The movement of microfilariae of Onchocerca volvulus in the human eye from lid to retina

Abstract

1. 1) A study of the possible routes of entry of mf. of O. volvulus into the different ocular tissues was carried out on 10 eyeballs. 2. 2) Serial sections were made after low-viscosity nitro-cellulose embedding; paraffin was used in the case of the lids. The uveal melanin was bleached, before the sections were stained by the Masson method and a modified phloxine tartrazine technique. 3. 3) It was concluded that the most common route taken by the mf. is from the bulbar conjunctiva into the cornea between the epithelium and Bowman's membrane. The sclera appears to offer a strong barrier to their passage, except at its anterior extremity where its fibres mingle with the corneal lamellae; thence the mf. can reach the uvea. 4. 4) It was also discovered that the parasites traverse the adventitial sheaths of the perforating blood vessels at the limbus, and the equator, and (perhaps) of the nutrient vessels to the optic nerve. 5. 5) It is believed that the presence of mf. of O. volvulus in the retina described in this paper is an original finding, and that the photomicrographs of mf. within the retina, vitreous and the optic nerve are the first ever to be reproduced.