At our Arizona LASIK locations, it’s not uncommon for a patient to visit us for the first time and say: “My vision is 20/100 (or insert any other visual acuity score here). Is this bad enough for LASIK?”
The simple response to this is, LASIK candidacy cannot be verified on your visual acuity measurements alone.
Visual acuity scores such as 20/100 describe sharpness of vision, and is measured at a certain distance based on a fixed standard. Normal visual acuity is 20/20. It means you can clearly and accurately see at 20 feet what is reality at 20 feet away. Having 20/100 vision means you should be within 20 feet to see what a person with normal vision can see 100 feet away.
To determine if your poor eyesight is suitable for LASIK, your laser vision correction doctor will figure out if your refractive error is within the range that can be treated.
What’s a Refractive Error Within the Treatable Range?
Before we delve into refractive errors that can be corrected by LASIK vision revision, let’s take a quick look on how normal vision works.
For 20/20 vision to be possible, the cornea and the lens must refract (bend) light rays direct to the very back of the eye, or specifically the retina. The retina is a layer of light-sensing photoreceptor cells – rods and cones – that convert light rays into electrochemical impulses that are sent to the brain for interpretation.
Refractive errors occur when you have an imperfectly-shaped cornea or lens. As a result, light rays do not all refract on the retina. Sometimes, as in the case of aging men and women, it’s the lens that can’t change shape enough to be able to focus on nearby objects (presbyopia).
Refractive errors include the following:
- nearsightedness (nearby objects are the only ones that are clear or distinct)
- farsightedness (far objects are the only ones that are clear or distinct)
- astigmatism (objects are blurred whether far or near)
- presbyopia (difficulties seeing up close due to the loss of elasticity in the lens)
A refractive error is measured in diopters — a unit used to denote the strength of your lens.
To qualify for the newest LASIK technology (topography-guided LASIK), your refractive prescription should fall within the following:
- Up to -8.0 diopters of nearsightedness, or
- Up to -3.0 diopters of astigmatism, or
- Up to -9.0 diopters nearsightedness with astigmatism; and,
- The amount of nearsightedness with or without astigmatism in your eye did not change by more than 0.5 diopters during the year before your pre-operation examination.
If your prescription is for vision measured as high as to -20.0 diopters of nearsightedness, implantable contact lenses are recommended instead over LASIK.
Other Factors that Influence Qualifications for LASIK
Your eye’s prescription is not the sole indicator as to whether you are eligible for LASIK. Generally, the following factors also need careful consideration before surgery:
- The thickness of cornea. Performing laser vision correction on a cornea that is too thin or has an extremely irregular and misshapen surface (keratoconus) could compromise outcomes and possibly result in vision deterioration.
- Pupil size. LASIK done on pupils that are unusually large could increase your risk of side effects such as glares and halos.
- Stability of prescription. Your prescription should be stable for at least 12 months before the procedure. For this reason, teens and younger folks are not good LASIK candidates until their eyes have “settled down” into a stable prescription.
- Overall eye health. You don’t suffer from dry eye syndrome, cataracts, or glaucoma.
- Pregnancy or lactation. Medications used during and after LASIK may pose a risk to your child while you’re pregnant or nursing. Hormonal shifts during pregnancy can also trigger dry eye symptoms.
Poor Eyesight is Not the Only Factor for LASIK
Although there may be factors that may keep a patient from being a good candidate for LASIK immediately, the good news is that patients who were not deemed good candidates years ago can now enjoy clearer vision as new techniques are refined and introduced.
Find out if your prescription and overall eye health make you a good laser vision surgery candidate by scheduling a consultation with one of our LASIK specialists. A thorough in-person assessment and evaluation is the best way to gauge whether or not LASIK is for you.