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retina

1. Syarif Hidayat Opthalmology Departement M.Djamil Hospital 2023 RETINA

2. 2 RETINA The retina has the highest rate of oxygen consumption of any tissue in the human body because of its high metabolic activity

3. 3 photoreceptor bipolar vascular cells Amacrine ganglion cells Retinal neurons Müller cells Astrocytes microglia the glial cells Endothelial cells pericytes vascular cells a functional neurovascular unit that transforms light into a neural signal The retina is composed of neural, glial, and vascular components

4. 4 Development of the retina and the retinal pigment epithelium. A, Apposition of the surface ectoderm (E) with the inner wall of the optic cup (arrowheads); the neural retina (NR) is separated from the outer wall and the pigment epithelium (PE) by the subretinal space (*). B, Further invagination of the optic cup with induction of the overlying lens (L) by the NR. The intervening subretinal space separates the NR from the PE Modified with permission from Ryan SJ, Ogden TE, Hinton DR, Schachat AP, Wilkinson CP. Ret i na. 3rd ed. St Louis: Mosby; 2001:5.)

5. The process of phototransduction occurs when cells in the retina sensitive to light convert it into an electrical signal that travels to the brain. Phototransduction Source: AAO BCSC 2022-2023 Section 2: Fundamentals and Principles of Ophtalmology . Page 305-312

6. ROD PHOTO TRANSDUCTION 6 When light hits rhodopsin, it becomes active and closes the cyclic nucleotide-gated channels. This causes the rod's membrane to become hyperpolarized and inhibits glutamate. In the dark, rhodopsin stays inactive and the CNG channels in the outer segment stay open. The rod depolarizes and continuously releases glutamate from its axonal terminal.

7. 7 Schematic representa tion of the phototransduction cascade in photoreceptor outer segments. A , Light-activated rhodopsin (R+) causes levels of cGMP to be reduced via transducin -disinhibited phosphodiesterase (PDE), leading to closure of cGMP voltage–gated channels (CNG) and subsequent hyperpolarization of the photoreceptor cell. B, R+ is deacti-vated through phosphorylation (indicated by Ps) and the binding of the protein arrestin ( Arr ). Phosphorylation is mediated by rhodopsin kinase (RK), which is regulated by recoverin (RV). RV dissociates from RK as calcium levels decrease following closure of cGMP voltage–gated channels. Arrestin binds to phosphorylated R+, completing the process. C, c GMP levels are restored through deactivation of transducin (T) via its intrinsic GTPase activity. PDE activity then decreases and guanylate cyclase activity increases, allowing cGMP levels to rise and opening the voltage-gated channels. cGMP = cyclic guanine monophosphate; GCAP = guanylatecyclase –activating protein; GDP = guanosine diphosphate; GTP = guanosine triphosphate; Tα, Tβ, Tγ = subunits of transducin . ( Redrawn from Ryan SJ, Schachat AP, Wilkinson CP, Hinton DR, Sadda SR, Wiedemann P. Ret i na. 5th ed. London: Saunders/Elsevier; 2013:Fig 14

8. 8 When light hyperpolarizes a cone, the cone hyperpolarizes neighboring horizontal cells. This effect inhibits the horizontal cells, stopping the release of GABA, which depolarizes (disinhibits) the cone by a recurrent synapse A person without cones loses the ability to read and see colors and can be legally blind Cone photo transduction

9. Presentation title 9 Termed S-Cones Blue-Yellow color vision Termed M-Cones Achromatic Contrast (Black and White) Termed L-Cones Red-Green Color Vision TRIVARIANT COLOR VISION

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