Abstract
Vitreoretinal surgery is performed using mechanical dissection that sometimes results in iatrogenic complications, including vitreous hemorrhage, retinal breaks, incomplete membrane delamination, retinal distortion, microscopic damage, etc. An ultraprecise laser probe would be an ideal tool for cutting away pathologic membranes; however, the depth of surgery should be precisely controlled to protect the sensitive underlying retina. The ultraprecise surgical microprobe formed by chains of dielectric spheres for use with the erbium:YAG laser source (λ=2940 nm), with extremely short optical penetration depth in tissue, was optimized. Numerical modeling demonstrated a potential advantage of five-sphere focusing chains of sapphire spheres with index n=1.71 for ablating the tissue with self-limited depth around 10 to 20 μm. Novel detachable microsphere scalpel tips formed by chains of 300 μm sapphire (or ruby) spheres were tested on ophthalmic tissues, ex vivo. Detachable scalpel tips could allow for reusability of expensive mid-infrared trunk fibers between procedures, and offer more surgical customization by interchanging various scalpel tip configurations. An innovative method for aiming beam integration into the microsphere scalpel to improve the illumination of the surgical site was also shown. Single Er:YAG pulses of 0.2 mJ and 75-μs duration produced ablation craters in cornea epithelium for one, three, and five sphere structures with the latter generating the smallest crater depth (10 μm) with the least amount of thermal damage depth (30 μm). Detachable microsphere laser scalpel tips may allow surgeons better precision and safety compared to mechanical scalpels when operating on delicate or sensitive areas like the retina.
Highlights
As of 2004, 4.1 million people in the United States suffered some form of diabetic retinopathy, and that number has steadily increased each year.[1]
The sphere chain was placed in front of the hollow waveguides (HWGs) with the inner and outer diameters of 300 and 750 μm, respectively, and both were secured together inside a thin-wall polyimide tube (B000PHAI3M, Amazon Supply, Seattle, Washington, USA)
Three, and five sphere structures of identical sphere size were tested and since each sphere chain configuration attenuated the energy differently, attenuation of the laser output was adjusted to normalize each configuration to an incident energy of ∼0.2 mJ on the tissue surface
Summary
As of 2004, 4.1 million people in the United States suffered some form of diabetic retinopathy, and that number has steadily increased each year.[1] The current surgical procedure for proliferative diabetic retinopathy requires the tedious use of steel instruments to remove deposits off of the retina.[2] The tools access the vitreous cavity and pathologic fibrovascular tissue on the retinal surface through the pars plana. Removal of the fibrovascular membranes from the retina is the most important yet most tedious aspect of vitreoretinal surgery. Retinal membranes are segmented using a combination of automated vitreous cutters, membrane peeling and cutting scissors, and manual scissors. Delamination with forceps or scraping with picks or creating space between the membrane and retina for mechanical segmentation all stress the retina, increasing the risk for retinal tear or other damage
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