Biomedical subjects

R L Radius

Publications and source records attributed to R L Radius.

At least 19 recordsLinked to original sources

PubMed1994

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.

Adolescent↗

PubMed1989

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.

Adult↗

PubMed1988

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.

Animals↗

PubMed1988

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.

Adrenergic beta-Antagonists↗

PubMed1988

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.

Aged↗

PubMed1986

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.

Adult↗

PubMed1986

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.

Animals↗

PubMed1984

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.

Animals↗

PubMed1984

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.

Cataract Extraction↗

PubMed1983

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.

Betaxolol↗

PubMed1983

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.

Animals↗

PubMed1982

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.

Animals↗

PubMed1982

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.

Animals↗

PubMed1981

Regional specificity in anatomy at the lamina cribrosa.

Specimens cut in cross section at the level of the lamina cribrosa in normal primate eyes are examined by light microscopy. The density of structural elements, consisting of crosswise-oriented connective-tissue trabeculae, is examined in different regions of the nerve head. It is noted that nasal more than temporal more than superior or inferior regions of the lamina cross section contain increased connective-tissue elements. This regional variation in nerve head anatomy is contrasted with susceptibility patterns of nerve head tissue to pressure elevation in both experimental and clinical glaucoma.

Animals↗

PubMed1981

Rapid axonal transport in primate optic nerve. Distribution of pressure-induced interruption.

Six primate eyes were studied after four hours of elevated intraocular pressure. Tissue specimens from the region of the lamina cribrosa were examined in cross section by transmission electron microscopy. Interruption in fast orthograde and retrograde axonal transport was identified in individual axons by noting accumulation of membraneous microorganelles, such as mitochondria and microvesicles within axon cylinders. Although organelle accumulation varied from bundle to bundle, involvement of individual axons was diffuse across the extent of a specific axon bundle. This observation contradicts the apparent association of axonal transport block with crosswise-oriented trabecular beams at the level of the lamina cribrosa as seen in tissue specimens examined in longitudinal section. It also fails to support the notion that blocked axonal transport with elevated pressure is produced by kinking of axons at the lamina.

Animals↗

PubMed1981

Effects of timolol on bovine corneal endothelial cultures.

The chronic use of timolol (Timoptic) maleate to control glaucoma may produce cytotoxic complications in the cornea. We have therefore compared the relative toxic effects of the commercial ophthalmic preparation with that of the pure compound. Commercial vehicle, either with or without 16 mM timolol maleate, killed cultures within the first five minutes of exposure. Pure timolol maleate, however, caused rapid but reversible cellular contractions, and cells remained viable in it for over 24 hours. Dilution with culture medium reduced both the cytotoxicity and the speed of the contractions. Incubation in 1:100 dilutions of vehicle or commercial drug preparations or in 0.16 mM pure timolol maleate did not alter cellular morphology. The results indicate that while undiluted vehicle is toxic, timolol maleate is not.

Animals↗

PubMed1981

Distribution of pressure-induced fast axonal transport abnormalities in primate optic nerve. An autoradiographic study.

The distribution of transport abnormalities in primate optic nerve from eyes subjected to five hours of pressure elevation (perfusion pressure of 35 mm Hg) was studied. Tissue autoradiography and electron microscopy were used to localize regions of the lamina cribrosa with increased transport interruption. A preferential involvement by this transport abnormality involved the superior, temporal, and inferior portions, to the exclusion of the nasal portion, of the optic nerve head. This observation supports the hypothesis that transport interruption seen in this model may be pertinent to the study of clinical glaucomatous neuropathy.

Animals↗

PubMed1981

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.

Connective Tissue Cells↗