THE AGEING EYE zyx Ian L. Bailey Lecturer and Clinic Supervisor, Victorian College F.B.O.A.H.D., L.0.SC. of Optometry, M. S.( lndi ana), B.App.Sc., Paper read to the seminar on Vision and its Protection held on June 1 and 2, 1972, and jointly sponsored by the Victorian College of Optometry and the Safety Engineering Society of Australasia, Victorian Division. ABSTRACT Most of the changes of vision due to ageing are attributable to changes in the crystalline lens. Hardening of the crystalline lens decreases the eye's ability to focus for near vision and so "reading" or "intermediate" glasses become necessary. Flattening of the crystalline lens causes a hyperopic shift in refractive error in the over 40 age group. Pathological conditions such as cataract, glaucoma and retinal degeneration can impair visual performance. Older persons need stronger and more carefully arranged lighting. The aim of this paper is to present an account of the more common changes in vision and visual functions with age and to give some indication of how these changes may affect job performance. These changes will be discussed under three major headings: 1. Changes in the refractive system with age 2. Changes due to eye disorders associated with age 3. Changes in visual function with age 1. CHANGES IN THE REFRACTIVE SYSTEM WITH AGE The refractive system of the eye has two optical elements - the crystal- line lens and the cornea - and their combined focussing power should exactly focus light rays from the object of interest on to the retina if the eye is to be correctly focused. The most significant changes in the eye's refractive system with age comes from changes of the crystalline lens. 1.1 Changes in focussing ability Unlike other tissues of the body the crystalline lens continues to grow throughout life. Each year it becomes bigger, thicker and flatter in curva- ture. The material of the lens progressively becomes stiffer and yellowish. These changes affect its most important function -the provision of adjust- ments of power to the eye's focussing system. Mechanism of accommodation The rim of the crystalline lens is connected to the circular ciliary body by numerous suspensory ligaments. The tension on these ligaments pulls on the lens causing it to become flattened. When the fibres of the circular muscle of the ciliary body shorten, the inside diameter of the ciliary body reduces. The consequent slackening of the suspensory ligaments allows the crystalline lens to bulge, so increasing its optical power. This increase in power is called accommodation. In the emmetropic eye (or in the ametropic eye which has been cor- rected by spectacles), when the ciliary muscle is relaxed and the crystal- Page 297 August, 1972