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Xiaoying Zhu, Sally A McFadden; Interactions between paired eyes during normal growth and lens compensation in chicks. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4437.
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© ARVO (1962-2015); The Authors (2016-present)
Many animal studies have shown that monocular optical treatment on one eye (either form deprivation or lens treatment) can affect the contralateral untreated eye, in terms of change in refractive error, ocular dimensions, and in certain molecular pathways: Monocular treatment on the treated eye can cause the contralateral eye to change either in the same direction as the treated eye (yoking) or the opposite direction (anti-yoking; Rucker et al., 2009, ARVO E-abstract 3931). We undertook a meta-analysis of the interactions (symmetrical size, symmetrical growth, yoking, and anti-yoking) in axial length (AL) in both untreated normal eyes and chicks wearing a spectacle lens on one eye.
(1) AL from both eyes in untreated chicks (n = 3008) was obtained to study the correlation between paired eyes and changes with age (1-17 days). (2) Another group of untreated chicks (n = 48) were measured on days 7 and 10 to study the AL growth in paired eyes. (3) Chicks wore spectacle lenses of various powers (+/– 5, 7, 10, and 15 D, n = 169) over one eye for various durations (1 to 7 days) and were measured before and after the treatment. The change in AL in the fellow eyes was compared to that estimated from eyes of age-matched untreated animals.
(1) The AL in paired eyes was highly correlated, suggesting symmetrical size, and there was a linear relationship between AL and age (y = 0.065x + 8.39 mm, from 1 to 17 days of age; r2 = 0.36, p < 0.0001). (2) The change in AL in paired eyes was also highly correlated (y = 0.69x + 0.07 mm, r2 = 0.56, p < 0.0001), suggesting symmetrical growth. (3) Both yoking and anti-yoking were observed after positive and negative lens treatments. Yoking effects increased with longer lens-wear durations for both positive and negative lens treatment, and dominated anti-yoking effects which were inconsistently observed and only when the lens-wear period was short.
Eye growth in untreated chicks was tightly regulated, shown with both symmetrical size and growth. While the exact mechanisms are unknown, monocular spectacle lens treatment caused both yoking and anti-yoking in the contralateral eyes. In monocular experiments, anti-yoking might sometimes lead to erroneous conclusions if comparisons are relative to the fellow eye, but such effects can be easily overcome by increasing the lens-wear period to greater than 4 days.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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