General Anatomy of the Eye & Degenerative Diseases of Human Retina Jennifer Hsieh Psy 159 Physiological Basis of Perception 1/11/2005

Background

Key Terms Vitreous humor – fluid in major chamber of eye. Retina – encodes the info as a neural signal to transmit to the brain. Macula lutea – pigmented central region of the retina containing fovea. Fovea – greatest capacity for fine detail discrimination. Optic nerves – bundle of ganglion cell axons carrying visual info. Cornea – where light enters the eye. Iris – a smooth ring of muscle with a central opening. Pupil – central opening. Lens – helps the cornea to produce a focused image.

Photoreceptors (Rods and Cones) Anatomy of the Retina Photoreceptors  (Rods and Cones) Outer Plexiform Layer Inner Nuclear Layer   Inner Plexiform Layer  Ganglion Cells  R H B A G

The Retina Receptors – absorb photons & begin to create neural signals. Outer plexiform layer – the receptors terminate here. Inner nuclear layer - Horizontal cells: responsive to lights across a wide area of the retina. Bipolar cells: response can be either hyperpolarizing (light falling directly on it) or depolarizing (light falling to the side). Amacrine cells: produce response (transient / phasic) when the light level changed. Inner plexiform layer – signals within bipolar cells conducted to here. Ganglion cells – receive the end products of all the previous processing and communicate it to the brain.

Retinal Photo - Ophthalmoscope

Degenerative diseases of the human retina In some eye diseases, the retina becomes compromised, and the degenerative changes lead to serious damage to the nerve cells that carry the messages about the visual image to the brain.

Age Related Macular Degeneration Age related macular degeneration - the macular area and fovea become compromised due to the pigment epithelium behind the retina degenerating and forming white spots.

Glaucoma Glaucoma - the pressure within the eye becomes elevated. The pressure rises because the anterior chamber of the eye cannot exchange fluid properly by the normal aqueous outflow methods.

Retinitis Pigmentosa Retinits pigmentosa - a hereditary disease of the retina. Most of the faulty genes affect the rod photoreceptors. Characteristic pathology is the occurrence of black pigment in the peripheral retina and thinned blood vessels.

Diabetic Retinopathy Diabetic retinopathy - a side effect of diabetes that can cause blindness. The vital nourishing blood vessels of the eye become damaged, distorted and multiply in uncontrollable ways.

Now that we are done, take the quiz! 1. The _____ transmits electrical impulses from the eye to the brain. A. Lens B. Optic nerve C. Vitreous humor 2. The eye works a lot like a... A. Camera B. Computer C. Projector 3. Below is a view of the fundus of the retina in a patient with ______. A. Glaucoma B. Healthy Eye (Normal) C. Macular degeneration B A A

References Hagerman, G.S. and Johnson, L.V. (1991) The photoreceptor-retinal pigmented epithelium interface. "Principles and Practice of Clinical Electrophysiology of Vision" (Eds. Heckenlively, J.R. and Arden, G.B.) Mosby Year Book, St. Louis, 1991, pp. 53-68. Henkind , P., Hansen, R.I. and Szalay, J. (1979) Ocular circulation. In "Physiology of the human eye and visual system" (Ed. Records, R.E.) pp 98-155. Harper & Row, new York. Kolb, H. (1991) The neural organization of the human retina. In "Principles and Practices of Clinical Electrophysiology of Vision" (Eds. Heckenlively, J.R. and Arden, G.B.) Mosby Year Book Inc. , St. Louis, pp. 25-52. Polyak, S.L. (1941) The Retina. University of Chicago Press, Chicago. Van Buren, J.M. (1963) The retinal ganglion cell layer. Charles C. Thomas, Springfield, Illinois.

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