Optic disc drusen
Encyclopedia
Optic disc drusen or optic nerve head drusen (ONHD) are globules of mucoprotein
s and mucopolysaccharides that progressively calcify in the optic disc
. They are thought to be the remnants of the axonal transport system of degenerated retinal ganglion cells.
ODD have also been referred to as congenitally elevated or anomalous discs, pseudopapilledema, pseudoneuritis, buried disc drusen, and disc hyaline
bodies. They may be associated with vision loss of varying degree occasionally resulting in blindness.
is a cable connection that transmits images from the retina
to the brain
. It consists of over one million retinal ganglion cell axon
s. The optic nerve head, or optic disc
is the anterior end of the nerve that is in the eye and hence is visible with an ophthalmoscope. It is located nasally and slightly inferior to the macula
of the eye. There is a blind spot
at the optic disc because there are no rods
or cones
beneath it to detect light. The central retinal artery and vein can be seen in the middle of the disc as it exits the scleral canal
with the optic nerve to supply the retina. The vessels send branches out in all directions to supply the retina.
are the most susceptible ethnic group. Certain conditions have been associated with disc drusen such as retinitis pigmentosa
, angioid streaks
, Usher syndrome
, Noonan syndrome
and Alagille syndrome
. Optic disc drusen are not related to Bruch membrane drusen of the retina
which have been associated with age-related macular degeneration
.
al neovascularization may develop as the juxtapapillary nerve fibers are disrupted, with subsequent subretinal hemorrhage and retinal scarring. Even more rarely, vitreous
hemorrhage may develop.
. Anterior ischemic optic neuropathy
(AION) is a potential complication.
which could imply raised intracranial pressure or tumors. True papilledema may present with exudates or cotton-wool spots, unlike ODD. The optic disc margins are characteristically irregular in ODD but not blurred as there is no swelling of the retinal nerve fibers. Spontaneous venous pulsations are present in about 80 percent of patients with ODD, but absent in cases of true disc edema. Other causes of disc elevation clinicians must exclude may be: hyaloid traction, epipapillary glial tissue, myelinated nerve fibres, scleral infiltration, vitreopapillary traction and high hyperopia
. Disorders associated with disc elevation include: Alagille syndrome
, Down syndrome
, Kenny-Caffey syndrome, Leber Hereditary Optic Neuropathy and linear nevus sebaceous syndrome.
, contrast sensitivity, color vision
, intraocular pressure
and threshold visual fields
. For those with visual field defects optical coherence tomography
has been recommended for follow up of nerve fiber layer
thickness. Associated conditions such as angioid streaks and retinitis pigmentosa
should be screened for. Both the severity of optic disk drusen and the degree of intraocular pressure elevation have been associated with visual field loss. There is no widely accepted treatment for ODD, although some clinicians will prescribe eye drops designed to decrease the intra-ocular pressure and theoretically relieve mechanical stress on fibers of the optic disc. Rarely choroidal neovascular membranes may develop adjacent to the optic disc threatening bleeding and retinal scarring. Laser treatment or photodynamic therapy or other evolving therapies may prevent this complication.
Mucoprotein
A mucoprotein is a glycoprotein composed primarily of mucopolysaccharides. It can be found in the synovial fluid of the knees....
s and mucopolysaccharides that progressively calcify in the 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"...
. They are thought to be the remnants of the axonal transport system of degenerated retinal ganglion cells.
ODD have also been referred to as congenitally elevated or anomalous discs, pseudopapilledema, pseudoneuritis, buried disc drusen, and disc hyaline
Hyaline
The term hyaline denotes a substance with a glass-like appearance.-Histopathology:In histopathological medical usage, a hyaline substance appears glassy and pink after being stained with haematoxylin and eosin — usually it is an acellular, proteinaceous material...
bodies. They may be associated with vision loss of varying degree occasionally resulting in blindness.
Anatomy
The optic nerveOptic 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 a cable connection that transmits images from the 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...
to the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
. It consists of over one million retinal ganglion cell axon
Axon
An axon is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron's cell body or soma....
s. The optic nerve head, 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"...
is the anterior end of the nerve that is in the eye and hence is visible with an ophthalmoscope. It is located nasally and slightly inferior to the macula
Macula
The macula or macula lutea is an oval-shaped highly pigmented yellow spot near the center of the retina of the human eye. It has a diameter of around 5 mm and is often histologically defined as having two or more layers of ganglion cells...
of the eye. There is a blind spot
Blind spot
Blind spot may refer to:In ophthalmology:*Scotoma, an obscuration of the visual field*Optic disc, also known as the anatomical blind spot, the specific region of the retina where the optic nerve and blood vessels pass through to connect to the back of the eye*Blind spot , also known as the...
at the optic disc because there are no rods
Rod cell
Rod cells, or rods, are photoreceptor cells in the retina of the eye that can function in less intense light than can the other type of visual photoreceptor, cone cells. Named for their cylindrical shape, rods are concentrated at the outer edges of the retina and are used in peripheral vision. On...
or cones
Cone cell
Cone cells, or cones, are photoreceptor cells in the retina of the eye that are responsible for color vision; they function best in relatively bright light, as opposed to rod cells that work better in dim light. If the retina is exposed to an intense visual stimulus, a negative afterimage will be...
beneath it to detect light. The central retinal artery and vein can be seen in the middle of the disc as it exits the scleral canal
Sclera
The sclera , also known as the white or white of the eye, is the opaque , fibrous, protective, outer layer of the eye containing collagen and elastic fiber. In the development of the embryo, the sclera is derived from the neural crest...
with the optic nerve to supply the retina. The vessels send branches out in all directions to supply the retina.
Epidemiology
Optic disc drusen are found clinically in about 1% of the population but this increases to 3.4% in individuals with a family history of ODD. About two thirds to three quarters of clinical cases are bilateral. A necropsy study of 737 cases showed a 2.4% incidence with 2 out of 15 (13%) bilateral, perhaps indicating the insidious nature of many cases. An autosomal dominant inheritance pattern with incomplete penetrance and associated inherited dysplasia of the optic disc and its blood supply is suspected. Males and females are affected at equal rates. CaucasiansCaucasian race
The term Caucasian race has been used to denote the general physical type of some or all of the populations of Europe, North Africa, the Horn of Africa, Western Asia , Central Asia and South Asia...
are the most susceptible ethnic group. Certain conditions have been associated with disc drusen such as retinitis pigmentosa
Retinitis pigmentosa
Retinitis pigmentosa is a group of genetic eye conditions that leads to incurable blindness. In the progression of symptoms for RP, night blindness generally precedes tunnel vision by years or even decades. Many people with RP do not become legally blind until their 40s or 50s and retain some...
, angioid streaks
Angioid streaks
Angioid streaks, also called Knapp streaks or Knapp striae are small breaks in Bruch's membrane, an elastic tissue containing membrane of the retina that can become calcified and crack....
, Usher syndrome
Usher syndrome
Usher syndrome is a relatively rare genetic disorder that is a leading cause of deafblindness and that is associated with a mutation in any one of 10 genes. Other names for Usher syndrome include Hallgren syndrome, Usher-Hallgren syndrome, rp-dysacusis syndrome and dystrophia retinae dysacusis...
, Noonan syndrome
Noonan syndrome
Noonan Syndrome is a relatively common autosomal dominant congenital disorder considered to be a type of dwarfism, that affects both males and females equally. It used to be referred to as the male version of Turner's syndrome ; however, the genetic causes of Noonan syndrome and Turner syndrome...
and Alagille syndrome
Alagille syndrome
Alagille syndrome is a genetic disorder that affects the liver, heart, kidney, and other systems of the body. Problems associated with the disorder generally become evident in infancy or early childhood...
. Optic disc drusen are not related to Bruch membrane drusen of the retina
Drusen
Drusen are tiny yellow or white accumulations of extracellular material that build up in Bruch's membrane of the eye. The presence of a few small drusen is normal with advancing age, and most people over 40 have some hard drusen...
which have been associated with age-related macular degeneration
Macular degeneration
Age-related macular degeneration is a medical condition which usually affects older adults and results in a loss of vision in the center of the visual field because of damage to the retina. It occurs in “dry” and “wet” forms. It is a major cause of blindness and visual impairment in older adults...
.
Pathophysiology
In children, optic disc drusen are usually buried and undectectable by fundoscopy except for a mild or moderate elevation of the optic disc. With age, the overlying axons become atrophied and the drusen become exposed and more visible. They may become apparent with an ophthalmoscope and some visual field loss at the end of adolescence. ODD can compress and eventually compromise the vasculature and retinal nerve fibers. Rarely, choroidChoroid
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...
al neovascularization may develop as the juxtapapillary nerve fibers are disrupted, with subsequent subretinal hemorrhage and retinal scarring. Even more rarely, vitreous
Vitreous humour
The vitreous humour or vitreous humor is the clear gel that fills the space between the lens and the retina of the eyeball of humans and other vertebrates...
hemorrhage may develop.
Prognosis
Optic nerve damage is progressive and insidious. Eventually 75% of patients will develop some peripheral field defects. These can include nasal step defects, enlarged blind spots, arcuate scotomas, sectoral field loss and altitudinal defects. Clinical symptoms correlate to visibility of the drusen. Central vision loss is a rare complication of bleeding from peripapillar choroidal neovascular membranesChoroidal neovascularization
Choroidal neovascularization is the creation of new blood vessels in the choroid layer of the eye. This is a common symptom of the degenerative maculopathy wet AMD .-Causes:...
. Anterior ischemic optic neuropathy
Anterior ischemic optic neuropathy
Anterior ischemic optic neuropathy is a medical condition involving loss of vision due to damage to the optic nerve from insufficient blood supply. AION is generally divided into two types: arteritic AION and non-arteritic AION...
(AION) is a potential complication.
Differential diagnosis
In most patients, optic disc drusen are an incidental finding. It is important to differentiate them from other conditions that present with optic disc elevation, especially papilledemaPapilledema
Papilledema is optic disc swelling that is caused by increased intracranial pressure. The swelling is usually bilateral and can occur over a period of hours to weeks. Unilateral presentation is extremely rare....
which could imply raised intracranial pressure or tumors. True papilledema may present with exudates or cotton-wool spots, unlike ODD. The optic disc margins are characteristically irregular in ODD but not blurred as there is no swelling of the retinal nerve fibers. Spontaneous venous pulsations are present in about 80 percent of patients with ODD, but absent in cases of true disc edema. Other causes of disc elevation clinicians must exclude may be: hyaloid traction, epipapillary glial tissue, myelinated nerve fibres, scleral infiltration, vitreopapillary traction and high hyperopia
Hyperopia
Hyperopia, also known as farsightedness, longsightedness or hypermetropia, is a defect of vision caused by an imperfection in the eye , causing difficulty focusing on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance...
. Disorders associated with disc elevation include: Alagille syndrome
Alagille syndrome
Alagille syndrome is a genetic disorder that affects the liver, heart, kidney, and other systems of the body. Problems associated with the disorder generally become evident in infancy or early childhood...
, Down syndrome
Down syndrome
Down syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th...
, Kenny-Caffey syndrome, Leber Hereditary Optic Neuropathy and linear nevus sebaceous syndrome.
Management
Patients with optic disc drusen should be monitored periodically for fundoscopy, Snellen acuityVisual acuity
Visual acuity is acuteness or clearness of vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain....
, contrast sensitivity, color vision
Color vision
Color vision is the capacity of an organism or machine to distinguish objects based on the wavelengths of the light they reflect, emit, or transmit...
, intraocular pressure
Intraocular pressure
Intraocular pressure is the fluid pressure inside the eye. Tonometry is the method eye care professionals use to determine this. IOP is an important aspect in the evaluation of patients at risk from glaucoma...
and threshold visual fields
Perimetry
Perimetry or campimetry is the systematic measurement of differential light sensitivity in the visual field by the detection of the presence of test targets on a defined background. Visual field testing can be performed clinically with confrontational field testing keeping the subject's gaze fixed...
. For those with visual field defects optical coherence tomography
Optical coherence tomography
Optical coherence tomography is an optical signal acquisition and processing method. It captures micrometer-resolution, three-dimensional images from within optical scattering media . Optical coherence tomography is an interferometric technique, typically employing near-infrared light...
has been recommended for follow up of nerve fiber layer
Nerve fiber layer
The retinal nerve fiber layer is formed by the expansion of the fibers of the optic nerve; it is thickest near the porus opticus, gradually diminishing toward the ora serrata....
thickness. Associated conditions such as angioid streaks and retinitis pigmentosa
Retinitis pigmentosa
Retinitis pigmentosa is a group of genetic eye conditions that leads to incurable blindness. In the progression of symptoms for RP, night blindness generally precedes tunnel vision by years or even decades. Many people with RP do not become legally blind until their 40s or 50s and retain some...
should be screened for. Both the severity of optic disk drusen and the degree of intraocular pressure elevation have been associated with visual field loss. There is no widely accepted treatment for ODD, although some clinicians will prescribe eye drops designed to decrease the intra-ocular pressure and theoretically relieve mechanical stress on fibers of the optic disc. Rarely choroidal neovascular membranes may develop adjacent to the optic disc threatening bleeding and retinal scarring. Laser treatment or photodynamic therapy or other evolving therapies may prevent this complication.
External links
- North American Neuro-Ophthalmological Society: Patient Information on Drusen
- Vishal Patel and Thomas A. Oetting, MD. Optic Nerve Drusen: 19 year-old female with blurred vision. August 14, 2007 U of Iowa eye rounds case study