Shpak G. Intraocular lens power calculation optimization

This thesis was devoted to intraocular length power calculation problem and the main factors, causing such calculating difficulties, in patients after phacoemulsification of cataract and IOL implantation in the bag. For such purpose the method of intraoperative IOL power calculation was invented (e.g. Declarational patent №19822 UA А61Е9/013 of September 15th 2004 Journal №9.). It is established that all modern intraocular length power calculation formulas have a definite preciseness of calculation (deviation of target refraction is from +0,35 ± 0,32 D to +59 ± 0,41 D). During computer tests it became obvious that for AL > 22,5 mm eyes the minimum deviation of target refraction is ±0,25D, it was achieved through the best formula - SRK/T and for AL < 22,5 mm eyes the minimum deviation of target refraction is ±0,25D, it was achieved implementing Hoffer-Q formula. It was determined in the lab that aphackic refraction during phacoemulsification is dependent of intraocular pressure. Intraocular pressure in the frame of 19.0 to 30.0 mm Hg (250-400 mm of water scale) is optimal for measuring aphackic refraction during the surgery of phacoemulsification. It has been determined that the well known method of intraoperative calculation is less precise comparing with the method of preoperative beometry data. The optimized method of intraoperative intraocular length power calculation in the standard environment allows to achieve the preciseness of target refraction with error of +0,23 ± 0,36 D of artiphacic eye, that equals the interferometry data received from the operating computerized IOL Master. In irregular situations such as keratorefractive procedures (LASIC, PRK, RK) optimized method of intraocular length power calculation with coefficient К' 1,94 can be used as a controlling method or as an alternative of preoparative calculation. On the eyes filled with silicon oil, the optimized method of intraoperative calculation can be successfully used as the main one, especially on the eyes with impossibility of determination of axial length of the eye.Taking into consideration everything discussed above and the presence of all necessary conditions of implementation, the intraoparative method of calculation can be used independently, as separate, recommended method of calculation in the standard and nonstandard situations, that comply with up-to-day standards of getting target refraction according to formulas. It can be implemented during the facoemulsification of the cataract with the IOL implantation as a certain stage of the eye surgery.