Customized ablation creates larger optical zone for astigmatic patient

A collegiate baseball player was referred for refractive surgery and treated with the Visx CustomVue system.

Issue: September 1, 2005

ByByron A. Stratas, MD, FACS

A college baseball player was referred to me for refractive surgery. Having never been successful with contact lenses, he wanted to be able to play baseball without having to wear glasses.

Byron A. Stratas

This 22-year-old varsity athlete proved to be an interesting case. His preoperative manifest refraction was primarily astigmatism, –0.35 –1.50 × 110 in the right eye with best corrected visual acuity of 20/20 and –0.75 –1.25 × 72 in the left eye with BCVA of 20/15. He had large, 8+ mm pupils in dim illumination.

There was nothing remarkable about the patient’s preoperative Orbscan, wavefront maps or RMS error. While there is debate about the relevance of RMS values, the point-spread function maps seem to be more descriptive.

With a conventional LASIK ablation, someone like this baseball player is at risk for significant night vision problems. With low sphere but more than 1 D of astigmatism, the laser does not allow a blend zone out to 8 mm. Even with a 6.5-mm optical zone, the minor axis of a conventional treatment could be as small as 4.5 mm, since the optical zone size only refers to the major axis.

Preop WaveScan data (OD).

Images: Stratas BA

Preop WaveScan data (OS).

Treatment

Fortunately, I was able to offer the patient a custom procedure, something I now recommend for anyone who is within parameters approved by the Food and Drug Administration. When an individual falls outside the parameters, I still feel compelled to tell them about wavefront and explain that the FDA is considering expanding the approval in the future.

A wavefront-guided procedure creates a different ablation shape than a conventional procedure. On the Visx CustomVue system (Advanced Medical Optics), the optical zone size refers to the minor axis, an important change from the conventional system that benefits patients like this one. In this case, for example, the CustomVue system created an optical zone of 6.7 × 6 mm with a blend zone that extends the treatment to 8 mm. The surgery was conducted using thin flaps and a CustomVue ablation without complication.

At the 6-week postoperative visit, the patient claimed he could see the laces on the baseball as it rotated toward him when he was at bat. Being able to see the laces and how they are spinning tells him what kind of pitch it is. He said he was not able to see like that while wearing his glasses. He also claimed to see as well at night as during the day, a significant subjective observation considering his large pupils.

This patient was thrilled with his outcome. Objectively, his vision was 20/15 uncorrected in both eyes, so he gained a line of vision in the right eye. This ballplayer had batted .600 in his college playoffs before the surgery, and he is now visually well-equipped to continue with his career.

Not every patient has such a memorable outcome, but overall I have been pleased with our CustomVue results and think the procedure is the state of the art in laser keratorefractive surgery today.

Tips for success with custom ablation

Consider doing your own WaveScan assessments. In our practice, the surgeon performs or evaluates the wavefront exam and personally calculates the CustomVue treatment plan. We have continued not to delegate those aspects of planning the treatment, primarily because we still learn a great deal from doing it ourselves.

Check your alignment. We now use iris registration to automatically cyclo-orient our ablations with the Visx S4 IR. At the time of this case, we manually marked the eye. I mark the 180° horizontal meridian with a new sterile skin marker and then check with a level to make sure the marks are exactly horizontal. We have the patient lie down under the laser and orient him so the marks are aligned with the reticles before stabilizing his head into position. When attempting to correct fine detail, it is important to ensure that the treatment is placed exactly where it should be relative to the wavefront measurements. In the future, I anticipate automated iris registration will help with this process.

Consider a thin flap. I use the IntraLase to create 100 µm to 125 µm flaps. At the time of this case, I used a Moria Carriazo-Barraquer microkeratome and routinely created 100-µm to 130-µm flaps because they preserve the most tissue. Considering that the epithelium is, on average, 55 µm deep and Bowman’s membrane is about 10 µm deep, we are using only 35 µm to 65 µm of stromal tissue with a thin flap. I think this approach offers the tissue-preservation advantages of surface ablation without the disadvantages. I am a big advocate of the quick recovery of LASIK and the ability to lift the flap later to enhance, if needed.

Create a consistent operating environment. We maintain a tight temperature and humidity range in the operating room, with a temperature of 70° and humidity of 44% with a dedicated Liebert Challenger 3000 HVAC system, manufactured by Emerson.

Source: Stratas BA

For Your Information

Byron A. Stratas, MD, FACS, is medical director of The LASIK Center at Eye Associates of Wilmington in Wilmington, N.C. He can be reached at 1729 New Hanover Medical Park Drive, Wilmington, NC 28403; 910-763-3601. Dr. Stratas has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.

Advanced Medical Optics, can be reached at 3400 Central Expressway, Santa Clara, CA 95051-7122; 408-733-2020; fax: 408-773-7278; Web site: www.visx.com.