During the APOC/WHO Impact Assessment studies in Nigeria held in 1998 and 1999, one thousand and sixty four randomly selected subjects underwent detailed eye examination in three selected sites namely, Cross River State (rain forest ecological zone), Taraba State (savanna ecological zone) and Kogi State (forest- savanna ecological zone). The general objective of the impact assessment studies was to evaluate the ophthalmological impact of onchocerciasis control (CDTI) in Nigeria, this paper highlights the public health significance of ocular onchocerciasis in three different ecological zones in Nigeria. The presence of ocular onchocerciasis was established in all the study sites, with a predominance of posterior segment manifestations, in the rain forest zone. A blindness prevalenc e of 2.4o/o was recorded in the study, with onchocerciasis being responsible for 13 out of the 43 (30.2%) bilaterally blind subjects identified. Onchocerciasis-induced blindness prevalence was relatively high in the rain forest and forest savanna zones of Cross River and Kogi States with Cross River State having the highest site-specific- prevalence (5/10) 50.0% of onchocercal blindness followed by Kogr with (5/12) 41.7%. Taraba site recorded only 27.3% (3121). Other conditions identified included glaucoma, optic nerve disease and cataract rates of which were also found to be high among the population (6.90/o,6.5 % and8.9oh respectively). Anterior segment onchocercal lesions, punctate and sclerosing keratitis were the predominant features of the infection in Taraba site (14.1o/o and 6.3% respectively), a savanna zone while posterior segment lesions were much more common in the forest zone of Cross-River site. Visual field measurements reflected the predominant posterior segment disease. The need to sustain the present efforts aimed at controlling onchocerciasis through mass ivermectin distribution is fuither highlighted. Integration of other Eye Care Programme for the conffol of glaucoma and cataract, into the community directed treatment initiative of APOC for onchocerciasis control should also be strongly considered, in order to drastically reduce the prevalence and incidence of ocular morbidity and blindness, in Nigeria, especially in the onchocerciasis endemic areas.