Blindness: The inability to see. The limiting of one or more of the basic functions of the eye: visual acuity, dark adaptation, color vision, or peripheral vision. These may result from EYE DISEASES; OPTIC NERVE DISEASES; VISUAL PATHWAY diseases; OCCIPITAL LOBE diseases; OCULAR MOTILITY DISORDERS; and other conditions.
The condition of lacking visual perception due to physiological or neurological factors.
There are over 50 definitions of blindness worldwide. The World Health Organization definition of blindness is less than 3/60 in the better seeing eye. This means that the better seeing eye cannot read the top letter on the Snellen visual acuity chart at three meters.
Visual Impairment: Reduced vision as a result of a disorder or disease of the eye or brain.
Signs and symptoms of low vision or blindness
- Crossed or turned eye
- Pupils that are excessively large or small
- Nystagmus (eyes that bounce around, dancing eyes, or strange eye movements)
- Delays in reaching developmental milestones
- Not tracking objects by three or four months
- Doesn’t blink at sudden bright lights
- Not interested in books or brightly colored toys
- Doesn’t reach for things placed in front of him or her
- Turning or tilting head to look at an object
- Eye pressing (rubbing or poking eyes)
- Not making eye contact
- Self-stimulating activities such as rocking, bouncing, and head nodding
There are MANY conditions that affect the eyes and vision. I will list some of them below. Please be sure to check out the LINKS section to find more information.
Amblyopia- A condition in which a person's vision does not develop properly in early childhood because the eye and the brain are not working together correctly. Amblyopia, which usually affects only one eye, is also known as "lazy eye." A person with amblyopia experiences blurred vision in the affected eye. However, children often do not complain of blurred vision in the amblyopic eye because this seems normal to them. Early treatment is advisable, because if left untreated, this condition may lead to permanent vision problems or even partial blindness. Treatment options include vision therapy exercises, prescription eyeglasses, or surgery. People with amblyopia may need to wear an eye patch over their stronger eye in order to force the affected eye to function as it should.
- Anopthalmia- Rare condition in which one or both eyes do not form during pregnancy. When both eyes are affected, blindness results. Prosthetic eyes can promote proper growth of the eye sockets and development of facial bones and also serve cosmetic purposes
- Astigmatism- Common vision condition, caused by an irregularly curved cornea or lens. People with astigmatism may experience blurred vision, eyestrain, or headaches. Can be corrected with eyeglasses, contact lenses, or corrective surger.
- Cataract- A condition in which the lens of the eye, which is normally clear, becomes cloudy or opaque.
- Coloboma- A cleft or gap in some part of the eye, such as the iris, lens, or retina, that is caused by a defect in the development of the eyeball.Children whose vision is impaired by coloboma may benefit from using reading materials that have large black print and well-spaced letters and words. They may also find it helpful to read one line at a time with the aid of a cutout reading window.
- Cortical visual impairment- Visual impairment caused by damage to the part of the brain related to vision. Although the eye is normal, the brain cannot properly process the information it receives. The degree of vision loss may be mild or severe and can vary greatly, even from day to day. Cortical visual impairment may be temporary or permanent. People with cortical visual impairment have difficulty using what their eye sees. For example, they may have trouble recognizing faces, interpreting drawings, perceiving depth, or distinguishing between background and foreground. Children with cortical visual impairment are often able to see better when told in advance what to look for.
- DeMorsier's Syndrome- Rare disorder, present at birth, in which the optic nerve is underdeveloped, the pituitary gland does not function properly, and often a portion of brain tissue is not formed. De Morsier's Syndrome isalso known as septo-optic dysplasia. It may cause blindness in one or both eyes and is also often accompanied by nystagmus and various other symptoms. Some children with De Morsier's Syndrome have normal intelligence, while others may be developmentally delayed, learning-disabled, or mentally retarded.
- Nystagmus- Condition that involves involuntary, rapid, repetitive movements of one or both eyes from side to side, up and down, or in a circular motion. Children with nystagmus may frequently lose their place when reading. Placing a cutout reading window over words or using a card to "underline" text can be helpful.
- Optic nerve atrophy- Degeneration of the optic nerve, which carries vision information from the eye to the brain. People who have optic nerve atrophy may have dimmed or blurred vision as well as a reduced field of vision. They may also have difficulty seeing contrast and fine detail. Vision loss through optic nerve atrophy is permanent. However, if the underlying cause can be identified and successfully treated, further vision loss may be prevented. Bright lighting, high contrast, and bold colors can help children with optic nerve atrophy see more clearly.
- Optic nerve hypoplasia- Condition, present at birth, in which the optic nerve is underdeveloped, so that adequate visual information is not carried from the eye to the brain. The effects of optic nerve hypoplasia have a broad range, from little or no visual impairment to near-total blindness. The condition may affect one or both eyes.
- Retinoblastoma- Malignant tumor (cancer) of the retina, generally affecting children under the age of 6. Usually hereditary, retinoblastoma may affect one or both eyes. Retinoblastoma has a cure rate of over 90 percent if treated early. Without prompt treatment, the cancer can spread to the eye socket, the brain, and elsewhere, and can cause death. Depending on the size and location of the tumor, treatment options include laser surgery, cryotherapy (a freezing treatment), radiation, and chemotherapy. In some cases, the affected eye may need to be removed.
- Retinopathy of prematurity (ROP)- Condition associated with premature birth, in which the growth of normal blood vessels in the retina stops, and abnormal blood vessels develop. As a result, the infant has an increased risk of detachment of the retina. Retinopathy of prematurity can lead to reduced vision or blindness. Laser therapy can help this condition if diagnosis and treatment occur early. Children who experience minor effects may benefit from the use of devices for low vision as they get older. Retinopathy of prematurity was formerly called retrolental fibroplasia.
- Strabismus- Condition in which the eyes are not both directed toward the same point simultaneously. Strabismus occurs when eye muscles are not working together properly. It is most commonly an inherited condition, but may also be caused by disease or injury. If diagnosed early, strabismus can usually be corrected. The condition may be treated with corrective eyeglasses, eye-muscle exercises, surgery, or a combination of these approaches. Young children with this condition may need to wear an eye patch over their stronger eye to force their weaker eye to function correctly. Children whose strabismus is not corrected may develop amblyopia.