Abstract： AIM:To investigate the effect of wearing corneoscleral contact lens on visual acuity,and corneal parameters in keratoconus patients.METHODS:In this prospective study,43 cases(83 eyes)with keratoconus were included and examined.A corneoscleral contact lens was fitted,and thorough exams were carried out at baseline,3 and 6 mo after wearing lenses,including slit lamp examination,objective and subjective refraction,uncorrected visual acuity(UCVA),and best-corrected visual acuity(BCVA),keratometry(Kmax,K1 and K2),central corneal thickness and endothelial cells count.RESULTS:Mean BCVA(LogMAR)improved from 0.34± 0.23 with the spectacles to 0.03±0.05 with the corneoscleral contact lenses in 6 mo(P＜0.001).Kmax changed from 52.80±5.93 D to 51.51±5.64 D in 6 mo(P＜0.001),central corneal thickness changed from 483.84±34.69 μm to 476.28±35.38 μ m(P＜0.001),and endothelial cell count changed from 2559.18±275.7 cells/mm2 to 2572.73± 274.3 cells/mm2 after wearing corneoscleral contact lens for 6 mo(P＜0.001).CONCLUSION:Corneoscleral lenses could significantly increase visual acuity,since there were no clinical noticeable changes in the corneal parameters,this lenses can be used safely in patients with keratoconus.