OCAP PPT

Group # 5

Retinal Pigmented Epithelium ( RPE )

Retinal Pigmented Epithelium

By: Padilla, Angelic NorefilGross description:

1. Consist of single layer of cells that extends forward from the margin of the optic nerve to the ora serrata anteriorly.

Retinal Pigmented Epithelium

2. The cells are narrow and tall in the posterior pole region and become flattened near the ora serrata.

3. On tangential section , the cells are hexagonal.

4. When seen in section, each cell consist of an outer non-pigmented epithelium part containing a large oval nucleus and an inner pigmented portion which extends as a series of straight thread-like process between the rods.

Functions:1. The RPE shields the retina from excess incoming light. It supplies omega-3 fatty acids and glucose.

2. Has a participation in the turnover of the outer segments of the photoreceptors, and the formation of the rhodopsin and iodopsin by storing and releasing vitamin A.

3.  It secretes substances to help build and sustain the choroid and retina.

4. The retinal pigment epithelium also serves as the limiting transport factor that maintains the retinal environment by supplying small molecules such as amino acid, ascorbic acid and D-glucose while remaining a tight barrier to choroidal blood borne substances.

Thank you!

Parts of Retinal Pigment Epithelium:

by: Aaron Jake de Leon and Charisse Visca 1. Base- adjacent to the curricular portion of Bruch’s Membrane to which its basement membrane is firmly attached. The base contains prominent infolding of the basal plasma membrane, many mitochondria, and a little or no pigment.

It contains:(Plasma membrane and mitochondria)

2. Body- contains the cell nucleus, many organelles and lipofuscin. The lipofuscin become prominent in the retinal pigment epithelium underlying the central retina in individuals older that 30 years.

It contains:

(Nucleus, endoplasmic reticulum, lipofuscin)

3. Apices-are topped with microvilli in which the outer segments of the rods and cones are imbedded in the interphotoreceptor matrix.

There are no specialized attachments between the photoreceptors and the retinal pigment epithelium.

The lateral surfaces of the apices of adjacent cells (but not the microvilli) are bound together by terminal bars that are composed of a basilar portion and an apical portion.

There is no Intracellular space at the level of these junctions, and together with the non-fenestrated retinal blood vessels they constitute the blood-retinal barrier.

Apical portion: It makes contact loosely with sensory retina through numerous Microvillus and concentrated with melanin granules.

Apex(pigmented, ingested outer segment)

It contains:

1. Microvilli2. Lateral terminal bars( Zonula Adherens and zonula occludens )

The zonula occludens (ZO) (Tight Junction) occupied very large, macular gap junctions occur within the region.

The zonula adherens (ZA) (Intermediate Junction) in adult chicken retinal pigment epithelium was examined with cryo-electron microscopic methods.

Deep-etching of the cross-fractured ZA showed globules in the intercellular space

(Age Related Macula Degeneration)

by: Kristine Nicole Ramos

Age related maculadegeneration(ARMD) mainly affects the older generation. It can affect people over 50years of age. Macula degeneration occurs when there is damage to the cells in the central area of the retina (the macula) which are responsible for seeing fine detail.

Age-related macular degeneration (AMD) occurs in 'dry' and 'wet' forms:

In ‘dry’ AMD─the most common form the light-sensitive cells in the macula slowly break down, blurring central vision in the affected eye the condition develops as the eye ages.

In the 'wet' form, abnormal blood vessel growth in the eye leads to the leaking of blood and proteins into the sensitive cells (called photoreceptors) in the macula, damaging them and causing vision loss.

The wet form is the condition in its advanced stage.

Role of RPE in ARMD:1. The RPE is responsible for maintaining the extracellular matrix and the activity of the photoreceptors. 

2. The primary cause of AMD is thought to be the degeneration of a layer of specialised cells called retinal pigment epithelium (RPE)

3. The RPE, melanin granules diminish, and lipofuscin granules form.

4. As we age, Bruch’s membrane tends to accumulate debris in the elastin lamina and also drusen between the collagen layer and RPE basal lamina. 

This debris accumulation causes a reduction in the permeability of Bruch’s membrane. 

This will hinder the pumping of waste from inside to outside of the eye by the RPE and may cause pigment epithelial detachments. 

Blood-Ocular Barrier

by: Myka Dayap1. It is a physical barrier between the local blood vessels and most parts of the eye itself, and stops many substances including drugs from traveling across it.

2. Inflammation can break down this barrier allowing drugs and large molecules to penetrate into the eye.

Blood-Retinal Barrier (BRB)

1. The blood–retinal barrier, or the BRB, is part of the blood–ocular barrier that consists of cells that are joined tightly together to prevent certain substances from entering the tissue of the retina.

2. It consists of non-fenestrated capillaries of the retinal circulation and tight-junctions between retinal epithelial cells preventing passage of large molecules from choriocapillaris  into the retina .

3. BRB Consists of Inner Blood-Retinal Barrier (IBRB) and Outer Blood-Retinal (OBRB).

Structure : The tight junctions of retinal pigment epithelium maintains the outer blood–retinal barrier.

Function :

It regulates fluids and molecular movement between the ocular vascular beds and retinal tissues and prevents leakage into the retina of macromolecules and other potentially harmful agents

 BreakdownDiabetic retinopathy

1.An eye damage that frequently occurs as a result of diabetes, is related to the breakdown of the blood–retinal barrier.

2. The barrier becomes more leaky in patients with diabetic retinopathy