AIM: To evaluate intraocular lens power (IOL) calculation and biometry before and 3mo after implantation of Keraring 355° intrastromal corneal ring segment (ICRS;Mediphacos, Belo Horizonte, Brazil) in keratoconic eyes.METHODS: In this cohort study, data of 19 keratoconus eyes of 18 patients which undergone ICRS implantations were gathered before and 3mo after surgery.Uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), manifest refraction, IOL power calculation formulas, axial lenght (AL) and keratometry were analayzed.RESULTS: Mean age of participants was 29.58±0.6.UCVA improved from 0.84 (0.35) logMAR to 0.43 (0.31) logMAR significantly (P<0.001).BCVA and AL didn`t change significantly after 3mo.All Sphere, cylinder and spherical equivalent (SE) were improved significantly (P<0.001).On the other hand, keratometry 1 (K1) and keratometry 2 (K2) decreased significantly.It was a considerable change in SRK/Ⅱ (P<0.001), Hoffer Q (P<0.001) and Holladay Ⅰ(P<0.001) after 3-month`s follow-up.Among this formula SRK/II had the lowest change.CONCLUSION: In addition to improvement in visual, refractive, and keratometry outcomes after Keraring implantation, there was a significantly changes in IOL calculation formulas values.However, ICRS procedure doesn`t interfere considerably AL in eyes, but it seems reduced keratometric values lead to IOL power calculations more accurately and all formulas suggested same IOL power.