Corneal Endothelial Cell Layer Research Articles

Corneal Endothelial Features in Patients Operated for Primary Congenital Glaucoma

To compare the corneal endothelial cell morphology using specular microscopy imaging between primary congenital glaucoma (PCG) and age-matched healthy controls, and to determine if the endothelial cell parameters vary among different subtypes of PCG. Retrospective case-control study. One hundred forty-five eyes of 145 patients operated for PCG between 1991 and 2018 and who returned for a follow-up visit between June 2021 and May 2022. Three hundred and nineteen age-matched healthy individuals constituted the control group. Corneal endothelial cell layer analysis was performed with EM-3000 (Tomey) noncontact specular microscope. Patients were categorized according to the clinical subtypes of PCG (neonatal, infantile, and late-onset) based on the Childhood Glaucoma Research Network classification. Specular microscopic parameters, including endothelial cell density (ECD), average cell size, coefficient of variation (CV), and maximum and minimum cell size, were compared with that of the control group. Mean ± standard deviation (SD) age of patients at endothelial imaging was 13.5 ± 6.54 years, and there was a male preponderance (n= 88, 61%). The majority of the patients had infantile-onset PCG (n= 67, 46%). Eyes with PCG demonstrated a significantly lower ECD compared with controls (2158.7 ± 636.5 vs. 2840.9 ± 232.5 cells/mm2; P < 0.0001). Other endothelial cell parameters were also significantly worse in PCG compared with controls. The mean ± SD ECD was 2344.3 ± 544.3, 2131.9 ± 626.4, and 2054.2 ± 714.0 cells/mm2 in neonatal onset, infantile, and late-onset PCG groups, respectively. Although the ECD was lowest in the late-onset PCG group, there was no significant difference in the ECD between the 3 subgroups. Except for CV, all the endothelial cell parameters were significantly worse in eyes with Haab striae than in eyes without. Patients with PCG have significantly lower ECD compared with healthy controls. Furthermore, other endothelial cell parameters were also significantly worse in the PCG group. These changes in the corneal endothelium in patients with PCG should be considered in long-term medical and surgical management. The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Corneal endothelium – Specular microscopy

AbstractCorneal endothelium is a single layer of hexagonal cells covering the inner surface of the cornea and maintains the corneal deturgescence by continuous pumping of water and ions from the stroma to the aqueous humour. This mechanism is necessary to preserve the transparency of the cornea. The corneal endothelium is derived from the neural crest. Endothelial cells are arranged in a mosaic pattern of mostly hexagonal shaped cells. The cells can be characterized by different size (polymegathism) and different shape (pleomorphism). These parameters may reflect a compromised endothelial functional status.The corneal endothelial cell layer does not capable for regeneration, a constant and age‐dependent loss of corneal cells present during lifetime. Extensive injury of corneal endothelium leads to permanent corneal swelling and bullous alterations on the corneal surface. If left untreated and in chronic cases inflammation, later on permanent scarring may occur leads to loss of corneal transparency and finally decreased vision.Generally, a healthy cornea has about 1500–3500 endothelial cells/mm2 in the central area (age 40–75). The gold standard for the evaluation of endothelial cell density is endothelial microscopy, based on specular reflection, when light is reflected from the interfaces of materials with different indices of refraction. In addition, in vivo confocal microscope can also be used to visualize the endothelium, along with other tissue components of the cornea.Different forms of corneal damage by inflammatory processes or by mechanical trauma following intraocular surgery can lead to additional endothelial cell loss. Evaluation and proper examination of corneal endothelium and endothelial cell density is important and has clinical relevance in aging, corneal preservation, phacoemulsification, and post‐keratoplasty corneas.

Short-term endothelial cell density changes after gonioscopy-assisted transluminal trabeculotomy.

To investigate the reduction in corneal endothelial cell density associated with gonioscopy-assisted transluminal trabeculotomy (GATT) in a short-term follow-up period. A retrospective analysis of the medical charts of patients with open-angle glaucoma who underwent gonioscopy-assisted transluminal trabeculotomy isolated or combined with phacoemulsification (phaco-gonioscopy-assisted transluminal trabeculotomy) was conducted. Patients who underwent phacoemulsification alone were included as controls. The endothelial cell density data (assessed using a specular microscope) before and at the first month after operation were collected and then compared. Sixty-two eyes previously treated with gonioscopy-assisted transluminal trabeculotomy (gonioscopy-assisted transluminal trabeculotomy, n=39 eyes; phaco-gonioscopy-assisted transluminal trabeculotomy, n=23 eyes) fulfilled the inclusion criteria. The mean age of the study patients was 61.3 ± 18.4 years in the stand-alone gonioscopyassisted transluminal trabeculotomy group and 60.4 ± 11.9 in phaco-gonioscopy-assisted transluminal trabeculotomy group. Men comprised 66.6% of the patients in the isolated gonioscopyassisted transluminal trabeculotomy group and 56.5% of those in the phaco-gonioscopy-assisted transluminal trabeculotomy group. The mean visual field defects (mean deviation index) were -13.9 ± 9.2 and -10.3 ± 7.7 dB in the isolated gonioscopy-assisted and phaco-gonioscopy-assisted transluminal trabeculotomy groups, respectively. The patients in the former group presented a mean endothelial cell density reduction of 28.8 cells/mm² (1.31%; p=0.467). In the latter group, the mean endothelial cell density loss was 89.4 cells/mm² (4.36%; p=0.028). The control eyes (23 patients) presented a mean endothelial cell density change of 114.1 ± 159.8 cells/mm² (4.41%; p=0.505). The endothelial cell density reduction in the phaco-gonioscopy-assisted transluminal trabeculotomy group was not significantly different from that in the controls (p=0.81). Gonioscopy-assisted transluminal trabeculotomy appears to be a safe procedure for the corneal endothelial cell layer when performed either isolated or combined with cataract extraction in a short-term follow-up period.

Evaluation of corneal endothelial cell morphology by specular microscopy in patients with acute anterior uveitis.

To determine the structure and morphology of corneal endothelial cell layer in patients with acute anterior uveitis. Thirty-four eyes of 34 acute anterior uveitis patients and 34 eyes of 34 healthy subjects were included. Mean cell density, coefficient of variation, maximum cell area, minimum cell area, average cell area and hexagonality ratio values were evaluated by non-contact specular microscopy. Parameters recorded in both groups were compared. The mean maximum cell area was 1054,44 ± 251,14 µm2, minimum cell area was 152.29 ± 53.65 µm2 and average cell area was 386.91 ± 41.73 µm2 in acute anterior uveitis group and the mean maximum cell area was 1057.65 ± 261.23 µm2, minimum cell area was 147.26 ± 20.45 µm2 and average cell area was 383.53 ± 43.12 µm2 in the control group. There were no significant differences between the two groups in terms of maximum, minimum and average cell area (respectively, p = 0.080, p = 0.72, p = 0.62, p = 0.67). The mean cell density was 2607.74 ± 277.63 cells/ µm2 in acute anterior uveitis group and 2669.35 ± 265.22 cells/µm2 in the control group. (p = 0.358). In acute anterior uveitis group the mean coefficient of variation was 31.68 ± 8.16, hexagonality ratio was 63.85 ± 11.14 and mean central corneal thickness was 571.47 ± 55.99µm; in control group the mean coefficient of variation was 25.29 ± 3.00, mean hexagonality ratio was 72.6 ± 4.80% and mean central corneal thickness was 534.82 ± 33.84µm. Statistically significant differences were seen between the two groups (respectively, P = 0,00, P = 0,00, P = 0.02). The mean central corneal thickness and coefficient of variation values were found higher, and the hexagonality ratio was found lower in acute anterior uveitis group. Our findings suggest that intraocular inflammation in anterior chamber negatively affects the endothelial function in patients with acute anterior uveitis.

Long-term effect of contact lens wear: A citation network study

BackgroundContact lenses can cause complications in 2/3 of the total population, but in most cases, they are mild and easy to manage. However, most of the studies are short-term. The aim of the study was to analyze the publications on the long-term effects of contact lens wear to understand the current research landscape through the analysis of dating networks as well as determining the different research areas and the most cited publications. MethodsThe Web of Science database was used to perform the publication search, looking for the terms “Long-term” AND “contact lens wear” within the period between 1977 and January 2021. The CitNetExplorer and CiteSpace software were then used to conduct the publication analysis. To obtain the graphics, the VOSviewer software was used. ResultsA total of 721 publications were found with 2999 citations generated within the network. The year 2010 was singled out as a “key year”, considering the number of publications that emerged in that year and increase in adaptations of contact lens worldwide. The most widely cited publication was “Effects of long-term extended contact lens wear on the human cornea”, an article by Holden et al., which was published in 1985. By using the clustering function, we were able to establish three clusters that encompassed the different research areas within this field: morphological changes, the loss of corneal sensitivity, tear film characteristics and longitudinal changes in ocular physiology. ConclusionsThe main research topic in this field focuses on the morphological changes that take place in the corneal endothelial cell layer.

In Vivo confocal microscopy findings after COVID-19 infection

ABSTRACT Purpose: To evaluate clinical and in vivo confocal microscopy (IVCM) findings of a patient who developed multiple unilateral subepithelial stromal opacities following conjunctivitis that developed during a COVID-19 infection. Methods: A 22-year-old female presented to our clinic with blurred right vision. The history revealed that she had experienced a COVID-19 infection one month ago. Redness and stinging of the right eye had started at the same time and she had been prescribed topical antibiotic drops and ointments. The redness in the right eye had decreased but blurred vision had then developed. Results: Slit lamp examination revealed a normal left eye. Several tiny subepithelial infiltrates without fluorescein staining of the cornea were present in the right eye. The anterior chamber, lens and fundus were bilaterally normal. IVCM revealed irregular corneal epithelial cells with bright borders in addition to scattered inflammatory cells and cell debris in the right eye. There were activated dendritic cells in the subbasal epithelial area with a significant decrease in the subbasal corneal nerve plexus. Clusters of highly reflective cells with an irregular shape were seen in the anterior corneal stroma together with foci of activated keratocytes. The corneal endothelial cell layer was normal. The left eye IVCM findings were all within normal limits. The right eye also showed decreased corneal sensitivity compared to the left. Conclusions: The possible role of corneal infiltrates as a trigger for COVID-19 could be explained with an immune-mediated mechanism. SARS-CoV-2 can result in decreased corneal sensitivity through corneal nerve involvement. The clinical results of this effect need to be evaluated in larger series.

Corneal Endothelial Layer Parameters in Patients Undergoing Strabismus Surgery

Purpose: To investigate the effects of horizontal and oblique strabismus surgery on the corneal endothelial cell layer. Methods: Eighty-three eyes of 56 patients were prospectively evaluated. Corneal endothelial cell layer analysis was performed with a specular microscopy device (EM-3000; Tomey Corporation) preoperatively and 1 day, 2 weeks, and 2 months postoperatively. Endothelial cell density, coefficient of variation, average cell area, standard deviation (SD) of the endothelial cell area, hexagonality, and central corneal thickness (CCT) were evaluated. Results: Endothelial cell density, average cell area, and SD of the endothelial cell area did not show a statistically significant change postoperatively. In the one and two horizontal muscle surgery groups, the hexagonality measurements 2 weeks postoperatively were significantly lower compared to preoperative values. In the one horizontal muscle surgery group and when all patients were examined, CCT 1 day postoperatively was significantly higher than 2 weeks postoperatively. No significant change was observed postoperatively in any of the endothelial parameters in the oblique surgery group. Spherical equivalent was positively correlated with endothelial cell density and CCT, and it was negatively correlated with the average cell area and age. Age was positively correlated with the average cell area and the SD of the endothelial cell area, negatively correlated with endothelial cell density and hexagonality, and was not correlated with the coefficient of variation or CCT. Conclusions: There is a temporary effect of horizontal strabismus surgery on hexagonality and corneal thickness. A definite decrease in cellular hexagonality occurs as the number of endothelial cells decrease and cell areas increase with age. [ J Pediatr Ophthalmol Strabimus . 2021;58(4):254–260.]

Growth of Human and Sheep Corneal Endothelial Cell Layers on Biomaterial Membranes.

Corneal endothelial cell cultures have a tendency to undergo epithelial-to-mesenchymal transition (EMT) after loss of cell-to-cell contact. EMT is deleterious for the cells as it reduces their ability to form a mature and functional layer. Here, we present a method for establishing and subculturing human and sheep corneal endothelial cell cultures that minimizes the loss of cell-to-cell contact. Explants of corneal endothelium/Descemet's membrane are taken from donor corneas and placed into tissue culture under conditions that allow the cells to collectively migrate onto the culture surface. Once a culture has been established, the explants are transferred to fresh plates to initiate new cultures. Dispase II is used to gently lift clumps of cells off tissue culture plates for subculturing. Corneal endothelial cell cultures that have been established using this protocol are suitable for transferring to biomaterial membranes to produce tissue-engineered cell layers for transplantation in animal trials. A custom-made device for supporting biomaterial membranes during tissue culture is described and an example of a tissue-engineered graft composed of a layer of corneal endothelial cells and a layer of corneal stromal cells on either side of a collagen type I membrane is presented.

Corneal Endothelial Cell Density and Morphology in Different Trimesters of Pregnancy.

To evaluate corneal endothelial cell density (CD) and morphology in different trimesters of pregnancy. This prospective study included 66 (66 eyes) pregnant women. The patient group was divided into three subgroups comprised of 22 women in the first, second, and third trimesters of pregnancy. An age-matched group of 22 (22 eyes) volunteers served as controls. Corneal measurements were performed using specular microscopy (Noncon Robo SP8000, Konan Medical). Central corneal thickness (CCT) and CD, hexagonal cell ratio (HEX), and coefficient of variation (CV) of the corneal endothelial cell layer of the patients were measured at each trimester. Central corneal thickness did not change significantly during the pregnancy compared to controls (P>0.05). Endothelial CD was decreased in the first trimester and increased in the second and third trimesters, but the difference was not significant (P>0.05). Hexagonal cell ratio was decreased significantly in the first trimester (P<0.05). There was an increase in the second and third trimesters, which was not statistically significant (P>0.05). Coefficient of variation was increased significantly in the first trimester and showed a significant decrease in the second and third trimesters (P<0.05, respectively). Endothelial CD had a significant positive correlation with CV and HEX had a negative correlation with CV in the second trimester (r=0.438, P=0.041 and r=-0.822, P<0.001, respectively). Central corneal thickness and endothelial CD did not change significantly throughout the pregnancy. Hexagonal cell ratio and CV showed a significant but transient increase in the first trimester.

Proteomic analysis of corneal endothelial cell-descemet membrane tissues reveals influence of insulin dependence and disease severity in type 2 diabetes mellitus.

The objective of this study was to characterize the proteome of the corneal endothelial cell layer and its basement membrane (Descemet membrane) in humans with various severities of type II diabetes mellitus compared to controls, and identify differentially expressed proteins across a range of diabetic disease severities that may influence corneal endothelial cell health. Endothelium-Descemet membrane complex tissues were peeled from transplant suitable donor corneas. Protein fractions were isolated from each sample and subjected to multidimensional liquid chromatography and tandem mass spectrometry. Peptide spectra were matched to the human proteome, assigned gene ontology, and grouped into protein signaling pathways unique to each of the disease states. We identified an average of 12,472 unique proteins in each of the endothelium-Descemet membrane complex tissue samples. There were 2,409 differentially expressed protein isoforms that included previously known risk factors for type II diabetes mellitus related to metabolic processes, oxidative stress, and inflammation. Gene ontology analysis demonstrated that diabetes progression has many protein footprints related to metabolic processes, binding, and catalysis. The most represented pathways involved in diabetes progression included mitochondrial dysfunction, cell-cell junction structure, and protein synthesis regulation. This proteomic dataset identifies novel corneal endothelial cell and Descemet membrane protein expression in various stages of diabetic disease. These findings give insight into the mechanisms involved in diabetes progression relevant to the corneal endothelium and its basement membrane, prioritize new pathways for therapeutic targeting, and provide insight into potential biomarkers for determining the health of this tissue.

Femtosecond-Assisted Big Bubble: A Feasibility Study.

To evaluate the feasibility of femtosecond laser-assisted (FA) tunnel creation as a pretreatment for creating a big bubble (BB) to pneumo-dissect the corneal stroma from Descemet membrane. Five human cadaver eyes received pretreatment using a femtosecond laser. An intrastromal tunnel, along with a side cut, was achieved using customized femtosecond corneal disruption (custom mask). Before treatment, optical coherence tomography was performed and the intrastromal tunnel was intended to achieve a parallel orientation with respect to the corneal endothelial cell layer (50 µm above the endothelium). Surgical dissection of the side cut using a Sinskey hook was performed, followed by insertion of a deep anterior lamellar keratoplasty cannula into the tunnel and pneumo-dissection (BB). All corneas after treatment were prepared for histologic evaluation (light microscopy). FA pretreatment was successful in all 5 cadaveric corneas, and the BB was achieved in all eyes as well. Histologic evaluation of the corneas revealed complete separation of Descemet membrane and stroma in all eyes, with no remaining stroma attached to Descemet membrane and no signs of perforation. FABB seems feasible because pneumo-dissection of the corneal stroma from Descemet membrane was achieved in all human cadaver corneas of this experimental study. Optical coherence tomography, corneal histology, and macroscopic evaluation revealed complete Descemet-stromal separation.

Effects of Smoking on Central Corneal Thickness and the Corneal Endothelial Cell Layer in Otherwise Healthy Subjects.

The effects of smoking on central corneal thickness (CCT), corneal endothelial cell density (ECD), and morphology were evaluated in otherwise healthy subjects. The study included 103 current smokers and 106 healthy nonsmoking subjects without any eye disease apart from refractive errors. Endothelial cell density, percentage of hexagonality, and coefficient of variation (CV) in cell size were measured using noncontact specular microscopy. Central corneal thickness was measured by ultrasound pachymetry. The mean age of participants in the nonsmoker group was 31.4 ± 5.1 years (18-60) and 33.0±9.1 years (18-58) in the current smoker group. The mean CCT value was 523.7±34 μm in the nonsmoker group and 518.5±37 μm in the smoker group. The mean ECD, CV, and percentage of hexagonality values were 2,881±293.7 cells per square millimeter, 32.5±6%, and 56.6±11% in the nonsmoker group, and 2,681±323.9 cells per square millimeter, 33.4±5%, and 55.5±10% in the smoker group, respectively. Although there was no difference between the groups in terms of CCT, CV, and percentage of hexagonality values, a significant difference was determined in the case of ECD values[ZERO WIDTH SPACE][ZERO WIDTH SPACE] (P<0.001). The smoker group comprised 67 light smokers (65.0%) and 36 (35.0%) heavy smokers. Between these groups, there was no statistically significant difference in the mean values of CCT, ECD, CV, and the percentage of hexagonality. Although cigarette smoking has no effect on cell polymorphism and polymegethism, the results suggest that smoking reduces endothelial cell count.

Panoramic view of human corneal endothelial cell layer observed by a prototype slit-scanning wide-field contact specular microscope

PurposeTo observe the most peripheral region of the corneal endothelial cell (CEC) layer as long as optically recordable by use of a prototype slit-scanning wide-field contact specular microscope and produce...

High Throughput Assay Identifies Glafenine as a Corrector for the Folding Defect in Corneal Dystrophy-Causing Mutants of SLC4A11.

Protein misfolding, causing retention of nascent protein in the endoplasmic reticulum (ER), is the most common molecular phenotype for disease alleles of membrane proteins. Strategies are needed to identify therapeutics able to correct such folding/trafficking defects. Mutations of SLC4A11, a plasma membrane transport protein of the human corneal endothelial cell layer, cause cases of congenital hereditary endothelial dystrophy, Harboyan syndrome, and Fuchs' endothelial corneal dystrophy. Most SLC4A11 mutations induce SLC4A11 misfolding and retention in the ER. An assay amenable to high-throughput screening was developed to quantify SLC4A11 at the plasma membrane, enabling a search for potential traffic-correcting small molecules. The assay was validated by comparing cell surface abundance of SLC4A11 mutants measured in the assay to observations from confocal immunofluorescence and values from cell surface biotinylation. Functionality of mutant proteins was assessed, using a confocal microscopic green fluorescent protein (GFP) water flux assay where relative rates of cell swelling are compared. A small-scale screen revealed that the nonsteroidal anti-inflammatory drugs (NSAIDs), glafenine, ibuprofen, and acetylsalicylic acid dissolved in 0.2% dimethyl sulfoxide (DMSO), partially rescued the trafficking defect in some SLC4A11 mutants, expressed in HEK293 cells. These SLC4A11 mutants retained functional activity when rescued to the plasma membrane by glafenine treatment. Glafenine was effective with an EC50 of 1.5 ± 0.7 μM. These data suggest that glafenine, and perhaps other NSAIDs, hold potential as therapeutics for misfolded membrane proteins, like SLC4A11. The high throughput approach described here can be modified to identify correctors of other misfolded plasma membrane proteins that cause eye disease.

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

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

Measurement of corneal endothelial impedance with non-invasive external electrodes – A theoretical study

The corneal endothelial cell layer function is critical for the maintenance of hydration and transparency of the cornea. Recent advances in corneal lamellar transplantation point to the need for reliable, non-invasive and rapid endothelial function assessment. Findings using an invasive electrode in an experimental animal model have suggested an association between bioimpedance parameters and endothelial cell function. Currently, however there is no clinical device that allows for non-invasive measurements of endothelial layer electrical impedance. This report is a finite element simulation study that models the human eye. It evaluates the feasibility of using external non-invasive electrodes to detect changes in endothelial layer electrical properties as a function of electrode location and measurement frequencies. The findings show that the ratio between the potential recorded at low and high frequencies is sensitive to changes in endothelial resistivity as well as endothelial capacitance. Moreover, the optimal electrode configuration yielding the highest sensitivity is one where the current injecting electrodes are oppose to each other and the voltage recording electrodes are adjacent to the current injecting electrodes. This first-order theoretical study suggests that a non-invasive device which measures electrical properties of the endothelial layer from the exterior of the eye could be developed. Clearly further animal and human studies are required to develop a reliable clinical tool.

Endothelial Mesenchymal Transition: A Therapeutic Target in Retrocorneal Membrane

A single layer of corneal endothelial cells covers the posterior surface of the Descemet membrane. Normally, corneal endothelial cells do not proliferate, suggesting that factors inhibit their undergoing mitosis. Fibroblastic transformation of corneal endothelial cells due to syphilitic interstitial keratitis or alkali burn may result in stromal opacification. Various growth factors such as fibroblast growth factor 2 and transforming growth factor β are involved in "endothelial-mesenchymal transition (EnMT)." Endothelial wound-healing assay experiments revealed that cell migration toward artificial wound defect was mediated by p38 and c-Jun N-terminal kinase. To understand whether Smad signal might have an important role in EnMT regulation, gene transfer of Smad7 was employed to block transforming growth factor β/Smad signal in rat corneal endothelium 3 days before alkali burning. EnMT during healing interval after alkali burn was markedly suppressed by Smad7 overexpression associated with upregulation of cell proliferation. Therefore, blocking Smad signal effectively suppresses injury-induced EnMT and fibrogenic reaction by corneal endothelium without impairing repair of wound defect. Strategies that block Smad may be useful for prevention and treatment of fibrogenic disorders in the corneal endothelium.

Review of Corneal Endothelial Specular Microscopy for FDA Clinical Trials of Refractive Procedures, Surgical Devices, and New Intraocular Drugs and Solutions

Specular microscopy can provide a noninvasive morphologic analysis of the corneal endothelial cell layer from subjects enrolled in clinical trials. The analysis provides a measure of the endothelial cell physiologic reserve from aging, ocular surgical procedures, pharmaceutical exposure, and general health of the corneal endothelium. The purpose of this review is to discuss normal and stressed endothelial cell morphology, the techniques for determining the morphology parameters, and clinical trial applications.

Iridocorneo-endotheliales Syndrom (ICE-S): Klassifikation, Klinik und Diagnostik

The iridocorneal endothelial (ICE) syndrome includes progressive essential iris atrophy, the Cogan-Reese syndrome, Chandler's syndrome and mixed forms. The term ICE-S was proposed by Scheie and Yanoff in 1975 and by Yanoff in 1979. The capacity of migration of the abnormal corneal endothelial cell layer across the anterior chamber angle, and on to the anterior surface of the iris, possible on to the back surface of the iris and across the zonula fibers is responsible for corneal edema, secondary glaucoma, nevi, noduli and atrophy of the iris, and pupillary distortion. The contraction of the migrated membrane-like ICE tissue produces holes in the iris. The diseases are usually unilateral in young patients. The etiology is still not clear. Theories include membrane formation, low grade of inflammation and viral infection with Herpes simplex or Epstein-Barr virus. Glaucoma and edema of the cornea are the main therapeutic problems.

Long-Term Changes in Corneal Endothelial Morphology After Discontinuation of Low Gas-Permeable Contact Lens Wear

Low gas-permeable contact lens wear of polymethyl methacrylate or hydroxyethyl methacrylate material is known to cause morphologic abnormalities in the corneal endothelial cell layer. These lenses were widely prescribed and successfully worn until their use was actively discouraged in the late 1980s and early 1990s. This study was designed to investigate whether discontinuation of low gas-permeable contact lens wear leads to an improvement of corneal endothelial cell morphology. At the time of discontinuation and at least 5 years after discontinuation of low gas-permeable contact lens wear, noncontact specular photographs of the central corneal endothelium were made in 66 patients (14 male and 52 female, mean age 37.7 +/- 8.4, range 24.6-69.0). By computer analysis of endothelial photographs, parameters for polymegethism and pleomorphism were calculated, as well as cell density. Mean follow-up time between photographs was 6.8 years (SD 1.1). Sixty-one patients were refitted with rigid high gas-permeable contact lenses or high-water-content soft lenses, and 5 patients switched to spectacle wear. A small but significant recovery of the corneal endothelial cell morphology was found for the mean coefficient of variation of cell area, from 37.5 to 35.7 (P = 0.022), and for the coefficient of variation of the number of sides, from 13.1 to 12.4 (P = 0.004). The mean percentage of hexagonal cells increased from 54.2 to 56.2 (P = 0.013). Although the corneal endothelial cell morphology improved significantly on cessation of LGP contact lens wear, the values did not return to levels observed in normal, non-contact lens wearing individuals. During follow-up, the mean endothelial cell density decreased significantly (P = 0.001) from 2994 to 2890 (a 3.5% cell loss in 6.8 years), which is similar to the known normal age-related cell loss of 0.6% per year in non-contact lens wearing healthy individuals. Endothelial polymegethism and pleomorphism caused by PMMA or HEMA contact lens wear is partly reversible.