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The goal of refractive surgery is usually to make the patient's eyes plano, that is, eliminate any refractive error (prescription). An exception to this is monovision, where one eye is deliberately left with a small amount of myopia. Additionally, some patients with high or unusual prescriptions know that they will not achieve plano but are aiming to reduce their prescription to a small amount.
Merely being plano, however, does not guarantee that vision will actually be good or acceptable to the patient. A patient can be plano but also have small, moderate or large amounts of aberrations making vision quality poor. In other words you can be plano and at the same time have double vision, night vision disturbance or other defects - or to put it differently your eyes might be the right shape for good vision but have bumpy or irregular surfaces that interfere with vision.
Plano lenses have several uses. A patient with a prescription in only one eye might have eyeglasses with one plano lens and one prescription lens. Some dry eye patients wear glasses with plano lenses to protect their eyes from drafts, thereby reducing surface evaporation. |
