eccentric fixation is when a person looks at a target using a spot on the retina that is not the fovea (the normal center of sharpest vision). It can happen as an adaptation to central vision loss or as part of certain childhood vision disorders. Clinicians discuss eccentric fixation in amblyopia and strabismus evaluations and in low-vision rehabilitation. It is described and measured during eye exams rather than being a single “treatment” on its own.

fixation is the ability to hold your gaze steadily on a specific target. In eye care, it describes how accurately the eyes place an image on the fovea (the sharpest point of vision). Clinicians use fixation in vision testing, eye movement assessment, and retinal imaging. In surgical contexts, fixation can also mean securing an implant or tissue in a stable position.

suppression is a visual processing response where the brain reduces or “tunes out” input from one eye. It most often occurs when the eyes are misaligned (strabismus) or send unequal image quality (anisometropia). In everyday terms, it is the brain’s way of avoiding double vision or visual confusion. The concept is commonly used in binocular vision assessment in ophthalmology and optometry.

fusion is the brain’s ability to combine the two eyes’ images into one single visual percept. It is a core part of binocular vision, along with eye alignment and depth perception. In eye care, fusion is evaluated in exams for strabismus (eye misalignment), double vision, and eyestrain. It can also be supported through optical corrections, prisms, or structured visual training, depending on the case.

depth perception is the visual ability to judge how far away objects are and how they relate to each other in 3D space. It helps you reach for a cup, step off a curb, and navigate crowds without bumping into things. Clinically, it is assessed as part of binocular vision (how the two eyes work together). It is commonly discussed in eye exams, pediatric vision care, sports vision, and after eye disease or injury.

central vision is the part of vision used to see fine detail straight ahead. It supports tasks like reading, recognizing faces, and driving. It comes mainly from the macula, the center of the retina at the back of the eye. The term is used in eye exams, imaging, and discussions of macular disease and vision rehabilitation.

peripheral vision is the part of sight that detects what is happening outside the center of your gaze. It supports awareness of movement and objects to the sides, above, and below where you are looking. People rely on it for everyday tasks like walking through crowds, driving, and sports. Clinicians assess it to understand eye health and to screen for conditions that affect the visual field.

A visual field is the full area you can see while looking straight ahead. It includes central vision and peripheral (side) vision in each eye. Clinicians use visual field assessment to understand how vision is functioning beyond a standard eye chart. It is commonly used in eye care, neurology, and driving- or work-related vision evaluations.

color vision is the ability to detect and interpret differences in light wavelength as different colors. It is a normal visual function mainly supported by cone cells in the retina. It helps people recognize objects, signals, and subtle visual patterns in daily life. It is also used in eye care to support diagnosis and monitoring of certain eye and nerve conditions.

contrast sensitivity is the ability to see differences between an object and its background when the contrast is low. It complements visual acuity, which measures how small a high-contrast letter you can read. It helps explain real-world vision problems like trouble seeing in fog, dim light, or glare. It is commonly assessed in eye clinics and research to evaluate visual function beyond the eye chart.

stereopsis is the brain’s ability to perceive depth by combining the two slightly different images from each eye. It is often described as “3D vision” or true binocular depth perception. Clinicians assess it to understand how well the eyes work together. It is commonly discussed in eye exams, strabismus care, and vision development in children.

binocular vision is the ability to use both eyes together as a coordinated system. It allows the brain to combine two slightly different images into one clear visual percept. It is commonly discussed in eye exams, strabismus (eye misalignment) care, and vision therapy. It also matters in everyday tasks like reading, driving, sports, and hand–eye coordination.

convergence is the coordinated inward movement of both eyes to look at a near object. It is a normal part of binocular vision, helping the brain combine two images into one. Clinicians assess convergence during eye exams when people report near-vision symptoms. convergence is also a key concept in strabismus care, prism prescribing, and vision therapy.

amplitude of accommodation is the eye’s focusing range from far to near. It describes how much the natural lens can change focus to keep near objects clear. Clinicians use it in eye exams to understand near-vision function and age-related changes. It is commonly discussed in presbyopia, eyestrain, and pediatric vision assessments.

accommodation is the eye’s natural ability to change focus from far to near. It happens mainly by changing the shape of the eye’s crystalline lens. It is commonly discussed in eye exams, reading vision, and presbyopia (age-related near blur). Clinicians also consider accommodation when evaluating eye strain, headaches, and binocular vision issues.

interpupillary distance is the distance between the centers of your pupils. It helps align lenses and optical devices with the way your eyes naturally look at the world. It is commonly used when making eyeglasses, fitting some contact lens setups, and adjusting binocular devices. Clinicians also document it as part of broader binocular vision and facial/ocular assessments.

pupillary distance (PD) is the distance between the centers of the two pupils. It is most commonly used to center eyeglass lenses so the optical zones align with the eyes. It can be measured for distance viewing and for near tasks like reading. It is a practical measurement used in optometry, ophthalmology, and optical dispensing.

A prism diopter is a unit used to describe how strongly a prism bends (deviates) light. It is commonly written as Δ and used in eye care to measure and prescribe prism. Prism is used in exams and in eyeglasses to help align images seen by the two eyes. You’ll encounter prism diopter in optometry and ophthalmology when discussing strabismus and double vision.

A diopter is a unit used to describe the focusing power of a lens or optical system. It is most commonly used in eyeglass prescriptions, contact lens prescriptions, and intraocular lens (IOL) calculations. It helps clinicians quantify how much a lens converges or diverges light to bring images into focus on the retina. You will usually see it written as “D” in clinic notes and prescriptions.

keratometry is a way to measure the curvature of the cornea, the clear front window of the eye. It produces “K readings,” which describe how steep or flat the central cornea is. Eye care clinicians use keratometry in routine eye exams and before many types of eye surgery. It is also a core measurement for fitting contact lenses and assessing astigmatism.