Normative data of Electroretinogram and Visual Evoked Potential in Thai Population

Abstract

Objective: To define normal values of Electroretinogram [ERG] and Visual Evoked Potential [VEP] in different age groups using Viking Select Master Software V7.1.

Methods: ERG and VEP values were measured using Viking Select Master Software V7.1 in selected subjects without history of ocular and/or systemic diseases that affect ERG and VEP values. Results were studied in three groups of age: less than 10 years old, 11 to 40 years old and over 40 years old.

Results: There were 26 eyes in the first group with age range from 6-10 years old [mean 7.8 ± 1.52 years old]. In ERG : the normal values of photopic amplitude of ; a-wave was ≥ 18.57 microvoltage [μV] and b-wave was ≥ 23.82 μV, flickering amplitude of b-wave was ≥ 21.93 μV, scotopic amplitude of b-wave was ≥ 39.12 μV, mesopic amplitude of ; a-wave was ≥ 60.44 μV and b-wave was ≥ 96.84 μV. In VEP : transient flash amplitude was ≥ 20.58 μV and latency was ≤ 94.10 millisecond[ms], transient pattern size 2 amplitude was ≥ 8.61 μV and latency was ≤ 100.00 ms. There were 75 eyes in the second group with age range from 11-38 years old [mean 26.8 ± 7.35 years old]. The values of photopic amplitude of ; a-wave was ≥ 22.56 μV and b-wave was ≥ 20.14 μV, flickering amplitude of b-wave was ≥ 19.35 μV, scotopic amplitude of b-wave was ≥ 32.29 μV, mesopic amplitude of ; a-wave was ≥ 45.05 μV and b-wave was ≥ 78.97 μV, VEP- transient flash amplitude was ≥ 11.64 μV and latency was ≤ 96.78 ms, transient pattern size 2 amplitude was ≥ 4.82 μV and latency was ≤ 88.49 ms. There were 77 eyes in the third group with age range from 41-81 years old [mean 60.1 ± 11.54 years old]. The values of photopic amplitude of; a-wave was ≥ 19.12 μV and b-wave was ≥ 24.59 μV, flickering amplitude of b-wave was ≥ 18.76 μV, scotopic amplitude of b-wave was ≥ 35.60 μV, mesopic amplitude of ; a-wave was ≥ 40.90 μV and b-wave was ≥ 94.09 μV, VEP- transient flash amplitude was ≥ 10.07 μV and latency was ≤ 102.10 ms, transient pattern size 2 amplitude was ≥ 5.34 μV and latency was ≤ 96.00 ms.

Conclusion: We established normal ERG and VEP values in different age group using Viking Select Master Software V7.1 at Siriraj Hospital to distinguish between normal and pathological patients. The values are affected in relation to machine and environmental setting in different laboratory. It is essential for individual laboratories to set their own normal values.