Contact lenses are classified as medical devices and require a valid prescription from a licensed eye care professional, such as an optometrist or ophthalmologist. This requirement exists because a contact lens rests directly on the surface of the eye, and an improper fit or material choice can lead to discomfort, infection, or serious eye damage. Obtaining a contact lens prescription involves a comprehensive health check and precise measurements of your eye’s unique surface. The process is standardized to ensure the lenses provide optimal vision correction and maintain the long-term health of your eyes.
Scheduling the Comprehensive Eye Exam
The first step in getting fitted for contact lenses is scheduling a comprehensive eye health examination. This initial appointment is a prerequisite for a contact lens fitting and is more extensive than a simple vision screening. During this exam, the eye care professional checks for underlying conditions that might interfere with successful contact lens wear, such as severe dry eye, corneal abrasions, or eye infections.
The exam focuses on the overall health of the eye’s internal structures and anterior surface, confirming that your eyes are medically suitable for a contact lens. A glasses prescription alone does not contain the specific parameters needed for contact lenses. The doctor will perform a refraction to determine the necessary vision correction power, which is the starting point for calculating the final lens power.
The Contact Lens Fitting and Measurement Process
The contact lens fitting is a specialized procedure that occurs after the initial eye health check confirms suitability for lens wear. This process involves taking precise measurements to match the lens curvature and size to your individual eye shape. These measurements are crucial because a lens that is too tight or too loose can restrict oxygen flow or cause corneal irritation.
A primary measurement is the curvature of the cornea, typically assessed using keratometry or corneal topography. Keratometry measures the curvature of the central cornea, while corneal topography maps thousands of points across the entire surface to create a detailed map of your eye’s shape. This detailed mapping is important for irregular corneas or those requiring specialized lenses like toric lenses for astigmatism.
The eye care professional also measures the horizontal visible iris diameter, which helps determine the overall diameter of the contact lens needed for proper coverage and stability. A tear film evaluation is performed to assess the quality and quantity of your natural tears. Adequate lubrication is necessary for comfortable wear, and an insufficient tear film may lead the doctor to select a specific lens material designed to retain moisture. For complex vision needs, such as astigmatism or presbyopia, specialized designs like toric or multifocal lenses are selected, requiring precise measurements and lens positioning checks.
Trial Lenses and Insertion Training
Following the measurement process, you will be provided with trial lenses that incorporate the initial determined specifications. These lenses allow the eye care professional to assess the lens-to-eye relationship. The lens is checked for proper movement on the eye, ensuring it slides slightly when you blink, which is necessary for tear exchange and oxygen delivery to the cornea.
A significant part of this stage is the hands-on insertion and removal training session, particularly for new wearers. A trained technician will guide you through the proper techniques for safely putting the lenses into your eye and taking them out. This training also includes hygiene instruction, emphasizing the importance of washing hands before handling the lenses and using only approved cleaning and storage solutions. You must demonstrate proficiency in handling the lenses before being allowed to take them home.
You are then given a supply of trial lenses to wear for a specified period, often a few days to a week, to evaluate comfort and visual clarity in your daily life. This trial period is essential because the eye’s response to the lens material and fit cannot be assessed in a short office visit. The doctor will ask you to return for a follow-up appointment with the trial lenses in your eyes to check the fit and vision after extended wear.
Finalizing the Prescription and Follow-Up
The final step is the follow-up appointment where the eye care professional assesses your experience with the trial lenses and makes any necessary adjustments before finalizing the prescription. If the fit is stable, the vision is clear, and the eyes show no signs of irritation, the prescription is issued. A contact lens prescription is distinct from a glasses prescription, containing specific details such as the base curve, the lens diameter, the power (in diopters), and the material or brand name.
Federal regulations require the prescriber to provide you with a copy of your completed prescription. This prescription is legally required to purchase contact lenses and includes an expiration date, which is typically one year from the date of the exam. Annual follow-up examinations are required to renew the prescription, ensuring that your eye health is continually monitored for any changes that might affect your ability to wear contacts safely.