The lens-coating agent and the electroretinogram.
OBJECTIVE
To investigate the effects of 0.5, 1.0 and 2.5% methylcellulose coating agents on the ERG in normals.


METHODS
A total of 15 healthy volunteers underwent photopic ERG recordings in three experimental protocols comparing 0.5, 1.0 and 2.5% methylcellulose solutions. The conductivity of the solutions was measured.


RESULTS
The difference between 0.5 and 1.0% solutions showed significant changes (p < 0.05) in ERG amplitudes. The 0.5% solution produced approximately 15% higher ERG amplitudes than the 1.0% solution. Comparison between 1.0 and 2.5% solutions did not show significant changes in ERG amplitudes. The conductivity was essentially the same for 0.5 and 1.0% solutions, but conductivity of the 2.5% solution was roughly half of that of the other two solutions.


CONCLUSIONS
Although the 0.5% solution did yield significantly higher ERG values than the 1.0% and 2.5% solutions, the exact mechanism by which this occurs is not known. The source of these differences could arise from a combination of factors such as conductivity, viscosity, or other unknown components of the solutions. ERG laboratories should be consistent in the use of coating agents, and be aware that any change in solution might alter normative values by a modest percentage.
Department of Ophthalmology, Stanford University Medical Center, Stanford, CA 94305-5308, USA.
Alexandra
A
Serrato
Radouil
R
Tzekov
Michael F
MF
Marmor
D000328:Adult; D003261:Contact Lenses; D004553:Electric Conductivity; D004596:Electroretinography / Q000187:drug effects*; D005260:Female; D006801:Humans; D008297:Male; D008747:Methylcellulose / Q000494:pharmacology*; D012160:Retina / Q000502:physiology; D014783:Viscosity
D008747:Methylcellulose