Refraction Vision Test
Norm of Refraction Vision Test
Emmetropia or no refractive error.
| Refractive power of human eye, without accommodation: | 58 diopters | |
| Refractive power of structures of eye: | ||
| Cornea | 44 diopters | |
| Aqueous humor | 44 diopters | |
| Lens | 10–14 diopters | |
Usage of Refraction Vision Test
Assists in the evaluation of visual acuity; diagnosis of ametropias (refractive errors), including astigmatism, hyperopia (farsightedness), and myopia (nearsightedness); and determination of need for prescription of corrective lenses.
Description of Refraction Vision Test
Refraction is the process by which light rays entering the eye bend or pass obliquely over the curved surfaces of the eye (cornea, aqueous humor, lens, and vitreous humor), which have differing densities. Clear images are produced as a point of light is focused directly on the retina. The refraction vision test is only one of a series of procedures included in a full ophthalmologic eye examination. This test alone cannot diagnose eye disease.
Professional Considerations of Refraction Vision Test
Consent form NOT required.
Risks
Allergic reaction to eye drops (itching, hives, rash, tight feeling in the throat, shortness of breath, bronchospasm, anaphylaxis, death).
Contraindications
Previous allergy to mydriatic drops; narrow-angle glaucoma.
Preparation
- Eye drops may be placed in both eyes to dilate the pupils and to prevent lens accommodation during the examination.
Procedure
- The examiner locates the pupillary opening with a retinoscope and then assesses for stasis of the red-orange retinal reflection of the retinoscope light.
- Brightness, clarity, shape, size, vascularity, and uniformity of the retina are observed.
- A variety of lenses with varying lens powers are inserted into the client's test glasses.
- This process continues until the lens power that best neutralizes retinal reflex motion, produces the most clarity and brightness, and produces the most consistently correct reading of a visual chart is determined.
Postprocedure Care
- See Client and Family Teaching.
Client and Family Teaching
- This is a simple eye test to determine if you do or do not need corrective lenses.
- Bring sunglasses to wear after the procedure.
- Do not drive or operate any machinery until distance vision returns.
Factors That Affect Results
- Inadequate pupil dilation, excessive lens accommodation, or incomplete cooperation of the client prevents accurate results.
Other Data
- Most clients show some degree of ametropia or refractive error.
