Meridional analysis for calculating the expected spherocylindrical refraction in eyes with toric intraocular lenses.
OBJECTIVE
To present a method of calculating the expected spherocylindrical refraction after toric intraocular lens (IOL) implantation and to compare it with the actual outcomes in a small group of patients.


METHODS
Eye Institute, Tan Tock Seng Hospital, Singapore.


METHODS
The expected refractions of the 2 principal meridians of the cornea (maximum keratometry and minimum keratometry) were calculated separately using the Holladay 1 formula with a modification to the data used for the effective lens position. The expected refraction was compared with the actual outcomes in 7 eyes that had phacoemulsification with toric IOL implantation.


RESULTS
The mean preoperative keratometric cylinder was 2.07 diopters (D) +/- 0.97 (SD) (range 1.25 to 3.75 D), and the mean postoperative cylinder by subjective refraction was 0.68 +/- 0.40 D (range 0.25 to 1.50 D). The mean expected cylindrical refraction was 0.62 +/- 0.46 D (range 0.30 to 1.60 D). Five eyes (71.4%) were within +/-0.25 D of the expected refraction, and all eyes were within +/-0.50 D. There was a significant reduction in cylinder after toric IOL implantation (P<.001, paired t test). There was no statistically significant difference between the magnitude of the expected cylindrical refraction and the actual postoperative cylinder by subjective refraction (P = .604).


CONCLUSIONS
Calculation of the expected spherocylindrical refraction with toric IOLs was achieved using meridional analysis.
Fam
Han Bor
HB
Eye Institute, Tan Tock Seng Hospital, Singapore.
Lim
Kooi Ling
KL
D000465:Algorithms; D003315:Cornea / Q000503:physiopathology; D006801:Humans; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D055095:Optics and Photonics; D018918:Phacoemulsification; D012029:Refraction, Ocular / Q000502:physiology*