Open angle glaucoma in melanosis oculi: response to laser trabeculoplasty

The case for an association between secondary open angle glaucoma and melanosis oculi is strengthened by our recent observation of a teenaged male with advanced glaucomatous damage in the eye with melanosis oculi. This report summarizes his clinical findings, his response to medical therapy and laser trabeculoplasty, and suggests the possibility that melanosis oculi causes secondary open angle glaucoma in patients who are predisposed to primary open angle glaucoma.

Laser-induced primate glaucoma. I. Progression of cupping

Sustained intraocular pressure elevations were induced in 15 monkey eyes by argon laser photocoagulation of the trabecular meshwork. Large fluctuations of IOP resulted. Posttreatment gonioscopy revealed an open angle with scattered low peripheral anterior synechiae. Optic disc cupping progressed during pressure elevations, manifested first as posterior bowing of the optic nerve head and peripapillary tissues. Reversal of this early phase of cupping occurred in eight eyes during spontaneous normalization of IOP. In most eyes, as cupping evolved from saucerization to a deeper cup, the cup remained round. In four eyes, focal sloping of the cup to the inferotemporal rim occurred with nerve fiber layer defects. Total cupping with undermining of the rim occurred in five eyes with prolonged IOP elevation. Laser-induced primate glaucoma has features in common with juvenile human glaucoma and is a useful model for the study of cupping of the optic nerve head.

Laser-induced primate glaucoma. II. Histopathology

A sustained, moderate pressure elevation was produced in 15 nonhuman primate eyes by application of laser energy to the trabecular meshwork. By light and electron microscopy, the trabecular beams were blunted, and scattered synechiae were present. Backward bowing of the lamina cribrosa, partial loss of the myelin sheath surrounding axonal segments just posterior to the lamina, and diffuse axonal loss involving the entire nerve cross section were noted. A quantitative analysis of this axonal loss revealed that eyes with moderate nerve head damage (cup-disc ratio, 0.6 to 0.8) had only 38% to 69% of the expected normal axonal count. The eyes with nearly total cupping (cup-disc ratio, 0.9 to 1.0) maintained between 10% and 36% of the normal axonal count. The disc changes in these experimental eyes are similar to those previously described in human eyes with glaucoma.

[Therapy-refractory secondary open-angle glaucoma caused by epithelialization of the anterior chamber following cataract extraction]

Histologic findings are presented which relate to a case of primary diffuse epithelial downgrowth into the anterior segment after surgery, with subsequent secondary open-angle glaucoma which resisted all attempts at therapy. Possible types of early therapy are discussed.

Trabecular meshwork cell culture in glaucoma research: evaluation of biological activity and structural properties of human trabecular cells in vitro

The propagation of human trabecular cells in culture allows the study of the structural and functional properties of this distinct cell type under reproducible experimental conditions. Human trabecular cells can be effectively grown from dissected explants of trabecullar tissue, and the cultured cells can maintain the distinctive ultrastructural features of uncultured trabecular cells through at least five passages in vitro. The trabecular cell possesses a wide range of biochemical and structural properties that may be important for the maintenance of the aqueous outflow pathway. These properties include the growth of trabecular cells as an endothelial monolayer with a nonthrombogenic cell surface, the production of plasminogen activator, avid phagocytosis, and the ability to synthesize glycosaminoglycans, collagen, fibronectin, and other connective tissue elements. The presence of hyaluronidase and other lysosomal enzymes emphasizes that human trabecular cells are capable of metabolizing hyaluronic acid and other extracellular materials. Potential mechanisms of trabecular cell damage in vitro are examined by evaluating the effects of extended passage, peroxide exposure, and laser treatment on cellular morphology.

Developmental immaturity of the trabecular meshwork in juvenile glaucoma

We used light and electron microscopy to compare ten specimens of anterior chamber angle tissue obtained by trabeculectomy from seven patients with juvenile glaucoma (primary glaucoma with open iridocorneal angle in young humans with specimens of normal trabecular meshwork from humans of the same ages. In all cases of juvenile glaucoma, we observed a thick compact tissue consisting of cells with fine processes and extracellular substances at the anterior chamber side of Schlemm's canal and abnormal deposits of ground substances in the thick tissue. These observations strongly suggest that the thick compact tissue represents an immature development of the trabecular meshwork and may be one of the primary causes of increased intraocular pressure in juvenile glaucoma. Our studies indicate that both congenital and juvenile glaucoma occur because of developmental immaturity of the trabecular meshwork in anterior chamber angle tissue and that the more extensive the immaturity, the earlier the glaucoma will become manifest.

The effect of age on the nerve fiber population of the human optic nerve

Nerve fiber counts of 16 normal human optic nerves from subjects aged 3.5 to 82 years showed a significant effect of age (P = .0207). The delay between death or enucleation and fixation also significantly affected the result (P = .0078). The mean (+/- S.E.M.) count for the 16 nerves was 1,244,005 +/- 20,033 fibers, giving a 99% confidence level between 1,192,400 and 1,295,610 fibers.

Trabecular meshwork cellularity in primary open-angle glaucoma and nonglaucomatous normals

The trabecular meshwork cellularity (cells/unit tissue area) was compared in patients with primary open-angle glaucoma (POAG) with that of nonglaucomatous (NG) individuals. The NG specimens (n = 69) include specimens from the prenatal period (n = 14) as well as the postnatal period to age 98 years (n = 55). The glaucoma specimens (n = 49) covered a wide-range of ages (23-80 years) and were obtained at trabeculectomy (n = 31) or at autopsy (n = 18). Our results show that the trabecular cellularity in NG specimens decreases most rapidly and in a nonlinear manner in the late fetal period and for the first few years of postnatal life. This rapid decline in cellularity then slows down to proceed in a nearly linear manner for the remainder of the 98 years of life studied. The meshworks from patients with POAG have a lower cellularity than normals over the wide range of ages examined, but both types of specimens undergo similar declines in cellularity with age. Thus, the age-cellularity curves for both the NG and POAG specimens are parallel to each other. The loss of cells occurs in a gradient-like manner with the inner tissues being most affected and the outermost tissues least affected. A variety of statistical tests show that these changes in cellularity are highly significant and specific. These findings are compared to the loss of endothelial cells in the cornea and they are discussed in relation to the important clinical characteristics of POAG.

Open-angle glaucoma associated with posterior polymorphous dystrophy. A clinicopathologic study

Clinical and histopathologic features of a 62-year-old black man with posterior polymorphous dystrophy and open-angle glaucoma requiring trabeculectomy are reported. The surgical procedure was modified to allow en bloc resection of the deep limbal tissue and peripheral iris. Light and electron microscopy of the specimen revealed a high insertion of the iris into the posterior portion of the trabecular meshwork with compression of the intertrabecular spaces. These findings are similar to changes that have been reported in primary congenital glaucoma and suggest a developmental anomaly of the anterior chamber angle in this form of glaucoma associated with posterior polymorphous dystrophy.

[The neuro-retinal rim region in early glaucoma]

The true neuro-retinal rim area of the optic disc was obtained by calculating the magnification using axial length, refraction and corneal curvature. Patients with very early chronic open angle glaucoma and normals were compared. The neuro-retinal rim area separated these two populations better than the standard cup/disc ratios. The size of the optic nerve did not appear to change with age. The implications for clinical practice are outlined.

[Fluoroangiography of glaucomatous optic papilla]

Authors describe the fluoroangiography of the optic pupil in 15 patients who were suffering from chronic open-angle glaucoma and found a lessening of the fluorescence of the optic disk. It can be attributed to a hypoperfusion of the optic nerve. The results obtained and that is an constant ipofluorescein, even with different levels in relation to the type of glaucoma damage noticed, they look to support this etiopathogenetic hypothesis.

Glucocorticoid target cells in human outflow pathway: autopsy and surgical specimens

Target cells for glucocorticoids were found in trabeculectomy specimens obtained surgically from humans with glaucoma (primary and secondary) and from nonglaucomatous autopsy eyes using an autoradiographic technique. Specific nuclear localization of 3H-dexamethasone was found in cells of the trabecular meshwork, scleral fibroblasts, and in the endothelial lining of both Schlemm's canal and the outflow vessels. Glucocorticoids may alter the outflow facility by a direct effect on the metabolism of these cells. The autoradiographic method is suitable for studying competitors of glucocorticoid binding in small surgical specimens of human tissue involved in the outflow of aqueous humor.

Open-angle glaucoma: diagnosis and management

Open-angle glaucoma is not a benign disease; untreated, it can lead to total blindness. If intraocular tension is controlled early, before onset of visual field loss or optic nerve degeneration, the prognosis is good.

Why is intraocular pressure elevated in chronic simple glaucoma? Anatomical considerations

Ultrastructural analysis of 400 trabeculectomy specimens of glaucomatous eye revealed three types of extracellular deposits within the cribriform layer of the trabecular meshwork. One of these derives from the sheath of the subendothelial elastic-like fibres. Tissue culture and ultrahistochemical studies led to the assumption that these deposits contain glycoproteins, probably secreted by the cribriform layer cells.

Morphologic changes in the lamina cribrosa correlated with neural loss in open-angle glaucoma

We divided 25 glaucomatous human eyes into three groups representing mild (Group 1, seven eyes), moderate (Group 2, 11 eyes), and severe (Group 3, six eyes) optic nerve damage, based on visual field testing or remaining number of optic nerve fibers. The optic nerve head of each eye was examined by scanning electron microscopy. Compression of the successive lamina cribrosa sheets was the earliest detected abnormality, occurring in some eyes before the detection of visual field loss. Backward bowing of the entire lamina cribrosa was a later change and involved its upper and lower poles more than the mid-nerve head. The diameter of the scleral opening at the level of Bruch's membrane did not enlarge in these adult glaucomatous eyes. Mechanical compression of the nerve head occurred early enough to be considered a primary pathogenetic event in glaucomatous damage.

The lamina cribrosa and visual field defects in open-angle glaucoma

Two types of lamina cribrosa, one with the classic dot-like openings and the other with striate openings, were seen in 71 pairs of optic disc photographs from patients who had chronic open-angle glaucoma, were suspected to have glaucoma or had normal eyes. Of the 11 eyes with a striate pattern 64% showed glaucomatous visual field defects, whereas of the 60 eyes with a dot pattern only 12% showed such defects, a highly significant difference (p less than 0.001); when patient age and ratio of the vertical diameters of the optic cup and disc were controlled the difference remained significant (p = 0.0402). The striate pattern was also significantly associated (p less than 0.05) with a large optic cup (vertical cup/disc ratio 0.7 or greater).

Increased pressure of dilated episcleral veins with open-angle glaucoma without exophthalmos

Six unilateral cases and one bilateral case of dilated episcleral veins with elevated intraocular pressure without exophthalmos are described. Episcleral venous pressure measured on six unilateral cases showed increased pressure in the affected eye compared to the other eye and to normal controls. Two eyes had typical glaucomatous disc and visual field changes. Five had more optic disc cupping and pallor in the eye with the elevated episcleral venous pressure and intraocular pressure. A thorough work-up, including orbital venography in two unilateral cases, carotid arteriography in one and episcleral fluorescein angiography in five cases, failed to show venous obstruction or direct arterio-venous communications. The different diagnoses are discussed. This condition should be considered in unilateral or asymmetrical intraocular pressure elevation and in those patients with chronically red eyes without discharge.

[Immunofluorescence studies of the human trabecular meshwork]

Accumulation of extracellular material in the trabecular meshwork is responsible for increased resistance to outflow in the human eye. By means of the indirect immunofluorescence technique the authors detected extracellular collagen type IV, fibronectin and laminin in the trabecular meshwork and the wall of Schlemm's canal of glaucoma patients and controls. Collagen type IV is the so-called "basement membrane collagen" present in the lens capsule, Bowman's and Descemet's membranes. Fibronectin is a glycoprotein with many biologic activities; it can promote cell attachment and forms complexes with collagen. Laminin was isolated in 1979 and is present in the lamina lucida of basement membranes. The increased production and pathological metabolism of these three substances might be of some importance in the pathogenesis of primary open-angle glaucoma.