EyeWorld India June 2013 Issue

24 June 2013 EWAP FEAturE optimal for lens substance destruction, e.g., with 1.44 mcm Nd YAG laser. This is complete laser cataract surgery. From 1994 to 1997, the unique surgical technology of laser cataract extraction (LCE) was developed under the leadership of Prof. Svyatoslav Fyodorov, Eye Microsurgery Federal State Institution, Moscow, by a group of authors (V.G. Kopayeva, Y.V. Andreyev). This allows for the destruction of all types of nuclei, including the most dense cataracts without manual fragmentation. Pioneering laser machine “RAKOT” (NELA Company, St. Petersburg, Russia) has an Nd YAG laser with 1.44 mcm wavelength generating radiation in pulse-periodic regime with a 250 mcsec pulse duration, range of energy pulses 5-500 mJ, frequency 10-30 Hz, and a backing vacuum pump of original construction. Unlike other well-known types of irrigation/ aspiration systems, this has no need for occlusion as well as no need for a compressed air supply. This is a type of radiation never used before in medicine. Since 1997, after a series of experimental studies, LCE has been practiced in The S. Fyodorov Eye Microsurgery State Institution in Moscow and its 11 national branches at the territory of the Russian Federation; since 1998 it has been performed in other clinics in Russia, Ukraine, Kyrgyzstan, Uzbekistan, and Cyprus. The first 100 procedures were performed under the personal observation of Prof. Fyodorov. In 2008, the technology of laser cataract extraction was registered and approved by the Federal Service on Surveillance in Healthcare of the Russian Federation Government (#2008/263 – Nov. 26, 2008). The S. Fyodorov Eye Microsurgery State Institution possesses the most extensive experience worldwide in successful laser energy application in cataract surgery (in 2005 more than 20,000 surgeries were performed in the main clinic in Moscow). Long- standing practice is sufficient to make conclusions on this technology. In our studies, we proved laser energy superiority over ultrasound in cataract surgery. Laser is two- to three-fold safer and more efficacious than ultrasound operating at any nucleus density, with no need in manual fragmentation. There are no restrictions in total intraocular time of laser work. Our technology is bimanual. The laser tip delivers energy. The irrigation/aspiration tip procures input and output of irrigating fluid and contains a series of original specifications never used before in cataract surgery. The aspiration tube is manufactured from the material transparent for both the surgeon’s eye and laser radiation, hence working parts are not damaged by the radiation and do not leave foreign microparticles inside the eye. Special processing of the aspirator’s walls provides a laser energy concentration effect inside the aspiration tip. Therefore, lens material is destroyed outside and inside the irrigation/aspiration tip. This prevents aspirator lumen obturation. Unlike other technologies of laser cataract surgery (1.06 mcm Nd YAG, 2.94 mcm Er YAG) our laser technology allows facilities to operate on any density nuclei without choppers and transition on ultrasound. The main advantage of 1.44 mcm Nd YAG laser compared to ultrasound phacoemulsification is its safety for intraocular structures surrounding the lens. This can be explained by fundamental physical properties of the laser radiation, as well as the surgical technique of LCE. During laser operation we use maximal parameters of the laser for destruction of the most central and dense part of the nucleus (stage of crater formation). When forming the central crater-like defect the wide ridge of lens periphery stays intact and preserves the natural shape of the capsular bag, thus excluding posterior capsule motility and tractions of ciliary processes. Iris and ciliary body are also spared. The surgery itself has brought a new level of safety and efficacy. When operating on the peripheral less dense part of the nucleus, we decrease laser energy twice. Epinucleus with 1.5-3.0 mm width (depending on the age) is removed using vacuum only with no energy. According to physical properties of the 1.44 mcm Nd YAG laser water medium absorbs energy at the distance of 1-2 mm from the tip. Therefore during LCE surgery, energy does not reach ciliary processes surface even at the stage of nucleus peripheral part removal. The radiation is not capable of getting to the retina and beyond the eye via the wide water barrier. Laser radiation is characterized by coherence and monochromaticity (linearly directed), which excludes energy scattering. On the contrary, fluid is a perfect conductor for the ultrasound. Ultrasound spread zone is more than 30 mm. Ultrasound radiation is not well directed, it is dissipated at all directions; this circumstance is one of the main factors of damage. Contemporary ultrasound phaco machines are highly advanced due to extensive research and development efforts of the leading world manufacturers. Still it is not possible to exclude manual fragmentation of the nucleus as there is no way to change intrinsic physics of the ultrasound phacoemulsification technology. Laser pulse frequency is 30 pulses/sec. (30 Hz), ultrasound pulses frequency, 30,000-40,000/ sec. (30-40 kHz). This intrinsic physical property explains the phenomenon that during surgery the laser tip is not heated up as laser pulse momentum range hundreds fold surpasses pulse duration itself. The heat diffuses from the operational zone before the new energy portion is introduced. Even in the case of aspirator obturation there is no danger of corneal burn as well as no need to cool the tip by reverse fluid flow via the surgical wound. We plug surgical wounds tightly by the tips providing a complete seal of the eye during surgery. This leads to no pressure overfalls, anterior chamber depth is stable, there is no vacuum effect on the posterior segment of the eye, less influence on uveal microcirculation, less irrigation fluid consumption and side effects on corneal endothelium. OVD is better preserved inside the eye. One of the main advantages of LCE with 1.44 mcm Nd YAG laser is spontaneous formation of the nucleus cleavage and full destruction of the lens using laser energy only due to the mechanism of cluster brittle cracking and stratification of the lens substance. No other existing laser technology has such an effect. The ophthalmic laser machine “RAKOT” comprises two types of laser radiation. The 1.44 mcm Nd YAG laser destroys the lens. The second type of laser is low energy helium neon laser and acts as a red marker. It tints the invisible Nd YAG laser and exerts a positive biostimulating effect on eye tissues. Surgeons conducting LCE never mention postop inflammation. After LCE, the delicate process of cell repair regeneration is complete one month postop; after continued on page 27 Laser - from page 23