal thickness, intraocular pressure, and anterior and posterior topographic elevation maps were analyzed and compared between both groups.

RESULTS

Patients with POAG had greater forward shifting of the posterior corneal surface than that in healthy control eyes (p < 0.01). Significant differences in anterior corneal elevation between controls and POAG eyes were also found (p < 0.01).

CONCLUSIONS

Primary open-angle glaucoma eyes have a higher elevation of the posterior corneal surface than that in central corneal thickness-matched nonglaucomatous eyes.

Effect of acute increases of intraocular pressure on corneal pachymetry in eyes treated with travoprost: an animal study

PURPOSE

To evaluate "in vivo" the effect of topical travoprost on the central corneal thickness (CCT) of rabbit eyes, and the changes in the CCT after acute increases of intraocular pressure (IOP) in these eyes.

MATERIALS AND METHODS

This is an interventional, prospective, case-control, masked study. Topical travoprost was applied once daily for one month to the right eye of six New Zealand male rabbits, the left eye of each animal served as control. The baseline CCT and IOP were measured under general anesthesia. After the IOP was stabilized at 15 and 30 mmHg, as registered by direct cannulation of the anterior chamber, CCT measurements were measured again at both pressure levels.

RESULTS

The baseline CCT was thicker in eyes previously treated with travoprost (study group) than in control eyes (p < 0.01). The CCT decreased in both groups when IOP was raised to 15 and 30 mmHg, and there were no statistically significant difference in absolute CCT values between study and control eyes at any of the IOP levels (p = 0.5). However, the amount of CCT decrease from baseline values was greater in eyes previously treated with travoprost (study group) than in control ones, at both 15 and 30 mmHg IOP levels (p = 0.01 and 0.02, respectively).

CONCLUSIONS

Rabbit corneas treated with topical travoprost show a different strain response to acute increases in IOP than control eyes.

Methodologic quality of studies on prognostic factors for primary open-angle glaucoma progression measured by visual field deterioration

Glaucoma is a chronic, slowly progressing, and asymptomatic optic neuropathic disorder with a great variety of causes that involve gradual retinal ganglion cell axon loss. The disease is the second most common cause of blindness in the industrialized world. Once vision loss develops it is irreversible-although in many cases further loss can be slowed if adequate treatment is provided. If not treated, glaucoma can lead to complete vision loss in the affected eye. Primary open-angle glaucoma (POAG) is the most prevalent form of the disease in the industrialized countries, representing 94% of all glaucomas. In a Spanish study of 569 individuals, the prevalence of POAG was 2.1% (99% confidence interval 1.9%-2.3%) in the age range between 40 and 79 years. Assessing glaucomatous damage progression remains one of the most important and challenging aspects in glaucoma management. In addition, a better understanding of clinical risk factors for glaucoma worsening may help us to develop new strategies to improve glaucoma care. Over the past 2 decades, many studies have addressed the issue of risk factors associated with or predicting for glaucoma progression. Although many studies have attempted to identify the prognostic factors capable of predicting the course of POAG, the results have been varied and in some cases contradictory, and are thus of scant practical utility. This study was designed to evaluate the methodologic quality of the studies published in the literature on the prognostic factors for POAG progression measured by visual field deterioration.

Corneal hysteresis measured with the Ocular Response Analyzer in normal and glaucomatous eyes

PURPOSE

To identify differences in corneal hysteresis (CH) and central corneal thickness (CCT) between healthy and glaucomatous patients.

METHODS

Retrospective observational study. One hundred and thirty-three eyes of 75 healthy and 58 glaucomatous patients were included. CH was measured in each patient using Ocular Response Analyzer. CCT was determined by ultrasonic pachymetry. For each patient, one eye was randomly selected. We used a Student t-test to search for significant differences between the different groups (p<0.05).

RESULTS

In healthy and glaucomatous eyes, mean CH values were 10.46 +/- 1.6 and 8.77 +/- 1.4 mm Hg, respectively. Mean CCT values were 560.2 +/- 36.3 and 535.3 +/- 42.7 microm, respectively. CH and CCT were significantly lower in glaucomatous eyes than in normal eyes, (p<0.05).

DISCUSSION

In our series, CH was lower in glaucomatous than in normal eyes. The relationship between glaucoma, IOP, and ocular structures may not be confined to the consideration of CCT. A low CH value could be responsible for under-estimation of IOP. CH could also be a risk factor for glaucoma, independent of IOP. Further studies are needed to support these hypotheses.

CONCLUSION

In our investigation, CCT and CH were significantly lower in glaucomatous eyes than in healthy eyes.

Relation between central corneal thickness and intraocular pressure in Punjabi population

OBJECTIVE

The motive of this study was to determine the variation of central corneal thickness (CCT) in the Punjabi population and to examine its relationship with intraocular pressure (IOP) using a non-contact tonometer. The study and results emphasize the effects of age, sex and refraction on this relationship, which is important for the diagnosis and prevention of glaucoma in adequate time.

METHODS

The study design was a cross-sectional, population-based survey. The participants were 279 females and 253 males of Punjab Province, India, in the age group of 21-70 years. The CCT was measured using an ultrasonic pachymeter, and the IOP was measured using an air-puff tonometer in all subjects.

RESULTS

The mean values of CCT and IOP were observed to vary imprecisely with age. The measurement of both parameters was also affected by sex and refraction. The linear regression analysis suggests that the mean value of CCT grows progressively with increasing value of mean IOP. A significant positive correlation was identified between CCT and IOP in the age group of 21-70 years. The authors inferred that this correlation value varies prominently with age for both sexes, which needs to be investigated further.

CONCLUSIONS

The authors suggest that CCT is a noteworthy source of variation in IOP measurements for males as well as females belonging to different age groups, when assessing IOP as a risk for glaucoma in the Punjabi population.

Goldmann tonometry and pachymetry measures in patients with and without topical medical treatment at a glaucoma clinic

PURPOSE

To investigate, by audit, the intraocular pressure (IOP) and central corneal thickness (CCT) of patients attending a routine glaucoma clinic, in order to assess the potential effect of CCT on IOP measures.

METHODS

Data on current IOP (Goldmann), CCT (ultrasound) and glaucoma medications use were collected from 140 patients who presented for a follow-up visit over a 3-month period. Baseline IOP was retrieved from patient records.

RESULTS

The IOP was lower at follow-up, an expected effect of the use of IOP-lowering medications. However, the CCT was lower in medicated patients indicating, but not proving, that it changed in response to the lowering of IOP. Overall, the measured IOP was higher in patients with greater CCT values (p < 0.001) but this IOP-CCT relationship was most noticeable in patients with normal tension glaucoma and not obvious in those diagnosed with ocular hypertension. Overall, the slope of the IOP-CCT relationship was slightly steeper for those patients prescribed glaucoma medications.

CONCLUSIONS

In the routine assessment of glaucoma patients, corneal thickness can be shown to have an impact on applanation tonometry data. However, this effect may not be uniformly evident in patients with different types of glaucoma and may be different for patients under topical medical treatment.

Changes in central corneal thickness over time: the ocular hypertension treatment study

OBJECTIVE

To describe how much change, if any, occurs between central corneal thickness (CCT) measurements performed an average of 3.8 years apart in participants in the Ocular Hypertension Treatment Study (OHTS) and to identify clinical and demographic factors that are associated with changes in CCT, including baseline intraocular pressure, duration and class of ocular hypotensive medication, medical history, and systemic medication.

DESIGN

Secondary analysis of data from a randomized clinical trial.

PARTICIPANTS

Ocular Hypertension Treatment Study participants. Participants who had undergone incisional intraocular or keratorefractive surgery between CCT measurements were excluded.

TESTING

The first CCT measurements were performed starting in 1999, and the second measurements were performed starting in 2002. Measurements were performed by OHTS certified technicians using an ultrasonic pachymeter under a standardized protocol.

MAIN OUTCOME MEASURE

Central corneal thickness measurement (micrometers).

RESULTS

First and second CCT measurements were available from 73% (1191) of the 1636 OHTS participants randomized. Central corneal thickness decreased a mean rate of -0.74+/-3.5 microm/year between the first and second CCT measurements. The mean medication exposure between first and second CCT measurements in participants originally randomized to observation (n = 595) was 1.1+/-1.6 years, versus 5.0+/-2.7 years in participants originally randomized to medication (n = 596). Central corneal thickness decreased by a mean of 1.0+/-3.4 microm/year among participants originally randomized to observation, compared with 0.5+/-3.5 microm/year among participants originally randomized to medication (P<0.0001). Subgroup analyses suggest that participants treated only with topical prostaglandin analogues (PGAs) between the two CCT measurements had a greater rate of decrease per year than participants treated only with topical beta-blockers.

CONCLUSIONS

The rate of CCT decrease over 3.8 years is comparable to the cross-sectional age differences reported in the OHTS at the first measurement (0.6 microm/year) and comparable to other cross-sectional studies. Use of topical PGAs may be associated with a slightly higher rate of thinning. The modest age- and drug-related rates of thinning observed are unlikely to influence tonometry or clinical decision-making substantially in most clinical situations.

Corneal Thickness Measurement in the Management of Primary Open-angle Glaucoma

OBJECTIVE

To evaluate published literature to assess whether central corneal thickness (CCT) is a risk factor for the presence, development, or progression of glaucomatous optic nerve damage related to primary open-angle glaucoma (POAG).

METHODS

A PubMed literature search limited to English language articles conducted on November 15, 2004 retrieved 195 articles. The authors reviewed these abstracts and selected 57 to review in full text to determine relevance to the assessment questions. A further 24 studies of interest were identified from periodic updates to the literature search, surveillance of the literature, and reference lists of reviewed articles. From the 81 published reports identified, the first author applied specified selection criteria that yielded 37 articles for methodological review because of relevance to the assessment questions. The articles were rated according to the strength of evidence by the panel methodologist. A level I rating was assigned to well-designed properly conducted randomized clinical trials or similar quality-validated cohort studies with appropriate reference standards. A level II rating was assigned to well-designed case-control studies, exploratory cohort studies, and other nonrandomized clinical studies lacking consistently applied reference standards. A level III rating was reserved for poorly designed case-control studies, case series, and papers consisting only of expert opinion without supporting evidence. In addition, each study was graded as positive if it supported a statistical association of CCT with the risk of having or developing glaucomatous optic nerve damage or as negative if no such association was found.

RESULTS

There is strong and consistent level I and level II evidence that CCT is a risk factor for progression from ocular hypertension to POAG. Studies that were rated as providing the highest quality of evidence revealed mixed results with respect to glaucoma prevalence. One population-based study (level II) showed a positive association, another larger study (level I) revealed an association of marginal significance, and 3 studies (all level I) found no association of CCT with POAG prevalence.

CONCLUSIONS

There is strong evidence that measuring CCT is an important component of a complete ocular examination, particularly for patients being evaluated for the risk of developing POAG. Therefore, CCT measurement should be included in the examination of all patients with ocular hypertension. Although the evidence supporting the necessity of measuring CCT as part of screening for POAG or as a risk factor for glaucoma progression is not as strong, intraocular pressure (IOP) is the only modifiable risk factor in the treatment of glaucoma, and CCT has the potential to significantly impact IOP measurement by applanation tonometry in all patients.

Comparing central corneal thickness in a sub-Saharan cohort to African Americans and Afro-Caribbeans

PURPOSE

To evaluate the central corneal thickness (CCT) of Africans in a glaucoma practice in a university teaching hospital in West Nigeria, Africa, and compare results with similar studies carried out in African American and Afro-Caribbean populations.

METHODS

CCT was measured by means of ultrasound pachymetry (pachymeter used was Micropach 200 P+ Pachymeter; Sonomed) in only African participants with either glaucomatous or healthy eyes. After instillation of topical anesthetic, 3 measurements of corneal thickness were taken, and the average thickness for each was calculated. The relationship between CCT and age was studied using correlation analyses and t tests. A total of 70 eyes were included for analysis.

RESULTS

The mean CCT of all participants was 532.00 microm. Glaucoma suspects and patients with glaucoma had corneas thinner than those of normal participants (527.36 and 536.91 microm, respectively); however, the difference was not significant (P = 0.296). Decreasing values of CCT were significantly related to older age (P = 0.002). Men had a significantly higher CCT than women (P = 0.035).

CONCLUSIONS

CCT values in African populations are less than those of whites. Decreasing values of CCT are significantly related to older age, and men have thicker corneas than women. There is a suggestion that CCT is lower in patients with glaucoma than in nonglaucomatous controls; however, the difference is not statistically significant. Comparing our results to other studies in literature, it seems that average CCT is similar between populations living in sub-Saharan Africa and African Americans and Afro-Caribbeans.