Coloboma
Encyclopedia
A coloboma is a hole in one of the structures of the eye
, such as the iris
, retina
, choroid
or optic disc
. The hole is present from birth and can be caused when a gap called the choroid fissure between two structures in the eye, which is present early in development in the uterus
, fails to close up completely before a child is born. The classical description in medical literature is of a key-hole shaped defect. A coloboma can occur in one or both eyes.
or optic nerve
is missing, vision may be poor and a large part of the visual field may be missing. This is more likely to cause problems with mobility if the lower visual field is absent. Other conditions can be associated with a coloboma. Sometimes the eye may be reduced in size, a condition called microphthalmia
, or there may be glaucoma
, nystagmus, scotoma
or strabismus
.
, in which coloboma is associated with cleft lip and/or palate, ear abnormalities and hearing impairment, choanal atresia
, delays in growth and development, central nervous system
anomalies, lesser vision in extreme or little light and congenital heart defects. It can also be associated with Klinefelter Syndrome and Marfan syndrome.
of coloboma is estimated at around 0.5 to 0.7 per 10,000 births, making it a relatively rare condition.
Perhaps the most famous people with coloboma are John Ritter
, Henry Cavill
, Danielle Minton, New York Times columnist Andrew Ross Sorkin
, alternative rock singer songwriter Lachi and Madeleine McCann. McCann, a British girl, disappeared from the vacation resort rented by her parents in May 2007 just before her fourth birthday. Posters and online campaigns promoting the search for Madeleine use the word "Look" with the first "O" in the word being drawn in the shape of a coloboma radius extending from the pupil at the 7 o'clock position.
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
, such as the iris
Iris (anatomy)
The iris is a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupils and thus the amount of light reaching the retina. "Eye color" is the color of the iris, which can be green, blue, or brown. In some cases it can be hazel , grey, violet, or even pink...
, retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...
, choroid
Choroid
The choroid, also known as the choroidea or choroid coat, is the vascular layer of the eye, containing connective tissue, and lying between the retina and the sclera. The human choroid is thickest at the far extreme rear of the eye , while in the outlying areas it narrows to 0.1 mm...
or optic disc
Optic disc
The optic disc or optic nerve head is the location where ganglion cell axons exit the eye to form the optic nerve. There are no light sensitive rods or cones to respond to a light stimulus at this point. This causes a break in the visual field called "the blind spot" or the "physiological blind spot"...
. The hole is present from birth and can be caused when a gap called the choroid fissure between two structures in the eye, which is present early in development in the uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
, fails to close up completely before a child is born. The classical description in medical literature is of a key-hole shaped defect. A coloboma can occur in one or both eyes.
Presentation
The effects a coloboma has on the vision can be mild or more severe depending on the size and location of the gap. If, for example, only a small part of the iris is missing, vision may be normal, whereas if a large part of the retinaRetina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...
or optic nerve
Optic nerve
The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of...
is missing, vision may be poor and a large part of the visual field may be missing. This is more likely to cause problems with mobility if the lower visual field is absent. Other conditions can be associated with a coloboma. Sometimes the eye may be reduced in size, a condition called microphthalmia
Microphthalmia
Microphthalmia also referred to as microphthalmos, nanophthalmia or nanophthalmos, is a developmental disorder of the eye that literally means small eye...
, or there may be glaucoma
Glaucoma
Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently damaging vision in the affected eye and progressing to complete blindness if untreated. It is often, but not always, associated with increased pressure of the fluid in the eye...
, nystagmus, scotoma
Scotoma
A scotoma is an area of partial alteration in one's field of vision consisting of a partially diminished or entirely degenerated visual acuity which is surrounded by a field of normal - or relatively well-preserved - vision.Every normal mammalian eye has a scotoma in its field of vision, usually...
or strabismus
Strabismus
Strabismus is a condition in which the eyes are not properly aligned with each other. It typically involves a lack of coordination between the extraocular muscles, which prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely...
.
Related conditions
Some children with coloboma of the eye also have malformations in other parts of the body. There is a rare condition called CHARGE syndromeCHARGE syndrome
CHARGE syndrome , is a syndrome caused by a genetic disorder. It was first described in 1979.In 1981, the term "CHARGE" came into use as an acronym for the set of unusual congenital features seen in a number of newborn children...
, in which coloboma is associated with cleft lip and/or palate, ear abnormalities and hearing impairment, choanal atresia
Choanal atresia
Choanal atresia is a congenital disorder where the back of the nasal passage is blocked, usually by abnormal bony or soft tissue formed during fetal development.-Presentation:It can be unilateral or bilateral....
, delays in growth and development, central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
anomalies, lesser vision in extreme or little light and congenital heart defects. It can also be associated with Klinefelter Syndrome and Marfan syndrome.
Incidence
The incidenceIncidence (epidemiology)
Incidence is a measure of the risk of developing some new condition within a specified period of time. Although sometimes loosely expressed simply as the number of new cases during some time period, it is better expressed as a proportion or a rate with a denominator.Incidence proportion is the...
of coloboma is estimated at around 0.5 to 0.7 per 10,000 births, making it a relatively rare condition.
Perhaps the most famous people with coloboma are John Ritter
John Ritter
Jonathan Southworth "John" Ritter was an American actor, voice over artist and comedian perhaps best known for having played Jack Tripper and Paul Hennessy in the ABC sitcoms Three's Company and 8 Simple Rules, respectively...
, Henry Cavill
Henry Cavill
Henry William Dalgliesh Cavill is a British actor. He has appeared in the films The Count of Monte Cristo and Stardust, and played the role of Charles Brandon, 1st Duke of Suffolk, on the Showtime series The Tudors, from 2007 until 2010...
, Danielle Minton, New York Times columnist Andrew Ross Sorkin
Andrew Ross Sorkin
Andrew Ross Sorkin is a Gerald Loeb Award-winning American journalist, author and television personality. He is a financial columnist for The New York Times and a co-anchor of CNBC's Squawk Box. He is also the founder and editor of DealBook, a financial news service published by The New York Times...
, alternative rock singer songwriter Lachi and Madeleine McCann. McCann, a British girl, disappeared from the vacation resort rented by her parents in May 2007 just before her fourth birthday. Posters and online campaigns promoting the search for Madeleine use the word "Look" with the first "O" in the word being drawn in the shape of a coloboma radius extending from the pupil at the 7 o'clock position.