by PRKorIntacs » Sun Mar 14, 2010 1:15 pm
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.
edit:
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?