The Retina: gross anatomy
Items refer to the human eye unless otherwise specified. This section leans heavily on Wyszecki and Stiles (1982) an excellent book.
- In most primates the retina is about 200-250 micrometers thick.
- The primary layers of the retina from outermost surface to innermost surface:
- Pigment epithelium - supporting cells for the neural portion of the retina (photopigment regeneration, blood) it is also dark with melanin which decreases light scatter within the eye.
- Rod and cone layer/Bacillary layer,Layer of photoreceptor cells - contains the outer segments and inner segments of the rod and cone photoreceptors.
- Outer limiting membrane -
- Outer Nuclear Layer (ONL) - cell bodies of rods & cones
- Outer Plexiform Layer (OPL) - rod and cone axons, horizontal cell dendrites, bipolar dendrites
- Inner Nuclear Layer (INL) - Nuclei of horizontal, bipolar and amacrine cells
- Inner Plexiform Layer (IPL) - axons of bipolars (and amacrines), dendrites of ganglion cells
~35 um thick in vitro Macaque Monkey (Dacey, 1989)
~25 um thick in rabbit - may include shrinkage (Famiglietti, 1992a)
- Sublamina A/Outer/Upper two thirds/substrata s1 & s2,near INL: Off-center (Famiglietti & Kolb, 1976; Nelson et al., 1978)
- Sublamina B/Inner/Lower one third/substrata s3, s4 & s5, near GCL: On-center (Famiglietti & Kolb, 1976; Nelson et al., 1978)
- Famiglietti breaks each strata further into an alpha, beta and gama with alpha being closest to the INL and gamma being closest to the GCL (for example, Famiglietti 1992a)
- Layer of Ganglion cells (GCL)- Nuclei of the ganglion cells and displaced amacrine cells
- Layer of optic nerve fibers - fibers from ganglion cells traversing the retina to leave the eyeball at the optic disk.
- Polyak 1941's retinal regions
- Central Island - .17-.24 degrees 50-75 micrometers; longest cones and rod-free. Free of Blue cones (Williams, MacLeod & Hayhoe, 1981)
- Foveola - 1.4 degrees, 400 micrometers; the flat pit of the fovea; about 25,000 cones
- Blood vessel-free area - 1.4 - 2.3 degrees
- Rod-free area - 1.7-2.0 degrees (Polyak) 1.0 degrees (Oesterberg) 500-600 micometers
- Fovea - 5.2 degrees, 1,500 micrometers; about 110,000 to 115,000 cones
- Parafovea - 8.6 degrees, 2,500 micrometers
- Perifovea - 19.0 degrees, 5,500 micrometers
- Optic disk/blind spot (Example found on the net), (Photo found on net)
- Point at which the ganglion cell axons leave the eye ball
- oval which is taller than it is wide
- 1.5 - 1.8 mm x 2 - 2.4 mm
- 5 - 6 degrees x 7 - 8 degrees
- 4.8 mm nasal of visual pole and .47 mm above horizontal median
- 16 degrees temporal and 1.6 degrees below in external field. (I think it is closer to 12.5 degrees in my right eye)
- 15 degrees from foveal center in Macaque (de Monasterio et al., 1985)
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© 1995 Lance Hahn (email@example.com)