Patterns of visual function abnormalities in HIV positive children attending Harare Central Hospital's paediatric opportunistic infections clinic
Mutungamiri, Tendayi Denford
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Vision is composed of five simultaneous functions: visual acuity, colour vision, contrast sensitivity, visual field and stereopsis. These functions of vision are affected by disease processes that affect individual structures of the eye and the visual pathway. Human Immune Deficiency Virus (HIV), Highly Active Antiretroviral Therapy (HAART), Opportunistic Infections (OI) and the drugs used in their treatment have an effect on the eye and the visual pathway. This makes HIV positive children more likely to have poor visual function than the general paediatric population, however there is limited data available on visual function in HIV positive children both in Zimbabwe and sub- Saharan Africa. OBJECTIVES 1. To characterise the patterns of selected visual function abnormalities (contrast sensitivity and colour vision) in HIV positive children attending an Opportunistic Infections clinic. 2. To quantify the prevalence of contrast sensitivity and colour vision abnormalities in HIV positive children. 3. To establish the existence and type of association between either of these visual functions and CD4+ T cell count, WHO HIV clinical stage and previous anti-Tuberculosis treatment. DESIGN This was a cross sectional study of patients attending the Harare Central Hospital’s paediatric Opportunistic Infections Clinic, Harare, Zimbabwe. METHODOLOGY Systematic sampling was used to recruit participants. A structured questionnaire was used to gather patient information. A complete ocular examination was done inclusive of Visual acuity (Snellen chart), colour vision (Ishihara plates), Contrast sensitivity (Pelli Robson chart), Slit lamp and dilated fundus examination. RESULTS 1. A total of 168 participants were enrolled into the study (age range 7-12 years). BCDVA was better or equal to 6/12 in 98.8% of the participants. 2. The mean Log CS was 1.71 (range 1.2-1.95), with a standard deviation of 0.12. 3. The prevalence of poor contrast sensitivity was 12.5%, that of colour vision abnormality was 1.8%. 4. An association was established between poor contrast sensitivity and decreasing CD4+ T cell count (p=0.05). 5. Participants on HAART had a lower Log CS than those not on HAART (p=0.002). 6. Participants on second line HAART therapy had a lower Log CS than those on first Line HAART therapy, (p=0.02). 7. There was no associations established between previous anti TB treatment in participants and abnormalities in contrast sensitivity (p=0.63) and colour vision (p=0.50). CONCLUSION This study showed that poor contrast sensitivity is common in HIV positive children, with decreasing CD4+ T cell count being associated with poor contrast sensitivity. Contrast sensitivity abnormalities were found to occur even with good visual acuity.