This article is more than 5 years old. Information may no longer be current.
Neglecting posterior corneal surface may skew corneal astigmatism estimation
Am J Ophthalmol. 2009;147(5):788-795.
Click Here to Manage Email Alerts
Neglecting the posterior corneal surface measurement may reduce the accuracy of corneal astigmatism estimation, according to a study.
The prospective, observational study included right eyes of 493 subjects measured with the Pentacam rotating Scheimpflug camera (Oculus). Keratometric corneal astigmatism values were obtained by using the anterior corneal surface measurement and keratometric index and negating the posterior corneal surface measurement. Total corneal astigmatism values, derived with the Pentacam, were obtained by using doubled-angle vector analysis of astigmatism on both corneal surfaces, the study authors said.
The mean arithmetic estimation error of the keratometric corneal astigmatism magnitude for the corneal astigmatism magnitude was –0.06 ± 0.28 D; the absolute estimation error of those values was 0.24 ± 0.16 D.
The mean arithmetic estimation error of the keratometric corneal astigmatism angle for the corneal astigmatism angle was –0.06° ± 12.7°. The absolute estimation error was 7.4° ± 10.3°.
Of the 493 eyes, 142 eyes had a keratometric corneal astigmatism magnitude varying more than 0.5 D from the corneal astigmatism magnitude or a keratometric corneal astigmatism angle deviating more than 10° from the corneal astigmatism angle, the authors said.