Abstract
Purpose: :
To study the morphologic features of femtosecond arcuate incisions.
Methods: :
Using an artificial anterior chamber pressurized with Optisol through an IV, we compared a freehand diamond blade vs 150 kHz femtosecond laser (FS). The penetrating incisions were created through Bowman’s layer (BL) in 8 NZW rabbits and wound healing was followed for up to 47 days postop. Intrastromal vs penetrating incisions (freehand or Hanna Arcutome Diamond) were also evaluated in 31 rabbits and in 18 human cadaver eyes in a zero time model experiment. Factors studied were optical zone diameter (6-8 mm), incision arc length (600, 750, 900), incision depth (penetrating or 100 um below BL and 100 um above Descemet’s Membrane (DM), side cut angle (900 or 300), laser raster energy (1.8 or 2.1 uJ), and laser spot and line (S/L) separation (3 x 3 um to 7 x 7 um). Spectral domain OCT was performed immediately after the procedures. The corneas were subsequently fixed in glutaraldehyde or formalin and prepared for LM, SEM, and TEM.
Results: :
Rabbit Study: no difference in the LM comparing different incisions, whereas there were no epithelial changes over the intrastromal wounds vs an epithelial plug in the penetrating wounds postop. Eye Bank: With penetrating incisions, no differences in epithelial damage using blades vs FS whereas the stroma was more sharply cut with the FS. The intrastromal incisions had no epithelial, BL or DM changes with a single gas bubble unless a S/L of > 4 x 4 was used; 6 x 6 and 7 x 7 produced tissue bridges and separate bubbles. Similar singular intrastromal gas bubbles were seen with OCT using 1.8 uJ and a S/L of 4 x 4 um. No penetration of either side of the corneas occurred in any model. Achieved depths below BL and above DM were measured as attempted.
Conclusions: :
The FS laser created a single, intrastromal incision unlike a free hand or mechanical diamond blade incision. No morphologic changes were detected above and below the intrastromal incisions. Benefits include decreased risk of infection, no epithelial plug formation, and no need for topical antibiotics. OCT features were similar across all studies. Advantages over diamond blades include predictability of incision depth, arc length, and ability to modify side cut angle.
Keywords: cataract • clinical laboratory testing