photophobia means increased sensitivity or intolerance to light. It is a symptom, not a diagnosis, and it can come from eye conditions or non-eye conditions. People may describe it as discomfort, pain, squinting, or the urge to avoid bright places. The term is commonly used in ophthalmology, optometry, neurology, and primary care.

photopsia is the perception of flashes of light when no external light stimulus is present. People often describe it as brief sparks, lightning streaks, flickers, or shimmering. It is a symptom term used in ophthalmology, optometry, neurology, and emergency eye care. Clinicians use it to help localize whether a visual complaint may be coming from the retina, vitreous, optic pathways, or brain.

flashes are brief perceptions of light when no external light source is present. People often describe them as lightning streaks, sparks, arcs, or camera-like flickers. In eye care, flashes are treated as a symptom that can reflect changes in the vitreous, retina, or visual pathways. They are commonly discussed alongside floaters and sudden changes in peripheral vision.

floaters are small shapes that appear to drift across vision, often described as specks, threads, or cobwebs. They are a visual symptom caused by tiny shadows cast inside the eye. floaters are most commonly discussed in routine eye care and urgent retina evaluations. They can be harmless, but they can also be a clue to conditions affecting the vitreous or retina.

A scotoma is an area of reduced or missing vision within an otherwise normal field of view. It can look like a blank spot, a blurry patch, a dark area, or a shimmering “gap” in vision. The term is used in eye care and neurology to describe *where* vision is affected and *how* it behaves. Clinicians use scotoma patterns to help localize problems in the retina, optic nerve, or brain pathways for vision.

metamorphopsia is a visual symptom where straight lines look wavy, bent, or distorted. It is most commonly linked to problems affecting the macula, the central part of the retina used for detailed vision. Clinicians use the term to describe a patient’s experience and to guide testing for retinal disease. It is discussed in eye clinics, optometry practices, and ophthalmology training because it can signal clinically important change.

distortion is a change in how a visual image appears compared with reality. It can make straight lines look wavy, objects look stretched, or shapes look uneven. In eye care, distortion is most commonly discussed as a symptom of retinal or corneal problems. It is also used to describe optical side effects from glasses, contact lenses, or imaging systems.

peripheral vision loss means reduced ability to see objects off to the sides while looking straight ahead. People often describe it as “tunnel vision,” bumping into things, or missing movement coming from the side. In eye care, it is a symptom and a clinical finding rather than a single disease. It is commonly discussed in glaucoma care, retinal disease, neuro-ophthalmology, and driving/visual function questions.

central vision loss means reduced or missing vision in the center of what you see. It often affects reading, recognizing faces, and seeing fine detail. Clinicians use the term to describe a symptom pattern and to guide eye testing. It is commonly discussed in macular (retina) disease and optic nerve conditions.

gradual vision loss means a slow decline in visual clarity, field of view, or visual function over weeks, months, or years. It is a symptom description, not a single diagnosis. It is commonly used in eye clinics, primary care, and emergency triage to distinguish slower changes from sudden vision loss. It helps guide what conditions are considered and what tests are prioritized.

sudden vision loss means a noticeable drop in vision that occurs over seconds, minutes, or hours. It is a symptom, not a diagnosis, and it can involve one eye or both eyes. The term is commonly used in emergency care, optometry, and ophthalmology triage. It signals a need to quickly determine where in the visual system the problem is occurring.

vision loss means a reduction in the ability to see, compared with a person’s previous level of vision. It can affect sharpness, contrast, color, or the visual field (side vision). It is a symptom, a clinical finding, and sometimes a functional disability, depending on severity and cause. The term is commonly used in eye clinics, emergency care, and low-vision services to describe vision-related change.

blurred vision means that vision is not sharp, and fine details look smeared, hazy, or out of focus. It is a symptom rather than a single disease. People use the term in everyday life, and clinicians use it in eye exams and medical histories. It can be temporary or persistent, and it can involve one eye or both.

polycarbonate lenses are eyeglass lenses made from a durable plastic polymer called polycarbonate. They are designed to correct vision like other spectacle lenses, while emphasizing impact resistance and lighter weight. They are commonly used in children’s glasses, safety eyewear, sports eyewear, and some rimless or semi-rimless frames. In clinical practice, they are one of several lens material options selected based on prescription needs and lifestyle risks.

anti-reflective coating is a thin, transparent layer applied to optical surfaces to reduce glare and reflections. It is most commonly used on eyeglass lenses, but it is also used on instrument optics in eye clinics. By reducing surface reflections, it can improve visual clarity and cosmetic appearance. Its performance and durability vary by material and manufacturer.

photochromic lenses are eyeglass (and some contact or implant) lenses that darken in response to ultraviolet (UV) light and lighten again indoors. They are commonly used in everyday prescription glasses and non-prescription eyewear to reduce brightness outdoors. They aim to provide convenient, automatic light adaptation without switching between clear glasses and sunglasses. Performance and features vary by material and manufacturer.

prism glasses are eyeglasses that include prism power in one or both lenses. They shift where images fall so the eyes can aim more comfortably together. They are commonly used for double vision and certain binocular vision problems. They are prescribed by optometrists and ophthalmologists after eye alignment testing.

progressive addition lenses (PAL) are eyeglass lenses that change power gradually from top to bottom. They are commonly used to help people see clearly at distance, intermediate (computer range), and near. They are most often prescribed for presbyopia, the age-related loss of near focusing ability. They are worn in everyday glasses for work, reading, and driving.

trifocals are vision-correcting lenses designed with three distinct focal zones. They are commonly used in eyeglasses to help people see far away, at intermediate distance, and up close. They are most often prescribed for presbyopia, the age-related reduction in near focusing ability. In some settings, “trifocal” can also describe certain intraocular lenses used during cataract surgery.

bifocals are eyeglass lenses with two different optical powers in a single lens. They are commonly used to correct distance vision and near vision at the same time. They are most often prescribed for age-related near focusing difficulty (presbyopia). They are used in everyday settings like reading, computer tasks, and driving.