A retrospective chart review of patients with low vision attending the low vision care clinic of a tertiary eye care center between January and December 2017 was done. The comprehensive list of ocular conditions were categorized by senior Ophthalmologist as conditions causing CFL and PFL respectively. The patients data were categorized into central field loss and peripheral field loss based on the Berkeley Central Field Test (BCFT) and tangent screen test done as a part of low vision work up. Subjects those who presented with both central and peripheral involvement were excluded from this study. Collected data included presenting logarithm of the minimum angle of resolution (logMAR) distant and near visual acuity in the better eye, details of the low vision devices prescribed and post examination logMAR distant and near visual acuity with the low vision device. The low vision assessment and trial were conducted by two experienced optometrists. Institutional review board approval was obtained to analyze the hospital-based data and the tenets of Helsinki were followed.
Low Vision Devices
Distance optical devices were used to magnify objects up to 3 times more, whereas near optical devices were used to magnify printed materials and near objects. Single or multiple optical devices of the following kinds were used to improve the visual acuity of patients with lowvision: SEE TV binocular telescopes (Eschenbach, Germany) are spectacle model telescopes mostly suitable for recognizing faces and watching television in the adult population. Half‑eye spectacles are high‑powered reading glasses that allow both the eyes to read together. These are hands‑free magnifiers which provide a greater field of view and make it more comfortable for users to read and write. Hand‑held magnifiers(Low Vision Resource Centre [LVRC]‑Hong Kong Society forthe Blind [HKSB]) are more comfortable for spotting and give a better working distance and portability. Stand magnifiers (LVRC, HKSB) gives acomparatively wider range of magnification with limited field of view. Dome magnifiers (LVRC, HKSB) provide more comfortability for continuous reading tasks at a convenient working distance. Pocket magnifiers (LVRC, HKSB) are mostly used for spotting as they provide a wide range of magnification. Portable video magnifiers (Freedom Scientific Company, USA) with closed‑circuit television (CCTV) having a magnification from 2x to 25x, offer the option of contrast change, and freezing of images. Notexisa currency identifier are used for identifying notes using tactile cues. Clip‑on filters are colored filters are useful for patients with photophobia. Additional illumination was suggested in most cases for comfortable reading.
The patients were given a trial of single or combination of low vision optical and non-optical devices depending on their presenting visual acuity, and the maximum improvement in the visual acuity was noted. A detailed explanation about handling of the device and adaptation training was given to patients with the preferred device to enable them to handle the device independently. The instruction manual and the other requiremnets of the prescribed device were handed over to the patient.
Levels Of Visual Impairment:
The level of visual impairment was categorized based on the study recommended by the World Health Organization relating the visual acuity of the better eye with the best possible correction:
Category 0: Mild VI with visual acuity better than 6/18,
Category 1: Moderate VI with worse than 6/18–6/60,
Category 2: Severe VI with worse than 6/60–3/60,
Categories 3 and 4: Profound VI with worse than 3/60 to perception of light, and
Category 5: Blindness with no perception of light.
Descriptive statistics included median and Inter-quartile range (IQR) of the variables. Normality assumption was assessed using Shapiro-Wilk test. Wilcoxon sign rank test was used for comparison of continuous non-normally distributed variables of same group. Mann-Whitney test was used for group comparison of continuous non-normally distributed variables of two groups. All statistical analyses were performed using statistical package for the social sciences (SPSS) software version 20. The α (alpha) level was set at 0.05.