Assesment of visual acuity with Sweep VEP in children

To evaluate the visual acuity in children using sweep VEP (sVEP, visual evoked potential), and to compare the results with values obtained from Snellen visual acuity measurements. 216 children aged between 0-17 years were included in the study. Of these, 104 (%48,1) were between 7-17 years old, able to verbally communicate, and not having any systemic or ocular pathologies (Group1). Group 2 included 56 (%25,9) children who were aged between 6-17 years old and can also express their visual abilities verbally, whereas these 56 children were having strabismus, or anisometropic amblyopia whose best corrected visual acuity (BCVA, by Snellen measurements) were between 0,1 ? 0,8. 56 pre-verbal children (%25.9) between 0-5 years old who does not have any systemic or ocular pathology were included in Group 3. All subjects underwent a detailed opthalmological examination. Snellen visual acuity measurements were taken from all children, an the results were noted as BCVA. Also all children underwent a sVEP measurement (Metrovision, Monelec3, France). Average, and maximum sVEP results were recorded. Data were further analysed statistically via paired T test, Pearson corelation analysis, regression analysis, and Bland-Altman method. In Group 1, Snellen BCVA was found to be 0.013±0.007 logMAR, average sVEP acuity was found to be 0.18±0.057 logMAR, and maximum sVEP acuity was 0.10±0.016 logMAR. Average sVEP acuity, and maximum sVEP acuity values were found to be smaller than Snellen BCVA by 0.16, and 0.084 logMAR, respectively. In this group, both average and maximum sVEP values were correlated with Snellen BCVA values (r=0.54, p<0.001; r=0.72, p<0.001, respectively). Bland-Altman analysis revealed that in Group 1, the distribution of the differences between Snellen BCVA and average sVEP was +/-0.11 logMAR, and that between Snellen BCVA and maximum sVEP was +/-0.23 logMAR. In Group 2, Snellen BCVA was found to be 0.24±0.11 logMAR, average sVEP acuity was found to be 0.39±0.10 logMAR, and maximum sVEP acuity was 0.28±0.08 logMAR. Average sVEP acuity, and maximum sVEP acuity values were found to be smaller than Snellen BCVA by 0.15, and 0.04 logMAR, respectively. In this group, both average and maximum sVEP values were also correlated with Snellen BCVA values (r=0.71, p<0.001; r=0.54, p<0.001, respectively). Bland-Altman analysis revealed that in Group 2, the distribution of the differences between Snellen BCVA and average sVEP was +/-0.16 logMAR, and that between Snellen BCVA and maximum sVEP was +/-0.19 logMAR. In Group 3, average sVEP acuity was found to be 0.24±0.07 logMAR, and maximum sVEP acuity was 0.12±0.006 logMAR. These values were correlated with age (r= -0.264, p=0.05; r=0.396, p=0,0025, respectively) sVEP visual acuity measurements reveal comparable results with Snellen acuity results. This technique can reliably used in preverbal, or non-cooperative children for its ease and objectivity. Keywords: Visual acuity, Visual Evoked Potentials, Snellen, Sweep VEP