Posters

Prevalence of anterior and posterior astigmatism patterns and their influence in the amount of the total corneal astigmatism by ray tracing: new simple strategy to calculate toric IOLs

Poster Details

First Author: C.Arce BRAZIL

Co Author(s):    S. Srinivasan              

Abstract Details

Purpose:

Study the anterior, posterior and total corneal astigmatism (TCA by ray tracing). Propose a simple strategy to calculate Toric IOLs from any manufacturer in all type of astigmatisms

Setting:

Eye Clinic, Ayr Hospital, Scottland, UK and Private Eye Clinic, Campinas, Brazil

Methods:

Value and axis of SimK, posterior axial and TCA cylinders were studied in 591 eyes with Galilei

Results:

Anterior/posterior cylinders were parallel (1)WTR/WTR in 59% (2)ATR/ATR in 4% (3)OBL/OBL (oblique) in 4%, and crossed (4) ATR/WTR in 13% (5)WTR/ATR in 0% (6)OBL/OBL in 0.5% (7)WTR/OBL in 2% (8)OBL/WTR in 14% (9)ATR/OBL in 4% and (10)OBL/ATR in 0.3%. Type 1 was more frequent at all ages. Types 4 and 8 increased with age and were more frequent after 50-60 years old. Crossed astigmatism with posterior ATR is almost nonexistent. TCA was smaller than the anterior cylinder in types 1 (93%) and 3 (90%), and larger in types 2 (68%), 4 (99%), 8 (76%), 9 (87%) and 6, 7, and 10 (100%)

Conclusions:

TCA tends to be smaller than anterior cylinder when the anterior and posterior astigmatisms have parallel WTR and OBL axes, and larger if they were parallel ATR or crossed 45° to 90°. WTR/WTR type was the more frequent. OBL/WTR and ATR/WTR astigmatisms increase with age and have more prevalence after 50-60 years old. Instead of nomograms using anterior cylinder, fudge factors or vector analysis to assume the TCA, the system already calculates it using all components including posterior astigmatism and HOAs. We propose a strategy to calculate toric IOLs from any manufacturer in all type of astigmatisms by simply combining the SimK average and the TCA FINANCIAL INTEREST: One of more of the authors... receives consulting fees, retainer, or contract payments from a company producing, developing or supplying the product or procedure presented, One of more of the authors... travel has been funded, fully or partially, by a company producing, developing or supplying the product or procedure presented