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Biomedical subjects

W D Townsend

Publications and source records attributed to W D Townsend.

2 recordsLinked to original sources

Scleral depression.

Indirect ophthalmoscopic examination of the peripheral retina is greatly enhanced through the use of scleral indentation. This procedure enables the examiner to better diagnose and manage peripheral retinal anomalies. In this study, the anatomical landmarks and structures relevant to examination of the peripheral fundus are reviewed, along with the various types of instrumentation used in performing scleral indentation. The mechanical techniques used in scleral indentation are discussed as are many of the common errors committed by those learning to perform this procedure. Scleral indentation can be especially valuable in determining the exact nature of lesions noted in the retinal periphery. Case studies in which this procedure was vital to reaching an accurate diagnosis have been included.

Adult

The morphology of the cat tapetum lucidum.

Tapetum lucidum is a comparatively neglected structure found in many species used in vision research. Fundus photography and light and electron microscopy were used in this study to provide more information about the macro- and microstructure of this reflectant layer. In the cat, the tapetum is a lamellar choroidal structure formed by (in cross-section) rectangular cells containing groups of parallel crystal rods. Within each cell these groups of rods lie at various angles to each other but in a plane approximately parallel to the retina. The basal lamina (Bruch's membrane) is poorly developed or absent, and the retinal pigment epithelium contains relatively few pigment granules. It is thought that the function of tapetum lucidum is to reflect light that has not stimulated the retina back into the receptor cells for a second chance of absorption by the visual pigments, thus enhancing night vision.

Animals