Decreased retinal arteriolar diameters, which may decrease blood flow and slow oxygen delivery to regions of the retina.

Excessive sensitivity to light with the sensation of discomfort or pain in the eyes due to exposure to bright light.

Repetitive pressing, poking, and/or rubbing in the eyes.

A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age.

Intellectual disability, previously referred to as mental retardation, is characterized by subnormal intellectual functioning that occurs during the developmental period. It is defined by an IQ score below 70.

A form of strabismus with one or both eyes deviated outward.

An abnormality of refraction characterized by the ability to see objects in the distance clearly, while objects nearby appear blurry.

A cone-shaped deformity of the cornea characterized by the presence of corneal distortion secondary to thinning of the apex.

Nearsightedness, also known as myopia, is an eye condition that causes blurry distance vision. People who are nearsighted have more trouble seeing things that are far away (such as when driving) than things that are close up (such as when reading or using a computer). If it is not treated with corrective lenses or surgery, nearsightedness can lead to squinting, eyestrain, headaches, and significant visual impairment.\n\nNearsightedness usually begins in childhood or adolescence. It tends to worsen with age until adulthood, when it may stop getting worse (stabilize). In some people, nearsightedness improves in later adulthood.\n\nFor normal vision, light passes through the clear cornea at the front of the eye and is focused by the lens onto the surface of the retina, which is the lining of the back of the eye that contains light-sensing cells. People who are nearsighted typically have eyeballs that are too long from front to back. As a result, light entering the eye is focused too far forward, in front of the retina instead of on its surface. It is this change that causes distant objects to appear blurry. The longer the eyeball is, the farther forward light rays will be focused and the more severely nearsighted a person will be.\n\nNearsightedness is measured by how powerful a lens must be to correct it. The standard unit of lens power is called a diopter. Negative (minus) powered lenses are used to correct nearsightedness. The more severe a person's nearsightedness, the larger the number of diopters required for correction. In an individual with nearsightedness, one eye may be more nearsighted than the other.\n\nEye doctors often refer to nearsightedness less than -5 or -6 diopters as "common myopia." Nearsightedness of -6 diopters or more is commonly called "high myopia." This distinction is important because high myopia increases a person's risk of developing other eye problems that can lead to permanent vision loss or blindness. These problems include tearing and detachment of the retina, clouding of the lens (cataract), and an eye disease called glaucoma that is usually related to increased pressure within the eye. The risk of these other eye problems increases with the severity of the nearsightedness. The term "pathological myopia" is used to describe cases in which high myopia leads to tissue damage within the eye.

Inability to see well at night or in poor light.

Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms.

Atrophy of the optic nerve. Optic atrophy results from the death of the retinal ganglion cell axons that comprise the optic nerve and manifesting as a pale optic nerve on fundoscopy.

A nonspecific term denoting degeneration of the retinal pigment epithelium and/or retinal photoreceptor cells.

A misalignment of the eyes so that the visual axes deviate from bifoveal fixation. The classification of strabismus may be based on a number of features including the relative position of the eyes, whether the deviation is latent or manifest, intermittent or constant, concomitant or otherwise and according to the age of onset and the relevance of any associated refractive error.

A cataract is an opacity or clouding that develops in the crystalline lens of the eye or in its capsule.

An anomaly in the ability to discriminate between or recognize colors.

Diminished clarity of vision.

An absolute or relative decrease in retinal sensitivity extending from edge (periphery) of the visual field in a concentric pattern. The visual field is the area that is perceived simultaneously by a fixating eye.

Rhythmic, involuntary sinusoidal oscillations of one or both eyes. The waveform of pendular nystagmus may occur in any direction.

Cornea plana is an abnormally flat shape of the cornea such that the normal protrusion of the cornea from the sclera is missing. The reduced corneal curvature can lead to hyperopia, and a hazy corneal limbus and arcus lipoides may develop at an early age.

Presence of multiple yellowish-white lesions of various size and configuration on the retina not related to vascular lesions.

Lack of the foveal reflex, which normally occurs as a result of the reflection of light from the ophthalmoscope in the foveal pit upon examination. The foveal reflex is a bright pinpoint of light that is observed to move sideways or up and down in response to movement of the opthalmoscope.

Well-demarcated area(s) of partial or complete depigmentation in the macula, reflecting atrophy of the retinal pigment epithelium with associated retinal photoreceptor loss.

Any abnormality of the electrical responses of various cell types in the retina as measured by electroretinography.

The presence of small, white vitreous opacities consisting of calcium phosphate and complex, layered lipid deposits.

A pale yellow discoloration of the optic disc (the area of the optic nerve head in the retina). The optic disc normally has a pinkish hue with a central yellowish depression.

A type of cataract affecting the posterior pole of lens immediately adjacent to ('beneath') the Lens capsule.

Severe reduction of the ability to see. On the 6m visual acuity scale, severe reduction is defined as less than 6/60 but at least 3/60. On the 20ft visual acuity scale, severe reduction is defined as less than 20/200 but at least 20/400. On the decimal visual acuity scale, severe reduction is defined as less than 0.1 but at least 0.05.

Moderate reduction of the ability to see. On the 6m visual acuity scale, moderate reduction is defined as less than 6/18 but at least 6/60. On the 20ft visual acuity scale, moderate reduction is defined as less than 20/70 but at least 20/200. On the decimal visual acuity scale, moderate reduction is defined as less than 0.3 but at least 0.1.

Progressive maculopathy characterized by concentric regions of hyper- and hypo-pigmentation.

Pigment migration into the retina in a bone-spicule configuration (resembling the nucleated cells within the lacuna of bone).

Lack of any response to stimulation upon electroretinography.

A severe form of hypermetropia with over +5.00 diopters.

Mottling (spots or blotches with different shades) of the retinal pigment epithelium, i.e., localized or generalized fundal pigment granularity associated with processes at the level of the retinal pigment epithelium.

Reduced anteroposterior thickness of the retina. This phenotype can be appreciated by retinal optical coherence tomography (OCT).

Reduced velocity and acceleration in the pupillary light response.

Any structural anomaly of the vitreous body.

Atrophy of the choroid and retinal layers of the fundus.

Partial or complete loss of foveal tissue that was once present.

A reduction in visual acuity with best corrected visual acuity between 1.40 (20/500) and 1.89 logMAR (up to roughly 20/1590).