EFFECTS ON THE COMPENSATORY RESPONSES TO POSITIVE AND NEGATIVE LENSESOF INTERMITTENT LENS WEAR AND CILIARY NERVE-SECTION IN CHICKS

This study examined the ocular compensation to lens-induced defocus in chick and the effect of interrupting lens wear on a daily basis. Eyes fitted with +10 D lenses at hatching compensated rapidly, with almost complete compensation after 4 days of lens wear; they had decreased v itreous chamber depth compared to normal eyes and were thus hyperopic when the lenses were removed. In contrast, adaptation to the -10 D len ses was much slower, was still incomplete after 9 days of lens wear, a nd in this case, eyes had increased vitreous chamber depth and were my opic without the lenses. Adaptation improved when lens wear was delaye d until 7 days after hatching. The effect of interrupting lens wear by periods of normal vision varied with the sign of the lenses worn. Hyp eropia was always seen in response to +10 D lenses, although the magni tude of the response decreased as the duration of lens wear was decrea sed. In contrast, even brief periods of normal vision, i.e., 3 hr, pre vented the development of myopia in response to the -10 D lenses; this apparent sensitivity to normal vision is similar to that reported for form-deprivation myopia. Ciliary nerve section used here to eliminate accommodation did not alter these response patterns.