Posters

Characteristics of Posterior Corneal Astigmatism in Different Stages of Keratoconus (2366 eyes)

Poster Details

First Author: S.Zarriq MOROCCO

Co Author(s): C. Khodriss   A. Bennis   F. Chraibi   M. Abdellaoui   I. Benatiya        

Abstract Details

Purpose:

Assessment of corneal astigmatism at both surfaces plays an important role in vision correction procedures, either by rigid gas permeable contact lenses or by toric intraocular lens (IOL). Changes in the anterior surface of the cornea in keratoconus have been frequently described in the literature, only limited studies are available regarding the posterior corneal surface. The aim of our study is to evaluate the magnitudes and axis orientation of anterior corneal astigmatism (ACA) and those of posterior corneal astigmatism (PCA), the correlation between ACA and PCA, and the correlation between corneal astigmatism and asphericity in the different stages of keratoconus.

Setting:

We present a retrospective study including consecutive patients with KCN who were examined at the department of ophthalmology of the Hassan II university hospital of Fes, Morocco, between 2012 and 2019.

Methods:

bilateral Scheimpflug images of the anterior eye segment of 1183 patients with keratoconus were studied retrospectively. Eyes with previous trauma, other corneal diseases, or a history of surgery were excluded. The 2366 eyes were divided into four KCN subgroups according to the Amsler-Krumeich classification. The statistical analysis was performed using SPSS, we studied the correlation between mean keratometry and both anterior and posterior astigmatisms using the coefficient of Pearson. The correlation between ACA and PCA was evaluated using linear regression in different groups.  P value less than 0.05 was considered statistically significant.

Results:

The average amounts of total, anterior and posterior corneal astigmatism were 4,41± 3,18 D, 2.21+/-3,19 D, and 4,42D+/-3,9 respectively. The average PCA was 1,16, 0,7, 0,6 and 4D in stage 1,2,3 and 4 KCN respectively. There was a moderate correlation between ACA and PCA in stage 1, 2 and 3 keratoconus. This correlation was small in stage 4. The PCA was mostly against the role, and there was a tendency of increasing against the rule astigmatism in anterior corneal surface with increasing severity of KCN. There was a correlation between corneal astigmatism and asphericrity in stages 1,2, and 3 KCN

Conclusions:

In our study, the anterior corneal surface is more affected in stage 1 compared to stage 2 KCN, it is also more affected by the increase in the severity of KCN than the posterior surface. We also noticed that corneal astigmatism is correlated with corneal asphericity in stages 1,2 and 3 KCN, and that the anterior corneal astigmatism tends to become against the rule with progression of KCN.

Financial Disclosure:

None