Impact of axis misalignment of toric intraocular lenses on refractive outcomes after cataract surgery.
OBJECTIVE
To theoretically and clinically evaluate the impact of axis misalignment of toric intraocular lenses (IOLs) on postoperative refraction.


METHODS
International Vision Correction Research Center, University of Heidelberg, Heidelberg, Germany.


METHODS
Case series.


METHODS
A method based on mathematical solutions to obliquely crossed spherocylinders was derived according to the pseudophakic refractive properties and used to analyze the impact of toric IOL misalignment on postoperative refraction. The refractive outcomes were theoretically analyzed and actual postoperative outcomes assessed to confirm the theoretically identified impact.


RESULTS
The mean IOL misalignment was 12.5 degrees ± 6.7 (SD). Three main factors had an impact on refractive outcomes: hyperopic change in refractive sphere, reduction in astigmatic correction, and rotation of the astigmatic axis. The mean calculated spherical change was 0.32 ± 0.23 diopters (D) and the actual change, 0.36 ± 0.71 D. The mean calculated reduction in astigmatic correction was 0.65 ± 0.45 D and the actual reduction, 0.95 ± 0.54 D, indicating undercorrection of preexisting astigmatism. The mean calculated absolute astigmatic rotation was 32.7 ± 13.2 degrees (range 8 to 55 degrees) and the actual rotation, 29.1 ± 17.4 degrees. There was a correlation between the calculated and actual reduction (r(2) = 0.51; P = .001) and between the calculated and actual rotation (r(2) = 0.86; P<.001).


CONCLUSIONS
In addition to a reduction in astigmatic correction, misalignment of toric IOLs induced hyperopic spherical change and astigmatic rotation.
Guangdong Eye Institute, Guangdong Academy of Medical Sciences, Guangzhou, China.
Haiying
H
Jin
Il-Joo
IJ
Limberger
Angela
A
Ehmer
Haike
H
Guo
Gerd U
GU
Auffarth
D000328:Adult; D000368:Aged; D058452:Axial Length, Eye; D006801:Humans; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D008433:Mathematics; D008875:Middle Aged; D008962:Models, Theoretical; D018918:Phacoemulsification; D011183:Postoperative Complications; D019591:Pseudophakia / Q000503:physiopathology*; D012029:Refraction, Ocular / Q000502:physiology*; D012030:Refractive Errors / Q000503:physiopathology*; D055815:Young Adult