What is a Contact Lens Evaluation (and why do I have to pay extra)?

Have you ever found yourself wondering why you have to pay extra to have a prescription for contact lenses?   My patients often tell me the same things:  their prescription hasn't changed in years, they like the comfort of their lenses, they just want their same prescription again.  At my office, I never renew a prescription without evaluating the contact lens on the eye, testing vision, and checking the eye carefully for any signs of damage from contact lens wear.  These actions are the contact lens evaluation, an additional piece of the exam that glasses wearers would not need.  Typically your vision insurance has a separate copay for a contact lens evaluation because they also understand that it is a separate part of the exam.  What are the components of a thorough contact lens evaluation?

1) Evaluation of the cornea without contact lenses 

Neovascularization via

In the slit lamp microscope, your doctor will be painstakingly checking the corneal tissue.  The cornea is the clear surface over top of the iris where your contact lens sits.  The tissue functions like a window, allowing light to pass through into the eye.  Contact lenses can cause major damage to the corneal tissue if they are fitting too tightly, too loosely, or not allowing enough oxygen to pass through to the cornea underneath.  I look for several tell-tale signs of contact lens complications.  Are there small scars in the otherwise clear corneal tissue?  Those could be from old bacterial infections or areas where the corneal tissue died from lack of oxygen.  Are there blood vessels growing into the corneal tissue?  This is called corneal neovascularization and is a hallmark of poor oxygen passage.  The cornea should be clear, and if blood vessels are invading the cornea, you not only have a "red rimmed" eye appearance, you have cloudy corneal tissue and areas that are at higher risk for infection.  Scar tissue and blood vessel growth means that we need to either change your contact lens to a higher oxygen material, or change how you are wearing your lens if you are not following federal guidelines for your particular contact lens material.

2) Prescription Selection and Vision Evaluation

Your glasses prescription helps guide the contact lens powers that your doctor selects, but your glasses Rx is NOT the same as your contact lens prescription.  If you have a high prescription in glasses, or if you have astigmatism, your doctor performs mathematical calculations to change the glasses Rx into an appropriate contact lens power.  Glasses sit on your face, but contact lenses sit on your eye.  The higher your prescription, the more that difference in distance matters.  You should ALWAYS have your vision checked in your contact lenses at some point during your eye examination.  I also trial different lenses over the contact lenses to make sure I don't need to go stronger or weaker with the correction to improve visual acuity.

3) Evaluation of the Contact Lens on the Eye

The contact lens must fit the eye properly to offer safe,
clear vision correction.  via

I often tell my patients to think of their contact lens like a shoe.  They come in all different shapes and sizes (there are a ton of brands out there!), and your contact lens needs to be shaped correctly to properly fit your unique eye.  There is no one contact lens brand that will work for every patient.  Think about how much your foot hurts when your shoes are too tight or too loose.  And that is your foot!  The eye is so much more delicate and vital to your life!  If your contact lens fits improperly, you are at higher risk of scarring and infection.  The lens should move a little as you blink to let oxygen and tears pass underneath, but not too much as to be easily dislodged.  Even if you have worn that brand for years, the shape of your cornea may change with time and the fit must still be carefully evaluated every time you see your doctor.

The biggest take home?  Your doctor is not trying to waste your time by evaluating contact lenses on your eye.  I often meet with annoyance when I ask my patients to put on contact lenses for me to evaluate when they have "worn these for years!".  But after a discussion of the importance, my patients understand that I am just making sure that they are safely wearing contact lenses for the rest of the year.  Contact lenses are a medical device, and they are sitting on one of the most sensitive and vital structures of your body all day long.  It requires a vigilant doctor and a vigilant contact lens wearing patient to prevent potential permanent damage to the eye when you wear contact lenses.