Ametropia (from Greek ametros, "disproportionate", "irregular" + -opia, "sight") describes a condition of the eye in which images fail to come to a proper focus on the retina, due to a discrepancy between the size and refractive powers of the eye.

Ametropia requires visual correction (most commonly spectacles and contact lenses) and should not be confused with emmetropia, which results in clear uncorrected vision.

Ametropia is the collective name for any deviation in the relaxed focus of the eye from the normal state in which distant objects form sharp and clear images on the retina. If you are not emmetropic, then you have a refractive error and referred to as ametropic. Ametropia is treated with spectacles, contact lenses and in some cases by means of surgical intervention.

There are several classifications of ametropia and at their simplest form can be categorized as the various types of commonly known refractive errors, as follows:

Myopia or short-sightedness

Hyperopia or far-sightedness

Astigmatism

Presbyopia

All of which requires optical intervention, most commonly spectacles and contact lenses to restore clear vision.

There has been some research on causal factors involved in the development of ametropia. In particular, statistics show that prolonged near work correlates with the development of myopia, but it is still unclear whether there is a causal relation.Furthermore, outdoor activity has been found to have a protective effect on myopia development in children.

The most common symptom associated with uncorrected ametropia is blurred vision or eyestrain. Children with ametropia are often unaware that they have reduced vision until they discover that other children see better than they can. For example, many school children first notice that they cannot read from the projector or chalkboard as well as their classmates. For others who never report a problem, poor vision is first detected during vision screening or comprehensive eye and vision examination.

Blurred vision and the inability to see detail may be the hallmarks of ametropia, yet other symptoms include:

Decreased concentration levels

Focusing delays

Fatigue or drowsiness

Ocular discomfort

Headaches

Asthenopia

Squinting

Increased working distance

A need for brighter light for reading

Diplopia (double vision)

The evaluation and management of ametropia is important because significant functional deficits can occur when the condition is left untreated. Furthermore, ametropia is not a static condition and frequently motivates the individual to seek eye care, presenting the optometrist with the opportunity to check for the presence of other disorders, some of which might threaten sight or life. This opportunity underscores the public health benefit of comprehensive optometric care for patients with ametropia.
As primary eye care providers, optometrists have the expertise to examine, diagnose, treat, and manage a wide variety of eye and vision problems.

For patients requiring other health care services related to systemic conditions detected in the course of their eye examination, the optometrist becomes the point of entry into the broader health care system. Under corrected or uncorrected ametopia can cause significant visual disability and have a negative impact on the patient's quality of life. Gaining an understanding of the patient's specific vocational and avocational visual requirements helps the optometrist recommend the treatment most appropriate for enhancing visual performance.

A variety of options are available for optical correction of ametropia, dependent on ocular health, patient's specific vocational and avocational needs, the following spectacle treatment methods for ametropia include:

Single vision lenses

Accomodative support lenses

Bifocal lenses

Multifocal lenses

Near progressive lenses

Occupational lenses

All types of corrections for ametropia represent some visual compromise, compared with clear uncorrected vision. Ultimately, the success of treatment depends on the lens power, the optical correction, the specific visual tasks, characteristics of the individual patient, and the appropriate patient education given by the practitioner.

Optical correction with contact lenses can be used for correction of ametropia and include the following:

Spherical contact lenses

Toric contact lenses

Monovision contact lenses

Bifocal/ Multifocal contact lenses

Enhanced monovision lenses

It is of the utmost importance that contact lenses wearers alternate between contact lenses and spectacles to ensure the corneal health is not compromised in the long-term. With the significant advancements in contact lens technology over the past decade, many more patients have a positive outcome with contact lenses for either full or part-time visual correction.