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Purpose: In order to remove precisely scleral tissue overlying Schlemm's canal with minimal trauma as an outpatient procedure under local anesthetic, we used a VisX Twenty/Twenty excimer laser., Methods: We performed excimer laser filtration in three enucleated pig eyes, seven enucleated human eyes, and seven eyes of seven patients with severe glaucoma. Precise ablation to Schlemm's canal was confirmed by scanning electron microscopy in the enucleated eyes. For the patients, a local anesthetic was used, and a custom-made holder was used to mobilize the conjunctiva and fix the eye., Results: A functional sclerostomy was obtained with 1,780 to 5,965 pulses, using a 2 x 1-mm slit. In our mean follow-up of nine months (range, six to 12 months) the excimer laser filtration technique achieved controlled filtration in five of seven patients and minimized conjunctival trauma. One patient subsequently underwent cataract extraction., Conclusions: This study indicates that excimer laser filtration is an effective technique for achieving filtration in glaucoma. It may reduce the complications of glaucoma filtration surgery, particularly the incidence of shallow anterior chamber postoperatively, as it leaves the trabecular meshwork intact.

Fluorescein angiography of the iris vasculature and specular microscopy of the corneal endothelium were used to examine two important anterior chamber tissues in cases of heterochromic cyclitis, classical chronic cyclitis and some cases of iridocyclitis. The 13 cases of heterochromic cyclitis and eight cases of classical chronic cyclitis all showed vascular hypoperfusion of the iris, except for two young females with heterochromia. In these cyclitic eyes there was pupillary leakage of dye and all but one young female with heterochromia showed evidence of microneovascularization of the iris. Most patients showed evidence of abnormalities of the corneal endothelium, but this was most marked in elderly patients with heterochromic cyclitis, probably due to the long duration of the condition. Six of the patients with chronic cyclitis had bilateral disease and five of these were elderly women with glaucoma and grey irides, the group being distinct enough to form a discrete clinical entity. Seventeen of the patients with chronic cyclitis were females with grey irides suggesting that this type of patient is more susceptible to cyclitis. Patients with acute iridocyclitis showed little abnormality on fluorescein angiography, while those with recurrent or chronic disease showed vascular hypoperfusion and microneovascularization suggesting that these changes in the iris contribute to the chronicity of the condition. It is suggested that hypoperfusion and microneovascularization of the iris and abnormal permeability are important factors in the production of chronic cyclitis, and that the integrity of the corneal endothelium is affected by these changes if they operate over a long period of time.

The use of the specular microscope as a noninvasive in vivo method of identifying cholesterol crystals in two cases of crystalline corneal deposits is described. This illustrates the advantage of using the specular microscope under living conditions with a much higher magnification than is obtained with the slit lamp. Attention is drawn to the wider applications of this method.

Recent work has shown changes in the corneal endothelium accompanying corneal epithelial disease and anterior uveitis. It is important to differentiate these acute changes from other changes such as guttatae or corneal pigment deposition and to assess the magnitude of their effect upon the corneal endothelium. We have used specular microscopy to study changes in the corneal endothelium and Descemet's membrane and to study deposits on the back of the corneal endothelium and correlate them with changes in the endothelium by the use of conventional specular microscopy and by relief images which give a three dimensional view of the area concerned. This has particularly been applied to the conditions of superficial punctate keratopathy, keratoconjunctivitis sicca, corneal abrasions and exposure keratopathy, iritis and cyclitis, pseudoexfoliation of the lens capsule, anterior segment pigment dispersal syndrome, bullous keratopathy as well as corneal guttatae and pigment granules on the posterior cornea. Preendothelial lesions have been distinguished from endothelial and retrocorneal lesions by this technique aiding elucidation of the state of the endothelium. The changes which we noted occurred either at the level of Descemet's membrane (including formation of small rounded dark blebs less than one cell in diameter, larger blebs one to three cells in diameter, and guttatae, usually larger than the foregoing and sometimes very numerous), or at the level of the posterior endothelial surface (including small shiny nodular deposits, often numerous, due to pigment granules, and keratitic precipitates and inflammatory debris, the former usually large and the latter smaller, more irregular and sometimes very numerous). The differentiation and assessment of these various changes are discussed.

We have demonstrated marked changes in the corneal endothelium in some groups of patients with ocular anterior segment disease including chronic cyclitis, both heterochromic and classical, pseudoexfoliation of the lens capsule, and anterior segment pigment dispersal syndrome. The most striking changes occurred in heterochromic cyclitis with reduced endothelial cell counts (p less than 0.01) and altered cellular morphology. In almost all eyes with cyclitis endothelial belbs were seen. In eyes with unilateral pseudoexfoliation of the lens capsule there was a lower endothelial cell count with pleomorphism and polymegathism, the changes being somewhat more marked with raised intraocular pressure (p less than 0.01). In anterior segment pigment dispersal syndrome there was an even smaller reduction in count (p less than 0.05) with mild changes in morphology. Factors producing endothelial cell changes included hypoperfusion of the iris with microneovascularization of the iris stroma, intercellular bleb formation with oedema of the corneal endothelium, and raised intraocular pressure. A normal iris circulation is important to the integrity of the corneal endothelium.

A series of five cases is described in which superficial punctate keratopathy was associated with endothelial cell changes. The most striking change was the presence of dark areas or blebs, usually two to four cell diameters in extent. There was also distortion and crumpling of the corneal endothelium, mild pleomorphism and polymegathism of the endothelial cells, with a reduced cell count in some cases. These blebs have previously been reported in hard and soft contact lens wearers and are due to intercellular oedema with separation of endothelial cells from Descemet's membrane. Anoxia and interference with osmosis have been proposed as possible mechanisms for the production of these blebs, but our cases demonstrate that fine disruption of the corneal epithelium can affect the integrity of the corneal endothelium and may lead to significant damage over a long period of time.