Increased corneal thickness in patients with ocular hypertension

Clinical Characteristics and Surgical Outcomes of Turkish Patients With Pediatric Glaucoma Who Underwent Glaucoma Surgery in a University Hospital

PURPOSE

To describe the clinical characteristics and outcomes of a pediatric cohort surgically treated for primary or secondary pediatric glaucoma (PPG/SPG).

METHODS

A retrospective chart review was conducted of all patients with pediatric glaucoma who had surgery between 2013 and 2021. Relevant demographic and clinical data were cumulated and analyzed.

RESULTS

Forty-two eyes of 29 patients (18 girls and 11 boys) were included: 22 (52.4%) primary congenital glaucoma (PCG), 7 (16.7%) juvenile open-angle glaucoma, and 13 (30.9%) SPG. Mean ages at presentation were 2.57 ± 2.87, 131.96 ± 27.71, and 62.09 ± 65.12 months, respectively. In this study, eyes with PCG presented the earliest, with the highest intraocular pressure (IOP) and thickest central corneal thickness (CCT). The mean number of glaucoma surgeries was 1.48 ± 0.71, with 38.1% of the eyes needing two or more glaucoma surgeries; trabeculectomy was the most frequent glaucoma surgery in this cohort. After surgical intervention, the overall mean IOP dropped from 32.25 ± 12.97 to 18.10 ± 9.23 mm Hg (P < .001). Moreover, the percentage using antiglaucoma medications decreased from 100% to 35.7% at the final visit, as did the number of medications prescribed per eye (2.69 ± 0.92 vs 1.05 ± 1.46, P ≤ .001). Mean best corrected visual acuity (BCVA), in patients who could have their BCVA measured, improved from 0.61 ± 0.61 to 0.53 ± 0.51 logMAR at final follow-up.

CONCLUSIONS

Surgical intervention was shown to provide a well-controlled IOP, decrease dependance on glaucoma medications, and improve BCVA in both PPG and SPG. Multiple surgical interventions may be necessary in the treatment of some pediatric patients with glaucoma. Prognostically, thicker CCT was significantly associated with worse IOP control, more glaucoma surgeries, and more antiglaucoma medications at the final visit. Initial BCVA correlated significantly with BCVA at the final visit. [J Pediatr Ophthalmol Strabismus. 2024;61(3):188-197.].

Postoperative Changes in Central Corneal Thickness and Intraocular Pressure in a Prospective Cohort of Congenital Cataract Patients

PURPOSE

To evaluate changes in central corneal thickness (CCT) and intraocular pressure (IOP) in children after surgery for congenital cataracts and to investigate the association between CCT and IOP.

METHODS

For this prospective observational cohort study, we recruited patients undergoing surgery for unilateral or bilateral congenital cataracts. CCT and IOP were measured before surgery and 1, 3, 6, 12, and 24 months after surgery.

RESULTS

Seventy-six children (152 eyes) were enrolled; 33 eyes were unaffected by cataracts, 77 were aphakic, and 42 were pseudophakic. In aphakic eyes, mean CCT increased by 31.14 ± 44.32 μm at 12 months postoperation and 33.09 ± 35.42 μm at 24 months postoperation; this increase was significantly higher than that in pseudophakic eyes 12 months after surgery (8.36 ± 19.91 μm; P < 0.001) and 24 months after surgery (0.31 ± 14.19 μm; P = 0.024). However, no significant differences in IOP were found between the different phakic states at 12 and 24 months postoperation (P = 0.672 and P = 0.080, respectively). There were also no significant differences in CCT and IOP before and after surgery in the unaffected eyes.

CONCLUSIONS

Mean CCT peaked at 12 months, and the mean IOP remained normal in both the aphakic and pseudophakic eyes during this study. CCT and IOP were positively correlated, regardless of the phakic status or age, a relationship which suggests that both parameters should be monitored closely in postsurgical patients for up to 12 months and in this time, may impact the ability to diagnose glaucoma.

Central Corneal Thickness Variances Among Different Asian Ethnicities in Glaucoma and Nonglaucoma Patients

OBJECTIVE

To compare the central corneal thickness (CCT) between different ethnicities and particularly Asian subethnic groups that may contribute to the different glaucoma diagnoses using the optical low-coherence reflectometry technique.

METHODS

A retrospective study of 6 years including 1512 eyes of 929 patients of the Beckman vision center, University of California, San Francisco from 2011 to 2017 had their biometric parameters, including CCT, measured with the Lenstar. Patients were categorized into African Americans, Caucasians, Hispanics, Pacific Islanders, and Asians. Asians were further subcategorized into Chinese, Vietnamese, Koreans, Filipinos, and Japanese.

RESULTS

Among 1356 patients who had their CCT measured by Lenstar from 2011 to 2017, 1512 eyes of 929 patients were included. The study population included 462 Caucasians (52.96%), 60 African Americans (6.46%), 92 Hispanics (9.9%), 32 Pacific Islanders (3.44%), 130 Chinese (13.99%), 52 Filipinos (5.6%), 37 Vietnamese (3.98%), 34 Koreans (3.66%), and 30 Japanese (3.23%). African Americans had the thinnest CCT with a mean of 518.62±40.3 followed by Asians with a mean of 539.29±34.1. Among the Asian study sample, the Chinese had the thinnest CCT with a mean of 537.66±32.5. CCT was adjusted for age, sex, glaucoma diagnosis, diabetes status, and prostaglandin analogs use for >12 months.

CONCLUSIONS

Optical low-coherence reflectometry is a widely used technology, which can measure CCT. Our study confirms that African Americans have the thinnest corneas followed by Asians. In the latter group, relatively thin CCT may partly explain their high rates of normal-tension glaucoma.

Role of Central Corneal Thickness on Baseline Parameters and Progression of Visual Fields in Open Angle Glaucoma

Purpose

To evaluate the relationship of central corneal thickness (CCT) to baseline visual field parameters and visual field progression in patients with primary open-angle glaucoma (POAG).

Methods

Charts of consecutive patients with POAG were reviewed to obtain visual field data. Visual field was measured by standard threshold static perimetry. Variables analyzed included mean deviation (MD) and pattern standard deviation (PSD).

Results

A total of 121 eyes examined over 4 years were evaluated. A significant negative relationship between CCT and PSD (correlation coefficient: −0.02, p<0.05) was found. Analyses comparing CCT to change in PSD and MD (visual field progression) were statistically not significant.

Conclusions

Patients with thinner corneas initially present with a greater visual field defect, indicating that thin corneas may contribute to advanced glaucomatous damage at the time of diagnosis. However, CCT does not seem to be a significant risk factor for progression of the disease.

Correlation Between Dynamic Contour Tonometry, Uncorrected and Corrected Goldmann Applanation Tonometry, and Stage of Glaucoma

Importance

Accurate determination of intraocular pressure (IOP) is crucial for the diagnosis and management of glaucoma. Objective clinical evaluation of the correction equations for Goldmann applanation tonometry (GAT) is lacking.

Objectives

To investigate the difference between corrected and conventional GAT and Pascal dynamic contour tonometry (DCT) measurements, as well as the correlation between discordant IOP values and stage of glaucoma.

Design, Setting, and Participants

This prospective cross-sectional case series was conducted at the Department of Ophthalmology, University Hospital Zurich, and Talacker Eye Center between July 1, 2011, and May 31, 2016, among 112 white patients with glaucoma.

Interventions

Intraocular pressure measurements were performed with GAT and DCT in a randomized order. Goldmann applanation tonometry measurements were modified with 5 correction equations.

Main Outcomes and Measures

The primary end point was degree of concordance between corrected or uncorrected GAT and DCT measurements. The secondary end point was association between discordant IOP measurements and the stage of glaucoma, as assessed by the Glaucoma Severity Score.

Results

Among the 112 patients (67 women and 45 men; mean [SD] age, 66.3 [13.1] years), 63 of the eyes in the study (56.3%) were left eyes and 85 patients (75.9%) were taking ocular antihypertensive medications. Mean (SD) IOP was 20.3 (4.5) mm Hg (95% CI, 19.4-21.1) as measured by DCT and 17.0 [4.1] mm Hg (95% CI, 16.3-17.8) as measured by GAT. The mean (SD) discordance between DCT and GAT measurements was -3.3 (2.0) mm Hg (95% CI, 2.9-3.6). The 5 corrected GAT values ranged from -2.7 to -5.4 mm Hg compared with DCT. The mean (SD) result of the Dresdner correction formula (17.6 [4.1] mm Hg) was closer to the DCT measurement than the original GAT measurement. The mean (SD) Glaucoma Severity Score was 4.7 (3.4) (95% CI, 4.1-5.4). The uncorrected discordance IOPDCT - IOPGAT showed a positive correlation with the Glaucoma Severity Score (rs = 0.33; P < .001) and a negative correlation with central corneal thickness (rs = -0.22; P = .02).

Conclusions and Relevance

In comparison with DCT measurements, these data suggest that GAT values are significantly discordant in eyes with thin corneas and advanced glaucoma. Application of GAT-based correction formulas involves a possible risk of creating an even greater number of unpredictable measurement errors. Hence, we advise with caution, especially pertaining to eyes with thin corneas, to not place reliance on GAT readings, and abandon any correction formula.

Trial Registration

clinicaltrials.gov Identifier: NCT01474070.

Effect of age, sex, and refractive errors on central corneal thickness measured by Oculus Pentacam®

BACKGROUND

Central corneal thickness (CCT) can be used to assess the corneal physiological condition as well as the pathological changes associated with ocular diseases. It has an influence on the measurement of intraocular pressure and is being used as a screening tool for refractive surgery candidates. The aim of this study was to determine the median CCT among normal Pakistani population and to correlate CCT with age, sex, and refractive errors.

METHODS

We conducted a retrospective analysis of 5,171 healthy eyes in 2,598 patients who came to Hashmanis Hospital, Karachi, Pakistan. The age of the patients ranged from 6 to 70 years. The refractive error was gauged by an auto-refractometer, and CCT was measured using Oculus Pentacam^®.

RESULTS

The median CCT of our study was 541.0 μm with an interquartile range (IQR) of 44.0 μm. The median age was 26.0 years (IQR: 8.0). Median spherical equivalent (SE) of the patients was -4.3 D (IQR: 3.3) with the median sphere value as -4.0 D (IQR: 3.8). Lastly, the median cylinder was -1.0 D (IQR: 1.3). Age has a weak negative correlation with CCT (r=-0.058) and shows statistical significance (P<0.001). Additionally, males had thinner CCT readings than females (P=0.001). The cylinder values, on the other hand, had a significant (P=0.004) and positive correlation (r=0.154). Three values showed no significant correlation: sphere (P=0.100), SE (P=0.782), and the left or right eye (P=0.151).

CONCLUSION

Among the Pakistani population, CCT was significantly affected by three variables: sex, age, and cylinder. No relationship of CCT was observed with the left or right eye, sphere, and SE.

A structural model for the in vivo human cornea including collagen-swelling interaction

A structural model of the in vivo cornea, which accounts for tissue swelling behaviour, for the three-dimensional organization of stromal fibres and for collagen-swelling interaction, is proposed. Modelled as a binary electrolyte gel in thermodynamic equilibrium, the stromal electrostatic free energy is based on the mean-field approximation. To account for active endothelial ionic transport in the in vivo cornea, which modulates osmotic pressure and hydration, stromal mobile ions are shown to satisfy a modified Boltzmann distribution. The elasticity of the stromal collagen network is modelled based on three-dimensional collagen orientation probability distributions for every point in the stroma obtained by synthesizing X-ray diffraction data for azimuthal angle distributions and second harmonic-generated image processing for inclination angle distributions. The model is implemented in a finite-element framework and employed to predict free and confined swelling of stroma in an ionic bath. For the in vivo cornea, the model is used to predict corneal swelling due to increasing intraocular pressure (IOP) and is adapted to model swelling in Fuchs' corneal dystrophy. The biomechanical response of the in vivo cornea to a typical LASIK surgery for myopia is analysed, including tissue fluid pressure and swelling responses. The model provides a new interpretation of the corneal active hydration control (pump-leak) mechanism based on osmotic pressure modulation. The results also illustrate the structural necessity of fibre inclination in stabilizing the corneal refractive surface with respect to changes in tissue hydration and IOP.

Central corneal thickness in primary angle closure and open angle glaucoma

Purpose:

To quantitatively analyze central corneal thickness (CCT) in patients with primary angle closure glaucoma (PACG) and primary open-angle glaucoma (POAG), and to evaluate its correlation with severity of glaucoma.

Methods:

In this retrospective study, records of patients with previously diagnosed POAG or PACG at a tertiary glaucoma service were reviewed. CCT was measured by ultrasound pachymetry. Mean deviation (MD) on visual field (VF) testing was recorded for glaucoma severity determination. CCT and age- and sex-adjusted CCT were compared among the study groups using Student's t-test and analysis of covariance (ANCOVA), respectively. Univariate and multivariate regression models were used for correlation of age, MD and CCT.

Results:

A total of 115 patients with PACG, 215 with POAG, and 100 normal controls were included with mean age of 64.1 ± 10.4, 59.9 ± 10.5, and 62.04 ± 10.80 years, respectively. CCT was thicker in PACG eyes (545.5 ± 46.1 μm) as compared to POAG eyes (531.7 ± 37.3 μm) and controls (531.0 ± 38.3 μm) even after age and gender adjustment (ANCOVA, P = 0.05). CCT was found to decrease with increasing age only in the POAG group (β = -0.57, P = 0.01). Disease severity (MD of VF) was significantly and inversely correlated with CCT in both POAG and PACG eyes (β = 1.89, P = 0.02; and β = 1.38, P = 0.04, respectively) after age and sex correction.

Conclusion:

PACG eyes had thicker CCT as compared to POAG and normal healthy eyes in Iranian subjects. Severity of the disease was inversely correlated with CCT in eyes with both POAG and PACG.

Cornea in PCOS patients as a possible target of IGF-1 action and insulin resistance

OBJECTIVES

Previous studies suggest that serum IGF-1 is higher in women with polycystic ovary syndrome (PCOS). The ophthalmologic effects of IGF-1 excess have not yet been investigated in women with PCOS. The aim of the current study is to compare the corneal thickness of patients with PCOS and those of healthy subjects.

METHODS

Forty three patients with PCOS and 30 age-matched and gender-matched healthy individuals were enrolled in this cross-sectional study. Central corneal thickness (CCT) was measured in patients with PCOS and in healthy individuals with an ultrasound pachymeter. IGF-1 values were also determined in the study group.

RESULTS

Women with PCOS had significantly higher levels of IGF-1 and homeostasis model assessment (HOMA-IR) levels than the control group. Right and left CCT measurements were higher in the PCOS group than in the control group. A positive correlation between IGF-1 and right and left CCT was identified in both groups. In multiple linear stepwise regression analyses, IGF-1 independently and positively associated with HOMA-IR in women with PCOS. A correlation between total testosterone and CCT was identified in the whole group. In multiple stepwise regression analyses, total testosterone independently and positively associated with left central corneal thickness in the whole group.

CONCLUSIONS

These findings indicate that PCOS has target organ effects on the eye. Consequently, it can change central corneal thickness. Higher IGF-1 levels seem to be the main causes of increased corneal thickness. Insulin resistance in PCOS is one of the underlying causes and promotes increase in IGF-1. We suggest a careful and detailed corneal evaluation in PCOS patients to prevent the potential risk of increased CCT, in addition to the already-known complications.

The biometric study in different stages of primary angle-closure glaucoma

PURPOSE

This study compared the general and ocular biometric characteristics of normal, primary angle closure (PAC), and primary angle-closure glaucoma (PACG) patients to better understand the possible relationship between differences in ocular parameters that might predict risk for PACG in PAC patients.

METHODS

One hundred normal, 90 PAC, and 90 PACG eyes were retrospectively reviewed. General characteristics such as age, gender, body height, body weight, blood pressure, pulse, systemic diseases, and education level were recorded. Ocular findings included visual acuity, intraocular pressure, refraction, cup to disc ratio, and ocular biometry. Ocular biometry was obtained by A-scan ultrasonography (Digital A/B scan 5500; Sonomed Inc., Lake Success, NY, USA). The parameters recorded were anterior chamber depth (ACD), lens thickness (LT), axial length (AXL), lens/axial length factor (LAF), and relative lens position (RLP).

RESULTS

Although the controls, PAC group, and PACG group were found to be significantly different in age (62.7±9.8; 65.3±7.5; and 66.0±7.4, respectively), there were no gender differences. With regard to ocular parameters, the ACD tended to decrease and the LT and LAF tended to increase from normal to PAC to PACG. The eyes of the PACG group had significantly shallower ACD (P<0.001) and thicker lens (P<0.001) than those of the PAC group. While PAC had similar lens position to the control group, PACG had more anteriorly positioned lens than the PAC group (P<0.001). Logistic regression analysis found a significant association between a decrease in ACD and increased risk of PACG (odds ratio (OR)=3.59 for 0.2 mm decrease in ACD) as well as a significant association between an increase in LT and increased risk of PACG (OR=1.30).

CONCLUSIONS

In addition to LT, a shallower ACD owing to a change in RLP may have a role in the progression from PAC to PACG. Owing to the differences of certain biometric characteristics between PAC and PACG, A-scan ultrasonography might potentially be used for the early detection of PACG in PAC eyes.

Central corneal thickness in Chinese subjects with primary angle closure glaucoma

PURPOSE

To characterize central corneal thickness (CCT) in Chinese eyes with primary angle closure glaucoma (PACG).

METHODS

CCT was measured by ultrasound pachymetry in PACG eyes and compared with primary open-angle glaucoma (POAG) eyes. POAG eyes were further subdivided into high-tension glaucoma (HTG) and normal-tension glaucoma (NTG) for analysis. PACG eyes had glaucomatous optic neuropathy and visual field loss, an angle in which at least 180 degrees of angle in which the posterior trabecular meshwork was not visible, and raised intraocular pressure (IOP) and/or peripheral anterior synechiae. Both HTG (IOP >21 mm Hg) and NTG (IOP consistently <21 mm Hg) eyes had glaucomatous optic neuropathy with compatible visual field defects and open angles. Further comparison was made with CCT data of 1067 normal subjects previously enrolled in a population-based study.

RESULTS

We enrolled 154 patients with PACG and 300 with POAG. Mean age of PACG patients was 68.1±8.3 years compared with 71.1±12.4 years in POAG patients (P=0.002). There was no difference in mean CCT of PACG eyes (541.28±33.95 μm) and POAG eyes (539.28±34.84 μm, P=0.56) or normal eyes of control subjects (536.74±31.08 μm) (P=0.07). However, mean CCT of NTG eyes (535.23±36.10 μm) was significantly lower than that of HTG eyes (543.44±33.10 μm, P=0.04), and HTG eyes had thicker CCT than normal eyes (P=0.01).

CONCLUSIONS

PACG eyes had similar CCT as those with POAG or normal eyes in Chinese subjects.

Central Corneal Thickness in Microphthalmic Eyes with or without History of Congenital Cataract Surgery

Purpose

TO determine the central corneal thickness (CCT) in microphthalmic aphakic or Pseudophakic eyes as well as in microphthalmic eyes without any history of eye surgery.

Methods

Thirty-two patients with a mean age of 6.41 ±5.24 years after congenital cataract surgery with absolute microcornea, i.e., horizontal corneal diameter (HCD) <10 mm, or relative microcornea, i.e., HCD 10–11 mm but in the affected eye at least 0.5 mm smaller compared to the fellow eye, formed group A. Thirteen patients of mean age 0.94±1.22 years with absolute or relative microcornea plus another developmental anomaly of an eye without any history of eye surgery formed group B. The patients with corneal edema or scars were excluded. The control group consisted of 124 healthy school-aged children. Horizontal corneal diameter was measured with caliper and CCT with an ultrasound pachymeter. In infants, these measurements were performed under general anesthesia.

Results

In 48 eyes in group A and in 16 eyes in group B, the mean CCT was 635.13±65.35 μm and 642.31±93.07 μm, respectively, which was significantly greater (p<0.0001 and p=0.0018) in comparison with the mean CCT (553.58±33.12 μm) in the control group. Regression curve demonstrated the significant increase of CCT values along with the decrease of HCD in microphthalmic eyes.

Conclusions

Small corneas in microphthalmic eyes either with or without congenital cataract surgery have significantly higher CCT. The results demonstrate significant negative correlation between horizontal corneal diameter and CCT.

Central corneal thickness in black Cameroonian ocular hypertensive and glaucomatous subjects

PURPOSE

To evaluate central corneal thickness (CCT) in a black Cameroonian population of ocular hypertensive and glaucomatous subjects.

MATERIAL AND METHODS

This was a prospective study undertaken with an ultrasonic pachymeter from January 2009 to December 2009 in an eye clinic (INNEL Medical center) in Yaoundé, Cameroon.

RESULTS

One hundred subjects (200 eyes) were enrolled in the study. Sixty subjects were glaucomatous (primary open angle glaucoma, POAG group), and 40 ocular hypertensive (OHT group). The mean age of the sample was 52.60 ± 12.23 years. For the whole sample, CCT was 534.71 ± 37.95 μm in the right eye and 533.61 ± 37.67 μm in the left eye, with no statistically significant difference between the 2 eyes (P = 0.446). CCT in the POAG group was 526.30 ± 37.34 μm in the right eye and 524.90 ± 35.92 μm in the left eye. CCT in the OHT group was 547.32 ± 35.71 μm in the right eye and 546.67 ± 36.85 μm in the left eye. There was a statistically significant difference between CCT of the 2 groups (right eye: P = 0.013; left eye: P = 0.007).

CONCLUSION

Mean CCT of ocular hypertensive subjects was thicker than CCT of glaucomatous ones in our Cameroonian sample. However, in both ocular hypertensive or glaucomatous patients, CCT of black Cameroonians is thinner than that reported in other studies in Caucasian populations.

A clinical comparison of dynamic contour tonometry versus Goldmann applanation tonometry

BACKGROUND AND OBJECTIVE

To compare the intraocular pressures (IOP) obtained with dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) and to determine the dependency of both devices on corneal structure.

PATIENTS AND METHODS

One hundred forty eyes of 70 patients were included. Cases with corneal pathologies, former glaucoma diagnosis, and systemic diseases were excluded. All eyes underwent measurements of central corneal thickness (CCT) and corneal curvature. IOP measurements were obtained with GAT and DCT. The agreement of measurements was statistically analyzed.

RESULTS

The correlation of IOP values obtained with DCT and GAT was statistically significant. The mean DCT values were 0.46 ± 2.55 mm Hg higher than those of GAT, but this difference was statistically insignificant. Bland-Altman plots showed reasonable inter-method agreement between DCT and GAT measurements. GAT readings were significantly affected by CCT, but DCT measurements were affected by age and corneal curvature.

CONCLUSION

DCT is a reliable method of assessing IOP and is less dependent on central corneal thickness. This new technology may be a promising step forward in the management of glaucoma. Further studies are required to validate these observations.

Central corneal thickness in subjects with glaucoma and in normal individuals (with or without pseudoexfoliation syndrome)

Objective:

The evaluation of central corneal thickness (CCT) in subjects with pesudoexfoliation glaucoma (PEXG), primary open-angle glaucoma (POAG), and in normotensive individuals with or without pseudoexfoliation syndrome (PXS).

Study design/patients and methods:

CCT was evaluated with ultrasound pachymetry in a total of 179 individuals: 32 had bilateral PEXG, 55 had bilateral POAG, 35 had PXS, and 57 were healthy individuals without PXS.

Results:

CCT in PEXG eyes (526.00 ± 34.30 μm) was significantly thinner compared to POAG eyes (549.36 ± 39.3 μm) (P = 0.027) and normal control eyes with (550.64 ± 39.0 μm) or without PXS (547.36 ± 33.1 μm), (P = 0.039 and 0.048 respectively). No statistically significant difference was found comparing CCT values of POAG eyes to control group eyes.

Conclusion:

The evaluation of CCT is necessary in all patients with glaucoma and especially in those with PEXG due to the thinner cornea and the risk of underestimation of intraocular pressure.

Relationship between central corneal thickness and visual field defect in open-angle glaucoma

PURPOSE

To explore the relationship between central corneal thickness (CCT) and visual field defect in open-angle glaucoma (OAG).

METHODS

In this cross-sectional study, we tested 344 eyes in 344 eligible patients, including 233 with normal-tension glaucoma (NTG) and 111 with primary open-angle glaucoma (POAG). The association among variables, especially that between visual field defect and CCT, was probed by multivariate regression in eyes with NTG or POAG, and in all eyes. All eyes were divided into early, moderate, or severe visual field defect groups according to Anderson's classification. Statistical analysis was performed for all cases, and for the three CCT groups.

RESULTS

Multivariate regression analysis revealed an association between CCT and visual field defect in eyes with NTG but not in eyes with POAG or in all eyes. The eyes with early visual field defect had greater CCT than did those with severe visual field defect (533.2 versus 519.0 microm). The eyes with greater CCT had better visual field indices than did those with thinner CCT (-6.91 versus -9.17 dB).

CONCLUSIONS

Central corneal thickness is a factor associated with the status of the visual field defect: a greater CCT is associated with a better visual field index. Other factors such as the glaucoma subtype play a role in the effect of CCT on visual field defect.

Biometric and corneal topographic characteristics in patients with Weill-Marchesani syndrome

PURPOSE

To determine the biometry of ocular structures and corneal topographic characteristics in patients with Weill-Marchesani syndrome.

SETTING

Department of Ophthalmology, Shiraz University of Medical Sciences, Shiraz, Iran.

METHODS

Patients with Weill-Marchesani syndrome (syndrome group) and age-matched normal subjects (control group) were evaluated. All had a complete ocular examination including refraction and analysis using Fourier transformation, slitlamp biomicroscopy, pachymetry, keratometry, and ocular biometry. The following A-scan parameters were measured: anterior chamber depth (ACD), lens thickness, axial length (AL), lens-AL factor, and relative lens position (RLP). Corneal topography examinations were performed in the syndrome group only.

RESULTS

The syndrome group comprised 7 female patients and the control group, 20 female subjects. The syndrome group had statistically significantly higher myopia and corneal astigmatism than the control group (P<.0001). Oblique astigmatism was common in the syndrome group, showing a strong right-left specificity (right eyes' axes in the 135-degree meridian, left eyes' axes in the 45-degree meridian). The syndrome group had a statistically significantly shorter AL, shallower ACD, thicker lens, higher calculated lens power, and a higher lens-AL factor (P<.0001). However, there was no statistically significant difference in RLP (P = .32). The syndrome group also had statistically significantly thicker corneas and higher keratometry values (P<.0001).

CONCLUSION

Characteristic ocular findings in patients with Weill-Marchesani syndrome were a steep, thick cornea with a strong right-left specificity of corneal astigmatism; a thick lens; a short AL; and a shallow ACD.

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.

Correlation between corneal and scleral thickness in glaucoma

PURPOSE

To assess the correlation between central corneal thickness (CCT) and anterior scleral thickness (ST) in patients of primary open-angle glaucoma (POAG), normal tension glaucoma (NTG), and ocular hypertension (OHT).

PATIENTS AND METHODS

Consecutive patients with OHT, POAG, NTG, and normal individuals were recruited. CCT was measured by ultrasonic pachymetry, whereas ST was measured using ultrasonic biomicroscopy at the temporal quadrant, 2 mm posterior to the scleral spur. Investigators were masked to the diagnosis and CCT/ ultrasonic biomicroscopy data. Correlation between mean CCT and ST was analyzed.

RESULTS

One hundred and twenty-four subjects (31 with OHT, 31 with POAG, 31 with NTG, and 31 normal individuals) were enrolled. The CCT (OHT 548.06+/-30.45 microm; POAG 519.39+/-42.95 microm; NTG 505.81+/-27.23 microm; controls 529.90+/-43.40 microm) was found to be thicker in patients with OHT than POAG (P=0.004) or NTG (P<0.01). There was also a difference in CCT between NTG and control eyes (P=0.012). The ST (OHT 755.03+/-69.58 microm; POAG 738.45+/-66.83 microm; NTG 708.74+/-71.58 microm; controls 724.45+/-73.27 microm) was thicker in the OHT group than in NTG patients (P=0.012). No significant difference in ST was found among other groups. Among subgroups, the correlation between CCT and ST was found only among the patients with NTG (r=0.440, P=0.013). However, no correlation was seen between CCT and ST in patients with OHT, POAG, and controls.

CONCLUSIONS

There is a correlation between CCT and ST among the NTG group but no correlation was seen among OHT, POAG, and controls.

Age and racial variation in central corneal thickness of preschool and school-aged children

PURPOSE

The purpose of this study was to determine variations in central corneal thickness (CCT) of preschool and school-aged African American and white children. Secondary aims were to assess possible correlations between CCT measurements and gender, axial length, intraocular pressure (IOP), family history of glaucoma, or history of prematurity.

METHODS

Contact ultrasound was used to measure CCT and axial length in 76 white and 60 African American children between the ages of 7 months and 18 years. A questionnaire was completed by the parents or guardians, including medical and family history. Statistically significant associations and differences were assessed using the independent t test, analysis of variance, and linear regression. All associations were defined as significant when the alpha value was less than 0.05 (two-tailed).

RESULTS

Mean CCT was thinner in African American children (535 +/- 35 microm) compared to white children (559 +/- 38 microm) (P < .001). The corneal thickness in children ages 10 to 18 years was significantly higher than in all other age groups in both African American (P = .03) and white (P < .005) children. No association was found between CCT and gender, axial length, IOP, or family history of glaucoma. Premature children had thinner CCT (536 +/- 40 pm) than full-term children (552 +/- 38 microm) (P = .009).

CONCLUSIONS

African American children have a thinner CCT compared to white children at all ages. Children of both racial groups have an increasing value of CCT with increasing age after approximately age 10 years. Children born prematurely have a thinner CCT than full-term children.

Effects of central corneal thickness on the efficacy of topical ocular hypotensive medications

PURPOSE

To determine the effect of central corneal thickness (CCT) on the efficacy of intraocular pressure (IOP)-reducing drugs in patients with ocular hypertension (OHT).

METHODS

This retrospective study analyzed research records of 115 OHT patients and 97 ocular normotensive (ONT) volunteers. CCT was measured by slit-lamp pachymetry and IOP by pneumatonometry. The OHT patients were divided into Thick (>540 microm, n=52) and Thin (<or=540 microm, n=63) Cornea groups. Measurements in the OHT group were made after washout of all IOP-lowering drugs and at 1 week of treatment with latanoprost 0.005%, dorzolamide 2%, brimonidine 0.2%, apraclonidine 0.5%, pilocarpine 2%, or unoprostone 0.15% to 1 eye and vehicle contralaterally. ONT volunteers also were divided into Thick (n=34) and Thin (n=63) Cornea groups. Results were compared between groups using unpaired t tests or nonparametric Wilcoxon tests and within groups using linear regression analyses.

RESULTS

Baseline IOPs were not different between CCT groups of OHT patients or of ONT volunteers. After 1 week of drug treatment, IOP was significantly (P=0.02) lower in the OHT Thin Cornea group (16.0+/-3.0 mm Hg, mean+/-SD) than the OHT Thick Cornea group (17.4+/-2.8 mm Hg). There was a positive correlation between IOP and CCT (R=0.06, P=0.007) in OHT drug-treated eyes, but not OHT vehicle-treated or ONT untreated eyes. The final IOP was significantly lower in the Thin than the Thick Cornea group treated with brimonidine (P=0.02) but not with latanoprost (P=0.91).

CONCLUSIONS

When dosed with IOP lowering drugs, eyes with thinner corneas had lower IOPs than eyes with thicker corneas. This suggests a reduced efficacy of some glaucoma medications in ocular hypertensive patients with thick corneas.

Corneal curvature and central corneal thickness in eyes with pseudoexfoliation syndrome

BACKGROUND

Previous studies have reported different central corneal thickness (CCT) values in eyes with pseudoexfoliation syndrome (PXS). There has been no report about corneal curvature (CC) in PXS eyes. The aim of this study was to investigate the CCT together with the CC in PXS eyes with and without glaucoma.

METHODS

The CC (simulated keratometry 1 [SimK1], SimK2, and mean K) and CCT were prospectively studied by rotating a Scheimpflug camera in 72 PXS eyes and comparing them with 65 normal eyes.

RESULTS

In all PXS eyes, the mean K was significantly steeper than in control eyes (44.1 [SD 1.5] diopters (D) vs. 43.2 [SD 2.0] D, p = 0.04). When PXS eyes were subcategorized, the mean K was significantly steeper in both normotensive PXS eyes (44.6 [SD 1.6] D) and pseudoexfoliation glaucoma (PEXG) eyes (44.0 [SD 1.2] D) than normal eyes (43.2 [SD 2.0] D) (p = 0.001 and 0.02, respectively). In all PXS eyes, the mean CCT (546.4 [SD 39.6] microm) was not significantly different than the control eyes (542.9 [SD 32.2] microm) (p = 0.56). When PXS eyes were subcategorized, however, the CCT was significantly thinner in normotensive PXS eyes and significantly thicker in PEXG eyes.

INTERPRETATION

It appears that PEXG eyes have a significantly steeper CC and higher CCT than normal eyes. This could be of clinical significance because overestimation of true intraocular pressure may then occur in these eyes.

Cataract surgery for congenital cataract: endothelial cell characteristics, corneal thickness, and impact on intraocular pressure

PURPOSE

To investigate whether central corneal thickness (CCT), endothelial cell characteristics, and intraocular pressure (IOP) are affected in patients with previous congenital cataract surgery and to focus on their clinical significance.

METHODS

CCT and IOP measurements and specular microscopy were performed in 31 eyes of 17 cases of extracted congenital cataracts and 40 eyes of 20 age- and sex-matched participants as control group. The mean of three pachymetry measurements of the central cornea was taken as CCT. IOP was checked using an applanation tonometer.

RESULTS

The mean corneal thickness of the eyes with extracted congenital cataract (632+/-45 microm) was significantly greater than that of the control eyes (546+/-33 microm; p<0.001). There was no significant difference in the corneal endothelial cell count, coefficient of variation (CV), and mean cell area (AVG) of endothelial cells between operated eyes and the control group. The mean measured IOP in the operated group (22.8+/-3.3 mm Hg) was significantly greater than IOP in controls (14.1+/-1.8 mm Hg, p<0.001).

CONCLUSIONS

Although the corneas were clinically clear and there was no significant difference in endothelial characteristics of eyes with extracted congenital cataract and controls, central corneas of operated eyes were significantly thicker than those of controls. To differentiate the actual glaucoma from ocular hypertension in these patients, the central corneal thickness measurement should strongly be considered.

Central Corneal Thickness in the European Glaucoma Prevention Study

PURPOSE

To measure central corneal thickness (CCT) within the participants of the European Glaucoma Prevention Study (EGPS). This study was designed to test if lowering intraocular pressure (IOP) by means of dorzolamide is able to prevent or delay conversion from ocular hypertension to glaucoma.

DESIGN

Randomized, double-masked, controlled, observational clinical trial.

PARTICIPANTS

Eight hundred fifty-four of 1077 ocular hypertensive participants within the EGPS were investigated. Four hundred twenty-nine patients were treated with dorzolamide and 425 patients received placebo.

INTERVENTION

Treatment with dorzolamide or placebo (the vehicle of dorzolamide) in 1 or both eyes.

MAIN OUTCOME MEASURES

Central corneal thickness as measured by ultrasound pachymetry (DGH-500 Pachette; DGH Technologies, Exton, PA). The CCT measurements were obtained in the morning before measuring IOP. Five measurements were taken from each eye of each patient within 5 minutes of application of anesthetic eye drops.

RESULTS

Mean CCT was 572.6+/-37.4 microm (range, 458.5-695.6 microm). The CCT was higher in younger patients, male patients, and diabetic patients. Mean CCTs for the 429 patients receiving dorzolamide were 574.2+/-38.48 microm (range, 458.5-695.6 microm) and 571.0+/-36.21 microm (469.7-690.1 microm) for the 425 patients receiving placebo (P = 0.205). Central corneal thickness did not correlate with refraction, baseline IOP, or systemic hypertension.

CONCLUSION

Central corneal thickness measurements within the EGPS were greater than those reported in other studies of normal eyes without ocular hypertension. Larger CCT measurements correlated with male gender, younger age, and diabetes.

Central corneal thickness in congenital glaucoma

PURPOSE

The aim of this study was to compare central corneal thickness between eyes with congenital glaucoma and normal fellow eyes in unilateral glaucoma or less affected fellow eyes in bilateral glaucoma.

METHODS

Eyes of consecutive phakic children with congenital glaucoma and previous glaucoma surgery were examined under chloral hydrate. Complete ophthalmologic examination, central corneal thickness (CCT), axial length, and corneal diameter measurements were performed. Patients were included in the study if presented with intraocular pressure (IOP) less than 21 mm Hg and no biomicroscopic signs of corneal edema.

RESULTS

Nine patients were included in the study. The mean CCT in the more affected eye/glaucomatous eye was 522.3 +/- 65.2 microm and in the less affected eye/healthy eye was 579.7 +/- 44.5 microm. This difference was statistically significant (P = 0.0013).

CONCLUSION

CCT was significantly thinner in glaucomatous eyes than in normal fellow eyes in phakic children with congenital glaucoma. This finding may be another confounding factor when measuring IOP in these patients.

Inconsistency of the Published Definition of Ocular Hypertension

PURPOSE

To examine the variability and to evaluate the influence of the Ocular Hypertension Treatment Study (OHTS) on the criteria for published definition of ocular hypertension (OH).

DESIGN

Systematic literature review.

METHODS

All articles about OH published between January 1995 and July 2005 from the 3 clinical journals of ophthalmology were identified by a literature search. They were reviewed to determine the criteria used to define OH, including intraocular pressure and central corneal thickness, visual field and optic disc assessment.

RESULTS

There were 133 studies published on OH during the period under study. As a goal of the current study was to evaluate the influence of the publication of the OHTS results on the definition of OH used in the literature, all reports from the OHTS and its ancillary studies (n = 11) were excluded from the main analysis. After the exclusion of the OHTS reports, a total of 122 studies were used in the analysis. The intraocular pressure cut-off level used for OH diagnosis ranged from 18 to 26 mm Hg, with a mode of 22 mm Hg (49.2%). Only 13.1% of the articles reported central corneal thickness, and these were distributed evenly during the 10-year period under study. Visual field assessment was reported by most of the studies (110; 90.2%), but only 45% of them defined the criteria to classify a field as normal or glaucomatous. Further, only 37 of the 57 articles that reported the method of optic disc assessment described the criteria used to classify optic discs.

CONCLUSIONS

The criteria used to define OH during the past 10 years have been highly variable. This wide variation suggests the important need for a standardized definition of OH.

Comparison between central corneal thickness measurements by ultrasound pachymetry and optical coherence tomography

PURPOSE

Measurement of central corneal thickness (CCT) plays an important role in both diagnostic and therapeutic assessment of ocular diseases. Although ultrasound pachymetry (U-PACH) is regarded as the golden standard for measurement of CCT, optical coherence tomography (OCT) may offer advantages as it can locate the central cornea with precision with no corneal touch. Nevertheless, the agreement of OCT with U-PACH has not yet been gauged by Bland-Altman analysis. This study compares CCT measurement by OCT with that by U-PACH.

METHODS

Healthy subjects without ocular abnormality (except refractive errors less than or equal to -6.0 D), contact lens wear or ocular surgery were recruited. CCT was measured in one eye of normal subjects using OCT and U-PACH. Results were compared using correlation and Bland-Altman plots.

RESULTS

Fifty subjects were recruited. Mean +/- SD CCT measured by OCT was 565 +/- 33 microm. This was highly correlated (Pearson's coefficient = 0.934) with the mean thickness measured by U-PACH (543 +/- 33 microm). The coefficients of variation were good and comparable at 7.9% for U-PACH and 3.5% for OCT. Compared with U-PACH, OCT consistently overestimated the CCT by a mean of 23 microm as shown on Bland-Altman plot.

CONCLUSION

CCT measured by OCT and U-PACH is highly correlated. With appropriate adjustment factor, OCT agrees well with U-PACH and is a reliable alternative for CCT measurement.

Relationship between short wavelength perimetry and central corneal thickness values in ocular hypertensive subjects

PURPOSE

To evaluate the results of short wavelength perimetry (SWAP) of ocular hypertensive (OHT) patients and correlate these findings with central corneal thickness (CCT) measurements.

METHODS

Thirty-seven OHT patients with a mean age of 50.2+/-8.2 (SD) years and 30 control subjects with a mean age of 50.3+/-8.5 (SD) years were included in this study. A questionnaire was applied to patients to evaluate the demographic risk factors that may predict glaucoma development. After a detailed ophthalmologic examination, achromatic and short wavelength perimetries and ultrasonic pachymetry were performed and the results were compared between the two groups with Student t test and Mann-Whitney U test. A p value<0.05 is considered as statistically significant.

RESULTS

Mean CCT was higher in the OHT group (right eye; 558.13+/-28.39 microm and left eye; 558.94+/-27.30 microm) when compared with the control subjects (524.66+/-30.53 microm and 525.86+/-30.46 microm, respectively) (p<0.01). A significant positive correlation was found between CCT measurements and intraocular pressure (r=0.5, p<0.001). Four right eyes (10.8%) and five left eyes (13.5%) of OHT patients had defects in SWAP. OHT patients with SWAP abnormalities had significantly lower CCT measurements in right (527.25+/-17.34 microm) and left eye (528.80+/-13.60 microm) when compared with OHT patients without SWAP defects (561.87+/-27.29 microm and 563.65+/-25.92 microm, respectively) (p<0.05). Significant correlations were found between CCT and SWAP MD, PSD, and CPSD (p<0.05).

CONCLUSIONS

OHT patients with SWAP abnormalities had significantly lower CCT measurements than those without. CCT is considered as a risk factor for the development of glaucomatous damage in OHT patients.

Vergleichende Messung der zentralen Hornhautdicke mit zwei Ultraschallpachymetern

BACKGROUND

The aim of this study was to compare two different ultrasound pachymeters based on measurements of central corneal thickness (CCT).

METHODS

CCT of 1,070 eyes of 535 patients (glaucoma and glaucoma suspects) was determined using the ultrasound pachymeter IOPac (Heidelberg Engineering, Germany) and SP-3000 (Tomey Corporation, Japan). With the IOPac 8 measurements are averaged by the instrument and with the SP-3000 200 measurements, respectively. For statistical purposes intraclass correlation coefficients (ICC) and Bland-Altman analysis were calculated.

RESULTS

The mean CCT was 561.3+/-35.6 microm (IOPac) and 561.8+/-35.6 microm (SP-3000). The mean difference between both pachymeters was 0+/-8 microm. ICC was 0.9746 (95% confidence interval: 0.9714-0.9774).

CONCLUSIONS

The use of the two instruments tested has no influence on the determination of CCT. The measured CCT of glaucoma patients or suspects were slightly above the CCT of normals of other studies.

Changes in Corneal Thickness in Patients With Treated and Untreated Ocular Hypertension

PURPOSE

The elevated intraocular pressure (IOP) in eyes with ocular hypertension is often accompanied by increased corneal thickness. We tested the hypotheses that chronically elevated IOP causes a slow increase in corneal thickness and that lowering the IOP reverses this slow increase.

METHODS

Fifty patients with ocular hypertension were randomized to medication and observation groups in the Mayo Clinic site of the Ocular Hypertension Treatment Study. Central corneal thickness was measured using an optical pachymeter at baseline and annually for 6 years. The rates of change of corneal thickness was compared between the groups. Epithelial thickness was measured by confocal microscopy 8 years after the baseline examination.

RESULTS

Corneal thickness increased 1.5 +/- 3.3 microm/yr in the observation group (n = 23) and decreased -1.3 +/- 2.8 microm/yr in the medication group (n = 27, P = 0.002). Both rates were significantly different from zero (P = 0.04 and P = 0.02, respectively). Epithelial thickness was 46.4 +/- 4.9 microm in the observation group and 41.3 +/- 4.4 microm in the medication group (P = 0.008).

CONCLUSION

Results of this single-center series imply that corneal thickness increases slowly in eyes with ocular hypertension and decreases slowly if the IOP is lowered by topical medications. These phenomena could be explained by a causal relationship between elevated IOP and a slow increase in corneal thickness. A decrease in epithelial thickness accounts for a portion of the thinning that occurs with treatment. If confirmed in a larger series, these findings indicate that the effects of previous treatment on thickness should be considered if corneal thickness is to be used as a discriminant factor in the management of patients with ocular hypertension.

Circadian variations in central corneal thickness and intraocular pressure in patients with glaucoma

AIM

To analyse 24 hour variations in intraocular pressure (IOP) and central corneal thickness (CCT) in a group of glaucomatous patients.

METHODS

30 patients with primary open angle glaucoma were hospitalised and underwent circadian evaluations (at 8 pm, midnight, 4 am, 8 am, noon, and 4 pm) of supine and sitting IOP, respectively, measured using a Perkins and a Goldmann tonometer, and CCT measured using an ultrasonic pachymeter (the mean value of three measurements within 5 mum). All patients were treated with timolol 0.5% twice daily and latanoprost 0.005% once daily.

RESULTS

Mean supine IOP was 15.3 (SD 3.7) mm Hg (range 10-25), with circadian fluctuations of 7.3 (3.3) mm Hg. Mean sitting IOP was 15.1 (3.9) mm Hg (range 8-26), with circadian fluctuations of 5.4 (3.1) mm Hg. Mean CCT was 534 (39) microm (range 443-637 microm) with circadian fluctuations of 16.5 (6.2) microm (range 6-31 microm). Both the within patient and within time point fluctuations in CCT were statistically significant (p<0.0001, ANOVA).

CONCLUSIONS

The authors found considerable fluctuations in 24 hour IOP. The circadian fluctuations in CCT were small and, although statistically significant, did not seem to interfere with the circadian IOP assessment.

Relationship between central corneal thickness and severity of glaucomatous visual field loss in a primary care population

BACKGROUND

Although the ability of central corneal thickness (CCT) to predict development of primary open-angle glaucoma has become increasingly well recognized, the ability of CCT to predict severity of glaucoma remains uncertain. This study was designed to expand the available knowledge about the relationship between CCT and glaucoma severity.

METHODS

Retrospective identification of all patients with a clinical diagnosis of either primary open angle glaucoma (POAG) or ocular hypertension who were seen from September 2002 through May 2003 at the Albuquerque VA Medical Center eye clinic was completed. Eligible subjects were segregated into no, mild, moderate, or advanced visual field loss groups based on Advanced Glaucoma Intervention Study (AGIS) visual field scoring criteria. Following statistical analyses comparing the visual field groups, the sample was divided into thin, intermediate, and thick CCT groups, and further analysis was performed.

RESULTS

Mean CCT was significantly higher in the no field loss group compared with all 3 groups with glaucomatous visual field loss. Mean CCT was not statistically different, however, between the mild, moderate, and advanced visual field loss groups. In linear regression analyses, no significant relationship was found between CCT and severity of visual field loss.

CONCLUSIONS

Although CCT was associated strongly with development of POAG-related visual field loss, CCT was not associated with severity of visual field loss in this study. These findings suggest that glaucoma patients with thinner corneas are just as likely to have advanced levels of field loss as glaucoma patients with thicker corneas. Prospective studies are needed to validate these findings.

Central and paracentral corneal pachymetry in patients with normal tension glaucoma and ocular hypertension

PURPOSE

The difference in central corneal thickness among subgroups of glaucoma patients, as well as its influence on Goldmann applanation tonometry, has been well documented in several clinical trials. In the present study, possible similarities and differences between central corneal thickness and corneal thickness of paracentral quadrants in patients with normal tension glaucoma (NTG) and ocular hypertension (OHT) were investigated.

METHODS

Central and paracentral corneal thickness was measured by optical slit scan pachymetry (Orbscan II). Fourteen patients (28 eyes) with NTG and 11 patients (22 eyes) with OHT were included in this study. t-Test was performed for statistical analysis. To evaluate overall corneal topography, the mean and SD values of the differences between the central corneal thickness and each peripheral quadrant were analysed.

RESULTS

The following data was obtained (microm): (central, upper, temporal, nasal, inferior paracentral quadrant): OHT group 617-695-663-687-660. NTG group 568-629-593-612-616. Corneal thickness of all four paracentral quadrants differed significantly between the OHT and NTG groups. There was a more heterogeneous intraindividual pattern of overall corneal topography in the OHT group, and a more heterogeneous pattern of corneal topography among the individuals of the NTG group (interindividual heterogeneity).

CONCLUSIONS

A comparison of central corneal thickness and paracentral corneal thickness revealed clinically relevant differences between the OHT and NTG groups. The presented data underlines the importance of correlating the site of applanation with the corresponding corneal thickness, especially in OHT patients. It further substantiates the necessity to obtain individual pachymetric data for each NTG patient.

Central corneal thickness and glaucoma in aphakic and pseudophakic children

BACKGROUND

The risk of glaucoma among aphakic children is as high as 32%, based primarily on intraocular pressure (IOP) measurements. Although IOP may be falsely elevated by increased central corneal thickness, central corneal thickness (CCT) values have not been reported in this population.

METHODS

Patients from the practices of 2 pediatric ophthalmologists and 2 glaucoma specialists had measurements of CCT, IOP, and optic nerve cupping, with visual field analysis when possible. Normal fellow eyes of unilateral aphakes and pseudophakes were included as controls.

RESULTS

In 36 aphakic and 6 pseudophakic eyes CCT averaged 660 microns compared with 576 microns for phakic fellow eyes (P < 0.0001). Glaucoma, defined by IOP at least 35 mm Hg or by IOP at least 22 mm Hg associated with optic nerve changes, occurred in 21% of 28 aphakic patients but in no pseudophakic patient.

CONCLUSIONS

CCT in aphakic/pseudophakic children is substantially increased compared with control patients. These values may be important in interpreting IOP measurements in these children.

[The risk of glaucoma and corneal thickness]

Intraocular pressure is still the most important risk factor for the development of glaucomatous optic nerve damage. There is growing evidence that corneal thickness is a risk factor for the development of glaucoma. This might be caused by the effect of corneal thickness on intraocular pressure (IOP) measurements. Goldmann applanation tonometry measurements are correlated with corneal thickness. Thick corneas lead to false high readings whereas thin corneas lead to false low readings. If corneal thickness as a risk factor for glaucoma is only related to the dependency of IOP measurements on corneal thickness or is related to possible different biomechanical tissue properties in glaucomatous eyes is not known. However, a large proportion of the corneal thickness effect seems to be related to the effect on IOP readings by applanation tonometry. Neglecting corneal thickness can lead to false measurements of IOP with consequent misdiagnosis and false treatment. Therefore, measurements of corneal thickness should be performed in glaucoma patients and suspects.

Corneal thickness and functional damage in patients with ocular hypertension

PURPOSE

To correlate functional damage over time detected by standard automated perimetry (SAP) and frequency doubling technology (FDT) with central corneal thickness (CCT) in patients with ocular hypertension (OHT).

METHODS

Seventy-eight OHT patients underwent CCT measurements, SAP, and FDT (the latter two also after 12 and 18 months). Patients were divided into three equally sized groups of 26 patients each: thin (< 540 microm), normal (540-580 microm), and thick cornea (> 580 microm). The frequency of abnormal FDT and SAP results was analyzed over time (Pearson chi2 test).

RESULTS

Six of 26 patients with thin corneas (23.1%) presented an abnormal FDT test at baseline, compared to 1 of 26 (3.8%) in the normal thickness cornea group and 1 of 26 (3.8%) in the thick cornea group. After 12 months, the abnormal FDT tests were as follows, respectively: 9 of 26 (34.6%), 2 of 26 (7.7%), and 2 of 26 (7.7%). For SAP the abnormal results were as follows, respectively: 8 (30.1%), 5 (19.2%), and 2 (7.7%). After 18 months, the abnormal FDT tests were as follows, respectively: 16 (61.5%), 5 (19.2%), and 5 (19.2%). For SAP, the abnormal results were as follows, respectively: 10 (38.5%), 5 (19.2%), and 2 (7.7%).

CONCLUSIONS

OHT patients with thinner corneas have a greater risk of developing functional damage over time.

Comparison of intraocular pressure measured by Pascal dynamic contour tonometry and Goldmann applanation tonometry

AIMS

To compare the intraocular pressure (IOP) measurements obtained using the Pascal dynamic contour tonometer (PDCT) with the standard Goldmann applanation tonometer (GAT) and to correlate these with central corneal thickness (CCT) in patients with normal corneas.

METHODS

A prospective, masked, comparative case series of 116 eyes from patients attending a glaucoma clinic. IOP was measured with PDCT by one examiner and with GAT by a masked, independent examiner. A mean of six CCT readings was used for analysis.

RESULTS

IOP measured by the two instruments correlated significantly (r=0.77; P<0.0001). IOP measured by GAT correlated strongly with CCT (r=0.37, P=0.0001) whereas the relationship between IOP measured by PDCT and CCT approached significance (r=0.17, P=0.073). The differences between GAT and PDCT measured IOP also correlated strongly with CCT (r=0.37, P<0.0001). The 95% limits of agreement between GAT and PDCT were +/-4.2 mmHg. Dividing the eyes into three groups on the basis of CCT, demonstrated those in the thickest tertile showed a poorer agreement between instruments and the GAT measured significantly higher IOP in this group (P=0.003) while the PDCT showed no significant differences with different CCTs (P=0.37).

CONCLUSION

Demonstration of the relative independence of PDCT IOP measurements from CCT supports a potential clinical role for this instrument, particularly for subjects with CCT outside the normal range.

Intraocular Pressure Measurements After Conductive Keratoplasty

PURPOSE

To determine the possible impact of conductive keratoplasty (CK) on intraocular pressure (IOP) measurements.

METHODS

A prospective, single-center, noncomparative interventional case series was performed. Baseline and postoperative IOPs were measured by Goldmann applanation tonometry in 32 eyes of 18 patients who underwent CK for hyperopia correction. Mean follow-up was 11.9 months (range: 8 to 18 months).

RESULTS

After CK, a statistically significant decrease in the measured IOP was observed (before CK: 14.22+/-1.64 vs after CK: 12.66+/-2.21, P<.001). The change in IOP readings postoperatively was not correlated with age, sex, keratometric readings, or attempted correction.

CONCLUSIONS

Despite the limitations due to the small number of patients enrolled in this study, the applanation tonometer appears to underestimate the true IOP after CK.

Central corneal thickness: Will one measurement suffice?

OBJECTIVE

To evaluate the measurement of central corneal thickness (CCT) in a cohort of glaucoma patients over a 3-month period. Measurements were then applied to the criteria described in the Ocular Hypertension Treatment Study (OHTS).

DESIGN

Cohort study.

PARTICIPANTS AND METHODS

Fifty-one patients were recruited from a glaucoma clinic at Moorfields Eye Hospital. Central corneal thickness was measured using an ultrasonic handheld pachymeter by a trained observer. Patients' CCTs were measured at 2 consecutive clinic visits.

MAIN OUTCOME MEASURE

Mean central corneal thickness.

RESULTS

The readings showed clear fluctuation over the 3-month period, with a mean difference in corneal thickness of 9.6+/-26.9 microm in the right eye and 19.0+/-29.2 microm in the left eye. In addition, there was a systematic bias towards increased corneal thickness being recorded at the second reading in both eyes. This reached statistical significance in both the right eye (P = 0.02) and the left eye (P = 0.0003). The criteria used to categorize the risk of patients developing glaucoma in the OHTS were then applied to these results. On the basis of the second reading, 32% of eyes required recategorization in both the right and left eyes.

CONCLUSIONS

Measurements of CCT taken within a clinical setting by a trained observer may show significant variability. For CCT to become a valuable addition to the assessment of glaucoma suspects, more than one reading may be required. Failure to do so may result in misclassification and, thus, an inaccurate assignment of risk.

Central corneal thickness of Caucasians, Chinese, Hispanics, Filipinos, African Americans, and Japanese in a glaucoma clinic

OBJECTIVE

To characterize the central corneal thickness (CCT) of Asian (Chinese, Japanese, and Filipino), Caucasian, Hispanic, and African American patients in a multiethnic glaucoma practice.

DESIGN

Retrospective study (chart review).

PARTICIPANTS

Glaucomatous (n = 600) and nonglaucomatous (n = 201) eyes of 801 patients examined in a San Francisco glaucoma clinic from June 2002 to April 2004 who met inclusion criteria were included in the study. The 6 racial (ethnic) groups represented in the study were Caucasian (n = 186, 23.2%), Chinese (n = 157, 19.6%), Japanese (n = 121, 15.1%), Hispanic (n = 116, 14.5%), Filipino (n = 114, 14.2%), and African American (n = 107, 13.4%).

METHODS

Central corneal thickness was measured by means of ultrasound pachymetry in Asian (Chinese, Japanese, and Filipino), Caucasian, Hispanic, and African American participants with glaucomatous and normal eyes. The relationship between CCT and race was investigated using multivariate regression analyses, controlling for confounders. One eye of each of 801 participants was included for analysis.

MAIN OUTCOME MEASURES

Correlation of mean CCT with race, glaucoma diagnosis, age, spherical equivalent, gender, and history of ocular surgery.

RESULTS

The mean CCT of all participants was 542.9 mum. Central corneal thicknesses of Chinese (555.6 microm), Caucasian (550.4 microm), Filipino (550.6 microm), and Hispanic (548.1 microm) participants did not significantly differ. The CCT of Japanese participants (531.7 microm) was significantly less than that of Caucasians, Chinese, Filipinos, and Hispanics (all, P< or =0.001) and greater than that of African Americans (P = 0.03). African Americans had a CCT (521.0.0 microm) less than that of all races (P< or =0.05). Glaucoma suspects and patients with normal tension glaucoma (NTG), primary open-angle glaucoma (POAG), pseudoexfoliation glaucoma (PEX), and chronic angle-closure glaucoma (CACG) had corneas significantly thinner than those of normal participants (P< or =0.004), whereas ocular hypertensives had significantly thicker corneas (P<0.0001). Among all participants, decreasing values of CCT were significantly related to older age (P<0.01). Less negative or more positive refractive errors, gender, and history of ocular surgery were not associated with changes in CCT (P = 0.38, P = 0.50, and P = 0.97, respectively).

CONCLUSIONS

Studies examining individual Asian subpopulations in isolation suggest that differences in CCT may exist among different Asian groups. The results of this study indicate that CCT does, in fact, vary among Asian subpopulations; Japanese have thinner corneas than Chinese and Filipinos. Caucasians, Chinese, Hispanics, and Filipinos have comparable CCT measurements, whereas the corneas of African Americans are significantly thinner. Additionally, older individuals; glaucoma suspects; and participants with NTG, POAG, PEX, and CACG have thinner corneas. Ocular hypertensives, however, have thicker corneas.

Central corneal thickness and measured IOP response to topical ocular hypotensive medication in the Ocular Hypertension Treatment Study

PURPOSE

To determine whether central corneal thickness (CCT) correlates with measured intraocular pressure (IOP) response to topical ocular hypotensive medication in the Ocular Hypertension Treatment Study (OHTS).

DESIGN

Prospective randomized clinical trial.

METHODS

Intraocular pressure measurements were performed by Goldmann applanation tonometry. Central corneal thickness was measured by ultrasonic pachymetry. The following indicators of IOP response to topical ocular hypotensive medication were examined: (1) IOP after an initial four- to six-week one-eyed therapeutic trial of a nonselective beta-blocker (N = 549) or a prostaglandin analog (N = 201); (2) the mean IOP response during 12 to 60 months of follow-up among medication participants (N = 689); (3) the percentage of follow-up visits at which both eyes met the treatment goal; (4). the total number of different medications prescribed to reach treatment goal; and (5) the total number of different medications prescribed multiplied by the number of months each medication was prescribed.

RESULTS

Central corneal thickness was inversely related to the IOP response after the initial one-eyed therapeutic trial and during 12 to 60 months of follow-up (P < .05). Mean CCT was not correlated with the number of different medications prescribed during follow-up, the total medication-months, or the percentage of visits at which IOP target was met.

CONCLUSIONS

Individuals with thicker corneas had smaller measured IOP responses to ocular hypotensive medication than those with normal or thin corneas. We believe that CCT measurements may be useful in patient management and in interpreting clinical trials of ocular hypotensive medication.

Glaucoma risk factor assessment and prevention: lessons from coronary heart disease

PURPOSE

To determine whether multivariable risk factor assessment can be as successful in developing disease prevention strategies in patients with ocular hypertension as it has been in patients at risk for coronary heart disease (CHD).

DESIGN

From a literature review of the evolution of the global risk assessment model for CHD, parallels are drawn to the evolution of a global risk assessment methodology for glaucoma.

METHODS

This article summarizes the literature on global risk assessment and prevention of CHD in clinical practice, discusses the development of glaucoma risk assessment based on available trial and population data, and reviews the potential for prevention strategies founded on the cardiovascular disease model.

RESULTS

To improve risk assessment in glaucoma and develop disease management strategies for patients with ocular hypertension, it is first necessary to identify and quantify levels of risk associated with factors that predict disease progression. In addition, the incidence of glaucoma and the average person's life expectancy based on his or her age are needed. Finally, it is necessary to quantify how long it takes to develop a visual defect that affects quality of life once a person develops glaucoma.

CONCLUSION

The systematic application of epidemiologic data to CHD risk factor models provides insights into how global risk assessment can be incorporated into treatment recommendations for managing individuals with glaucoma. It is hoped that ophthalmologists can use the results of future clinical trials and long-term studies to develop disease prevention strategies in patients with ocular hypertension based on multivariable risk assessment.