Probleme der Kunstlinsenberechnung nach photorefraktiver Keratektomie bei hoher Myopie

Abstract

After corneal refractive surgery, various techniques to determine the current corneal power should be compared and the value around which results tend to cluster should be relied on to avoid hyperopia after cataract surgery with lens implantation. In those cases where keratometry and refraction before PRK/LASIK are available, the gold standard is still to subtract the change of the SEQ at the corneal plane from the preoperative central keratometric power, although in the present case report the subtraction of 24 % of the SEQ change at the spectacle plane from the measured corneal power value seemed to produce the best result. Pure subtraction of the SEQ change at the spectacle plane from the corneal power value before refractive surgery has to be avoided in eyes with excessive myopia. The most reliable corrected power value should be inserted in more than one modern third-generation formula (such as Haigis, Hoffer Q, Holladay 2, SRK/T) and the highest power IOL should be implanted. In all instances, the cataract surgeon has to make sure that the corrected K-reading is not wrongly re-converted within the IOL power calculation formula used.

Reliability of a new correcting factor in calculating intraocular lens power after refractive corneal surgery

“…All the articles in English published through December 2003 were reviewed and were included if there were sufficient data to apply the R factor, CHM, and DKM. 7,[14][15][16][17] For this reason, the sample comprised only 19 eyes.…”

“…[1][2][3][4][5][6] For this reason, if a patient who had refractive surgery develops a cataract, using the actual K-readings with the current formulas, the power of the IOL will be underestimated and the patient will be at risk for hyperopia. [7][8][9][10][11][12][13][14][15][16][17][18][19][20] To overcome this problem, 3 main techniques have been proposed: historical methods (HM), contact lenses, and the so-called true corneal power method.…”

“…This method can be performed in patients for whom no preoperative refractive parameters are available, but unfortunately it is not reliable if media opacities result in visual acuity worse than 20/70. 27 The most precise method thus seems to be the HM, [14][15][16][17][18][19][20][21][22][23] but regrettably the necessary information is not available for most patients.…”

Intraocular lens calculation after refractive surgery for myopia: Haigis-L formula

“…In the past few years, increasing attention has been given to this problem. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Three main sources of error have been identified. 16 First, curvature measurements are erroneous because they are not obtained from the corneal center (radius error).…”

Vergleichende Ergebnisse der Hornhautbrechkraftbestimmung dreier Messgeräte nach LASIK

“…Ausschlusskriterien waren Voroperationen, chronische Augenerkrankungen, Augenentzündungen, Z. n. Hornhautverletzungen sowie Netzhauterkrankungen. [5,11,12].…”