Eye Poop Reduction

Looking for information on therapies that slow the vision cycle. Got all sorts of things on slowing traffic for safer cycling.

While I am all for fewer car/bicycle accidents, that is not exactly what I had in mind!

Back to Wikipedia, I discovered the visual cycle is the process through which light is transformed into electrical signals. If you have a penchant for chemistry, I refer you to the Wikipedia article. Social scientist here! As far as I am concerned…then there is magic!

Part of this magic includes having three different types of cone cells that respond to three, different wavelengths of light. By taking stock of the strength and blending of the stimuli from these three, types of cone cells, we are able to see color! Cool! Although my guess would have been the primary colors, the colors they detect are actually red, blue and green. Why? Dunno. Magic.

But back on track, visual cycle…

Since the job of RPEs is not only to feed the photoreceptors but also to clean up after them, RPEs have to be able to tolerate a lot of…uh, poop. (Gee, maybe I am just a big RPE! I feel like I deal with that stuff all the time!) When there is too much poop for them to handle, we get, among other problems, drusen.

Janet Sparrow in Therapy for Macular Degeneration: Insight from Acne (catchy title?) said “it is the responsibility of the RPE to internalize the membranous debris discharged daily by the photoreceptor cell.” In other words, they eat eye poop. Unfortunately, some of the molecules in the poop are toxic (as if eating eye poop was not bad enough) and not at all good for the RPEs or surrounding cells.

The theory goes something like this: Less eye poop would make life easier for the RPEs. While we cannot get rid of all the eye poop – after all it is a byproduct of what we want: sight – maybe we can reduce the volume of how much poop we actually have to deal with. If we slow down the chemical processes involved in sight maybe we can produce less poop and thus see for a longer period of time.

They are checking out that theory right now. Foundation Fighting Blindness (FFB) advertised for subjects for a phase 2 (proof of concept) clinical trial of ACU-4429, a “visual cycle modulator”. For our purposes, read “eye poop reduction strategy”.

FFB also published a one page blurb about Fenretinide. Fenretinide has successfully completed phase 2 clinical trials and is on the way to phase 3. They are hopeful it will slow down the visual cycle in those with dry AMD. The slowing should lead to fewer lesions in dry AMD and fewer cases of wet AMD.

Oh, and that chemistry I referred to earlier? I might actually have to understand some of it. Oy. In the visual cycle there is a pigment-y sort of thing called 11-cis. Helping the light signal along its way to become sight causes a chemical change in the 11-cis. In order to get changed back to its original form so it can do its job again and not contribute to the eye poop problem, 11-cis needs help from several molecules, one of which is REP65. REP65. Remember that name. It may be an up-and comer.

written October 14th, 2017

Next: coming soon!

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