What Tests Are Done Before LASIK? A Complete Guide to Your LASIK Evaluation
If you’re considering LASIK in Saginaw, you may wonder what happens before the actual procedure. Will your doctor simply check your prescription, or are there other tests involved?
A LASIK evaluation is much more comprehensive than a routine vision test. Before recommending surgery, your eye doctor needs to determine whether your eyes are healthy, whether your prescription is appropriate and stable, and whether your corneas can safely undergo laser reshaping.
At MiVision Eye Care in Saginaw, MI, refractive evaluations are part of the process of determining whether LASIK or another vision correction option is appropriate for you.
Here are the tests you can typically expect during a pre-LASIK evaluation.
Why Are Tests Needed Before LASIK?
LASIK changes the shape of the cornea to correct refractive errors such as nearsightedness, farsightedness, and astigmatism. Because the procedure permanently reshapes corneal tissue, your surgeon needs detailed information about your eyes before treatment.
The evaluation helps your doctor determine:
- Whether your prescription is stable
- Whether your cornea is healthy and has an appropriate shape
- Whether your cornea is thick enough for the planned treatment
- Whether you have dry eye or other ocular-surface problems
- Whether there are signs of conditions that could make LASIK unsafe
- Which vision correction procedure may be most appropriate for you
The FDA recommends a thorough eye examination and baseline evaluation before LASIK to determine whether someone is a suitable candidate.
1. Visual Acuity Testing
You will have your vision measured both without correction and with your current glasses or contact lens prescription.
This is the familiar eye-chart test where you read letters or symbols from a specific distance.
Your doctor uses these measurements to establish your current level of vision and determine how much correction you receive from glasses or contacts.
Visual acuity testing is one of the standard components of a refractive surgery evaluation.
2. Refraction Testing
Your eye doctor will carefully measure your prescription to determine the amount of nearsightedness, farsightedness, or astigmatism you have.
You may undergo a manifest refraction, where you look through different lenses and tell your doctor which options make the letters clearer.
In some cases, a cycloplegic refraction may also be performed. This test uses eye drops to temporarily relax the focusing muscles of the eye, allowing your doctor to obtain additional information about your prescription.
Accurate refraction is particularly important before refractive surgery because the measurements are used to plan your treatment.
3. Corneal Topography or Corneal Mapping
This is one of the most important tests before LASIK.
Corneal topography creates a detailed map of the surface of your cornea. Think of it as creating a "map" of the cornea's shape and curvature.
The test can help your surgeon identify irregularities that may not be detected during a standard eye exam.
It can also help detect conditions such as keratoconus or irregular astigmatism, which may affect whether LASIK is appropriate.
The American Academy of Ophthalmology recommends computerized corneal topography or tomography as part of the refractive surgery evaluation, and preoperative topography is routinely used to screen for corneal abnormalities.
Why does corneal mapping matter?
LASIK reshapes the cornea. Your surgeon therefore needs to know exactly what your cornea looks like before deciding whether and how it can safely be treated.
If testing shows that LASIK isn't the safest option, your doctor may discuss alternatives such as PRK or EVO ICL, depending on your individual eye health and anatomy. MiVision offers LASIK/PRK evaluations as well as Implantable Collamer Lens (ICL) options.
4. Corneal Thickness Measurement (Pachymetry)
Another important measurement is corneal thickness, also called pachymetry.
During LASIK, a controlled amount of corneal tissue is reshaped. Your surgeon needs to know how thick your cornea is before treatment to determine whether there is enough tissue for the planned procedure.
Thin corneas can affect LASIK candidacy. The FDA specifically identifies corneal thickness as one of the factors that should be considered when determining whether someone is a suitable candidate.
Corneal thickness is also evaluated alongside the corneal shape and other measurements rather than being considered by itself.
5. Dry Eye and Tear Film Testing
Your tear film plays an important role in the quality and comfort of your vision.
Before LASIK, your doctor may evaluate your eyes for dry eye and other ocular-surface problems.
Depending on your symptoms and examination, testing may include measurements of tear-film stability or tear production. Some evaluations may also use corneal staining or other specialized tests to identify areas of dryness or irritation.
This matters because pre-existing dry eye can increase the risk of experiencing dryness after LASIK.
If significant dry eye is identified, your doctor may recommend treating it before moving forward with surgery.
6. Slit-Lamp Eye Examination
A slit-lamp examination allows your eye doctor to examine the structures at the front of your eye under magnification.
Your doctor can look at areas including the:
- Cornea
- Conjunctiva
- Eyelids
- Iris
- Lens
- Other structures at the front of the eye
This examination can help identify conditions such as corneal abnormalities, inflammation, cataracts, or other problems that could affect your treatment options.
A comprehensive eye examination is an important part of determining whether LASIK is appropriate.
7. Eye Pressure Testing
Your eye pressure may also be measured using tonometry.
This helps your doctor screen for elevated intraocular pressure and evaluate your overall eye health.
Eye pressure measurement is included in standard preoperative refractive surgery evaluations.
An abnormal result does not automatically mean you cannot have vision correction surgery. Instead, it may mean that your doctor needs to investigate the finding further before making a recommendation.
8. Pupil Size Measurement
Your doctor may measure the size of your pupils, including how they respond under lower-light conditions.
Pupil measurements can provide additional information when discussing potential postoperative visual symptoms such as glare or halos.
However, pupil size is only one part of the overall evaluation and does not determine LASIK candidacy by itself. The relationship between pupil size and postoperative visual symptoms is still debated.
9. Dilated Eye Examination
A dilated examination allows your doctor to look more closely at the back of your eye, including the retina and optic nerve.
This is important because LASIK treats the cornea, but your doctor still needs to make sure there aren't other eye conditions that could affect your vision or make surgery inappropriate.
A comprehensive pre-LASIK evaluation may include a dilated fundus examination.
10. Wavefront Testing
Some patients may undergo wavefront analysis as part of their LASIK evaluation.
Wavefront technology can measure certain optical imperfections in the eye that aren't captured by a standard glasses prescription.
These measurements may help the surgeon understand the quality of your vision and determine whether a customized treatment approach may be appropriate.
Wavefront analysis is among the additional diagnostic tests that may be used during refractive surgery evaluations.
11. A Review of Your Medical and Eye History
Not every part of a LASIK evaluation involves a machine.
Your doctor will also want to know about your medical and eye history, including:
- Previous eye surgeries or injuries
- Current and previous eye conditions
- Medications
- Allergies
- Previous changes in your prescription
- Contact lens use
- Dry eye symptoms
- Other health conditions that could affect healing
The FDA recommends discussing your past and current medical and eye conditions and all medications with your doctor before LASIK.
Your doctor may also ask about your goals and expectations. That's important because LASIK isn't simply about achieving a particular number on an eye chart. Your desired lifestyle and visual needs can also influence which treatment is most appropriate.
Do You Need to Stop Wearing Contact Lenses Before LASIK Testing?
Usually, yes.
Contact lenses can temporarily change the shape of the cornea, which can make preoperative measurements less accurate.
The amount of time you need to stop wearing contacts depends on the type of lenses you use and your doctor's instructions. The FDA advises contact lens wearers to switch to glasses before the baseline evaluation because contacts can affect corneal shape for a period of time after they are removed.
Your eye doctor will tell you exactly how long you should be out of your lenses before testing.
What Happens If a Test Shows I'm Not a LASIK Candidate?
Not being a LASIK candidate doesn't necessarily mean you have no options for reducing your dependence on glasses or contacts.
Depending on the reason LASIK isn't recommended, your eye doctor may discuss alternatives such as PRK or EVO ICL.
For example, PRK does not create the same corneal flap used in LASIK and may be considered for certain patients who aren't ideal LASIK candidates. EVO ICL is another option that corrects vision without reshaping the cornea.
The right procedure depends on your prescription, corneal measurements, eye health, lifestyle, and other individual factors.
How Long Does a LASIK Evaluation Take?
The length of your appointment can vary depending on the number of tests you need and whether your eyes require additional evaluation.
Because a LASIK consultation involves more than simply checking your prescription, you should expect a more comprehensive evaluation than a routine glasses or contact lens exam.
Your doctor may also recommend additional testing if something requires further investigation.
What Should You Bring to Your LASIK Consultation?
Before your appointment, it can help to have:
- Your current glasses
- Information about your contact lenses
- Your previous eye-care records, if available
- A list of your medications
- Information about previous eye surgeries or conditions
- Questions about LASIK and its alternatives
Most importantly, be prepared to discuss what you want to achieve with vision correction.
What Happens After the Tests?
Once your testing is complete, your ophthalmologist will review the results with you.
The goal isn't simply to determine whether you can have LASIK. It's to determine whether LASIK is a safe and appropriate choice for your specific eyes.
Your doctor may recommend LASIK, suggest another vision correction procedure, recommend treatment for an eye-surface condition first, or determine that refractive surgery isn't appropriate.
You should have an opportunity to discuss the potential benefits, risks, alternatives, expected results, and any questions you have before making a decision.
Get a LASIK Evaluation in Saginaw, MI
If you're considering LASIK, the first step is a comprehensive evaluation—not a commitment to surgery.
At MiVision Eye Care, our refractive evaluation helps assess your prescription, eye health, corneal measurements, and other factors that can affect your vision correction options. MiVision provides LASIK and PRK evaluations in Saginaw and serves patients throughout the Great Lakes Bay and Mid-Michigan region.
If LASIK isn't the best fit for your eyes, other options may be available. The goal is to find the vision correction approach that is safest and most appropriate for you.
Ready to find out if LASIK may be right for you? Schedule a consultation with MiVision Eye Care in Saginaw, MI, today.