[Immunohistochemical study of the extracellular matrices related to accommodation in monkeys]

The mechanism of accommodation was studied by immunohistochemical staining of extracellular matrices in monkey eyes.

Frozen sections from five pairs of post-mortem eyes donated by physiologists were used. The antigens listed in Table 1 were selected, and a 2- or 3-step staining technique was used. Confocal laser microscopy was used to evaluate the staining and take photographs. Many frames were reconstituted for the Figures.

a) The ciliary muscle was divided into circular and longitudinal portions by arrangement of alpha-smooth muscle actin and surrounded by dense nets of alpha-elastin at the inner border under pigmented ciliary epithelium. Elastin nets extended into the stroma of the ciliary processes. In the lens, elastin was observed in the equatorial and central subcapsular area. b) Zonules were heavily stained by fibrillin-1 as bundles. Continuous fibers connected the surface of ciliary processes with the lens capsule, and were also anchored along the ciliary epithelium toward the pars plana. Type IV collagen was seen in circumferential lens capsule and between the lens fibers, especially in the equator and central cortex. c) There was more alpha-1A adrenoceptor in the longitudinal than the circular portion of the ciliary muscle.

Our results provide an argument against Helmholtz's theory, but in favor of Tsherning's theory. The accommodation to near might be accomplished by contraction of circular ciliary muscle held by elastin nets pulling the zonules centripetally. The zonular tension puts pressure on the equator and also pulls the lens capsule anterocentrally. This coordination of the matrices will shorten the equatorial plane of the lens and expand the inter-lens-fiber space, making the polar axis wider. As to the far accommodation, longitudinal muscle will pull the zonules peripherally, narrowing the inter-fiber space.