Role of ‘A’ Scan in Prediction of Intraocular Lens Power- A One Year Cross Section Study

Abstract

INTRODUCTION ABSTRACT Cataract is the most common curable cause of blindness in India. Today’s cataract surgery occurs at an earlier age and with implants for monofocal and multifocal corrections, patients now anticipate excellent ‘uncorrected acuity’, not just improved ‘best corrected vision’. This expectation places increased importance on accurate biometry and intraocular lens ( IOL ) calculations. OBJECTIVE OF THE STUDY: To assess the accuracy of ‘A’ scan unit in determining intraocular lens power. METHODOLOGY One hundred and twenty patients undergoing cataract surgery, at KLESPKH and Medical Research Centre, Belgaum were taken in the study. Prior to the surgery a complete ocular examination was done including measuring the intra-ocular pressure and patency of lacrimal drainage system. Routine pre-operative investigations were done and pre-operative medications were given to all the patients. Keratometry was done using Bausch and Lomb type keratometer. The axial length was measured with Appasamy ( Appascan2000) A scan unit, Retinoscopy was done at 6 th week post-operatively and the readings were recorded. The post-operative refraction was taken as spherical equivalent. OBSERVATIONS AND RESULTS The results of this study showed that the predictive error varied in the range of +/- 1 in 82.5% of patients, +/-2 in 95.0% of patients and +/-3 in 100%. Out of 120 patients X 48% had the best corrected visual acuity of 6/9 and of these subjects 41% were in the age group of 51-60 years . CONCLUSION Biometry is definitely essential and accurate in calculating intra-ocular lens power. A careful selection of intraocular lens power might reduce unexpected surprises but will not eliminate them and both the patient and the surgeon should be prepared for the same.