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JM Harrison, HA Reitsamer, MM Alvarado-Garcia, JD Roache, A Elkashef, J Mojsiak; S-Cone ERG in Cocaine-Dependent Humans and Controls . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1193.
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Purpose: To determine whether the short wavelength sensitive cone (S-cone) ERG of cocaine-dependent humans is different from that of controls. A previous study showed that S-cone b-wave amplitudes were reduced in cocaine-dependent humans,1 but this finding has not been independently replicated. Method: As part of a larger therapeutic study, we recorded ganzfeld S-cone ERGs from 14 cocaine-dependent subjects (DSM-IV criteria) using cocaine (urinalysis) and 10 age-matched controls. The S-cone ERG isolation by adaptation to a bright yellow ganzfeld is similar to a previously described method.2 The ERGs were produced by 5 flashes/s superimposed on a 6449 td background produced by 15 diffused yellow LEDs (595 nm, 5077 td) and 12 green LEDs (535 nm, 1372 td) presented in a custom ganzfeld (0.2 m diameter). ERGs were produced by "blue", "green", and "red" flashes (Wratten 98, 61, and 29 filters, respectively). Dilated pupil diameter was 8 mm. ERGs were recorded by Burian-Allen-Lawwill electrodes. Results: The S-cone ERG configuration produced by the "blue" flash consisted of a small a-wave (1.3 µV 13 ms), an early b-wave (2 µV, 23 ms), a negative trough (1 µV, 31 ms) a later S-cone b-wave (4 µV, 44 ms), and a large, late negative wave (7 µV, 83 ms) . The ERG produced by the "green" and "red" flashes, whose brightnesses were adjusted to produce approximately the same early b-wave amplitude, lacked the later b-wave and negative wave. No ERG component amplitudes differed significantly in the cocaine-dependent subjects compared to those of controls. Only the peak time of the negative trough (peak time 31 ms) produced by the "red" flash differed significantly (p=0.001) in the two groups. Conclusion: The mean S-cone b-wave amplitude of 20 cocaine-dependent subjects in the earlier study was 48% less than that of 20 controls.1 Our data do not indicate a large mean difference in S-cone b-wave amplitude in the two groups. The power was 0.8 to detect a 40% difference with p<0.05. Two cocaine-dependent subjects, however, lacked the late S-cone b-wave. In the cocaine-dependent population, there may be a subgroup with small or absent S-cone ERGs. The numbers of this subgroup may not be proportionately represented in our sample. 1) M. Roy, et al. Arch Gen Psychiatry 54:153-156, 1997. 2) S.E. Simonsen and T. Rosenberg Doc Ophthalmol 91:323-332, 1996.
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