what is age related macro degeneration?
blurred vision in the centre of the visual field and loss of colour
what are the 4 main affects of AMD?
- Slow recovery of visual function after exposure to bright light
- Trouble discerning colours - a loss in contrast sensitivity
- Visual acuity decreases
- blurred vision
what are the 2 forms of AMD?
1) Wet – new blood vessels grown within diseased retinal tissue and leak and damage the retina
2) Dry – degeneration occurring in the retina - little or no haemorrhaging
what are early predictive signs of both types of AMD?
- Common characteristic of both is fatty deposits on the retina (drusen)
- Builds up between bruch’s membrane and retinal pigment epithelium of the eye
what are the rods and cones for in the eye?
rods = photoreceptor for low light cones = photoreceptor respsonsible for colour vision
what is the macular?
functional centre of the retina – gives 20/20 vision – best colour vision
what is the fovea?
an area of closely packed cones for accurate vision
what is found in the choroid?
all the blood vessels
what happens during progression of AMD?
- retinal pigment epithelium cells toward the rear of the retina malfunction and die
- rods and cones adjacent to the RPE cells die
- choroid layer develops abnormal structure and physically displaces overlying neural retina
why are RPE cells important?
they are needed for eyes to function correctly so the consequences of them being destroyed is significant
6 functions of RPE cells?
1) regeneration of bleached opsins
2) phagocytosis of damaged photoreceptor membranes
3) transepithelial transport of important nutrients
4) secretion of growth factors essential for the retina
5) absorption of light
6) protection against photo-oxidation
which type of AMD account for 90% of cases and is currently incurable?
the dry variant
what are the 3 problems with restoration of RPE cells through cell transplantation?
- Restoration of central vision is at the expense of an area of peripheral vision
- Lengthy and technically challenging operation to do - must remove RPE layer and implant RPE at disease site
- Follow up procedure is required to remove compression medium (oil drop)
a possible solution is using RPE cells from donor material however what are the problems with this?
- hard to come by
- RPE cells show a limited capacity to proliferate in vitro
- RPE phenotype tends to degenerate with time in culture
could use ES cells grown in vitro but what is a problem?
delivery of the cells
- patients are typically elderly with an aged bruchs membrane
- cells may fail to attach to the bruchs membrane
what is a solution to cell suspensions failing to attach to the bruchs membrane?
could manufacture an artificial membrane by engineering a patch and attaching the undamaged RPE cells to it
is the cell coated patch effective in preliminary tests?
yes it is - clinical trials now underway to test safety and soon efficacy
describe the cross section of macular?
choroid - bruchs membrane - retinal pigment epithelium - cone cells - light
