[Quantitive evaluation of metamorphopsia in macular disease]

Visual acuity loss and scotoma are not the only functional consequence of macular disease. Frequently, patients also complain of metamorphopsia. Such visual distortion should be taken into account when evaluating the potential benefit of surgical procedures in macular disease. The Amsler grid does not allow any quantified analysis. In addition, a precise confrontation of the macular lesion with its functional consequences is not possible by this test. We present a new method for analyzing metamorphopsia in macular disease.

Opto-acustic modulation controlled laser emission allowed to generate a retinal image of 256 squares with an angular size of 1 degrees each. The subject was instructed to fixate the center of the grid and to push a handheld button every time he perceived abnormalities within the presented pattern. At the end of the procedure, the responses were represented on graph superimposed on the fundus image. 15 eyes of 15 successive patients complaining of metamorphopsia were included in this preliminary study. Informed consent was obtained prior to inclusion. All patients reported abnormalities on standard Amsler testing. The test-retest reliability was evaluated by repeating the same procedure between 2 hours and 7 days after the first procedure.

The evaluation of 3 patients did not provide reliable information on metamorphopsia because of instable fixation. In 12 patients, a coherent response was obtained. In 9 eyes, the result was unchanged when repeating the procedure, concerning both the number of abnormal elements and their spatial distribution.

The preliminary results appear to be encouraging, indicating a good reproducibility of the results of this method. They should be confirmed on a larger scale. Further work is necessary to evaluate the interest of this method in assessing functional results of macular surgery.