Devika Krishnadas1 , Girija Krishnapillai2 , Meenu Choorackathadathil Jacob3
BACKGROUND Cataract is the leading cause of blindness and visual impairment throughout the world and the commonest cause of visual impairment in older adults. Surgery is the only definitive treatment currently available for visually significant lenticular opacity. Cataract extraction with the implantation of an artificial intraocular lens (IOL) is the most commonly performed ophthalmic surgical procedure. Accurate calculation of IOL power is necessary for attaining the desired postoperative refraction. Aim of this study is to compare the accuracy of Intra Ocular Lens (IOL) power calculation by two different methods, with partial coherence interferometry in Carl Zeiss IOL master and applanation ultrasound biometry, by analysing the post-operative refractive status. METHODS It is a prospective study, 150 eyes, cataract extraction by single surgeon during March 2013-2014 at Little Flower Institute of Ophthalmology. Before surgery axial length and IOL power measured by both IOL master and contact Amplitude scan (A scan) ultrasound biometry. Surgery was uneventful temporal phacoemulsification, clear-corneal incision with posterior chamber IOL implantation. IOL power calculated with IOL master was implanted for all patients. RESULTS 150 eyes analysed. Mean axial length: IOL Master calculated axial length was 0.02 mm longer compared to ultrasound (p value <.001). Mean spherical equivalent on 2 weeks and 6 week follow up shows no significant difference. Post-operative mean Best Corrected Visual Acuity (BCVA) was 6/6 in 94% patients and 6/9 or better in 99.3% patients. CONCLUSIONS Though there is no significant difference in mean prediction error and final spherical equivalent with these two machines, the patients who attained refractive accuracy within 0.25 D was considerably more with PCI calculated IOL power compared to A scan. Mean spherical equivalent in patients at 1-2 weeks and 4-6 weeks showed no significant difference, demonstrated the early stability of refractive status after phacoemulsification.
