A comparison of toric IOL cylinder steps of 0.75D and 0.5D to neutralize astigmatism and determining the optimal toric IOL cylinder step based on over 1000 toric implants
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First Author: M.Goggin AUSTRALIA
Co Author(s): B. LaHood M. Lawless G. Sutton C. Hodge
Two of the most commonly available toric IOL cylinder power steps worldwide are 0.75D and 0.5D. This study assessed whether there was any significant difference in the ability of these two power steps to neutralize corneal astigmatism following cataract surgery. The optimal cylinder power step magnitude for toric IOLs was also calculated. This will help surgeons decide which toric IOL to use to best aim for zero residual astigmatism and will assist toric IOL manufacturers in knowing whether there is need to change their current cylinder power steps
Private practice in Adelaide and Sydney, Australia and Auckland, New Zealand
745 eyes were implanted with Alcon Acrysof toric IOLs with cylinder powers of 1D, 1.5D, 2.25D, 3D, 3.75D, 4.5D, 5.25D, and 6D. 700 eyes were implanted with Zeiss AT TORBI toric IOLs with cylinder powers from 1D upwards in 0.5D increments. Six weeks post-operatively, accurate refraction and repeat biometry were taken. Refractive outcomes were compared for each toric IOL group to an optimal outcome of zero residual astigmatism. An optimal toric IOL cylinder power was also calculated for each eye and this information used to model an ideal toric IOL cylinder step. .
Post-operative refractive astigmatism was reduced compared to pre-operative corneal astigmatism in all eyes. There was no clinically or significant difference between the 0.75D and 0.5D cylinder power steps based on their ability to achieve zero refractive astigmatism. The ideal optimal toric IOL cylinder step range was 0.43D, which maximizes the number of eyes with residual refractive astigmatism within 0.5D of zero.
Toric IOL use is beneficial in reducing the burden of refractive astigmatism with both ranges of toric IOL cylinder steps investigated. Surgeons can be reassured that whether they choose to use a toric IOL with cylinder steps of 0.75D or 0.5D they will be equally good at achieving as close to zero residual refractive astigmatism as possible. An optimal toric IOL cylinder power range of steps would be 0.43D which for practical manufacturing reasons would be rounded up to 0.5D.