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Laser Extraction of Hard Cataract using a New «Racot» Machine based on 1.44 mcm Nd:YAG Laser
Andreyev Y. V., Kopayeva V. G., Belikov A.,
The S. Fjodorov State Institut "Eye Microsurgery Complex" (Moscow)
The purpose of this paper is to evaluate clinical results of laser cataract extraction for hard cataract using a new «RACOT» machine created by the Institute of Fine Mechanics and Optics, St.-Petersburg (US patent No.6,322,557B1Nov.27,2001). The material of study includes 1500 operations performed from September 1997 to June 2001 which were divided into 2 groups. Group 1 (340 cases) included 292 mature and 48 brunescent cataracts with hardness 3-5. Group 2 (1160 cases) included 1036 mature and 124 brunescent cataract with hardness 3-5. The patients age was 71±7.1 years. The constructed machine included Nd:YAG laser with 1.44 mcm wavelength, cumulated with aspiration pump. Two separate special designed tips laser and irrigation-aspiration were used. Surgical technique. 2 corneal incisions were performed, 2.5 mm for the irrigation-aspiration tip and 0.8 mm for the laser tip. After capsulorhexis and hydrodissection the nucleus was destroyed with bowl and division into fragments technique. In group 1 we used the energy of pulses 100 mJ (vacuum 40 mm Hg) for bowl formation and 80 mJ (vacuum 150 mm Hg) for fragments aspiration. 1% methylcellulose was used. In the group 2 we increased pulse energy to 180 mJ during bowl formation and to 120 mJ for fragments aspiration. It simplified surgical maneuvers and made more controllable fragments removal. After 340 performed surgeries, the thin silicone plate on irrigation-aspiration tip to protect posterior capsule was additionally used. It was inserted under fragments to prevent posterior capsule suction. Also more stable viscoelastic 3% methylcellulose began using to prevent washing out viscoelastic layer from anterior chamber. In group 1 complete cataract removal (lens destroying and aspiration) lasted 7.2±3.8 min. In no case a transfer to ultrasound phacoemulsification was used. In group 2 the time of operation decreased to 3.2±1.8 min. The cases of posterior capsule rupture decreased from 42 (12.5%) in group 1 to 11 (0.9%) in group 2, only 2 cases of capsule rupture occurring in the last 860 operations. In group 1 corneal edema was noted at 1-3 day in 94 (27.6 %) cases. In group 2: 28 (9.3%) cases of corneal edema were observed in the first 300 operations, during subsequent 860 operations cornea maintained clear. 8 (2.3%) cases of IOP elevation up to 28 mm Hg at 1-6 days were observed in group 1, and only 2 (0.1%) cases in group 2. The BCVA 0.7-1.0 was achieved in 1230 (82%) cases. In the long-term period no complications were revealed which could be explained by to the negative effect of laser energy on ocular tissues. The results proved a possibility to remove hard and brunescent cataracts with the application of a new laser unit. The maximum safety of operation could be reached using optimized energy parameters (180 mJ to bowl formation and 120 mJ to fragments aspiration), protective silicone plate and thoroughly control of viscoelastic location in anterior chamber.