Pathogenesis of corneal oedema associated with herpetic eye disease.

Corneal oedema and stromal disease, induced in rabbits by intrastromal injection of herpes simplex virus, type 1, strain RE (HSV-1, RE), reached a peak of 12-15 days after infection. Corneal oedema as measured by ultrasonic pachymetry, and stromal disease as measured by a subjective scoring system, were closely related for 30 days after infection. Morphometric analysis of wide field specular micrographs showed that no immediate endothelial cell damage occurred in either control or HSV-1 infected corneas. Alizarin red S staining of corneas taken during the period of most severe oedema indicated no significant endothelial cell loss; however, visual inspection indicated numerous staining abnormalities. Scanning and transmission electron microscopy provided evidence of an intact endothelial layer possessing integrated infiltrating cells. Virus antigen could not be detected on endothelial cells by immunoperoxidase staining at any time during development of corneal oedema. The results indicate that corneal oedema associated with HSV-1 induced disease can occur in the absence of detectable virus replication and cytolysis of corneal endothelial cells.     

Histopathological analysis of corneal endothelial polymegethism.

The corneal endothelium from six humans (three contact lens wearers and three non-contact lens wearers) was examined. Scanning electron microscopy confirmed endothelial polymegethism. Observations with the transmission electron microscope showed that an oblique reorientation of the lateral walls of the endothelial cells had occurred in the contact-lens-wearing group of corneas. The endothelium of the contact lens wearers also showed some inter- and intracellular edema but were otherwise of a healthy appearance containing normal organelles. The oblique reorientation of the lateral wall of the endothelial cell allows for the possibility that a cell with a large anterior surface area may have a small posterior surface area or vice versa. Thus, polymegethous cells may not vary in cell volume. This hypothetical alternative to current theories of contact lens-induced polymegethism should be explored in future research.     

Effects of posterior chamber lens implantation on the endothelium of transplanted corneas

AIMS—The morphological changes of the corneal endothelium after posterior chamber lens implantation in the transplanted corneas were investigated.
METHODS—36 patients underwent extracapsular cataract extraction with posterior chamber lens implantation. Among these, penetrating keratoplasty had been performed in 18 patients before cataract surgery. The indications for penetrating keratoplasty in these cases included keratoconus, herpetic keratitis, and macula cornea. 18 cataract patients with normal corneas were also studied as controls. The central corneal endothelium in each subject was examined with a wide field specular microscope at a few days before and 3 months after cataract surgery.
RESULTS—Although the transplanted corneas showed lower endothelial cell densities, marked polymegethism, and pleomorphism in the baseline variables, the endothelial morphological changes in the transplanted corneas after posterior chamber lens implantation were comparable with those in the normal corneas. Also, there was no clinical evidence, especially, of corneal epithelial and/or endothelial rejections and corneal decompensation in all corneas.
CONCLUSION—Even though the transplanted corneas have a lower endothelial cell density and marked polymegethism, it is believed that cataract surgery does not induce corneal decompensation in cases where the peripheral recipient endothelium can be considered to have normal morphology.

     

Confocal microscopy in the iridocorneal endothelial syndrome

AIMS: To report the appearances of iridocorneal endothelial (ICE) syndrome from real time, white light confocal microscopy. METHODS: Three consecutive patients, each with ICE syndrome, were examined prospectively. Corneal specular and confocal microscopic examinations were performed in all three patients. In the first patient, a penetrating keratoplasty was performed and the cornea was examined by light and scanning electron microscopy. No surgery was performed in the remaining two patients. RESULTS: In the first patient corneal oedema prevented endothelial specular microscopy. Confocal microscopy performed before penetrating keratoplasty successfully revealed abnormal epithelial-like endothelial cells. Histological examinations of the cornea following penetrating keratoplasty revealed the presence of multilayered endothelial cells with epithelial features (microvilli). In the remaining two patients, specular microscopy showed the presence of ICE cells with typical dark/light reversal. Confocal microscopy demonstrated groups of endothelial cells with epitheloid appearances. In all three patients, the contralateral endothelial appearance was normal by specular and confocal microscopy, except for moderate endothelial polymegathism in one patient. Epithelial-like endothelial cells were characterised by prominent nuclei on confocal microscopy. CONCLUSIONS: The application of confocal microscopy indicates that the ICE syndrome is characterised by epitheloid changes in the endothelium. Confocal microscopy may be used to diagnose the ICE syndrome by demonstrating epithelial-like endothelial cells with hyperreflective nuclei. This technique is especially of value in cases of corneal oedema, since specular microscopy may fail to image the endothelium in such cases.     

长期配戴软性角膜接触镜对角膜内皮细胞的影响

目的 评价长期(≥10年)持续配戴软性角膜接触镜(SCL)对角膜内皮细胞的影响,更好地长期持续配戴SCL者进行眼病治疗及内眼手术前的评估.方法 利用非接触式角膜内皮显微镜(TOP-CON SP-2000P),观察长期配戴SCL的98只眼角膜内皮细胞的改变.同年龄组无其他疾患非戴SCL近视眼的角膜内皮细胞参数作为对照观察.结果 长期持续配戴SCL组角膜内皮细胞密度为2516.58±311.77,角膜内皮细胞面积变异系数(CV)为28.10±3.76,角膜内皮六角形细胞比例(6A%)为(48.90±6.10)%,与无SCL配戴史组比较差异均有统计学意义(P=0.02,P＜0.01,P＜0.01).结论 长期持续佩戴SCL组与无SCL佩戴史组对比在角膜内皮细胞数量和形态上的差异均有统计学意义,相比之下长期持续佩戴SCL对CV和6A%的影响更为显著.因此对长期持续配戴SCL患者进行可能引起内皮细胞损失的眼疾治疗和手术时应选择合理的药物和相对安全的手术方式,避免角膜内皮失代偿的发生.同时也建议近视患者尽量避免长时间持续佩戴SCL以保证角膜内皮的健康.

Abstract：

Objective To investigate long term effects (≥ 10years) of soft contact lens (SCL) wear on the corneal endothelium in order to evaluate the risk before a treatment and an operation better.Methods Non-contact specular microscopy (TOPCON SP-2000P) was performed on long-term (≥ 10years) SCL wearers and the control group.Results After more than 10 years SCL wearing,cell density was 2516.58± 311.77,CV was 28.10± 3.76 and 6A% was (48.90± 6.10)%.There was statistically difference (P =0.02,P ＜0.01,P ＜0.01) compared with those of the control.Conclusion Long-term soft contact lens wear produce cell loss and cell shape change,and the cell shape changes are more remarkable.We should choose safer surgery and medicine for the patients with long-term soft contact lens wear.At the same time,we also suggest that myopia sufferer should avoid wearing SCL consistently for a long term.     

Corneal response to rigid contact lens wear.

Three adult rhesus monkeys were subjected to 2 and 24 hours of polymethylmethacrylate (PMMA) contact lens wear. The induced corneal changes were examined with the electron microscope. Mild epithelial oedema as well as early degenerative cell changes was present already after 2 hours' wear. Rigid lens wear for 24 hours produced more severe oedema and cell alterations together with premature cell loss and ultimately, in areas of lens bearing, corneal denuding. Only the monkeys wearing contact lenses for 24 hours had significant stromal swelling, which was primarily evident in the posterior region, while the anterior limiting lamina remained unaffected. The stromal swelling was patchy and mainly around keratocytes and between lamellae, while fluid within the lamellae was evident only occasionally in posterior stroma. Changes among keratocytes were evident, especially posteriorly, where reaction was frequently severe. Endothelial reaction was restricted to a limited fluid uptake in the 24-hour-wear experiment. In addition there was in these monkeys an apparent loosening of the endothelial adhesion to the posterior limiting lamina. It is concluded that the oedematous epithelium undergoes cell shrinkage and flattening, which is compensated for by an uptake of fluid. The uptake of fluid maintains the overall normal thickness of the epithelium. The conclusion is supported by other studies, where the normal thickness of oedematous epithelium has been shown by pachometry. The results in the present study further suggest that stromal oedema in the contact lens wearer is a result of a relative loss of endothelial function, leading to a swelling that moves in a posterior to anterior direction.     

Quantitative analysis of wide-field specular microscopy. II. Precision of sampling from the central corneal endothelium

The precision of the measurement of mean endothelial cell area obtained by sampling with small-field and wide-field specular microscopy from the central 4 mm of human corneal endothelium was studied by comparing endothelial cell parameters from individual specular micrographs in vivo to the results obtained by montaging the micrographs from the entire central 4 mm of the same corneas. The small samples were at least 10% from the true mean cell size of all cells of the central 4 mm in any endothelium other than that with the most homogeneous pattern. A new algorithm for sampling with these two specular microscopes will need to be derived to permit a more precise measure of the mean area of endothelial cells in the central 4 mm of the human corneal endothelium.     

The correction of aphakia in infants with hydrogel extended-wear contact lenses. Corneal studies

Although hydrogel extended-wear contact lenses (EWCLs) have been used extensively in the correction of aphakia in neonates, little is known about the effects of these lenses on infant corneas. Recent studies have demonstrated that long-term contact lenses can induce endothelial morphometric changes, including an increased coefficient of variation (CV) of mean endothelial cell area. Using wide-field specular microscopy, the authors studied 11 eyes of 10 patients, 1 to 3 years of age who, after lensectomy for congenital cataracts, wore EWCLs for the correction of aphakia. Except for two corneas in which increased pachometric readings and CV developed after repeated episodes of lens loss and inflammation, the EWCL were well tolerated and associated with few complications in this study.     

Confocal microscopic observations of the human cornea following overnight contact lens wear

Background: Striae and folds are observed with a slidamp biomicroscope in the cornea following overnight contact lens wear. These phenomena are poorly understood. The aim of this study is to employ confocal microscopy to observe and document these and other morphological changes in die human cornea following overnight contact lens wear. Methods: Slitlamp biomicroscopy, slit‐scanning confocal microscopy and ultrasonic pachometry were performed on both eyes of 13 subjects (3M, 10F, age 24 ± 3 years) before and after eight hours overnight wear of a ‐3.00 D Bausch & Lomb one day disposable soft contact lens (Dk/t = 15.1 times 10^‐9 (cm/sec) x {ml O²/ml x mmHg)) in one eye; the other non‐lens‐wearing eye acted as a control. Results: Following sleep, both corneas were swollen (lens‐wearing eye 11.8 ± 3.8 per cent; control eye 2.1 ± 1.9 per cent) and the stroma of both corneas displayed an apparent reduction in keratocyte density (lens‐wearing eye 21 per cent; control eye 10 per cent). Folds were observed with the slidamp biomicroscope and long, straight, dark, orthogonal lines were observed widi die confocal microscope, in the posterior stroma of the oedematous lens‐wearing eyes. Such features were not observed in die control eyes. The keratocytes appeared less distinct with greater levels of corneal oedema. Conclusion: The apparent loss of keratocytes following overnight lens wear is an optical artefact that can be explained in terms of corneal oedema causing volumetric tissue expansion and a loss of optical clarity, which hampers keratocyte detection. These findings place the onus on researchers postulating a loss of stromal keratocytes following clinical interventions, such as contact lens wear, to account for the effects of oedema.     

Morphometric analysis of the corneal endothelium. Specular microscopy vs. alizarin red staining

Computer-assisted analysis of endothelial morphology provides useful indices of cell shape and size which appear to correlate to the monolayer's functional status. In this study morphometric data obtained by wide-field specular microscopy of in situ corneal endothelia are compared to data obtained by alizarin red S staining of excised corneas. Both human donor corneas and rabbit corneas were studied. The results of the study indicate that considerable (14%) cell shrinkage occurs in rabbit endothelia following staining. Associated with this cell shrinkage is a normalization of cell area which is manifest as a significant (P less than 0.001) decrease in the coefficient of variation of cell area. The percentage of hexagonal cells, however, remains unchanged. These changes were not mitigated by lowering the osmolality of the saline rinse following staining or by minimizing evaporation by placing a drop of silicone oil on the stained button. In human tissue no significant differences in cell area or cell shape were noted in comparing morphometric data obtained by staining to that obtained from specular microscopy. Useful morphometric data can be obtained by alizarin staining. This technique combined with cell morphometric analysis could provide valuable data in corneas whose lack of clarity limits or precludes specular microscopy. Caution, however, must be exercised in comparing morphometric data by this method to those obtained in situ for rabbit tissue.     

Clinicopathologic features of Chandler's syndrome

The clinicopathologic features of Chandler's syndrome are elucidated based on a study of nine patients. Keratoplasty, trabeculectomy and/or iris specimens were studied by light, electron and, in six cases, specular microscopy. The prominent pathologic features were abnormalities of the endothelially-derived cells lining the posterior corneal surface, the inner surface of the trabecular meshwork, and the anterior iris surface. In all four corneal buttons, the endothelium was diffusely attenuated and focally absent, and posterior collagen layers were present. Extension of the endothelial cell layer and Descemet's membrane deposition over the trabecular meshwork were observed in two trabeculectomy specimens, and similar proliferation onto the anterior surface of the iris was evident in four iris specimens. Other abnormalities of the endothelial cells included increased intracytoplasmic filaments. These pathologic alterations are consistent with the concept of Chandler's syndrome as representing one variant of the iridocorneal endothelial (ICE) syndrome. Interestingly, although both endothelial proliferative and degenerative responses can be observed in Chandler's syndrome, their occurrence within the same eye is apparently not simultaneous.     

Endothelial damage associated with intraocular lenses.

We examined the corneal endothelium of five patients with the clinical specular microscope before and at intervals after combined cataract extraction and intraocular lens implantation. There was a severe loss of endothelial cells postoperatively in all five patients despite clear, thin corneas. We observed no significant endothelial regeneration (increased number of cells) or continued cell loss during 15 weeks of postoperative observation. The clinical specular microscope was useful in assessing the endothelial effects of ocular surgical procedures.     

Cellular changes in transplanted human corneas

PURPOSE: To measure endothelial cell and keratocyte densities in transplanted corneas and the changes in these densities with time. METHODS: The endothelia of 500 consecutive penetrating corneal transplants were studied longitudinally by specular microscopy for 10 to 20 years. The keratocytes of 36 corneal transplants that varied in postoperative times from 1 month to 20 years were studied cross-sectionally by clinical confocal microscopy. The keratocytes of five transplanted corneas were studied longitudinally by confocal microscopy at 1 day, 1 week, and 1 month postkeratoplasty. RESULTS: Endothelial cell density decreased progressively at an accelerated rate for 20 years after transplantation, with concurrent increases in the coefficient of variation of cell area and corneal thickness and decreases in the percentage of hexagonal cells. Grafts with insufficient endothelial cells developed late endothelial failure, which was the primary cause of graft failure after the first 5 postoperative years. The grafts with late endothelial failure did not lose endothelial cells faster than grafts that did not fail, but instead had fewer cells immediately after transplantation, diminishing to a critically low cell density earlier. The keratocyte density was also decreased in transplanted corneas. Keratocytes became "activated" during the first week after keratoplasty and in grafts with late endothelial failure. CONCLUSION: It should be possible to prevent or delay late endothelial failure, the primary cause of graft failure, by increasing the number of endothelial cells on transplanted corneas. The status of the keratocytes appears to affect corneal transparency and, thus, visual quality in the grafted eye.     

THE USE OF SPECULAR MICROSCOPY TO INVESTIGATE UNUSUAL FINDINGS IN THE CORNEAL ENDOTHELIUM AND ITS ADJACENT STRUCTURES

The use of specular microscopy is not confined to the corneal endothelial mosaic, but may be used at any level through the corneal stroma to the posterior endothelial surface. In the stroma the not very dense, irregularly rounded deposits of corneal dystrophies may be differentiated from the dense, geometric shapes of crystalline deposits. At the level of Descemet's membrane the fine parallel lines of tears in Descemet's are distinct from the multiple fine vertical deep stromal lines seen in advanced keratoconus. At the level of the endothelial mosaic the cells may be counted and their morphology examined, while blebs may also be seen in a wide variety of pathological conditions including superficial keratopathies, contact lens wearers, deep keratopathies, anterior uveitis and contusion injury. These blebs vary in size in different conditions and are often transient. They must be distinguished from guttae which are permanent and although an occasional finding in normal corneas are a constant feature of cornea gutatta and Fuchs' dystrophy. On the posterior endothelial surface the relief mode enables the examination of numerous deposits including red blood cells, white blood cells, keratitic precipitates, pigment granules and pseudoexfoliative KP. The morphology of these various findings is discussed.     

Relocation of posterior corneal rings in clinical wide field specular microscopy

A clinical study of posterior corneal rings in human eyes was undertaken using the Pocklington (Keeler-Konan) contact wide field specular microscope designed by Sherrard. The method used to reproduce identical posterior corneal rings in the same human cornea, in vivo, using the contact wide field specular microscope camera, without the aid of a contact lens, is described. The technique enables the clinician to relocate and evaluate a selected area of human endothelial cells in the same eye.     

RELOCATION OF POSTERIOR CORNEAL RINGS IN CLINICAL WIDE FIELD SPECULAR MICROSCOPY

A clinical study of posterior corneal rings in human eyes was undertaken using the Pocklington (Keeler-Konan) contact wide field specular microscope designed by Sherrard.
The method used to reproduce identical posterior corneal rings in the same human cornea, in vivo, using the contact wide field specular microscope camera, without the aid of a contact lens, is described. The technique enables the clinician to relocate and evaluate a selected area of human endothelial cells in the same eye.     

Specular and scanning electron microscopy in diffuse silicone keratopathy

In a 50-year-old man, penetrating keratoplasty was carried out to treat a diffuse silicone keratopathy that developed 2 years after a pars plana vitrectomy combined with an intravitreal silicone injection for a complicated retinal detachment in the only aphakic eye. At 2 weeks after the intravitreal silicone injection, specular microscopy revealed a mild pleomorphism in the corneal endothelium and an endothelial cell loss of 26%. After 5 months, a small silicone drop floated in the anterior chamber and the first signs of diffuse keratopathy were observed. At the same time, specular microscopy revealed severe damage to the endothelial cells and a cell loss of 69%. After the keratoplasty, scanning electron microscopy of the corneal button showed a filamentous structure of the posterior surface of the cornea, with fibroblast-like cells; the endothelial cells were absent.     

Two cases of posterior keratoconus

We studied 3 eyes from 2 patients with posterior keratoconus. One patient (a 17-year-old female) had posterior keratoconus bilaterally and the other (a 8-year-old male) had posterior keratoconus in one eye and Peters' anomaly in the contralateral eye. Slit-lamp biomicroscopy disclosed localized thinning with stromal haze underlying the endothelium in the central cornea. Photokeratoscopy revealed no abnormalities suggestive of anterior keratoconus. Wide-field specular microscopy showed the endothelial cells with normal cell density (approximately 3500 cells/mm2) and morphology in both the peripheral and central corneas (adjacent to the hazy areas).     

Morphologic evaluation of Descemet's membrane and corneal endothelium in diabetes mellitus

Diabetes mellitus is characterized by abnormally thickened basement membranes throughout the body and the eye. In addition, abnormal corneal endothelial cell morphology has been found in eyes of diabetics. The authors examined Descemet's membrane (the basement of the corneal endothelium) and the endothelial cells in 19 diabetic corneas and 19 age-matched nondiabetic normal corneas in a masked fashion by transmission electron microscopy and specular microscopy. No statistically significant quantitative or qualitative differences were found between the two groups.     

A morphologic and fluorophotometric analysis of the corneal endothelium in long-term extended wear soft contact lens wearers

Eleven extended wear soft contact lens wearers with an average of 4 years of wear underwent corneal fluorophotometry and quantitative specular microscopy. Compared to age-matched controls, a significant increase in mean endothelial permeability was found in the contact lens group, indicating a defect in their endothelial barrier function. A significant increase in the mean endothelial pump rate was also noted in the contact lens group. In addition, mean corneal thickness was significantly greater in the contact lens group. No significant difference was noted between the two groups in mean cell area and figure coefficient; however, the coefficient of variation was significantly higher in the contact lens group. Duration of contact lens wear correlated positively with coefficient of variation. An inverse correlation was noted between contact lens oxygen transmissibility and cell area, as well as corneal thickness. These data suggest both a morphologic and functional defect in the corneal endothelium of long-term extended wear soft contact lens wearers.