Why Does the Eye Doctor Dilate Your Eyes?
At Colorado Eye Surgeons, one question that patients often ask Dr. Pennington is, “why do we need to dilate my eyes”. We certainly understand that dilating the eyes can be a hassle both from a time management perspective and how it affects your vision after your appointment. To understand why we dilate, let’s first describe the anatomy of the human eye.
Anatomy of the Human Eye
Our eyes consist of many parts and generally doctors and surgeons will divide the eye into two basic compartments, the anterior and posterior portions (sometimes discussed as the anterior and posterior chambers). Let’s take a closer look at the two portions of the eye.
The anterior portion of the eye consists of conjunctiva, sclera, cornea, anterior chamber, iris, and pupil. When we look at a person’s eye without a microscope this is all that is visible. The conjunctiva is a clear tissue that overlies the sclera which some people refer to as “the whites of the eye”. The cornea is the clear dome that helps refract (bend) light coming into the eye. If you are a contact lens wearer, the contact lens sits on your cornea. After light enters the eye through the cornea, it then passes through the anterior chamber which is a fluid filled area on its way to the pupil. The pupil is the dark area in the center of your iris. The iris is what makes up the “color” of a person’s eye. There isn’t any tissue in the pupil, rather it is empty space that is not reflecting light back which gives it the black appearance.
The posterior portion of the eye typically is divided up between the vitreous, the retina, and the choroid, but for this discussion we will include the lens as well. This area of the eye for the most part is not visible when you are looking at a person’s eyes outside of a doctor’s exam room. After light passes through the pupil, it encounters the lens. The lens will bend the light again much like the cornea does, and then light continues through vitreous until it hits the retina. At the retina the light is turned into signals that are sent to the brain to be processed as visual information. The choroid underlies the retina, but for purposes of this discussion doesn’t need to be addressed.
Why Does The Eye Doctor Dilate the Eye?
Finally, for the explanation of why we dilate the eyes. The usual answer is so the doctor is able to view the posterior portion of the eye. In order to see all of the tissue in the posterior portion of the eye, we need a very wide (a.k.a dilated) pupil in order to have a proper angle for visualization.
So, in short, this is why an ophthalmologist or an optometrist will dilate your eyes.
Occasionally there are other reasons to do so that deal with your glasses or contacts prescription, but for a standard eye exam, it is usually to assess the whole health of the eye. At Colorado Eye Surgeons, we have technology that can give a view of the retina without dilating your eyes. During your visit, it is good to ask our doctors about your options for assessing the health of your retinas.
