Eye exams have come a long way over the decades, and are very different from the ones your parents and grandparents might have had, though the core components are similar.
In a city like Toronto, eye exams that are offered from office to office, optical to optical can vary a lot, from the very quick and basic to a more thorough exam much like going to your family physician for a yearly physical.
So what are some of the things you’ll come across in the modern eye exam? In this article we will go over:
The Snellen Chart
The eye chart, officially known as the Snellen chart, is typically the first thing people think of when one says the phrase “eye exam”. The chart has several rows of letters of different sizes, with the largest letter on top and descending in size as you travel down the chart. Many patients recognize it for the big “E” at the top.
The Snellen chart is used to measure visual acuity. Its creator, Dr. Herman Snellen, created the chart in the 1860’s to help measure his patient’s visual ability when compared to what a “standard”, “healthy” or “emmetropic” eye is able to read from specific distances. The standard distance for acuity is six meters, or 20 feet, and by adjusting the size of the letters on the chart, it can simulate what something would look like at further or closer distances. The patient is asked to read lines on the chart, and their ability to do so is compared to the results of the “standard” eye; when paired together, the result is the patient’s visual acuity.
For example, if the smallest line a patient can read on the chart is the one designated as “20/40”, then that means that the patient must be 20 feet away to read what a “standard” eye can read clearly at 40 feet. This test is done with and without visual aid devices (glasses, contact lenses, etc.), and is used in conjunction with the phoropter to determine the refractive power required to get as close to 20/20 visual acuity as possible. Depending on a patient’s eyes, they may be able to achieve 20/20 acuity without visual aids, or with the use of visual aids.
What is Visual Acuity used for?
Visual acuity is used as an indicator as to whether a patient may require glasses to legally drive – without glasses a patient may only be able to achieve 20/80, but with glasses they can comfortably achieve 20/20, for example. Visual acuity is also used to help diagnose and legally define low vision, or blindness.
Over the years the eye chart has become digitized, allowing the optometrist to randomize the letters to prevent chart memorization by frequent patients. Digitizing the chart also allows the optometrist to flip through the acuity lines at the press of a button, and to easily highlight specific lines for patient’s to read. And with the use of mirror, the optometrist is able to use the chart without the exam room needing to be 20 feet in length, making the space more efficient.
One of the staple devices in the eye exam room, its design has had a few changes and modernizations as technology advanced. Also known as a refractor, the phoropter is typically mounted on an arm set up next to the exam chair that can swing and be manipulated in front of the patient’s eyes and face. The device contains many different lenses that can cycle in front of the patient’s eyes via manual or remote control. The optometrist is able to test and measure the patient’s refractive error by having the patient’s look through these lenses and evaluating how well they can see the eye chart at the other end of the room.
The phoropter contains lenses that help measure spherical power, astigmatism power and axis of rotation, and even prism power and direction. Older phoropters were controlled manually by the optometrist spinning specific dials while asking for subjective feedback from the patient as to the level of clarity of their vision with the current selection of lenses. Modern phoropters are controlled remotely with a separate control panel that can save multiple lens selections and combinations at once, allowing the optometrist to rapidly switch between lenses and hone in on the patient’s prescription. With the click of a button, the final readings can then be added to the patient’s chart and easily printed for – or even emailed to – the patient for their use.
While phoropters have been around since the 1910’s, their design and function as binocular refraction devices has changed very little, only becoming more efficient as technology has advanced.
The Slit Lamp
The second staple of an optometrist’s exam room, the slit lamp is a powerful binocular microscope that the optometrist will use to examine the physical structures of the eye and evaluate a patient’s eye health. With the patient’s head positioned on the chin rest and against the forehead rest, the optometrist is able look through the microscope and examine various points of interest from the front through to the back of the eye. The optometrist can examine the surface of the eye, the lids and the meibomian glands along the lid margins, or the tear film and evaluate its effectiveness.
By manipulating the powerful light attached to the unit, the optometrist can bounce light inside the eye to see a cross section of the layers of the cornea, examine the anterior chamber and the lens between the anterior and posterior chambers. With stronger magnification, the optometrist can look further through an appropriately sized pupil (typically dilated) to see the back of the eye, where the retina, macula and optic nerve head are.
The slit lamp will typically have several smaller devices attached to it that can swing into position as needed. This may include a smaller bright light to aid in achieving a highly detailed view inside the eye, or a tonometer to accurately measure the fluid pressure within the eye. While many devices and tools within healthcare have become digital and automatic, the slit lamp relies on the training and intricate manual control of the optometrist, and remains one of the most useful tools of diagnostics in the optometrist’s arsenal.
The Auto Refractor
One of the newer tools at an optometrist’s disposal, the auto-refractor is now a common element either in the exam rooms or during the pretest prior to the exam with the optometrist. It is a machine with a computer on board that uses light and a digital camera to give a rough measurement of the surface of a patient’s eyes. This provides the doctor with a general reading of the high points and low points of the surface of the eye (known as the keratometry or k-readings) which is useful when determining the best fit for soft contact lenses. The auto-refractor can also give a rough estimate of the patient’s starting or neutral refractive error. While it only provides a rough estimate, it provides a useful starting point for the optometrist in the exam room to work with in determining an accurate refraction and prescription for the patient.
Some auto-refractors are fitted with an additional device that uses a pin-point light to measure corneal thickness and ocular fluid pressure less invasively than older methods. The more memorable element of these auto-refractors is the “puff of air” that shoots out of the machine towards the patient’s eye. Sensors on the patient side of the machine then measure the pressure of the air that bounces back off the patient’s eye, and calculates the internal pressure of the fluids. This method of testing is considered to be preferred as it does not involve touching the patient or the eye, and can be done without administering numbing drops.
Auto-refractors can be manually controlled by a trained technician or staff member, or can be fully automatic and capable of switching between the patient’s eyes and its functions without operator input, making the pretesting stage quick and efficient.
The Retinal Camera
Another newer device that’s become a fixture for optometrists and ophthalmologists alike, the retinal camera is a powerful device with a custom camera system, microscope and onboard computer that is capable of producing high-quality images of the structures located within the back of the eye. Known as fundus photography, the image captured can show the retina, macula, optic nerve, and all the veins and vessels all at once and in impeccable detail.
While the slit lamp allows the optometrist to look at the same structures themselves, the photo is useful in seeing the whole of the rear of the eye as one image, and to see the normally small parts of the eye at a much larger scale and level of detail only available with digital photography. Fundus photography can help detect retina or vitreous tears, damage caused by diabetic eye disease, swelling of the optic nerve and the early warning signs of glaucoma.
Some cameras have also been modified with an additional scanning function, and using light waves are able to produce a cross section scan of the retinal layers and the macula. Known as the Optical Coherence Tomography, or OCT scan, the scans can help the optometrist detect changes in retinal layer thickness, detect separations or irregularities, and aid in diagnosing conditions such as macular degeneration or diabetic eye disease. OCT scans can help provide guidance for treatment plans for conditions like glaucoma.
The photos and scans produced by these retinal cameras have been invaluable in early detection of eye related diseases and conditions, and more and more optometrists are implementing them as a standard part of a regular exam.
The Visual Fields Test
Though not as common as some of the other devices and instruments in this article, the visual fields test is just as important for the purposes of diagnosing severe conditions. The visual fields test measures the total width of a patient’s area of vision while they focus on a single point straight ahead, also known as the measure of peripheral vision ability in degrees. This test can detect any blind spots a patient might have, or a decrease in peripheral ability over time due to conditions such as glaucoma.
The ways the visual fields test is administered can vary depending on whether the optometrist or ophthalmologist wants to run a basic check or a more in-depth examination. The detailed visual field test involves the patient looking into a machine called a perimeter and staring at a predetermined fixed point on the screen inside. The patient is then instructed to press a button every time they see a blinking light or moving line appear somewhere else on the screen without looking away from the centre. The test is done per eye, with the untested eye covered for the duration, and can take anywhere from three to ten minutes to complete depending on the testing type.
In some cases, a patient may only need to have visual field screening once. Other patients may need regular screening on a yearly or bi-annual basis. Certain jobs and careers require a visual field test as a part of their application process, and at least a basic visual field screening is required for new drivers getting their license in Ontario. Should you find yourself requiring a visual field test for any reason, a quick call to your regular optometrist to see if they provide that testing is recommended.
The Importance of Eye Exams
As you can see, the eye exam has come a long way from the early days as technology has advanced, allowing doctors to assess and evaluate ocular conditions earlier than they had in the past. And with early detection comes early treatment and management. A thorough modern eye exam is just as important for your overall health as your yearly physical with your family doctor. It is important to note that not every eye exam offered will have all of these instruments and checks, so it is important to inquire ahead of time as to what the eye exam consists of and whether that is right for you and your needs.
At 360 Eyecare, we believe in offering our patients the full scope of eye health needs, and our comprehensive eye exams reflect that vision. Please reach out to any of our three locations to book your next eye exam today: 360 Eyecare – Rosedale, 360 Eyecare – Beaches and 360 Eyecare – Metro.