Results from 2 years of follow-up in a study of presbyopia correction with femtosecond laser intrastromal correction show continued safety, refractive stability, and maintenance of improvements in near visual acuity.
"This is a quick procedure with a rapid and painless recovery, and patients are benefiting on average with a 4- to 5-line gain in uncorrected near visual acuity (UCNVA) as well as some improvement in intermediate vision," said Prof. Holzer, professor and director, refractive surgery, International Vision Correction Research Centre (IVCRC), Department of Ophthalmology, University of Heidelberg, Germany. "We've not seen any refractive regression, corneal weakening, endothelial cell loss, or straylight disturbances, and this noninvasive procedure carries a very low risk for infections, which makes it a very attractive option for patients."
The intrastromal procedure is performed using a proprietary femtosecond laser (Technolas Femtosecond Workstation, Technolas Perfect Vision) to cut five consecutive cylindrical rings, beginning in the center of the cornea with a 1.8-mm diameter ring. The algorithm for determining the distances between the rings and the depth of the cuts is based on the refraction, keratometry, and pachymetry.
The working principle for the efficacy of the procedure for improving near vision is that the intrastromal cuts induce central steepening of the cornea. In addition, corneal asphericity becomes more negative, and wavefront aberrometry shows significant reductions in spherical aberration (4,0) after the procedure.
"In most patients, there is central steepening of up to +2.5 D," Prof. Holzer said.
The results reported by Prof. Holzer were from a subset of 25 patients treated at the IVCRC within the context of a multicenter European trial. The enrolled patients had a minimal near add of +2 D, were treated between July and September 2008, and per the ethics committee decision, had only the nondominant eye treated.
"The procedure can be done bilaterally, and at the 24-month follow-up visit, seven patients had already decided to have their second eye treated," Prof. Holzer said.
The 25 patients had a mean age of 56 years (range 47 to 67) and included 18 men. At enrollment they had a mean sphere of +0.75 D, mean cylinder of –0.33 D, and mean SE of +0.60 D. Mean logMAR uncorrected distance VA (UCDVA) was 0.11 and UCNVA was 0.7.
"It is important to note that these patients were slightly hyperopic," Prof. Holzer said. "The procedure causes a small myopic shift, which was about –0.4 D in this population. Therefore, the ideal candidate should be a little hyperopic so that there is not any significant loss of distance UCVA."