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Biomedical subjects

A Eisner

Publications and source records attributed to A Eisner.

31 records · Page 2Linked to original sources
PubMed1987

Sensitivities in older eyes with good acuity: eyes whose fellow eye has exudative AMD.

We compared several indices of foveal visual function between two groups of people aged 60 and older. One group was comprised of individuals who had good acuity in one eye, but had a history of exudative aging macular degeneration (AMD) in the other eye. We measured visual function in these individuals' good eyes only. The second group was a normative group; it was comprised of individuals who had good acuity in each eye. None of the eyes which we tested from either group had funduscopic evidence of macular pathology other than macular drusen and/or hypopigmentation. We found that eyes whose fellow eye had suffered from exudative AMD themselves suffered compromised foveal function, even when they retained 20/20 or better acuity. Losses of sensitivity mediated by blue-sensitive cones tended to be greater for 1 degree than for 3 degrees diameter test stimuli. Absolute sensitivity losses at long test wavelengths were probably due to several factors, including decreased effective cone photopigment density. Slow rates of recovery during dark adaptation were associated with the presence of many macular drusen and/or macular hypopigmentation. Eyes whose fellow eye had suffered from exudative AMD had more macular drusen and hypopigmentation than eyes whose fellow eye had not suffered from exudative AMD.

Aging↗
PubMed1986

Multiple components in photopic dark adaptation.

After extinction of a 580-nm bleach, the rate of decrease of the logarithm of visual threshold to a foveal long-wavelength test is not described by an exponentially shaped function. There is a period of time roughly midway between extinction of the bleach and complete recovery of sensitivity when the threshold does not continue to decrease. The duration of this period can be up to about a minute, depending on the illuminance of the bleach. The departure from an exponential time course of recovery during this period is more evident when the test stimulus is a disk that is defocused on the retina and sinusoidally modulated at 1 Hz than when the test stimulus is a sharp-edged disk that is either flashed for 160 msec or sinusoidally modulated at 1 Hz. Losses rather than plateaus of sensitivity with time are sometimes apparent--depending on the observer and stimulus parameters--roughly midway through recovery when the test is a defocused disk modulated sinusoidally at 1 Hz.

Adaptation, Ocular↗
PubMed1986

Total occlusion does not disrupt photoreceptor alignment.

Previous measurements of the photopic Stiles-Crawford function (SCF) in human observers prior to, during, and after (1) total occlusion, and (2) displacement of the eye's pupil, indicate by inference the presence of a phototropic mechanism which actively maintains photoreceptor alignment. In an attempt to replicate and expand the conclusions of these experiments, full SCFs were measured on three normal eyes and one abnormal eye prior to and after at least 6 days total occlusion. Counter to previous reports, total occlusion induced few if any alterations in the SCF rho value in both the normal and abnormal eyes.

Darkness↗
PubMed1981

Flicker photometric study of chromatic adaption: selective suppression of cone inputs by colored backgrounds.

Flicker photometric equivalence is both additive and transitive when the test and standard are alternated upon a relatively more intense colored background. When the balance of red versus green cone excitation from the background is unequal, the contribution of one cone type to flicker photometric spectral sensitivity may be depressed in relation to that of the other by at least 1 order of magnitude more than Weber's law predicts. The resultant spectral sensitivity is determined predominantly by only one class of cone. The cone spectral sensitivities of normals are then seen to be the same as those of dichromats, although there is some individual variation. A model is developed to explain this surprising phenomenon.

Adaptation, Ocular↗
PubMed1980

Blue-sensitive cones do not contribute to luminance.

By using violet backgrounds we selectively altered blue-cone sensitivity but found no change in flicker photometric sensitivity. This indicates that blue cones do not contribute to luminance as defined by flicker photometry.

Color Perception↗
PubMed1975

Static pressure-flow relation in the total systemic vascular bed of the dog and its modification by the baroreceptor reflex.

To evaluate arterial baroreceptor reflex control of total systemic vascular resistance, we studied the relation between mean arterial blood pressure (P) and mean aortic flow (Q) before and after the reflex was abrogated. In 12 dogs with a perfusion pump interposed at the vena-caval-right atrial junction, Q was kept at 60, 80, 100, 120, and 140 ml/min kg-1 for up to 20 minutes. There was little time-dependent change in P at any of these flows. When the reflex was intact, the mean P-Q curve was only slightly convex to the pressure axis; its linearized slope was 0.55 mm Hg-min-kg/ml and its pressure axis intercept was 44 mm Hg. After section of the sinovagal nerves, administration of hexamethonium (30 mg/kg, iv) and norepinephrine (3-5 mug/kg min-1, iv), or both, the slope became 0.96 mm Hg-min-kg/ml and the pressure axis intercept was about 3 mm Hg. Similar findings were obtained in 3 closed-chest dogs in which P was servocontrolled and Q was measured. Therefore, we think that the conventional practice of calculating total peripheral resistance as P/Q and evaluating reflex control of it in terms of the changes in that value involves only a small error in the moderately sub -and supranormal flow range.

Animals↗
PubMedDate not supplied

A low-cost contact lens for green-only argon-laser photocoagulation.

Filtration of argon laser light to eliminate the blue wavelengths and create a green-only light may be clinically useful in treating macular lesions. To that end, an inexpensive, easy method of modifying a posterior pole contact lens for use with any ophthalmic argon laser to allow only green, not blue, laser light to be used for macular photocoagulation is described.

Contact Lenses↗