Aim: To compare axial length measurement and other parameters in biometry obtained by optical and ultrasound applanation methods, among pre-operative cataract patients in Eye Foundation Hospital, Ikeja Lagos, with a view to identifying any significant difference between the methods. Methodology: the study was a comparative cross-sectional study; a total of 209 eyes of 152 patients were recruited into the study. Comparison, correlation and agreement of axial length measurements of the eye with optical and applanation ultrasound were analyzed. The anterior chamber depths, and intraocular lens power calculated using SRK-II formula, were also analyzed on all consenting consecutive pre-operative cataract patients during the period of study. Data analysis was done using Statistical Package for Social Sciences (SPSS) version 20 software. Mean and standard deviation were reported. Pearson’s correlation coefficient was calculated for axial length and anterior chamber depth between both methods. A regression linear equation was also plotted for axial length by both methods. Bland-Altman’s plots were used to evaluate the agreement in axial length between methods set at 95% confidence intervals. Statistical significance of measurements by both methods was determined using paired t-test at p value less than 0.05 (p < 0.05). 1 Results: the mean age of the study patients was 65.68 (±10.6) years, in an age range of 42 to 94 years. There were more female patients represented in the study (52.6%), with 53.11% of measurements in the right eye. Mean axial length measurement of 23.79 (±1.06) mm by the optical method was statistically significantly longer than the mean of 23.75 (±1.07) mm by the ultrasound applanation method (p<0.038). The optical method measured longer in the male (24.24 ± 1.07 mm) than in the female (23.29 ± 0.81 mm) gender; anterior chamber depth was also deeper in male. There was high correlation (r =0.935, p<0.001) between axial length measurements by both techniques. Bland-Altman’s plot showed an agreement between axial length measurements by both optical (IOL Master) and ultrasound applanation methods (0.798 to -0.708; 95% CI). The mean intraocular lens power calculated using SRK-II formula were 20.90 ± 2.3 D (optical) and 19.75 ± 2.4 D (applanation ultrasound); their difference was statistically significant but with high correlation.