Comparison of contrast sensitivity and HOAs

October 1, 2013

Because patient expectations of post-surgery outcomes have, inevitably, increased, there is a requirement now for surgeons to offer optimized techniques to ensure patient satisfaction.

With continual technological advancements, updates in techniques and easier access to information, patient expectations of post-surgery outcomes have, inevitably, increased. Therefore, there is a requirement now for surgeons to offer optimized techniques to ensure patient satisfaction.

After corrective surgery for the treatment of myopia and astigmatism, it is common for patients to experience a reduction in their contrast sensitivity and an increase in higher-order aberrations (HOAs), which could affect the level of patient satisfaction. Paying particular attention to these two post-surgery issues, Professor Walter Sekundo (Department of Ophthalmology, Philipps-University of Marburg, Germany) and colleagues compared 1-year results of the refractive lenticule extraction (ReLEx) FLEX technique with wavefront optimized femto-LASIK.1

"The refractive results of ReLEx FLEX surgery were published prior to this paper by our group followed by other investigators. However, at the time, when this study was initiated no comparative data was available on HOA and contrast sensitivity," explained Prof. Sekundo when discussing the reasoning behind the study.

"This was quite straight forward," said Prof. Sekundo. "We performed standardized refraction, visual acuity, contrast sensitivity testing and measured HOA using WASCA aberrometer in matched groups who were operated on by a single surgeon."

The team looked at 44 eyes of 22 patients with spherical equivalent (SE) of –5.13 D who were treated with ReLEx flex and 50 eyes of 25 patients with SE of –5.42 D who underwent wavefront-optimized femto-LASIK. To perform the procedures, the team employed the VisuMax femtosecond laser system (Carl Zeiss Meditec, Jena, Germany) with a 200 kHz repetition rate and a MEL 80 Excimer Laser (Carl Zeiss Meditec) for femto-LASIK with aspheric ablation profiles.


"At one year the mean SE in the ReLEx group was –0.23 ± 0.35 D and in the Femto-LASIK group –0.15 ± 0.27 D," revealed Prof. Sekundo. He noted that an improvement in the mesopic contrast sensitivity was demonstrated in the ReLEx treated eyes, which improved from 1.49 and 0.99 to 1.54 and 1.1 at 12 and 18 cpd, respectively. In the Femto-LASIK group there was also an improvement but it was not as good as the ReLEx group. The numbers for the Femto-LASIK patients were pre-op 1.51 and 1.03 and after one year 1.54 and 1.06.

"We did not expect to find this improvement in mesopic contrast sensitivity after ReLEx FLEX compared to pre-op data! Indeed, we can consider this to be a good outcome, if the contrast sensitivity is not worsened by surgery," added Prof. Sekundo. "Additionally, we found that the HOAs after ReLEx increased from 0.15 to 0.23 μm and after Femto-LASIK from 0.175 to 0.320μm (p = 0.0023)."


"These excellent visual quality results combined with the further improvement of the procedure, in particular as ReLEx SMILE (small incision lenticule extraction) using 500 kHz VisuMax laser has popularised this procedure virtually within last 1–2 years, has meant there is an increase in patient demand for it," emphasized Prof. Sekundo. "The number of patients opting for ReLEx rises day-by-day. These patients do not want LASIK surgery and come to ReLEx surgeons for 'the new generation of laser refractive surgery'." In his opinion, this increase in patients opting for ReLEx over LASIK will, in return, push other manufacturers (apart from Carl zeiss Meditec, which holds the patent) to develop similar systems to be able to cope with the demand.

"Surgeons should not be afraid of this new procedure," concluded Prof. Sekundo. "ReLex, in particular the latest development via a small incision (ReLEx SMILE), has many advantages over LASIK and femto-LASIK. They should start to perform ReLEx by themselves in order to appreciate the long-term results."


1. J. Gertnere, I. Solomatin and W. Sekundo, Graefe's Arch. Clin. Exp. Ophthalmol., 2013;251(5):1437–1442.