[Aging changes in ocular tissues and their influences on accommodative functions].

Abstract

It is well known that the amplitude of accommodation deteriorates with aging. However, it is not clear what kinds of morphological changes of age-dependent deterioration of amplitude of accommodation accompany in the crystalline lens and the ciliary muscle, which are the most important involved tissues in the accommodation mechanism. In the present study morphological changes of these tissues were investigated in relation to the deterioration of the accommodative amplitude. Age-dependent deterioration of the subjective amplitude of accommodation obtained by an accommodometer (VDT Accommodometer NP-200, Toyo-Medical, Nagoya) and the objective amplitude by an autorefractometer with a built-in infrared optometer (NIDEK AA 2000 Accommodometer, NIDEK, Gamagori, Japan) were compared. The objective amplitude was 2-3 dptr less than the subjective amplitude for all ages, but change of both curves with aging were parallel. The crystalline lens measured by an ultrasonic A-scan instrument, Alpha 20/20 (Storz, U.S.A.), showed continuous increase in thickness with aging and by accommodative contraction. The crystalline lens in the fifties was as same in thickness as the accommodatively contracted lens in the twenties but the increasing ratio of lens thickness in accommodative contraction decreased with aging and it reached a minimum in the sixties. Scanning electron microscopy (JSM F-15, JOEL Co, Tokyo) revealed three types of characteristic substructures on the cell surface of the crystalline lens fiber, ie, interlocking protrusion, ball-and-socket junction and microplica or the tongue-and-groove junction. In the lenticular nucleus the microplica was prominent on the cell surface throughout all ages but the ball-and-socket junction was sparse in number. On the other hand, the ball-and-socket junction was well developed on the cell surface in the superficial cortex of the lens. The microplica on the cell surface in the superficial cortex was recognizable but indistinct. The microplica and ball-and-socket junction seemed to shift relative to each other in the deeper cortex of the lens. The interlocking protrusion was recognized throughout the whole lens, but was prominent in the lenticular nucleus. The crystalline lens fibers of advanced age were irregural in shape and the spherical substructure, large and small in size, and frequently formed suggesting the cataractous change. Delicate shift of the ciliary processes after conjunctival application of 4% pilocarpine was confirmed by an angioendoscope (Angio Fiber Imaging System FCA-8000. Fukuda Electronics K.K., Tokyo) which was inserted into the vitreous space of cynomorgus monkey eyes.(ABSTRACT TRUNCATED AT 400 WORDS)