True about electroretinogram ?
Ans. is 'd' i.e., 'c' wave is positive wave Electroretinogram The changes induced by the stimulation of light in the resting potential of the eye are measured by electroretinography. It is extinguished or absent in complete failure of function of rods and cones, e.g. pigmentary retinal dystrophy, complete occlution of retinal aery, complete retinal detachment, advanced siderosis etc. Negative 'a' wave represent the activity in rods and cones. Positive 'b' wave arises in inner retinal layers. Positive 'c' wave is associated with the pigmentary epithelium. Uses :? Diagnosis and prognosis of retinal disorders such as retinitis pigmentosa, Leber's congenital amaurosis, retinal ischaemia and other chorioretinal degenerations. To assess retinal function when fundus examination is not possible, e.g. in the presence of dense cataract and corneal opacity. To assess the retinal function of the babies where possibilities of impaired vision is considered.
a' wave is positive wave
'a' wave arises from pigmented epithelium
b' wave arises from rods and cones
'c' wave is positive wave