Peripheral corneal oedema following cataract extraction (Brown-McLean syndrome).

We describe the clinical features of 21 eyes of 15 patients who developed peripheral bullous corneal oedema following cataract extraction. The peripheral oedema was asymptomatic in all cases and was only noted at a review examination. Although the onset of the peripheral oedema was probably delayed for several years after surgery, it was not documented to progress in any patient or to involve the central cornea. Endothelial specular microscopy did not reveal any endothelial features that are specific for this condition, but confirmed that the central endothelial cell density can be as high as 2150 cells/mm2 in the presence of peripheral corneal decompensation. Despite the surface irregularity resulting from the peripheral corneal oedema 12 patients (18 eyes) continued to wear contact lenses to correct their aphakia.

The posterior corneal surface in posterior polymorphous dystrophy: a specular microscopical study.

Forty-eight cases of posterior polymorphous dystrophy (PPD), diagnosed on the presence of classic vesicles at the level of Descemet's membrane, were studied with the specular microscope. Vesicles alone occurred in 42% and were present in conjunction with PPD bands in 48% and a diffuse abnormality of Descemet's membrane in 10%. It was notable that none of the cases showed ocular abnormalities other than those of the cornea. Endothelial specular photomicroscopy (ESP) revealed distinctive characteristics of PPD vesicles and bands that distinguish them from other posterior corneal abnormalities, e.g., the iridocorneal endothelial syndrome and Haab's striae, which can appear similar at the slit lamp level. The interpretation of the ESP images was that vesicles are pits and bands are trenches in Descemet's membrane only. The endothelium was composed of enlarged cells in almost all cases. Other endothelial abnormalities reported by previous observers were not found. There was evidence that the affected corneas of children were more rigid than normal, and this is discussed in relation to the aetiology of the lesions of PPD.

On the morphology of cells of posterior cornea in the iridocorneal endothelial syndrome.

The iridocorneal endothelial (ICE) syndrome is potentially a blinding condition as a result of glaucoma and/or corneal decompensation. The basic pathology seems to be in the corneal endothelium, which many studies confirm takes on a characteristic slit lamp appearance of hammered silver and image reversal with the specular microscope. The origin and morphology of the abnormal cells are unknown. Many histopathological studies of keratoplasty and trabeculectomy specimens reveal as many cell types. This paper reports some general and specular microscopical data from 57 cases of the syndrome, argues that the reason for the variety of histopathological findings in other studies is due to poor sampling of the study material, deduces the morphology of the abnormal cells on specular microscopical criteria, and compares the specular and scanning electron microscopical images in one case with those of other reports. It is tentatively concluded that the appearance of the abnormal cells is a function of their three-dimensional shape and that they produce blister-like vesicles that rupture, collapse, and eventually invaginate.

Distinguishing features of the iridocorneal endothelial syndrome and posterior polymorphous dystrophy: value of endothelial specular microscopy.

The literature suggests that posterior polymorphous dystrophy (PPD) may show features such as iridocorneal adhesions, glassy membranes, and pupillary ectropion which are typically ascribed to the iridocorneal endothelial (ICE) syndrome. This complicates diagnosis. PPD, unlike ICE, is familial, and ICE, unlike PPD, is usually progressive and frequently complicated by glaucoma: thus it is important to distinguish between them. To determine whether this could be achieved by specular microscopy, since the posterior corneal surface is abnormal in both conditions, 57 cases of ICE and 44 of PPD were repeatedly examined and photographed with the specular microscope. Progressive and/or static morphological features of the corneal endothelium and Descemet's membrane were found that were specific for each condition. Specular microscopy can thus provide a definitive diagnosis of ICE or PPD even in uncertain cases.

Manipulative damage to the endothelium of infant and adult donor corneas.

Six human donor corneas were studied with the scanning electron microscope to quantify the hazards to the endothelium during the excision of corneoscleral buttons. Although the number studied was small, it was found that: (1) striae were more numerous in the flaccid, very young, donor corneas (under 1 year old) than in the more rigid adult corneas: (2) iridocorneal endothelial touch can result in loss of the posterior membrane and death of the touched endothelial cells. This corroborates the findings of other investigators. Both findings are important, because these conditions reduce the quality of the donor cornea for transplantation.

The other side of the corneal endothelium.

New high-magnification biomicroscopes, the specular microscope and now the in-tandem confocal microscope, provide new images of the corneal endothelium in vivo. These are not always easy to interpret, and correlation with the morphology of the endothelium as seen in dead, fixed specimens is necessary. One such image is of the anterior surface with the confocal microscope. It exhibits a mosaic of hexagonal cells. This surface has not been specifically investigated previously in fixed preparations and the in vivo appearance does not correlate with the structure deduced from transmission electron micrographs. These indicate that the bases of endothelial cells are in the form of thin processes that would not present an image of clearly defined cell outlines. Therefore, the anterior surface of corneal endothelium stripped from ox and human corneas has been examined with the scanning electron microscope. It was found that the basal cell membranes extend processes to neighbouring cells and that some of these seem to unite. The possibility that these findings are artefactual has been examined by comparing them with published transmission and scanning electron micrographs, and it has been concluded that the processes of the basal cell membranes are real.

Posterior corneal folds and endothelial cell damage in human donor eyes.

Posterior folds in human donor corneas stored as whole eyes in moist chambers, or isolated in McCarey-Kaufman medium at 4 degrees C, have been studied by light and scanning electron microscopy to determine whether or not endothelial cells on the folds are damaged. Extensive, often irreversible cell damage was found associated with most of the folds. Hence posterior folds in donor corneas are of importance in that they indirectly reduce the quality of the donor cornea for transplantation.

The infant corneal endothelium.

Specular microscopy of the in vivo corneal endothelium of 48 clinically normal eyes of 31 infants less than 1 year old revealed a regular mosaic of small cells. The cell population density of individuals varied greatly, as it does in age-related adults. Reexamination of five eyes indicated a reduction of the cell population density during the first year. This change could be accounted for by corneal growth in the absence of endothelial mitoses and not necessarily by true cell loss. There were morphologic indications of mitoses, but their interpretation is open to doubt.

Neodymium: YAG laser iridotomies--short-term comparison with capsulotomies and long-term follow-up.

This study addresses three aspects of anterior segment Nd:YAG laser treatment--acute endothelial damage, as assessed by endothelial specular photomicrography (ESP), acute and long-term intraocular pressure (IOP) changes, and long-term iridotomy patency. The acute ESP and IOP changes in 26 eyes (21 patients) after Nd:YAG laser iridotomies were compared to 39 eyes (37 patients) after Nd:YAG laser capsulotomy. Similar endothelial damage occurred in both groups, although less damage was noted in the group of 9 eyes in which capsulotomies were undertaken in the presence of an intraocular lens. In a parallel study 53 eyes (44 patients) were followed for a mean of 83 weeks (19 months) from the time of Nd:YAG iridotomy. There were no late closures and no late rises in IOP. The level of acute IOP rise after treatment did not predict long-term IOP. We conclude that Nd:YAG iridotomy is an effective procedure in the long-term, and that both iridotomy and capsulotomy are accompanied by noteworthy acute endothelial changes and intraocular pressure rises.

Postoperative grey-white lines of the posterior cornea and endothelial cell damage.

'Snailtracks' (grey-white streaks and patches on the posterior corneal surface which occur postoperatively) have recently been implicated as possible markers of corneal endothelial cell damage. We have examined this phenomenon in vivo with the slit-lamp and specular microscope. We recognised three types of linear form and, in contradiction of other observers, found that each was always coincident with a wrinkle in Descemet's membrane. Moreover, we were able to demonstrate only minimal endothelial cell damage in only a few of the tracks.

Age-related changes of the corneal endothelium and stroma as seen in vivo by specular microscopy.

Two age-related changes of the human cornea are revealed in vivo by specular microscopy, (1) loss (and enlargement) of endothelial cells and (2) wrinkling of the posterior corneal layers when the cornea is applanated. A comparison of the rate of loss of cells and the effect upon the morphology of the endothelium as determined in several studies, indicates that cell loss and enlargement are rapid in the first year of life, slower up to the age of about 25 years, and fairly stable thereafter. In some individuals the remaining cells appear to enlarge regularly and in others irregularly. Posterior wrinkles on applanation of the cornea occur in the adult cornea only, and suggest an increasing rigidity of the stroma with increasing age.

Air, methylcellulose, sodium hyaluronate and the corneal endothelium. Endothelial protective agents.

In a randomised trial the endothelial protective agent used during extracapsular cataract extraction and intraocular lens insertion was air in 19 eyes (group 1), methylcellulose in 25 eyes (group 2) and sodium hyaluronate in 22 (group 3). The cell population densities of each eye were estimated immediately before and three months after the operations to determine the degree of cell loss. Eyes showing mechanical (touch) damage on the second postoperative day were eliminated. The numbers of eyes in each group which showed a statistically significant cell loss were compared, and the mean cell losses in each group were tested for significant differences. It appears that air actually damages the endothelium while methylcellulose and Na-hyaluronate are not harmful, and afford a high, essentially equal degree of endothelial protection.

Corneal endothelial changes following short pulsed laser iridotomy and surgical iridectomy.

Pre- and post-operative endothelial specular photo-microscopy was performed on 46 eyes of 29 patients who had been randomly assigned to iridotomy with the Nd:YAG or the dye laser, or to surgical peripheral iridectomy for the relief of pupil block glaucoma. Localised damage to the endothelium was observed in two eyes following Nd:YAG laser iridotomy and in one eye following dye laser iridotomy. No endothelial changes were recognised after surgical peripheral iridectomy. Central corneal endothelial cell densities remained unchanged following all procedures.

Damage to the corneal endothelium during Nd/YAG photodisruption.

Damage to the human corneal endothelium, as seen by specular microscopy, associated with short pulsed neodymium: yttrium-aluminium-garnet (Nd/YAG) laser iridotomy and capsulotomy, is described. A specular and scanning electron microscopical study of fresh in vitro rabbit eyes submitted to Nd/YAG iridotomy was performed to investigate the nature of the endothelial damage. The majority of lesions showed irreversible changes ranging from individual cell destruction to disruption of large areas of the endothelium, while cells adjacent to these lesions had changes of an apparently reversible nature. It was possible to correlate accurately these scanning electron microscopic changes with the appearances seen with the clinical specular microscope. The extent of such damage appears to be related to the quantity of power delivered, its delivery mode, the number of laser bursts, and the target tissue/endothelium distance. The possible causes for such damage are discussed.

The posterior surface of the cornea in the irido-corneal endothelial syndrome: a specular microscopical study.

The corneal endothelia of 21 eyes afflicted with the irido-corneal endothelial (ICE) syndrome have been studied repeatedly with the clinical specular microscope. In all cases a characteristic cell type (the 'ICE-cell') is present but distributed in 4 different patterns. Accordingly, each case could be classified at any one time as one of 4 endothelial variants. One variant, always associated with elevated intraocular pressure (IOP), is characterised by a scattering of ICE-cells throughout the endothelial mosaic. This progresses rapidly to a second variant in which the entire endothelium appears 'replaced' by ICE-cells. In a third variant, associated with normal IOP, ICE-cells 'replace' only a portion of the endothelium which itself shows a great increase in cell numbers/unit area. This, apparently, slowly progresses to a fourth variant which shows a dramatic loss of endothelial cells.

Clinical features of the irido-corneal endothelial syndrome.

Progressive iris atrophy, Chandler's syndrome and the iris naevus syndrome are recognised as subgroups of the irido-corneal endothelial syndrome but in some cases a confusing overlap of the clinical signs is found. The clinical features of five cases selected from 19 patients with this syndrome are described. The findings suggest that the disease can be better subdivided into two groups based on the morphology of the posterior corneal surface as seen with the slit lamp.