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Biomedical subjects

M L Wolbarsht

Publications and source records attributed to M L Wolbarsht.

At least 55 records · Page 3Linked to original sources
PubMed1981

Increased retinal oxygen supply following pan-retinal photocoagulation and vitrectomy and lensectomy.

Panretinal photocoagulation as well as vitrectomy are the main treatment modalities for diabetic and other proliferative retinopathies. We show that both treatments introduce a new source of oxygen to the inner retina and propose that their efficacy in controlling the retinopathy results from their effect on the oxygenation of the inner retina. Panretinal photocoagulation reduces the oxygen consumption of the outer retina and allows more oxygen to diffuse to the inner retina from the choroid. Vitrectomy/lensectomy on the other hand allows aqueous humor to flow back to the retina and give oxygen to the inner retina which normally has a lower PO2 than aqueous humor. This causes the PO2 in aqueous humor to fall.

Animals↗
PubMed1980

A scleral buckle pressure gauge for continuous monitoring of intraocular pressure.

An implantable variable resistance pressure gauge has been constructed from a conductive elastomere in the form of a scleral buckle which is suitable for recording intraocular pressure in vivo continuously over an indefinite period of time. The similarity of the pressure transducer to the standard scleral buckles used to reduce retinal detachments suggests that it will be tolerated over a period of years without significant effect on intraocular pressure. The electrical output from these pressure gauges appears to be both well defined and of sufficient magnitude to operate a valve to control intraocular pressure.

Animals↗
PubMed1980

Cone contributions to cat retinal ganglion cell receptive fields.

Extracellular microelectrode recordings were made from ganglion cells of the intact, in situ eyes of adult common domestic cats. Three different photopic systems, with peak spectral sensitivities at 450, 500, and 556 nm, were observed. All ganglion cells received input from a cone system with a peak spectral sensitivity of 556 nm. The blue-sensitive cone system was observed in about one-half of the ganglion cells studied. In each case the 450-nm cone system contributed to only one functional type of response, either ON or OFF, in the same cell. The other two photopic systems most often contributed to both the ON and OFF responses of an individual ganglion cell. In four cases the 450-nm cone system mediated responses that were opponent to those of the other two photopic systems. The third photopic mechanism has a peak spectral sensitivity at 500 nm and contributed to most receptive field surrounds and many receptive field centers. It is distinguished from the rod system by the occurrence of a break in both dark-adaptation curves and increment-sensitivity curves. No apparent differences in receptive field cone contributions between brisk-sustained and brisk-transient cells were seen.

Animals↗
PubMed1980

The rationale of photocoagulation therapy for proliferative diabetic retinopathy: a review and a model.

A model is proposed for initiation and inhibition of growth in retinal vessels including the control of proliferative diabetic retinopathy by photocoagulation. The model assumes that chronic dilatation (constriction) of a retinal blood vessel causes (inhibits) growth. Destruction of rods and cones by photocoagulation allows more choroidal oxygen to reach the inner retina and constrict retinal vessels. The attenuated vessels in late stage retinitis pigmentosa are an analogous and exaggerated effect to that from photocoagulation. The control of proliferative diabetic retinopathy is compared to the cause of retrolental fibroplasma. Following vitrectomy the retina utilizes oxygen from the aqueous which results in dilatation of iris vessels followed by rubeosis iridis. From this model, neovascularization from the disc or angle vessels follows the dilatation resulting from increased flow in their distal vascular beds.

Diabetic Retinopathy↗
PubMed1978

The corneal polarization cross.

The corneal polarization cross can be seen at the human cornea using crossed polaroids. The optical mechanisms for this phenomena include rotation and retardation of the light at the surface of the cornea due to the corneal curvature, as well as retardation due to an average circumferential orientation of the birefringent corneal collagen.

Birefringence↗
PubMed1977

Trichromatic vision in the cat.

Many cat retinal ganglion cells (types X, Y, and W) have inputs from three separate cone systems. Those with peak sensitivities at 450 and 555 nanometers have been previously shown. A gamma max cone with a peak sensitivity of 500 nanometers can be differentiated from other cones by spectral sensitivity and from rods by receptive field differences, functioning above rod saturation levels, and by cone-rod breaks in the dark-adaptation curves. The similarity of the three-cone cat retina to the extramacular retina of the rhesus monkeys suggests that the cat may have photopic trichromatic vision.

Action Potentials↗
PubMed1977

A portable system for external photography.

A portable system for external photography combines a focusing lamp and movable flash unit with a wide focusing range. The system is arranged to operate from a single two-position trigger and may be hand-held or mounted on a slitlamp stand. It is designed for use in general ophthalmology in a multilaned office practice or bedside use in a hospital situation.

Ophthalmology↗
PubMed1976

Levodopa-stimulated growth hormone secretion and diabetic retinopathy.

Since growth hormone has been implicated as a possible etiologic factor in the development of diabetic retinopathy, we examined growth hormone levels in two groups of growth-onset diabetics matched for age and duration of disease. The experimental group had definite proliferative diabetic retinopathy; the control group of growth-onset diabetics had no significant retinopathy. Basal and levodopa-stimulated levels of growth hormone were determined for each group. Growth hormone response could not be correlated with the presence or absence of diabetic retinopathy (P less than .05).

Adult↗
PubMed1976

Visual sensitivity of the eye to infrared laser radiation.

The foveal sensitivity to several near-infrared laser wavelengths was measured. It was found that the eye could respond to radiation at wavelengths at least as far as 1064 nm. A continuous 1064 nm laser source appeared red, but a 1060 nm pulsed laser source appeared green, which suggests the presence of harmonic generation in the retina.

Color Perception↗
PubMed1975

Ultrathin coating by plasma polymerization applied to corneal contact lens.

Plasma coating (deposition of polymer under the influence of plasma) is utilized to modify the surface properties of corneal contact lens. An ultrathin layer (thickness of roughly 200 A) of plasma polymer of acetylene/H20/N2 is applied to poly(methyl methacrylate) (PMMA) corneal contact lenses. The surface becomes highly wettable with water compared to uncoated lens. When coated and uncoated contact lenses are placed on rabbit eyes, a remarkable difference in accumulation of mucous matter is observed. With the control lenses, the accumulation of mucous matter in a week is sufficient to affect the optical clarity of the lenses, whereas the coated lenses show no change after three months continuous wearing. The comparative degree of adhesion of the corneal epithelium cells onto glass, modified glass, PMMA, and coated PMMA surfaces is studied using tissue cultures and phase contrast microscopy. The coated PMMA surface exhibits a degree of tissue adhesion lower than that of control PMMA and higher than that of glass surface, and no sign of toxicity of the coated surface is observed by the tissue cultures.

Acetylene↗