Impact of Posterior Corneal Astigmatism in Toric IOL Selection
Purpose
To evaluate the impact of posterior corneal astigmatism on outcomes with toric intraocular lenses (IOLs).
Methods
Prospective, comparative, correlational design with a non-experimental field study. Corneal astigmatism was determined in 72 eyes of 40 patients diagnosed with cataract and corneal astigmatism through two methods: placid discs (Nidek Scan II) and ray traicing (Ziemer Galilei ™ G2) divided into two groups according to results: Group 1 ≤1.10 astigmatism diopters (D) by placido disks and Group 2, Total ≤1.10 corneal astigmatism according traicing ray. Following Phacoemulsification and IOL implant refractive results and visual acuity (VA) were assessed. Data were expressed as arithmetic mean, standard deviation (SD), absolute figures and percentages, statistical significance P = 0.05.
Results
Group 1, residual astigmatism -1.16 D ± 0.57 Standard Deviation (SD) with AV LogMar 0.15 ± 0.06 SD; Group 2: -0.49 ± 0.38 D with AV DS 0 DS LogMar ± 0.07 respectively. Test of mean difference between results obtained by both devices: p≤0,05. A positive linear correlation between measurements of anterior and posterior corneal astigmatism by the ray traicing method (correlation coefficient r = 0.22 and p <0.05) was found.
Conclusion
The selection of toric intraocular lenses based on anterior corneal measurements could induce overcorrection in eyes with astigmatism with the rule and undercorrection in those with astigmatism against the rule.