Tuesday, March 9, 2010

Introduction into this myope's life plus PRK candidacy.

Ive wanted to "fix" my eyes ever since I got my first pair of glasses at age 12. 
I remember asking for laser eye surgery in my teens and my dad said I was too young. I asked again in my early 20s and begin researching RK(obsolete), lasik, PRK, Intacs, IOLs, etc. I posted on different forums about lasik and was told that lasik damages every eye and those people warning me away from lasik had gotten lasik without being fully informed of the risks and they wish they could go back to glasses. They pointed out a list of over 100 different things that can go wrong with lasik. They also said that lasik increases high order aberrations, gives worse vision than glasses(especially at night and in dim light), creates a flap that never heals, causes dry eyes, puts you at risk for ectasia, etc. In short, they scared me away from lasik.

When I mentioned PRK, they said it also damages your eyes, but they admit it's the "lesser of the evils" compared to lasik. I asked about IOLs and they said that's for those who wish to remove their cataracts. I researched IOLs and they are also being done for extreme myopes who aren't good candidates for lasik/PRK. Some say that IOLs are actually *more* risky than lasik, so it's rarely done if you are a good candidate for lasik/PRK. I do know that getting IOLs also means youll never have to worry about cataracts in the future. It robs you of all accomodation so they are best for those 40+

I also researched Intacs and again, was told even Intacs have their risks and could damage your eyes and that they were meant for keratoconus and ectasia. They said my choice was glasses or contact lenses(low risk) and there was nothing else I should even consider. I had tried contacts about 20 times but they were never comfortable  for more than a few minutes. I could constantly feel them and they made my eyes dry and achy. An optometrist said I had oily tears and wasn't surprised I could never tolerate contacts.

Intacs are based on contact lense technology and from my research, they have the least risks and most benefits. The biggest advantage is that Intacs can be removed and the effects will revert back to pre-op levels. Unlike PRK, I can get Intacs in one eye first and if for any reason it doesn't work out, I can have it removed and go back to glasses without aniseikonia. Saving all my cornea leaves the options open for future technology that replaces lasik/prk.

My left eye is -5, my right eye is -4.5 and I see 20/30 with glasses. Intacs will reduce my myopia and hence reduce my dependency on glasses without needing reading glasses. I will only need glasses for distance. I spend many hours a day on the computer and won't need glasses for this after Intacs. I am surprised Intacs isn't marketed more, many people are low to moderate myopes and could benefit from Intacs with less risks than lasik and even PRK. They would have the safety net of Intacs being removable among other advantages.

I learned about stuff such as:

Though less well known, these small implants can improve vision in patients with mild to moderate myopia without the risk of permanent eye damage inherent in the tissue removal technique of LASIK. Intacs are semi-circular disks implanted in the cornea which stretch it to assume a flatter shape. Though slightly less precise than LASIK, they are removeable and replaceable, so if the patient has an unexpected over- or under-correction, the implant can be removed and another of a different size inserted to obtain the desired correction. The implants are located at the edge of the cornea, so the central visual area is completely intact and undamaged, and the strength of the cornea is undiminished, making it a better option for pilots and those who engage in contact sports where eye injury is a possibility.

Intacs are unsuitable for severe myopia and more than minor astigmatism (1.00 diopters), as the cornea can only be stretched so far. If the Intacs are removed, vision returns to its preoperative level. Aside from vision correction, Intacs are also used to treat keratoconus. Intacs are FDA approved and 10 year studies have revealed no major problems with Intacs and very few patient complaints; however, because the procedure takes more training than LASIK, there are fewer eye surgery clinics offering it. However, the Intacs website gives a list of practitioners in each state, as well a few in Canada, Europe and Mexico.

Intacs pros over PRK

1. No cornea removed, keep all 550 microns
2. Center of cornea untouched
3. Very remote chance of overcorrection(for me)
4. Maintain prolate cornea(Allegretto can do that too)
5. Intacs can be removed, keeps future options open
6. 3x faster healing time and less pain
7. Bandage contact lens for only a day
8. Faster surgery than lasik/prk
9. 60% chance of improving BCVA(for keratoconus?)
10. No risk of ectasia, makes cornea stronger
11. Can get in one eye at a time
12. Less risk of dry eyes
13. Consistant correction, litle variation

PRK pros over Intacs

1. Avoid 35mm HG vacuum for 8 seconds
2. No foreign object in eyes
3. Can correct me to -1 instead of -2
4. $2000 cheaper(hardly matters)
5. Avoid migration complication of Intacs

On another note, if I do decide on PRK, it will be with the Allegretto wavefront guided with an 8mm prolate(not oblate!) zone to match my 8mm pupils. Wavefront-guided PRK is based on aberrometry measurements and is designed to treat both spherocylinder and higher order aberrations. I don't expect a reduction in my HOAs unless they were high to begin with, ill be getting tested for this. I do suspect I have plenty of HOAs and irregular astigmatism since my left eye corrects to 20/25-20/30 and my right eye corrects 20/40. I mentioned this 5 years ago on this forum. Ive learned alot since then but still have more to learn. It's good to be informed of all the risks.

I read that results demonstrated similar wavefront outcomes in both groups in eyes with less than 0.3 microns of pre-operative higher-order aberrations (HOAs), accounting for 83 percent of eyes. Eyes with 0.3 to 0.4 microns of pre-operative HOAs demonstrated slightly more improvement with wavefront-guided treatments than with Wavefront Optimized treatments. In cases with more than 0.4 microns of HOA, it was discovered that post-operative HOAs were reduced significantly in the wavefront-guided cohort. No symptomatic increases in aberrations were observed in either cohort. Also, the Allegretto Wave is the only standard LASIK platform that has demonstrated the ability to preserve and improve low contrast acuity.

One website claims: My 20/15 rate is about 99% in these cases."

Is this 20/15 with glasses? No way UCVA, most can't even get to 20/20 as ive learned. Besides ill be happy to just be 20/20 with glasses and surprised if I get 20/15 with glasses. How do more than very few people see such tiny letters, especially when glasses minify them even further? It would be a limitation of the retina and cone density. Well that limit may actually be 20/8 but with zero HOAs which is impossible, especially after lasik/prk. Note that I am skeptical of all exaggerated claims regarding "perfect vision" and "rare complications"

I did get a lasik consultation back in 2003 but of course did more research and decided lasik was too risky. Ive been interested in Intacs back then and still am. Because Intacs are so rarely done on myopia and very few centers even offer Intacs(mainly for keratoconus) I have been looking at PRK(not lasik) and the Allegretto is the newest, best laser in America. Nothing is risk free, I am just considering my options with the least amount of risk.

Option 1:

Reduce the -5.25 in left eye to -3.25 by setting the laser for 2d of correction. I am allowing a 1d margin because the healing response among many other factors dictate this. Thus ill end at -2.25 to -4.25 but there's a small chance I can end outside this range. Still, an overcorrection is very unlikley to occur. Allowing 3+ months for left eye to heal, then reduce the right eye from -4.75 to -3.25 by setting the laser for 1.5d of correction as well as correcting my irregular astigmatism at the same time. Allow 3+ months for right eye to heal, repeat left eye with a target of -1.5d(-0.5d to -2.5d range) post prk refraction. Allow 3+ months to heal and repeat right eye to closely match whatever left eye ultimately ends up at. Retaining -1.5d of myopia(give or take) will save some cornea, greatly reduce the risk of overcorrection and greatly reduce(not eliminate, that's impossible) my dependancy on both distance and reading glasses and allow me to use the computer with no glasses!

Should I end up better than 20/20 BCVA for some strange reason, I won't be getting an enhancement and will be happy to live with around -3d of myopia and enjoy the super sharp BCVA as well as reduced dependancy on glasses and never need reading glasses.

Should the first go of PRK on the left eye get me to -2.5 or better, an "overcorrection" to be technical, I won't repeat the left eye and just do the right eye to closely match the left eye. Ill be happy I didn't go for plano as I would have ended up significantly overcorrected for real. This would mean reading glasses or bifocals for me.

Should the results be dissatisfactory on the left eye regarding dryness, night vision, unusual outcome, complications, I won't touch the right eye. Because the difference between -3.25(therebouts) and -4.75 will be fairly close, this will minimize the aniseikonia and ill be able to go back to glasses and wait 5-10 years for better laser technology.

I would have to decide what action to take for other possible outcomes once they happen.

Option 2: Reduce the -5.25 in left eye to -3.25 by setting the laser for 2d of correction. I am allowing a 1d margin because the healing response among many other factors dictate this. Thus ill end at -2.25 to -4.25 but there's a small chance I can end outside this range. Still, an overcorrection is very unlikley to occur. Allowing 3+ months for left eye to heal, then reduce the right eye from -4.75 to -1.5(therebouts) with as little astigmatism as possible. Wait then do a second round on the left eye to closely match right eye. Will likley end up somewhere between -0.5 and -2.5 which is allowing a 1d margin from the -1.5d target. This range is acceptable in reducing my dependancy on glasses while keeping a low amount of myopia to preserve some near vision.

As to the possible outcomes that should happen, see above.

Option 3: Get both eyes done with a target of -1.5, range of -0.5 to -2.5. This is more risky for several reasons. Although it means no enhancements, there's a small chance of an overcorrection because I have no idea on the healing response. Ill be removing around 100 microns of cornea(27 per diopter for 8mm prolate zone?) so this puts me at increased risk of haze(even with MMC?) vs. removing around 50 microns each go and spreading it over 2 treatments, allowing a full healing each time. Ill be risking both eyes at once instead of one. Ill also lose the advantage of seeing thru the other eye when the treated eye is healing and vision may be slightly blurry.

Monovision is not for me, I do not want anisometropia nor risk overcorrecting the dormant distance eye, seen it happen all the time. I can't and won't aim for plano in either or both eyes for the reasons I mentioned, it's too risky and pointless to waste cornea just to trade for reading glasses. I use my eyes for near more than distance and am wearing computer glasses that correct 3.5d of my 5d of myopia. It is not realistic to expect an elimination of glasses for everything, you can choose distance, intermediate or near and wear glasses part time.

Choosing distance is the most risky because an overcorrection will result in bifocals. You can't add cornea back. Choosing intermediate to the tune of -1.5d gives me a safety margin. An "overcorrection" will likley mean ill be -0.5d instead of hyperopic. An undercorrection will mean ill be -3d and can either leave well enough alone or enhance that to around -1.5d. Choosing near is great for high myopes who just don't have enough cornea for any other choice anyway unless they want to risk IOLs. It's great to be around -2.5d instead of the -6, -7, -8(therebouts) that they are. If they don't find -2.5d acceptable and they don't want to risk IOLs, it's perfectly acceptable for them to stick with glasses like this -9d friend I know.

Thanks for reading. I am still doing research and have realistic expectations of a reduced dependancy on glasses, reducing my refractive error and understanding the risks.


1. How much cornea is removed for an 8mm optical zone? Where can I find the math?
2. I read that the cornea can't be flatter than 35d or the quality of vision goes way down. Is the flattening based on how much cornea is removed regardless of optical zone size or by how many diopters you correct?
3. Is it true the more cornea you remove, the more surface nerves that control tears get damaged? I notice lasik causes way more dry eyes than PRK, is this because the flap damages an extra 150 microns of cornea?
4. Why don't more people consider the Allegretto for PRK and to keep their corneas prolate? It's less risky and causes less damage than oblate lasik.
5. Why don't more people research something as serious as laser surgery as carefully and as long as me?
6. What kind of tests other than measuring my pupils(8mm?), dry eyes, cornea thickness(550 microns) HOAs, cornea topography should I ask for?

On March 25, I went to get a PRK consultation. I got several tests and asked more questions than anyone else. The optometrist says I probably know more about some aspects of vision than he does! First I was tested on the autorefractor which thinks im a -7 I told her it overcorrected me and she says that's common. Next I got topographies of my cornea. I knew I had irregular astigmatism from the 2005 topographies. Those also showed irregular astigmatism.

Then it was off to test my UCVA. I saw nothing on the eyechart, not even the 20/400 "E". I knew it probably would be an "E" since most eyecharts use this letter on top but I don't go by memory! I didn't think id see 20/400 being a -5 which is moderately high myopia. Throw in around -1 of astigmatism on top of the -5 myopia and you are talking 20/800 being in the ballpark. Then I tested with my computer glasses(-3.5) and saw 20/100 with them. With my distance glasses I see 20/30 in left eye and 20/60 in right eye. My right eye is a little undercorrected, it can do 20/30 BCVA.

This eyechart has 20/400, 200, 100, 80, 70, 60, 50, 40, 30, 25, 20, 15, 10 lines. Some eyecharts have additional lines such as 20/300, 20/250, 20/150, 20/120, 20/12, etc. I had asked him how rare 20/12 was and they don't have that line on their chart. Funny how 70% get 20/15, yet less than 0.1% get 20/10. Wonder what % would be in between.

My aberrometry showed a RMS of .38um in left and .55um in right. I was correct when I figured my right eye is more aberrated. My vision is not as clear in that eye. I also have more astigmatism as well. I would benefit from wavefront guided PRK since im above .3um They say my HOAs could be reduced to normal, but not eliminated alltogether which I already knew.

My pupils do measure in the 8mm range which I already knew. I was surprised that they give everyone the same 6.5mm optical zone with a blend to 9.2mm. This will take 16um/diopter. They say they can correct astigmatism together with myopia no problem. Even my low astigmatism can be corrected(rather, reduced) with a best fit oval ablation profile. I asked about the 8mm optical zone and he says they don't do this as it "eats" too much cornea and there's no room for a blend zone (it would be 12mm) if an 8mm optical zone were to be used. Also a blend zone is important for a smooth transition and it's better than a larger optical zone with no room for any blend zone. He says 1 in 25 people have pupils my size. There's only been one case of poor night vision under the allgretto laser with unknown cause.

He says I can aim for a -1 or -1.5 or anything I feel like. This will greatly reduce the risk of an overcorrection to hyperopia. Ill also save several microns of cornea. I said 350 microns was the safe minimum and he said I am absolutely correct. Get too thin and you get ectasia. Ill have to wear a thin pair of distance glasses for TV and driving but I get to see clearly without reading glasses for everything. I have the accomodation of a 40-45 year old and wear -3.5s for the computer and -5s for distance. Ill probably go for -1 and regress slowly over the years. Ill become more myopic as I get older, said my optometrist. No problem, ill need more myopia as my presbyopia worsens to preserve my near vision and stay out of reading glasses. I spend 75% of my time wearing my -3.5 glasses and only 25% wearing my -5 glasses so this makes sense.

They had a near chart and I was seeing 20/40 with my -5 distance glasses and 20/25 with my -3.5 computer glasses. This is from 16 inches. I have to take my glasses off and look from 8 inches to see the tiny 20/20 line. I can live with 20/25 near vision. I don't get 20/20 distance vision either as the 20/20 line is far too tiny. He says some people see better after lasik/prk than they do with their glasses. I said glasses minify and distort and he says im correct. They may see 20/25 with glasses and get 20/20 after the surgery. If they see 20/20 with glasses, they could be 20/15 after surgery!

He says there's a 97% chance of 20/20, 70% chance of 20/15 and less than 0.1% chance of 20/10! Of the 16,000+ laser surgeries performed only 4 people have ever attained a 20/10 UCVA! I said I read on the internet that 1 in 500 see 20/10 and he said try 1 in 5000! He explained that you need a superb retina and absolutely no refractive error. The exception is a small amount of hyperopia that can be accomodated by a young, non presbyopic eye. The retina limits most people to 20/15 or 20/20, but not everyone's retina will be capable of 20/20, if so, they won't be 20/20 after surgery, not even with glasses.

He says you can be 20/20 with -0.25 but he's never seen a -0.5 attain 20/20 without glasses. No one with 20/20 UCVA can be -0.5, anyone who says so is wrong and measured it wrong. He went on to say that -1 gives you 20/40 to 20/50 and -1.5 gives 20/60 to 20/80 in most of the patients he's refracted. Would be interesting to learn more about the correlation between diopters and 20/xx.

I had thought the chance was 10% of getting to plano and 67% chance of give/take half diopter and 90% chance of give/take one diopter and he says that's wrong, the odds are very, very good of 20/20 UCVA after surgery. He says young people are deliberately overcorrected to +0.25 to account for regression in the future. Also those with a spherical equivalent of plano or a quarter diopter can still see 20/20.

My corneal thickness was measured at 570 and 563, no problem for PRK nor lasik for the matter. I am choosing PRK because the risks are less. I know there's a long healing period and I read lasik is more popular because people want near instant gratification. He said im correct and also explained ill need to wear bandage contact lens for 3-5 days and expect 4-8 week healing period. I am fine with this. When I asked if I should get one eye done at a time, he said they won't be in balance and that the risk is the same for getting one or both eyes done. Guess ill get both eyes done at the same time and aim for a -1 sphere, 0 cylindar and ill end up somewhere in that ballpark.

I will be doing more research and asking more questions. The surgeon has my medical records and will be reviewing it and letting me know the best options and risks once he returns from vacation. I heard I was a candidate but I still want to learn more even though I know plenty. I also need other opinions from other laser centers.

I got a PRK candidacy test at another center:

First, I filled out a lasik checklist. A few of the questions stood out and I am reposting them here as it's informative. Q: Would you be satisfied if your natural vision was greatly improved even if you still had to wear corrective lenses some of the time? A: Yes. Q: Do you feel that good vision without glasses is more important than perfect vision with glasses? A: Yes. Q: Is it acceptable to you that you may need glasses for reading after lasik? A: No.

They are pointing out that lasik(or PRK) can reduce your dependancy on glasses. I expect my natural(UCVA) vision to be greatly improved, which should be easy since im about 20/800! I don't have perfect 20/20 vision with glasses anyway and besides, presbyopes can *not* have perfect vision, they must choose to either see well at distance or at near. If they want both, progressive glasses would be the way to go. Because I can see clear from near, why should I give that up? I am aiming for a -1.5 target so I greatly improve my distance vision while still keeping most of my near vision. Ill be able to see the computer and regular size print without readers. I already wear computer glasses most of the time and only switch to distance glasses when I get out of the house.

The usual battery of tests were done on me, same as the first PRK center. This wavefront test(6.5mm diameter) says I have a half micron of HOAs. It also says I have almost -6d of spherical equivalent. I am more like a -5.5 though. I also got an orbscan that shows the color contours and estimated my cornea at ~550 which is average thickness.

I asked lots of questions and the doctors were impressed with how knowlegeable I am. A female optometrist measured my pupils at between 8mm and 9mm. She gave me a nearvision card and I could read line 5(20/50?) with glasses and without them, I could easily see the smallest line from about 8 inches. She is 43 and presbyopic herself but thanks to being -0.75, she does not yet need reading glasses(her friends are so jealous!) and only needs "cheaters" for night driving. I figured her UCVA was 20/30 and was correct. Her BCVA is an amazing 20/15!

My BCVA is 20/25 to 20/30, the 20/20 line is simply too small because my glasses minify. If you can still see 20/20 with eyes as bad as mine, you have an amazing retina! She did say that I would be surprised by how some people can actually see better than 20/20. I certainly am surprised! The 20/20 line is tiny, just a third of an inch! With my glasses, it's much smaller than that!

I got to meet the surgeon and he was also impressed by how much I knew. He discussed monovision but it's not for me due to anisometropia. I mentioned that I am aiming for a slight undercorrection of -1.5 to preserve some of my near vision and will accept the occasional need for distance glasses. I don't drive and spend alot of time on the computer. He says the laser is accurate to 0.12 diopters and most people end within 0.25 diopters. Get me in the ballpark of -1.5 give or take half diopter and ill be happy. He says I have realistic expectations and am almost certain to achieve that. There's always the option for an enhancement. Ill probably leave well enough alone unless I end up hyperopic or very undercorrected like a -3.

Speaking of expectations, he says alot of people have high expectations and they insist on "perfect" vision. I said they are being unrealistic. If they are presbyopic, they will never be free of glasses and will never see clearly both distance and near. Monovision lets you see clear but with only one eye at a time which isn't for me. I also asked if you reject those who demand "perfect" vision and he laughed and gestured with his foot "I kick them out like this" and swung his leg. My dad later told me he was joking. I told dad that unhappy patients are bad for business because they warn their friends away.

We discussed the fear of overcorrections and he said it's rare to be overcorrected or end up with a large undercorrection. His nomogram actually programs the laser for +0.25 or even +0.5 overcorrection for young people and an undercorrection by the same amount for old people. He will program the laser so ill initally be -1 sphere then ill heal to -1.5. I said even if I end at -1, that's fine with me. There's a 1.5 diopter "buffer" before I end up hyperopic, something that would result in bifocals for presbyopes or rolling the die again on an enhancement. End up slightly undercorrected and no problem, you get to see clear from near and only need glasses for stuff like driving, watching movies and seeing things from a mile away.

We also discussed the fact the Allegretto laser is the only laser that is capable of a prolate profile. This is important for preserving quality of vision and giving the best possible night vision. An oblate ablation results in poorer quality of vision. Also this laser has a blend/transition zone to 9.2mm which results in less of a decrease in night vision compared to older lasers with a small ablation zone and no transition zone. Due to my huge pupils, I expect some decrease in night vision netherless. Ill probably be seeing some halos in the transition zone area. Another reason "perfectionists" should stick with glasses.

He asked if I wore contacts which I replied that I tried them about 20 times and they caused discomfort, irritation, dryness and felt like an eyelash. That's why im considering PRK to improve my vision and be less dependant on glasses. A note to you contact lens wearers, stick with contact lens. They do the job better than laser surgery for less cost and risk. You will be able to see without distance glasses by wearing contact lenses.

He will remove my epithelium with alcohol and a scalpel/brush. He used to do LASEK but it was no better than PRK. 80% of his surgeries he performs are LASIK and 20% are PRK. I correctly said that's because people want near instant gratification and heal in days, not weeks. PRK has less risks and gives better long term results. In exchange, I will endure wearing uncomfortable bandage contacts for 5 days, then deal with fluctuating vision for a few weeks before I fully heal and my vision stabalizes around a -1.5

Wavefront optimized vs. guided was discussed and he says wavefront guided can reduce my HOAs from 0.5um to 0.4um while wavefront optimized may increase them by 0.1 or 0.2 but that I won't notice a difference, especially since ill have -1.5d of blur anyway. He recommends wavefront guided if your HOAs are 0.8um or higher. His laser only does wavefront optimized so youd need to get it done in a different center. I will have to research this more, but I would prefer wavefront guided for myself if I can find a nearby center. It would give me a better chance of preserving more of my night vision.

Thanks for reading my long post regarding what went on during my PRK evaluation. What else should I know of? Anything you wish to share yourself?

Update(Dec 29, 2010) I haven't gotten around to this in a while but at this point im going to wait for Keraflex as well as better lasers(such as the IVIS) to come to a location near me. The PRK center with the custom wavefront Allegretto rejected me as a candidate because I knew too much and asked too many questions! Oh well, their loss as I might have gone ahead back then. The other center also has the Allegretto laser but they don't offer custom wavefront. No thanks, I don't want an increase in HOAs.

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