CHROMATIC ABERRATION AND ACCOMMODATION - THEIR ROLE IN EMMETROPIZATION IN THE CHICK

The roles of chromatic aberration and accommodation as cues to emmetro pization in the chick were investigated. Myopia was induced monocularl y by lid suture for a period of 1-2 weeks from hatching, after which e yes were reopened and the recovery process followed. Monochromatic lig ht (ML) rearing conditions and ciliary nerve section surgery were used to eliminate chromatic aberration and accommodative activity respecti vely. Control animals were reared in white light (WL). When accommodat ion was left intact, chickens reared under monochromatic light were ab le to recover normally. However, ciliary nerve section produced hypero pia, deepening of the anterior chamber and a tendency towards axial le ns thinning, irrespective of the light conditions used. Hyperopic refr active errors peaked at 4 weeks (mean refractive errors: +5.7 D, +4.21 D for ML, WL groups respectively, 4 weeks), with the ML group still e xhibiting significant hyperopia at 7 weeks. Ciliary nerve section did not prevent the myopic response to lid suture (mean refractive errors: -22.65 D; -25 D for ML, WL groups respectively, 1 week) nor the elimi nation of myopia when eyes were reopened. These data indicate that nei ther accommodation nor chromatic aberration are fundamental to the gro ss operation of the emmetropization process although they may be essen tial for the fine tuning of refraction.