Aniseikonia is-

Ans. is 'd' i.e., Difference in the size of image formed by the two eyes * Anisoeikonia is defined as a condition wherein the images projected on the visual cortex from the two retinae are abnormally unequal in size or shape. Causes may be : -i) Optical aniseikonia: - When the difference between refractive error of two eyes is of high degree, the image of an object may be of different size or shape in two eyes. So the defect is at refractive structures level.ii) Retinal aniseikonia: - Defect is at retinal level and occurs due to displacement of retinal elements towards the nodal point in one eye due to stretching or edema of the retina.iii) Cortical aniseikonia: - Defect is at higher central level. There is asymmetrical simultaneous perception inspite of equal size of images formed on the two retinae.