If you regularly visit an eye clinic for an eye exam, you may notice the optometrist jot down a few points, such as “visual acuity,” during the test or as they ask you questions. While you might be familiar with “20/20 vision,” you may also notice they record “20/60 uncorrected.” This unfamiliar fraction can leave you confused. It doesn’t end here. After trying out a few lenses, your optometrist explains that you now have a “myopic” prescription, but what exactly does that mean? We could go on and on.
Eye exams often come with terminology that can feel unfamiliar or technical. We aim to break down some of the most common eye exam terms and explain what they mean in this blog so you’ll know exactly what’s happening during your next visit to a Toronto optometrist.
What are Myopia, Hyperopia, and Emmetropia?
These terms refer to different types of refractive errors or vision prescriptions that affect how the eyes focus.
Myopia, commonly known as near-sightedness, means that a person can see objects up close more clearly than those far away, without the need for glasses or contact lenses in Toronto. If you have myopia, your prescription will show a minus sign (-) in the Sphere (SPH) column, indicating that your eyes have “too much focusing power” for distant objects to appear clear.
Hyperopia, on the other hand, means the person can see distant objects more easily but has to work harder to focus on close objects. If you are hyperopic, your prescription will have a plus sign (+) in the SPH column. Hyperopic eyes are considered “underpowered,” making it challenging to focus on nearby objects, though distance vision may also be slightly blurry.
Emmetropia refers to the absence of any refractive error. Meaning no prescription is needed. It is often described as having “normal” vision and serves as a reference point for measuring visual acuity and clarity.
What is Presbyopia?
Another term that describes a refractive error type is presbyopia, which refers to the degeneration of the eye’s ability to see things up close as we age, regardless of the patient’s prior prescription.
The muscle or lens inside the eye, separate from the cornea, is normally very elastic when we are younger and will adjust in size when we are trying to focus on objects up close.
As we age, this lens loses its elasticity, making it harder to focus properly up close. Symptoms of this physical change start to show up around the age of forty and, for most patients, become significant enough to require specific reading correction around forty-five. You can be myopic, hyperopic, or emmetropic and still develop presbyopia.
When planning for an eye exam to check for presbyopia or other vision changes, knowing what to expect and the available coverage in Toronto can make the process easier.
What is Astigmatism?
Astigmatism is caused by the shape of the eye and affects focusing ability at all distances. Instead of being perfectly round, an astigmatic eye is more cylindrical, causing light to bend unevenly. As a result, the eye cannot focus light onto the retina at a single point, making objects appear blurry or distorted, no matter how hard the eye tries to focus.
No eye is perfectly round, and mild astigmatism often goes unnoticed as the brain compensates for it. However, higher levels of astigmatism can cause significant blurring and difficulty in distinguishing shapes.
Astigmatism is corrected with specially shaped eyeglasses or contact lenses designed to match the eye’s cylindrical curvature, helping light focus uniformly. In some cases, surgery can also correct astigmatism.
If your prescription includes astigmatism, it will appear in the Cylinder (CYL) and Axis sections, indicating the degree and orientation of the irregular curvature.
What is Visual Acuity?
Commonly mistaken as a prescription value, visual acuity is a graded measurement of an eye’s ability to see and distinguish shapes and the details of an object at a specific distance. It typically appears as a fraction, either resembling “20/20” or “6/6”, with the upper number representing the distance from which the patient can see the specific object, while the bottom number represents the distance an “emmetropic” eye can see the same object.
For example, if a patient only clearly sees the letters on the chart at 20 feet when the normal eye can see them at 30 feet, the optometrist would then note the visual acuity of that eye as “20/30”.
Visual acuity is measured a few times during a regular exam and will sometimes have additional notes such as “uncorrected” or “best corrected” next to them. Optometrists in Toronto will measure a patient’s visual acuity with no glasses, contact lenses, or other visual aids first to get a baseline (“uncorrected”), and then with the use of the phoropter or other lenses, attempt to bring the patient’s acuity as close to “20/20” as possible (“best corrected”).
Just because you wear glasses doesn’t mean you aren’t able to achieve 20/20 vision. It just means you require glasses or contact lenses to do so.
What is the Cornea?
Another term that comes up often during an eye exam is the cornea. This is a transparent physical part of the eye that covers the front-most part of it. It completely covers the iris and pupil. It is responsible for the eye’s visual ability and prescription and helps to protect much of the inner parts of the eye.
The cornea also plays a huge role in successful contact lens wear and the ability to wear certain brands, sizes, and shapes. Every cornea is unique, as most are not perfectly smooth like the surface of a ball but have high points and low points along certain meridians. The shape of the cornea affects the eye’s prescription.
Hence, most laser or corrective surgery involves reshaping the cornea in specific ways to alter a patient’s prescription, though there are limits to this. The cornea is made up of five separate layers. From the uppermost layer down, they are the “epithelium,” “Bowman’s membrane,” the “stroma,” “Decemet’s membrane,” and the “endothelium.”
What is the Eye Lens?
The lens within the eye, also known as the crystalline lens, is the structure within the eye that helps to focus rays of light to land on the retina, thus allowing us to see. The lens is a very elastic structure of clear tissues that are controlled by muscles holding it in place behind the pupil and in front of the retina.
When the brain sends the appropriate signals, the muscles pull and shape the lens, which increases or decreases the focusing power to let light pass through the eye and hit the retina properly. If light cannot hit the retina properly, it may be due to the shape of the eye itself or the shape of the cornea affecting its path, thus the need for a prescription.
As we age, the elasticity of the lens starts to weaken, the muscles become stiffer, and the clear tissues that make up the lens start to become cloudy. The lens spends more and more of its time in the “default” shape, which does not help with focusing on objects up close.
Using reading or progressive glasses will help with the changes in visual clarity, but eventually, the clouding of the lens will increase until a cataract is formed, which is the hardened form of the crystalline lens. At this point, it must be surgically removed to allow light to pass through the eye freely again, and artificial implants are put in to help focus the light on the retina.
What is Dilation, and What are Dilation Drops?
To “dilate” means to widen an opening. In optical terms, dilation refers to the actions of the pupil opening to allow more light through the eye. If you think of the eye as a camera system, then the pupil is the aperture that controls the amount of light entering through the system and hitting the film, or the retina, at the back.
The size of the pupil is controlled via signals sent by the brain in response to light levels in your surroundings; high light levels mean the pupil will be smaller, so as not to allow too much light through the eye, and low light levels require a larger pupil to allow as much light as possible through.
During an eye exam in Toronto, optometrists need to see clearly through to the back of the eye to examine the full scope of the retina and the condition of the macula, two structures that play a huge role in the ability to see.
Whether the optometrist chooses to use retinal imaging or the slit lamp biomicroscope, the pupil needs to be of adequate size to get a good view of the inside. As the instinct is to close the pupil under harsh or bright lighting, the optometrist may request the patient’s consent to use dilation drops.
These drops temporarily widen the opening of the pupil and paralyze the pupil’s ability to change size, preventing it from shrinking during the remainder of the exam.
What is a Floater?
To understand what a floater is, first, you must understand that the globe or ball of an eye is not solid. It is comprised of two “chambers” filled with fluid: a chamber behind the cornea and in front of the crystalline lens, and the other chamber behind the lens and in front of the retina. It is in this second chamber that floaters tend to originate.
A floater is a particle that forms within the fluid – called vitreous fluid – that is large enough to cast a shadow on the retina when it floats between it and the light entering the eye. These shadows can all look very different depending on the shape of the floater, from small lines to spots, from cobwebs to cotton wisps.
Floaters on their own cause no harm aside from being mildly annoying as they move about, but a sudden increase in their number, or abrupt change in their appearance, or any other visual disturbance or distortion occurring in that eye can indicate more serious ocular conditions and should be brought to the attention of an optometrist as soon as possible.
Conclusion
With these explained terms, you’ll have a better understanding of the jargon used during your next eye exam in Toronto. While there are many more terms, this overview gives you a starting point. If these terms are unfamiliar, it may be time to visit an eye clinic for a comprehensive exam.
For anyone searching for an Eye Clinic Near Me in Toronto, our clinics in Yorkville at 55 Bloor St W, Suite 03, and in The Beaches at 2199 Queen St E offer a welcoming environment with experienced optometrists ready to guide you through your eye care journey. Better yet, book an appointment today. We’ll be happy to assist you!
Frequently Asked Questions
1. Why is it important to understand eye exam terminology?
Understanding common eye exam terms helps you communicate better with your optometrist and ensures you are actively involved in decisions about your eye health.
2. What is an eye refraction test?
An eye refraction test determines your prescription for glasses or contact lenses by measuring how light bends (or refracts) as it passes through your eye.
3. What is binocular vision?
Binocular vision refers to the way both eyes work together to create a single, three-dimensional image. Problems with binocular vision can lead to double vision or eye strain.
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