Real life complication rates of Lasik - Nidek EC-5000 excimer laser

[Scientist]

Just thought it would be interesting to pull out some large case studies, laser by laser and look at complication rates. FDA clinical trials are performed by the best surgeons with an ideal patient population. What really happens when someone like you or me walks into a laser vision clinic? We may get some idea from this large retrospective study of 683 eyes on the Nidek lEC-5000 excimer laser:

J Refract Surg. 2003 Mar-Apr;19(2 Suppl):S247-9.
Complications of photorefractive keratectomy and laser in situ keratomileusis.
Lui MM, Silas MA, Fugishima H.

METHODS: Retrospective study of excimer laser in 683 eyes: PRK was
performed in 103 eyes and LASIK was performed in 580 eyes using the
Nidek EC-5000 excimer laser.


thin flaps 0.73%
free caps 0.58%
buttonholes 0.43%
small flaps 0.43%
striae that necessitated lifting and irrigating the flap 2.04%
Epithelial ingrowth 1.17%
Interface debris 0.58%
haze 0.43%
glare 0.43%
microwrinkled flaps 4.39%
postoperative dry eye with pain 6.15%
dislocated flaps or flap glare 0.43%
decentered ablations 0.29%
toxic keratitis 0.29%
Loss of 1 or more lines of BSCVA 0.73%
Keratoconus 0.29%
----------
TOTAL COMPLICATIONS 19.39%

Late postoperative complications were 98 cases of spherical equivalent
refraction more than or equal to 1.00 D (14.3%) with 6 months follow-up.

So let's add patients whose corrections were missed: 14.30%

----------
33.69%

So around 33.7% of patients had a complication or missed their correction
by at least a diopter. Ready to sign up for surgery? And I suppose you
are wondering what the authors concluded from this study?

"CONCLUSION: Refractive surgery with the Nidek EC-5000 excimer laser was safe, with few complications."

Did they not add up their own numbers???

[Rebecca Petris]

Scientist,

Adding up the percentages of patients (or eyes) with a specific complication cannot possibly, in my opinion, be an accurate way of estimating the percentage who had a complication. There is considerable overlap between these categories. As just one example, loss of BSCVA is almost certainly related to other listed categories (such as buttonhole flaps).

[Scientist]

Rebecca, yes - Adding does assume that complications occur singly. Some unfortunate individuals may have multiple complications (isn't that actually worse?), but incidence per individual complication can be assumed to be calculated correctly. The individual %'s for some complications are not small, many complications ARE likely unrelated, and therefore it is easy to disagree with the author's conclusion that the complication rate is 'low'. The problem I see is that the authors didn't design their study with the help of good statisticians so that they could get at numbers such as overall complication rate, rates stratified by complication type in association with various pre-surgical variables such as pupil size, preoperative prescription, degree of astigmatism, corneal thickness and other factors. These sorts of studies are lacking. If lasik were performed in hospitals with independent oversight we would have accurate figures for complication rates. Let's take the most conservative scenario and say that the complications in this study occur in 3's - this would still leave a complication rate higher the general public would likely accept. If they knew.

I agree with Rebecca, and I will even go further. Let's suppose that a company was manufacturing eyeballs on an assembly line, and each of the items you listed was a defect. Then let's suppose that some eyeballs would have no defect, some would have one defect, others would have multiple defects. If the company was committed to a zero defect policy, then the occurrence of a single defect would cause the eyeball to be rejected. Therefore, eyeballs with multiple defects would not be treated any differently than those with but a single defect. However, in the real world, defects are given a rating according to their seriousness. For example, a cosmetic defect vs. a functional defect. In this situation, an eyeball with no defects would be considered "perfect," while eyeballs with one or more defects might be considered "barely acceptable" or "not acceptable" based upon the number of defects and their relative seriousness. Microstriae would surely be considered a defect, but it is conceivable that some microstriae may not adversely affect the functioning of the eyeball, depending on the size and location.

I hope I haven't upset anybody with this crude analogy.

DrG

[Scientist]

When you have many possible complications, each with a low incidence, the odds of having any single complication increase. Please factor in this notion with the fact that the procedure induces higher order aberrations (wavefront too, just less), severs the corneal nerves and leave the patient with a permanent interface - overall the picture is not attractive. We haven't even touched contrast senstitivity. Anything that increases light scattering can increase loss of contrast senitivity. Maybe those microstriae are more troublesome than you think. All the mess that lasik puts into the cornea gives contact lens fitters like you the chance for a real 'wow' factor when you put a patient in the right lens.

[Lucy]

Our Dr. G says:

I hope I haven't upset anybody with this crude analogy.

Of course you haven't. You explained it so those of us without multiple degrees can understand it. It might only include me. It saves me from asking for an explanation.

[Glenn]

To expand on DrG’s points a bit further, these figures represent the occurrence of complications, not unresolved complications or complications that cause a degradation in visual function. Thin flaps, free caps, buttonholes, small flaps, striae that necessitated lifting and irrigating the flap, epithelial ingrowth, postoperative dry eye with pain, and even haze and glare commonly resolve with treatment and healing. Nobody wants to deal with any of these issues, but the path of refractive surgery is not always a smooth road.

Additionally, missing the target is not quite the same as inducing a complication that causes vision degradation. Keeping in mind that the purpose of refractive surgery is to provide the convenience of a reduce need for corrective lenses, this purpose may be achieved even without totally eliminating the need for corrective lenses.

[Scientist]

Originally Posted by Glenn - USAEyes.org

Nobody wants to deal with any of these issues, but the path of refractive surgery is not always a smooth road

Then perhaps the path of refractive surgery should not be 'hyped' as a smooth road. People with any of those listed complications (except maybe some of the missed corrections, depending on severity and direction) are going through hell. Many complications of refractive surgery are not fixable. There are plenty of unfixables here on the bulletin board who would be more than happy to tell you about what that's like.

[Glenn]

You won’t see me hyping refractive surgery as being a 20-Minute Miracle.

I do not discount the difficulties an unfortunate few individuals endure due to poor refractive surgery outcomes. Let us not forget that our organization operates the ComplicatedEyes.org sister website specifically to provide support and assistance for those who have problems with refractive surgery.

[Casey]

Originally Posted by Glenn - USAEyes.org

You won’t see me hyping refractive surgery as being a 20-Minute Miracle

No, of course not. You hype it as being a 6 month, overwhelmingly successful surgery. Apparently you do not count life-altering complications such as severe dry eyes and night vision disability as complications.

[Scientist]

Originally Posted by Casey

You hype it as being a 6 month, overwhelmingly successful surgery.

By the way, Glenn, how do you figure a 200 micron flap, a residual 200 micron stromal bed and 14 D of spherical aberration, with a 3.4 mm OZ is going to resolve at six months??? Her surgeon SWORE to her that it ABSOLUTELY WOULD!!!

[Glenn]

Casey,

Accurate information is important for anyone considering refractive surgery. In actual fact, LASIK and PRK are relatively successful procedures at the six-month postop point. I do not consider dissemination of relevant and accurate information as “hype”. Your accusation that our organization does not count life-altering complications such as severe dry eyes and night vision disability as complications is inaccurate and completely unfounded.


Scientist,

I did not tell Casey (or anyone) that a 200 micron flap, a residual 200 micron stromal bed, 14 D of spherical aberration, and a 3.4 mm OZ is going to resolve at six months. A prognosis provided by Casey’s doctor has nothing to do with me.