Teller Cards and Freiburg Acuity Visual Evoked Potential in Children with Poor Visual Behavior

Abstract

Purpose : Visual evoked potential (VEP) acuity test makes estimations of acuity in pre- and nonverbal patients with visual impairment feasible; yet the interpretation of VEP acuity and the relationship to the more commonly measured behavioral preferential looking (PL) acuity test remain incompletely understood. Indeed, the degree of (dis)agreement between behavioral and VEP acuity may contain useful information about the origins of visual impairment. Accordingly, this study compares Teller Acuity Card and Freiburg VEP (FrAVEP) acuities in children with different causes of visual impairment.

Methods : To date, binocular best-corrected acuity has been measured in 32 subjects (23 with cerebral visual impairment, CVI; 9 with other ocular disorders) aged 0.6–15 (median 2) years at test, using both Teller Acuity Card (Stereo Optical Company, Chicago, IL) PL and FrAVEP (Espion E3, Diagnosys, Lowell, MA) procedures (see Bach and Farmer, Doc Ophthalmol, 2019) and compared with 4 healthy controls. Acuities, so obtained, were expressed in LogMAR and plotted against the normal limits of binocular acuity for age. The relationship of acuity to the delta between PL and FrAVEP measures of acuity was investigated. To compare the three groups, analysis of variance (ANOVA) was used.

Results : All subjects had measurable PL and FrAVEP acuities. In nearly all subjects, both PL and FrAVEP acuities were below normal for age. PL acuity spanned 2.08–0.00 LogMAR (Snellen 20/2400–20/20); FrAVEP acuity spanned 1.03–0.17 LogMAR (Snellen 20/215–20/29). There was a strong correlation between PL and FrAVEP acuity tests (r=0.79). However, FrAVEP acuity tended to be better than PL acuity—especially when acuity was poor. That is, the delta between PL and FrAVEP acuity was greatest in subjects with the lowest acuity levels. Three quarters of the healthy controls had better PL than FrAVEP, but only 4 of 9 ocular disorders subjects and a mere 2 of 23 CVI subjects. Furthermore, the delta between PL and FrAVEP was more than twice as large in subjects with CVI as in those with other ocular conditions (P<0.05).

Conclusions : Acuity by FrAVEP exceeded the estimation of acuity by PL. This discrepancy might result from differences in the stimuli, including the stimulated retinal locations. That said, larger discrepancies in acuity measured using both PL and FrAVEP may imply cerebral involvement.

This is a 2020 ARVO Annual Meeting abstract.