So I've finally decided to do this. Last week I had another consultation with Dr. Rabinowitz at the end of which I scheduled my Visian ICL implant procedures.
Some doctors do both eyes at the same time or within a few days of each other, some perform the iridotomy a couple of weeks before the implant. My doctor told me that he prefers to do the iridotomy at the same time as the implant because some people experience pain during the iridotomy. He also suggested to do my left eye first (it's the non-dominant eye) and the right eye a week later. That way any unexpected complications could be dealt with before the next eye is tackled. Doing it this way would also give me a chance to reverse the procedure if I don't like the immediate results without my dominant eye ever being touched.
So I scheduled the left eye to be done next Monday, May 19th and the right eye for Tuesday, May 27th. It'll cost me a total of $9,800 and I really don't want to think about that part too much right now... but, hey, it's my eyes. If the surgery turns out alright I'll be ecstatic and the thought of having spent 10k won't bother me too much.
Having the eyes done a week apart will be a bit odd.
You can't wear contacts in whichever eye will be worked on for at least a week before surgery. So right now I'm back to wearing glasses even during training. Of course just now one of the little nose pad thingies had to break off so that the damn frame is scratching up the side of my nose. Great. It's quite annoying but obviously not worth fixing or replacing at this point. Anyhow, what this means is that once my left eye is done I'll still have to wear the glasses for the right eye for a week so i'll have to pop out the left lens during that time. It'll be a weird experience for sure. One eye with ICL vision, the other one with the old glass lens. One eye shielded from the elements the other one exposed.
This is all very exciting (and scary). I'll post more as stuff happens.
Tuesday, May 13, 2008
Thursday, March 27, 2008
VISIAN ICLS: The Final Answer?
After mulling everything over for the last 6 months and almost pulling the plug on the whole idea Dr. Rabinowitz called me up recently to let me know that a new Visian ICL was now available. I've yet to verify all his claims but if they all check out then I've made my decision. I'll have the newer Visian ICLs implanted!
So why those and not anything else?
Well here's an overview of the most important points that lead to my decision:
LASIK: NEVER!
Way too many risks and completely irreversible. Potential night vision problems, post-op permanent dry eye, lower quality vision since the laser shaped area isn't perfectly smooth like the natural eye, permanent destabilization and thinning of the cornea. No way.
INTACS: nope.
Not precise enough (1/2 diopter steps instead of 1/4 diopters), limited availability, insufficient range of prescription (max -3 diopters myopia), optically correct zone is likely too small
PHAKIC IOLS:
VERISYSE PIOLs: no
large cut into cornea likely to increase astigmatism, optically corrected area potentially too small, not available in my prescription (minimum prescription is -5 diopters of myopia). Endothelial cell loss.
VISIAN ICLs: yes
small incisions not likely to increase astigmatism, collamer material supposedly has excellent compatibility with body tissues, designed to repel protein deposits, optically corrected area at 5.9mm is large enough, lenses are completely invisible from the outside. Risk of initial endothelial cell loss. Risk of cataract formation greatly reduced with improved vaulting of new version of the lenses. Lenses can be removed if cataract formation is detected. Worst case scenario: natural lens replacement required due to fully formed cataract. Regular checkups are probably a good idea to catch any developing problems early on. It's still a mixed bag and there's no perfect solution but this seems the most reasonable choice to me. The one thing I'm most worried about is actually optical effects from stray light entering the eye through the tiny cuts created during the iridotomy. But it seems that only relatively few people experience this effect.
Well, there you go.
This wraps up the background posts leading up to my current situation. From here on out I'll simply post about my experiences with my doctor, the procedure itself and life with my new set of eyes.
Stay tuned!
So why those and not anything else?
Well here's an overview of the most important points that lead to my decision:
LASIK: NEVER!
Way too many risks and completely irreversible. Potential night vision problems, post-op permanent dry eye, lower quality vision since the laser shaped area isn't perfectly smooth like the natural eye, permanent destabilization and thinning of the cornea. No way.
INTACS: nope.
Not precise enough (1/2 diopter steps instead of 1/4 diopters), limited availability, insufficient range of prescription (max -3 diopters myopia), optically correct zone is likely too small
PHAKIC IOLS:
VERISYSE PIOLs: no
large cut into cornea likely to increase astigmatism, optically corrected area potentially too small, not available in my prescription (minimum prescription is -5 diopters of myopia). Endothelial cell loss.
VISIAN ICLs: yes
small incisions not likely to increase astigmatism, collamer material supposedly has excellent compatibility with body tissues, designed to repel protein deposits, optically corrected area at 5.9mm is large enough, lenses are completely invisible from the outside. Risk of initial endothelial cell loss. Risk of cataract formation greatly reduced with improved vaulting of new version of the lenses. Lenses can be removed if cataract formation is detected. Worst case scenario: natural lens replacement required due to fully formed cataract. Regular checkups are probably a good idea to catch any developing problems early on. It's still a mixed bag and there's no perfect solution but this seems the most reasonable choice to me. The one thing I'm most worried about is actually optical effects from stray light entering the eye through the tiny cuts created during the iridotomy. But it seems that only relatively few people experience this effect.
Well, there you go.
This wraps up the background posts leading up to my current situation. From here on out I'll simply post about my experiences with my doctor, the procedure itself and life with my new set of eyes.
Stay tuned!
PHAKIC IOLs: Have Your Cake And See It Too
After finding out about the Allegretto laser there was a time period when I was seriously considering doing the LASIK thing. So I started looking for a doctor in LA that had a good reputation, lots of experience, someone I could potentially trust to fiddle around with my eyes. I finally came across Dr. Rabinowitz at the Cornea-Genetic Eye Institute at Cedars-Sinai. He's been my ophthalmologist since fall of 2007.
The institute's website happened to have a bunch of stuff on it including some information about a phakic iol product called Visian ICL. I had never heard of this before which is somewhat weird considering I had been researching this stuff for a while. I always thought artificial lens products were only there to do a full replacement of the actual natural lens in case of severe lens damage due to cataracts etc. But this information was basically about implantable contact lenses for simple vision correction not about replacing the natural lens.
Intriguing!
I started digging into this subject and found that there are 2 major products available:
1) the Verisyse Phakic IOL which goes in front of the iris
and
2) the Staar Visian ICL which goes behind the iris into the chamber in front of the natural lens.
The Verisyse lens is inserted into the eye through a 6mm cut into the side of the cornea and then clamped onto the iris itself. It's available for prescriptions upwards of -5 diopters of myopia and I believe there are toric versions available for correction of astigmatism. It's available with optical diameters up to 6.5mm I believe but that requires a larger cut. This lens is visible from the outside.
The Visian ICL is inserted behind the iris and sort of lodges into the aqueous chamber in front of the natural crystalline lens. It's shaped like a rectangle and measured to fit into the chamber exactly so it won't dislodge and move off center. It's inserted into the eye through a small incision with a syringe. The lens is quite soft and rolled up and simply unfolds once injected into the eye. The ophthalmologist then tucks the corners behind the iris and makes sure it sits right. This is done through 2 other small incisions which I believe are placed at about 12 and 6 o'clock. The space in front of the iris is temporarily filled with a gel that protects the cornea during the procedure which is later flushed out again. The last published numbers I've seen say the Visian ICL has up to 5.5mm optical diameter (version 5?) but Dr. Rabinowitz told me the new one that just got released has 5.9mm (version 6?).
So what's the deal with these lenses then?
Well, the best part about them is this: no part of the optical pathway of the eye is altered and either lens can be removed/replaced again if required or desired. There is no permanent alteration of the cornea or the iris or the lens. Even the Verisyse which is clamped to the iris doesn't seem to damage it. This lens has been around for a while and Dr. Rabinowitz told me about longer term studies where people had the lens until they died. When they removed the lens the iris simply relaxed back into its natural shape at the points it was clamped and no permanent damage from the clamping could be detected.
So are these lenses the perfect solution then?
Not entirely. There are still serious risks and potential side effects. For one the optical diameter is a problem for people with large pupils. If the optical diameter is too small there may be halos, starbursts etc just like with LASIK. If Dr. Rabinowitz told me the truth about the latest Visian ICL though then there's finally a lens with an appropriate optical diameter for my eyes.
Next there is the issue of the incisions. As I've mentioned before any incision in the cornea is likely to introduce or increase astigmatism. A 6mm cut is a massive incision so there's a serious drawback to choosing the Verisyse lens right there. The Visian ICL clearly dominates in this area. 3 very small incisions at the periphery of the cornea are much less of a problem. The studies I've seen indicate negligible increase in astigmatism for the vast majority of people.
Another issue is the required perforation of the iris. Either lens sits in a liquid filled space in the eye. This liquid is pumped through the eye and provides nutrients as well as garbage disposal. Having a foreign object lodged in there is going to impede the flow of liquid leading to increased intra-ocular pressure. To alleviate the problem the iris is punctured in 1 or 2 places near its top edge to aid flow. This is often done pre-op using a laser which punches 2 holes at about 11 and 1 o'clock. Some doctors like mine prefer to cut tiny slits into the iris at 12 o'clock during the operation. The iridotomy can be painful and there is a chance of optical effects caused by scattered unfocused light entering the eye through the hole(s). That's maybe a good reason to go for the 12 o'clock method. That point is more likely to be covered by the eye lid at any time.
Another risk is impact of a foreign body on the endothelium. This is the layer of cells that basically acts like a pump for the liquid that circulates through the chambers behind and in front of the iris. Apparently either lens cause at least some initial endothelial cell loss. You have to have a certain minimum density of endothelial cells to qualify for either procedure. It's kind of a cool test actually: a special camera snaps a microscopic picture of your endothelial cell layer and the doc then uses a click and paint style program to mark and count individual cells.
There are of course plenty more risks common to all eye surgery but one that's specific to the Visian ICL is the problem of contact with the natural lens. If the ICL doesn't vault away from the natural lens properly it can touch it which can in turn lead to inreased risk of cataract. The older versions available here in the US had a pretty significant cataract risk associated with them and Dr. Rabinowitz said he doesn't use them anymore. But a newly released version of the lens that had already been available in Europe for some time has much improved vaulting and the risk is now at below 2% which isn't so bad given that most actual patients tend to be older and thus tend to have a naturally higher risk for cataracts. The risk for a relatively young person with relatively healthy eyes might be lower than the average found in the studies.
The institute's website happened to have a bunch of stuff on it including some information about a phakic iol product called Visian ICL. I had never heard of this before which is somewhat weird considering I had been researching this stuff for a while. I always thought artificial lens products were only there to do a full replacement of the actual natural lens in case of severe lens damage due to cataracts etc. But this information was basically about implantable contact lenses for simple vision correction not about replacing the natural lens.
Intriguing!
I started digging into this subject and found that there are 2 major products available:
1) the Verisyse Phakic IOL which goes in front of the iris
and
2) the Staar Visian ICL which goes behind the iris into the chamber in front of the natural lens.
The Verisyse lens is inserted into the eye through a 6mm cut into the side of the cornea and then clamped onto the iris itself. It's available for prescriptions upwards of -5 diopters of myopia and I believe there are toric versions available for correction of astigmatism. It's available with optical diameters up to 6.5mm I believe but that requires a larger cut. This lens is visible from the outside.
The Visian ICL is inserted behind the iris and sort of lodges into the aqueous chamber in front of the natural crystalline lens. It's shaped like a rectangle and measured to fit into the chamber exactly so it won't dislodge and move off center. It's inserted into the eye through a small incision with a syringe. The lens is quite soft and rolled up and simply unfolds once injected into the eye. The ophthalmologist then tucks the corners behind the iris and makes sure it sits right. This is done through 2 other small incisions which I believe are placed at about 12 and 6 o'clock. The space in front of the iris is temporarily filled with a gel that protects the cornea during the procedure which is later flushed out again. The last published numbers I've seen say the Visian ICL has up to 5.5mm optical diameter (version 5?) but Dr. Rabinowitz told me the new one that just got released has 5.9mm (version 6?).
So what's the deal with these lenses then?
Well, the best part about them is this: no part of the optical pathway of the eye is altered and either lens can be removed/replaced again if required or desired. There is no permanent alteration of the cornea or the iris or the lens. Even the Verisyse which is clamped to the iris doesn't seem to damage it. This lens has been around for a while and Dr. Rabinowitz told me about longer term studies where people had the lens until they died. When they removed the lens the iris simply relaxed back into its natural shape at the points it was clamped and no permanent damage from the clamping could be detected.
So are these lenses the perfect solution then?
Not entirely. There are still serious risks and potential side effects. For one the optical diameter is a problem for people with large pupils. If the optical diameter is too small there may be halos, starbursts etc just like with LASIK. If Dr. Rabinowitz told me the truth about the latest Visian ICL though then there's finally a lens with an appropriate optical diameter for my eyes.
Next there is the issue of the incisions. As I've mentioned before any incision in the cornea is likely to introduce or increase astigmatism. A 6mm cut is a massive incision so there's a serious drawback to choosing the Verisyse lens right there. The Visian ICL clearly dominates in this area. 3 very small incisions at the periphery of the cornea are much less of a problem. The studies I've seen indicate negligible increase in astigmatism for the vast majority of people.
Another issue is the required perforation of the iris. Either lens sits in a liquid filled space in the eye. This liquid is pumped through the eye and provides nutrients as well as garbage disposal. Having a foreign object lodged in there is going to impede the flow of liquid leading to increased intra-ocular pressure. To alleviate the problem the iris is punctured in 1 or 2 places near its top edge to aid flow. This is often done pre-op using a laser which punches 2 holes at about 11 and 1 o'clock. Some doctors like mine prefer to cut tiny slits into the iris at 12 o'clock during the operation. The iridotomy can be painful and there is a chance of optical effects caused by scattered unfocused light entering the eye through the hole(s). That's maybe a good reason to go for the 12 o'clock method. That point is more likely to be covered by the eye lid at any time.
Another risk is impact of a foreign body on the endothelium. This is the layer of cells that basically acts like a pump for the liquid that circulates through the chambers behind and in front of the iris. Apparently either lens cause at least some initial endothelial cell loss. You have to have a certain minimum density of endothelial cells to qualify for either procedure. It's kind of a cool test actually: a special camera snaps a microscopic picture of your endothelial cell layer and the doc then uses a click and paint style program to mark and count individual cells.
There are of course plenty more risks common to all eye surgery but one that's specific to the Visian ICL is the problem of contact with the natural lens. If the ICL doesn't vault away from the natural lens properly it can touch it which can in turn lead to inreased risk of cataract. The older versions available here in the US had a pretty significant cataract risk associated with them and Dr. Rabinowitz said he doesn't use them anymore. But a newly released version of the lens that had already been available in Europe for some time has much improved vaulting and the risk is now at below 2% which isn't so bad given that most actual patients tend to be older and thus tend to have a naturally higher risk for cataracts. The risk for a relatively young person with relatively healthy eyes might be lower than the average found in the studies.
ALLEGRETTO: The World Isn't Flat
I have to admit it... this one almost won me over!
Conventional LASIK systems have a severe flaw: the mathematical model used to drive the spatial adjustments of the laser assumes that the surface of the eye is flat. Such simplifications and approximations were needed to make the systems capable of reacting and operating quickly enough to perform the procedure on a live eye.
Except of course that the eye isn't flat.
The result of this is that these lasers are rather limited in terms of accuracy. This impacts the results in two major ways:
1) it limits the size of the optically corrected zone because the error of correction increases the further away the laser operates from the optical axis of the eye. The smaller the corrected zone the greater the chances of experiencing night vision problems. Your iris may open up beyond the optically corrected zone (max pupil diameter is about 6.5mm with conventional lasers) and you will begin to see artifacts such as halos, star bursts, glare and double or triple vision depending on the size difference between the optically corrected zone and the degree to which iris opens up in darkness.
2) vision correction is only accurate in the exact center of the cornea. Light passing through the periphery of the optically correct zone will not be corrected perfectly. This will reduce the overall quality of the result and so you're pretty much guaranteed never to get 20/20 vision from a laser procedure if conventional systems are used.
But then there came the Allegretto... the first laser with a mathematical model of the eye that described it as rounded. This allows the system to create optically corrected zones for eyes with pupil diameters exceeding 6.5mm and to reduce the level of error in the periphery of the corrected zone. Very nice indeed. It also comes with a few other improvements such as a different laser beam profile that apparently reduces stepping between ablation "pixels".
To me this system was the first one that seemed to be in the sweet spot. Capable of acceptable levels of accuracy and of avoiding those dreaded night vision effects.
So what kept me from choosing LASIK done with the Allegretto? Well, I still didn't really feel comfortable. Even the bigger optical zone still comes with a transitional area prone to introduce optical errors. Much more though the thought of doing something irreversible to my eyes, of reducing the structural stability and integrity of my corneas, of potentially suffering for the rest of my life from screwed up vision unable to do anything about it, these thoughts just didn't sit right with me and I couldn't get myself to pull the trigger.
But let me just say this much: if I absolutely had to I'd pick Intralase for flap cutting and the Allegretto laser for doing the correction. Or of course hypothetical newer systems that improve on those two technologies. Anything less than what these two can do would simply be unacceptable to me.
Conventional LASIK systems have a severe flaw: the mathematical model used to drive the spatial adjustments of the laser assumes that the surface of the eye is flat. Such simplifications and approximations were needed to make the systems capable of reacting and operating quickly enough to perform the procedure on a live eye.
Except of course that the eye isn't flat.
The result of this is that these lasers are rather limited in terms of accuracy. This impacts the results in two major ways:
1) it limits the size of the optically corrected zone because the error of correction increases the further away the laser operates from the optical axis of the eye. The smaller the corrected zone the greater the chances of experiencing night vision problems. Your iris may open up beyond the optically corrected zone (max pupil diameter is about 6.5mm with conventional lasers) and you will begin to see artifacts such as halos, star bursts, glare and double or triple vision depending on the size difference between the optically corrected zone and the degree to which iris opens up in darkness.
2) vision correction is only accurate in the exact center of the cornea. Light passing through the periphery of the optically correct zone will not be corrected perfectly. This will reduce the overall quality of the result and so you're pretty much guaranteed never to get 20/20 vision from a laser procedure if conventional systems are used.
But then there came the Allegretto... the first laser with a mathematical model of the eye that described it as rounded. This allows the system to create optically corrected zones for eyes with pupil diameters exceeding 6.5mm and to reduce the level of error in the periphery of the corrected zone. Very nice indeed. It also comes with a few other improvements such as a different laser beam profile that apparently reduces stepping between ablation "pixels".
To me this system was the first one that seemed to be in the sweet spot. Capable of acceptable levels of accuracy and of avoiding those dreaded night vision effects.
So what kept me from choosing LASIK done with the Allegretto? Well, I still didn't really feel comfortable. Even the bigger optical zone still comes with a transitional area prone to introduce optical errors. Much more though the thought of doing something irreversible to my eyes, of reducing the structural stability and integrity of my corneas, of potentially suffering for the rest of my life from screwed up vision unable to do anything about it, these thoughts just didn't sit right with me and I couldn't get myself to pull the trigger.
But let me just say this much: if I absolutely had to I'd pick Intralase for flap cutting and the Allegretto laser for doing the correction. Or of course hypothetical newer systems that improve on those two technologies. Anything less than what these two can do would simply be unacceptable to me.
Wednesday, March 26, 2008
INTRALASE: NextGen Flaps
One of the problems with LASIK had always been cutting the flap. The doctor would cut a corneal flap using a Microkeratome.
If a given doctor is a cheapskate he may be tempted to reuse his blades a few times resulting in dulled cutting edges that would tear rather than cut the flaps and massively increase the risk of infection.
A good doctor should actually change blades between eyes, not just between patients.
But even a shiny clean new blade cuts a flap that varies at least 50% in thickness. A dull blade would result in an even more irregular flap. The problem is that increased irregularity of the flap makes it harder for the eye to heal post-op. Not that it ever truly heals, mind you.
The translucency of the corneal cells stems in part from their being suspended in a state of perpetual near-death. They don't do much. There isn't a lot of blood there providing nutrients and oxygen. Instead specialized pumping cells sort of push a liquid through the eye that washes some nutrients up to the cells and carries away some garbage. Basically this means that these cells don't really do much. They sort of reattach after being cut but it'll never be the same again as before.
This makes cutting a perfect flap very important. The better the flap the more structurally stable the cornea will be post-op and the lower the risk will be of suffering from epithelial ingrowth and other complications.
Also, cutting into the eye is always likely to induce or increase astigmatism. The less irregular the cut the better the chance to avoid this kind of effect as well.
IntraLase addressed that problem or at least reduced its impact. Laser-based flap cutting is much more precise and predictable.
At this point I felt like a major hurdle had been cleared. This was the first laser tool I'd even consider to let anywhere near my eyes.
However, that was only the first part. I still didn't see any improvements in the actual vision correction part of the procedure.
If a given doctor is a cheapskate he may be tempted to reuse his blades a few times resulting in dulled cutting edges that would tear rather than cut the flaps and massively increase the risk of infection.
"Many Microkeratome components used for LASIK are licensed, "regulated" and approved by the FDA solely as single-use, disposable medical devices, but the FDA states the FDA has No jurisdiction to enforce Federal laws regarding these FDA approved medical devices. Hundreds of LASIK Doctors have admitted reusing these single use blades, but none have lost their medical licenses and only a few have even been placed on temporary probation (to my knowledge).
I was totally shocked when the CDC infectious disease contact said there is a patient benefit from Doctors saving money by reusing single-use, disposable blades (even if it exposes patients to potential harm without sterilization). The FDA working group met and requested a full copy of that survey article below that indicates that 21% of Doctors admitted they reuse microkeratome blades for LASIK."
(quoted from LasikLiberty.com)
A good doctor should actually change blades between eyes, not just between patients.
But even a shiny clean new blade cuts a flap that varies at least 50% in thickness. A dull blade would result in an even more irregular flap. The problem is that increased irregularity of the flap makes it harder for the eye to heal post-op. Not that it ever truly heals, mind you.
The translucency of the corneal cells stems in part from their being suspended in a state of perpetual near-death. They don't do much. There isn't a lot of blood there providing nutrients and oxygen. Instead specialized pumping cells sort of push a liquid through the eye that washes some nutrients up to the cells and carries away some garbage. Basically this means that these cells don't really do much. They sort of reattach after being cut but it'll never be the same again as before.
This makes cutting a perfect flap very important. The better the flap the more structurally stable the cornea will be post-op and the lower the risk will be of suffering from epithelial ingrowth and other complications.
Also, cutting into the eye is always likely to induce or increase astigmatism. The less irregular the cut the better the chance to avoid this kind of effect as well.
IntraLase addressed that problem or at least reduced its impact. Laser-based flap cutting is much more precise and predictable.
At this point I felt like a major hurdle had been cleared. This was the first laser tool I'd even consider to let anywhere near my eyes.
However, that was only the first part. I still didn't see any improvements in the actual vision correction part of the procedure.
WAVEFRONT: Ultramegasupervision!
For a number of years nothing seemed to happen. There wasn't any real obvious progress in terms of the laser procedures, the Intacs idea was clinically dead for a while, nothing new appeared on the horizon. The LASIK procedures did get a little better and little more refined. More people were doing it. But I just wasn't convinced.
The only big change during that time was the advent of wavefront technology in the world of LASIK. Loosely based on solutions used for high-powered telescopes which needed to correct minute atmospherical disturbances in order to increase optical resolution it was touted as a great revolution in vision correction. By correcting the small optical imperfections of the eye one could not only correct one's vision but make it "superhuman".
This was and still is not much more than a marketing scheme. First of all the human eye isn't some mechanical optical system like a camera's or a telescope's. The state of the eye is in constant, albeit subtle flux. For example one's exact prescription will vary during the day depending on the level of one's fatigue, the brightness of the environment and other factors. My tiny bit of astigmatism comes and goes and can only be measured as 0.25 diopters in terms of statistics. Secondly even if your eyes would have the necessary resolution in terms of detail to notice the difference between wavefront and non-wavefront treatment which most people's eyes don't (mine do though) it wouldn't really matter. At that level of detail the coarseness of the laser shaped cornea would likely undo any improvements anyhow. The laser doesn't exactly create a smooth surface but something akin to a pixelated approximation. This is like comparing a camera with a high-end lens to another with a really cheap one. Pictures taken with either may be perfectly in focus but the images taken through the high-end lens will have more discernible detail all else being the same.
So it seemed like Wavefront technology was maybe potentially delivering some small improvement but the risk of the procedure was really still the same. Sort of like playing MegaMillions instead of Super Lottery.
In any case not a good enough reason for me to suddenly decide in favor of a laser treatment.
The only big change during that time was the advent of wavefront technology in the world of LASIK. Loosely based on solutions used for high-powered telescopes which needed to correct minute atmospherical disturbances in order to increase optical resolution it was touted as a great revolution in vision correction. By correcting the small optical imperfections of the eye one could not only correct one's vision but make it "superhuman".
This was and still is not much more than a marketing scheme. First of all the human eye isn't some mechanical optical system like a camera's or a telescope's. The state of the eye is in constant, albeit subtle flux. For example one's exact prescription will vary during the day depending on the level of one's fatigue, the brightness of the environment and other factors. My tiny bit of astigmatism comes and goes and can only be measured as 0.25 diopters in terms of statistics. Secondly even if your eyes would have the necessary resolution in terms of detail to notice the difference between wavefront and non-wavefront treatment which most people's eyes don't (mine do though) it wouldn't really matter. At that level of detail the coarseness of the laser shaped cornea would likely undo any improvements anyhow. The laser doesn't exactly create a smooth surface but something akin to a pixelated approximation. This is like comparing a camera with a high-end lens to another with a really cheap one. Pictures taken with either may be perfectly in focus but the images taken through the high-end lens will have more discernible detail all else being the same.
So it seemed like Wavefront technology was maybe potentially delivering some small improvement but the risk of the procedure was really still the same. Sort of like playing MegaMillions instead of Super Lottery.
In any case not a good enough reason for me to suddenly decide in favor of a laser treatment.
INTACS: Two Rings To Correct Them All
While I was waiting on the sidelines observing the rapid increase in popularity of LASIK and worrying about its side and long term effects I came across a company that had gotten the FDA to approve a totally different technology for vision correction: Intacs corneal rings.
Intacs were supposed to correct vision by reshaping the cornea without interfering with the optical pathway of the eye at all. Basically Intacs are ring shaped implants that are shoved into the cornea squeezing it into a different shape thus correcting focus. Now this sounded much more appealing to me. The optical pathway would be very close to unaltered (not completely unaltered because any violation of the physical integrity of the cornea can introduce or increase astigmatism) and the rings could be removed again later if there were complications or the need to change the prescription. Unfortunately at the time few doctors were using them and they were only approved for mild myopia yet (up to 3 diopters). But Intacs had already been submitted for FDA approval for correction of moderate myopia (which is the category I fall into) and so I decided to wait it out. Unfortunately LASIK's success completely destroyed the market for less risky but more expensive alternatives. The company seemed to have gone defunct eventually and Intacs only reappeared again later on and are now mostly used for fixing Keratoconus induced misshapen corneas (and less for vision correction. Plus they're still not available for anything above 3 diopters in the US.
Looking back I'm glad I wasn't able to get them. Intacs weren't particularly accurate at least back then (1/2 diopter steps rather than 1/4 diopter steps) and the optically corrected zone is probably too small for me (my eyes open up to 5.8mm and 6.2mm respectively during night vision) which would almost certainly have resulted in halos and other nightvision optical effects.
Intacs were supposed to correct vision by reshaping the cornea without interfering with the optical pathway of the eye at all. Basically Intacs are ring shaped implants that are shoved into the cornea squeezing it into a different shape thus correcting focus. Now this sounded much more appealing to me. The optical pathway would be very close to unaltered (not completely unaltered because any violation of the physical integrity of the cornea can introduce or increase astigmatism) and the rings could be removed again later if there were complications or the need to change the prescription. Unfortunately at the time few doctors were using them and they were only approved for mild myopia yet (up to 3 diopters). But Intacs had already been submitted for FDA approval for correction of moderate myopia (which is the category I fall into) and so I decided to wait it out. Unfortunately LASIK's success completely destroyed the market for less risky but more expensive alternatives. The company seemed to have gone defunct eventually and Intacs only reappeared again later on and are now mostly used for fixing Keratoconus induced misshapen corneas (and less for vision correction. Plus they're still not available for anything above 3 diopters in the US.
Looking back I'm glad I wasn't able to get them. Intacs weren't particularly accurate at least back then (1/2 diopter steps rather than 1/4 diopter steps) and the optically corrected zone is probably too small for me (my eyes open up to 5.8mm and 6.2mm respectively during night vision) which would almost certainly have resulted in halos and other nightvision optical effects.
Subscribe to:
Posts (Atom)
