Wavefront-guided treatment corrects night-visin problems

April 1, 2006

The results from subjective assessments of night-vision disturbance showed that 14 of the 16 eyes achieved an improvement of at least 60%.

Dr. Reinstein reported the results achieved in a series of 16 eyes of nine patients who were complaining of severe night-vision problems. The benefit of the repair procedure was demonstrated by subjective reports of symptom improvement, return of contrast sensitivity to normal levels, and reduction of spherical aberration. No patients lost any lines of best spectacle-corrected visual acuity (BSCVA).

Conventional treatment results

"This study was designed to evaluate the safety and efficacy of wavefront-guided enhancement for patients with night-vision complaints using the Carl Zeiss Meditec platform, but by including an unaffected control group, it sought to investigate what is a tolerable level of aberrations and to what extent aberrations need to be corrected in order to treat patients with night-vision disturbances successfully," said Dr. Reinstein, medical director, London Vision Clinic, London, England, and assistant professor in clinical ophthalmology, Weill Medical College of Cornell University, New York.

"The results indicate that eliminating spherical aberration is not a requirement for patients to be happy, and that has important clinical implications because it tells us we can save tissue as we plan these ablations," he said. "However, it was also extraordinary to find there were patients who underwent primary treatment with the MEL80 laser who actually benefited with improved contrast sensitivity. I am not aware of any other conventional (non-wavefront) laser treatment that has been associated with that type of result."

Prior to undergoing the wavefront enhancement, each of the case eyes was confirmed to have increased spherical aberration based on assessment with the WASCA aberrometer (Carl Zeiss Meditec). Patients with increases in other higher-order aberrations, decentered ablations, or other complications that would contribute to night-vision disturbances were excluded from the study. All of the eyes undergoing enhancement were also confirmed to have adequate stromal thickness based on measurements with 3D very high-frequency digital ultrasound (Artemis, Ultralink).

The results from subjective assessments of night-vision disturbance showed that 14 (88%) of the 16 eyes achieved an improvement of at least 60% and 12 (76%) benefited with an improvement of at least 80%. Contrast sensitivity was evaluated at four spatial frequencies (3, 6, 12, and 18 cpd) using the CSV-1000 (VectorVision). Those results showed statistically significant improvements in contrast sensitivity at all frequency levels tested as well as in the percentages of eyes with normal contrast sensitivity as analyzed using the Boxer-Wachler normalized contrast sensitivity ratio. Across the four spatial frequencies, contrast sensitivity was in the normal range among 6% to 38% of eyes prior to enhancement and in 75% to 88% of eyes after the wavefront-guided procedure.

Analysis of attempted versus achieved SE indicated the procedure had good refractive predictability-76% of eyes were within 0.50 D of attempted SE and 100% were ±1.00 D.