This is to compare preoperative and postoperative binocular functional vision in patients with unilateral intraocular len（IOL） in one eye and mild cataract in the fellow eye.

The subjects are the patients who underwent monocular IOL implantation before and present mild cataract in the fellow eye.Compare preoperative and postoperative the binocular functional vision and the satisfaction of patients when the patients ask for the surgery (phacoemulsification and IOLs implantation)on the fellow eye. The type of IOLs maybe according to the patients preference and the eyes condition.The subjects will be divided into three groups according to the type of the IOLs，including monofocal group,bifocal group,and trifocal group.

Inclusion Criteria:

• Patients who had monocular intraocular lens in one eye with mild cataract in the fellow eye ask for the cataract surgery in the fellow eye
• Regular corneal topography and corneal astigmatism ≤ 0.75 Diopter

Exclusion Criteria:

• Pregnant or nursing women
• In the presence of other ocular diseases that may affect the stability of the lens capsule (pseudoexfoliation syndrome, glaucoma, traumatic cataract, Marfan syndrome, etc.)
• In the presence of other ocular diseases that is expected to have a poor final visual acuity of worse than 0.2 logMAR after surgery (amblyopia, strabismus, keratoconus, etc.)
• Pupil abnormality (non-reactive pupil, tonic pupils, abnormally shaped pupils, etc.)
• Patients using systemic or ocular medication that affect visual acuity.
• Patients with history of ocular trauma or prior ocular surgery including refractive procedures
• Patients participating in other clinical trials during the study.