A – C
The eye's ability to change focus between near and far objects by flexing the crystalline lens. This ability naturally decreases with age — a condition known as presbyopia — making reading glasses necessary for many adults over 40.
A measurement of how clearly you see, typically expressed as a fraction (such as 20/20). "20/20" means you can see at 20 feet what a person with normal vision sees at 20 feet. 20/40 means your visual acuity is reduced, and 20/200 or worse is considered legally blind in most states.
A condition in which one eye does not develop normal vision during childhood, usually because the brain begins to favor the other eye. Amblyopia is best treated early in childhood through patching, atropine drops, or glasses. Without treatment, the vision deficit can become permanent.
An irregularity in the shape of the cornea or lens that causes blurry or distorted vision at all distances. Rather than being perfectly round like a basketball, the eye is more oval like a football. Astigmatism is very common and is corrected with glasses, toric contact lenses, or refractive surgery.
A number from 1 to 180 found on your glasses prescription when you have astigmatism. It indicates the orientation (angle) of the astigmatism correction. The axis tells lens makers which direction to position the cylindrical correction in your lens.
Inflammation of the conjunctiva — the clear tissue lining the inner eyelid and covering the white of the eye. Causes include bacterial infection, viral infection, and allergies. Bacterial and viral forms can be contagious; allergic conjunctivitis is not. Treatment depends on the cause.
The clear, dome-shaped front surface of the eye that plays a major role in focusing light onto the retina. The cornea is responsible for roughly two-thirds of the eye's total focusing power. Conditions affecting the cornea include keratoconus, corneal abrasions, and dry eye disease.
The "CYL" value on your prescription measures the amount of astigmatism correction needed. It can be a positive or negative number. If your prescription has no CYL value, it means you do not have significant astigmatism in that eye.
D – F
A complication of diabetes that damages the blood vessels in the retina. In early stages, it often causes no symptoms. As it progresses, it can cause swelling, leaking, abnormal vessel growth, and eventually significant vision loss. Annual dilated eye exams are the most important preventive step for patients with diabetes.
The process of enlarging the pupil using eye drops so the doctor can examine the structures at the back of the eye, including the retina, optic nerve, and blood vessels. Dilation causes temporary light sensitivity and blurred near vision, typically lasting 2–4 hours. Many patients can now choose Optomap retinal imaging as an alternative or complement to dilation.
Small yellow or white deposits that form under the retina. Small, hard drusen are common with age and are generally low-risk. Larger, softer drusen are associated with age-related macular degeneration (AMD) and require closer monitoring. Drusen are detected through retinal imaging during a comprehensive eye exam.
Small shapes — specks, threads, or cobwebs — that drift across your field of vision. They are caused by tiny clumps or fibers in the vitreous gel inside the eye casting shadows on the retina. Most floaters are harmless and age-related. A sudden onset of many new floaters, especially with flashes of light, should be evaluated promptly to rule out retinal detachment.
The interior surface of the back of the eye, including the retina, optic disc, macula, and blood vessels. When your doctor takes a "fundus photo" or performs a "fundus exam," they are examining these structures to evaluate your eye health and screen for disease.
G – L
A group of eye diseases that damage the optic nerve, typically caused by elevated intraocular pressure (IOP). Glaucoma often has no early symptoms — peripheral vision is lost first, and by the time patients notice changes, significant damage may have already occurred. It is the leading cause of irreversible blindness worldwide. Early detection through regular exams is critical.
The fluid pressure inside the eye, measured in millimeters of mercury (mmHg). Normal IOP typically ranges from 10–21 mmHg. Elevated IOP is a major risk factor for glaucoma, though glaucoma can occur at normal pressures and elevated pressure does not always lead to glaucoma. IOP is measured during routine eye exams using a device called a tonometer.
A progressive condition in which the cornea gradually thins and bulges outward into a cone shape, distorting vision in ways that glasses cannot fully correct. It typically appears in adolescence or early adulthood. Management includes specialty contact lenses (scleral or RGP lenses) and, in some cases, corneal cross-linking to halt progression.
The transparent, flexible structure behind the iris that helps focus light onto the retina. The crystalline lens changes shape to allow near and far focus (accommodation). With age, it becomes less flexible (presbyopia) and can become cloudy (cataract). It is different from the corrective "lenses" in glasses or contact lenses.
M – R
A small but critical area at the center of the retina responsible for sharp, detailed central vision. The macula is used for reading, recognizing faces, and seeing fine detail. Conditions like age-related macular degeneration (AMD) and diabetic macular edema affect this area and can cause central vision loss.
A common cause of dry eye in which the small oil-secreting glands along the eyelid margins become blocked or produce poor-quality oil. This disrupts the tear film's oily outer layer, causing tears to evaporate too quickly. Symptoms include dry, irritated, or watery eyes. Treatment includes warm compresses, lid hygiene, and in some cases, in-office procedures.
A refractive error in which distant objects appear blurry while close objects remain clear. It occurs because the eye is too long or the cornea too curved, causing light to focus in front of the retina rather than on it. Myopia is corrected with minus-power lenses. High myopia (above -6.00 D) significantly increases the risk of retinal detachment, glaucoma, and other complications.
A non-invasive imaging test that uses light waves to take cross-sectional images of the retina, showing individual tissue layers with microscopic detail. It is used to detect and monitor conditions including glaucoma (optic nerve fiber layer), macular degeneration, and diabetic eye disease. The scan is painless and takes only seconds.
The nerve that transmits visual information from the retina to the brain. It contains approximately one million nerve fibers and is visible during a dilated eye exam as the optic disc at the back of the eye. Damage to the optic nerve — as seen in glaucoma — results in permanent vision loss because nerve fibers do not regenerate.
The natural, age-related loss of the eye's ability to focus on close objects, typically becoming noticeable in the early to mid-40s. It occurs because the crystalline lens gradually loses flexibility. Presbyopia is corrected with reading glasses, bifocals, progressive lenses, multifocal contact lenses, or refractive surgery.
The light-sensitive tissue lining the back of the eye, similar to film in a camera. The retina contains millions of photoreceptor cells (rods and cones) that convert light into electrical signals sent via the optic nerve to the brain. Retinal conditions — including detachment, macular degeneration, and diabetic retinopathy — can cause severe or permanent vision loss.
S – Z
A large-diameter rigid gas-permeable contact lens that vaults completely over the cornea and rests on the white of the eye (the sclera). Scleral lenses create a fluid-filled reservoir over the eye, providing exceptional vision correction for irregular corneas (such as keratoconus) and severe dry eye. They are more comfortable than standard RGP lenses and are an increasingly popular specialty lens option.
The main power value on your glasses prescription, measured in diopters (D). A minus (-) value indicates myopia (nearsightedness); a plus (+) value indicates hyperopia (farsightedness). The higher the number, the stronger the prescription. A sphere value of 0.00, DS, or Plano means no spherical correction is needed in that eye.
A misalignment of the eyes in which one or both eyes turn inward, outward, upward, or downward — either constantly or intermittently. It can lead to amblyopia (lazy eye) if untreated. Treatment options include glasses, patching, vision therapy, and in some cases surgery. Strabismus affects both children and adults.
The measurement of intraocular pressure (IOP) inside the eye, used primarily to screen for and monitor glaucoma. The traditional "air puff" test is one method, but many practices — including Santé Eyecare — use a non-contact tonometer that is more comfortable while still providing accurate readings.
The entire area you can see — including peripheral (side) vision — without moving your eyes. Visual field testing is a key diagnostic tool for detecting and monitoring glaucoma, neurological conditions, and other diseases that affect peripheral vision. You typically press a button each time you see a flicker of light while looking straight ahead during the test.