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Post Info TOPIC: Corneal incisions are common


Executive

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Posts: 397
Date: Sun Apr 17 7:20 PM, 2005
Corneal incisions are common
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I think that the common misconception is that the use of corneal incisions is out dated and no longer viable. It seems that this is far from the truth as they are commonly used, for example, following PK to correct astigmatism. Although the use of laser technology is prevalent as well keratotomy is far from obsolete. The following links refer to the use of corneal incisions following PK and similar:


Radial keratotomy for residual myopia after photorefractive keratectomy.


CONCLUSION: Radial keratotomy is an effective, safe method for
treating undercorrected myopia after PRK.


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9559465&itool=iconabstr


Relaxing incision guided by videokeratography for astigmatism after keratoplasty for keratoconus.


CONCLUSION: Fewer reoperations were needed when videokeratography was used.


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?


Combined transverse and interrupted radial keratotomy for compound myopic astigmatism


CONCLUSION: Combined transverse and interrupted radial incisions are effective in correcting naturally occurring astigmatism.


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=1390407&itool=iconabstr


Arcuate transverse keratotomy remains a useful adjunct to correct astigmatism in conjunction with photorefractive keratectomy.


CONCLUSION: Arcuate transverse keratotomy performed prior to PRK for high astigmatism or after PRK for lower levels of residual astigmatism effectively improved visual outcome.


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10693620&itool=iconabstr


The question has to be asked, Why is it that these incisions are acceptable (Bearing in mind that in the case of PK the incisions are required only because after completely removing the patient cornea astigmatism is sometimes created withen the donor button) where as Prof. Lombardi's mini ark incisions are not?


It seems reverse thinking to place incisions upon an astigmatism that has been created by the very operation designed to remove the steepened refractive error. Why not use these same radial incisions BEFORE graft?


Hari



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Fil


Veteran Member

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Posts: 31
Date: Tue Apr 19 12:54 PM, 2005
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Hari,
The structure of a keratoconus cornea is different comparing to the structure of a normal cornea.
The keratoconus corneas have decreased levels of enzyme inhibitors and increased enzyme activities that can degrade the various extracellular matrices within the keratoconus corneas. The inhibitor–enzyme imbalance undoubtedly plays a major role in the stromal thinning and Bowman’s layer/basement membrane breaks that are characteristic of keratoconus corneas.
So the long term effect of incisions on keratoconus cornea is unpredictible. It's the problem...

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Executive

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Posts: 397
Date: Fri Apr 29 1:33 AM, 2005
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Hi Fil,
Unfortunatly there is a danger in all the good we are trying to do by posting extracts from medical studies here. That is that many of us are not doctors and so understand only little of what it is we are in fact posting.


Suffering from a disease such as KC does encouage us to become more schooled on the subject but at the end of the day I personally have to accept or refuse a statement on what makes logical sense, to me.
You are correct a KC cornea and a transplanted one are two very different things... but it seems that the stress and cellular disarray that goes along with corneal graft must also be taken into account. The links I posted above where all in regards to surgeons operating on corneal donor buttons that come with their own set of problems:


Specular Microscopy allows for a reasonable determination of endothelial cell density, cell pleomorphism and polymegathism, and corneal guttata. These morphological changes are indicative of the current status of the endothelium as well as its functional reserve. The endothelial layer must be intact for it to maintain its barrier properties. However, because the endothelium does not divide, cell loss (due to injury or normal cell aging) is replaced by the enlargement and migration of adjacent endothelial cells to close the breach in the monolayer. Thus, older corneas tend to have a lower cell density although this is not absolute. Cell pleomorphism and polymegathism may give additional information about the stresses and strains that have been placed on the cornea.


The above statement points out the complex evaluation that is required for donor cornea exceptance. But it also points to cell stress and enzyme change being a constant, and one that is common in all transplants... this is not nessesarily a bad thing.


But why are we asked to think that the so called 'Relaxing incisions' preformed post transplant are so much less risky than Mini ark, if we are also to believe that such incisions are a contradiction to a structurally unsound cornea? Is not a donor button by its very defintion structurally unsound? It may not have many of the inherent problems accociated with other transplants but this is still the transferance of tissue... and that is no easy task. 
What I think is missing in the assessment of Mini ark is a level playing field... that is that the same rules of assessment must be used for all.
Corneal grafts certainly have their place as an option... But the arguement in this case is that the degraded state of a KC cornea cannot stand Mini ark, How has this been evaluated? What sourse material is used to state that long term Mini ark stability is unpredictable? It is the lack of raw data that some use as a negative toward the procedure... the fact that the available information  is research and development acheived solely at the Lombardi clinic moves some to call it invalid. I think this far to narrow a view in the battle against KC, one where we have so few weapòns... We must be open to explore all options and more important still the medical powers that be must be urged to examine (In detail) these same options. It seems far too easy for those whom do not suffer KC to denounce possible avenues that with a little more understanding could possibly be an answer for so many,
Regards,


Hari



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