Biometry accuracy using zero- and negative-powered intraocular lenses.

Journal article

PURPOSE: To audit the accuracy of biometry using the SRK/T formula when negative- or zero-powered intraocular lenses (IOLs) are predicted and to compare the results between A-scan, B-scan, and optical methods of biometry. SETTING: Moorfields Eye Hospital, London, United Kingdom. METHODS: This retrospective analysis comprised 78 eyes of 54 patients having cataract surgery with zero- or negative-powered IOLs. Axial lengths were measured with A-scan, B-scan, applanation, or optical methods. Differences between SRK/T-predicted and actual postoperative refraction were analyzed for 75 eyes having cataract surgery. Ocular comorbidity, visual acuity, and biometry readings were also compared. RESULTS: Forty-one percent of 75 patients analyzed were within +/-1.00 diopter (D) of the predicted refraction, although there was a significant tendency toward a hyperopic overcorrection by 1.14 D (95% confidence interval, 0.89-1.39 D). This overcorrection error was consistent across all 3 biometry methods used to estimate axial length and increased with the use of stronger (more negative) IOLs. CONCLUSION: Surgeons should be aware of the tendency for negative-powered lenses to overcorrect and lead to a hyperopic outcome when using the SRK/T biometry formula in highly myopic eyes. A weaker-powered negative IOL is recommended to aim for a more myopic postoperative outcome by about 1.00 to 2.00 D.

Authors: Maclaren, R; Sagoo, MS; Restori, M; Allan, B

• Publication status: Published
• Journal: Journal of cataract and refractive surgery
• Volume: 31
• Issue: 2
• Pages: 280-290
• Publication date: 2005-02-01
• DOI: 10.1016/j.jcrs.2004.04.054
• EISSN: 1873-4502
• ISSN: 0886-3350
• Language: English
• Keywords: Reproducibility of Results; Biometry; Refraction, Ocular; Humans; Myopia; Lens Implantation, Intraocular; Accommodation, Ocular; Phacoemulsification; Retrospective Studies; Lenses, Intraocular