Doctoral Dissertations

Date of Award

6-1969

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

H.V. Shirley Jr

Committee Members

O.E. Goff, R.C. Fraser, R.L. Murphee

Abstract

A series of 12 experiments was conducted to study factors involved in the development of ophthalmacrosis in chickens.

It was found that exposure of chicks to continuous light, regardless of color or intensity, caused the eyeballs to enlarge, but more strikingly that continuous darkness caused the enlargement to an even greater extent. Breaking the day into long, short, or superimposed photoperiods resulted in less apparent eye enlargement than was found in birds exposed to a continuous lighting regime. When the birds were exposed to a diurnal light cycle the eyes appeared to be unaffected.

Chicks hatched from eggs incubated in continuous darkness appeared to have ophthalmacrosis at hatching time; however, when the chicks were subsequently placed under a diurnal light cycle they returned to normal. When these chicks were placed under a continuous lighting regime upon hatching the condition continued to worsen and permanently impaired vision resulted.

Regardless of whether the birds were placed under a continuous lighting regime from 0-8 weeks or from 6-22 weeks of age they developed ophthalmacrosis; however, the symptoms appeared more slowly in the 8-22 week period. When birds with ophthal macrosis were switched to a diurnal light cycle from 8-22 weeks all returned to normal but with varying degrees of retinal damage. Switching birds with normal eyes to a continuous lighting regime from 8-22 weeks of age resulted in varying degrees of ophthal macrosis and retinal damage. In all cases the degree of retinal damage was positively related to the degree of ophthalmaorosis.

The development of ophthalmaorosis was found to be related to the accumulation of excess amounts of sodium and water in the eye.

The effects of pinealectomy, estrogen implantation, and the feeding of thiouracil and protamone on the development of ophthalmaorosis were studied. The relationships of pituitary, bursa, and thyroid weights to ophthalmaorosis were determined,

A hypothesis, involving the hypothalmic-pituitary-adrenal complex, to explain the development of ophthalmaorosis is presented.

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