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Boston EyePain Foundation - a new way of looking for the causes for dry eye

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  • Boston EyePain Foundation - a new way of looking for the causes for dry eye

    Dr Perry Rosenthal , who was a founder of the Boston Foundation for Sight and instrumental in the development of the PROSE lenses and who is pretty well known on the DEZ, has recently set up a new not for profit foundation called the Boston EyePain Foundation. The website is - http://www.bostoneyepain.org/.
    This site makes very interesting and informative reading for anyone interested in dry eye – that is all of us on DEZ, I guess.

    Dr Rosenthal believes we need to look at dry eye in a completely new way – we need a paradigm shift. His ideas are certainly controversial and he knows he is fighting a battle to get them accepted but, they are well worth considering.

    The following is my own summary of his ideas. Apologies to all for any inaccuracies or misinterpretations on my part. I am not medically trained in the least, so this is a very lay interpretation.

    Dry eye is caused by problems with the corneal nerve system. This is a critical point he is making and the one where he feels the effort to cure dry eye needs to be focused. The “old way of thinking” is that dry eye is caused by a compromising of tear quality and/or quantity. This then leads to inflammation and corneal pain. Dr Rosenthal believes instead that it is a problem in the corneal nerve system that causes the body’s tear producing system to breakdown (but not in all patients.)

    It seems to me that he has come to this conclusion partly because of two classes of patients that he would consistently see and that could not be explained by the traditional dry eye model.
    1. The first are those with severe dry eyes who have no inflammation or pain.
    2. And the second are those with no dry eye signs (i.e. they have wet eyes with good tear quality) who exhibit often excruciating corneal pain.

    He believes that it is the function of the corneal nerve system to trigger the tear response in the body and, for many patients with this type of corneal nerve problem dry eye signs develop because the signalling system is not correctly telling the body to create tears.

    He thinks that there are two types of corneal nerve problem although I am not sure that these are exclusive conditions. (That is, I think a patient may often have both of these problems.)
    1. The first is hypersensitivity of the corneal nerves (or sensors) at the cornea itself. In this case the nerves react too readily to a thinning tear layer. That reaction is felt as the typical dry eye like pain most on the DEZ are familiar with. For these cases artificial tears as well as treatments to improve tear quality and quantity will have a beneficial effect as they will thicken the tear layer and so quieten the corneal nerves (i.e. reduce the pain.)
    2. The second type of corneal nerve problem is what he calls CCNP (Centralized Corneal Neuropathic Pain). This is where the nerve problem is at the brain end of the nerves. In these cases, typically, a patient will have corneal pain regardless of how wet the eye is.

    I believe this view of dry, while quite radical, bears strong consideration as it does explain a lot of the otherwise inexplicable problems of dry eye. Not only does it explain the two classes of patients that the old model does not (described above). Perhaps it also explains the problem nearly all on DEZ seem to have – that the traditional dry eye treatments do not produce the promised relief.

    A last thing I wanted to say that may make Dr Rosenthal’s theory seem harder to accept (but it is a theory I like) is his evolutionary explanation as to how the eyes’ nervous and tear systems have developed. I think that the traditional thinking (certainly it was my thinking) was that tears serve to protect the eye and that corneal nerves are designed to trigger off a reaction when the tear protection is compromised. Perhaps this is where the real paradigm shift comes in. Dr Rosenthal ponders that the function of the tear system is to produce good quality tears as an aid to vision. That is, tears are the final lens of the eye and tears are needed for clear vision, not for protection. So the corneal nerve system is designed to fire off impulses to the brain not because the cornea is unprotected when the eye becomes dry, but because it is trying to stop vision becoming compromised. Without this, he thinks, when we first crawled upon the land our existence as a species would have been threatened. We would not have spotted that hungry Sabre Tooth Tiger.

    Again I apologise for any misrepresentations in the above explanation. Here is a link to a page on Dr Rosenthal’s site where he explains in detail his ideas - http://www.bostoneyepain.org/does-th...el-hold-water/. This is meant for doctors to read but I feel it is worth taking the time to go though (with the help of Google for some of the terms).
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