For the purpose of this discussion a monocular cataract will be defined as advanced opacification of the crystalline lens in one eye, while the other lens is clear or has opacities that have not yet affected visual acuity. The case of the infant born with monocular cataract is another problem and will not be discussed here.
Until recently a cataract in one eye was allowed to go to maturity and beyond as long as the vision remained useful in the other eye. An ancient dictum said one should wait until vision dropped to 20/70 in the better eye before operating on the other. The reasoning behind this was that as long as the patient could see well enough to get around and to do close work with the better eye, the eye operated on would be of little or no good. A patient could not wear a cataract lens before
GOAR EL. The Management of Monocular Cataracts. AMA Arch Ophthalmol. 1955;54(1):73-76. doi:10.1001/archopht.1955.00930020075011