Correlation of Ocular Onchocerciasis with the Refractive Status of the Eye among Selected Endemic Communities in Imo State, Nigeria

Abstract

Background: The study was aimed at investigating the correlation between ocular onchocerciasis and refractive status of the eye among selected endemic communities in Imo State, Nigeria.

Methods: A total of 462 participants aged 5-84 (44.9 ±12.1) years and comprised of 238 (51.5%) males and 224 (48.5%) females were sampled. Blood-free skin snips were collected using the skin snip biopsy technique. Bloodless skin snips were extirpated from the iliac crest region using a sclera-corneal punch which resulted in the removal of around 2 mg of tissue. To allow the microfilariae emerge, the tissue removed was incubated in normal saline at room temperature for 24 hours. The emerging microfilariae were then identified under a high powered 40X microscope. Out of the 462 participants, 221 (47.8%) tested positive to O. volvulus. Of the 221 that tested positive, 104 (47.1%) (male, 69 and female, 35) had ocular manifestations. Ocular examination was performed on positive individuals using the slit lamp biomicroscope under retro illumination.

Results: Using the chi square statistical analysis, this study showed a statistically significant difference (P<0.05) between onchocerciasis and the refractive state of the eye in Amuro, Umulolo, Amano and Umuokpara community and odds ratio showed that onchocerciasis was more likely to cause these errors. There was no statistical significant difference (P>0.05) in the refractive state of the eye in Ihube.

Conclusions: The result suggested that presbyopia had a higher manifestation while hyperopia and astigmatism had the least manifestation than other refractive errors. The result from the study showed a decline in the 5 studied communities but the presence of positive diagnosis suggests of a continuous disease transmission and onchocerciasis is not yet fully eliminated in Okigwe. With sustained high coverage of ivermectin mass drug administration by African Programme for Onchocerciasis Control (APOC), onchocerciasis prevalence would be eliminated.

Keywords: Ocular onchocerciasis, Refractive status, Eye, Endemic communities.