When it comes to pupil evaluation, accuracy is key. Pupils can be evaluated for size and shape to help determine the cause of certain eye problems and brain injuries. This can provide valuable information to the doctor and help the patient. This article will explain these evaluations, how they are done, and why they are important for treating certain brain injuries.
What is a pupil?
Eye pupils are the openings in our eyes that allow light to enter. Light rays exit our eyes through these ocular versions of gills, also known as iridal valves or slits—thus their name “windows.” When objects enter the retina at right angles (binocular vision), they fill both pupil openings and create an image in them.
Why Is a Pupil Evaluation Important?
Optometrists use eye pupil size and shape (or dilatation) as one of the first quick tests to examine a person’s eyes. In children, certain neurological problems can cause pupils to be “abnormally small or large,” making distant objects not bright enough for them to focus on clearly (a condition known as amblyopia, “immobilized” vision).
Many other eye disorders and conditions also require diagnosis by an optometrist following a detailed examination of pupils by an ophthalmologist as a way to confirm the diagnosis and guide treatment. For instance, amblyopia is caused when the light source (screen, sun, or lamp) is too intense for reading at close range; if this condition goes on long enough, it can cause serious damage to the eyes.
Different Types of Eye Pupil Evaluation
- Pupillometry: This is the most commonly used method of pupil reactivity. A measuring instrument called a pupilometer (a hand-held, battery-powered device) measures how big or small each pupil actually is and what it does when you move your eyes around to aim different objects at it. This test can also be conducted on those in a coma, although their eye movements are not activated.
- Applanation Tonometry: An applanation tonometer is a test device that uses graded disks to measure pupils’ vertical and horizontal diameters. The amount of water in each eye or both eyes may be measured at different pressures, creating corresponding indentations on plastic grading wheels.
- Corneal Topography: This test uses an ophthalmoscope (a simple telescope) to simultaneously observe the shape, size, and movement of a patient’s cornea. These two details can be used to determine if there are any changes in vision due to other causes aside from optical problems with the eyes.
- Autorefraction: This method can be used with those who cannot read or write. With this test, an image of your retina is taken (with a laser gun) and then transmitted to the ophthalmologist’s computer as greyscale data points, forming a two-dimensional map. The resulting digital design is read by specialized software that allows you to visualize where each point falls along with the three-dimensional cornea in relation to the depth of the eye.
- Dilated Pupillary Exam: This can be performed by taking a picture of the back wall of the patient’s eye via light or camera and looking at it through an eyepiece that goes in one eye. The dominant hand holds a pen for reference to show where each pupil is located, leading to measuring its size either using indirect measures like a coverslip reflection test or direct measurement testing with special opaque overlays placed on the paper behind the observer’s head to represent light being reflected from the eye.
- Visual Field Test: The standard test used to grade visual acuity involves the patient being asked, either with or without glasses, which elements of a pattern appear. The easiest way to accomplish this task is by inspecting horizontal and vertical lines simultaneously, one eye at a time, while focusing on shifting the chart’s position between two locations. If you notice that one line has changed location relative to its neighbour, return your attention to it before setting off for another point.
Accuracy in pupil evaluation is essential for diagnosing and treating ocular diseases. By having an accurate assessment of the pupillary light reflex, physicians can make more informed treatment decisions.