Histologic Regions

Question 1

The retina is often described as consisting of which two regions

Answer 1

Peripheral retina and central retina/posterior pole

Question 2

The peripheral retina is designed for

Answer 2

Detecting gross form ad motion.

Question 3

Where does convergence occur

Answer 3

Occurs in the peripheral retina. Bipolar cells can receive stimuli from up to 80 rods.

Question 4

How many layers of ganglion cells in the peripheral retina

Answer 4

Single layer

Question 5

Peripheral retina terminates where

Answer 5

Anteriorly at the era serrata.

Question 6

How does the retina transition into the ciliary body?

Answer 6

Most inner:
Internal limiting membrane of retina–> basement membrane of ciliary body

Middle: Neurosensory retina merges to become a single layer of columnar cells –> non- pigmented epithelium of ciliary body

RPE (retinal pigmented) —-> Pigmented epithelium of ciliary body
Most outer

Question 7

Central retina/posterior pole. Histologically, can be referred to as:

Answer 7

The macula lutea

Question 8

Macula Lueta

• How large
• Located where
• Which photoreceptor is present
• Convergence or non convergent?
• How many layers of ganglion cells?

Answer 8

• A small portion of the center retina located between the superior and inferior temporal vascular arcades.
• 5.5 mm in diameter.
• Cones dominate
• Has more ganglion cells per area than anywhere else due to minimal/no convergence.
• 2 or more layers of ganglion cells.

Question 9

Histologically, the macula lutea can be defined by the presence of 2 or more layers of ganglion cells and xanthophyll. What is xanthophyll.

Answer 9

Has antioxidant (prevents DNA damage) and blue light filtering properties. 2 types:

1. Lutein
2. Zeaxanthine

Question 10

The macula lutea can be subdivided into:

Why is it divided this way?

Answer 10

The perifovea, parafovea, fovea (macula) and foveola (fovea)

Divided based on the number and rows of cells in the nuclear layer. Not easily differentiated on viewing the living retina.

Question 11

Perifovea

• How thick
• How many ganglion cell layers
• Located where

Answer 11

The outermost ring of the macula lutea

• 1.55 mm ring
• has 2-4 layers of ganglion cells.

Question 12

Parafovea

• How thick?
• Properties

Answer 12

Inner to the perifovea

• 0.5mm ring
• Inner nuclear layer (photoreceptors) OPL (outer plexiform layer- synapse between bipolar and ganglion) and GCL (Ganglion cell layers) are thickest in this area.

Inner nuclear layer can be 12 cells thick and ganglion cell layer is 7 cells thick

Question 13

Fovea (clinically, the macula)

Answer 13

1. 5mm in diameter
   - Appears as a darkened region in central retina
   - RPE cells are taller and contain more pigment than anywhere else in the retina.

Question 14

Foveola (Clinically, the fovea)

Answer 14

0. 35 mm in diameter
   - Appears as a depression due to bipolar, horizontal, amacrine and ganglion cells being displaced laterally. This allows light to directly reach the photoreceptors without any interference.
   - Only contains cones, no rods.
   - This is the region of the retina with the highest concentration of cones.

Question 15

Which retinal layers are present in the foveola (clinically, the fovea?)

Answer 15

Outer

1. RPE
2. Photoreceptor layer (elongated, and only cones)
3. External limiting membrane (between inner/outer segments and fibers of photoreceptors)
4. Outer nuclear layer (10 rows of cone nuclei with a 1:1:1 ragtop of cones:bipolar cells: ganglion cells)
5. Outer plexiform layer (synapse between photoreceptors and bipolar cels) This is also called Henle’s fiber layer
   - Cone axons take an oblique course to reach displaced bipolar and horizontal cells.

Question 16

Henle’s fiber layer

Answer 16

Found in the foveola (clinically, the fovea)
Obliquely oriented cone axons are known as henle’s fibers.

The innermost layer before cone axons take an oblique course to reach displaced bipolar and horizontal cells. O

Question 17

Does the foveola (fovea) have any capillaries?

Answer 17

No. Noursed by only the choriocapillaris. Referred to as the foveal avascular zone (FAZ)
Extends just a little beyond the fovea, but allows light to pass unobstructed into the photoreceptor outer segment.

Question 18

Optic disc (optic nerve head)

Answer 18

Site where ganglion cell axons accumulate and exit the eye.
Lacks all retinal elements except the nerve fiber layer and inner limiting membrane.
Because there are no photoreceptors, it creates a blind spot in the visual field.