Effect of retinal illuminance on visual acuity, visual fields and contrast sensitivity in patients with glaucoma, albinism and diabetics retinopathy

[摘要] Introduction:Individuals with low vision may have reduced or impaired visual acuity, visual fields,and contrast sensitivity. This may lead to impaired visual functioning, orientation andmobility. In addition, those patients may have binocular defects, colour defects andpoor visual processing. Patients who are visually impaired as a result of diabeticretinopathy, albinism, and glaucoma have difficulties with execution of many visuallyguideddaily tasks. Visually impaired patients in these three groups (diabeticretinopathy, albinism and glaucoma) report that their visual abilities are verydependent on lighting conditions. Filters and tinted lenses are often prescribed to lowvision patients to mainly reduce their discomfort and sometimes provide improvedvisual performance.Method:Cross-sectional comparative design was used to examine the effect of changing retinalillumination on visual acuity, contrast sensitivity, and visual fields in participants withalbinism, diabetic retinopathy and glaucoma. Measurements of these visual functionswere made with and without 4% transmission neutral grey filters (NoIR U23).Results:In response to reducing the retinal illumination, there was an average significantreduction of 0.12±0.08 log units in visual acuity for participants with albinism whilstthere was a significant reduction of 0.34±0.22 log units in contrast sensitivity.Glaucoma participants showed the average significant reduction in visual acuity of0.06±0.08 log units and an average significant reduction in contrast sensitivity of0.25±0.18 log units. Diabetic retinopathy showed the average non-significantreduction of 0.06±0.14 log units in visual acuity and a significant reduction of 0.31±0.15log units in contrast sensitivity.Central visual fields in albinism participants showed no defects either with or withoutthe NoIR U23 filter. Seven glaucoma participants did not show any visual field defects,whereas nine showed fields defect with the NoIR U23 filter. Four participants withglaucoma showed an improvement with the NoIR U23 filter. On the 50 points scaleused for quantifying visual field size, glaucoma participants showed an averagereduction of 1.6±13.3 points in response to the filters. In diabetic retinopathyparticipants, the average visual fields showed a significant reduction of 6.7±11.7 withthe NoIR U23 filter. Eight diabetic retinopathy participants showed fields defects, andtwelve did not have any visual fields defects.Conclusion:Reducing the retinal illuminance generally causes vision to become worse. Visualacuity and contrast sensitivity become worse with the NoIR U23 filter. Where there arecentral visual field defects with no filter, then these defects usually become larger withthe filter in place. Visual field testing showed no defects for any of the albinismparticipants either with or without the NoIR U23 filter. Within each of the three lowvision groups, there are large variations in the responses to the reduction of lightentering the eye. Some individuals showed substantial changes in response tochanges in lighting conditions while others, with the same ocular condition showedlittle or no change. This has implications for the clinician when prescribing filters.Attention should be given to the individual patient and the way in which they respondto reductions in light levels.

[发布机构] University of the Free State