[Individualization of IOL constants for two hydrophobic intraocular lenses. SRK II, SRK/T, Hoffer-Q, Holladay 1 and...

The aim of the study was an assessment of refraction error after implantation of two types of hydrophobic acrylic intraocular lenses and derivation of customized IOL constants for the SRK II, SRK/T, Hoffer Q, Holladay 1 and Haigis formula.

The purpose of the present study was to analyze the refractive outcome of two hydrophobic acrylic intraocular lenses and to present a computerized calculation scheme for customization of lens-specific parameters provided by the lens manufacturers based on the refractive results of a surgeon or study center.

In this prospective monocentric study 100 consecutive cataract eyes were treated at the Eye Hospital of the Barmherzige Brüder (Compassionate Brothers) in Linz/Austria with a hydrophobic acrylic aspherical intraocular lens (Polytech Y10AS, n = 50) or a hydrophobic acrylic spherical intraocular lens (Hoya PC-60R, n = 50). The biometrical data were assessed preoperatively together with the refractive outcome 8-10 weeks after treatment in order to analyze the deviation of postoperative refraction (spherical equivalent) from target refraction (ΔREF) and to customize the lens constants for the SRK II, SRK/T, Hoffer Q, Holladay 1 and Haigis formula.

Based on this data set it could be demonstrated that using the lens constant provided by the manufacturer (ΔREF) the Polytech lens showed a systematic trend to myopia in contrast to the Hoya lens which ranged around zero. This trend could be compensated by selecting appropriate lens specific constants. For the Polytech/Hoya lens median lens constants of: A = 118.0/118.6 (SRK II), A = 117.9/118.6 (SRK/T), pACD = 4.8/5.1 (Hoffer Q), SF = 1.1/1.5 (Holladay I) and d = 4.2/4.6 (Haigis) were extracted and using linear regression a lens constant triplet for the Haigis formula of a(0) = 4.39, a(1) = 0.29, a(2) = 0.11/a0 = 4.73, a(1) = 0.30, a(2) = -0.01 could be derived.

Ophthalmic surgeons or surgical centers are encouraged to check (refractive) outcomes after cataract surgery permanently in terms of quality control. If a systematic trend in ΔREF could be extracted from the data set a customization of the lens-specific constants is recommended to eliminate systematic errors. Such customization is only valid for a dedicated environment (e.g. for one surgical center with standardized surgical techniques and measurement equipment) and cannot be generalized.