Allegretto Wave

September 1, 2006

Ophthalmologists who perform refractive procedures today, often to the dismay of patients as well as the treating physicians, achieve less than optimal satisfactory results postoperatively in 5% to 25% of their patients. Residual refractive errors, overcorrection, as well as pre-existing irregular astigmatisms induced by small optical zones and/or decentred ablations are difficult to correct with standard treatments because of their irregular nature.

Ophthalmologists who perform refractive procedures today, often to the dismay of patients as well as the treating physicians, achieve less than optimal satisfactory results postoperatively in 5% to 25% of their patients. Residual refractive errors, overcorrection, as well as pre-existing irregular astigmatisms induced by small optical zones and/or decentred ablations are difficult to correct with standard treatments because of their irregular nature.

According to A. John Kanellopoulos, MD, these "problem" patients would clearly benefit more from a custom ablation. Dr Kanellopoulos is Clinical Associate Professor of the Department of Ophthalmology at New York University Medical School and Director of the LaserVision Institute in Athens, Greece. He presented the results of his study on such problem patients employing a topography-guided wavefront optimized Allegretto system (WaveLight Laser Technologie AG), and spoke of the very positive results attained when using this fine-tuned custom re-treatment system.

"Although the term customized treatment is usually used for wavefront-guided treatments, topography-guided ablation is also a form of customized ablation. However, instead of conforming treatment to the wavefront map, it uses the patient's topography height map as the basis for the treatment," he said.

Putting it to the test

In his prospective, non-comparative study, 27 eyes of 22 patients with a history of LASIK for myopia underwent topography-guided enhancement treatment with the Allegretto Wave excimer laser system. All patients included in the study had previous myopic or hyperopic laser surgery and were dissatisfied with their quality of vision because they still had residual myopia, hyperopia, or mixed astigmatism. Indications included small original optical zone, decentred ablation, irregular astigmatism, as well as night vision problems. Pre- and postoperative evaluations of the study patients were recorded including refraction, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), corneal asphericity (Q value), low contrast sensitivity, scotopic pupil size, topography with the Orbscan II (Bausch & Lomb) and with the Wavelight Topolyzer (yielding the topography height maps), ultrasound corneal pachymetry with the NIDEK US-1800, as well as the patient's subjective assessment of improvement. Patients were evaluated one hour, one day, one week, one month, three months and six months post-procedure.

Results showed that, at the six-month follow-up exams, the mean UCVA improved from 20/49±0.22 to 20/25±0.21 and the mean BSCVA improved from 20/32±0.15 to 20/21±0.14 in patients. The refractive error also improved from sphere of -0.84±1.37 D to -0.61±0.81 D, and cylinder of -0.55±0.78 D to -0.53±0.58 D. Corneal asphericity, as measured by the Q value, improved on average from +1.46±0.79 to +1.07±0.89. Dr Kanellopoulos noticed that the mean contrast sensitivity scores at 12 cycles/degree improved by 70% from a mean of 3.56±0.66 to 6.05±0.59. In the majority of cases, study patients reported an improvement of their symptoms postoperatively.

Why do we need it?

According to Dr Kanellopoulos, eyes with decentred and/or small optical zone ablations may suffer from irregularities in the corneal surface, which can dramatically affect the quality of vision in patients. Here, the cornea acts like a multifocal lens and causes uneven distributions of light. Subsequently, the eye loses BSCVA, contrast sensitivity, and experiences halos and starbursts around objects. These symptoms can be especially bothersome during scotopic and/or mesopic conditions when the pupil dilates and exposes more of the irregular cornea. Eye surgeons, therefore, opt to perform "customized" forms of ablations, including this technique of topography-guided treatments, as well as wavefront-guided ablations.