for fresh ophthalmology residents

1. Anatomy of the
Retina
Othman Al-Abbadi, M.D

2. Introduction
• It’s the internal layer of eyeball.
• A thin transparent membrane having a purplish-red color.
• Thickness>> 0.56mm near the optic disc to 0.1mm at the
ora serrata… while it’s thinnest at the fovea centralis.
• Continuous posteriorly with the optic nerve, while
anteriorly with the ciliary body & iris epithelium.
• Bordered by the vitreous internally & the Bruch’s
membrane externally.
• Firmly attached at the margins of optic disc and at its
anterior termination at the ora serrata .
• Approximate landmark on outside of the eye; medially
insertion of medial rectus, laterally insertion of lateral
rectus (closer to the limbus nasally)

4. • It consists of an :
- outer retinal pigment epithelium. (RPE)
(derived from outer layer of optic cup).
- inner neurosensory layer.
(derived from inner layer of optic cup).
• Macula lutea: an oval ,yellowish area ,at the center of
the posterior part of retina… It has central depression
called the fovea centralis.
• The optic disc: a 3-mm depression of the retina where
the optic nerve leaves… pierced by the central retinal
artery & vein… Blind spot.

6. Retinal pigment epithelium
• Hexagonally arranged single layer of narrow & tall
cells from the margin of the optic nerve flattening
gradually towards the ora serrata.
• The basal end of each cell is infolded and rests on a
B.M which forms a part of the Bruch's membrane.
• Apically shows microvili (5-7um long ), which
project between & adhesively bind with rods &
cones but with no specialized attachments.
• The adjacent cell membrane are bound together in
basal region by zonula adherens, and in apical region
by zonula occludens.

7. Melanin granules

9. • Functions:
- Absorption of light.
- Turnover of the outer segments of the rods & cones &
formation of rhodopsin & iodopsin by vitamin A.
- Prevention of scattering by absorption of reflected light.

10. Keep in mind that the remainder of the
optic vesicle is still a potential space
that can separate the RPE from the
retina resulting in Detached Retina

11. Neural Retina
Photo receptors
*Rods:
- 110-125 milion .
- denser at the periphery (absent at
fovea)
- responsible for vision in dim light
producing images of varying shades of
black & white.
* Cones:
- number about 6.3-6.8milion .
- highest density at the fovea
- responsible for color vision in bright light.

14. Bipolar cells
• First order neuron in visual pathway.
• one or more dendrites pass outward to synapse with
photoreceptor cell terminal .
• The single axon is directed inward to synape with
ganglion cell and amacrine cells.
• Types:
- Rod bipolar cells: connecting rods to ganglion cells,
- Flat or diffuse bipolar cell: connect cones to ganglion
cells,
- Midget bipolar cell: connect a single cone cell to a single
midget ganglion cell.

17. Ganglion cells
• Second order neuron in visual pathway.
• Only 100 million ganglion cells in the retina; meaning
more than 100 photoreceptors per ganglion cell.
• Single layer in periphery and increase towards the
macula while completely absent at the fovea.
• Nonmyelinated intraocular & become myelinated just
after leaving the lamina cribrosa.
• The myelin sheath is formed by oligodendrocytes.
• If intraocular part gets myelinated, it results in a blind
spot.

20. • Horizontal cell:
• They have one long & several short processes.
• Inhibitory function by releasing GABA.
• Have a role in sharpening contrast.

22. Amacrine cells
• No axons.
• Stimulated by the Bipolar cells & then they excite
the Ganglion cells.

23. Muller cells
• A supporting cell.

24. Layers of the Retina
1. RPE
2. Rods & Cones
3. External limiting membrane .
4. Outer nuclear layer.
5. Outer plexiform layer.
6. Inner nuclear layer.
7. Inner plexiform layer.
8. Ganglion cell layer .
9. Nerve fiber layer.
10. Internal limiting membrane.

26. Blood supply
• Dual supply:
• The outer laminae (down to the outer nuclear) by the
choroidal capillaries
• The inner laminae by the cental retinal artery & vein
• The integrity of the retina depends on both of these
circulations, neither of which alone is sufficient &
there’s No anastomosis.