Advanced Vision Testing & LASIK
Expert advice on the right level of investment in topography and wavefront technologies.
By Daniel S. Durrie, M.D.

To perform your best LASIK, you need to invest in the proper vision-testing equipment for patient screening and management. But you don't want to collect a lot of equipment out of which you won't get the full value.

"What do I need to buy?" is a question I'm asked often. My answer is that what you buy in the way of topography and wavefront technology depends on how involved with LASIK you want to be, how many procedures you want to perform. If your goal is to perform:

50 or fewer LASIKs per month. At this level, a standard placido disk topographer, most of which now cost $2,000 or less, will serve you well. You'd use it in unusual cases and to screen patients to rule out keratoconus and detect contact lens-related corneal warpage. As a surgical planning tool, it would help you to map the direction and magnitude of astigmatism. And, post-op, it would help you to match patients' symptoms with the shape of their corneas. You'd be able to tell, for example, if the cornea was the cause of glare-and-halo complaints. Standard placido disk topography can also show you how well you're centering your laser.

50 to 100 LASIKs per month. If this level of LASIK is your goal, I recommend that you invest in an advanced topography unit like the Orbscan. With volume in this range, you have a higher chance of running into cases that require that level of technology.

With these types of units, in addition to collecting elevation data, you can assess whether a patient's astigmatism is irregular. You can also assess pachymetry across the entire cornea, picking up subtle variations in thickness, which might alter your surgical plan. In some cases you might elect to perform a surface ablation rather than LASIK with a flap, for example. Or, if you have access to more than one type of laser, you might use a different laser that removes less tissue or more tissue in certain areas. Pancorneal pachymetry will also tell you whether the corneal apex is well-centered.

You might advise a patient in any of those situations to hold off on having LASIK until custom ablation is approved. If they still want to proceed, you at least have the information you need to educate them on what to expect from their procedure.

100 or more LASIKs per month. Not many doctors are performing this many procedures, but if that's your goal, you should purchase a wavefront device now.

At this level, you're obviously screening patients for current treatments, but you're most likely also screening them for future custom ablation treatments. Therefore, to advise properly on whether to have LASIK now or wait, and what to expect either way, you have to know the extent of their higher-order aberrations, which only an aberrometer can tell you.

Also, if you perform 100 or more LASIKs per month, it probably means you take referrals of difficult cases: post-LASIK patients whose surgeons can't explain why they don't see better. In these cases, you need to know whether the problem is corneal or retinal, and wavefront devices can tell you.

How I use today's advanced vision testing

I've tested most of the topography and wavefront devices in use today, and I use advanced topography (the Orbscan) and wavefront (I have several units.) in every LASIK case, pre- and postoperatively.

Each provides valuable information. The Orbscan gives me a view of the total shape of the cornea: front-surface curvature, back-surface curvature, and thickness. Wavefront gives me the shape of the entire optical system. I correlate the two to determine why patients who've had LASIK are having vision complaints, whether those complaints are due to corneal or retinal causes, whether today's technology can fix their problems, and whether patients who want to have LASIK would be better off waiting for custom ablation approval or undergoing a different procedure.

Advanced topography and wavefront also help me to determine whether I can perform an enhancement on a patient, whether he should wait for phakic IOLs or custom ablation, or whether he should have, say, a CK or Intacs enhancement to LASIK rather than more ablation.

The information is reassuring for patients, too. Take, for example, a post-LASIK patient who refracts close to plano without a lot of residual nearsightedness, farsightedness or astigmatism and whose flap looks perfect, yet he has significant visual symptoms like poor night vision, diplopia or poor contrast. If his symptoms match his wavefront, I can explain that there is a reason for his problems, higher-order aberrations. And I'm able to tell him that I can eventually fix those problems.

Being able to make those types of determinations is key for any surgeon who wants to provide LASIK at the highest level. With advanced vision testing, we improve in all three crucial aspects of LASIK: pre-op screening, surgical planning and post-op management.

Dr. Durrie heads the refractive surgery team for Hunkeler Eye Centers in Overland Park, Kan. He has more than 20 years of experience performing refractive and corneal surgery, and he trains surgeons from around the world on new surgical techniques.