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Alexander Vankov, Phillip Gooding, Michael Wiltberger, Dave Dewey, Noah Bareket, Georg Schuele; Femtosecond Corneal Cut Quality as Function of IOP. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3128.
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Individual tissue effects created by singular femtosecond laser pulses should merge into a continuous cut to form a complete incision. This paper examines the corneal cut quality by femtosecond laser as a function of intraocular pressure (IOP).
The CATALYS ® System was used to create corneal incisions on fresh porcine eyes. Intraocular pressure was controlled by inserting a large volume needle and connecting with a water bottle raised to different height levels to enable constant and well controlled IOP throughout the experiment at 15, 30 and 60mmHg. The eyes were docked to the CATALYS ® System and regular cataract related corneal incisions performed. Standard corneal incisions parameters were used with the variation of 1 and 10 line density (factor of line to line spacing density). Immediately after exposure treated eyes were put into gluteraldehyde fixative to fix the tissue in its condition right after exposure. After 24 hours of fixation the corneas were treated with fixed stresses, separating places free of bridges. Cross-sectional cuts of the cornea were examined under the microscope. The percentage of remaining tissue bridges was evaluated.
We found that corneal cut quality depends on IOP. Density of the bridges on the anterior side of penetrating corneal incisions increases with the increase of the intraocular pressure. For line density of one no tissue bridges were found for 15mmHg while 12% & 18% of tissue bridges were found for IOP levels of 30 & 60mmHg respectively (Figure 1). These tissue bridges at higher IOP levels could be eliminated by increasing the line density to 10 (Figure 1). All data were statistically significant with respect to each other.
This is reports for the first time the observation that IOP has a significant effect on the quality of corneal cuts. Mechanical stress within the corneal tissue might be the leading contributor to explain the variability. Preservation of the good cut quality at all pressures levels requires increase of the laser spot density.
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