Intraocular lens calculation accuracy limits in normal eyes

Abstract

The need to individualize and fudge parameters decreases with better physical models of the pseudophakic eye. Further improvements are possible by individual topography to extract corneal asphericity and measured pupil size to calculate the best focus, by improved position predictions based on individual measurements of the crystalline lens and by smaller tolerances for IOL manufacturing.

Optimizing intraocular lens power calculations in eyes with axial lengths above 25.0 mm

“…8 Using this higher group refractive index of 1.3616 in our data set, the magnitude of the hyperopic outcome was reduced by only a few percentage points (data not shown). In a study by Preußner et al, 15 the following equation was used to transform the AL values given by the IOLMaster: Transformed AL Z 0.9479 Â IOLMaster AL C 1.0848. This transformation gave zero prediction error and zero steepness of the regression line fitted to the prediction error for a collective of 189 eyes.…”

Ray-tracing intraocular lens power calculation using anterior segment optical coherence tomography measurements

“…Systematic differences between the MRSE at 5 m and at infinity were not corrected in the same manner as in previous studies 5,7 since it cannot influence the comparison of 3 methods. The refractive error was evaluated using 1-way analysis of variance after the equality of variances was verified using the Bartlett test.…”

“…2 Use of optical coherence interferometry facilitates easy and reliable measurement of the AL with high accuracy. 3 With third-generation calculations, such as the SRK/T formula, 4 sufficient accuracy can be achieved in most patients with monofocal IOLs, 5,6 whereas the refractive error increases in eyes with an abnormal AL 6,7 or corneal profile. 8 Ray tracing, the gold standard in lens and optical system designs, is a straightforward and promising approach in IOL power calculation.…”

Effect of corneal aberrations on intraocular lens power calculations

“…Preussner et al 24 propose the use of nonparaxial ray-tracing procedures for IOL power calculations, showing the importance of corneal asphericity. This was confirmed in a large-population study 25 in which the mean anterior corneal eccentricity values were used. In a further step in this direction, personalized corneal eccentricities, calculated from the anterior corneal topography, were introduced into the nonparaxial ray-tracing procedure, 26 showing their influence in the calculation, especially in post-LASIK eyes.…”