[The F-L test for determining alternating central scotoma].

BACKGROUND

Based on their experiences several authors consider an alternating central scotoma as the main reason for reading difficulties due to dyslexia.

METHODS

Searching for a simple and reliable method for determination of an alternating central scotoma we used a pair of synoptophore fusion images, in the center of which we added the letter F respectively L as central control signs. A spontaneously perceived and persisting E means a perfect and stable orthophoria. A persisting F or L with fusion of the images means a one sided central scotoma. Alternation of F and L with fusion of the images means an alternating central scotoma.

RESULTS

By examining normal readers, untreated asthenopic and untreated dyslexic patients, we found mostly rapid alternation of F and L in the latter two groups, whereas most of the normal readers saw F, L and E alternating at longer intervals.

CONCLUSIONS

Thus undisturbed reading seems not to demand perfect orthophoria. On the other hand a rapidly alternating central scotoma may be considered as an important factor causing reading difficulties.