Eye Examination Tests
Eye Examination Tests
An eye examination is a series of tests performed by an ophthalmologist (medical doctor), optometrist, or orthoptist, optician, assessing vision and ability to focus on and discern objects, as well as other tests and examinations pertaining to the eyes. Health care professionals often recommend that all people should have periodic and thorough eye examinations as part of routine primary care, especially since many eye diseases are asymptomatic.
Visual acuity - Visual acuity is the eye's ability to detect fine details and is the quantitative measure of the eye's ability to see an in-focus image at a certain distance. The standard definition of normal visual acuity (20/20 or 6/6 vision) is the ability to resolve a spatial pattern separated by a visual angle of one minute of arc.
Refraction - In physics, "refraction" is the mechanism that bends the path of light through the eye. In an eye exam, the term refraction is the determination of the ideal correction of refractive error.
Objective refraction - An objective refraction is a refraction obtained without receiving any feedback from the patient, using a retinoscope or auto-refractor.
Subjective refraction - A subjective refraction requires responses from the patient. Typically, the patient will sit behind a phoropter or wear a trial frame and look at an eye chart. The eye care professional will change lenses and other settings while asking the patient for feedback on which set of lenses give the best vision.
Cycloplegic refraction - Sometimes, eye care professionals prefer to obtain a cycloplegic refraction, especially when trying to obtain an accurate refraction in young children who may skew refraction measurements by adjusting their eyes with accommodation. Cycloplegic eye drops are applied to the eye to temporarily paralyze the ciliary muscle of the eye.
Pupil function - An examination of pupilary function includes inspecting the pupils for equal size (1 mm or less of difference may be normal), regular shape, reactivity to light, and direct and consensual accommodation. These steps can be easily remembered with the mnemonic PERRLA (D+C): Pupils Equal and Round; Reactive to Light and Accommodation (Direct and Consensual).
Ocular motility - Ocular motility should always be tested, especially when patients complain of double vision or physicians suspect neurologic disease.
Visual field (confrontation) testing - Testing the visual fields consists of confrontation field testing in which each eye is tested separately to assess the extent of the peripheral field.
Slit-lamp - Close inspection of the anterior eye structures and ocular adnexa are often done with a slit lamp which is a table mounted microscope with a special adjustable illumination source attached.
Intraocular pressure - Intraocular pressure (IOP) can be measured by Tonometry devices. The eye can be thought of as an enclosed compartment through which there is a constant circulation of fluid that maintains its shape and internal pressure.
Retinal examination - Examination of retina (fundus examination) is an important part of the general eye examination.
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Journal of optometry : open access