Using visual thresholds to establish low vision performance.

Table 6 gives an example of a similar task (N10 print of 75% contrast) but with different requirements of fluency showing how much extra visual performance (acuity threshold, contrast threshold and magnification) is needed to achieve fluent reading. After the clinical assessment of visual function, it should be possible to categorize clients into three different groups on the basis of their threshold visual performance, each needing a different approach depending on their goals and needs as shown in Table 7. These are: Group I: Limited or no survival reading potential. Group II: Survival reading potential but limited likelihood of fluency. Group III: Clear survival reading potential with fluent reading possible if motivated. The author believes that it is always best to start with what the client has to read in order to maintain their independence, rather than what they wish to read for leisure, education or employment. Therefore, it is more successful to concentrate initially on spot/survival reading even if the client seems to have potential for regaining fluency. It should, however, be made clear to the client that this is the approach to be adopted. It is futile for the practitioner, as well as frustrating and demoralizing to the client, to press ahead with complex devices or wasteful trial and error sessions if, at an early stage, it is clear that the client will never return to fluent reading. Instead, it is far better to begin the move to vision substitution (e.g. audio-tapes) for leisure reading at an earlier stage. The overriding influence in low vision management is clearly the motivation of the client.(ABSTRACT TRUNCATED AT 250 WORDS)