At your full eye exam, the word “dilation” may have been stated or overheard. This procedure may be a mystery to many, and the indications for it may vary. Below is a description of what it is, why it is performed, and when it will be avoided.
Dilation, at our office, refers to the procedure in which the pupil, the black circle at the center of the eye that allows light to enter, is enlarged. This is done through an eye drop that targets and inhibits specific receptors in the parasympathetic system.
There are multiple drops available, often varying according to the underlying purpose. The eye drop also has a secondary function of temporarily halting the focusing system within the eye that is responsible for clear near vision, also known as accommodation.
The most common reason for dilation is to better assess the retina at the back of the eye. Though our optometrist can view the back of the eye through the pupil with or without this procedure, dilation results in a larger pupil and allows our optometrist to view further into the periphery.
This is also conducted if you present to the office with suspicious symptoms like flashing lights in your vision; dilation allows our doctor to extensively assess and rule out any abnormalities. Furthermore, it may be completed to get a better look at other structures within the eye such as the lens in the case of cataracts.
The effects and duration of the drop vary from person to person with eye colour as a common factor, and they also depend on the concentration used by the doctor.
It can be expected that the effects of the drop can last for at least a few hours. A higher concentration may be required if our doctor feels that the lower concentration does not provide adequate dilation.
The other reason that the eyes may need to be dilated is for a cycloplegic exam. In this case, the halting of the accommodative system is the most important aspect.
This is conducted on patients that require a more precise measurement of their prescription. Our optometrist may decide to perform this procedure because they suspect that the accommodative system may be overactive and affecting the measurements of one’s prescription. The eye drop used for this procedure has effects that often resolve before the end of the day.
Dilation drops may also be used in myopia control. In this case, a specific low concentration drop is used once daily to slow down the progression of myopia during childhood. Lastly, a dilation drop may be prescribed to help with pain control in conditions such as uveitis.
There are some cases when our optometrist will decide against dilation. One of those reasons may be anatomical.
The drainage structure for the fluid in the eye, known as the anterior angle, varies in size. In some patients, it may be very small, and during dilation, there is a higher risk for the angle to narrow and close.
This can result in an increase in intraocular pressure that can cause nausea, headaches, and more severely, damage to the eye. Another reason that dilation may be avoided is in certain traumatic injuries. Using a dilation drop can harm the eye more and thus will be avoided.