Regeneration strat: Age-related macular degeneration Flashcards
What is AMD?
A medical condition which may result in blurred or no vision in the center of the visual field
- Due to the loss of the retinal epithelial cells, which normally provides nourishment to the rods and cones
What are the affects of AMD on vision?
- Slow recovery of visual function after exposure to bright light
- Visual activity drastically decreasing
- Blurred vision
- Trouble discerning colours
(Loss in contrast sensitivity)
What is wet AMD characterised by?
- The growth of new blood vessels within the retinal tissue and subsequent haemorrahging from them
- Drusen speads over large parts of the eye
What is dry AMD?
-Little of no haemorrhaging
What are the early signs of both AMD types?
Drusen
- Fatty deposits on the retina
- Extracellular material builds up between Bruch’s membrane and the retinal pigment epithelium of the eye
What are the rods of the eye?
Photoreceptors for low light vision
What are the cones of the eye?
Photoreceptors for colour vision
What is the macula of the eye?
- Functional centre of the retina
- Gives the best colour vision
What is the foeva of the eye?
- Closely packed cones
- Accurate vision
- Centre of the macula
What happens during the progression of AMD?
1) Retinal pigment epithelium (RPE) cells towards the rear of the retina malfunction and die
2) Photoreceptors adjacent to the RPE die (can’t be properly supported)
3) Choroid layer containing blood vessels develops abnormal structure and physically displaces overlying neural retina
What are 6 functions of the RPE?
1) Regeneration of bleached opsins
2) Phagocytosis of photoreceptor membranes
3) Transepithelial transport
4) Secretion of growth factors essential for the retina
5) Absorption of light
6) Protection against photo-oxidation
Can cell transplantation cure AMD?
What type of transplantation was used first?
Yes, possibly
- Restores sight
- Autologous (cells obtained from the same individual)
Disadvantages of autologous transplantation to cure AMD?
1) Restoration of central vision is at expense of an area of peripheral vision
2) Lengthy and challenging operation
3) Follow up surgical procedure to remove compression medium
Can cultured RPE cell be grown to treat AMD?
Probably
- In vitro produced human RPE maintains sight when transplanted in RCS raat
If cultured RPE cells work, what is the problem?
- Donor material hard to come by
- RPE cells show a limited capacity to proliferate in vitro
- RPE phenotype tends to degenerate with time in culture
- Karyotypically abnormal
- Similarity to normal RPE is questionable