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Corneal posterior astigmatism: contribution for total corneal astigmatism and relation with age

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Session Details

Session Title: Corneal Astigmatism Assessment. Surgery Equipment

Session Date/Time: Saturday 05/09/2015 | 11:00-13:00

Paper Time: 11:38

Venue: Main Auditorium

First Author: : R.Leite PORTUGAL

Co Author(s): :    T. Monteiro   N. Franqueira   F. Faria-Correia   F. Vaz           

Abstract Details


Corneal astigmatism is the most significant factor contributing to total refractive astigmatism. Studies show that the posterior corneal surface is important for calculation of total corneal astigmatism. Studies also show that astigmatism increases with age. In this study the authors evaluate the relative contribution of anterior and posterior astigmatism for total astigmatism and the association of astigmatism type with age.


Department of Ophthalmology, Hospital de Braga, Braga, Portugal


The authors measured anterior, posterior and total corneal astigmatism using Pentacam HR® Oculus tomography. The study included 123 eyes, between 20 and 80 years of age, with corneal astigmatism higher than 1,00 D and no corneal pathology or a history of previous corneal surgery. Statistical analysis was performed to calculate the relation and the axis of anterior and posterior astigmatism with age.


We found a weak and negative correlation between both anterior and posterior corneal astigmatism and age. Regarding the anterior corneal surface, with the rule (WTR) astigmatism was found at younger ages than oblique astigmatism, while against the rule (ATR) was associated with older age (ANOVA test, p value less than 0.05). We did not observe a shift in corneal posterior astigmatism with increasing age. Using a multiple linear regression model we observed that the increase in anterior astigmatism is associated with an increase in total corneal astigmatism (p less than 0.05) and that the increase in posterior astigmatism is associated with a decrease in corneal total astigmatism (p less than 0,05).


Anterior and posterior corneal astigmatism contribute differently for total corneal astigmatism. The orientation of anterior astigmatism vector shifts significantly with age, while posterior astigmatism vector does not change. Measurement of posterior corneal astigmatism is of clinical relevance for the calculation of toric intraocular lenses.

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