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C.F. Wildsoet, V. Padmanabhan; Patching Fellow Eyes During Subjective Night Does Not Prevent Disruption to Minus Lens Compensation in Constant Light Chicks . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1984.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Constant light (CL) produces shallow anterior chamber (AC), flatter cornea and deeper vitreous chamber (VC) in chicks. It also disrupts emmetropization to minus lenses but not plus lenses (ARVO 2004). This study investigated whether the protective effect for normal growth afforded by covering one eye during the subjective night of CL chicks (Li & Howland 2003) extends to compensation to minus lenses. Methods: Five day–old White Leghorn (Gallus gallus domesticus) chicks were reared in CL for 2 weeks. Right eyes wore a light–proof patch during the subjective night. The left eyes were left unpatched and in the second week, were treated with either –10D or +10D lenses (n=5,6) or left without a lens (n=6). Refraction, corneal curvature and intraocular dimensions were measured at baseline (day 5), & 7, 9 & 14 days later using retinoscopy, keratometry and high–frequency A–scan ultrasonography, respectively. Changes from baselines in lens treated eyes are compared to the no–lens eyes and reported below as mean difference, S.D. Results: Unpatched no–lens eyes showed typical CL–induced anterior segment changes, but were protected from CL–induced VC and optical axial length (OAL) elongation. Patched eyes were completely protected from all CL effects. The CL–plus lens eyes became more hyperopic (+9.2, 1.4D, p<0.0001), with shorter VCs (–0.46, 0.11mm, p<0.0001) and OALs (–0.54, 0.11mm, p<0.0001), than the CL–no lens eyes. The CL–minus eyes also became more hyperopic than CL–no lens eyes (+5.4, 2.8D, p<0.001), although decreases in OALs and VCs, relative to CL–no lens eyes, did not reach statistical significance. Conclusions: Patching one eye of CL chicks during the subjective night does not preserve emmetropization in the unpatched eye; minus lenses failed to induce the usual myopic shifts, just as seen with unpatched CL chicks (ARVO 2004). Because emmetropization is largely a local ocular phenomenon, these data argue for local effects of CL in addition to the humoral systemic influences that presuamably underlie the protection seen in no–lens eyes. The differential effects on AC and VC dimensions in the latter case also argue for their independent regulation.
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