Reassessment of the corneal endothelial cell organisation in children

Hemi-Ultrathin Descemet Stripping Automated Endothelial Keratoplasty (Hemi-UT-DSAEK) Using Pediatric Donor Corneas: A Case Series

OBJECTIVE

We sought to evaluate the clinical outcomes of hemi-UT-DSAEK grafts from the pediatric donor corneas of patients affected by Fuchs Endothelial Corneal Dystrophy (FECD).

METHODS

A prospective, interventional case series was conducted at the Ophthalmology Department of Venice Civil Hospital and the Veneto Eye Bank Foundation (Venice, Italy). Six eyes of six patients affected by FECD received large-diameter, semicircular hemi-UT-DSAEK grafts obtained from three pediatric donor corneas using the standard pull-through method. Endothelial cell density (ECD), central corneal thickness (CCT), best-corrected visual acuity (BCVA) and intraoperative and postoperative complications were recorded at different time intervals up to 12 months.

RESULTS

The average donor age was 64.6 ± 8.6 years, and the pre-operative ECD was 3266 ± 225 cells/mm2. At 12 months postoperatively, the average ECD was 1376 ± 509 cells/mm2 with a mean decrease of 56.8 ± 19.1% from the preoperative donor count. At 12 months, four out of six eyes had significantly improved and reached a BCVA of ≥20/25 (Snellen equivalent). The mean CCT significantly decreased from 788 ± 138 μm before surgery to 576 ± 30 μm at 12 months postoperatively (p < 0.01).

CONCLUSIONS

Hemi-UT-DSAEK grafts using pediatric donor corneas are surgically feasible and can provide similar clinical outcomes compared to conventional UT-DSAEK. Transplanting pediatric donor tissues with high ECD into two patients could potentially increase the donor tissue pool to treat endothelial disease.

The network structure of the corneal endothelium

A generic network model is applied to study the structure of the mammalian corneal endothelium. The model has been shown to reproduce the network properties of a wide range of systems, from low-dimensional inorganic glasses to colloidal nanoparticles deposited on a surface. Available extensive experimental microscopy results are analyzed and combined to highlight the behavior of two key metrics, the fraction of hexagonal rings (p₆) and the coefficient of variation of the area. Their behavior is analyzed as a function of patient age, the onset of diabetes, and contact lens wearing status. Wearing contact lenses for ∼10 years is shown to change the endothelium structure by the equivalent of ∼30 years contact lens-free. Model network configurations are obtained using a Monte Carlo bond-switching algorithm, with the resulting topologies controlled by two potential model parameters (the bond and angular force constants) and the Monte Carlo temperature. The effect of systematically varying these parameters is investigated. In addition, the effect of constraining the ring size distribution is investigated. The networks generated with relatively weak bond force constants are shown to correlate best with the experimental information. The importance of extracting the full ring size distribution (rather than simply the fraction of hexagons) is discussed.

Corneal endothelial morphology of healthy myopic Malaysian children of Chinese ethnicity aged 8-9 years and its association with axial length

Background: This is a cross-sectional study to further understand the effects of axial length elongation on the corneal endothelial cell’s morphology in myopic children. Abnormal changes in the morphology of corneal endothelium are indicators of corneal stress or instability which could be linked to myopia. Methods: 111 school children comprising of 37 emmetropes, 37 mild myopes and 37 moderate myopes aged 8-9 years old were recruited. Visual acuity was measured using the LogMar chart, cycloplegic refraction was determined using an open-field autorefractor (Grand Seiko WAM-5100, Hiroshima, Japan) and refined using subjective refraction. Morphology of corneal endothelial cells [endothelial cell density, coefficient of variation, hexagonality and central corneal thickness] was evaluated using a non-contact specular microscope (Topcon SP-2000P). Axial length was measured with A-scan ultrasound biometry (PacScan Plus, Sonomed Escalon, NY). The correlation between morphology of corneal endothelial cells and axial length were assessed using Pearson Correlation and Linear regression analysis. Results: There was no significant difference in corneal endothelial cells and axial length between gender (p>0.05). Significant reduction in endothelial cells density and hexagonality and increased coefficient of variation was found in eyes of higher myopic power which had longer axial when compared to emmetropes (p<0.001). Except for central corneal thickness, all corneal endothelial cells parameters correlated significantly with axial length (p<0.05). For every 1mm increase in axial length, endothelial cells density decreased by 73.27cells/mm2, hexagonality decreased by 2.32% and coefficient of variation increased by 1.75%. Conclusions: There were significant changes in morphology of cornea endothelial cells in young moderate myopic children of Chinese ethnicity at 8-9 years of age. This result provides normative data for Malaysian children of Chinese ethnicity that can be used for comparison and reference for clinical procedures, thereby facilitating decision-making with respect to interventions for myopia control, especially in prescribing contact lens for children.

Corneal endothelial assessment in xeroderma pigmentosum: a case-control study

PURPOSE

To analyze and compare corneal endothelial mosaic in terms of endothelial cell population, morphology and irregularity in patients with xeroderma pigmentosum (XP) with clear corneas with normal age and sex matched subjects using specular microscopy.

METHODS

Nine patients with XP without corneal involvement were evaluated in the study. An age and sex matched group of nine healthy subjects participated as control group. Evaluation of corneal endothelial layer was performed using specular microscopy.

RESULTS

Each study group consisted of five males and four females with total mean age of 28 ± 11.3 years (12-46 years). Endothelial cell density was significantly lower in patients with XP in comparison with controls (P < 0.002). Maximum and minimum cell areas were significantly higher in XP group (P < 0.016 and P < 0.029, respectively). Although central corneal thickness was higher in controls, the difference was not statistically significant (P = 0.106). Furthermore, our study showed that the patients with XP had no difference with controls in terms of coefficient of variation of cell areas.

CONCLUSIONS

This study showed that endothelial cell population can decrease in patients with XP, although other specular microscopic variables such as coefficient of variation and central corneal thickness may remain within normal values.

Corneal thickness and endothelial morphology in Normal Thai eyes

Background

This study aimed to determine the influence of age on central corneal thickness and corneal endothelial morphology as well as to identify the relationship between them in normal Thai eyes.

Methods

Non-contact specular microscopy was performed in volunteers stratified into seven age groups ranging from 11 to 88 years. The corneal endothelial parameters studied included central corneal thickness (CCT), endothelial cell density (ECD), coefficient of variation in cell size (CV), cell area (CA) and percentage of regular hexagonal cells.

Results

In a total of 501 subjects (1002 eyes), the mean age was 43.12 ± 18.80 years and 347(69.3%) were females. The mean CCT, ECD, CV, CA, and hexagonality was 533.80 ± 33.00 μm, 2732 ± 258 cell/mm², 37.61 ± 6.76%, 369.04 ± 37.90 μm, and 49.03 ± 7.53%, respectively. There was a significant inverse correlation between age and CCT (r = − 0.215, P <  0.001), ECD (r = − 0.496, P <  0.001),and hexagonality (r = − 0.265, P <  0.001). The CV and CA directly correlated with age (r = 0.242, P <  0.001 and r = 0.470, P <  0.001). The estimate rate of endothelial cell loss was 0.2% per year. There was no correlation between CCT and ECD (P = 0.106).

Conclusion

Normative data for corneal endothelial morphology in healthy Thai eyes showed that CCT, ECD, and hexagonality were significantly decreased, while the endothelial cell area and the variation in cell size were increased with aging. The central corneal thickness did not correlate with the endothelial cell density.

Riding the cell jamming boundary: Geometry, topology, and phase of human corneal endothelium

It is important to assess the viability of eye-banked corneas prior to transplantation due to inherent senescence and known loss of endothelial cells during surgical manipulation. Corneal endothelial cells have a complex basal and paracellular shape making them challenging to accurately measure, particularly in oedematous ex vivo tissue. This study used calibrated centroidal Voronoi Diagrams to segment cells in images of these human corneas, in order to characterize endothelial geometry, topology, and phase. Hexagonal cells dominated the endothelia, with most comprised of five different pleomorphs exhibiting self-similar topological coarsening through most of the endothelial cell density range. There was a linear relationship between cell size and shape, though cells with greater than six sides were present in larger proportions than cells with less. Hexagonal cell regularity was stable and largely independent of density. Cell and tissue phase was also examined, using the cell shape index relative to the recently discovered 'cell jamming' phase transition boundary. Images showed fluid endothelia with a range of shape indices spanning the boundary, independent of density but dependent on hexagonal regularity. The cells showed a bimodal distribution centred at the boundary, with the largest proportion of cells on the fluid side. A shoulder at the boundary suggested phase switching via shape transformation across the energy barrier, with cells either side having distinctly different size and shape characteristics. Regular hexagonal cells were closest to the boundary. This study showed the corneal endothelium acts as a glassy viscous foam characterized by well-established physical laws. Endothelial cell death transiently and locally increases cell fluidity, which is subsequently arrested by jamming of the pleomorphically diverse cell collective, via rearrangement and shape change of a small proportion of cells, which become locked in place by their neighbours thereby maintaining structural equilibrium with little energy expenditure.

A novel method for examining corneal endothelial cell morphology in infants

Previous studies have suggested that central corneal endothelial cell density (ECD) decreases from 6,100 cells/mm² in neonates to 3,100 cells/mm² in 10-year-olds. Currently data on ECD in young children as well as the trend for ECD decrease during childhood is sparse because of the difficulty of examination using existing clinic-based specular microscopes. We developed a novel method of imaging young children intraoperatively with the goal of beginning to establish age-specific normative data for ECD and hexagonality of cells (%HEX). Children were imaged using our novel technique under general anesthesia or awake in clinic using a child-friendly technique. A total of 58 children were recruited (mean age, 5.50; range, 0.44-10.36). Our cohort displayed a significant linear decrease in ECD with age (r = -0.56, P < 0.001). No correlation was found between %HEX and age (r = -0.10, P = 0.48).

Micro- and nano-topography to enhance proliferation and sustain functional markers of donor-derived primary human corneal endothelial cells

One of the most common indications for corneal transplantation is corneal endothelium dysfunction, which can lead to corneal blindness. Due to a worldwide donor cornea shortage, alternative treatments are needed, but the development of new treatment strategies relies on the successful in vitro culture of primary human corneal endothelial cells (HCECs) because transformed cell lines and animal-derived corneal endothelial cells are not desirable for therapeutic applications. Primary HCECs are non-proliferative in vivo and challenging to expand in vitro while maintaining their characteristic cell morphology and critical markers. Biochemical cues such as growth factors and small molecules have been investigated to enhance the expansion of HCECs with a limited increase in proliferation. In this study, patterned tissue culture polystyrene (TCPS) was shown to significantly enhance the expansion of HCECs. The proliferation of HCECs increased up to 2.9-fold, and the expression amount and localization of cell-cell tight junction protein Zona Occludens-1 (ZO-1) was significantly enhanced when grown on 1 μm TCPS pillars. 250 nm pillars induced an optimal hexagonal morphology of HCEC cells. Furthermore, we demonstrated that the topographical effect on tight-junction expression and cell morphology could be maintained throughout each passage, and was effectively 'remembered' by the cells. Higher amount of tight-junction protein expression was maintained at cell junctions when topographic cues were removed in the successive seeding. This topographic memory suggested topography-exposed/induced cells would maintain the enhanced functional markers, which would be useful in cell-therapy based approaches to enable the in situ endothelial cell monolayer formation upon delivery. The development of patterned TCPS culture platforms could significantly benefit those researching human corneal endothelial cell cultivation for cell therapy, and tissue engineering applications.

Correlation analysis between central corneal thickness and intraocular pressure in juveniles in Northern China: the Jinan city eye study

Purpose

To determine the distributions and relation of central corneal thickness (CCT) and intraocular pressure (IOP) by NT-530P in Chinese juveniles, and the effect of gender, age, height, weight and refractive errors on the CTT and IOP.

Methods

CCT and IOP of 982 eyes in 514 juveniles aged from 7 to 18 years were measured with NT-530P. Multi-linear regression and ANOVA analysis were used to analyze the relation of CCT and IOP, and the effect of gender, age, height, weight, refractive condition on CCT and IOP respectively.

Results

The mean CCT and IOP were 554.19±35.46 µm and 15.31±2.57 mmHg. There were significant correlations between the CCT and IOP values. Linear regression analysis revealed a positive correlation between CCT and IOP (r = 0.44, P<0.05). Linear regression equation: IOP = −2.35+0.032CCT, which means the IOP will increase 0.32 mm Hg for every 10-µm increase in CCT. The mean of Corrected IOP (CIOP) was 15.32±2.38 mmHg and had no relation with CCT. There was a negative correlation between refraction degree and CCT (P<0.05), but no correlation between refraction degree and IOP. Multi-linear regression model revealed that the height, weight, age and gender have no effect on the distribution of CCT and IOP respectively.

Conclusions

There is a 0.32 mmHg increase in IOP for every 10-µm increase in CCT. The height, weight, age and gender has no effect on the distribution of CCT and IOP. CCT will become thinner with myopia diopters increases in juveniles. The measurement of CCT is helpful in evaluating the actual IOP correctly.

Corneal endothelial cell density and morphology in low and moderate myopic Chinese eyes

AIM

To describe and compare the corneal endothelial cell density and morphology in young, low and moderate myopic Chinese adults in Malaysian Chinese population.

METHODS

Non-contact specular microscopy (Topcon SP3000P, Tokyo, Japan) was performed in low (n=78; 21.22±1.51 years) and moderate (n=78; 21.82±1.40 years) myopic subjects. The mean of three consecutive measurements of endothelial cell density (MCD), coefficient of variation (CV) in the cell size, and hexagonal appearance of the cell were obtained.

RESULTS

In low myopic eyes the MCD was 3 063.0±176.2/mm(2), the mean CV was 33.4±4.0% and the mean hexagonal appearance of the cell was 57.9±2.7%. In moderate myopic eyes the MCD was 2961.6±159.0/mm(2), the mean CV was 33.9±3.6% and mean hexagonal appearance of the cell was 56.2±4.7%. There were statistically significant differences in MCD (P<0.000) and hexagonal appearance of the cell (P<0.005) between low and moderate myopic eyes.

CONCLUSION

The corneal endothelial cell layer in more myopic eyes tends to have less MCD and cell hexagonality compared to lower myopic eyes. Nevertheless, there is no significant difference in CV between low and moderate myopic eyes.

Corneal endothelial cell characteristics after pediatric cataract surgery

PURPOSE

To describe the corneal endothelial cell characteristics after pediatric cataract surgery.

METHODS

Retrospective case series of 29 study eyes and 26 controls were evaluable. Specular microscopy was performed and endothelial cell features were correlated with clinical and surgical features.

RESULTS

Mean age at testing was 106 months in the study group and 116 months in the control group with a mean interval of 78 months after cataract surgery. Mean endothelial cell density in study eyes was 2,668 cells/mm(2) (control eyes, 3,002 cells/mm(2), P < .01). Mean coefficient of variation was 35% (control eyes, 31%, P < .01), and mean percentage of hexagonal cells was 40% (control eyes, 51%, P < .01). There was no significant difference based on age, duration since cataract surgery, contact lens use, glaucoma, number of intraocular procedures, or presence of intraocular lens.

CONCLUSIONS

This study demonstrates endothelial cell loss with polymegathism and pleomorphism in children undergoing cataract surgery. This poses a risk of developing long-term corneal complications and hence close monitoring of the endothelial cell count is advisable.

Characterization of porcine corneal endothelium for xenotransplantation

PURPOSE

Endothelial keratoplasty (EKP) has become increasingly popular in the treatment of corneal disease. However, the global shortage of human donor corneas limits clinical corneal transplantation. Genetically engineered (GE) pigs may provide an alternative source of corneas for EKP. The aim of this study was to evaluate corneal endothelial cells (CECs) from wild-type (WT) and GE pigs.

METHODS

Density, size of CECs, and the percentage of hexagonal cells (as a measure of heterogeneity) were measured by ex vivo confocal microscopy in corneas from WT and GE pigs of different ages - neonatal (4-5 days), young (5-15 weeks), adult (5-15 months), and old (20-42 months). α1,3-galactosyltransferase gene-knockout (GTKO) pigs transgenic for the human complement-regulatory protein(s), CD46 (GTKO/CD46) +/- CD55 (GTKO/CD46/CD55) were used as sources of GE corneas.

RESULTS

Mean CEC densities (cells/mm²) were neonatal (5968), young (3789), adult (2589), and old (2070). As with human corneas, there was an age-dependent decrease in pig CEC density and increase in pig CEC size. However, unlike human corneas, there was no correlation between the percentage of hexagonal cells (approximately 50% in all pig corneas) and age, suggesting that heterogeneity is intrinsic for pig corneas. Genetic modification did not affect CEC density, size, or morphology compared to WT pigs.

CONCLUSION

Because of the availability of young pigs and their greater CEC density (and the protection afforded against the human immune response), GE pigs could provide an unlimited source of corneas for clinical EKP.

Ocular manifestations of xeroderma pigmentosum: long-term follow-up highlights the role of DNA repair in protection from sun damage

OBJECTIVE

Xeroderma pigmentosum (XP) is a rare autosomal recessive disease caused by mutations in DNA repair genes. Clinical manifestations of XP include mild to extreme sensitivity to ultraviolet radiation resulting in inflammation and neoplasia in sun-exposed areas of the skin, mucous membranes, and ocular surfaces. This report describes the ocular manifestations of XP in patients systematically evaluated in the Clinical Center at the National Institutes of Health.

DESIGN

Retrospective observational case series.

PARTICIPANTS

Eighty-seven participants, aged 1.3 to 63.4 years, referred to the National Eye Institute (NEI) for examination from 1964 to 2011. Eighty-three patients had XP, 3 patients had XP/Cockayne syndrome complex, and 1 patient had XP/trichothiodystrophy complex.

METHODS

Complete age- and developmental stage-appropriate ophthalmic examination.

MAIN OUTCOME MEASURES

Visual acuity; eyelid, ocular surface, and lens pathology; tear film and tear production measures; and cytologic analysis of conjunctival surface swabs.

RESULTS

Of the 87 patients, 91% had at least 1 ocular abnormality. The most common abnormalities were conjunctivitis (51%), corneal neovascularization (44%), dry eye (38%), corneal scarring (26%), ectropion (25%), blepharitis (23%), conjunctival melanosis (20%), and cataracts (14%). Thirteen percent of patients had some degree of visual axis impingement, and 5% of patients had no light perception in 1 or both eyes. Ocular surface cancer or a history of ocular surface cancer was present in 10% of patients. Patients with an acute sunburning skin phenotype were less likely to develop conjunctival melanosis and ectropion but more likely to develop neoplastic ocular surface lesions than nonburning patients. Some patients also showed signs of limbal stem cell deficiency.

CONCLUSIONS

Our longitudinal study reports the ocular status of the largest group of patients with XP systematically examined at 1 facility over an extended period of time. Structural eyelid abnormalities, neoplasms of the ocular surface and eyelids, tear film and tear production abnormalities, ocular surface disease and inflammation, and corneal abnormalities were present in this population. Burning and nonburning patients with XP exhibit different rates of important ophthalmologic findings, including neoplasia. In addition, ophthalmic characteristics can help refine diagnoses in the case of XP complex phenotypes. DNA repair plays a major role in protection of the eye from sunlight-induced damage.

Cultivation of human microvascular endothelial cells on topographical substrates to mimic the human corneal endothelium

Human corneal endothelial cells have a limited ability to replicate in vivo and in vitro. Allograft transplantation becomes necessary when an accident or trauma results in excessive cell loss. The reconstruction of the cornea endothelium using autologous cell sources is a promising alternative option for therapeutic or in vitro drug testing applications. The native corneal endothelium rests on the Descemet’s membrane, which has nanotopographies of fibers and pores. The use of synthetic topographies mimics the native environment, and it is hypothesized that this can direct the behavior and growth of human microvascular endothelial cells (HMVECs) to resemble the corneal endothelium. In this study, HMVECs are cultivated on substrates with micron and nano-scaled pillar and well topographies. Closely packed HMVEC monolayers with polygonal cells and well-developed tight junctions were formed on the topographical substrates. Sodium/potassium (Na⁺/K⁺) adenine triphosphatase (ATPase) expression was enhanced on the microwells substrate, which also promotes microvilli formation, while more hexagonal-like cells are found on the micropillars samples. The data obtained suggests that the use of optimized surface patterning, in particular, the microtopographies, can induce HMVECs to adopt a more corneal endothelium-like morphology with similar barrier and pump functions. The mechanism involved in cell contact guidance by the specific topographical features will be of interest for future studies.

Corneal endothelial morphologic assessment in pediatric cataract surgery with intraocular lens implantation: a comparison of preoperative and early postoperative specular microscopy

PURPOSE

To observe longitudinal changes in the corneal endothelium after pediatric cataract surgery with intraocular lens implantation.

DESIGN

Prospective, longitudinal study.

METHODS

settings: Iladevi Cataract and IOL Research Centre, Ahmedabad, India. study population: This study included 100 pediatric eyes undergoing cataract surgery with intraocular lens implantation. Posterior capsule management was based on the status of the posterior capsule. Two-port anterior limbal vitrectomy was carried out after posterior capsule plaque peeling. observation procedures: Corneal endothelial morphologic features: endothelial cell density (cell/mm(2)), coefficient of variation, percentage of hexagonality, and central corneal thickness were assessed. main outcome measures: To evaluate whether there is a difference in endothelial cell morphologic features before surgery and 3 months after surgery and also whether pediatric cataract surgery with and without anterior vitrectomy has any impact on the endothelial cell morphologic features.

RESULTS

A comparison of preoperative and postoperative specular microscopy is given here: endothelial cell density, 3225.1 ± 346.8 cells/mm(2) versus 3057.7 ± 330.1 cells/mm(2) (P < .001); coefficient of variation, 27.5 ± 10.6 versus 37.7 ± 16.3 (P < .001); percentage of hexagonality, 58.1 ± 15.3 versus 48.6 ± 13.4 (P < .001); and central corneal thickness, 529 ± 30 μm versus 527 ± 34 μm (P = .64). There was 5.1% decrease in mean endothelial cell loss at 3 months after surgery. No statistically significant difference was noted in the percentage decrease in mean endothelial cell density between eyes undergoing cataract surgery with intact posterior capsules, eyes undergoing manual posterior capsulorrhexis without anterior limbal vitrectomy, and eyes undergoing anterior limbal vitrectomy (P = .543).

CONCLUSIONS

Endothelial cell loss with currently practiced techniques of pediatric cataract surgery is within acceptable limits by adhering to the principles of close chamber technique.

Central corneal thickness and intraocular pressure in Malay children

Background

To determine the mean values for central corneal thickness (CCT) and intraocular pressure (IOP) and the relationship between these values, in healthy Malay children to serve as reference values in diagnosis and treatment.

Design

A cross-sectional study.

Methodology/Principal Findings

One hundred and eight eyes (54 subjects) of Malay children without diagnosis of ocular abnormality or disease meeting our inclusion and exclusion criteria were selected. The CCT and IOP were measured by specular microscopy and non-contact air-puff tonometry respectively, for analysis and comparison with the values obtained in previous studies. Mean CCT and IOP was found to be 530.87±30.79 µm and 15.65±3.05 mm Hg respectively. CCT was found not to vary with age. A positive relationship was found between CCT and IOP; specifically, with every 100-µm increase in CCT, IOP increased by 3.5 mm Hg.

Conclusions/Significance

CCT and IOP are strongly related in healthy Malay children aged 8 to 16. The mean CCT of Malay children is lower than that of majority children of other ethnic groups, supporting the existence of CCT variation among different populations and that ethnicity should be a key consideration when applying CCT data to the general pediatric population.

Ocular manifestations of trichothiodystrophy

OBJECTIVE

Trichothiodystrophy (TTD) is a rare, autosomal recessive disorder characterized by sulfur-deficient brittle hair and multisystem abnormalities. Many TTD patients have a defect in known DNA repair genes. This report systematically evaluates the ocular manifestations of the largest-to-date cohort of TTD patients and xeroderma pigmentosum (XP)/TTD patients.

DESIGN

Case series.

PARTICIPANTS

Thirty-two participants, ages 1 to 30 years, referred to the National Eye Institute for examination from 2001 to 2010; 25 had TTD and 7 had XP/TTD.

METHODS

Complete, age- and developmental stage-appropriate ophthalmic examination.

MAIN OUTCOME MEASURES

Visual acuity (VA), best-corrected VA, ocular motility, state of the ocular surface and corneal endothelial cell density, corneal diameter, and lens assessment.

RESULTS

Developmental abnormalities included microcornea (44% TTD), microphthalmia (8% TTD, 14% XP/TTD), nystagmus (40% TTD), and infantile cataracts (56% TTD, 86% XP/TTD). Corrective lenses were required by 65% of the participants, and decreased best-corrected VA was present in 28% of TTD patients and 71% of XP/TTD patients. Degenerative changes included dry eye (32% TTD, 57% XP/TTD) and ocular surface disease identified by ocular surface staining with fluorescein (32% TTD) that usually are exhibited by much older patients in the general population. The 2 oldest TTD patients exhibited clinical signs of retinal/macular degeneration. Four XP/TTD patients presented with corneal neovascularization.

CONCLUSIONS

These TTD and XP/TTD study participants had a wide variety of ocular findings including refractive error, infantile cataracts, microcornea, nystagmus, and dry eye/ocular surface disease. Although many of these can be ascribed to abnormal development--likely owing to abnormalities in basal transcription of critical genes--patients may also have a degenerative course.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosures may be found after the references.

Clinical phenotype of posterior polymorphous corneal dystrophy in a family with a novel ZEB1 mutation

PURPOSE

To describe the clinical phenotype in a family with posterior polymorphous corneal dystrophy (PPCD) and a novel mutation in the ZEB1 gene.

METHODS

 Clinical examination, anterior segment photography, specular microscopy and electrophysiological investigations were performed and quantified. Genomic DNA extracted from peripheral blood was sequenced for ZEB1 exons. Cosegregation of identified mutation with the disease status in the family was confirmed using polymerase chain reaction and restriction fragment length polymorphism.

RESULTS

Ocular examination was performed on five family members from two generations. Three had anomalies of the corneal endothelium that were consistent with PPCD. Endothelial cell counts ranged from 2306 to 2987 mm(2) (ref. 2000-4000 cells/mm(2) ). No evidence of glaucoma or retinal abnormalities was observed. Extraocular abnormalities such as inguinal herniation, hydrocoele and possible bony or connective tissue anomalies were part of the disease spectrum in this family. Mutation analysis revealed a novel change in exon 5 of ZEB1 (c.672delA) that cosegregated with the affected disease status.

CONCLUSION

The detailed clinical features of PPCD associated with a novel ZEB1 mutation are supportive of the previously proposed range of phenotype parameters. Further phenotype-genotype correlations may provide insights into the clinical variability and pathological processes affecting the corneal endothelium, Descemet's membrane, retinal photoreceptor function and extraocular tissues of some patients.

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.

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.

Aging changes of mouse corneal endothelium and Descemet's membrane

The purpose of this study was to characterize age-associated changes in the corneal endothelium and Descemet's membrane (DM) in C57BL/6 mice, an inbred strain commonly used as a genetic disease model. Corneas from mice aged 2 weeks to 24 months were studied. Light microscopy was used to assess central endothelial cell density, area, and morphology. Transmission electron microscopy was used to assess thickness and ultrastructural features of DM. Central corneal endothelial cell density showed a rapid decline from 5,232+/-892 cells/mm(2) (mean+/-S.D.) at 2 weeks to 2,532+/-112 cells/mm(2) at 16 weeks of age. Thereafter, cell density declined more slowly, reaching 2,004+/-134 cells/mm(2) at 24 months of age. DM thickness showed an approximately linear increase from 1.12+/-0.22 microm (mean+/-S.D.) at 2 weeks to 4.19+/-1.17 microm at 24 months of age. DM in 2 and 6 week age groups was composed entirely of material with an electron dense, periodic banding pattern. Sixteen week, 12 month, and 24 month age groups exhibited an additional, progressively thicker, homogeneous layer lacking periodic banding. The observed age-dependent thickening of DM was predominantly due to accumulation of the posterior, non-banded layer. In C57BL/6 mice, central endothelial cell density declines with age and DM progressively thickens due to accumulation of a posterior, non-banded portion. These age-associated changes are strikingly similar to observations in humans and thus further support the potential usefulness of the mouse model for studying disorders of the corneal endothelium and Descemet's membrane.

Corneal endothelial cell density and morphology in normal Iranian eyes

Background

We describe corneal endothelial cell density and morphology in normal Iranian eyes and compare endothelial cell characteristics in the Iranian population with data available in the literature for American and Indian populations.

Methods

Specular microscopy was performed in 525 eyes of normal Iranian people aged 20 to 85 years old. The studied parameters including mean endothelial cell density (MCD), mean cell area (MCA) and coefficient of variation (CV) in cell area were analyzed in all of the 525 eyes.

Results

MCD was 1961 ± 457 cell/mm² and MCA was 537.0 ± 137.4 μm². There was no statistically significant difference in MCD, MCA and CV between genders (Student t-test, P = 0.85, P = 0.97 and P = 0.15 respectively). There was a statistically significant decrease in MCD with age (P < 0.001, r = -0.64). The rate of cell loss was 0.6% per year. There was also a statistically significant increase in MCA (P < 0.001,r = 0.56) and CV (P < 0.001, r = 0.30) from 20 to 85 years of age.

Conclusion

The first normative data for the endothelium of Iranian eyes seems to confirm that there are no differences in MCD, MCA and CV between genders. Nevertheless, the values obtained in Iranian eyes seem to be different to those reported by the literature in Indian and American populations.

Assessments of corneal endothelial cell density in growing children and its relationship to horizontal corneal diameter

BACKGROUND

Few studies have been published of corneal endothelial cell density (ECD) in children, especially in relation to the age and corneal size of the individuals. The possible effect of corneal enlargement on the endothelium was studied, and the results were objectively reviewed in relation to literature reports on corneal diameter and age.

METHODS

ECD was assessed in 119 children aged 5 to 15 years after endothelial photography with a noncontact specular microscope (Topcon SP-1000 or SP-2000P), followed by manual digitization of cell overlays. The horizontal corneal diameter, as the visible iris diameter, was measured to 0.5-mm accuracy.

RESULTS

The mean +/- SD value for ECD, calculated using all individual cell area values, was 3542 +/- 510 cells/mm2 (range, 2576 to 5316), whereas it was 3246 +/- 416 cells/mm2 (range, 2404 to 4817) if the mean cell area value from each image was used to calculate ECD. The mean horizontal corneal diameter was 11.48 +/- 0.58 mm (+/- SD). The corneal diameter was not obviously age-related for this group, but there were clear trends for younger children to have higher ECD values than older children (p2, depending on the method for calculating ECD.

CONCLUSIONS

ECD values were found to be significantly correlated to corneal diameter in children aged 5 to 15 years, and this factor should be considered in comparative studies.

A retrospective pilot study to assess the impact of strabismus surgery on the corneal endothelium in children

PURPOSE

To investigate if strabismus surgery has an impact on the corneal endothelium in children.

METHODS

Fourteen children who had undergone uncomplicated strabismus surgery an average of 41 months previously (range 24-73 months) were compared with a group of age-matched (range 5-12 years) and refractive error (RE)-matched (range -4.74 to +4.25 D) children. Following noncontact specular microscopy, areas of at least 100 cells were measured, the number of sides for each cell recorded, and endothelial cell density (ECD) calculated from the area measures. Corneal diameter was measured with a clinical rule, corneal curvature with a manual keratometer, central corneal thickness (CCT) by ultrasound pachometry, and IOP by non-contact tonometry.

RESULTS

The average ECD (+/-S.D.) in the post-surgery group was 4467+/-627 cells mm(-2), which was significantly higher (p < 0.02) than in the control group (3781+/-452 cells mm(-2)). This was because the average endothelial cell area in the surgery group was significantly smaller than in the control group (p < 0.005; 252+/-25 microm2 vs 296+/-29 microm2). Differences in cell areas were slightly greater for smaller cells (-15.7% for five-sided cells, -15.6% for six-sided cells, -14.3% for seven-sided cells and -13.8% for eight-sided cells). The cell differences appear to be related to both a slightly smaller corneal diameter (11.00+/-0.52 mm vs. 11.21+/-0.58 mm) and a slightly higher CCT (0.528+/-0.033 mm vs. 0.515+/-0.032 mm) in the post-operative group.

CONCLUSION

The endothelial mosaic in children after strabismus surgery can show a higher than expected ECD value and slight cell pleomorphism. These signs indicate that there might be differences in eye growth and endothelial inflammatory stress associated with uneventful strabismus surgery.