Fixation stability and macular light sensitivity in patients with diabetic maculopathy: a microperimetric study with a scanning laser ophthalmoscope.

BACKGROUND

In patients with diabetic maculopathy, evaluation of visual acuity alone may not represent central retinal function sufficiently. Despite good visual acuity, patients may suffer from visual disturbances like waviness, relative scotoma, loss of fixation and decrease of contrast sensitivity. The aim of the study was to assess localized light sensitivity in the central visual field and to determine fixation stability in patients with diabetic maculopathy with moderate visual loss in comparison to healthy controls.

METHODS

Twenty-seven patients (mean age: 54 +/- 15; range 17-81 years) with diabetic maculopathy and 61 controls (mean age: 45 +/- 22; range 18-85 years) were included in the study. Light sensitivity was quantified by presenting stimuli with different light intensity with simultaneous real-time monitoring of the retina (intensity: 0-27.9 dB; size: Goldmann III, wavelength: 633 nm). Eye movements were controlled by semiautomatic fundus tracking. Fixation stability was quantified by measuring the area within 75% of all points of fixation.

RESULTS

Fixation stability was significantly decreased in diabetic patients in comparison to controls (43 +/- 22 vs. 31 +/- 16 arc min, p < 0.01). There was a significant difference in macular light sensitivity in diabetic patients compared to controls (19.6 +/- 0.5 dB), both in mean difference (15.6 +/- 1.4 dB) and if affected with macular edema (16.1 +/- 4.5 dB), hard exudates (13.3 +/- 6.7 dB), nonperfusion areas (10.3 +/- 7.9 dB) and laser burns (3.0 +/- 6.1 dB). Temporal parts of the macula were more affected than other parts. No correlation was found between visual acuity and foveal light sensitivity and foveal fixation, respectively.

CONCLUSIONS

Macular light sensitivity decreased progressively with the kind and severity of retinal alteration independent of visual acuity. The assessment of macular light sensitivity and stability of fixation with automatic threshold microperimetry may help to identify patients with diabetic maculopathy and could improve the management of diabetic maculopathy.