| FORUM Associazione A.M.C. http://www.associazionecheratocono.it/forum/ |
|
| "Giorni buoni e giorni cattivi" per i portatori di http://www.associazionecheratocono.it/forum/viewtopic.php?f=4&t=74 |
Pagina 1 di 1 |
| Autore: | scaistar [ martedì 22 febbraio 2005, 13:11 ] |
| Oggetto del messaggio: | "Giorni buoni e giorni cattivi" per i portatori di |
Ho trovato questo articolo in cui un Dottore di Jerusalem spiega come mai alcuni portatori di LAC si trovano bene per alcuni giorni e poi male per altri. Good Eye Days -- Bad Eye Days (GED/BED) by Bezalel Schendowich, OD, FIACLE A common complaint of contact lens wears and especially those with keratoconus is that they can fairly well wear their contact lenses for several days running and then run up against several days during which they can't manage even to insert the little beasts. Some patients have termed this situation Good Eye Days/ Bad Eye Days (GED/BED). I would like to offer a possible explanation of this phenomenon; a rationale why GED/BED is likely to be more prevalent amongst the KC contact lens wearing population than amongst those with non-conical corneas; and hopefully a possible prevention-cure. Causes Of the many possible causes of GED/BED, I think the most likely is simply overwearing contact lenses. While many people can wear lenses for many consecutive hours day after day with no readily apparent insult, there exists a particular corneal structure which tires of bearing the contact lens-foreign body at some stage. We first became aware of the 'overwear syndrome' (OWS) many years ago with hard (not gas permeable -- RGP) contact lenses. After too many hours eyes begin to redden, tear and generally reject the lenses; the morning after is even worse. Many cases of OWS have been at least partially remedied with contact lenses made from RGP materials, but some corneas still can not handle the stress of long term wear. I think that in KC we have to consider two additional factors besides the 'foreign body under the lid' aspect: the predisposition of the conical cornea to react pathologically to stresses on (1) the molecular level and (2) the cellular level. A series of recent laboratory studies summarized by Dr. M. Cristina Kenney when she presented the Everett Kinsey Lecture last year to the Contact Lens Association of Ophthalmologists and since reprinted in the Spring '99 issue of the NKCF Newsletter and on their website can help us understand the weakness and susceptibility of the KC cornea to react badly to physical stress. While the paper ought to be read in full, I will use some of the results here. 1. Molecularly, several biochemical compounds (amino acids, proteins, enzymes) have been identified in significantly different concentrations in normal corneal cells as opposed to their concentrations in keratoconic cells. Some compounds are more frequently found in keratoconus cells and others which exist in normal corneas are in some cases non-existent in KC. The purposes of these chemicals of course varies. In normal corneas the compounds which are missing in KC aid the cornea in proper healing after injury, in new cell growth and development, and in maintaining the structural uniformity and transparency of the cornea. Those that are found in KC but not in normals have been shown to weaken the cornea's response to UV-light and other external stresses. 2. Research has shown that on the cellular level, KC cells will capitulate and self-destruct (apoptosis) when threatened or injured. Other work has shown that areas of these cells will more likely heal from injury and abrasion abnormally. This compromised healing response results in scars and thinner tissue than would a healthy cornea. Now back to GED/BED. We know that KC'ers, like most of the visually unchallenged world, enjoy seeing; and because, seeing is optimized for them by wearing contact lenses (in most cases), will tend to wear their lenses to the maximum. Sometimes they overrun the maximum, physiologically safe, wearing time for their eyes and their lenses. That would have been a Good Eye Day. Many KC'ers can wear their lenses for many successive GED's before they suddenly encounter a BED. And then, 'all H--- breaks loose'. "Why can't I wear my contact lenses?" cries the hapless voice over the phone. On examination and questioning the careful clinician can discover that his patient has probably been pushing his lens wear to the limit. He is now in the throes of what may be considered to be a complicated OWS with exaggerated responses dictated by his compromised KC cornea. So, from these thoughts it seems that when the wearing is good, we have GED; and after the wearing has been very, very good, it can be followed by the BED. It also seems that because of the peculiar biochemistry of the cells of the KC cornea this is more likely to happen to KC'ers than non-KC'ers. I would like to propose that however so much a KC'er needs (and I imply with that word a 'need' greater than most of us can comprehend) to wear his lenses in order to function, he will do far better in the long run by limiting his continuous wearing time. Continuous wearing time (CWT) is one of my favorite functions of contact lens wear. At each follow-up visit I try to ask every patient how long he has worn his lenses so far today and yesterday and the day before. This helps me to understand more clearly the intricacies of contact lens adaptation. I explain to my patient-in-the-chair that when he removed his lenses for his afternoon nap he essentially divided his wearing day into distinct units. I, then, ask again how long he wears his lenses continuously (I also remind him to thoroughly clean his lenses on each removal). Treatment While KC patients have to read, write, work, and compete like the rest of us in order to survive and they have to cook, clean, drive, plow, and so on as part of their every day lives; and while they must be able to see efficiently to perform these functions, it must not be at the expense of either their immediate eye health or their capacity to wear their contact lenses on the following day. A common sense approach to CWT for these patients maintains a balance between necessary binocular wear, incidental alternating monocular wear, and around the house spectacle wear (for those who can -- and most can manage something around the house with glasses). We must use our judgment as professionals to help our patients find the most efficacious way of avoiding the pitfalls of GED/BED. ------------------------------ Bezalel Schendowich, OD, FIACLE |
|
| Pagina 1 di 1 | Tutti gli orari sono UTC + 1 ora [ ora legale ] |
| Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group http://www.phpbb.com/ |
|