Article Date: 12/1/2004

Wavefront Technology Comes Of Age
Aberrometry has taken on new importance as clinicians find new diagnostic applications.
By Louis J. Catania, O.D., F.A.A.O.

Colleagues no longer ask me, "Should I get into wavefront?" Today, the question is, "What type of wavefront is best for my practice?"

The question is certainly valid. Far from being limited to guiding custom ablation in refractive surgery, wavefront technology is redefining our diagnostic and prescribing capabilities.

The Marco 3-D Wave* aberrometer offers these features, and I've been involved in several studies of its diagnostic capabilities. This technology is giving us information we never had before, which means we now can address problems we never could before.

In our practice, we find the system essential for quite a few nonsurgical applications. Here are the top six.

Look for Versatility

Versatility is an important consideration when adding any new technology, and you're going to want an aberrometer that does a lot for you.

At Nicolitz Eye Consultants in Jacksonville, Fla., we use the Marco 3-D Wave for all of our in-office diagnostic work. It gives us the total power of the eye and identifies higher-order aberrations, individual aberrations and internal optical path differential (the separate power of the lens). It's also an autorefractor and a corneal topographer.

1. Evaluating eyes not correctable to 20/20.

Many of us have lost sleep over eyes that don't correct to 20/20. We do all the tests -- visual fields, optical coherence tomography, Heidelberg retinal tomography -- but we can't find a thing. When we do some root mean square (RMS) values, we often find that problems with higher-order aberrations are degrading a patient's vision.

2. Assessing static vs. dynamic vision differences.

If we just measure a patient's distance vision and add on +2.00D for near vision without taking cylinder into account, the result may be less than desirable because the cylinder at near can change more than the plus. A patient with a significant cylinder shift might benefit from a separate pair of reading glasses for near work.

3. Determining the best lenses for contact lens candidates.

Soft contact lenses may not be the best modality for a patient with significant coma coming off the cornea. A better choice might be a gas permeable lens, which can neutralize some of that coma coming through the front surface of the lens.

Speaking of contact lenses, Penny Asbell, M.D., and I are comparing patients undergoing corneal refractive therapy (CRT) to patients who've had conventional LASIK. We plan to evaluate patients at 3, 6 and 12 months.

Thus far, at 3 months, Dr. Asbell has found the CRT technology keeps aberrations lower than conventional LASIK does. I should point out two important facts, however: First, we have not yet started a custom LASIK cohort, which may yield different results. And second, the "sweet spot" for LASIK usually occurs at 6 months.

 

Initial Reaction From a New User

 

Peter Van Hoven, O.D., vice president of Primary Eye Care Group in Brentwood, Tenn., has been using the Marco 3-D Wave for about 6 months. "The 3-D Wave gives a great deal of information and helps us find answers to problems that sometimes don't make sense," he says.

Dr. Van Hoven and his colleagues use the 3-D Wave on every patient for autorefraction, topography and wavefront analysis, integrating it into their Epic 2100 system. They find it particularly useful for complex contact lens cases. "On a few cases, I've used the 3-D Wave to download topographies and e-mail them to contact lens designers," he says. "They can then view and manipulate the data real-time and successfully manufacture a contact lens for the patient."

4. Identifying dry eye.

Just as dry eye distorts topography maps, it distorts power maps as well. So, basically, the aberrometer is another tool we can use to help us identify dry eye.

5. Examining post-blink tear instability relative to refractive surgery.

A recent study1 identified a two- to five-fold increase in higher-order aberrations post-blink at about a 15-second blink. Researchers concluded that refractive surgeons should measure post-blink time before they measure aberrations.

I studied more than 20 patients at 10 seconds and found that, indeed, the higher-order aberrations dramatically increased, but of significant interest, the lower-order aberrations changed, as well. This means that if a patient with no vision problems complains she can't see clearly, wavefront readings taken immediately after a blink and 8 to 10 seconds later can show the RMS value change that's causing her blur.

We've just begun a larger study to determine associated parameters (age, sex, medications, etc.) and the potential benefits of artificial tears.

6. Judging corneal aberrations secondary to certain lid and ocular pathologies.

Our practice includes an oculoplastic surgeon, and we've been doing aberrometry before and after blepharoplasty for ptosis. Preoperatively, every patient shows vertical coma from the pressure of the upper lid (minus on top, plus on the bottom). One month post-op, it's gone. Bleph-aroptosis and any other lid condition that presses on the cornea will likely create visual aberrations -- we found a 77% to 96% increase in vertical coma. This is compelling information that we've been able to gather.

Future implications

Wavefront technology isn't limited to guiding corneal laser custom ablations. We can perform routine refractions, evaluate the impact of tear film on vision, understand refractive problems, determine the best contact lenses for a patient, assess ocular surface disorders, and monitor refractive surgery patients. I'm certain the implications of this technology will be far-reaching.

 

This patient was pre-op for bilateral blepharoplasty to correct lid ptosis. Initial testing with the 3-D Wave revealed asymmetric inferior astigmatism and increased RMS values. The lid position was grossly abnormal as demonstrated by the eye image overlay.  This patient is 1 month post-op for blepharoplasty. The appearance of the lids is normal, and cosmetically, the patient was very pleased. Also, the patient reported vision quality was much better than before the surgery. The 3-D Wave revealed the patient had minimal corneal astigmatism and dramatically reduced higher-order aberrations as noted on the graph. This demonstrates the effect the lid has on the cornea over time.

*The 3-D Wave is manufactured by Nidek for Marco.2-S

1. Koh S, Maeda N, Kuroda T, et al. Effect of tear film break-up on higher-order aberrations measured with wavefront sensor. Am J Ophthalmol. 2002 Jul;134(1):115-117

 


Optometric Management, Issue: December 2004