Subjects were recruited from the Outpatient Department of the Rural Eye Hospital, Sankara Nethralaya, Chennai. One hundred consecutive patients who could read English alphabets and who had unaided visual acuity better than or equal to 6/60 so as to exclude people with severe visual impairment. Consecutive patients visiting the optometrist room, which was standardized for testing and who met the required criteria were included in the study. After obtaining oral consent from the subjects, unaided visual acuity was tested by a trained optometrist using both the newly constructed Pocket Vision Screener and logMAR visual acuity chart. All visual acuity testing was performed by a single examiner. For each subject, right eye was chosen as the testing eye and the other eye was occluded. The chart to be read first was chosen randomly. The randomization was done using the pseudo-random number generator in Microsoft Excel. Subjects were seated at a distance of 3 m from the chart. In the case of visual acuity measurement using the logMAR chart, the subjects were instructed to read from the top left and stop reading until they were not able to read anymore letters. Every correctly read letter was assigned a score of 0.02 and every incorrectly read or unread letter was assigned a score of 0.00. Visual acuity (logMAR) for each subject was determined using the formula:
VA (logMAR) =1.1–0.02 × number of correctly read letters
In the case of the Pocket Vision Screener, the subjects were instructed to read all the letters in the middle line. Correct response of any three letters out of the middle five in the middle line was considered to have passed the screening as more than 50% of the letters were rightly identified. The time taken to measure visual acuity was recorded using a stopwatch for both the logMAR chart and Pocket Vision Screener.
Data analysis was done using Microsoft Office Excel 2003 (Microsoft) and SPSS version 12.0 (SPSS Inc.).