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Ophthalmology and Allied Sciences

Volume  4, Issue 1, Jan-Apr 2018, Pages 28-33
 

Original Article

Optical (Partial Optical Coherence Interferometry) (AL-Scan) versus Ultrasound Biometry (A-Scan) for IOL Power Calculation: A Comparative Study

Rajitha Kondam*, Latha Gundlapally**, Ravi Kumar Reddy***

*Assistant Professor, Department of Ophthalmology, Malla Reddy Institute of Medical Sciences, Hyderabad, Telangana 500055, India. **Consultant, Maha Lakshmi Eye Hospital, Hyderabad, Telangana 500070, India. ***Professor, Dept. of Ophthalmology, Medivision Eye Care Centre, Hyderabad, Telangana 500028, India.

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DOI: http://dx.doi.org/10.21088/oas.2454.7816.4118.5

Abstract

Context: The refractive power of the human eye depends on the power of the cornea and the lens, the position of the lens, and the length of the eye. Accurate assessment of these variables is essential in achieving optimal postoperative refractive results. Aims: To compare the accuracy of IOL power calculation by measuring the axial length with Optical (Partial Optical Coherence Interferometry ALScan) biometry and Ultrasound biometry. Settings and Design: It was a prospective observational study done at Medivision eye and Health Care centre. Methods and Material: The study group was 200 patients, who underwent Phacoemulsification. The SRKT formula was used to calculate the IOL power in all patients. Autokeratometry performed with the optical scan was used in all patients. Statistical Analysis: Mean (SD) and frequency (percentage) was used to describe summary data. Paired T test was performed to explore statistically significant difference between two measurements. Chisquare was used to assess the difference between categorical variables. Results: Out of 200 patients 83 (41.5%) were female and 117 (58.5%) were male. Mean Age of the study population was 62.30±7.66 years and the range 33 to 81. The mean difference between axial lengths measured by the 2 modalities was 0.1274±0.1733 mm with AL Scan measuring higher than US Biometry (Paired TTest p < 0.05). The residual error was Zero in 75 (37.5%) eyes in the ALscan group and 59 (29.5%) eyes in the Ascan group. When analyzed at 95% confidence for the difference at zero error in preoperative prediction versus postoperative acceptance of IOL power, the predictions did not differ between both the modalities. Conclusion: The ALscan is on average a closer predictor than Ascan of the final spherical equivalent. ALscan may offer a slight advantage because of the easier and quicker operation compared with the Ascan.

Keywords: Axial; AScan; Eye; Phacoemulsification.


Corresponding Author : Latha Gundlapally, Consultant, Maha Lakshmi Eye Hospital, Hyderabad, Telangana 500070, India