Purpose: To analyse the distribution of the difference between both eyes in the calculation of the dioptric power of the intraocular lens in a series of 7994 patients and the biometric variables that determine it. Methods: The data of patients between 3 and 99 years old, residents of the city of Guayaquil and neighbouring sites, who received ocular biometry by partial optical coherence interferometry between 2004 and 2020 were reviewed. Ocular biometrics, including axial length (AL), anterior chamber depth (ACD), and the mean corneal dioptre power (CD), were measured by partial coherence interferometry. Refraction without or with cycloplegia was recorded in spherical equivalent (SE). The Haigis formula from the IOL Master instrument was used to calculate the dioptric power of the intraocular lens in both eyes. Results: Data from the bilateral optical biometry of 7994 patients were analysed. The mean and standard deviation of AL, CD, ACD and dioptre power of the IOL were 23.66 ampersand-flag-changeplusmn; 1.25, 43.70 ampersand-flag-changeplusmn; 1.49, 3.34 ampersand-flag-changeplusmn; 0.40 and 20.46 ampersand-flag-changeplusmn; 3.84, respectively. 2538 (31.7percent-flag-change) patients had equal dioptre power of the IOL between both eyes. 3243 (40.6percent-flag-change) patients had a 0.50 D difference; 1162 (14.5percent-flag-change), 1.0 D; 425 (5.3percent-flag-change), 1.5 D. 626 patients (7.8percent-flag-change) had a difference in IOL dioptre of 2 D or more, with a maximum of 24 D. The asymmetry of AL between OU was ampersand-flag-changege; 0.4 mm in 10.49percent-flag-change, while that of CD reached ampersand-flag-changege; 1 D in 1.9percent-flag-change. Conclusions: 92.16percent-flag-change of patients had a difference within 1.5 D between both eyes in the calculation of the dioptre power of the intraocular lens. In case an eye is programmed in which it is impossible to perform a reliable biometry, either due to trauma or due to white or brunescent cataract, the calculation of the intraocular lens could be done taking as a reference the biometry of the contralateral eye.
