The evolution and persistence of ocular pathology was assessed in a cohort of Onchocerca volvulus infected patients treated annually with
ivermectin for 23 years. Patients were resident in rural Central and Kara Region of Togo and ocular examinations included testing of visual acuity,
slit lamp examination of the anterior eye segment and the eye fundus by ophthalmoscopy. Before
ivermectin treatment, vivid O.
volvulus microfilariae (MF) were observed in the right and left anterior eye chamber in 52% and 42% of patients (nā=ā82), and dead MF were seen in the right and left cornea in 24% and 15% of cases, respectively. At 23 years post initial treatment (PIT), none of the patients (nā=ā82) presented with MF in the anterior chamber and cornea. A complete resolution of punctate
keratitis (PK) lesions without observable
corneal scars was present at 23 years PIT (p<0.0001), and sclerosing keratitits (SK) lessened by half, but mainly in patients with lesions at early stage of evolution. Early-stage
iridocyclitis diminished from 42%(rE) and 40%(lE) to 13% (rE+lE)(p<0.0001), but advanced
iridocyclitis augmented (p<0.001) at 23 years PIT compared to before
ivermectin. Advanced-stage
papillitis and
chorioretinitis did not regress, while early-stage
papillitis present in 28%(rE) and 27%(lE) of patients at before
ivermectin regressed to 17%(rE) and 18%(lE), and early-stage
chorioretinitis present in 51%(rE+lE) of cases at before
ivermectin was observed in 12%(rE) and 13%(lE) at 23 years PIT (p<0.0001). Thus, regular annual
ivermectin treatment eliminated and prevented the migration of O.
volvulus microfilariae into the anterior eye chamber and cornea;
keratitis punctata lesions resolved completely and early-stage sclerosing keratitits and
iridocyclitis regressed, whilst advanced lesions of the anterior and posterior eye segment remained progressive. In conclusion, annual
ivermectin treatments may prevent the emergence of ocular pathology in those populations still exposed to O.
volvulus infection.
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