Six Months Follow-Up Results in Minipigs for Fs-Laser Presbyopia Treatment

Abstract

Purpose: : To investigate whether fs-laser in-vivo treatment of the crystalline lens causes cataract or unexpected changes in lens structure.

Methods: : Ten Ellegaard Göttingen Minipigs® underwent fs-laser treatment to investigate possible changes in the crystalline lens. The pigs were middle-aged (about 5 years) to assure that the lenses exhibited a sclerotic nucleus. The laser structures covered a volume of 5 x 5 x 3.5 mm, centered within the lens. Three pigs were laser structured slightly above the threshold for treatment, while the remainder were treated with about twice the pulse energy of the threshold. The pulse duration was 400 fs at a repetition rate of 200 kHz.The follow-up was performed by slit-lamp examinations applying the LOCS III method. Lens opacity was quantitatively characterized by means of Scheimpflug images. Follow-ups have been done 1 week, 1 month, 3 months and 6 months after laser surgery. In a pilot trial a histology was performed on the lens and retina of one species by means of HE-staining.

Results: : Even 6 months after surgery no cataract has been induced. Slit lamp and Scheimpflug images did not show changes in crystalline lens structure. Laser spots are still clearly visible. No changes of crystalline lens tissue around laser spots can be found. Histology revealed proper laser cuts within the lens and no apparent damage of the retina.

Conclusions: : Fs-laser surgery for possible presbyopia treatment does not induce cataract in pigs 6 months after surgery. Laser structure in lens has not changed during the past 6 months. Since the laser grid did not disappear 6 months after surgery even with low laser energy treatment, low energy might be sufficient to create permanent changes in crystalline lens structure.

Keywords: presbyopia • laser • cataract