Effect of Illunmination on Stereoacuity

PURPOSE: To investigate the effect of illumination on stereoacuity and to evaluate adequate illumination for each stereotest. METHODS: We measured stereoacuity by Titmus stereotest, TNO stereotest, Lang stereotest in normal group of 40 cases and strabismus group of 26 cases with five levels of illumination. The statistical analysis was performed to compare the mean stereoacuity between different levels of illumination using Student t-test. RESULT: In Titmus stereotest, stereoacuity improved as illumination increased up to 60 lux, which was statistically significant (P< 0.05). In TNO stereotest, stereoacuity significantly improved as illumination increased up to 200 lux in normal group (P< 0.01), and up to 60 lux in strabismus group (P=0.01). In Lang stereotest, 100% of normal group passed the test under 20 lux or more, and 100% of strabismus group passed the test under 60 lux or more. DISCUSSION: The illumination of 60 lux or more was required for Titmus stereotest and 200 lux or more for TNO stereotest, which was sufficient with the room illumination. Lang stereotest is less influenced by illumination and could be performed under lower illumination than other stereotests.

The Stereoacuity on Child Strabismus 1. Aflalysis of Horizontal Deviations

Eighty children who had horizontal strabismus were examined with Titmus and random-dot stereogram(TNO) for the stereoacuity. The patients were analyzed about visual acuity and types of strabismus. In addition, we also analyzed thirty three patients who received correction surgery for the strabismus for evaluation of the changes of postoperative visual acuity and its relationship to the stereoacuity. The results were as follows: 1. The stereoacuity tested by the TNO was proportional to the change of visual acuity, but that of the Titmus was not proportional. 2. The stereoacuity in the exodeviation was higher than the esodeviation. The stereoacuity in the intermittent exotropia was higher than the constant exotropia, and there was no difference in stereoacuity between the accommodative and nonaccommodative esotropia. 3. The visual acuity was improved postoperatively. 4. The postoperative stereoacuity was also improved. The patients with esodeviation showed more improvement in the stereoacuity compared with that of the patients with exodeviation.