PURPOSE: To determine changes in straylight after iris-fixated phakic intraocular lens implantation (pIOL) and to investigate the relationship between straylight and several preoperative and postoperative variables. DESIGN: Institutional, prospective cross-sectional study. METHODS: Artiflex (Ophtec B.V.) pIOL implantation was performed in 61 eyes (36 patients). Straylight values were measured before surgery and 3 months after surgery using the Oculus C-Quant (Oculus Optikgerate). Furthermore, correlations were analyzed between straylight and the following parameters: keratometry, axial length, spherical equivalent, astigmatism, pIOL power, best spectacle-corrected visual acuity, and pupil size. RESULTS: Mean straylight decreased from 1.18 +/- 0.17 log units before surgery to 1.13 +/- 0.17 after surgery (P = .016). Higher preoperative straylight values were associated with larger postoperative decreases in straylight (r = -0.534; P < .001). Higher postoperative straylight values were correlated to higher axial length (r = 0.444; P = .001) and lower keratometry values in diopters (r = -0.414; P = .001). After regression analysis, only axial length was found to be an independent predictor of preoperative and postoperative straylight (P < .001 and P = .001, respectively). After correcting for the axial length of an emmetropic eye (23.44 mm), all straylight correlations disappeared, indicating that an increase in distance from cornea to retina explains the increase in straylight values in longer eyes. CONCLUSIONS: Retinal straylight was reduced significantly after Artiflex pIOL implantation. Besides age, axial length was the only predictor of preoperative and postoperative straylight values. The increased tissue length light has to pass from cornea to retina, might explain the increase in straylight values in longer eyes.