The monkey anterior hyaloid bends posteriorly during accommodation in proportion to accommodative amplitude and the sclera bows inward with increasing age in both species. Future descriptions of the accommodative mechanism, and approaches to presbyopia therapy, may need to incorporate these findings.

Decreased lens movement with age could be in part secondary to extralenticular age-related changes, such as loss of ciliary body forward movement. Ciliary body centripetal movement may not be the limiting component in accommodation in the older eye.

Purpose To explore the attachments of the posterior zonule and vitreous in relation to accommodation and presbyopia in monkeys and humans. Methods We used novel SEM and UBM techniques to visualize the anterior, intermediate and posterior vitreous zonule and their connections to the ciliary body, vitreous membrane, lens capsule and ora serrata, and to characterize their age-related changes and correlate them with loss of accommodative forward movement of the ciliary body. We injected α-chymotrypsin focally to lyse the vitreous zonule and determined the effect on movement of the accommodative apparatus in monkeys. Results The vitreous attaches to the peripheral lens capsule and the ora serrata directly. The pars plana zonule and the posterior tines of the anterior zonule are separated from the vitreous membrane except for strategically placed attachments, collectively termed “vitreous zonule,” that might modulate and smooth the forward and backward movements of the entire system. Age-dependent changes in these relationships correlated significantly with loss of accommodative amplitude. Lysis of the intermediate vitreous zonule partially restored accommodative movement. Conclusions The vitreous zonule system may help to smoothly translate to the lens the driving forces for accommodation and disaccommodation generated by the ciliary muscle, while maintaining visual focus and protecting the lens capsule and ora serrata from acute tractional forces. Stiffening of the vitreous zonular system may contribute to age-related loss of accommodation and offer a therapeutic target for presbyopia.

Our findings quantify the movements of the zonule and ciliary muscle during accommodation, and identify their age-related changes that could impact the optical change that occurs during accommodation and IOL function.