Pattern visual evoked potentials in the assessment of objective visual acuity in amblyopic children

Abstract

The aim of this study was to determine the value of pattern visual evoked potentials (PVEP) to five consecutive check size patterns in the assessment of visual acuity (VA) in children. One hundred unilateral amblyopic (study group) and 90 healthy children with best-corrected visual acuity (BCVA) of 1.0 (control group) were planned to be included. PVEP responses to five consecutive check sizes (2 degrees , 1 degrees , 30', 15', and 7') which are assumed to correspond to VAs of 0.1, 0.2, 0.4, 0.7 and 1.0 Snellen lines were recorded in both groups. Eighty-five children in the study group (85.0%) and 74 children in the control group (82.2%) who cooperated well with PVEP testing were included. Normal values for latency, amplitude, and normalized interocular amplitude/latency difference in each check size were defined in the control group. PVEP-estimated VA (PVEP-VA) in the amblyopic eye was defined by the normal PVEP responses to the smallest check size associated with normal interocular difference from the non-amblyopic eye, and was considered predictive if it is within +/-1 Snellen line (1 decimal) discrepancy with BCVA in that eye. Mean age was 9.7 +/- 1.9 and 9.9 +/- 2.2 years in the study and the control groups, respectively. LogMAR (logarithm of minimum angle of resolution) Snellen acuity was well correlated with the logMAR PVEP-VA (r = 0.525, P < 0.001) in the study group. The Snellen line discrepancy between BCVA and PVEP-VA was within +/-1 Snellen line in 57.6% of the eyes. PVEP to five consecutive check sizes may predict objective VA in amblyopic children.

Assessment of Human Visual Acuity Using Visual Evoked Potential: A Review

“…We can conclude that most studies used the SSVEP technique combined with a frequency-domain analysis method for EEG data, such as Fourier transform, obtaining the amplitude and phase at a specific frequency, e.g., the fundamental frequency of onset-offset mode or second harmonic of pattern reversal mode [ 27 , 56 , 61 , 65 , 66 ]. On the other hand, the transient VEP with a temporal frequency lower than 3 Hz used a time-domain analysis method such as a superimposed average, obtaining the amplitude and latency of a time-domain peak, e.g., P100 [ 67 , 68 , 69 , 70 , 71 , 72 ].…”

“…One combines the independent parts into a system, called a combined system, such as the systems in previous studies [ 7 , 35 , 36 , 68 , 75 , 104 ]. The other is a dedicated system utilized to generate the visual stimulus, record the VEP, and define the acuity in VEP assessment with some necessary auxiliary equipment, such as the Enfant system (Neuroscientific Corp., Farmingdale, NY, USA) [ 61 , 62 , 63 , 80 , 82 , 85 , 93 , 94 , 95 , 108 ], the PowerDiva system developed by Norcia (Smith-Kettlewell Eye Research Institute, San Francisco, CA, USA) [ 13 , 14 , 17 , 52 , 75 , 79 , 83 , 99 , 109 , 110 , 111 ], the RETIsystem (Roland Consult Instrument GmBH, Wiesbaden, Germany) [ 69 , 71 , 72 , 77 , 112 ], and the Freiburg Evoked Potentials (EP2000) system developed by Bach (Medical Center, Freiburg University, Freiburg, Germany) [ 22 , 30 , 31 , 113 ]. Bach and Farmer [ 26 ] evaluated the implementation and outcome quality of the VEP acuity method on commercial equipment (Diagnosys Espion Profile and E3 electrophysiology systems) and found that VEP acuity agreed with subjective acuity to within ± 0.31 logMAR, indicating that this technique can be accessible to more users.…”

“…Another threshold determination method, which is more direct and faster, is called the smallest check size technique [ 10 , 53 , 67 , 84 ], taking the smallest check size that evokes a repeatable and recognizable VEP as the VEP acuity [ 131 ], which was also used in other studies [ 71 , 72 , 105 , 111 , 132 ]. To improve the smallest check size technique, Mackay et al [ 89 ] used a successive approximation algorithm to generate the stimulus, and the visual acuity threshold was defined when the VEP response to three consecutively increasing spatial frequencies was scored as detection, detection, no detection.…”

“…Ridder and Rouse [ 94 ] compared sVEP acuity of pre-amblyopic therapy with Snellen acuity of post-amblyopic therapy, finding that sVEP acuity before the therapy can be used to predict Snellen acuity after therapy. Gundogan et al [ 71 ] verified that pattern VEP can be used to predict objective visual acuity in amblyopic children by using the latency and amplitude of P100 in five consecutive check sizes. Wenner et al [ 31 ] compared VEP acuity with psychophysical FrACT acuity in subjects with anisometropic and strabismic amblyopia, finding that acuity can be markedly overestimated using VEP in amblyopia even though measurements of both VEP and FrACT acuity were highly reproducible.…”

Clinical Ocular Electrophysiology

“…Because of the reflection of the central retinal function, pattern VEP is used to estimate visual acuity in many clinical situations besides optic nerve function [60]. An impaired VEP is anatomically non-specific.…”