What is the Retinal Pigment Epithelium?
The retinal pigment epithelium is a fundamental component of the retina that plays an important role in vision. The retinal pigment epithelium (RPE) is made of a single layer of regular polygonal cells arranged at the outermost layer of the retina. The outer side of the RPE is connected to Bruch’s membrane and the choroid, while the inner side is connected to the outer segment of photoreceptor cells. RPE structures are essential to normal vision, and alterations in the RPE can impair function and cause retinopathy.
- The retinal pigment epithelium (RPE) is a key component of the retina that plays a role in vision.
- Alterations in the RPE impair retinal function and lead to retinopathy
- Age-related macular degeneration, retinitis pigmentosa and Stargardt’s are retinal conditions caused by RPE dysfunction.
Understanding Retinal Pigment Epithelium
The RPE has a number of functions. First, it is responsible for maintaining visual function and the visual cycle. RPE cells are phagocytic. They engulf and eliminate exfoliated photoreceptor outer segments (POS) and maintain the normal renewal of visual cells. Secondly, it prevents light damage due to the pigment particles like melanin and lipofuscin. Lastly, RPE barrier cells guard both the inside and outside of the retina and strictly control substance entry and exit.
Conditions Caused by Disorders of the Retinal Pigment Epithelium
Age-related macular degeneration (ARMD), Retinitis Pigmentosa and Stargardt’s disease are three ocular conditions in which RPE dysfunction plays a role.
Age-Related Macular Degeneration
Age-related macular degeneration (ARMD) is the progressive degeneration of the photoreceptors and underlying RPE cells in the macula region of the retina. It is the leading cause of vision loss in the elderly. Though our understanding of ARMD has increased over the years, the underlying disease mechanism has not yet been identified. The disease is thought to be due to a combination of environmental and genetic factors.
Retinitis pigmentosa (RP) is a hereditary disorder of the photoreceptors and the RPE which gradually leads to night blindness and progressive constriction of the visual field. The pigmentary changes seen in RP are characteristic of bone spicules, like pigment clumping which is due to photoreceptor degeneration, atrophy in the outer retina and pigment epithelium, and RPE cells migrating into the retina.
Stargardt disease is the most common form of juvenile macular degeneration and is characterized by a progressive loss of central vision, with an onset of symptoms during the teenage years. Stargardt disease results in a rapid accumulation of lipofuscin in the RPE cells, leading to RPE and photoreceptor cell degeneration.
Diagnosing Conditions of the Retinal Pigment Epithelium
A diagnosis for a condition of the RPE will be made during a dilated, comprehensive eye exam. It may be confirmed, managed, and/or treated using optical coherence tomography (OCT), which is a non-invasive imaging test that uses light waves to take cross-section pictures of the retina.
Treatment of the Retinal Pigment Epithelium
Treatment depends on the condition caused by the RPE disorder.