Age-Related Changes in Human Ciliary Muscle

PURPOSE: To examine the role of the ciliary muscle in accommodation and presbyopia. METHODS: Sixteen pairs of eyes from donors aged 1 to 107 years were treated with atropine or pilocarpine and then processed for light microscopy. Seven pairs were analyzed for treatment effects, including morphometric measurements of muscle dimensions, muscle fiber group area, and the percentage of connective tissue. RESULTS: The ciliary muscle shortened in length in response to drug treatment at all ages. The ciliary muscle of older subjects contained greater amounts of connective tissue and was shorter, wider and the internal apical edge moved forward. CONCLUSIONS: This study confirms previous reports that the human ciliary muscle retains its ability to contract throughout the lifespan. However, the ciliary muscle also displayed age-related changes, which may be partly accounted for by the forces exerted from the aging lens and zonules.