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Overall refractive astigmatism correlates with shorter chord length
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BARCELONA — Measurement at a 2 mm chord length was more strongly correlated with overall ocular refractive astigmatism than when a 5 mm peripheral chord length was used, according to a speaker here.
“We wanted to look at that relationship between corneal astigmatic power and ocular refraction and also look at different parameters such as chord length and ... different techniques for measuring corneal power,” Phillip J. Buckhurst, MD, said at the European Society of Cataract and Refractive Surgeons meeting.
Phillip J. Buckhurst
In the study conducted by Buckhurst and colleagues, 75 eyes of 75 patients were all implanted with the Tecnis ZA900 monofocal IOL (Abbott Medical Optics). Patients were followed up at 3 to 6 weeks and at 3 to 6 months postoperatively, he said.
The IOLMaster 500 (Carl Zeiss Meditec), OPD-Scan III (Nidek) and Pentacam HR (Oculus) were used to look at chord length and true net power, as well as sagittal power, Buckhurst said.
“We actually found that only the true net powers were giving us a similar result to the refractive astigmatism. In fact, at visit two there was only the 2 mm chord length that was similar to the refractive outcomes. We were finding that the rest of the sagittal powers were underestimating the magnitude of astigmatism when compared to the refractive outcomes,” Buckhurst said.
“More needs to be explored with looking at the relationship between the corneal power and refractive astigmatism, but what seems to be quite key is that we cannot just ignore chord length and that it is important at what zone that corneal astigmatism is measured,” he said. — by Nhu Te
Disclosure: Buckhurst reports no relevant financial disclosures.