Refractive error is the most common cause of reduced clarity of vision (visual acuity) and may be a readily treatable component of poor vision in patients with other diagnoses.
Use of a pinhole will overcome most refractive errors and thus allows their identification as a cause of reduced visual acuity.

Treatment

Contact Lenses

An estimated 40.9 million US adults wear contact lenses, mostly for correction of refractive errors, for which they provide better optical correction than glasses.
Decorative contact lenses are increasingly being used.
The major risk from contact lens wear is corneal infection, potentially a blinding condition.
Such infections occur more often with soft lenses, particularly extended wear, for which there is at least a fivefold increase in risk of corneal infection compared with daily wear. Decorative contact lenses have a high prevalence of microbial contamination.
Contact lens wearers should be made aware of the risks they face and ways to minimize them, such as avoiding overnight wear or use of lenses past their replacement date and maintaining meticulous lens hygiene, including not using tap water or saliva for lens cleaning.
Contact lenses should be removed whenever there is ocular discomfort or redness.

Surgery

Various surgical techniques are available to reduce refractive errors, particularly nearsightedness.Laser corneal refractive surgery reshapes the middle layer (stroma) of the cornea with an excimer laser.
Other refractive surgery techniques are extraction of the clear crystalline lens with insertion of a single vision, multifocal, or accommodative intraocular lens; insertion of an intraocular lens without removal of the crystalline lens (phakic intraocular lens); intrastromal corneal ring segments (INTACS); collagen cross-linking; laser thermal keratoplasty; and conductive keratoplasty (CK). Topical atropine and pirenzepine, a selective muscarinic antagonist; rigid contact lens wear during sleep (orthokeratology); and various types of soft contact lenses and spectacles reduce the rate of progression of nearsightedness but their long-term efficacy and safety are uncertain.

When to Refer

Any contact lens wearer with an acute painful red eye must be referred emergently to an ophthalmologist.