Effects on the compensatory responses to positive and negative lenses of intermittent lens wear and ciliary nerve section in chicks

Abstract

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 vitreous chamber depth compared to normal eyes and were thus hyperopic when the lenses were removed. In contrast, adaptation to the -10 D lenses was much slower, was still incomplete after 9 days of lens wear, and in this case, eyes had increased vitreous chamber depth and were myopic without the lenses. Adaptation improved when lens wear was delayed until 7 days after hatching. The effect of interrupting lens wear by periods of normal vision varied with the sign of the lenses worn. Hyperopia was always seen in response to +10 D lenses, although the magnitude of the response decreased as the duration of lens wear was decreased. In contrast, even brief periods of normal vision, i.e., 3 hr, prevented 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.

Very Low Density Lipoprotein

“…Conversely, an insufficient axial growth will place the focal plane of the eye behind the retina: the eye is hyperopic or far-sighted (1). Studies on experimental animal models have demonstrated that emmetropization is driven by visual inputs (2, 3, and 4) and primarily controlled by the retina (2,4). The control of ocular axial growth by visual factors has been extensively investigated in chicken experimental models (3,4).…”

“…Studies on experimental animal models have demonstrated that emmetropization is driven by visual inputs (2, 3, and 4) and primarily controlled by the retina (2,4). The control of ocular axial growth by visual factors has been extensively investigated in chicken experimental models (3,4). Applying negative lenses over the eye of the chicken places the focal plane behind the retina (hyperopic defocus), accelerates axial eye growth and leads to a myopic condition (Lens Induced Myopia, LIM).…”

The Influence of Light Exposure and Seasonal Changes on Short-Term and Longer-Term Changes in Axial Length of the Human Eye

“…However, several animal studies that blocked accommodation in eyes exhibiting active growth (Schaeffel et al, 1990;Schwahn & Schaeffel, 1994;Schmid & Wildsoet, 1996), Chapter 1: Literature review 5 concluded that accommodation is not essential for either natural emmetropization or emmetropization in response to imposed defocus to occur.…”

Vitamin D in Dry Eye and Myopia

“…For example, Schmid and Wildsoet (1996) found that chicks wearing high positive powered lens developed hyperopia, and a short period of normal vision intervention helped to prevent myopia development. Chick model also showed that the defocus induced by negative and positive lenses can be compensated, implying the absence of accommodation cues does not impede the blur signal being recognised by retina (Diether & Schaeffel, 1997).…”

“…The development of refraction in the models of monkey (Hung et al, 1995) and tree shrew (McBrien et al, 1999), can be altered by wearing by positive or negative lenses. Animal models have shown that the development of refraction and axial length during early life can be manipulated by lens wear: a hyperopic defocused image forms behind the retina (using negative lens) causes axial elongation and myopic shift in refraction, whereas a myopic defocused image forms in front of the retina (using positive lens) develops hyperopia (Edwards, 1996;Schmid & Wildsoet, 1996).…”