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Biomedical subjects

R A Weale

Publications and source records attributed to R A Weale.

At least 73 records · Page 4Linked to original sources
PubMed1983

Senile cataract. The case against light.

A photochemical theory of the etiology of senile cataract is developed on the assumption that observed prevalences are representable by cumulants of tolerances, the latter being distributed normally and depending in a quantitatively defined way on the amount of short-wavelength radiation absorbed during life. The theoretical risk-curves are consistent with the observed ones. The variation of the predicted and observed values has a slope not differing significantly from unity, but the intercept differs from zero. It is concluded tentatively that the photochemical hypothesis accounts for the observations better and better as age advances, and more so where the radiation is more intense.

Aging↗
PubMed1982

The age variation of "senile' cataract in various parts of the world.

As its name implies, senile cataract is age-related. A survey of 9 studies indicates to what extent the epidemiology of senile cataract can be represented by Gompertz plots. These are shown to be suitable separately for men and women and to enable one to distinguish between inborn and environmental influences. Further support is obtained for the view that myopia and cataract may be linked, and attention is drawn to the potentially noxious effect of (ultraviolet) light.

Age Factors↗
PubMed1981

On the problem of retinal directional sensitivity.

When two physically similar pencils of light enter the eye, one through the pupillary centre and the other near the edge, the former appears brighter and, when monochromatic light is used, generally as thought it were of a shorter wavelength. This is usually attributed to the photoreceptors, notably the cones, being more sensitive to light travelling along them axially than to light with a radial component. However, allowance has also to be made for pre-retinal factors. One of these is the angle of incidence on the cornea; the Fresnel formulae show that, at perimetric angles less than 15 degrees, the ensuing asymmetry in the fractions of light lost by the two pencils needs compensating. Furthermore, a correction is required for differential light absorbance along different paths in the crystalline lens. Finally, the narrowness of the pencils necessitates the application of diffraction theory: the harmonic content of a light beam varies inversely with the distance between its point of pupillary entry and the optic axis, the effect varying across the spectrum. The above corrections suggest that there is little difference between the directional sensitivities of human rod and cone mechanisms; the above chromatic effect can be explained partly on the basis of pre-retinal factors, and earlier theoretical explanations are rendered more plausible.

Animals↗
PubMed1981

Human ocular aging and ambient temperature.

A survey of the literature on the incidence of the age of onset of presbyopia in various parts of the world reveals a great deal of variation. At first sight this appears to correlate with geographical latitude, but statistical and epidemiological evidence rules this out in favour of ambient temperature. Indirect evidence suggests that the crystalline lens is located sufficiently near to the surface of the body for this to be a likely explanation.

Adult↗
PubMed1979

Now let me see.

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Developing Countries↗
PubMed1978

The perimeter as a monitor of glaucomatous changes.

A small group of glaucoma patients with scotomata were compared with normal coevals. Plots were obtained of the error of each measurement as a function of retinal illumination. A statistical analysis shows the limitations of perimetry as a monitor of the progress of glaucoma. The significance of the data is discussed.

Glaucoma↗
PubMed1978

Rhodopsin and visual threshold in retinitis pigmentosa.

Rhodopsin kinetics and visual threshold were determined in three subjects with a dominant form of retinitis pigmentosa. The retinal areas studied showed varying loss of sensitivity, which correlated well with the reduction in the measured density of rhodopsin in the test region. Rhodopsin photosensitivity was normal, and there was no evidence that either rhodopsin or the cone pigments regenerated more rapidly than normal. The findings in these cases of retinitis pigmentosa, when compared with the threshold changes induced by vitamin A deficiency or photic bleaching, suggest that the disease produces an imbalance between disc removal and new disc formation, which results in a progressive shortening of the photoreceptor outer segments and, eventually, in their complete disappearance.

Adult↗
PubMed1977

Sun-glasses.

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Eyeglasses↗