This week we'll discuss important points about patient-specific LVC risks which even many otherwise well-informed patients are simply not aware of before surgery. These are things which, even if included in the consent form at all, will often be "coded" in semi-doctor-speak. They may be written in a fashion which does not convey the probable impact the relevant complications can have on the patient's visual function or comfort. Most critically, though, they do not apprise the patient of his/her increased risk level vs. the general populace.

I hasten to say that the laser vision correction “hot buttons” listed below are NOT discussed comprehensively or in any depth at all and they are also only a fraction of the topics that deserve coverage. But for the full skinny, I'm afraid you'll have to wait until Iwrite the Ultimate Consumer Guide which I've been trying so long to find time to write. So in the meantime:

What are LVC “Hot Buttons”? (No, no, they are not warmed-over donor corneas, called buttons by doctors.) I use this term to refer to issues in laser eye surgery which (1) have the potential to adversely affect your results and/or your satisfaction with your outcome in a big, big way; (2) are a big part of defining your personal risk profile for known adverse effects of laser eye surgeries – that is, are things which place you at higher or lower risk than the average Joe with the average eyeballs; and (3) have disappointingly few and small (if any) statistical samples associated with them none of which are available uniformly to all patients to help them evaluate their risk level.

I guess another way to say it would be that Hot Buttons are the things we patients with bad outcomes wish someone had told us, because most of us had risk factors that we didn't know were risk factors. Granted, some patients are super-consumers and get super-educated before surgery, but at the same time, the more people get LVC, the more people simply tend to assume that it's as simple as getting it done. So that's what we're here for.
 

HOT BUTTON #1: Pupil size.

I won't expound at length. Go read The Lone Dog's first three articles (here, here, and here) if you have time. The most important things to know are:

a. Pupil size matters. What? Oh, you've been reading the medical literature? Well, yes, now that you come to mention it, it is true that certain people in learned (or not-so-learned, depending what you think about gross lapses in scientific protocol) scientific circles have published studies recently suggesting that pupil size cannot predict night vision disturbances. I'll dissect those when I have more time on my hands. The simple fact is that basic common sense, as well as basic optical principles, as well as conventional practice in refractive surgery for many years including right now, suggest that pupil size is very important and that you should get a laser treatment bigger than or equal to your pupil size. At the end of the day if it really didn't matter, pupil measurement device manufacturers wouldn't be making money hand over fist.

b. Pupil size matters to your vision quality. Things like whether you can drive safely at night, or distinguish your brown socks from your black socks. L'il stuff like that.

c. Pupil size is too frequently mismeasured – on the small side. That is anecdotal, but hey, take it from someone who has spoken with one helluva lotta patients with >=7mm pupils who were measured at <=6mm. This is because there is no decent standard protocol for measuring dark-adapted pupils.   In my opinion, now that wide zone (>6mm) lasers are available, pupil mismeasurement is one of the most significant risks remaining.

d. You should find out your true dark-adapted pupil size before making any decisions about laser eye surgery, unless you really don't mind gambling with your vision.
 

HOT BUTTON #2: High prescription.

I am very, very happy to be able to say that these days, reputable doctors are much more likely to be very cautious about very high prescriptions than they were a few years ago. Experience does pay off, I guess. But that does NOT mean there aren't many out there lasering high prescription patients. And when it comes down to it, people with very high prescriptions are some of the most motivated to pursue surgery. (Believe me, I know!)

I have two key worries about high prescriptions:

a. The higher the prescription, the more loss of vision quality. I haven't looked recently so I don't know how many scientific studies say so, but almost any surgeon will at least agree over a beer that this is the case.   What is loss of vision quality? It means that you can read much or all of the eyechart at your doc's office but you're still miserable because though decipherable it looks so awful; AND, it doesn't get any better when you're wearing glasses! It means things like contrast sensitivity loss (where dim lights will never again feel romantic) and night vision disturbance (starbursts, haloes and other pretty but distracting fireworks displays around point-light sources) and ghosting (where you see two or more of everything – it's amusing, for the first thirty seconds or so). WHY does this happen? Lots of reasons. One, it's simply the nature of the beast. Corneas were meant to be prolate. Flatten them too much, and your optics get trashed. Also, the higher the prescription, the more tissue they have to vaporise (excuse me, ablate) and the longer it takes, other issues start coming into play. Also, the higher the prescription, the less likely you will have enough corneal thickness to allow them to do a wide-zone treatment, and if you have a small-zone treatment but had large pupils, well, same problems.

b. The higher the prescription, the worse the dry eye (esp with LASIK). Indeed, most (though certainly not all) of the truly dreadful dry eye cases I know had very high corrections. More about dry eye later on. For the moment let's just say it's very serious.

c. Do you really want to subject yourself to BOTH of those risks at the same time? If you think so, go onto the D'Eyealogues bulletin board, register, and post the following question in the Open Forum: “Anybody with a high prescription before LASIK want to share their story?”

So what's a high prescription? Well, the American Association of Ophthamology (AAO) once said 8 diopters of myopia (i.e. -8.00) was the threshold. I certainly would not be inclined to peg it any higher than that though I might go slightly lower. It also depends on pupil size and corneal thickness. Speaking of which…
 

HOT BUTTON #3: CORNEAL THICKNESS

This is where it starts getting cooooomplicated, because hot buttons 1, 2 and 3 are all intertwined. I mean, the bigger your pupils (if they measure them right) and/or the higher your prescription, the deeper they're going to have to go, so it's not just a simple absolute little question of “are your corneas thick enough?” I'll try to touch briefly on a few of the key points I want you to understand during your risk evaluation process.

Please note that the following points are specific to LASIK:

a. Surgery will penetrate deep into your cornea... I get a real kick out of the promotional videos you see at laser centers or online on the websites. I sometimes suspect that the reason they show you slick graphics and not live surgeries might not be just because of the gross-out factor. In nearly ever video I've ever seen, the treatment appears to be FAR more superficial than it in fact is and you would never guess that the reality is that the flap alone may cut a quarter to a third of your tissue – that's before they start lasering. In total, depending on your prescription you can expect to have one third to one half of your total corneal thickness affected. – What's even more amazing is some of these promotional schemes that use phrases like “Lifetime guarantee” (referring to prepayment of “enhancement procedures”). That kind of thing ought to be outlawed, in your editor's humble opinion. It clearly and blatantly suggests to non-doctor consumers that you have a lifetime supply of cornea and that whittling away at it every so often is just fine. But I digress. Another day, another diatribe.

b. …And, the depth of penetration matters – permanently… The other part of the graphics that is vaguely amusing is that after the lasering part, when the flap gets folded back down and patted into place, it appears to magically rebond to the rest of the cornea and it becomes a lovely uniform cornea again. Gee, how nice. Only, that's not quite right. The fact is, slicing through cornea to create the LASIK flap is NOT like cutting your finger (well, minus the blood) and letting it heal. I'm not a biochemist or dermatologist or ophthalmologist, but even I can understand that if the top part and the bottom part “healed” like a wound heals, there would be some scar tissue getting in the way of your vision. It is the absence of this process which allows LASIK to have such stunning next-day results for so many people. No, the corneal flap does not “heal” in that sense. It can actually be lifted rather easily (after you poke at the edges a little) for years and years later. I am not saying that is a problem; for those who need further surgery it's supposed to be a benefit. But the salient fact is that (magic phrase, listen carefully) the flap does not contribute to the long-term structural stability of the cornea. (That's not anecdotal evidence from Rebecca by the way – I wouldn't know. That's based on broadly known and accepted scientific research.) What does that mean in plain English? Well, simply put: You have pressure inside your eye. Your cornea is the outside part of your eye. Your cornea needs to be thick enough (strong enough) to withstand the pressure inside your eye. Otherwise, you start getting bulges…. And a condition called corneal ectasia, which believe me you don't want, unless you like the idea of bad vision, uncomfortable treatments, and a high probability of needing corneal transplantation.

c. …But, depth of penetration is not altogether predictable... This is one of the slightly scary parts; don't worry too much, but don't bury your head in the sand either – you have to inform youself in order to protect yourself by choosing a very conservative treatment plan or being willing to forego surgery if it's too risky for your corneas. Anyway, you know the fancy blades ("microkeratome" is a more soothing name, but it just means "little cornea-cutter") that they make the flap with? Well, those blades have settings which specify how thick to cut the flap. But many major brands have been shown to have a very wide range in terms of what they actually achieve. (See the Headlines section of Keratoscoop for links to some useful abstracts – try the Flap, Flap, Flap article.) Where am I going with this? If you are cutting it close in terms of the expected total penetration of your surgery vs. the amount of minimum tissue that can be left underneath the flap with safety, you could be placing yourself at risk because the microkeratome could cut a thicker flap than expected and put you over the limit.

d. So… you need to be conservative and leave room for error, doubt, known variances, and all those things. “But,” you say, “That's my doctor's job.” “I couldn't agree more,” I say. “And would you like to talk to a few ectasia patients I know who were operated on by very reputable doctors?” Take matters into your own hands. Take your risk analysis into your own hands. That's all I'm asking. And it's for your own good, it really is.
 

Oh dear, oh dear — where has the time gone? I have only covered three, and skipped loads of stuff on each of them. Sorry, but then, if you've made it this far, you really deserve a break anyway.

Tune in next week for more LVC Hot Buttons!