Early visual-evoked potential acuity and future behavioral acuity in cortical visual impairment.
OBJECTIVE
Cortical Visual Impairment (CVI) is bilateral visual impairment caused by damage to the posterior visual pathway. Both preferential looking and sweep visual-evoked potential (VEP) can be used to measure visual acuity. The purpose of this study was to determine if an early VEP measure of acuity is related to a young patient's future behavioral acuity.


METHODS
The visual acuity of 33 patients with CVI was assessed using the sweep VEP and a behavioral measure on two occasions. The median age of the patients at the initial visit was 4.8 years (range: 1.3 to 19.2 years), and they were followed for an average of 6.9 years (SD: 3.5 years).


RESULTS
The mean initial VEP acuity was 20/135 (0.735 logMAR), and the mean initial behavioral acuity was 20/475 (1.242 logMAR). The average difference between the two initial measures of acuity was 0.55 log unit, with the behavioral measure reporting a poorer visual acuity in all patients. However, the mean final behavioral acuity was 20/150 (0.741 logMAR), and the average difference between the initial VEP acuity and the final behavioral acuity was only 0.01 log unit. Therefore, the initial VEP measure was not statistically different from the final behavioral measure (t = 0.11; dF = 32; p = 0.45).


CONCLUSIONS
Even though the initial VEP measure was much better than the initial behavioral measure, the initial VEP measure was similar to the behavioral visual acuity measured approximately 7 years later. Sweep VEP testing can be used as a predictive tool for at least the lower limit of future behavioral acuity in young patients with CVI.
Watson
Tonya
T
School of Optometry, University of California, Berkeley, Berkeley, California 94720-2020, USA. twatson@berkeley.edu
Orel-Bixler
Deborah
D
Haegerstrom-Portnoy
Gunilla
G
D000293:Adolescent; D001519:Behavior; D002648:Child; D002675:Child, Preschool; D005074:Evoked Potentials, Visual; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D011930:Reaction Time; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013997:Time Factors; D014786:Vision Disorders / Q000503:physiopathology*; D014787:Vision Tests / Q000379:methods*; D014792:Visual Acuity; D014793:Visual Cortex / Q000503:physiopathology*; D014795:Visual Pathways; D055815:Young Adult