thinnest corneal ever have..

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thinnest corneal ever have..

Postby alohadaniel » Sat May 12, 2007 12:48 pm

hi everyone. 2 qns:
1. My particulars:
Left: -8.50 -0.75 180 6/6
Right: -10.50 -0.75 180 6/6
Central Pachymetry: L 480 R 460

poor me...
Anyone could tell me what's the meaning of 6/6 and 180?
The doctor told me I m not suitable for LASIK definitely right now. I was quite dissapointed and forgot to ask is there any other surgery could save me? LASEK? PRK?

I heard of some websites say that LASEK is suitable for those with thin corneas and high degree of myopia. Any advise? what is the safe thickness of corneas considered during LASIK. 400um?

2. I never used contact lenses for the most recent 1 yr. Now I m thinking about having contact lenses since there is nearly no hope for me to get my eyes better by surgery. I ve used contact lenses for nearly 2yrs when i was so young(now I am 20). Is there any possiblility that the corneas was getting thiner and thiner during that period because of the not so healthy use of contact lenses? Do contact lenses really hurt corneas so heavily? Can I still use contacts on my vulnerable eyes.? Are corneas going to become thinner after that? I m worried.
alohadaniel
 
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Location: singapore

Re: thinnest corneal ever have..

Postby LasikExpert » Sat May 12, 2007 5:42 pm

alohadaniel wrote:Anyone could tell me what's the meaning of 6/6 and 180?


The 180 is the direction of your astigmatism with 0 degree at the left and 180 degree at the right when facing your eyes. See prescription.

If you are outside of the United States, the 6/6 would mean that with this correction you see an object 6 meters away from you with the clarity a normally sighted person would see an object 6 meters away. 6/6 is the same as 20/20. 20/20 is 20 feet with clarity of 20 feet.

alohadaniel wrote:The doctor told me I m not suitable for LASIK definitely right now.


This is correct.

alohadaniel wrote:I was quite dissapointed and forgot to ask is there any other surgery could save me? LASEK? PRK?


Let's do some basic math. Every diopter of correction over a 6.0mm conventional ablation treatment zone will remove 12 microns of tissue. Your worst eye would require about 125 microns of tissue removal.

A minimum of 250 microns of cornea must remain untouched to maintain stability in a healthy cornea.

Even the thinnest possible Lasik flap created with a femtosecond laser would be 100 microns thick.

So, your right eye is 460 microns thick, subtract the 100 microns for a flap, subtract 125 microns of tissue removed, and you have 235 microns remaining. Your cornea would be unstable.

A surface abltion technique would eliminate the Lasik flap and you would have 335 microns of cornea remaining. That is within the recommended minimum.

With such high refractive error, it is highly likely you will regress and require enhancement surgery. Regression of no more than 2.00 diopters would be a reasonable expectation. That is another 24 microns of lost tissue.

If you require a larger treatment zone than the 6.0mm we have used in our example, then the amount of tissue per diopter of correction goes up exponentially. A 6.5mm optical treatment zone would require about 18 microns of tissue per diopter of change. Now you would have 155 microns untouched with Lasik and 255 microns with a surface ablation like PRK, LASEK, or Epi-Lasik...plus another 30 or so for enhancement. You would not be able to have a larger ablation zone and this may be important due to Lasik and night vision problems.

If you elect to have wavefront-guided ablation rather than conventional ablation, more tissue would be removed.

It is clear that Lasik is out. A surface ablation technique like PRK, LASEK, or Epi-Lasik may be possible, but you are really thinning an already thin cornea and this may not be wise.

alohadaniel wrote:Now I m thinking about having contact lenses since there is nearly no hope for me to get my eyes better by surgery.


This is a reasonable and wise alternative. The technology of newer contact lenses is improved over the previous models.

alohadaniel wrote:...now I am 20


Your age actually brings up an issue about your corneal thickness. You should be carefully checked for a corneal disease called keratoconus. This causes weakening and thinning of the cornea and normally presents before the fourth decade of life. Keratoconus tends to run in families, so if any of your family has it or required corneal transplants, you may be at elevated risk. Keratoconus with thin corneas would be a contraindication for Lasik and even PRK, LASEK, or Epi-Lasik.

alohadaniel wrote:Is there any possiblility that the corneas was getting thiner and thiner during that period because of the not so healthy use of contact lenses?


Don't misuse your contacts and the probability of contact lens induced corneal thinning is low in a healthy cornea. Discuss the specifics with your doctor.
Glenn Hagele
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USAEyes

Lasik Info &
Lasik Doctor Certification

I am not a doctor.
LasikExpert
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Re: thinnest corneal ever have..

Postby alohadaniel » Sun May 13, 2007 4:13 am

LasikExpert wrote:
alohadaniel wrote:Anyone could tell me what's the meaning of 6/6 and 180?


The 180 is the direction of your astigmatism with 0 degree at the left and 180 degree at the right when facing your eyes. See prescription.

If you are outside of the United States, the 6/6 would mean that with this correction you see an object 6 meters away from you with the clarity a normally sighted person would see an object 6 meters away. 6/6 is the same as 20/20. 20/20 is 20 feet with clarity of 20 feet.

alohadaniel wrote:The doctor told me I m not suitable for LASIK definitely right now.




This is correct.

alohadaniel wrote:I was quite dissapointed and forgot to ask is there any other surgery could save me? LASEK? PRK?


Let's do some basic math. Every diopter of correction over a 6.0mm conventional ablation treatment zone will remove 12 microns of tissue. Your worst eye would require about 125 microns of tissue removal.

A minimum of 250 microns of cornea must remain untouched to maintain stability in a healthy cornea.

Even the thinnest possible Lasik flap created with a femtosecond laser would be 100 microns thick.

So, your right eye is 460 microns thick, subtract the 100 microns for a flap, subtract 125 microns of tissue removed, and you have 235 microns remaining. Your cornea would be unstable.

A surface abltion technique would eliminate the Lasik flap and you would have 335 microns of cornea remaining. That is within the recommended minimum.

With such high refractive error, it is highly likely you will regress and require enhancement surgery. Regression of no more than 2.00 diopters would be a reasonable expectation. That is another 24 microns of lost tissue.

If you require a larger treatment zone than the 6.0mm we have used in our example, then the amount of tissue per diopter of correction goes up exponentially. A 6.5mm optical treatment zone would require about 18 microns of tissue per diopter of change. Now you would have 155 microns untouched with Lasik and 255 microns with a surface ablation like PRK, LASEK, or Epi-Lasik...plus another 30 or so for enhancement. You would not be able to have a larger ablation zone and this may be important due to Lasik and night vision problems.

If you elect to have wavefront-guided ablation rather than conventional ablation, more tissue would be removed.

It is clear that Lasik is out. A surface ablation technique like PRK, LASEK, or Epi-Lasik may be possible, but you are really thinning an already thin cornea and this may not be wise.

alohadaniel wrote:Now I m thinking about having contact lenses since there is nearly no hope for me to get my eyes better by surgery.


This is a reasonable and wise alternative. The technology of newer contact lenses is improved over the previous models.

alohadaniel wrote:...now I am 20


Your age actually brings up an issue about your corneal thickness. You should be carefully checked for a corneal disease called keratoconus. This causes weakening and thinning of the cornea and normally presents before the fourth decade of life. Keratoconus tends to run in families, so if any of your family has it or required corneal transplants, you may be at elevated risk. Keratoconus with thin corneas would be a contraindication for Lasik and even PRK, LASEK, or Epi-Lasik.

alohadaniel wrote:Is there any possiblility that the corneas was getting thiner and thiner during that period because of the not so healthy use of contact lenses?


Don't misuse your contacts and the probability of contact lens induced corneal thinning is low in a healthy cornea. Discuss the specifics with your doctor.


Thanks for your reply.
According to your statement. Does that mean there is no suitable surgery for me currently? Do I necessarily need to wait for the new technology to come out?

I ve checked my eyes every year and the doctor used to tell me my eyes were healthy though he did not check the thickness of corneas. Is that enough to say I have no corneal disease? The doctor always said: pure high prescription.

My corneal thickness is so small:480/460. Based on your experiences, is it natural to be so small or because of other reasons like contact lenses. My father had high prescription also but he did PRK about 9yrs ago. Now it is quite ok for him but a little regression. He does not has any corneal diseases. My mother got extremely good eyes.

Do u mean that if I use contact lenses correctly, carefully. It does not hurt corneas, even my prescription is so high, right?
alohadaniel
 
Posts: 6
Joined: Wed Mar 21, 2007 2:57 pm
Location: singapore

Re: thinnest corneal ever have..

Postby LasikExpert » Sun May 13, 2007 5:37 am

alohadaniel wrote:Does that mean there is no suitable surgery for me currently? Do I necessarily need to wait for the new technology to come out?


It may be possible to have PRK, LASEK, or Epi-Lasik, but exact calculations need to be taken and even if it is possible, it may not be wise.

alohadaniel wrote:I ve checked my eyes every year and the doctor used to tell me my eyes were healthy though he did not check the thickness of corneas. Is that enough to say I have no corneal disease?


I recommend that you seek an comprehensive medical eye exam from an ophthalmologist. With such high myopia and thin corneas, you should be checked every few years for the health of your eyes. Your everyday eye doctor (optometrist) is able to do much, but is limited in expertise and ability.

alohadaniel wrote:My corneal thickness is so small:480/460.


This is thinner than normal.

alohadaniel wrote:Do u mean that if I use contact lenses correctly, carefully. It does not hurt corneas, even my prescription is so high, right?


Yes.
Glenn Hagele
Volunteer Executive Director
USAEyes

Lasik Info &
Lasik Doctor Certification

I am not a doctor.
LasikExpert
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Joined: Fri May 12, 2006 6:43 am
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