Contact lenses slightly alter the shape of your cornea. You should stop wearing them before your initial evaluation so your eyes can return to their normal shape and be measured for treatment. You’ll also need to stop wearing them before surgery.

The amount of time your contacts need to be removed may vary depending on the type of lenses you use and your surgeon’s technology and preferences.

The following are general guidelines, but your doctor may recommend something different. Be sure to talk with your doctor before your initial evaluation. If you wear:

• Soft contact lenses-stop use for two weeks
• Rigid gas permeable (hard) lenses-stop use for a month

A thorough eye examination allows your doctor to determine if you are eligible for presbyopia laser vision correction and prevent complications. Also, be sure to tell your doctor if you have night vision or dry eye symptoms or any other noticeable eye symptoms. Your doctor can then advise you of ways to reduce your risk of side effects.

Your doctor may perform a number of tests and ask you for detailed information about your personal eye health history, including your family history, your use of glasses and contacts and your professional and lifestyle needs.

Although your doctor may also perform additional tests, your doctor will usually:

• Test your corrected and uncorrected vision and diagnose the amount of visual error in each eye.
• "Map" the shape of each cornea to see how it contributes to refractive errors (higher order aberrations may also be mapped if Wavefront-guided LASIK is being considered).
• Screen for possible diseases of the eye, including glaucoma, cataracts, complications from diabetes and any corneal irregularities or abnormalities.
• Measure corneal thickness (which will determine if or how much LASIK correction is possible), pupil size in a variety of lights and eye movement.
• Examine the eyelids for inflammation, irregularities or other conditions.
• Assess the back of the eye with the pupil fully dilated to detect possible eye and systemic disorders.

Your doctor will then review the results of your eye exam with you to discuss your eligibility as well as any additional testing that may be necessary.

Your doctor may also ask about how well you learn new skills and adjust to change-some people are more comfortable adjusting to monovision than others. If you have never tried monovision before, your doctor may recommend that you try it in advance of surgery with special contact lenses, to confirm that you will be able to adjust easily.

If you have any questions about why a test is omitted or included, discuss them with your doctor. You deserve to be satisfied with your evaluation before proceeding with surgery.

If you have resumed wearing your contact lenses after your initial eye exam, your surgeon will ask you to stop wearing them again for a similar amount of time before your surgery.

The day before surgery, your doctor may ask you to stop using creams, lotions, make-up and perfume.

You may be asked to scrub your eyelashes for a period of time to reduce bacteria and get rid of residues and debris along the lashes.

Occasionally, patients may also be given a regimen of artificial tears, warm compresses, gels and other prescription medications to treat preexisting dry eye or eyelid inflammation (called blepharitis).

You should arrange for transportation to and from your procedure as well as your first follow-up visit, usually the day after surgery. (Many patients feel able to drive the day after surgery, but it is wise to be prepared in case you do not.)

On the day of surgery, you should be sure to eat a light meal ahead of time.

Most people have little or no pain during LASIK surgeries like presbyopia laser vision correction, though some discomfort is possible. You’ll be awake for the procedure and usually only the eyes need to be numbed-usually with anesthetic drops. In some cases, a doctor may give a mild oral sedative, as well.

Once you’re positioned properly under the LASIK machine, a stabilizing device called a speculum helps keep your eye open. Another device applies suction pressure to hold your eye still for treatment. This also causes your vision to darken for a few seconds.

Your surgeon will use an advanced automated device-either a microkeratome blade or a femtosecond laser-to create a small, circular flap in the cornea. Most patients do not see this occur and feel little or no pain because the eye is anesthetized.

Next, the surgeon will gently lift the flap back and you will focus on a target light for a short time as the excimer laser sends short, invisible pulses of cool ultraviolet light to reshape your cornea.

The laser removes tiny amounts of corneal tissue, following the exact map of your eye that was created during your initial examination. This is called ablation.

You may hear a steady clicking sound while the laser operates, and you may notice a mild odor. Most lasers have modern trackers which automatically follow eye movements to help keep the procedures centered. The surgeon will watch your eye the entire time and can turn off the laser at any point.

When the treatment is done, the flap is laid back in place, to protect the eye and speed healing. You will rest for a little while and then, if you are having the other eye operated on, the procedure will continue.

Depending on your refractive error and other considerations, your doctor may instead want to perform surgery on the other eye about one week later.

Patients are given a topical anesthetic (eye drops) to numb the eye, so they experience little or no pain during the procedure. The microkeratome-the instrument the surgeon uses to create the flap-and the laser do not cause any pain or discomfort, but there can be a moment of pressure when the surgeon applies the vacuum ring at the beginning of surgery. Many patients describe a mild burning sensation, such as after opening the eyes while swimming in chlorinated water, for a few hours after surgery. After the first few hours, this uncomfortable feeling usually subsides.