Contact Lens Exam

What the Doctor Does During a Contact Lens Exam

…and why you still need it even if you already had an Eye Exam

A contact lens fitting is a separate medical evaluation that ensures contacts are safe, comfortable, and appropriate for your eyes. It goes far beyond checking your vision — it evaluates how a medical device (the contact lens) interacts with your eye.    Depending on your medical history, the doctor may do some or all of the following:

 1. Evaluates Your Eye Health

Before any lens goes on your eye, the doctor checks for conditions that affect contact lens wear, such as:

• Dry eye
• Allergies
• Corneal health
• Eyelid issues (like blepharitis)
• Tear film quality

These factors determine whether contacts are safe for you and what type will work best.
 

2. Takes Specialized Measurements (Not Included in an Eyeglass Exam)

Contacts must match the anatomy and physiology of your eye. These measurements ensure the lens fits properly and won’t cause irritation or long-term damage.
 

Corneal Curvature (Keratometry)

Measures how steep or flat the front of your eye is.

• Too steep → lens can “suction cup” and reduce oxygen flow
• Too flat → lens moves excessively and causes irritation. This determines the base curve of your lens.

Corneal Topography (if needed)

Creates a detailed map of your cornea’s surface.

• Important for astigmatism, post-surgery eyes, or irregular corneas
• Helps select the right lens design and stability

Horizontal Visible Iris Diameter (HVID) (if needed)

Evaluates the width of the colored part of your eye.

• Determines the diameter of the lens
• Ensures the lens fully covers the cornea properly.

Pupil Size

Measured in bright and dim light.

• Affects night vision, glare, and halos
• Important for multifocal and specialty lenses

Tear Film Evaluation

Contacts rely on your natural tears for comfort and clarity. The doctor assesses:

• Tear quantity
• Tear quality
• Tear breakup time (TBUT)

What Tear Breakup Time (TBUT) Is

TBUT measures how long your tears stay smooth and stable on the surface of your eye before they start to evaporate or “break up.”

• A dye (usually fluorescein) is placed in your tears.
• You blink once, then hold your eyes open.
• The doctor times how long it takes for the first dry spot to appear.

A short TBUT means your tears evaporate quickly, which can cause:

• Dryness
• Blurry vision
• Contact lens discomfort
• Reduced wearing time

This measurement helps determine whether you need:

• A specific lens material
• A different replacement schedule
• Dry eye treatment before wearing contacts

Lid Position and Blink Pattern

Your eyelids influence how the lens moves and stays centered.

• Affects stability
• Especially important for toric and multifocal lenses

Baseline Corneal and Conjunctival Health

The doctor documents the condition of the cornea and surrounding tissues to monitor for future contact-related changes.
 

3. Selects the Correct Lens Type

Based on your measurements, eye health, and lifestyle, the doctor chooses:

• Soft or rigid gas-permeable lenses
• Daily, biweekly, or monthly disposables
• Toric lenses for astigmatism
• Multifocal lenses
• Specialty lenses

Even if you’ve worn the same brand for years, the doctor must confirm it’s still appropriate.
 

4. Test the Lens on Your Eye

You try on trial lenses so the doctor can evaluate:

• Centering
• Movement with blinking
• Rotation (for astigmatism lenses)
• Comfort
• Vision clarity

This ensures the lens is physically safe for your cornea.

5. Examines the Fit Under a Microscope

Using a Slit Lamp (BioMicroscope), the doctor checks:

• Lens edges
• Tear exchange
• Corneal response
• Early signs of irritation or hypoxia

This is the medical safety check that a glasses exam does not include.

6. Finalizes Your Contact Lens Prescription

A contact lens prescription includes:

• Brand
• Base curve
• Diameter
• Power
• Replacement schedule

This is legally separate from a glasses prescription because it requires different measurements and safety evaluations.
 

7. Provides Training (If needed)

For new or returning wearers, the staff teaches:

• Insertion and removal
• Cleaning and storage
• Safe wearing habits
• Warning signs of problems

 

Summary: Why You Need a Contact Lens Fitting Even if You Already Had an Eye Exam

A standard eye exam checks your vision and overall eye health. A contact lens fitting checks how a medical device interacts with your eye.

Even longtime wearers can develop:

• Dryness
• Inflammation
• New Astigmatism
• Corneal changes
• Contact-related complications

These issues can only be detected during a fitting.

Do I Have to Pay for the Fitting, even if my Contact Lens Prescription Didn’t Change?

Yes. The fitting fee is for the evaluation and the doctor’s time spent with you, not for changing the prescription.

You’re paying for:

• Specialized measurements
• Trial lenses
• The doctor’s time evaluating the fit
• The legally required contact lens prescription
• The medical assessment of how the lens interacts with your eye

Even if everything stays the same, the doctor must still perform the fitting steps to ensure the lenses remain safe for you.