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Studying the contribution of posterior corneal astigmatism to total corneal astigmatism

Poster Details

First Author: H.Helaly EGYPT

Co Author(s):                  

Abstract Details


To study the contribution of the posterior corneal surface to the total corneal astigmatism


Faculty of Medicine, Alexandria University, Egypt


A clinical study that included 100 eyes of 100 persons with clear healthy corneas. Pentacam Scheimpflug imaging was performed to measure anterior and posterior corneal astigmatism and central corneal thickness. The total corneal power was calculated using the Gaussian optics formula. All included subjects signed an informed consent


The anterior corneal astigmatism was with the rule (steep meridian vertical) in younger age (76% of persons) and this tended to be against the rule in older age (69% of persons). Vertical meridian was considered as 90 + 30 degrees. Ignoring the posterior corneal surface astigmatism resulted in error in calculating the total corneal astigmatism (error of 0.26 D).


Calculating astigmatism without putting into consideration the posterior corneal surface may result in error or estimation of the total corneal astigmatism. This may affect the use of toric intraocular lenses. FINANCIAL INTEREST: NONE

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