A comparison of corneal endothelial morphology in cornea guttata, Fuchs' dystrophy and bullous keratopathy

Imaging the Corneal Endothelium in Fuchs Corneal Endothelial Dystrophy

Fuchs endothelial corneal dystrophy (FECD) is characterized by the progressive degeneration of the corneal endothelium (CE). The purpose of this article is to review the diagnostic tools available to image and assess the CE in FECD. Slit-lamp biomicroscopy with specular reflection and retroillumination are important techniques to assess the CE. Objective diagnostic tests, such as retroillumination photographic analysis, specular microscopy, in vivo confocal microscopy (IVCM), and anterior segment optical coherence tomography, are valuable tools to evaluate the CE in FECD. Specular microscopy can be performed rapidly without touching the eye but requires a clear cornea with a smooth CE. In contrast, IVCM can image all layers of the cornea, even in advanced FECD. However, IVCM is contact-based and more technically challenging. It is important to select the appropriate objective diagnostic test to image and assess the CE in managing patients with FECD.

Regional variability in corneal endothelial cell density between guttae and non-guttae areas in Fuchs endothelial corneal dystrophy

OBJECTIVE

To assess the regional variability of corneal endothelial cell density (ECD) between guttae and non-guttae areas in subjects with Fuchs endothelial corneal dystrophy (FECD) using non-contact specular microscopy and confocal microscopy.

DESIGN

Retrospective chart review from 2009 to 2014 at the Massachusetts Eye and Ear Infirmary.

PARTICIPANTS

One hundred fifteen eyes of 73 subjects with FECD.

METHODS

Subjects with FECD underwent same-day specular and confocal microscopy in the same eye. Clinical stage of disease was documented on the day of image acquisition. Regional variability of ECD associated with guttae and non-guttae areas was assessed. Manual endothelial cell counts were performed.

RESULTS

Thirty-two percent of subjects had high quality endothelial images by both specular and confocal microscopy. Of these subjects, 83% were classified clinically as early-stage FECD. There was a significant association between stage of disease and the ability to obtain high quality specular images (χ²; p = 0.0012). There was no difference in mean ECD derived from specular (1363 ± 594 cells/mm²) or confocal (1391 ± 493 cells/mm²; p = 0.75) images. There was a statistically significant decrease of 31.8 ± 21.7% in mean ECD in areas surrounding guttae (1296 ± 560 cells/mm²) compared to non-guttae areas (1926 ± 674 cells/mm²; p < 0.0001) as determined by confocal microscopy.

CONCLUSION

These findings support confocal microscopy as an alternative to specular microscopy for evaluating the corneal endothelium of patients with FECD, especially those with advanced disease. Confocal microscopy also revealed regional differences in ECD in guttae and non-guttae areas in patients with FECD.

Objective assessment of the corneal endothelium in Fuchs' endothelial dystrophy

PURPOSE

To develop a standardized method of endothelial cell density (ECD) assessment in Fuchs' endothelial dystrophy that maximizes the sample area and uses the clearest endothelial cells in confocal images.

METHODS

The corneal endothelium of 51 eyes from 30 patients, with varying degrees of Fuchs' endothelial dystrophy, was examined using confocal microscopy. In two or three distinct images of the central endothelium, local contiguous cell density was determined using a variable frame method. The effective ECD was the product of the local cell density and the fraction of the image that was free of guttae. Two examiners assessed the severity of disease in each eye during slit-lamp examination and assigned a severity grade of 1 to 6. In a second group of 55 eyes with Fuchs' dystrophy from 30 patients, the clinical grade was predicted from the effective ECD and the regression coefficients of the first group and compared to the subjective clinical grade assigned by one examiner.

RESULTS

The effective ECD decreased linearly with subjective grade (r = -0.93, P < 0.001). The grade predicted from the effective ECD differed from the subjective clinical grade by -0.1 ± 0.8 (mean difference ± standard deviation).

CONCLUSIONS

The effective ECD in confocal images provides an objective means of assessing the corneal endothelium in Fuchs' dystrophy and might be a useful tool in clinical studies.

Assessment of the reliability of endothelial cell-density estimates in the presence of pseudoguttata

PURPOSE

The purpose of this work is to assess the reliability of endothelial cell-density (ECD) estimates in corneas with different severity pseudoguttata.

METHODS

Specular microscopy was undertaken on grade 1, 2, or 3 pseudoguttata patients and age-matched controls aged 52-83 years. On high magnification prints of central cornea, areas of complete cells (all sides visible) and partial 'cells' (one or more sides obscured) were measured manually. Sets of 45 complete cells were selected, as well as 75 cells that were a mixture of complete and partial cells on guttate endothelia. ECD was calculated by a progressive averaging technique.

RESULTS

Each group comprised 12 patients with similar range of ECD values (1,230-4,587 cells/mm(2)). Based on 40 complete cells, ECD could be estimated to within ±3.1% for grade 3 pseudoguttata versus ±2.0% for controls. If a mixture of complete and partial cells were measured, ECD could be estimated to within ±2.8% for grade 3 pseudoguttata images (n = 70 cells) and ±1.1% for controls. The estimated variability increases to substantial levels of ±20% if only ten cells were measured. No statistical differences in ECD were noted between guttate and normal endothelia if only complete cells were measured, but could be different if partial 'cells' were included.

CONCLUSIONS

Providing adequate numbers of complete cells are measured and in the absence of obvious polymegathism, ECD estimates can be made to within around ±3% in the presence of typical but significant pseudoguttata.

Central corneal thickness and intraocular pressure measures in human corneas with endothelial guttata: an observational quality control study

PURPOSE

The aim of the present study was to assess central corneal thickness (CCT) and intraocular pressure (IOP) in eyes where the corneas were affected by different degrees of severity of endothelial pseudo-guttata or guttata.

METHODS

In a prospective, case series observational study, non-contact tonometry and non-contact specular microscopy (NCSM) with pachymetry for central corneal thickness measures were undertaken as routine procedures on predominantly older patients without a history of corneal problems or contact lens wear. For those showing any signs of corneal endothelial abnormalities, images of the central cornea endothelium were further processed to measure the area (as a percentage) occupied by the guttata.

RESULTS

Abnormal endothelial images were obtained from 43 patients (seven with bilateral changes) with an average age of 67.5 years. Between 1.5 and 54.9 per cent of the endothelial images were affected by guttata, which were assigned grade 1 (20 eyes), grade 2 (18 eyes) or grade 3 (11 eyes). When assessed by grade, the central corneal thickness increased and the measured IOP decreased as the guttata became more numerous and confluent. Regression analyses revealed only a weak association between central corneal thickness (p = 0.044, r = 0.149) or the measured IOP (p = 0.090, r = -0.244) and the extent of the guttata (percentage). With the apparently contrasting IOP and central corneal thickness effects, no significant IOP-CCT relationship was noted (p ≥ 0.268, r ≤ 0.160).

CONCLUSIONS

Where corneas have mild-to-modest non-dystrophic endothelial guttata, there may be a less predictable effect of corneal thickness on the outcome of tonometry.

Adhesion molecule expression in bullous keratopathy

BACKGROUND

Adhesion molecules may play an important role in the pathogenesis of bullous keratopathy.

METHODS

The expression of the integrin VLA-beta 1, alpha-subunits of the beta 2-integrins LFA-1, Mac-1, and p150,95, the members of the immunoglobulin family ICAM-1 and VCAM-1, and the selectin ELAM-1 on corneas with bullous keratopathy (BK) secondary to intraocular surgery was studied immunohistochemically using an APAAP method.

RESULTS

In the corneas with BK (in contrast to normal corneas), a downregulation of VLA-beta 1 was observed throughout the corneal tissues, particularly on the epithelial layer where bullae occurred; ICAM-1 was induced on epithelial membranes in both BK and inflamed corneas; and the expression of beta 2-integrins, VCAM-1 and ELAM-1 was upregulated in some specimens with remaining endothelial cells.

CONCLUSION

The results show that the investigated adhesion molecules may participate in the pathogenesis of BK. The decrease in VLA-beta 1 in patients with BK may be an important factor in the occurrence and development of recurrent bullae; the induced ICAM-1 may recruit beta 2-integrin-positive leukocytes into the epithelial layer, thus aggravating epithelial damage; and beta 2-integrins and VCAM-1 may play a role in endothelial injury and decompensation.

EGF and PGE2: effects on corneal endothelial cell migration and monolayer spreading during wound repair in vitro

In vivo repair of the adult human corneal endothelium occurs mainly by movement of cells into the wound defect rather than by cell division. Two forms of cell movement contribute to endothelial wound repair: migration of individual cells into the defect and spreading of the confluent monolayer into the wound area. This laboratory has developed a tissue culture model using rabbit corneal endothelial cells pretreated with the mitotic inhibitor 5-fluorouracil to mimic the relatively amitotic state of human corneal endothelium in vivo. This model permits study of the effects of growth factors and other agents on individual cell migration and monolayer spreading in response to wounding. mRNA for epidermal growth factor (EGF) and its receptor has been detected in cultured corneal endothelial cells and EGF receptors have been detected on human corneal endothelial cells in situ, suggesting that this growth factor may act in an autocrine manner. Prostaglandin E2 (PGE2) is synthesized by cultured corneal endothelial cells and is present in relatively high quantity in aqueous humor in response to corneal wounding and to inflammation in the anterior chamber. Although corneal endothelial cells may be exposed to both EGF and PGE2, little is known about their effects on monolayer repair. The current study compared the effects of PGE2 alone, EGF alone, and both agents in combination on individual cell migration and monolayer spreading using the wound model system and also determined the effect of EGF on PGE2 secretion using a commercial immunoassay. A 15 min exposure of wounded cultures to exogenous PGE2 stimulated individual cell migration and suppressed monolayer spreading.(ABSTRACT TRUNCATED AT 250 WORDS)

The preoperative assessment of the corneal endothelium

The ability of the cornea to maintain its transparency after surgery depends primarily upon the integrity of the corneal endothelium and in corneal grafting this is important for both donor and recipient eyes. The corneal endothelium may be significantly affected in various conditions of the anterior segment, especially if these exist over a considerable period of time. These conditions include superficial keratopathy, long-term contact lens wear, cornea guttata and low-grade anterior uveitis, especially chronic cyclitis which may be almost imperceptible clinically. The suitability of such corneas for use as donor material as well as the response of the eyes to anterior segment surgery can be assessed by specular microscopy and this may become even more important in the future as long-term contact lens wearers become more numerous in the community.

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.