Background:
Occult macular dystrophy (OMD) is a rare hereditary macular dystrophy characterized by severe bilateral progressive loss of central vision with normal fundus appearance and normal fundus fluorescein angiography (FFA).
Aim:
The aim of the present study was to assess the correlation between the multifocal electroretinogram (mf-ERG) parameters and best corrected visual acuity (BCVA) in patients with OMD.
Patients and methods:
Twenty eyes of 10 patients with OMD and twenty eyes of 10 age and gender matched normal subjects were included in this study. Full ophthalmic examination, FFA, optical coherence tomography (OCT),full field electroretinogram (ERG) and mf-ERG were performed for all participants. The average amplitude density of P1 wave, amplitude and implicit time of P1 and N1 waves were recorded in the five concentric hexagon rings. The correlation between these mf-ERG parameters and BCVA (LogMAR) were analyzed.
Results:
There were no statistically significant differences in age, gender and refraction between the studied groups (p= 0.54, 1.0 and 0.82, respectively).Mf-ERG parameters in OMD patients showed significant central depression with less affection of peripheral rings. The average amplitude density of P1 wave, amplitude of P1 and N1 waves were significantly reduced in the central rings (ring 1,2 and 3),with less impairment in the paracentral areas(ring 4 and 5).The implicit time of P1 andN1 waves were significantly delayed across the central rings in the OMD patients. The BCVA(LogMAR) was significantly negatively correlated with the amplitude of P1 and N1 waves(p≤0.001).The BCVA (LogMAR) was significantly positively correlated with the implicit time of P1 and N1 waves (p≤0.001).Multiple regression analysis demonstrated that the amplitude and latency of P1 andN1waves in the central rings (1 and 2) were the most important determinants for BCVA.
Conclusion:
Mf-ERG has a key role in detection of OMD and can be considered as a valuable objective test for detection of central/macular dysfunction. The amplitude and latency of P1 andN1 waves in ring 1 and 2 may be used as biomarkers for prediction of visual prognosis in these patients.
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