![]() Convergence of the eyes The near response. ![]() Īccommodation Definition: Modification of the refractive power of the eye (curvature of the lens) to view a nearby object Goal: Clear vision of a nearby object Therefore, a lesion in optic tract will cause loss of vision from the ipsilateral nasal field of vision + contralateral temporal field of vision.Therefore, each optic tract carries fibers from the both the temporal side of the ipsilateral retina + nasal side of the contralateral retina.Optic nerve fibers from the lateral ( temporal ) parts of the retinae do not decussate.Therefore an Optic Chiasma lesion ( e,g, Pituitary Tumor ) will cause vision loss from the both lateral halves of the Field of Vision.Optic nerve fibers from the medial ( nasal ) side of retinae decussate in the Optic Chiasma.Optic nerve 2.Optic chiasm 3.Optic tract 4.Lateral geniculate body (nucleus) 5.Optic radiation 6.Visual cortex Passing through the Blind Spot they leave the eye, constituting the Optic Nerve.These axons converge at the Optic disc ,which is also called Blind Spot Axons of Ganglion Cells constitute the Optic Nerve.Photoreceptors :Rods and Cones synapse on Bipolar Cells, which in turn, synapse on Ganglion Cells.( Pathway from Retina to the Visual Centers in the Brain ).A person of 6/12 has less vision than normal vision.is minimal amount of light that elicit sensation of light.-(person can normally distinguish two separate points if their centers lie up to 2 micrometers apart on the retina, which is slightly greater than the width of a foveal cone) Visual threshold:.it is usually defined in terms of the shortest distance by which two lines can be separated and still be seen as 2 lines.Degree to which details of objects are perceived.Objectives At the end of this lecture the student should be able to: Describe visual acuity & depth perception To know visual pathway and field of vision Describe the process of accommodation reflex and its pathway, Identify and describe pupillary light reflex, its pathway and relate these to clinical situations as Argyl Robertson pupil Identify the lateral geniculate body and visual cortex functions. Physiology of Vision Lecture-2-Accommodation & Pupillary Light Reflex Dr.SalahElmalik
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