Emmetropia (Normal Vision)

Emmetropia, colloquially known as normal vision or right vision, is the ideal optical condition of the eyes. Deviations from emmetropia are referred to as ametropias, more commonly known as refractive errors.

In this state, a bundle of light rays from an infinitely distant object strikes the point of sharpest vision (fovea) on the retina without any accommodative effort. Keep reading to discover the definition of emmetropia, what makes perfect vision and more.

What is Emmetropia (Normal Vision)?

The meaning of emmetropia refers to the optical ideal condition, or perfect vision. The state of normal vision occurs when light rays from an optically infinitely distant object strike a single point on the retina at the place of sharpest vision, the macula (fovea), without any accommodative effort by the eye. This without any visual aid.

The light rays are converted into electrical signals here and reach the brain via the optic nerve. The brain then creates the image. The following illustration shows the path of the light rays and their impact on the retina in emmetropia.

How Common is Emmetropia?

Many people wonder ‘what is 20/20 vision’. It is rather rare for someone to have perfect vision, or be emmetropic.

Rather than having 20/20 vision, most people have slight refractive errors, corrected or uncorrected. This is quite normal and can be corrected with glasses, contact lenses, or eye laser treatment. More than half of the population relies on visual aids, and this number is expected to increase in the coming years. According to a survey by the Association of Optics Switzerland, even 4 out of 5 people in Switzerland rely on visual aids. Regular eye tests are important to discover and treat refractive errors.

What Are Common Abnormalities of Emmetropia?

The most common ametropias, or refractive errors, are myopia (nearsightedness), hyperopia (farsightedness), astigmatism (cylindrical error), and, in a broader sense, presbyopia (age-related farsightedness). Many of these conditions can be managed with proper eye care and treatment.

Myopia

In myopia, the light rays meet in front of the retina, causing distant objects to appear blurry.

Hyperopia

In hyperopia, the light rays meet behind the retina, allowing individuals to see distant objects clearly while nearby objects appear blurry and out of focus, or can only be seen clearly with significant eye strain.

Astigmatism

People with astigmatism, colloquially known as cylindrical error or corneal curvature, have a distorted view of object shapes. Since astigmatism often occurs in combination with hyperopia and myopia, vision can also be blurry at various distances.

Presbyopia

Unlike the other refractive errors, presbyopia is not really a refractive error but an ageing process of the eye's lens. The elasticity and thus the adaptability of the lens decreases with age. People notice, gradually from the age of 45, that nearby objects appear blurry. Presbyopia can be corrected with glasses or a refractive lens exchange.