Distribution of Posterior Corneal Astigmatism According to Axis Orientation of Anterior Corneal Astigmatism

Abstract

PurposeTo investigate the distribution of posterior corneal astigmatism in eyes with with-the-rule (WTR) and against-the-rule (ATR) anterior corneal astigmatism.MethodsWe retrospectively examined six hundred eight eyes of 608 healthy subjects (275 men and 333 women; mean age ± standard deviation, 55.3 ± 20.2 years). The magnitude and axis orientation of anterior and posterior corneal astigmatism were determined with a rotating Scheimpflug system (Pentacam HR, Oculus) when we divided the subjects into WTR and ATR anterior corneal astigmatism groups.ResultsThe mean magnitudes of anterior and posterior corneal astigmatism were 1.14 ± 0.76 diopters (D), and 0.37 ± 0.19 D, respectively. We found a significant correlation between the magnitudes of anterior and posterior corneal astigmatism (Pearson correlation coefficient r = 0.4739, P<0.001). In the WTR anterior astigmatism group, we found ATR astigmatism of the posterior corneal surface in 402 eyes (96.6%). In the ATR anterior astigmatism group, we found ATR posterior corneal astigmatism in 82 eyes (73.9%). Especially in eyes with ATR anterior corneal astigmatism of 1 D or more and 1.5 D or more, ATR posterior corneal astigmatism was found in 28 eyes (59.6%) and 9 eyes (42.9%), respectively.ConclusionsWTR anterior astigmatism and ATR posterior astigmatism were found in approximately 68% and 91% of eyes, respectively. The magnitude and the axis orientation of posterior corneal astigmatism were not constant, especially in eyes having high ATR anterior corneal astigmatism, as is often the case in patients who have undergone toric IOL implantation.

Distribution of posterior corneal astigmatism and aberration before cataract surgery in Chinese patients

“…Studies also found that with increasing age, the anterior and total corneal steep meridian shifted from WTR to ATR, whereas the posterior corneal steep meridian did not change significantly [6,7,12]. Our study was consistent with the previous findings.…”

“…Savini and Naeser [11] have found that neglecting the posterior corneal astigmatism (PCA) had the highest effect on the refractive error after Toric IOL implantation. However, studies on the overall characteristics of PCA and posterior corneal aberration in a large cohort of patients remain rare [5,12]. Data on the status of posterior cornea are of clinical significance to the TCS assessment, cataract surgical parameters setting, and choosing appropriate IOL [1].…”

Posterior Corneal Characteristics of Cataract Patients with High Myopia

“…There was a significant positive correlation between posterior corneal astigmatism and anterior corneal astigmatism for the high myopia group, especially when the steep meridian was aligned vertically for the anterior corneal surface, which agreed well with the findings of previous studies [10,14]. However, we found no correlation between the magnitude of posterior corneal astigmatism and total corneal astigmatism.…”

Clinical outcomes with toric intraocular lenses planned using an optical low coherence reflectometry ocular biometer with a new toric calculator

“…Orientation of PCA is also variable. It may be possible to predict the orientation of the steep meridian of the posterior cornea when the steep meridian of the anterior cornea is vertical (with-the-rule, or WTR), but it is more difficult to predict when the steep meridian of the anterior cornea is horizontal (against-the-rule, or ATR) or oblique, especially in patients with high ATR anterior corneal astigmatism 8,9. Given the above, corneal astigmatism measurements that rely only on measurement of the anterior corneal surface may be poor predictors of the true total corneal astigmatism.…”