Vision-Related Terms

We would like to help you learn about some vision-related terms. 

Acuity = keenness of perception; sharpness of vision 

Amblyopia = diminished sight in one eye (also called Lazy Eye) 

Cataract = the clouding of the lens of the eye, which is normally clear; light can no longer pass through the lens easily and vision becomes hazy or blurred; current treatment is the surgical removal of the lens and replacement with a man-made lens, which is safe and successful 

Cortical Visual Impairment (CVI) = a condition that indicates that the visual systems of the brain do not consistently understand or interpret what the eyes see 

Diabetic retinopathy = an eye disorder that is caused by diabetes that usually appears in stages and can lead to blindness; a complication of diabetes caused by damage to blood vessels in the retina 

Farsightedness = able to see distant objects more clearly than nearby objects 

Functional blindness = no useful vision 

Glaucoma = the second leading cause of blindness in the United States; a disease where pressure within the eye is so high that it can damage the optic nerve and lead to vision loss; it affects side vision long before central vision is affected 

Legal blindness = a central vision acuity for distance of 20/200 or poorer in the better eye with correction; or a field of vision no greater than 20 degrees in widest diameter 

Low vision = vision that cannot be further improved by corrective lenses or medical or surgical intervention, although low vision rehabilitation may help someone to use his/her remaining sight more effectively 

Macula = the specialized part of the retina responsible for sharp central vision (the ability to see detail) 

Macular degeneration = the leading cause of blindness for people over the age of 50; and eye disease that results from damage to the macula 

Nearsightedness = able to see nearby objects more clearly than distant objects 

Optic Nerve Atrophy = the degeneration of the part of the eye that carries stimuli from the rods (the part of the retina that allows one to see in low light) and cones (the part of the retina that allows one to see color) to the brain 

Optic Nerve Hypoplasia = underdevelopment of the optic nerve during pregnancy 

Retina = the sensory membrane that lines the eye, receives the image formed by the lens, is the immediate instrument of vision, and is connected with the brain by the optic nerve 

Retinitis pigmentosa (RP) = condition characterized by the progressive loss of peripheral vision, usually beginning with night blindness 

Retinopathy of Prematurity (ROP) = an eye disorder affecting premature infants; ROP affects immature blood vessels of the retina 

Severe vision impairment = inability to read ordinary newsprint with the best correction (glasses or contact lenses) 

Strabismus = eye misalignment or eyes that do not move normally, caused by an imbalance of the muscles that move the eyeball 

Visual impairment = trouble seeing with one or both eyes when wearing glasses or contact lenses 


Understanding Eye Specialists and Their Training


Performs surgery. Diagnoses and treats eye diseases. Tests for visual acuity and visual field. Prescribes glasses, low vision aids (magnifiers) and medication.


4 years college
4 years medical school
1 year internship
3 years residency

12 years total

(1 additional year for pediatric specialty)



Prescribes glasses, low vision aids (magnifiers), and teaches patients how to use them. Some may do low vision exams and provide vision training activities. Some states allow diagnosis and prescription.


4 years college
3-4 years optometry school

7-8 years total



Grinds and fits lenses prescribed by ophthalmologist or optometrist.


1 year of optical courses
2 years apprenticeship under certified optician

3 years total