Optometry is a healthcare profession concerned primarily with examining vision and the eyes, identifying refractive errors and ocular abnormalities, providing optical correction and managing or referring eye conditions within the practitioner's scope of practice and jurisdiction. Optometrists commonly perform eye examinations, assess visual function, prescribe spectacles or contact lenses and detect signs of ocular or systemic disease. Modern optometry extends beyond simply determining whether someone needs glasses because examination of the eyes can reveal abnormalities involving the cornea, lens, retina, optic nerve, intraocular pressure and visual pathways. Scope of practice varies internationally, including differences in diagnostic authority, prescribing rights and surgical involvement.
Refraction is a central optometric function and determines the optical correction required to focus images appropriately on the retina. Myopia occurs when distant objects are focused in front of the retina under relaxed accommodation, hyperopia when the optical system tends to focus behind the retina, and astigmatism when optical power varies with meridian. Presbyopia is the age-related reduction in accommodative ability that makes near focusing more difficult.
Spectacles, contact lenses and other optical devices can compensate for refractive errors, but correction of refraction is distinct from treatment of the underlying biological causes of many eye diseases. Visual acuity is also only one component of vision and does not by itself provide a complete assessment of ocular health.
A comprehensive eye examination can evaluate structures and functions throughout the eye. Depending on the clinical setting, assessment may include visual acuity, refraction, pupil responses, ocular motility, visual fields, anterior eye examination, intraocular pressure and examination of the retina and optic nerve. Retinal imaging, optical coherence tomography and other technologies can provide detailed structural information. These tests can assist with detection and monitoring of diseases such as glaucoma, diabetic retinopathy, macular degeneration and retinal disorders. However, a screening test and a definitive diagnosis are not necessarily the same thing; abnormal findings may require additional investigations or referral to an ophthalmologist or another medical specialist.
Glaucoma illustrates why optometry is not simply an optical service. Glaucoma encompasses a group of optic neuropathies involving characteristic damage to the optic nerve and corresponding visual-field loss, with elevated intraocular pressure being an important risk factor but not a universal defining feature. Optometrists can identify risk factors and suspicious structural or functional findings through eye examination and monitoring, while treatment and prescribing responsibilities depend on jurisdiction and practitioner scope. Early disease may produce few noticeable symptoms, so examination can identify problems before a person recognises functional impairment. The distinction between measuring intraocular pressure and diagnosing glaucoma is important because pressure is one clinical variable rather than a standalone diagnosis.
Optometry also has an important role in detecting systemic disease through ocular findings. Diabetes can cause retinal vascular changes and diabetic retinopathy, hypertension can produce retinal vascular abnormalities, and some neurological or inflammatory diseases can manifest through the optic nerve or other ocular structures. Eye examination may therefore contribute to broader medical assessment, although an ocular finding alone does not necessarily establish a systemic diagnosis. Optometrists may communicate findings to general practitioners, ophthalmologists or other specialists when further investigation is indicated. The eyes can provide a clinically accessible view of vascular and neural tissues, which contributes to the diagnostic value of ocular examination.
Contact lens practice involves assessment of the ocular surface, tear film, corneal health, lens fit and the individual's ability to handle and care for lenses safely. Contact lenses alter the environment immediately surrounding the cornea, so poor hygiene, inappropriate wear schedules or unsuitable fitting can increase the risk of complications, including corneal infection. Different lens materials and designs serve different optical and clinical purposes, including correction of myopia, astigmatism and presbyopia. Contact lenses should therefore be treated as medical devices requiring appropriate fitting, instruction and ongoing assessment rather than simply as cosmetic alternatives to spectacles.
Paediatric optometry addresses vision during a period when visual development is particularly important. Conditions such as significant uncorrected refractive error, amblyopia and binocular vision disorders can interfere with visual development and educational performance. Amblyopia is reduced visual function resulting from abnormal visual development rather than simply an optical blur that can always be corrected immediately with spectacles. Assessment of children may therefore involve age-appropriate tests of acuity, alignment, ocular health, binocular function and refractive status. Myopia management has also become an important area of contemporary optometry, involving strategies intended to reduce the rate of myopic progression in appropriately selected children.
Optometry sits within a wider eye-care system that includes ophthalmology, orthoptics, dispensing optics and other healthcare services. Ophthalmologists are medical doctors specialising in eye disease and can perform surgery, while optometrists generally provide primary eye care, examination, optical correction and detection or management of eye conditions within their legal scope. Orthoptists have particular expertise in binocular vision, ocular motility and related disorders, particularly within hospital eye services. The boundaries differ between countries, so descriptions based on one healthcare system cannot automatically be applied globally. The central function of optometry is the preservation and optimisation of vision through examination, correction, detection, management and appropriate referral.
