Partial Coherence Laser Interferometry Versus Conventional A-Scan Acoustic Biometry in Intraocular Lens Power Calculation – Comparison of Postoperative Refractive Error
Keywords:Partial coherence laser interferometry, ultrasound A scan, IOL power formulae, biometry, A- constant, intraocular lens
Purpose: To compare the post-operative residual refractive error in patients undergoing cataract surgery using partial coherence laser interferometry (PCLI) versus A-scan Applanation acoustic biometry.
Study Design: Quantitative experimental research.
Place and Duration of Study: Shifa International Hospital (SIH), Islamabad from November 2018 to August 2019.
Methods: Total 254 patients were selected. Group A included patients whose biometry was done using PCLI method and group B included patients who had A-Scan acoustic biometry. Intraocular lens power calculation was done using SRK/T formula. Phacoemulsification surgery with foldable Intraocular lens was performed. Patients were called for follow-up visit the next day and then one month after surgery. Postoperative refractive error was checked after one month. All data were entered and analyzed using SPSS version 21.0. Descriptive statistics were used for qualitative as well as quantitative variables. We applied independent samples t-test to compare the mean postoperative refractive error in both groups. A p-value of less than 0.05 was considered significant.
Results: The mean age of patients was 65 ± 9.37 years. The preoperative mean axial length was 20.35 ± 1.1 mm in the PCLI group and 21.54 ± 1.2 mm in the ultrasound group. Mean Absolute Error (MAE) of postoperative residual refractive error in the PCLI group was 0.12 ± 0.13 mm (P = 0.003). The MAE in the ultrasound group was 0.18 ± 0.12 mm (P = 0.02).
Conclusion: The non-contact optical biometry improves the mean absolute error for postoperative refraction and is a reliable tool for biometry in phakic eyes before surgery.
Key Words: Partial coherence laser interferometry; Ultrasound A scan; Biometry; A-constant; Intraocular lens.
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