<prompt> Critical period of development of fixation reflex is2-4 months of age6-8 months of age2 years3 years  <response>: A. i.e. 2-4 months Unilateral cataract in children should be operated early in life because the critical period for development of fixation reflex is between 2 4th months of age.Q Age Visual Development At Bih Eye appear to move randomly there is no central fixation Fovea is not fully developed visual acuity is roughly 660. The retina is almost fully developed at bih, apa from macula which fuher develops after bih till 4-6 months of ageQ Myelination of optic nerve begins in the 7th month in utero reaches lamina cribrosaQie is completed Hypermetropia of 2 to 3D2 Orbit is more divergent 500Q as compared to adult 450 . A-P diameter of eyeball is 16.5 mmQ 70 of adult size which is attained by 7-8 years Corneal diameter is 10 mm.Q Adult size 11.7 mm is attained by 2 yrs. of age The anterior chamber is shallower, the angle deep the lens is more spherical as compared to the adult eye. 6 weeks 112 months Fixation reflex first becomes apparent and eye can follow bright light for a sho distance 2-4 months Critical period for development of fixation reflexQ 4-6 months Refixation reflex develops firmly Macula differentiates 6-8 months Depth perception stas developingQ 6 years Fovea develops completely Full visual acuity of 66 attained If visual developmental process is interrupted during this period by any means eg. high anisometropia, congenital cataract it results in amblyopia which becomes irreversible after few years. If the stimulus deprivation occurs bilaterally severe by the age of 6 months it results in pendular nystagmus on attempted fixation. PAX6 is the master gene for eye development. Binocular Vision Psycho-optical Reflex Fusion Reflex Fixation Refixation Reflex When a normal individual fixes Retinal areas which coordinate visually in the Since the most accurate his visual attention on an object occipital coex so that such an object is seen vision is attained by fovea of regard, the image is formed on with both eyes as single object are ka it is necessary that the eyes the fovea of both the eyes corresponding points. The most impoant pair be rapidly oriented so that separately, but the individual of which is foveae. Nasal half of one retina image of an object of perceives a single image. This corresponds to temporal half of other retina in interest falls upon them or state is called Binocular Single occipital coex. that of a moving object vision. It is a conditional reflex Points on two retinae which are not retained on them. This which is not present since bih corresponding points in this sense of term are ascendancy of fovea is but is acquired during 1., 6 called disparate points and if object forms its maintained by Fixation monthsQ and is completed during retinal images on these, it will be seen double Reflex first few years. Psycho-optical binocular diplopia. If disparity is slight there reflex is tendency to move the eyes so that images may be fused by means of Fusion Reflex 