Aim: To examine how stereoacuity changes with age as measured by a variety of stereotests. Methods: Stereoacuity has been measured in 60 normal subjects aged 17-83 years by a single observer using TNO, Titmus, Frisby near, and Frisby-Davis distance stereotests. Motor fusion was measured at M metre and 6 metres. Results: Overall stereoacuity measured by all tests showed a mild decline with age (p,0.001 for all tests; Spearman rank correlation). A marked reduction to screening or absent levels of stereoacuity was seen in five subjects aged over 55, but only with the TNO stereotest. All these subjects were able to achieve a stereoacuity of 200 seconds of arc or better with the Titmus test and 340 seconds of arc or better using the Frisby near stereotest. There was a small decline with age in the base out motor fusion range measured at 6 metres (p,0.05; Spearman rank correlation). No subject described difficulty in judging distances for everyday tasks. Conclusions: Although subjects showed some decline in stereoacuity with age by all tests, the large drop in stereoacuity seen in some older subjects using the TNO test was probably due to difficulty overcoming the dissociative effect of the test rather than a true reduction in cortical disparity detection. Results of random dot stereotests should be interpreted with caution in older patients, particularly with respect to their ability to perform everyday visual tasks.

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BTXA is of greatest benefit in patients with residual deviations particularly when the inferior rectus is injected, but is of limited value as a primary therapy in chronic IV N palsy.

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