Increase in axial length of the macaque monkey eye after corneal opacification.

The cornea of one eye was opacified in two young macaque monkeys by multiple stromal injections of a suspension of polystyrene particles (latex). Ultrasound measurements showed that the eye with opaque cornea grew at a faster rate, so that after 1 year it was more than 1 mm longer than the normal eye. This difference in axial length was due to elongation of the posterior segment, since lens thickness, depth of anterior chamber, and corneal curvature were identical in both eyes. At histological examination, no pathological changes were observed in the anterior segment of the latex-injected eye except for a scant vascularization of the corneal opacity. The result of this experiment demonstrates that opacification of the corneal has effects on axial length similar to, although less marked than, those on lid fusion and therefore supports our previous conclusion that the myopia caused by lid fusion is triggered by the abnormal visual impact and involves central visual pathways.