Assessment of visual evoked potentials in stable COPD patients with no visual impairment

To assess whether patients having stable chronic obstructive pulmonary disease (COPD) with no clinical evidence of visual impairment or peripheral neuropathy have visual evoked potentials (VEP) abnormalities on electrophysiologic evaluation.

In the present study, 80 male subjects with no clinical neuropathy or visual impairment were included; 40 COPD patients and 40 age-matched healthy volunteers. The characteristics of subjects including age, quantum of smoking, duration of illness (in COPD patients only), and spirometric indices {forced expiratory volume in first second (FEV₁), FEV₁/forced vital capacity (FVC) %, and peak expiratory flow rate (PEFR)} were assessed. The mental status was assessed using a questionnaire Mini-Mental State Examination (MMSE) Questionnaire. Electrophysiologic studies for the evaluation of VEP were carried out on computerized equipment. Latency and amplitude of P100 wave were analyzed from the VEP wave patterns obtained through a standardized protocol in both the groups to detect abnormalities in the COPD group. For the COPD group, correlations of P100 parameters with patient characteristics, spirometric indices, and MMSE scores were assessed. Significant abnormality was defined as a variation beyond healthy volunteer mean ± 3 standard deviation.

We observed significantly prolonged latency and decreased amplitude of P100 in both eyes of the patients in COPD group compared with healthy volunteers. Twenty-two of the 40 COPD patients (55%) had significant abnormalities in P100 latency, and three COPD patients (7.5%) had abnormalities in P100 amplitude. The latency of P100 on the right side had statistically significant inverse correlation with FEV₁/FVC% and MMSE score.

Twenty-three of the 40 stable COPD patients (compared with healthy volunteers) were observed to have significant VEP abnormality detected on electrophysiologic evaluation: 21/40 having prolonged P100 latency and only 2/40 with decreased P100 amplitude. The statistically significant correlations were observed only between P100 latency (right eye) and FEV1/FVC as well as MMSE scores. The rest of the correlations were not statistically significant.