Intrastromal treatment optimal for patients with mild hyperopia, has strict indications
Flapless intrastromal correction of presbyopia (IntraCor) with a femtosecond laser (Femtec 520F, Technolas Perfect Vision) provides good presbyopic correction with slight decreases in distance vision. However, the indications for the monovision procedure are strict and it provides the optimal results in patients with mild hyperopia.
Dr Erik L. Mertens, FEBOphth, presented his findings at the annual meeting of the American Society of Cataract and Refractive Surgery.
The femtosecond laser is an 80KHz device. When performing the presbyopia treatment, 40 KHz is used. Using this procedure, five microscopic, concentric ring patterns are created in the stroma that alter the corneal curvature and correct presbyopia. The creation of three and six rings is being investigated but is not yet approved. Currently, one eye is treated at a time, and the nondominant eye is treated first, explained Dr Mertens.
Immediately postoperatively, air bubbles are visible in the cornea and almost resolve by 2 hours after the procedure; by 1 month postoperatively the effects of the procedure are barely visible. Dr Mertens showed on optical coherence tomography images that there is a safety zone between Descemet's membrane and the area treated with the procedure.
Probably the most important aspect of this procedure is centration. Topographic evaluation shows central steepening that, according to Dr Mertens, works very well, when the treatment is well centred.
"With this procedure, centration is extremely important," he said.
In Dr Merten's hands, this procedure is best performed in patients who have refractive errors of +0.5 to +1.25 D. When he initially treated patients who had plano presbyopia, the patients were unhappy postoperatively with the slight myopic shift and resultant mild loss of their distance visual acuity. After the surgery, patients who had mild hyperopia had some glare and halos, and some patients developed dry eye, but these may not be related to the procedure.