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Biomedical subjects

J J Weiter

Publications and source records attributed to J J Weiter.

At least 19 recordsLinked to original sources
PubMed1992

Classification of retinal pigment epithelial detachments associated with drusen.

To understand the natural history of retinal pigment epithelial (RPE) detachments (PEDs) associated with drusen, we retrospectively reviewed 125 PEDs that had not undergone laser treatment over an average follow-up period of 28 months. We identified six types of RPE detachments: pseudo-vitelliform, confluent drusen, serous, vascular, and hemorrhagic lesions as well as PEDs associated with a retinal vascular abnormality. We correlated the type of detachment with visual acuity and anatomic outcome. The poorest results were obtained for PEDs associated with neovascularization (vascular, hemorrhagic, and retinal vascular abnormality types). Eyes presenting with pseudo-vitelliform lesions or confluent drusen had the best visual prognosis and anatomic results. Obvious subretinal new vessels developed in 16 (34%) of the serous PEDs over an average follow-up period of 25 months. Subretinal neovascularization was rare in the pseudo-vitelliform and confluent drusen groups. The proposed classification system may be useful in predicting the natural course of PEDs.

Adult↗
PubMed1992

Retinal blood flow alterations associated with scleral buckling and encircling procedures.

The bidirectional laser Doppler technique and monochromatic photography were used to measure the absolute blood flow rate in the major temporal retinal arteries in seven patients following unilateral scleral buckling and encircling procedures, and in two patients before and after removal of scleral buckling elements. In the seven patients who had undergone uncomplicated scleral buckling procedures the arterial flow rates were on average 50% lower (p = 0.01) in the surgically treated eyes than in the contralateral eyes. Removal of scleral buckling elements in two patients produced increases of 73% and 44% in arterial blood flow rates.

Adult↗
PubMed1992

Comparison of external and internal approaches for transplantation of autologous retinal pigment epithelium.

The feasibility of autologous transplantation of retinal pigment epithelial (RPE) cells from just posterior to the ora serrata to the posterior pole was demonstrated in the rabbit model. Two techniques for introducing the transplanted cells were compared: an internal (anterior transvitreal) and an external (posterior transscleral) penetration to the subretinal space. In both approaches, RPE cells were obtained by biopsy from the peripheral retina of a rabbit eye, cultured, labeled with a fluorescent dye and 3H-thymidine, and transplanted to the posterior pole of the same or contralateral eye. The external approach consistently resulted in a greater number of transplanted cells on Bruch's membrane. The internal technique was more precise because it permitted direct visualization of the placement of the transplanted RPE. Transplantation of autologous RPE is a possibility that should be further pursued.

Animals↗
PubMed1992

Viral infections of the choroid and retina.

DNA (herpes viruses) and RNA (rubella, rubeola) group viruses are recognized causes of viral retinitis. Severe damage is often the result, not only because the viruses have a cytologic effect but also because the antigens may cause immune complex deposition that results in vasculitis. Most of the viral retinitides are associated with systemic disease; immune-compromised individuals are more susceptible than healthy individuals. A distinct clinical entity, acute retinal necrosis, affects the eye only in healthy individuals and is associated with the herpes family of viruses.

Chorioretinitis↗
PubMed1991

Preretinal pH changes in the rabbit under conditions of light and dark.

Preretinal pH was measured in the avascular region of 19 rabbit retinas during alternating cycles of light and dark, using a miniature, needle-type pH electrode. In 14 experiments with the rabbits breathing room air, cyclic changes in pH, decreasing in the dark and increasing in the light, were observed. The transition from light to dark caused a mean pH decrease of 0.047 +/- 0.029 U (n = 14). An inversion of the light/dark pH response was observed in five experiments. In three of these, the effect was induced by having the rabbits breathe 100% O2. In the five rabbits showing a reversed response, a mean pH increase of 0.034 +/- 0.025 pH U was observed in the dark; light-ON caused a decrease of 0.035 +/- 0.025 pH U. The direction of the preretinal pH change is thought to be the net effect of light/dark-induced changes in the metabolism of the photoreceptors and inner retinal layers (defined for the purpose of this paper as the region between the outer synaptic layer and the inner limiting membrane). In six separate experiments, retinal metabolism was assessed by measuring preretinal PO2 during alternating cycles of light and dark while the rabbits breathed room air. Oxygen tension declined from a mean of 14.5 +/- 6.2 (S.D.) mmHg in the light to 10.1 +/- 5.4 (S.D.) mmHg in darkness, and increased from a mean of 10.9 +/- 5.1 (S.D.) mmHg in darkness to 15.4 +/- 5.8 (S.D.) mmHg in the light. The time courses of the pH and the PO2 changes were similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Optic nerve head blood speed as a function of age in normal human subjects.

We used the laser Doppler technique to determine the relation between age and the speed of blood cells moving through the capillaries of the optic nerve head. We studied 22 normal human volunteers ranging in age from 16-76 years. The results were best described by a statistically significant quadratic relationship between capillary blood speed and age. Blood speeds were lowest in the youngest and oldest subjects and highest in subjects between 27 and 35 years old. A two-phase linear model showed a statistically significant 20% decrease in blood speed in volunteers between the ages of 31 and 76. The results were not affected by gender, degree of refractive error, systemic blood pressure, intraocular pressure, cup/disc ratio of the optic nerve head, or by site-to-site differences in the light scattering properties of the optic nerve head tissue. Capillary blood speed was, on average, 15% greater from temporal sites than from nasal sites, corresponding to the equally greater distribution of ganglion cell axons within the same area. The results provide a baseline of normal age-controlled data that can be compared to measurements obtained from patients with disorders of the optic nerve head thought to have a vascular etiology.

Adolescent↗
PubMed1990

The macular photostress test in diabetic retinopathy and age-related macular degeneration.

We propose the macular photostress test for the evaluation of macular function in the office setting. Eighty eyes were tested and divided into four diagnostic categories: background diabetic retinopathy, diabetic macular edema, age-related macular degeneration, and normal. The recovery times for the eyes with age-related macular degeneration were longer than for eyes with macular edema (P = .03). Age-matched patients with age-related macular degeneration had longer recovery times than did those without age-related macular degeneration (P = .0001). A possible explanation is that the prolonged recovery time in the eyes with age-related macular degeneration reflects that the anatomic lesion is located in the retinal pigment epithelium-photoreceptor complex. In comparison, the eyes with macular edema, whose lesion is in the inner retina and not the retinal pigment epithelium, show a less-prolonged recovery time than the eyes with age-related macular degeneration.

Adolescent↗
PubMed1989

Effects of optic atrophy on retinal blood flow and oxygen saturation in humans.

Retinal blood flow and oxygen saturation were evaluated in patients with unilateral inner retinal degeneration secondary to neurogenic optic atrophy. Arteriovenous O2 saturation for temporal and nasal vascular segments of the affected eyes, evaluated by retinal vessel oximetry, was 12% +/- 9% higher than in the fellow eyes (seven patients). Blood flow in the temporal retinal arteries of the affected eyes, measured by the laser Doppler technique, was 48% +/- 20% lower than in the fellow eyes (four patients). The combination of these results indicated a 40% +/- 29% reduction in O2 delivery in the affected eyes (four patients), thereby quantifying the decrease in retinal metabolism that resulted from inner retinal degeneration.

Adolescent↗
PubMed1989

Malignant transformation of an iris melanocytoma. A case report.

A 34-year-old Caucasian woman was diagnosed as having a pigmented iris tumor showing recent growth and satellite lesions. The tumor was associated with pigmentation of the anterior chamber angle and secondary unilateral glaucoma. After local excision, histopathologic studies revealed the plump polyhedral cells typical of melanocytoma. However, the examination of additional sections showed evidence of malignancy. The diagnosis of a melanocytoma that transformed into malignant melanoma was made and later confirmed by electron microscopic studies. Following surgical excision of the tumor, the eye maintained normal intraocular pressure. There was no evidence of recurrence 4 years after surgery.

Adult↗
PubMed1989

Precocious retinal adhesion is affected by furosemide and ouabain.

A "precocious" adhesive force develops between the neurosensory retina (NSR) and the retinal pigment epithelium (RPE) 15-30 minutes after eyes are removed from day 15 embryonic chickens and incubated at 37 degrees C. Precocious adhesion has been reported to be blocked by exposure to cold but to be unaffected by exposure to furosemide and ouabain. Since RPE transport is thought to play a major role in the adhesion between the RPE and NSR of adult mammals, and since ouabain and furosemide block RPE transport in embryonic chickens, it has been thought that precocious adhesion in embryonic chickens is not a good model for studying adhesion between the RPE and the NSR of adult mammals. We have found, however, that when steps are taken to ensure that ouabain and furosemide reach the transport sites on RPE apical membrane before precocious adhesion develops, that ouabain and furosemide do affect precocious adhesion.

Animals↗
PubMed1989

Photocoagulation of chorioretinal anastomoses in far-advanced age-related macular degeneration.

In age-related macular degeneration, communication between the retinal and choroidal circulations occurs spontaneously or following unsuccessful laser photocoagulation of subretinal new vessels. The resulting chorioretinal anastomotic complex, which includes the subretinal new vessels and their feeder retinal vessels, usually shows marked exudation and produces an extensive serous detachment of the neurosensory retina in the posterior pole, often associated with hard exudates. Eleven eyes with chorioretinal anastomotic complexes were treated using the monochromatic green argon laser. Adequate closure of the chorioretinal anastomotic complexes by photocoagulation resulted in retinal flattening in the posterior pole with resolution of the hard exudates and improvement of vision in eight of the 11 treated eyes.

Aged↗
PubMed1989

Superoxide production by porcine retinal pigment epithelium in vitro.

Cultured porcine retinal pigment epithelial cells release superoxide, measured as superoxide dismutase (SOD)-suppressible reduction of cytochrome C, and SOD-suppressible luminol-dependent chemiluminescence. Latex beads stimulated a significant release of superoxide that reached 82 nmol/mg protein in the first 15 min and declined thereafter. Formation of an insoluble blue formazan following reduction of nitroblue tetrazolium histochemically demonstrated that superoxide was released over the region of the cell vicinal to the bead. Dioctanoylglycerol, a synthetic, cell-permeating activator of protein kinase C, also elicited a rapid release of superoxide from RPE cells. This study emphasizes the need to characterize the mechanisms by which superoxide is generated, whether its release is regulated, and how toxicity is prevented in vivo.

Animals↗
PubMed1989

Blood flow in the normal human retina.

The laser Doppler technique was used to measure the blood flow rate in 41 major vessels in ten eyes of healthy volunteer subjects. The specific relationship between blood flow rate, F, and vessel diameter, D, was determined for both retinal arteries and retinal veins. On average, F increased with increasing D at a power of 4.1, consistent with the presence of Poiseuille flow. In six eyes of six subjects, measurements on individual vessels were combined to yield the total retinal blood flow rate. The mean and standard deviation of the total retinal blood flow was 80 +/- 12 microliter/min. The blood flow rate per unit mass of retinal tissue was calculated and found to be in good agreement with that reported for macaque monkeys. Blood flow to the temporal side of the retina was approximately three times larger than to the nasal side. There was no significant difference between blood flow to the superior and the inferior retina.

Adult↗
PubMed1989

Cell loss in the aging retina. Relationship to lipofuscin accumulation and macular degeneration.

We examined the impact of aging on the numbers of photoreceptors and retinal pigment epithelium (RPE) cells, and the number of photoreceptors per RPE cell profile, in selected regions of 30 human eyes. The mean ratio of photoreceptors to RPE cell was higher in the macula than in the paramacula (P less than 0.01) or the equatorial area (P less than 0.001). We found evidence for an age-related loss of RPE in both whites (P less than 0.02) and blacks (P less than 0.0006), although the rate of loss in whites was significantly slower than in blacks. Photoreceptor loss in blacks was inversely correlated with age (P less than 0.04). In whites, however, photoreceptor loss was very significantly and directly correlated with lipofuscin concentration in the opposing RPE (P less than 0.0001) and unrelated to age. The disparity in the rates of photoreceptor and RPE cell loss produced, in older eyes, a higher ratio of photoreceptors per RPE cell profile. In the macula, the ratio for whites over 50 years of age was significantly higher (P less than 0.05) than that in blacks over 50. Our data suggest that the increased phagocytic and metabolic load on the RPE, which ultimately the macula causes a preferential age-related accumulation of lipofuscin in the RPE, which ultimately leads to photoreceptor death. This may prove a useful model of age-related macular degeneration and Stargardt's disease.

Adolescent↗
PubMed1989

Association between cilioretinal arteries and juxtapapillary scars.

We examined the relationship of cilioretinal arteries (CRAs) to juxtapapillary chorioretinal scars, along with the developmental significance of the latter in relation to CRA formation. Both eyes of 360 patients were studied. Sixty-eight (18.9%) of these patients had a CRA in at least one eye, 13 of these 68 (19.1%) had one in both. The CRAs were distributed equally between right and left eyes. Two hundred eight patients (57.8%) had a scar in at least one eye; 157 of these (75.5%) had one in both. The presence of a CRA was significantly associated with the presence of a scar. Since both are common developmental variations, this correlation points to a common embryologic formation mechanism.

Ciliary Body↗
PubMed1989

Furosemide-sensitive Cl transport in bovine retinal pigment epithelium.

Bovine retinal pigment epithelium (RPE)-choroid explants were sealed in an Ussing chamber. Typical preparations produced a transepithelial voltage (Ve) of 12 mV (retina side positive) and had an electrical resistance (R) of 300 ohm-cm2. These values can be attributed to the RPE. Furosemide and ouabain reduced the Ve without affecting R when applied to the apical side of the RPE, but had no effect upon Ve and R when applied to the choroidal side. Acetazolamide had no effect upon Ve and R when applied to either side of the tissue. In Cl-free medium, ouabain reduced Ve without affecting R, while furosemide had no effect upon Ve and R. In Na-free medium, ouabain and furosemide had no effect upon Ve and R. Unidirectional isotope flux studies performed under open circuit conditions showed a net retina-to-choroid Cl flux that was abolished by furosemide. These results indicate that bovine RPE possesses a furosemide-sensitive Cl transport system.

Animals↗
PubMed1989

Topical phenylephrine for mydriasis affects rabbit retinal pigment epithelial transport.

Rabbit retinal pigment epithelium (RPE) has an alpha-1 adrenoreceptor that substantially reduces RPE short circuit current (Isc) when stimulated. Since phenylephrine is a potent alpha adrenergic agonist frequently used to obtain pupil dilation, we examined the effect of topically applied phenylephrine for pupil dilation on RPE transport. Naive black dutch-belted rabbits received either one drop of 10% phenylephrine applied at t = 0 and t = 30 min or one drop of 1% cyclopentolate applied at t = 30 min. At t = 50 min, RPE-choroid-sclera explants from these animals were sealed in an Ussing chamber. At t = 60-70 min, 1.4 X 10(-4) M epinephrine was introduced into both sides of the Ussing chamber. The change in Isc produced by epinephrine was measured. The Isc reduction in rabbits receiving phenylephrine was 26% (+/- 5% SD, n = 6). The Isc reduction in rabbits receiving cyclopentolate was 39% (+/- 6% SD, n = 5). These values are significantly different (P less than 0.02, student two-tail t-test). These results indicate that topical phenylephrine reached the RPE in vivo and prestimulated the alpha-1 adrenoreceptors.

Administration, Topical↗