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E Valas Teuma, Craig Smith; CORNEAL INCISION DEPTH ACCURACY STUDY FOR THE LENSAR LASER SYSTEM. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3946.
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© ARVO (1962-2015); The Authors (2016-present)
The LENSAR Laser System (LLS) is a femtosecond laser assisted cataract surgery (FLACS) device. In addition to standard capsulotomy and lens fragmentation, the LLS also provide full thickness clear corneal incisions (CCI) and partial thickness arcuate incisions (AI). This study assesses the accuracy of the corneal incision depth produced by the LLS in an animal model.
Surgery was performed on 27 porcine eyes on three different serial number systems. A full procedure was performed on each eye including suction, docking, biometric scan and a full surgical procedure containing a capsulotomy, lens fragmentation, two 3-plane CCI and two 45-degree AI. Three incision depth modes for the AI were studied: fixed depth, percentage depth and fixed residual stroma. Two CCI depths were studied for the CCI: 50% depth and 30% depth for tunnel start point. Upon completion of each surgery each eye was immediately measured using an OCT system (OptoVue RTVue-100/CA).
For 600μm fixed depth incisions the depth was measured to be 603 ± 27 (SD). For 80% depth incisions the depth was measured to be 79.8% ± 2.06 (SD). The average corneal thickness at the incision point was 927μm, making the standard deviation of the incision depth 19.1μm. For incisions intended to provide a fixed residual stroma bed of 125μm, the results were 137.5 ± 13.0 (SD). For this mode the standard deviation was half that of the fixed depth mode; a significant difference (P<0.001).<br /> For CCI incisions with mid-plane tunnels intended to be at 50% cornea depth at the entrance and mid-point, the resulting depth was 45.2% ± 4.42 (SD). For CCI incisions with the mid-plane tunnels intended to be 30% depth at the entrance and 50% depth at the mid-point, the resulting depth at the entrance was 31.8% ±2.95(SD), and at the mid-point measured 48.4% ± 2.67(SD).
The LLS provides accurate and repeatable incisions depth regardless of incision mode; below a level where refractive outcome variance would be observed. The fixed residual depth mode provided the highest accuracy in this study, due to the consistent edge contrast seen in the Scheimpflug images of the cornea posterior surface. Fresh porcine eyes may show variable amounts of necrosis in the epithelial cells, resulting in inconsistent transparency and significant variance in light scattering off the anterior surface, impacting measurement accuracy.
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