The hierarchy of required visual ability for the 19 items
(Table 3) shows that the 4 most difficult tasks were all related to activities that require high resolution: reading a textbook at arm’s length, threading a needle, reading destination details of a bus, and copying from the blackboard despite sitting in the front row. All these are significant activities in schoolchildren.
At the easiest extreme of our difficulty hierarchy (those items that required least visual ability) were tasks of daily living, such as applying paste to a toothbrush, locating food on a plate, walking alone in the corridor at school, and walking back home at night, for which the subjects reported little or no difficulty. This implies that vision may not be as critical when subjects are required to do tasks that can be managed by other cues, such as tactual (locating food on a plate and applying paste to a toothbrush). Although we used a 5-point rating scale (0–4) in the present study, the subjects tended to dichotomize their responses. Response category 0 was used 22% of the time and category 4 was used 64% of the time with categories 1, 2, and 3 being used only 2%, 2%, and 6% of the time, respectively. The probability of subjects using categories 1, 2, or 3, was near zero for all values of person-item measure. These response categories were rarely used by our subjects and conveyed no information. Approximately half of our subjects (56.4%) were moderately visually impaired and we expected most of them to respond with “moderate to a great deal of difficulty” in performing the tasks, but they tended to dichotomize the responses (i.e., they answered with the most extreme categories). We speculate that it was difficult for the children to remember the four response categories. In addition, they may not have not been able to make judgments of scale (i.e., they either could perform the task or they could not, and if they could, they did not have any basis for deciding whether they had mild, moderate, or a great deal of difficulty, because they always performed the task that way). All these factors could have led to an infrequent use of the intermediate rating categories. Based on our experience we suggest that the rating scale of the LVP-FVQ could be modified to make it dichotomous and to further shorten the administration time. However, another study with a more heterogeneous (in visual acuity) and larger sample size is needed before such a recommendation can be made.