Purpose:
We have previously shown that subscleral drainage channels can be created with a femtosecond laser in ex vivo human and rabbit eyes by scanning in rectangular raster pattern [1, 2]. We now present results demonstrating that a subscleral drainage channel can be created in vivo in the rabbit eye with subsequent reduction in IOP.
Methods:
A femtosecond laser beam tuned to a 1.7 µm wavelength was expanded and focused through 0.5 NA aspheric lens (Thorlabs; Newton, NJ) as shown in Fig. 1. The rectangular raster pattern was programmed to create a 450µm (width) × 150µm (length) channel, as shown in Fig. 2, with scan parameters being a 3 µm spot separation, a 5 µm line separation, and a 3 µm layer separation. The scan started by moving the lens with a translational stage controlled by step motors (Newport Corp., Irvine, CA) at the posterior surface of the sclera in the angle of the eye and ended just below the anterior scleral surface. After creation of the channels the eyes were monitored using OCT imaging. The effect of the channel was also evalauted by measuring IOP before and after the laser treatment.
Results:
Fig. 3 shows an OCT image of a channel created with a very thin scleral layer preserved between the top of the channel and the anterior surface of the sclera. In this eye, IOP was reduced from 14mmHg pre-operatively to 8mmHg immediately following the creation of channel.
Conclusions:
A precise subscleral drainage channel can be created in vivo in the rabbit using an ab externa approach and a 1.7 µm femtosecond laser, resulting in a measureable reduction in IOP. A similar approach adapted to the human eye has significant potential in the treatment of glaucoma.
Keywords: intraocular pressure • laser • refractive surgery