A comprehensive eye examination assesses the sharpness of your vision and evaluates the overall physical health of your eyes. Whether you should wear your glasses depends entirely on which part of the exam the eye doctor is performing. The procedure first analyzes the effectiveness of your current vision correction, then determines any necessary changes, and finally checks for underlying health conditions. Understanding this flow guides you on when to keep your eyewear on and when to take it off.
The Initial Assessment
The initial portion of your exam requires you to wear your current glasses or contact lenses to establish your baseline visual acuity. The doctor needs to know precisely how well you are seeing with your present correction to understand if your vision has changed. During this step, the eye care professional uses a lensometer to measure the exact power of your current eyeglass lenses. This measurement provides an objective starting point for comparison with the new prescription determination. Your doctor will also ask about your daily visual needs, any discomfort, and your health history.
Determining the New Prescription
Once your baseline is established, your glasses must be removed to accurately determine the precise lens power needed to sharpen your vision. This process, known as refraction, is a subjective test that relies on your feedback. The eye doctor places a large instrument called a phoropter in front of your eyes, which contains a series of different lenses. During refraction, you look through the phoropter at an eye chart while the doctor rapidly switches between lens combinations, asking, “Which is clearer, one or two?” This technique refines the spherical, cylindrical, and axis components of your prescription to correct refractive errors like nearsightedness, farsightedness, and astigmatism.
Health Checks and Dilation
After measuring your visual acuity and determining your prescription, the doctor conducts a thorough physical examination of the eye structures, requiring your glasses to be removed. Tools like the slit lamp microscope are used to examine the cornea, iris, and lens, checking for issues like cataracts or corneal abrasions. Eye pressure is also measured using tonometry, a screening test for glaucoma. A significant part of the health check is the fundus examination, which involves looking at the back of the eye. To get the clearest view of the retina and optic nerve, the doctor may administer dilating eye drops that temporarily widen your pupils, making it easier to detect signs of diseases like diabetic retinopathy or macular degeneration.
Special Considerations for Contact Lens Wearers
Patients who primarily wear contact lenses have a slightly different procedural requirement for their eye exam. You should arrive wearing your contact lenses so the doctor can first assess their fit and how they interact with the eye’s surface. Using the slit lamp, the doctor checks for proper lens movement and any potential irritation to the cornea. However, contact lenses must be removed for the refraction and the comprehensive internal health checks, just as glasses are. If you are having a specific contact lens fitting, bring a contact lens case, solution, and your backup pair of glasses, as you may not be able to comfortably reinsert the lenses until the dilation effects have worn off.