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.