Screening for glaucoma with stereo disc photography.

PURPOSE: To determine the value of taking simultaneous stereo photographs of the optic nerve head as a basis for identification of patients with glaucoma. METHODS: Two hundred fifty-eight patients received complete ophthalmological examinations and were ranked on a scale of 1-5 regarding the likelihood of their having glaucoma. Each eye was also photographed using the NIDEK camera, providing stereo pairs of the optic nerve head. The same patients were reclassified by two independent masked observers on the same scale of 1-5, based solely on examination of the photographs. RESULTS: Examination of stereo photographs alone provided maximum sensitivity of 75% and specificity of 95% in identification of glaucoma patients when photographic readings were compared with all available clinical information. CONCLUSIONS: Stereo photographs of the optic nerve head can be used for glaucoma detection with an accuracy that is significantly greater than simple tonometry and with a sensitivity that is equivalent to screening with computerized perimetry.

Trabeculectomy for traumatic hyphema with increased intraocular pressure.

We reviewed the medical records of 11 consecutive patients who underwent trabeculectomy with anterior chamber washout and peripheral iridectomy as the primary surgical treatment for traumatic hyphema that was unresponsive to medical management. The mean intraocular pressure before surgery was 48 mm Hg. In ten of the patients the intraocular pressure was lowered to 21 mm Hg or lower after surgery and remained below that level up to the most recent follow-up visit, which ranged from eight to 97 months. One patient required a topical beta-blocker and oral acetazolamide to lower pressure to this level after surgery. Eight patients had visual acuity of 20/60 or better at last follow-up. Corneal blood staining occurred in eight patients. Compared with other techniques for surgical management of traumatic hyphema, trabeculectomy provides a means to keep intraocular pressure lowered while the remaining blood is clearing from the anterior chamber. Trabeculectomy with anterior chamber washout and peripheral iridectomy appears to be a safe and reliable procedure in the management of traumatic hyphemas in which medical management fails to control intraocular pressure.

Ab interno sclerostomy with a high-powered argon endolaser. Clinicopathologic correlation.

A high-powered argon blue-green laser coupled to a 300-microns quartz fiberoptic probe was used to create an ab interno sclerostomy in a patient undergoing enucleation for a blind painful eye. Despite the presence of diffuse rubeosis, 360 degrees peripheral anterior synechiae, and superior conjunctival scarring, it was possible to create a full-thickness defect from the anterior chamber angle to the subconjunctival space without operative complications. Six laser applications were required using 8 W of power per pulse and 0.1-second pulse duration. The eye was enucleated immediately after the laser procedure, prepared for light microscopy, and sectioned serially. Histologic analysis demonstrated a patent fistula approximately 300 microns in diameter with sharp wound margins. Tissue damage was localized to within 150 microns of the sclerostomy. The overlying conjunctiva was intact.

Ab interno sclerostomy with a high-powered argon endolaser.

We used a high-energy argon blue-green laser (15-W maximum power output) to create full-thickness sclerostomies from the region of the anterior chamber angle to the subconjunctival space in pigmented rabbits using an ab interno approach. One to four laser pulses delivered through a 300-micron noncontact fiberoptic probe produced patent sclerostomies in all 20 eyes treated using 0.1-second pulse duration and 5 to 14 W of power. No intraoperative complications were encountered. Intraocular pressure, measured in 12 animals, decreased an average of 12 mm Hg in the treated eye relative to the fellow eye on the first postoperative day. The drop in intraocular pressure was associated with formation of a functioning filtration bleb. Intraocular pressure returned to preoperative levels in ten of 12 (83%) of the animals by the fourth postoperative day, and there was an associated flattening of the filtration bleb. Histologic and radioautographic analysis indicated that the effect of the laser was focal. Tissue damage and cellular proliferative response were limited to within approximately 200 micron of the wound margin.

Visual-field function in pseudophakia.

An automated perimeter (Octopus 2000) was used to examine visual-field function in 52 pseudophakic eyes. Threshold sensitivity was reduced throughout the visual field by from 0.4 to 20.0 decibels from that of threshold sensitivity in age-matched normal eyes. This reduction was comparable to that seen in contact-lens-corrected aphakic eyes.

A comparison of betaxolol and timolol in open angle glaucoma and ocular hypertension.

In a randomized, double-masked study, 41 patients with primary open-angle glaucoma or ocular hypertension were treated with betaxolol 0.5% or timolol 0.5% drops for 26 weeks. The average decrease in intraocular pressure (IOP) over the total study period was significant with both betaxolol (-6.3 mmHg) and timolol (-7.2 mmHg) in patients receiving no adjunctive therapy. There was no difference between betaxolol and timolol with respect to changes from baseline IOP. Significantly decreased mean brachial arterial pressure (MAP) was seen only with timolol, although the difference between the two groups was not significant. Pulse, pupil size, and basal tear secretion were unchanged in both groups. Burning upon instillation of the drops was more frequent with betaxolol.

Anatomy of the optic nerve head and glaucomatous optic neuropathy.

The mechanism of axon damage in eyes with glaucomatous optic neuropathy remains undefined. Interestingly, it has been observed that, although the entire nerve cross-section may be involved by the nerve damage, in many instances, the superior and inferior axon bundles are preferentially affected by the pressure insult. Thus, recent studies by many investigators have stressed a re-examination of the optic nerve head anatomy, including the nerve head microcirculation, the glial and connective tissue elements within the nerve head, and the morphology of the axons themselves. Any correlation between regional differences in this anatomy and the preferential involvement by specific axon bundles within the nerve head by the pressure insult may suggest some further insight into the mechanisms underlying the pressure-induced axon loss in glaucomatous eyes.

Background illumination and automated perimetry.

Visual field function in the right and left eyes of 31 normal volunteers was evaluated with an automated projection perimeter (OCTOPUS). Serial visual field evaluations were repeated in these same eyes with neutral filters of increasing optical density. We compared the results of threshold determinations with the different neutral filters in place before the examined eye. Significant reduction in threshold sensitivity at several test spots throughout the central 30 degrees visual field was seen with neutral density filters of 0.5 log units or greater. The low level of background illumination of the OCTOPUS perimeter (4.0 apostilbs) may allow relatively minor reduction in light transmission by the ocular media to produce significant changes in the recorded level of threshold sensitivity during visual field evaluation.

Axon morphology at the lamina cribrosa in monkey eyes.

The eyes of 8 monkeys (Aotus trivirgatus) were studied. The mean cross-section area and the least diameter of axon cylinders were calculated from measurements made by computer assisted planimetry of electron photomicrographs of sections through the optic nerve head at the level of the lamina cribrosa. The density of intrabundle connective tissue and glial cell elements in nerve fiber bundles was also calculated. The mean cross-section area and minimum diameter of axons in the temporal part were less than in the nasal part of the nerve. The values for axons in the superior and inferior parts of the nerve were intermediate. A similar pattern of increasing dimensions was seen in axons from the more axial nerve compared to neurons in the more circumferential nerve sectors. The density of the intrabundle, nonaxonal tissue elements did not differ significantly across the nerve. Although axon dimensions may play some role in defining the vulnerability of neuronal tissue to a pressure insult, the results of this anatomic investigation do not support the hypothesis that differences in axonal distribution by size across the nerve section define the regional vulnerability of the nerve head to elevated intraocular pressure.

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.

Pseudophakia and intraocular pressure.

We studied the change in intraocular pressure in 373 consecutive eyes undergoing cataract extraction with intraocular lens implantation between Jan. 1, 1981, and May 31, 1982. There was a mean increase in intraocular pressure of 0.1 mm Hg following this surgery. This increase, however, was not statistically significant (P greater than .5). There was a mean rise in pressure of 0.8 mm Hg in the eyes undergoing intracapsular surgery and a mean fall in pressure of 0.6 mm Hg in the eyes undergoing extracapsular surgery (P less than .05). The change in pressure was unrelated to age, surgeon, or lens type. The results of a separate analysis of 16 eyes with a preoperative diagnosis of glaucoma and eight eyes with ocular hypertension were similar.

Use of betaxolol in the reduction of elevated intraocular pressure.

Forty eyes in 20 patients with elevated intraocular pressure were treated with either a 0.125% betaxolol ophthalmic solution or a placebo. After 2, 4, and 6 weeks of twice-daily therapy, the eyes receiving the betaxolol had a mean percent reduction in IOP greater than that in the eyes treated only with the drug vehicle (placebo). Both solutions were well tolerated.

Pressure-induced fast axonal transport abnormalities and the anatomy at the lamina cribrosa in primate eyes.

In ten owl monkey eyes (Aotus trivirgatus) the location of pressure-induced (perfusion pressure 35 mmHg) axonal transport abnormalities was determined by the examination of serial step cross-section tissue radio autographs from the optic nerve head. The degree of the local transport interruption did not correlate with the fiber bundle cross-section area, the shape of the laminar pores or the density of the inter-bundle septa in that region.

The anatomy at the lamina cribrosa in the normal cat eye.

In normal cat eyes, the mean cross-sectional area of the nerve fiber bundles is greater in the temporal than in the nasal lamina cribrosa. The area occupied by the interbundle trabeculae is less in the temporal sectors than in the nasal sectors of the nerve. The number and the shape of the laminar pores are similar in all nerve sectors.

Axonal transport interruption and anatomy at the lamina cribrosa.

Pressure-induced, focal axonal transport abnormalities were studied in 14 cat eyes by the examination of serial step-section tissue radioautogram. Although the patterns of the transport interruption at the lamina cribrosa varied from eye to eye, the temporal sectors of the nerve head were most often involved by this abnormality. The anatomy at the lamina cribrosa was studied in adjacent (6 micrometers) cross-sectional specimens. The thickness of the extra-bundle trabeculae and the nerve fiber bundle dimensions including the cross-sectional area and the number and the shape (the ratio of the major and the minor axis diameters) of the laminar pores were measured by computer-assisted perimeter analysis. There was no correlation between the location of the transport interruption and any of these anatomic measurements.

Anatomy of the lamina cribrosa in human eyes.

Light microscopy of specimens of human eyes cut in cross section at the level of the lamina cribrosa showed variation in structural anatomy, as demonstrated previously in certain primate eyes. Connective tissue and glial cell structural elements were greater in nasal-temporal as compared with inferior and superior quadrants of the disc. This regional variation suggests a hypothesis for the specificity of early patterns of optic nerve dysfunction characteristic of glaucomatous optic neuropathy. In glaucomatous eyes, nerve head regions with relatively less structural tissue elements may yield early to detrimental effects of persistent pressure elevation.

Pressure-induced optic nerve axonal transport interruption in cat eyes.

After intravitreal injection of tritiated leucine, optic nerve axonal transport was studied in 30 cat eyes by tissue radioautography. Twenty-five experimental eyes were examined after four hours of acute pressure elevation with perfusion pressures maintained at 20 to 70 mm Hg. In five control specimens, intraocular pressures were maintained at 10 mm Hg for the four-hour interval. The extent of leucine accumulation, as seen by radioautographs, was inversely proportional to the perfusion pressure. Accumulation was limited to the region fo the lamina cribrosa. The anatomic distribution and pressure response of this transport interruption were similar to those seen in primate eyes studied under similar conditions.

Morphology of axonal transport abnormalities in primate eyes.

The ultrastructure of the retina and optic nerve head was studied in primate eyes after central retinal artery occlusion. Within 2 hours of the vascular occlusion the inner retinal layers undergo watery (isosmotic) swelling. This watery swelling of axons and astroglia extends into the nerve head as far back as the anterior boundary of the scleral lamina cribrosa. The swelling is increased 4 hours after the occlusion, and by 24 hours disintegration has occurred. At the optic nerve head mitochondria and vesicles of smooth endoplasmic reticulum begin to accumulate within 2 hours. The accumulation increases at 4 hours and persists to 24 hours. The watery swelling seems characteristic of ischaemic axons. Membranous organelles accumulate at the boundary of an ischaemic zone when material carried by axonal transport is brought via the healthy axon segment to the boundary, but they cannot proceed further into the ischaemic zone. Such accumulation is typical of locations where rapid orthograde axonal transport or retrograde axonal transport is blocked. In contrast, when slow axonal flow is impaired, the swelling is characterised by an excess of cytoplasmic gel without a marked accumulation of organelles. Rapid orthograde transport and retrograde transport seem to be closely related to one another, while slow axoplasmic flow seems fundamentally different. From morphological findings we suspect that, in experimental glaucoma, intraocular pressure first affects the intracellular physiological process of rapid orthograde and retrograde axonal transport. Watery swelling may not occur unless the ischaemic injury to cell metabolism is more advanced. In contrast, in experimental papilloedema, the swelling results predominantly from impaired slow axoplasmic flow.

Anatomy of the retinal nerve fiber layer.

Anatomy of the retinal nerve fiber layer in rabbit eyes is studied by light microscopy, transmission electron microscopy, and scanning electron microscopy. It is demonstrated that retinal striations noted ophthalmoscopically in these eyes represent individual fiber bundles, Axon bundles are compartmentalized within tissue tunnels comprised of elongated processes of glial cell origin.