To assess the visual function of patients with keratoconus who underwent penetrating keratoplasty with the use of the VF-14 questionnaire. Fourteen patients (9 male and 5 female) with a mean age of 38 years (SD 13.59) participated in the study. All patients had keratoconus, confirmed by corneal topography, and all had previously undergone penetrating keratoplasty in one eye. Their mean best-corrected visual acuity (BCVA) binocularly was 0.185 (SD 0.077) LogMAR. None of the grafted eyes had a BCVA < 0.300 LogMAR. Fourteen healthy volunteers, age- and sex-matched, also participated in the study as control subjects. The VF-14 questionnaire was used to evaluate the effect of the ocular status in the daily life activities of the patients. The mean VF-14 result for the grafted patients with keratoconus was 62.37% (SD 22.60) and for the control group it was 100% (P < 0.001). There was only a weak correlation between the VF-14 score and the binocular BCVA (r = -0.394, P = 0.163). The mean VF-14 result in grafted patients with keratoconus is indicative of low functional ability despite the satisfactory postoperative BCVA. The absence of a significant correlation between the VF-14 score and the mean BCVA indicates that the low functional visual ability in these patients is probably associated more with the 'perceived by themselves' difficulty due to their ophthalmological condition.