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Effects of continuous light on experimental refractive errors in chicks
Author(s) -
Guo S. S.,
Sivak J. G.,
Callender M. G.,
Herbert K. L.
Publication year - 1996
Publication title -
ophthalmic and physiological optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.147
H-Index - 66
eISSN - 1475-1313
pISSN - 0275-5408
DOI - 10.1046/j.1475-1313.1996.96000117.x
Subject(s) - dioptre , retinoscopy , refractive error , ophthalmology , keratometer , vitreous chamber , lens (geology) , medicine , cornea , optometry , emmetropia , optics , eye disease , visual acuity , physics
Summary It is possible to induce ametropias in young chicks either by depriving the developing eye of clear form vision with a translucent goggle or by defocusing the retinal image with convex or concave lenses. The refractive properties of the developing chick eye are also altered by raising young birds in a continuous light environment. The effects of superimposing form deprivation or defocus treatments on chicks raised in continuous light are unclear. Newly hatched ( n = 31) chicks were raised for 2 weeks under continuous light while wearing either translucent goggles or + 10 or − 10 diopter (D) lenses over one eye. Refractive states, corneal curvature and intraocular dimensions were measured periodically by retinoscopy, keratometry and A‐scan ultrasound. The birds were sacrificed after 2 weeks and the eyes removed and measured with calipers. Under continuous light, all eyes treated with translucent goggle and − 10D lens developed moderate myopia (− 2.6 ± 0.5 D and − 1.4 ± 0.3 D, respectively) by day 4. The eyes treated with a + 10 D lens developed moderate hyperopia (+ 4.8 ± 0.5 D) at day 4. Corneal curvatures of all treated eyes were slightly, but significantly, larger than contralateral control eyes by day 4. After 2 weeks of goggle or lens application, all the treated eyes were hyperopic due to corneal flattening. But the eyes treated with a goggle or a − 10 D lens still showed relative myopia compared to the fellow eyes (treated minus untreated = − 3.8 ± 0.4 D and − 2.8 ± 0.4 D, respectively), and the eyes treated with a + 10 D lens showed more hyperopia than fellow eyes (treated minus untreated = + 5.1 ± 0.6 D). Compared with the control eyes, the axial length (mainly vitreous chamber depth) was slightly, but significantly, increased in the eyes treated with a goggle or a − 10 D lens, and the axial length decreased slightly in the eyes treated with + 10 D lens. The results suggest that form deprivation and retinal defocus (induced by ± 10 D lenses) could still induce experimental refractive errors (myopia and hyperopia) in chicks kept under continuous light, but the effects of form deprivation and retinal defocus were partially suppressed by continuous light.