Central corneal endothelial cell density and central corneal thickness in ocular hypertension and primary open-angle glaucoma

The effect of topical bimatoprost on corneal clarity in primary open-angle glaucoma: a longitudinal prospective assessment

PURPOSE

To study the effect of topical bimatoprost on the corneal optical density values using a dual Scheimpflug Placido analysis system.

METHODS

This longitudinal case-control study included 18 patients with newly diagnosed primary open-angle glaucoma who received topical bimatoprost as a first-line treatment and 20 healthy individuals (age and sex-matched controls). Corneal densitometry data were obtained using the dual Scheimpflug analyzer at pre-treatment and 1st, 6th, 12th, 18th months of post-treatment. Repeated measures of ANOVA and Pearson correlation tests were used for statistical analysis.

RESULTS

There were statistically significant differences between pre-treatment and post-treatment 1st and 6th months corneal densitometry values (p < 0.001, p = 0.007, respectively). However, there was no statistically significant difference between the post-treatment 12th and 18th months (p > 0.05). Corneal densitometry values decreased during the 1st month. Intraocular pressure (IOP) differences were statistically significant between baseline and 1 month after treatment (P < 0.001), however not statistically significant between the 1st and 6th, 6th and 12th, 12th and 18th months after treatment (p > 0.05, for all). Corneal densitometry was not correlated with IOP (r = - 0.037, p = 0.44). In the control group, there was no statistically significant difference between baseline and post-baseline 18th-month corneal densitometry measurements (p > 0.05).

CONCLUSIONS

Topical bimatoprost administration might result in a decrease in corneal densitometry measurement. It is of clinical importance that topical bimatoprost administration can affect corneal transparency and cause a possible alteration in corneal properties.

The corneal endothelium: clinical review of endothelial cell health and function

The endothelial cell is a critical structure within the cornea and is responsible for maintaining corneal clarity through its pump function. Endothelial cells are lost over time naturally but can be injured medically, surgically, or as a part of various dystrophies. Monitoring of endothelial cells can be performed clinically or more formally with specular microscopy. In cases of significant compromise, endothelial cells can be transplanted by various endothelial keratoplasty techniques. The future pipeline is bright for possible endothelial cell regeneration and rehabilitation. This article reviews these topics in depth to provide a comprehensive look at the structure and function of the endothelial cell, etiologies of endothelial cell damage, detailed review of iatrogenic causes of endothelial cell loss, and management strategies.

The impact of biomechanics on corneal endothelium tissue engineering

The integrity of innermost layer of the cornea, the corneal endothelium, is key to sustaining corneal transparency. Therefore, disease or injury causing loss or damage to the corneal endothelial cell population may threaten vision. Transplantation of corneal tissue is the standard treatment used to replace malfunctioning corneal endothelial cells. However, this surgery is dependent upon donor tissue, which is limited in supply. Hence, tissue engineers have attempted to construct alternative transplantable tissues or cell therapies to alleviate this problem. Nevertheless, the intrinsic non-dividing nature of corneal endothelial cells continues to foil scientists in their attempts to yield large numbers of cells in the laboratory for use in such novel therapies. Interestingly, the contribution of the biomechanical properties of the underlying extracellular matrix (ECM) on cell division, tissue development and maintenance has been extensively investigated in other many cell types. However, the impact of biomechanics on corneal endothelial cell behaviour is relatively unexplored. Here, we describe contemporary tissue engineering solutions aimed at circumventing donor tissue scarcity. We review the ECM structure and biomechanical features of corneal endothelial cells. We discuss the alterations of ECM in endothelial disease development and progression and point out the role of ECM in developing a tissue-engineered corneal endothelium. We highlight the main biomechanical cues, including topographical and mechanical features, that impact cellular behaviors. Finally, we discuss the influence of biomechanical cues on cell and tissue development, and how corneal endothelial cells response to individual biomechanical stimuli in tissue engineering, which have implications for designing an engineered endothelium and maintaining cell function.

Association Between Anterior Chamber Angle and Corneal Endothelial Cell Density in Chronic Angle Closure

Purpose

To study the association between corneal endothelial cell density (ECD) and degree of anterior chamber angle (ACA) opening in eyes with chronic angle closure glaucoma.

Methods

The study was conducted at JEC Eye Hospitals in Indonesia. Treatment-naïve patients aged ≥40 years with IOP >21 mmHg and peripheral anterior chamber depth (ACD) grade 2 or less by Van Herick's technique were recruited. Trabecular iris angle (TIA; degree) was measured using anterior segment optical coherence tomography (AS-OCT) and classified as: grade 1 ≤10°, grade 2 11-20°, and grade 3 >20°. Noncontact specular microscopy was performed, and the following corneal parameters were obtained:ECD (cells/mm²), coefficient of variation (CV; μm²/cell), percentage of hexagonal cells, and central corneal thickness (CCT; μm).

Results

A total of 52 eyes from 52 subjects were recruited (16 grade 1 TIA, 24 grade 2 TIA, and 12 grade 3 TIA). Presenting IOP was not significantly different between groups. The median central corneal ECD was 2684.5 (1433-2934), 2587.0 (1902-3103), and 2441.0 (1659-3005) cells/mm² in grade 1, 2, and 3 TIA, respectively, with no significant differences across the groups (P = 0.67). The CV was lowest in grade 3 TIA (36.4 ± 7.2 μm2/cell), and highest in grade 1 TIA (38.3 ± 9.6 μm2/cell), but the differences were not significant (P = 0.74). Likewise, the percentage of hexagonality and CCT was not significantly different. TIA was not correlated with IOP but was modestly correlated with age.

Conclusion

The corneal ECD and morphological characteristics such as CV and hexagonality were not significantly different across various TIA grading in chronic angle closure. This may reflect the lack of chronic and gradual IOP insult on corneal endothelial parameters as TIA did not show direct effect towards IOP.

Profile of central corneal thickness and corneal endothelial cell morpho-density of in healthy Congolese eyes

Purpose

To determine the pachymetric and corneal endothelial cell morphometric features and their relationship to ocular and systemic factors in healthy Congolese subjects.

Methods

Non-contact specular microscopy was used in 278 healthy eyes (278 subjects) to measure central corneal thickness (CCT), corneal endothelial cell density (CECD) along with cell size, coefficient of variation (CV) in cell size, and hexagonality (HEX). The lower and upper reference limits and average values for each parameter were determined. Correlation and association of average values with anthropo-demographic and clinical variables were assessed.

Results

The mean age was 38.9 ± 17.2 years (10.9–80.7 years). Average values were 504.2 ± 30.7 μm (CCT), 2907.1 ± 290.9 cells/mm² (CECD), 348.5 ± 38.4 μm² (cell size), 32.9 ± 3.6% (CV), and 51.8 ± 7.2% (HEX). CCT was 504.9 ± 33.6 μm in men and 503.6 ± 28.3 μm in women (p = .73); values for CECD were 2917.1 ± 253.5 cells/mm² and 2899.2 ± 317.8 cells/mm² (p = 0.61), respectively. Lower and upper reference limits were 449.6 μm and 566.0 μm for CCT, and 2165.3 cells/mm² and 3414.4 cells/mm² for CECD, respectively. CCT correlated with body mass index (BMI), (r = − 0.12, P = 0.04). CECD decreased with age (r = − 0.49, P < 0.001), BMI (r = − 0.20, P = 0.001), intraocular pressure (r = − 0.13, P = 0.029) and ocular perfusion pressure (r = − 0.28, P = 0.028). CECD decayed by 8.3 cells/mm² or 0.30% per year of age and CCT decreased by 0.72 μm per kg/m².

Conclusions

Mean central cornea was thinner, CECD higher, and references limits lower than reported in other African populations. The CCT and CECD normative values reported herein will be useful for both clinical and research purposes in this population.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-021-01947-x.

The Effects of Glaucoma and Glaucoma Therapies on Corneal Endothelial Cell Density

A healthy corneal endothelium is required for corneal clarity. Both the glaucoma disease state and its various forms of treatment can have adverse effects on the corneal endothelium. Both the presence of glaucoma and the magnitude of intraocular pressure elevation are related to endothelial cell loss (ECL). Topical medical therapy, laser procedures, and both traditional surgeries-trabeculectomy and tube-shunts-and newer minimally invasive glaucoma surgeries have variable effects on ECL. This review will summarize the reported effects of glaucoma and its treatment on ECL. Concerns for corneal endothelial cell health should be part of the decision-making process when planning glaucoma therapy for lowering intraocular pressure, with added caution in case of planned device implantation in eyes with preexisting ECL and low endothelial cell density at high risk for corneal endothelial decompensation.

Visual acuity, refractive error, and regression outcomes in 169 children with high myopia who were implanted with Ophtec-Artisan or Visian phakic IOLs

PURPOSE

To analyze outcomes in a large cohort of spectacle-aversive children with high myopia who were treated by implantation of the Ophtec-Artisan or Visian phakic intraocular lens (pIOL).

METHODS

Outcome data were collated retrospectively in 78 children (115 eyes) implanted with the Ophtec-Artisan iris-enclaved anterior chamber pIOL and 91 children (154 eyes) implanted with the Visian ICL (intraocular collamer lens) sulcus pIOL. All children had difficulties with spectacle or contact lens wear. Mean age at surgery was 9.9 years; mean follow-up was 3.9 years (range, 0.6-14.1 years).

RESULTS

A total of 248 of 269 eyes (92%) were corrected to within ± 0.5 D of their target value. Spherical correction averaged 12.3 ± 1.0 D. Refractive spherical regression was -0.04 D/year at last follow-up. Uncorrected distance visual acuity improved from an average logMAR 1.8 to 0.4; corrected distance visual acuity improved an average 0.3 logMAR. Of the treated children, 68% had a gain in binocular fusion. Neurobehavioral and/or visuomotor comorbidities were present in 87% of children. Five eyes (2%) developed retinal detachment an average 6 years after implantation. Nine eyes (3%) implanted with the Ophtec-Artisan pIOL required repositioning after trauma.

CONCLUSIONS

Implantation of pIOLs in children is an effective method for correcting high myopia in spectacle noncompliant children. Rates of myopic regression after pIOL surgery are substantially lower than those reported for children treated by excimer laser photorefractive keratectomy (PRK). The prevalence of major complications was relatively low in this high-risk population.

Corneal endothelial cell loss after trabeculectomy and phacoemulsification in one or two steps: a prospective study

Objective

The objective of this study was to analyse the results of the surgical treatment of coexisting cataract and glaucoma and its effects on corneal endothelial cell density (CECD).

Methods

We include two longitudinal prospective studies: one randomised that included 40 eyes with open angle glaucoma that received one- (n = 20) or two-step (n = 20) phacotrabeculectomy and another that included 20 eyes that received phacoemulsification. We assess the impact of surgery on different clinical variables and in particular in CECD using Confoscan 4™ confocal microscopy and semiautomatic counting methods.

Results

Phacoemulsification and phacotrabeculectomy, but not trabeculectomy, increase significantly best-corrected visual acuity and anterior chamber depth and trabeculectomy and one- or two-step phacotrabeculectomy decreased similarly the intraocular pressure. We document percentages of endothelial cell loss of 3.1%, 17.9%, 31.6% and 42.6% after trabeculectomy, phacoemulsification and one- or two-step phacotrabeculectomy, respectively. The coefficient of variation did not increase significantly after surgery but the percentage of hexagonality decreased significantly after phacoemulsification and after two-step phacotrabeculectomy.

Conclusions

Trabeculectomy, phacoemulsification and phacotrabeculectomy are surgical techniques that cause morphological changes and decrease the densities of the corneal endothelial cells. Trabeculectomy produces lesser endothelial cell loss than phacoemulsification, and phacoemulsification lesser cell loss than phacotrabeculectomy. Two-step phacotrabeculectomy (trabeculectomy followed 3 months later by phacoemulsification) causes more cell loss than one-step phacotrabeculectomy, and this could be due to the cumulative effects of two separate surgical traumas or to a negative conditioning lesion effect of the first surgery. For the treatment of coexisting glaucoma and cataract, one-step phacotrabeculectomy is the treatment of choice.

Characteristics of the Corneal Endothelium Across the Primary Angle Closure Disease Spectrum

Purpose

To evaluate the corneal endothelial characteristics across the primary angle closure (PAC) disease spectrum amongst patients diagnosed as PAC suspects (PACS), PAC, PAC glaucoma (PACG), and previous acute PAC (APAC).

Methods

We analyzed a total of 529 subjects (51 PACS, 170 PAC, 234 PACG, and 74 with previous APAC). All subjects had undergone laser peripheral iridotomy prior to study recruitment. Corneal endothelial parameters were measured using a noncontact specular microscope and the following parameters were obtained: mean central endothelial cell density (ECD; cells/mm2), coefficient of variation (CV) in cell area, and percentage of hexagonal cells.

Results

The mean age of the subjects was 65.1 ± 8.2 years, and 55.2% were females. The mean central ECD was 2582.0 ± 472.8 cells/mm2 in PACS, 2566.0 ± 408.3 cells/mm2 in PAC, 2523.8 ± 406.8 cells/mm2 in PACG, and 2504.0 ± 558.1 cells/mm2 in APAC, with no significant differences in ECD across the subgroups (P = 0.61). The CV was lowest in PACS (34.38 ± 6.05 μm2/cell), and highest in APAC (37.61 ± 7.98 μm2/cell), but the differences were not significant (P = 0.07). Likewise, the percentage of hexagonality was not significantly different between the groups. A subgroup analysis on the eyes with previous APAC with their fellow eye also showed no significant differences in the corneal endothelial characteristics.

Conclusions

The corneal ECD and morphological characteristics such as CV and hexagonality are not significantly different across the PAC disease spectrum. This may reflect the lack of a sustained and/or dramatic IOP insult and/or an insignificant deleterious effect from medications, age, and chronicity on corneal endothelial parameters.

A Comparative Study of Central Corneal Epithelial, Stromal, and Total Thickness in Males With and Without Primary Open-Angle Glaucoma

PURPOSE

To compare the central corneal epithelial thickness (CET), stromal thickness (CST), and total thickness (CCT) in males with and without primary open-angle glaucoma and to determine the factors associated with corneal thickness.

METHODS

A case-control study was conducted to evaluate 116 male patients at the Miami Veterans Affair Medical Center. Subjects with available anterior segment optical coherence tomography images (Cirrus HD-OCT, Carl Zeiss Meditec Inc, Dublin, CA) were retrospectively classified into 2 groups by glaucoma status. CET, CST, and CCT measurements between the groups were compared. Associations between thickness and other variables of interest were also evaluated.

RESULTS

The 2 groups were similar with respect to race and ethnicity. Mean age of patients in the glaucoma group (70.3 ± 8.9) was higher than in the nonglaucoma group (66.0 ± 11.7), P < 0.03. Individuals who self-identified as black had lower CST (447.8 ± 29.0 μm) and CCT (503.0 ± 30.5 μm) compared with whites (CST: 470.0 ± 31.7 μm; CCT: 525.1 ± 32.4 μm), P = 0.0001 and P = 0.0002, respectively. In a similar manner, individuals with glaucoma had lower CST (453.4 ± 32.5 μm) and CCT (507.3 ± 33.8 μm) than that of those without glaucoma (CST: 465.2 ± 31.2 μm; CCT: 521.5 ± 31.5 μm), P = 0.05 and P = 0.02, respectively. CET, CST, and CCT were negatively correlated with the number of antiglaucoma medications (r = -0.2, r = -0.22, and r = -0.25, respectively), P = 0.05 for all.

CONCLUSIONS

Individuals with glaucoma have lower CST and CCT measurements compared with individuals without glaucoma. An increased number of glaucoma medications were associated with lower thickness measurements.

Acute ocular hypertension disrupts barrier integrity and pump function in rat corneal endothelial cells

Acute ocular hypertension (AOH) frequently compromises corneal endothelial cell (CEC) function in clinical practice. This type of stress induces corneal oedema and a decrease in the corneal endothelial cell density (ECD). The anterior chamber of the right eye of Sprague-Dawley rats was irrigated with Balanced Salt Solution (BSS) for two hours, and the left eye served as a control to determine the time-dependent effects of AOH on endothelial cell morphology and function. The average intraocular pressure (IOP) increased to 82.6 ± 2.3 mmHg (normal range: 10.2 ± 0.4 mmHg) during anterior irrigation. Very soon after initiating irrigation, corneal oedema became evident and the cornea exhibited a significant increase in permeability to FITC-dextran. The peripheral ECD was significantly reduced, and the morphology of CECs became irregular and multiform. The structures of the zonula occludens-1 (ZO-1) and F-actin were severely disrupted. In addtion, Na,K-ATPase exhibited a dispersed expression pattern. Two days after irrigation, obvious CEC proliferation was observed, the ECD recovered to a normal level, and F-actin was dispersed throughout the cytoplasm. Seven days later, the CEC structure and function were nearly normalized. Based on the results obtained using this model, an acute IOP crisis exerts transient deleterious effects on CEC structure and function in rats.

Phakic Intraocular Collamer Lens (Visian ICL) Implantation for Correction of Myopia in Spectacle-Aversive Special Needs Children

PURPOSE

A subset of children with high anisometropia or isoametropia and neurobehavioral disorders have chronic difficulties with spectacle or contact lens wear. We report the results of refractive surgery in a series of these children treated using bilateral or unilateral intraocular collamer lens (Visian ICL) implantation for moderate to high myopia.

DESIGN

Prospective nonrandomized cohort study.

METHODS

Clinical course and outcome data were collated prospectively for 40 implanted eyes in 23 children (mean age 10.2 ± 5.3 years, range, 1.8-17 years). Myopia ranged from -3.0 to -14.5 diopters (D), mean -9.2 ± 3.5 D. Goal refraction was plano to +1 D. Correction was achieved by sulcus implantation of a Visian ICL (STAAR Surgical, Monrovia, California, USA) under general anesthesia. Mean follow-up was 15.1 months (range, 6-22 months).

RESULTS

Thirty-five eyes (88%) were corrected to within ±1.0 D of goal refraction; the other 5 (12%) were corrected to within 1.5 D. Uncorrected distance visual acuity improved substantially in all eyes (from mean 20/1050 [logMAR 1.72] to mean 20/42 [logMAR 0.48]). Spherical regression at last follow-up was an average of +0.59 D. Visuomotor comorbidities (eg, amblyopia, nystagmus, foveopathy, optic neuropathy) accounted for residual postoperative subnormal visual acuity. Thirteen of the 23 children (57%) had a neurobehavioral disorder (eg, developmental delay/intellectual disability/mental retardation, Down syndrome, cerebral palsy, autism spectrum disorder). Eighty-five percent (11/13) of those children were reported to have enhanced visual awareness, attentiveness, or social interactions. Endothelial cell density was measureable in 6 cooperative children (10 eyes), showing an average 1% decline. Central corneal thickness, measured in all children, increased an average of 8 μm. Two children (8%) required unplanned return to the operating room on the first postoperative day to alleviate pupillary block caused by a nonpatent iridotomy. No other complications were encounterd.

CONCLUSION

Visian ICL implantation improves visual function in special needs children who have moderate to high myopia and difficulties wearing glasses or contact lenses.

Changes in Corneal Endothelial Cell after Ahmed Glaucoma Valve Implantation and Trabeculectomy: 1-Year Follow-up

Purpose

To compare changes in corneal endothelial cell density (CECD) after Ahmed glaucoma valve (AGV) implantation and trabeculectomy.

Methods

Changes in corneal endothelium in patients that underwent AGV implantation or trabeculectomy were prospectively evaluated. Corneal specular microscopy was performed at the central cornea using a non-contact specular microscope before surgery and 6 months and 12 months after surgery. The CECD, hexagonality of the endothelial cells, and the coefficient of variation of the cell areas were compared between the two groups.

Results

Forty eyes of 40 patients with AGV implantation and 28 eyes of 28 patients with trabeculectomy were studied. Intraocular pressure in the AGV implantation group was significantly higher than that in the trabeculectomy group (p < 0.001), but there was no significant difference in other clinical variables between the two groups. In the AGV implantation group, the mean CECD significantly decreased by 9.4% at 6 months and 12.3% at 12 months compared with baseline values (both, p < 0.001), while it decreased by 1.9% at 6 months and 3.2% at 12 months in the trabeculectomy group (p = 0.027 and p = 0.015, respectively). The changes at 6 months and 12 months in the AGV implantation group were significantly higher than those in the trabeculectomy group (p = 0.030 and p = 0.027, respectively). In the AGV implantation group, there was a significant decrease in the CECD between baseline and 6 months and between 6 months and 12 months (p < 0.001 and p = 0.005, respectively). However, in the trabeculectomy group, a significant decrease was observed only between baseline and 6 months (p = 0.027).

Conclusions

Both the AGV implantation group and the trabeculectomy group showed statistically significant decreases in the CECD 1 year after surgery. The decrease in CECD in the AVG implantation group was greater and persisted longer than that in the trabeculectomy group.

Effect of Mitomycin-C Augmented Trabeculectomy on Corneal Endothelial Cells

Purpose:

To evaluate the effect of mitomycin-C (MMC) on corneal endothelial cell density (ECD) and morphology after trabeculectomy.

Methods:

In this prospective comparative case series, 31 eyes with glaucoma underwent trabeculectomy with (group I), or without (group II) MMC. Specular microscopy was performed pre-, and postoperatively at months 1 and 3. Outcome measures included central corneal endothelial cell count and coefficient of variation (CV) of cell size.

Results:

Overall, mean preoperative ECD was 2,135.8 ± 397.6 cells/mm²; corresponding values at postoperative months 1 and 3 were 2,019.6 ± 447.2 cells/mm², and 1,991.4 ± 425.5 cells/mm², respectively (P > 0.05). Cell loss from month 1 to 3 was 1.3 % (P > 0.05). Subgroup analysis showed significant differences in endothelial cell loss at month 1 (P = 0.048) and month 3 (P = 0.014) between the MMC and control groups with no significant difference between the two groups in terms of cell loss from months 1 to 3, postoperatively (P = 0.968). Overall, mean pre-and postoperative CVs at months 1 and 3 were 27.38 ± 4.55, 27.96 ± 4.26, and 28.35 ± 4.47, respectively, with no significant difference between the two groups (P > 0.05). There was no correlation between preoperative central endothelial cell density (CECD) and MMC related cell loss.

Conclusion:

MMC application in trabeculectomy seems to cause a small but significant corneal endothelial loss. Most of the damage occurs intraoperatively, or in the early postoperative period, however progressive endothelial cell loss is not a major concern.

Evaluation of corneal endothelium in adolescents with juvenile glaucoma

Purpose. To evaluate the endothelial cell density (ECD) and central corneal thickness (CCT) in adolescents with juvenile open-angle glaucoma (JOAG) and ocular hypertension (OH) and to investigate the influence of topical antiglaucoma medications on ECD and CCT in adolescents with JOAG. Methods. ECD and CCT were investigated in 66 eyes of 33 adolescents with JOAG. Depending on the topical treatment the eyes were classified into 4 groups: (1) topical carbonic anhydrase inhibitor, (2) prostaglandin analogs, (3) beta-blocker, and (4) CAI-beta-blocker combination. ECD and CCT were also checked in 24 adolescents with OH and in control group (33 persons). Results. ECD was significantly lower in eyes with JOAG (2639.5 cells/mm²) compared with ECD in eyes with OH (2924.5 cells/mm²) and in control group (2955.5 cells/mm²). CCT was 0.554 mm in eyes with JOAG, 0.55 mm in eyes with OH, and 0.544 mm in control group. ECD in patients with JOAG was 2730 cells/mm² (1 group), 2773.5 cells/mm² (2 group), 2539.5 cells/mm² (3 group), and 2551 cells/mm² (4 group). CCT was 0.556 mm in 1 group, 0.558 mm in 2 group, 0.532 mm in 3 group, and 0.544 mm in 4 group. Conclusions. Our findings indicate that JOAG and OH did not affect CCT, but JOAG has influence on ECD in adolescents. There were no significant differences between ECD and CCT of eyes treated with different kinds of antiglaucoma medications.

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.

Age-related changes in central corneal thickness in normal eyes among the adult Lithuanian population

Background

The purpose of this study was to estimate mean central corneal thickness (CCT) and determine whether there are any correlations between CCT, age, and sex in the adult Lithuanian population.

Methods

A total of 1,650 Caucasians of Lithuanian origin (aged 18–89 years) comprising 688 (41.7%) men and 962 (58.3%) women were examined. Subjects were stratified by age into seven groups. CCT was measured using ultrasonic pachymetry. Correlations between CCT, age, and sex were sought.

Results

Mean (± standard deviation) CCT for both eyes was 544.6±30.5 μm. Mean CCT was 545.2±30.5 μm in the left eye and 544.6±30.5 μm in the right eye, and was 545.0±25.6 μm in men and 544.4±33.5 μm in women. Mean CCT was 550.8±35.7 μm in subjects aged 18–29 years, 557.5±27.6 μm in those aged 30–39 years, 551.3±31.4 μm in those aged 50–59 years, 544.0±31.4 μm in those aged 50–59 years, 544.2±31.6 μm in those aged 60–79 years, 535.1±27.8 μm in those aged 70–79 years, and 530.1±16.8 μm in those aged 80–89 years. No statistically significant difference in CCT was found between the sexes (P>0.05). However, there was a significant difference in subjects aged 18–29 years; men had higher CCT than women (P<0.05). A statistically significant negative correlation was found between CCT and age (r=-0.263, P<0.05) that was stronger in men (r=-0.406, P<0.05) than in women (r=-0.118, P<0.05).

Conclusion

The mean CCT in adult Lithuanians was 544.6±30.5 μm, of the left eye 545.2±30.5 μm and of the right – 544.6±30.5 μm. CCT of the right eye was equal to the CCT of both eyes. Mean CCT was 545.0±25.6 μm in men and 544.4±33.5 μm in women. Young men tended to have higher CCT than women. CCT decreases over the lifetime, meaning that older people have thinner corneas. CCT’s dependence on age is stronger in men.

Central corneal thickness in southern Egypt

The study aimed to determine mean central corneal thickness (CCT) in a southern Egyptian population according to gender and age using ultrasonic pachymetry and to compare these CCT measurements to different populations. A prospective, observational, consecutive case series of 4,368 non-glaucomatous subjects (emmetropes and myopes) aged 16-70 years was carried out from August 2010 to March 2013 at the outpatient ophthalmology clinic in Sohag University Hospital and the Laser Vision Center in Sohag City, Egypt. Refraction, keratometry, slit-lamp examination, and intraocular pressure (IOP) measurements were obtained for all subjects. CCT was measured by ultrasonic pachymetry. The average CCT was 530.06 ± 38.03 μm. Average CCT was 532.6 ± 33.3 μm in emmetropes, 531.5 ± 31.3 μm in myopes <6 diopters (D), 531.1 ± 31.4 μm in myopes >6 D and 533 ± 33 μm in hyperopes, with no statistically significant difference between the groups. There was a statistically significant difference in CCT between age groups and gender. There was a strong correlation between CCT and IOP among the non-glaucomatous population. CCT was found to be lower in Egyptians than in Caucasian, Hispanic, and Japanese populations but comparable to African and African American populations.

Corneal endothelial cells 6-7 years following cataract surgery in patients with pseudoexfoliation syndrome

PURPOSE

To assess the condition of the corneal endothelium an extended period after cataract surgery in eyes with and without pseudoexfoliation syndrome (PES).

METHODS

Forty-six patients with PES who underwent cataract surgery in the Eye Department, Oslo University Hospital, in 2001 and 2002 were enrolled and compared to 101 matched controls without PES who had surgery in the same period. They were re-examined 6-7 years following surgery with measurements taken of corneal endothelial cell density (ECD), pleomorphism, polymegathism and corneal thickness.

RESULTS

Mean ECD was 2024 ± 371 cells/mm(2) in eyes with PES and 2144 ± 365 cells/mm(2) in eyes without PES. The difference was not statistically significant. No significant difference in polymegathism and pleomorphism was noted. Mean corneal thickness was 543 and 547 μm in eyes with and without PES, respectively (not statistically significant). The presence of glaucoma in pseudoexfoliative eyes was not associated with endothelial cell changes.

CONCLUSION

Six to 7 years following cataract surgery, no statistically significant differences were established in ECD, pleomorphism, polymegathism and corneal thickness in eyes with and without PES. No clinical signs of corneal decompensation were noted amongst the participants.

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 and intraocular pressure in the Cameroonian nonglaucomatous population

Aim:

We performed a prospective, analytical study from 01 January to 31 March 2009 in the Ophthalmology Unit of the Gyneco-Obstetric and Pediatric Hospital of Yaounde, aiming to determine the profile of central corneal thickness (CCT) in the Cameroonian nonglaucomatous black population and its relationship with intraocular pressure (IOP).

Results and discussion:

Four hundred and eighty-five patients (970 eyes) meeting our inclusion criteria were selected for this study. The average CCT was 529.29 ± 35.9 μm in the right eye (95% confidence interval [CI]: 526.09–532.49), 528.19 ± 35.9 μm in the left eye (95% CI: 524.99–531.40) and 528.74 ± 35.89 μm in both eyes (95% CI: 526.48–531.00), range 440 to 670 μm. The average IOP was 13.01 ± 2.97 mmHg in both eyes (95% CI: 12.82–13.19). A rise in CCT by 100 μm was followed by an increase in IOP of about 2.8 mmHg (95% CI: 2.3–3.6) for both eyes taken together. Linear regression analysis showed that corneal thickness was negatively correlated with age and IOP was positively related with age.

Conclusion:

CCT in the Cameroonian nonglaucomatous black population was found to be lower compared with CCT values in Caucasian and Asian populations. On the basis of reference values ranging between 527 and 560 μm, an adjustment of IOP values by a correction factor is required for many Cameroonian patients. This will improve the diagnosis and follow-up of glaucoma by helping to detect true ocular hypertension.

Changes in corneal endothelial cell density in patients with normal-tension glaucoma

PURPOSE

To study the changes in corneal endothelial cell density in eyes with normal-tension glaucoma compared with those in controls.

METHODS

A total of 227 subjects in three groups, one each of normal-tension glaucoma and primary open-angle glaucoma patients and one of normal controls, were studied from January 2008 to July 2008 in the Ophthalmology Department of Kangbuk Samsung Hospital. The glaucoma (normal-tension glaucoma and primary open-angle glaucoma) patients included monocular and binocular glaucoma patients. Corneal endothelial cells were examined using a noncontact specular microscope.

RESULTS

The mean endothelial cell densities in the three groups were as follows: normal-tension glaucoma group, 2696.7+/-303.9 cell/mm2; primary open-angle glaucoma group, 2370.5+/-392.3 cell/mm2; and normal group, 2723.6+/-300.6 cell/mm2. The endothelial cell count was not significantly different between normal-tension glaucoma and normal groups (P=1.000). Primary open-angle glaucoma patients had significantly lower endothelial cell counts (P<0.001) than the normal group. The endothelial cell count was also significantly lower in eyes with primary open-angle glaucoma than in normal-tension glaucoma eyes (P<0.001).

CONCLUSIONS

There was a significant decrease in corneal endothelial cell density in eyes with primary open-angle glaucoma, but not in eyes with normal-tension glaucoma. Elevated intraocular pressure likely affected the decrease of corneal endothelial cell density in eyes with glaucoma.

Phakic intraocular lens correction of high ametropia in children with neurobehavioral disorders

PURPOSE

A subset of children with high ametropia and neurobehavioral disorders have chronic difficulties with spectacle or contact lens wear. We report the results of refractive surgery in a series of these children treated using bilateral or unilateral phakic intraocular lenses (IOLs) for ametropia >10 D.

METHODS

Clinical course and outcome data were collated prospectively in a group of 12 children (mean age, 10.1 years; range, 4-17 years) with neurobehavioral disorders exacerbated by poor compliance with spectacles. Myopia in 18 eyes ranged from -10.0 to -22.75 D (mean, -15.2 D) and in 2 hyperopic eyes from +10.25 to +10.75 (mean, +10.5 D). Goal refraction was approximately 0 to +1 D. Correction was achieved by implantation of an iris-enclaved phakic IOL under general anesthesia. Mean follow-up was 9.1 months (range, 3-15 months).

RESULTS

Myopia correction averaged 14.5 D and hyperopia correction 9.4 D. Eighty-six percent of eyes (17/20 eyes) were corrected to within +/- 1 D of emmetropia and the remaining 14% (3 eyes) to within +/- 2 D. Uncorrected visual acuity improved substantially in all 20 eyes (60-fold; from a mean of 20/3400 to a mean of 20/57). Ocular comorbidities in each child accounted for residual postoperative, subnormal visual acuity (eg, amblyopia, nystagmus, albinism, regressed retinopathy of prematurity). Visual functions (measured using a 23-item validated survey) improved. One eye required IOL exchange; no other clinically significant complications have been encountered.

CONCLUSIONS

Phakic IOL implantation improves visual function substantially in neurobehaviorally impaired children who have high ametropia and difficulties wearing glasses.

Changes in corneal endothelial cell density and morphology after Ahmed glaucoma valve implantation during the first year of follow up

PURPOSE

To determine the effect of Ahmed glaucoma valve (AGV) implantation on corneal endothelial cells.

METHODS

Ahmed glaucoma valves were implanted in 30 eyes of 30 patients with refractory glaucoma. Corneal endothelial cell density and shape was prospectively evaluated in both the subject and fellow eyes of each patient. Corneal specular microscopy was performed on the superior, superotemporal, superonasal and central corneal areas before and at 1, 6 and 12 months after surgery.

RESULTS

A statistically significant decrease in average corneal endothelial cell density was observed 12 months postoperatively in the subject eyes compared with the baseline value (P = 0.001). No such changes were observed in the fellow eyes during follow-up period. The mean percentage decrease in corneal endothelial cell density in subject eyes was 3.5% at 1 month, 7.6% at 6 months and 10.5% at 12 months after surgery. The superotemporal area, which was closest to the tube, showed the greatest decrease in endothelial cell density at 1 year after surgery, while the central cornea showed the least decrease. In terms of endothelial cell morphology, polymegathism and pleomorphism increased in the early postoperative periods, and then gradually approached the preoperative status by 6 months after surgery.

CONCLUSION

Corneal endothelial cell density progressively decreased after AGV implantation. These findings indicate that particular care should be taken during intraoperative and postoperative management of AGV implantation patients in order to minimize damage to the endothelium.

Identifying relationships between tomography-derived corneal thickness, curvature, and diameter and in vivo confocal microscopic assessment of the endothelium in healthy corneas of young adults

PURPOSE

Despite the importance of a healthy endothelial layer in anterior segment surgery, the possible influence of corneal parameters on endothelial cell density (ECD) has largely been ignored in the young adult eye. This study investigated the possible associations between corneal tomographic parameters and ECD values in young adults.

METHODS

Subjects aged 21-30 years, with normal corneas were recruited. Mean ECD, mean cell area (MCA), coefficient of variation for cell area (COVA), and proportion of hexagonal cells were derived by in vivo confocal microscopy. The Orbscan II system was used to measure corneal parameters including: thickness, horizontal corneal diameter, corneal curvature, anterior and posterior elevation, and eccentricity.

RESULTS

Sixty-two subjects (42 female, 20 male) were included (mean age 25+/-3 years). Overall mean ECD was 3169+/-309 cells/mm(2) with no differences between genders. Mean percentage of hexagonality was 53+/-5%, male subjects (55%) had a higher percentage of hexagonal cells than female subjects (51%) (P=0.02). Central corneal thickness (CCT) was 529+/-43 microm. Central ECD was significantly correlated with CCT (Pearson's r=0.26, P=0.04). However, horizontal corneal diameter (r=0.19, P=0.14), anterior corneal curvature (r=-0.07, P=0.6), and posterior corneal curvature (r=-0.07, P=0.6) were not correlated with ECD or percentage of hexagonality. There was no statistically significant association between anterior chamber depth (3.6+/-0.3 mm) and ECD (r=0.15, P=0.3).

CONCLUSION

Corneal thickness is related to ECD in normal young adult eye, with lower ECD values identified in thinner corneas; however, corneal diameter and corneal curvature do not have a significant correlation with ECD.

Corneal endothelial cell changes after trabeculectomy and deep sclerectomy

PURPOSE

To compare the effect of trabeculectomy and deep sclerectomy on the corneal endothelium.

METHODS

This prospective comparative study investigated 62 eyes of 62 patients scheduled for a single trabeculectomy (n=18), a single deep sclerectomy (n=14), a combined trabeculectomy and phacoemulsification (n=11), or a combined deep sclerectomy and phacoemulsification (n=19). Exclusion criteria were history of corneal disease, ocular trauma, inflammation, or previous glaucoma or cataract surgery. Preoperative, 3-month and 1-year postoperative noncontact specular microscopies were performed on central and superior corneas. Endothelial cells were counted with a computer-assisted analyzer.

RESULTS

In central cornea, a statistically significant postoperative endothelial cell loss was found after trabeculectomy and deep sclerectomy (alone and combined with cataract extraction) at 3 and 12 months. Cell loss was 7% after penetrating surgery and 2.6% after nonpenetrating surgery (noncombined surgeries). This difference in cell loss was statistically significant. Cell loss increased significantly over the course of the study at 12 months (9.6% and 4.5%, respectively). Cell loss was also significantly higher after trabeculectomy than sclerectomy in upper cornea only in noncombined surgeries. No statistically significant difference in coefficient of variation of cell size (CV) and percentage of cell hexagonality (Hex %) was noted.

CONCLUSIONS

Endothelial cell loss was moderate 3 and 12 months after glaucoma surgery. However, it was greater after trabeculectomy, suggesting less corneal damage after deep sclerectomy. This observation deserves further clinical study.

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.

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

AIMS

To determine if central corneal thickness (CCT) changes over time and if this change relates to glaucoma progression.

METHODS

39 patients (64 eyes) with open angle glaucoma, ocular hypertension, glaucoma suspect status, or a normal eye examination were examined at two visits. CCT, age, race, sex, family history of glaucoma, presence of diabetes and systemic hypertension, diagnosis, visual acuity, spherical equivalent, intraocular pressure, vertical and horizontal cup to disc ratios, number of glaucoma medications prescribed, Advanced Glaucoma Intervention Study (AGIS) score and mean deviation of Humphrey visual fields, and interventions required were recorded. Statistical analysis used the Wilcoxon signed ranks test, linear regression, and analysis of variance.

RESULTS

Between the two visits (mean 8.2 years apart), mean CCT decreased by 17 mum in right eyes (p<0.002) and by 23 mum in left eyes (p<0.001). This decrease was greater in right eyes of patients with primary open angle glaucoma than in normals (p = 0.041). There was no significant association between change in CCT and other examination parameters. Change in CCT was not associated with topical carbonic anhydrase inhibitor use.

CONCLUSION

In this longitudinal study, CCT decreased over time, but this may not be related to glaucoma progression.

Effect of Shear Stress on Attachment of Corneal Endothelial Cells in Association With Corneal Endothelial Cell Loss After Laser Iridotomy

PURPOSE

Laser iridotomy often causes bullous keratopathy; however, the mechanism is unclear. We investigated whether changes in aqueous humor hydrodynamics after laser iridotomy have any role in corneal endothelial cell loss.

MATERIALS AND METHODS

Porcine corneal endothelial cells were plated onto glass slides. Following 1 or 3 hours for adhesion, the endothelial cells were exposed to shear stresses (0.1-10 dyne/cm) for 15 minutes, and the number of detached cells was counted. In addition, the pressure and shear stress on corneal endothelial layer were calculated in a virtual model of laser iridotomy.

RESULTS

The number of detached corneal endothelial cells increased with shear stresses in a dose-dependent manner. Significant increase of rate of detached corneal endothelial cells was observed at >0.3 dyne/cm after 1-hour attachment and at 1 dyne/cm after 3-hour attachment. The maximum pressure on corneal endothelial layer was 0.007 mm Hg, which is negligible compared with intraocular pressure. However, the maximum shear stress on the corneal endothelial layer could be> dyne/cm in some conditions of laser iridotomy.

CONCLUSIONS

The resistance of corneal endothelial cell loss to shear stress is time dependent. Shear stress could be a cause of corneal endothelial cell loss in some conditions of laser iridotomy.

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.

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.

Clinical responses of the corneal endothelium

The corneal endothelium maintains corneal deturgescence and clarity by a pump-leak mechanism first described by David Maurice. This cell layer can be investigated clinically with specular microscopy, fluorophotometry, and pachymetry. We describe the clinical responses of the corneal endothelium to aging, drugs, glaucoma, contact lens wear, trauma, disease, and surgery.

The effects of corneal parameters on the assessment of endothelial cell density in the elderly eye

BACKGROUND

The possible impact of corneal thickness, curvature, and size on the measurement of endothelial cell density (ECD) has largely been ignored in the normal eye. The aim of this study was to investigate the possible impact of the main corneal parameters on the analysis of ECD values at the central, superior, and temporal parts of the corneal surface.

METHODS

All 75 participants (52 females, 23 males) were assessed as part of a pre-cataract surgery investigation. The mean age was 75.7 (SD 10.9) years. Confocal microscopy was used to measure ECD and the percentage of six sided cells at the central, superior, and temporal parts of the cornea. The Orbscan II topography system was used to measure corneal thickness, topography, and horizontal corneal diameter.

RESULTS

The mean central ECD measured was 2488 (SD 301) cells/mm(2), compared with 2525 (SD 505) cells/mm(2) in the temporal cornea and 2639 (SD 398) cells/mm(2) in the superior cornea. The regional differences in ECD were not significant (p>0.14). The central ECD was significantly correlated to the central (mean 0.593 (SD 0.039) mm, p = 0.021) as well as the temporal (0.628 (SD 0.039) mm, p<0.001) and the superior corneal thickness (SD 0.644 (SD 0.048) mm, p = 0.018). The mean corneal curvature at the centre (7.7 (SD 0.34) mm, p = 0.002) as well as 3 and 5 mm from the apex was significantly related to ECD (p = 0.008 and p = 0.009, respectively).

CONCLUSIONS

The study suggests that in an older population, lower ECD values would be expected in thinner and/or steeper corneas.

Penetrating keratoplasty for endothelial decompensation in eyes with buphthalmos

PURPOSE

To evaluate the prognosis and complications of penetrating keratoplasty (PKP) for corneal decompensation in eyes with buphthalmos and to analyze the risk factors for graft failure.

PATIENTS AND METHODS

Clinical records of 13 adult and three pediatric patients who underwent PKP for endothelial decompensation with a previous diagnosis of congenital glaucoma of a total of 3,663 corneal transplantations performed in our department between January 1987 and December 2001 were reviewed retrospectively. During the study period, a total of 33 PKPs was performed in 20 eyes with buphthalmos. The median age of the patients at the time of PKP was 39 years (range, 3 to 72). All patients had a history of intraocular surgery, including multiple glaucoma surgeries, cataract extraction, and PKP. The impact of pre-, intra-, and postoperative factors on graft failure and duration of graft clarity was analyzed.

RESULTS

Fifty-five percent (11/20) of the eyes received only one graft, 25% (5/20) received two, and 20% (4/20) received three grafts. During a mean follow-up of 87.2 months (range, 4.5-72), graft failure occurred in 18 of 33 grafts (54%). Seven (7/18, 39%) had immunologic graft rejection, and 11 (11/18, 61%) had nonimmunologic graft failure. At the end of the follow-up, 75% (15/20) of the eyes had clear grafts. Duration of graft clarity was found to be significantly shorter in regrafts compared with that of primary grafts (27.0 +/- 27.7 versus 56.4 +/- 41.0 months, p= 0.02). After PKP, intraocular pressure (IOP) was uncontrolled in 12 (12/33, 36%) grafts. Nine of 20 eyes (45%) required an average of 3.2 cyclodestructive procedures per eye for pharmacologically resistant elevated IOP. The final postoperative vision improved in 70% (14/20) of the eyes and the best visual acuity postoperatively (75% > or =20/400) was significantly better than the preoperative visual acuity (25% > or =20/400, p= 0.0001).

CONCLUSIONS

Endothelial decompensation due to congenital glaucoma is a very rare indication for PKP. The incidence of graft failure is high, and nonimmunologic reasons are the leading causes of graft failure in this high-risk population. Visual acuity can be significantly improved but is usually still very limited by advanced glaucomatous optic nerve damage and amblyopia. Efficient control of IOP before and after PKP is mandatory in eyes with buphthalmos to avoid graft failure and progress of glaucomatous optic nerve atrophy.

Accelerated chronic endothelial cell loss after penetrating keratoplasty in glaucoma eyes

PURPOSE

Accelerated chronic endothelial cell loss may be the main reason for limited prognosis of penetrating corneal grafts in glaucoma eyes. This hypothesis, however, has not yet been proven and is examined in this article.

METHODS

Three groups of normal-risk keratoplasty patients were followed up prospectively. Group I consisted of 172 patients (without glaucoma history and without postoperative increase in intraocular pressure), group II comprised 15 patients (with glaucoma history, but without postoperative increase in intraocular pressure), and group III consisted of seven patients (with glaucoma history and with postoperative increase in intraocular pressure). Immune reactions in the postoperative course were an exclusion criterion. Follow-up periods averaged 2.7 +/- 1.7 years (group I), 2.8 +/- 1.7 years (group II), and 2.6 +/- 2.0 years (group III). Only patients with at least three postoperative endothelial cell density values were included in the study. Loss of endothelial cells. mm-2. d-1 was derived from the postoperative endothelial values of each patient by calculating the slope of the regression line for each scatterplot of endothelial cell density values plotted against time.

RESULTS

During the follow-up period 0.82 +/- 0.97 cells. mm-2. d-1 were lost in group I, 1.01 +/- 1.04 cells. mm-2. d-1 were lost in group II, 2.67 +/- 2.16 cells. mm-2. d-1 were lost in group III (ANOVA and Gabriel post-hoc test: I/II P = 0.82, I/III P < 0.001, II/III P = 0.004).

CONCLUSIONS

Postoperative increase in intraocular pressure may be a possible cause for accelerated endothelial cell loss in glaucoma eyes, but this result is tentative because of the small number of patients included in the two glaucoma groups. Confirmation by long-term observation of larger patients groups is desirable. The result implies good control of intraocular pressure after penetrating keratoplasty. Whether this method is the correct means by which to prevent accelerated endothelial cell loss in such eyes must be shown in future studies.

Corneal disease in patients with chronic renal insufficiency undergoing hemodialysis

PURPOSE

To evaluate alterations of the corneal endothelium in patients undergoing hemodialysis for renal insufficiency.

METHODS

Sixty-six patients undergoing hemodialysis received a complete ophthalmologic examination. The state of the endothelium was assessed using pachymetry and specular microscopy. The group of patients undergoing dialysis was divided according to the time of dialysis, aluminum, product of calcium and phosphate in blood, and parathyroid hormone to analyze the influence of these factors. The possible presence of iron and aluminum in the aqueous humor of patients who underwent and those who did not undergo hemodialysis was also estimated.

RESULTS

Patients undergoing hemodialysis did not have significant corneal edema. Cell density was significantly lower in patients undergoing dialysis than in patients not undergoing dialysis; this reduction appeared to be associated with length of dialysis and was unrelated to serum aluminum and calcium levels. Patients undergoing dialysis did not have cell polymorphism or polymegethism, although there was a tendency toward increased polymegethism with length of dialysis. Aluminum and iron were not increased in the aqueous humor of patients undergoing dialysis.

CONCLUSIONS

The alteration of the endothelium that we found is not related to the elements studied. It is possibly the result of another product dissolved in the anterior chamber or to the alterations of the anterior segment that these patients are known to have.

Corneal thickness and endothelial density before and after cataract surgery

BACKGROUND/AIMS

Deturgescence of the corneal stroma is controlled by the pumping action of the endothelial layer and can be monitored by measurement of central corneal thickness (pachymetry). Loss or damage of endothelial cells leads to an increase in corneal thickness, which may ultimately induce corneal decompensation and loss of vision. Little is known about the effect of moderate reductions in endothelial cell number on the thickness of the corneal stroma. This study aimed to investigate this matter further using patients who had incurred moderate decreases in their endothelial cell counts as a result of cataract surgery.

METHODS

Central corneal thickness was measured 1 day before surgery, 1 day after surgery, and again at 3 months or 1 year. Endothelial cell counts were also performed 1 day before surgery and thereafter at 3 months or 1 year after surgery. The relationship between these two parameters was assessed statistically. Precise measurements of central corneal thickness were made by optical low coherence reflectometry. For comparative purposes, this parameter was also determined by ultrasonic pachymetry. Central corneal endothelial cell numerical density was estimated on photomicrographs taken with a specular microscope.

RESULTS

All patients had significant postoperative corneal swelling on the day after surgery; preoperative values were restored by 3 and 12 months, even though significant endothelial cell losses had occurred. No correlation existed between central corneal thickness and central corneal endothelial cell numerical density. Measurements estimated by ultrasonic pachymetry were more variable and significantly higher than those determined by optical low coherence reflectometry.

CONCLUSION

As long as the numerical density of the corneal endothelial cells does not fall below the physiological threshold, a moderate decrease in this parameter does not compromise the pumping activity of the layer as a whole.

Human corneal thickness and its impact on intraocular pressure measures: a review and meta-analysis approach

We determined the "normal" central corneal thickness (CCT) value in human corneas based on reported literature values for within-study average CCT values, and used this as a reference to assess the reported impact of physiological variables (especially age and diurnal effects), contact lens wear, pharmaceuticals, ocular disease, and ophthalmic surgery on CCT. With the expected CCT and its variance defined, it should be possible to determine the potential impact of differences in CCT in intraocular pressure (IOP) assessments, especially by applanation tonometry, using a meta-analysis approach. Some 600 sets of CCT data were identified from the worldwide literature over the period of 1968 through mid-1999, of which 134 included IOP measures as well. The within-study average CCT values and reported variance (SD) was noted along with the number of eyes and any special characteristics, including probable ethnic origin of the study subjects. Various sets of data were subjected to statistical analyses. From 300 data sets from eyes designated as normal, the group-averaged CCT was 0.534 mm. From 230 data sets where interindividual variance was reported, the group-averaged CCT was 0.536 mm (median 0.536 mm; average SD of 0. 031 mm, average coefficient of variation = 5.8%). Overall, studies using slit-lamp-based pachometry have reported marginally lower CCT values (average 0.530 mm, average SD 0.029 mm) compared to ultrasound-based studies (average 0.544, average SD 0.034 mm), which perhaps reflects the type of individual studied (non-surgical vs. pre-surgical patients) rather than the technique itself. A slight chronological increase in reported average CCT values (approximately 0.006 mm/decade) was evident, but a substantial chronological increase was evident for ultrasound pachometry studies (approximately 0.015 mm/decade). Within the meta-analysis-generated average and variance, age had no obvious impact on CCT measures for *whites, although an age-related decline in CCT is evident for non-whites. Any diurnal effects are likely concealed within the expected variance in CCT. Contact lens wear and pharmaceuticals generally produced changes in CCT that were well within the expected variance in CCT. Of the ocular diseases, only those associated with collagen disorders (including keratoconus) or endothelial-based corneal dystrophies (e.g., Fuchs) were likely to result in decreases or increases, respectively, of CCT beyond the normal variance. Routine contact lens wear and diseases such as diabetes seem unlikely to produce changes in CCT of a magnitude that would justify pachometry as a monitoring method beyond routine slit-lamp evaluation. Increases in CCT beyond the expected variance were reported after a range of intraocular surgeries (cataract operations, penetrating keratoplasty), whereas photorefractive surgery produces a measurable decrease in CCT. A meta-analysis of possible association between CCT and IOP measures of 133 data sets, regardless of the type of eyes assessed, revealed a statistically significant correlation; a 10% difference in CCT would result in a 3. 4 +/- 0.9 mm Hg difference in IOP (P </= 0.001, r = 0.419). The observed phenomenon was much smaller for eyes designated as healthy (1.1 +/- 0.6 mm Hg for a 10% difference in CCT, P = 0.023, r = 0. 331). For eyes with chronic diseases, the change was 2.5 +/- 1.1 mm Hg for a 10% difference in CCT (P = 0.005, r = 0.450), whereas a substantial but highly variable association was seen for eyes with acute onset disease (approximately 10.0 +/- 3.1 mm Hg for a 10% difference in CCT, P = 0.004, r = 0.623). Based on the meta-analysis, normal CCT in white adults would be expected to be within +/-11.6% (+/-2 SD) of 0.535 mm, i.e., 0.473-0.597 mm (95% CI, 0.474-0.596). The impact of CCT on applanation tonometry of healthy eyes is unlikely to achieve clinical significance, but for corneas of eyes with chronic disease, pachometry should be performed if the tonometry reveals IOP readi

Ten-year postoperative results of penetrating keratoplasty

OBJECTIVE

To investigate the changes in central corneal endothelial cells and corneal thickness in transplanted corneas from 5 to 10 years after grafting. This study also aimed to investigate the development of glaucoma, graft rejection, and graft failure during the first 10 postoperative years.

DESIGN/PARTICIPANTS

Longitudinal cohort study of 500 consecutive penetrating keratoplasties by 1 surgeon. Patients were asked to return for follow-up examinations at 2 months and at 1, 3, 5, and 10 years after grafting. The authors excluded eyes regrafted during the study and the fellow eyes of bilateral cases, leaving 394 grafts in 394 patients for analysis.

INTERVENTION

Penetrating keratoplasty was performed.

MAIN OUTCOME MEASURES

Using specular microscopy, the authors measured endothelial cell density, coefficient of variation of cell area, percentage of hexagonal cells, and corneal thickness. The authors performed clinical examinations to determine graft rejection or failure and the development of glaucoma.

RESULTS

By 10 years postkeratoplasty, 80 of the 394 patients had died and 68 grafts had failed. Of the remaining 246 patients, 119 (48%) returned for their 10-year examinations. For the 72 patients who returned for all of the scheduled postoperative visits and had no rejection episodes, reoperations, or failure, endothelial cell loss from preoperative donor levels at 10 years was 67 +/- 18% (mean +/- standard deviation), endothelial cell density was 958 +/- 471 cells/mm2, coefficient of variation was 0.32 +/- 0.11, hexagonal cells were 56 +/- 12%, and corneal thickness was 0.58 +/- 0.05 mm. The 5- to 10-year changes for all these values were significant (P < or = 0.004). The mean rate of late endothelial cell loss from 5 to 10 years postkeratoplasty was 4.2% per year. Eyes that were aphakic after grafting had the lowest endothelial cell loss (57 +/- 24%) and the lowest interval cell loss from 5 to 10 years postkeratoplasty (4 +/- 19%). Eyes that were phakic had the highest endothelial cell loss (73 +/- 8%) and 5- to 10-year-interval cell loss (17 +/- 31%). Eyes with posterior chamber lenses had a greater endothelial cell loss (71 +/- 9%) than did eyes with anterior chamber lenses (51 +/- 25%, P = 0.03). The 10-year cumulative risk of glaucoma, rejection, or failure was 21%, 21%, and 22%, respectively. Late endothelial failure became the major cause for graft failure, accounting for 9 of the 11 failures after 5 postoperative years.

CONCLUSIONS

From 5 to 10 years after penetrating keratoplasty, the annual rate of endothelial cell loss was seven times the normal rate. The endothelial cell loss, pleomorphism, polymegethism, and corneal thickness increased significantly during this time, indicating continued endothelial instability and dysfunction, resulting in an increasing rate of late endothelial failure.

The influence of glaucoma history on graft survival after penetrating keratoplasty

BACKGROUND

It was the purpose of this retrospective study to evaluate the effect of a preoperative history of glaucoma on graft survival after penetrating keratoplasty.

PATIENTS AND METHODS

Six hundred and forty-six penetrating keratoplasties with generally good prognosis were analyzed retrospectively. Indications for surgery were corneal dystrophy, degeneration and scarring. Only first keratoplasties in corneas without severe vascularization or acute inflammation were included. Surface disorders, a history of herpes or Acanthamoeba keratitis were further exclusion criteria. Keratoplasties were performed only if glaucoma seemed to be controlled preoperatively. Graft survival ratios were calculated according to Kaplan and Meier, and statistical significance was evaluated by means of the log-rank test.

RESULTS

With a glaucoma history the estimated 3-year graft survival rate was 71%, in contrast to 89% without such a history. This difference was statistically significant (P < 0.001). There was no difference between the groups with respect to immune reactions. With a glaucoma history, postoperative episodes of glaucoma decompensation were responsible for half of the graft failures.

CONCLUSIONS

A preoperative history of glaucoma affects graft prognosis negatively, presumably through a negative influence of postoperatively elevated intraocular pressure on a vulnerable graft endothelium, and not by an increase in immune reactions. Therefore, keratoplasties in eyes with glaucoma are high-risk procedures and glaucoma has to be monitored more efficiently pre- and postoperatively.