Estimation accuracy of surgically induced astigmatism on the cornea when neglecting the posterior corneal surface measurement

. Purpose:  To evaluate the accuracy of corneal surgically induced astigmatism (SIA) estimation when neglecting the posterior corneal surface measurement. Methods:  Fifty right eyes undergoing phacoemulsification were measured with a rotating Scheimpflug camera (Pentacam; Oculus Inc., Wetzlar, Germa...

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Published in:Acta ophthalmologica (Oxford, England) England), 2011-08, Vol.89 (5), p.417-422
Main Authors: Cheng, Li‐Sheng, Tsai, Ching‐Yao, Tsai, Ray Jui‐Fang, Liou, Shiow‐Wen, Ho, Jau‐Der
Format: Article
Language:English
Subjects:
Aged
Aged, 80 and over
Astigmatism - diagnosis
Astigmatism - etiology
Astigmatism - prevention & control
Cataract
Corneal Topography - instrumentation
Corneal Topography - methods
Corneal Topography - standards
Female
Humans
Male
Middle Aged
Models, Biological
Monitoring, Intraoperative - instrumentation
Monitoring, Intraoperative - methods
Monitoring, Intraoperative - standards
phacoemulsification
Phacoemulsification - adverse effects
Phacoemulsification - methods
posterior cornea
Postoperative Complications - diagnosis
Postoperative Complications - etiology
Postoperative Complications - prevention & control
Postoperative Period
Preoperative Care
Reproducibility of Results
Retrospective Studies
surgically induced astigmatism
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Summary:. Purpose:  To evaluate the accuracy of corneal surgically induced astigmatism (SIA) estimation when neglecting the posterior corneal surface measurement. Methods:  Fifty right eyes undergoing phacoemulsification were measured with a rotating Scheimpflug camera (Pentacam; Oculus Inc., Wetzlar, Germany) both before and after surgery. Clear corneal incisions with one suture were used in the phacoemulsification surgery. The keratometric corneal SIA (KSIA) was derived using the anterior corneal surface measurement and the keratometric index (1.3375) while neglecting the posterior corneal surface measurement. The Pentacam‐derived total corneal SIA (PSIA) was derived by vergence tracing and polar value analysis [KP(135) and KP(180)] of the measurements on both corneal surfaces. Results:  The mean arithmetic estimation errors of the KSIA for the PSIA were 0.16 ± 0.32 (−0.52 to 1.14) D for the KP(135), and −0.02 ± 0.30 (−0.75 to 1.29) D for the KP(180). There was a significant difference between the KP(135) components of the KSIA and PSIA. Bivariate analysis revealed a statistically significant difference between the combined means of the KSIA and PSIA. Overall, 24% had either a KP(135) component of the KSIA that differed by > 0.50 D from that of the PSIA or a KP(180) component of the KSIA that differed by > 0.50 D from that of the PSIA. The blurring strength caused by neglecting the posterior corneal measurement was > 0.50 D in 24% of eyes. Conclusion:  Neglecting the posterior corneal surface measurement may lead to significant deviation in the corneal SIA estimation after phacoemulsification in a proportion of eyes.
ISSN:1755-375X
1755-3768
DOI:10.1111/j.1755-3768.2009.01732.x