Bietti crystalline dystrophy (BCD) is an inherited eye disease that can lead to night blindness and other problems seeing. The disease is named for Dr. G. B. Bietti, an Italian ophthalmologist, who described three patients with similar symptoms in 1937. Read about causes, symptoms, and treatment for this rare disease.
Glistening crystalline-like lesions at posterior pole of retina in patient with Bietti crystalline dystrophy. Fundus also shows atrophic-like changes of RPE and patchy atrophic change of choriocapillaris vessels. Clumping of retinal pigment is also apparent.
Bietti crystalline dystrophy is a disorder in which numerous small, yellow or white crystal-like deposits of fatty (lipid) compounds accumulate in the light-sensitive tissue that lines the back of the eye (the retina). The deposits damage the retina, resulting in progressive vision loss.
People with Bietti crystalline dystrophy typically begin noticing vision problems in their teens or twenties. They experience a loss of sharp vision (reduction in visual acuity) and difficulty seeing in dim light (night blindness). They usually lose areas of vision (visual field loss), most often side (peripheral) vision. Color vision may also be impaired.
The vision problems may worsen at different rates in each eye, and the severity and progression of symptoms varies widely among affected individuals, even within the same family. However, most people with this condition become legally blind by their forties or fifties. Most affected individuals retain some degree of vision, usually in the center of the visual field, although it is typically blurry and cannot be corrected by glasses or contact lenses. Vision impairment that cannot be improved with corrective lenses is called low vision.
Source: MedlinePlus Genetics
What Is Bietti’s Crystalline Dystrophy?
Bietti Crystalline Dystrophy
Image by Mansour 2017
Bietti Crystalline Dystrophy
Shiny, yellow-white crystalline deposits present in posterior pole of right eye retina
Image by Mansour 2017
What Is Bietti’s Crystalline Dystrophy?
Bietti’s crystalline dystrophy (BCD) is a rare genetic disease. In BCD, crystals made of fatty acids build up in your cornea (the clear outer layer at the front of the eye) and your retina (the light-sensitive layer of tissue in the back of the eye).
People with BCD may first notice symptoms in their teens or twenties, like trouble seeing in low light or out of the corners of the eyes. Over time, this leads to vision loss.
There is currently no proven treatment for BCD, but vision rehabilitation can help you make the most of your vision.
Source: National Eye Institute (NEI)
Causes
Newborn autosomal recessive pattern of inheritance
Image by Thomas Shafee and TheVisualMD
Newborn autosomal recessive pattern of inheritance
Newborn autosomal recessive pattern of inheritance
Image by Thomas Shafee and TheVisualMD
Genes and Bietti’s Crystalline Dystrophy
Bietti’s crystalline dystrophy (BCD) is a rare disease that happens when crystals made of fatty acids build up in your cornea (clear outer layer at the front of the eye) and retina (light-sensitive layer of tissue in the back of the eye).
BCD is an inherited genetic disease, which means that parents pass it down to their children. If you have BCD or it runs in your family, you can get tested for the BCD gene to learn more about the risk of passing it to your child.
How do genes cause BCD?
BCD is caused by changes in a gene called CYP4V2. Experts think this gene affects how the body uses fatty acids, but they’re still studying how this works.
In most cases, you can only get BCD if you have 2 copies of this abnormal (changed) BCD gene — usually 1 inherited from each parent. This type of inheritance is called autosomal recessive inheritance.
If you only inherit 1 abnormal BCD gene and your other copy is normal, you won’t have symptoms of the disease. People with only 1 copy of the abnormal gene are called carriers.
If I have the BCD gene, will I pass it down to my child?
If you have BCD, you’ll always pass down 1 copy of the abnormal gene to each of your children. If you’re a BCD carrier, you have a 1 in 2 chance of passing down the gene to each child.
But your children will only have symptoms if they have a second copy of the abnormal BCD gene. In fact, if 2 BCD carriers have a child together, that child has a 1 in 4 chance of having symptoms of BCD.
Can I get tested for the BCD gene?
Yes, there are genetic tests for the CYP4V2 gene that causes BCD.
If you have BCD or it runs in your family, you can talk with your doctor or a specialist called a genetic counselor to learn more about the risk of passing BCD down to your child.
Source: National Eye Institute (NEI)
CYP4V2 Gene
Ideogram of human chromosome 4
Image by Office of Biological and Environmental Research of the U.S. Department of Energy Office of Science, the Biological and Environmental Research Information System, Oak Ridge National Laboratory.
Ideogram of human chromosome 4
Selected genes, traits, and disorders associated with the chromosome listed; (blue and violet) regions reflecting the unique patterns of light and dark bands seen on human chromosomes stained to allow viewing through a light microscope; (red) the centromere, or constricted portion, of each chromosome; (yellow) chromosomal regions that vary in staining intensity and sometimes are called hererochromatin (meaning “different color”); (lines between yellow) variable regions, called stalks, that connect a very small chromosome arm (a “satellite”) to the chromosome.
Image by Office of Biological and Environmental Research of the U.S. Department of Energy Office of Science, the Biological and Environmental Research Information System, Oak Ridge National Laboratory.
CYP4V2 Gene: Cytochrome P450 Family 4 Subfamily V Member 2
Normal Function
The CYP4V2 gene provides instructions for making a member of the cytochrome P450 family of enzymes. These enzymes are involved in the formation and breakdown of various molecules and chemicals within cells. The CYP4V2 enzyme is involved in a multi-step process called fatty acid oxidation in which fats are broken down and converted into energy, but the enzyme's specific function is not well understood.
Health Conditions Related to Genetic Changes
Bietti crystalline dystrophy
At least 42 CYP4V2 gene mutations have been identified in people with Bietti crystalline dystrophy, a disorder in which numerous small, yellow or white crystal-like deposits of fatty (lipid) compounds accumulate in the light-sensitive tissue that lines the back of the eye (the retina). The deposits damage the retina, resulting in progressive vision loss.
CYP4V2 gene mutations that cause Bietti crystalline dystrophy are predicted to change the structure of the CYP4V2 enzyme in a way that reduces or eliminates its activity. The mutations likely affect lipid breakdown; however, it is unknown how they lead to the specific signs and symptoms of Bietti crystalline dystrophy. For unknown reasons, the severity of the signs and symptoms differs significantly among individuals with the same CYP4V2 gene mutation.
Other disorders
Certain common variations (polymorphisms) in the CYP4V2 gene have been associated with an increased risk of a type of blood clot called a deep venous thrombosis (DVT). DVTs occur most often in the deep veins of the legs or arms. If these clots travel through the bloodstream, they can lodge in the lungs and cause a life-threatening complication called a pulmonary embolism. While nearby genes on chromosome 4 are known to be involved in blood clotting, it is unclear how the CYP4V2 gene variations may affect this process.
Other Names for This Gene
BCD
CP4V2_HUMAN
CYP4AH1
cytochrome P450 4V2
cytochrome P450, family 4, subfamily V, polypeptide 2
Genomic Location
The CYP4V2 gene is found on chromosome 4.
Source: MedlinePlus Genetics
Inheritance
autosomal recessive pattern of inheritance
Image by Thomas Shafee and TheVisualMD
autosomal recessive pattern of inheritance
Newborn autosomal recessive pattern of inheritance
Autosomal recessive inheritance is the most common type of inheritance for retinal dystrophies. When this type of condition is present in a family, it is often seen only in one child or in siblings, not in the parents or other relatives.
As shown in the figure, to have symptoms of Bietti's Crystalline Dystrophy (BCD), an individual must have two copies of the same disease gene. We all have two copies of each gene, since we inherit one from our father and one from our mother.
In the figure above, the N stands for the normal copy of the BCD gene and the B stands for the abnormal copy of the BCD gene. Both parents have an N gene and a B gene and are therefore called “carriers.” In this scenario, there is a 75 percent chance that a child will not have BCD. In each child there is a 50 percent chance to inherit the N gene and a 50 percent chance to inherit the B gene from each parent. There is:
a 25 percent chance that a child will inherit both N genes and be unaffected
a 50 percent chance that a child will inherit one N gene and one B gene and be unaffected, but be a carrier of the mutant gene
a 25 percent chance for a child to inherit both B genes and be affected
These recessive genes can be passed on for generations without causing disease, since two copies are needed to cause symptoms.
Source: National Eye Institute (NEI)
Symptoms
Depiction of a person with blurry vision
Image by https://www.myupchar.com
Depiction of a person with blurry vision
Depiction of a person with blurry vision
Image by https://www.myupchar.com
What Are the Symptoms of Bietti's Crystalline Dystrophy?
The first symptom of BCD is usually a change in your vision. You may notice that you don’t see as clearly as you used to. This includes:
Blurry or hazy vision
Trouble seeing in low light
Not being able to see things out of the corner of your eye (peripheral vision)
Trouble seeing certain colors
This condition affects both eyes but 1 eye may get worse more quickly than the other.
These early symptoms get worse over time. Eventually, most people with BCD lose most or all of their vision. Many people with BCD can still see things in the center of their vision, but this vision is often blurry.
Source: National Eye Institute (NEI)
Diagnosis
Dilated Pupil / Undilated Pupil
Undilated Pupil / Dilated Pupil
Interactive by National Eye Institute, National Institutes of Health
Dilated Pupil / Undilated Pupil
Undilated Pupil / Dilated Pupil
Undilated Pupil / Dilated Pupil - Portions of the retina that can be seen through an undilated versus a dilated pupil.
Interactive by National Eye Institute, National Institutes of Health
How Will My Eye Doctor Check for Bietti's Crystalline Dystrophy?
Your eye doctor can check for BCD during a comprehensive dilated eye exam. The exam is simple and painless — your doctor will give you some eye drops to dilate (widen) your pupil and then check for eye disease.
Your eye doctor may also use genetic testing to confirm that you have BCD. These tests check for changes in the gene that causes BCD (CYP4V gene2).
Source: National Eye Institute (NEI)
Additional Materials (2)
Undilated Pupil / Dilated Pupil
Undilated Pupil / Dilated Pupil
Dilated and Undilated Pupil - Portions of the retina that can be seen through an undilated versus a dilated pupil.
Interactive by National Eye Institute, National Institutes of Health
An undilated pupil / A dilated pupil
An Undilated Pupil and Dilated Pupil
An Undilated Pupil and Dilated Pupil
Interactive by National Eye Institute (NEI)
Undilated Pupil / Dilated Pupil
National Eye Institute, National Institutes of Health
An Undilated Pupil and Dilated Pupil
National Eye Institute (NEI)
Dilated Eye Exam
Dilated Eye Exam
Also called: Comprehensive Dilated Eye Exam, Dilated Fundus Exam
A dilated eye exam is the best thing you can do for your eye health. It’s the only way to check for eye diseases early on, when they’re easier to treat — and before they cause vision loss. Learn what happens during and after a dilated eye exam and how often you need one.
Dilated Eye Exam
Also called: Comprehensive Dilated Eye Exam, Dilated Fundus Exam
A dilated eye exam is the best thing you can do for your eye health. It’s the only way to check for eye diseases early on, when they’re easier to treat — and before they cause vision loss. Learn what happens during and after a dilated eye exam and how often you need one.
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Use the slider below to see how your results affect your
health.
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0.125
0.32
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Your result is Normal vision.
US: 20/25 to 20/12 (Metric: 6/7.5 to 6/4)
Visual acuity is expressed as a decimal or a fraction. 1 = US 20/20 or metric 6/6 is considered optimal vision.
The top number refers to the distance you stand from the chart. This is often 20 feet (6 meters).
The bottom number indicates the distance at which a person with normal eyesight could read the same line you correctly read.
Related conditions
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Use the slider below to see how your results affect your
health.
Your result is Normal.
The peripheral vision is normal.
Related conditions
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Use the slider below to see how your results affect your
health.
Your result is Normal.
A normal result indicates normal movement of the eyes in all directions.
Related conditions
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Use the slider below to see how your results affect your
health.
Your result is Normal.
A normal result means the status of your optic nerve and retina is in good shape.
Related conditions
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Use the slider below to see how your results affect your
health.
Your result is Pass.
A pass or normal result means that the pupils dilate (get larger) when room light is dimmed; the pupils are round and equal in size, in both bright and dim light; and the pupils quickly and symmetrically constrict to a bright light directed into either of the eyes and when the bright light swings between the two eyes.
Related conditions
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Use the slider below to see how your results affect your
health.
mm Hg
10
21
Your result is Normal.
A normal result means your eye pressure is within the normal range. However, the thickness of your cornea can affect measurements. A corneal thickness measurement (pachymetry) is needed to get a correct pressure measurement.
Related conditions
A dilated eye exam is the best thing you can do for your eye health! It’s the only way to check for eye diseases early on, when they’re easier to treat — and before they cause vision loss.
The exam is simple and painless. Your eye doctor will check for vision problems that make it hard to see clearly, like being nearsighted or farsighted. Then your doctor will give you some eye drops to dilate (widen) your pupil and check for eye diseases.
Since many eye diseases have no symptoms or warning signs, you could have a problem and not know it. Even if you think your eyes are healthy, getting a dilated eye exam is the only way to know for sure.
How often you need a dilated eye exam depends on your risk for eye disease. Talk to your doctor about what’s right for you.
Get a dilated eye exam every 1 to 2 years if you:
Are over age 60
Are African American and over age 40
Have a family history of glaucoma
If you have diabetes or high blood pressure, ask your doctor how often you need an exam. Most people with diabetes or high blood pressure need to get a dilated eye exam at least once a year.
The exam includes:
A visual acuity test to check how clearly you see. Your doctor will ask you to read letters that are up close and far away.
A visual field test to check your peripheral (side) vision. Your doctor will test how well you can see objects off to the sides of your vision without moving your eyes.
An eye muscle function test to check for problems with the muscles around your eyeballs. Your doctor will move an object around and ask you to follow it with your eyes.
A pupil response test to check how light enters your eyes. Your doctor will shine a small flashlight into your eyes and check how your pupils react to the light.
A tonometry test to measure the pressure in your eyes. Your doctor will use a machine to blow a quick puff of air onto your eye, or gently touch your eye with a special tool. Don’t worry — it doesn’t hurt!
Dilation to check for problems with the inner parts of your eye. Your doctor will give you some eye drops to dilate (widen) your pupil. This helps the doctor see inside your eye.
Depending on your needs, your doctor may include other tests too. Ask your doctor if you have questions.
Dilating your pupil lets more light into your eye — just like opening a door lets light into a dark room. Dilation helps your eye doctor check for many common eye problems, including diabetic retinopathy, glaucoma, and age-related macular degeneration (AMD).
For a few hours after a dilated eye exam, your vision may be blurry and you may be sensitive to light. Ask a friend or family member to drive you home from your appointment.
If your eye doctor finds refractive errors in your vision, you may get a prescription for eyeglasses or contact lenses to help you see more clearly.
Bring your sunglasses!
Your eyes may be sensitive to light for a few hours after your exam. Sunglasses can help, so bring them if you have them! Your eye doctor may also have disposable sunglasses they can give you.
If your eye doctor finds signs of an eye disease, you can talk about treatment options and decide what’s right for you. Learn more about these common eye diseases:
Diabetic eye disease
Age-related macular degeneration
Cataract
Glaucoma
If you’re seeing clearly and there are no signs of eye disease, you’re all set until your next exam. Make an appointment for your next dilated eye exam before you leave the office — that way, you won’t forget!
Additional Materials (50)
Comprehensive Dilated Eye Exam
Video by National Eye Institute, NIH/YouTube
Animation: Detecting age-related macular degeneration through a dilated eye exam.
Video by National Eye Institute, NIH/YouTube
Animation: Detecting diabetic retinopathy through a dilated eye exam
Video by National Eye Institute, NIH/YouTube
What are dilating eye drops?
Video by EyeSmart — American Academy of Ophthalmology/YouTube
Dilated fundus examination
Diagram of the Eye Before and After Dilated Eye Exam
Image by National Eye Institute (NEI), National Institutes of Health (NIH)
Pupillary response
Pupillary response : Animation that illustrates the pupillary light reflex. When the light is turned on, the pupil reacts by constricting.
Image by Greyson Orlando
Right Eyeball
3D visualization based on scanned human data of the right eyeball.
Image by TheVisualMD
Tangier disease
Diffuse hazy opacity of the right cornea in the patient with Tangier disease
Image by National Eye Institute
Pupil
The pupil is the central transparent area (showing as black). The grey/blue area surrounding it is the iris. The white outer area is the sclera, the central transparent part of which is the cornea.
Image by ROTFLOLEB
Mydriasis
Mydriasis, pupillary response
Image by OpenStax College
Intraocular lens
Cataract surgery performed, IOL inserted. Note incision right of dilated pupil.
Image by Janke
Drawing of a woman having her eyes examined by a doctor using a machine
See your eye doctor for a dilated eye exam every year. Early treatment of eye problems can help save your sight.
Image by NIDDK Image Library
Two-sided Adie's pupils of unknown etiology identified by an ophthalmologist
Two-sided Adie's pupils of unknown etiology identified by an ophthalmologist
Image by Casper
Ehlers-Danlos Syndrome
The patient was a four-year-old female who was first seen three months before with a two day history of swelling of the upper lid of the left eye and lower lid of the right eye. This was apparently due to some skin eruption. The patient was also thought to have congenital glaucoma and the sclerae were noted to be blue. The corneas also protruded anteriorly and it was thought the patient might possibly have keratoconus. The patient was thought to have the syndrome of blue sclerotics with a high myopic astigmatism. Incidentally, the parents were first cousins. Generally, the patient had a brachycephaly, there was no nystagmus and the heart was normal. The patient was thought to possibly have osteogenesis imperfecta. She was also thought to have the typical physique of Marfan's, but the lenses were not dislocated. She had blue sclerae ([1], [2]) and keratoconus and she was -6.00 to -8.00 diopters myopic. It appeared that the patient had type VI Ehler's Danlos syndrome on the basis of the blue sclera, high myopia and keratoconus.
Image by National Eye Institute
Sensitive content
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Slit Lamp Exam
Maj. Ivy Madson, 99th Air Base Squadron optometry flight commander, uses a Slit Lamp to examine the interior of the eye during an exam for Airman 1st Class Hunter, 18th Reconnaissance Squadron Airman, Jan. 13, 2015, at Creech Air Force Base, Nevada. The Creech Medical Aid Station now offers optometry services to all personnel assigned to Creech AFB Tuesdays from 7:30 a.m. to 3 p.m. (Last names have been withheld for security purposes). (U.S. Air Force photo by Staff Sgt. Adawn Kelsey/Released)
Image by U.S. Air Force photo by Staff Sgt. Adawn Kelsey/Released
Mydriasis
Mydriasis, pupillary response. Dilated pupils after an optometrist appointment.
Image by Nutschig at en.wikipedia
Drawing of an eye with a dilated pupil
None
Image by NIDDK Image Library
Child's Eye Exam
Lenses placed in a trial frame help determine eyeglass prescription.
Image by National Eye Institute, National Institutes of Health
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Eye exam
Capt. Luanne Danes uses a light to check the anterior segment of Master Sgt. Timothy Vanderhoff's eye during his visit to the Optometry Clinic Nov. 19, 2009, Eielson Air Force Base, Alaska. Captain Danes is looking for healthy structure of the eye and ensuring no corneal disease is present. Captain Danes, officer in charge of Optometry, is assigned to the 354th Medical Operation Squadron. Sergeant Vanderhoff, crew chief, is assigned to the 168th Aircraft Maintenance Squadron. (U.S. Air Force photo/Staff Sgt. Christopher Boitz)
Image by U.S. Air Force photo/Staff Sgt. Christopher Boitz
Eye exam
U.S. Navy Lt. Patricia Salazar examines a patient's eyes at a Continuing Promise medical clinic set up by staff assigned to the hospital ship USNS Comfort in Paita, Peru
Image by Petty Officer 1st Class Brian A. Goyak, U.S. Navy
Dilated fundus examination - Before
The same eye as File:Result of Dilated fundus examination.JPG, but before examination
Image by Nicko va
Pupil
Dilated and Undilated Pupil - Portions of the retina that can be seen through an undilated versus a dilated pupil.
Image by National Eye Institute, National Institutes of Health
Dilated fundus examination - After
Result of Dilated fundus examination
Image by Nicko va
Dilated fundus examination
This is my dilated pupil, an hour or two after getting drops put in them so the optometrist could examine my retinas. Pupil dilated using the anticholinergic drug tropicamide.
Image by grendel|khan and Lady Byron
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Baby Eye Exam
Maj. Renee Vincent shows Taylor, 1, an ophthalmoscope during an exam. The 341st Medical Group has a total of 21 technicians and 24 nurses serving approximately 10,000 beneficiaries at Malmstrom. Major Vincent is the 341st Missile Wing’s pediatric advisor, commander of the 341st Medical Operations Squadron’s Maternal Child Flight, and a certified pediatric nurse practitioner for the 341st MDG. (U.S. Air Force photo/Staff Sgt. Marcus McDonald)
Image by U.S. Air Force photo/Staff Sgt. Marcus McDonald
Optical Coherence Tomography
A detailed cross-sectional image of the back of the eye is obtained using an optical coherence tomography (OCT).
Image by National Eye Institute, National Institutes of Health
Iris (anatomy)
Image by Shanon
Fundus Photography
An eye care professional takes fundus autofluorescence photographs to study the retina.
Image by National Eye Institute, National Institutes of Health
Drawing of an eye with a dilated pupil
Dilated eye
Image by NIDDK Image Library
An undilated pupil and dilated pupil
Dilating your pupil lets more light into your eye — just like opening a door lets light into a dark room. Dilation helps your eye doctor check for many common eye problems, including diabetic retinopathy, glaucoma, and age-related macular degeneration (AMD).
Image by National Eye Institute (NEI)
Get a dilated eye exam
A dilated eye exam is the best thing you can do for your eye health. It’s the only way to check for eye diseases early on, when they’re easier to treat — and before they cause vision loss.
Image by National Eye Institute (NEI)
Get a dilated eye exam
A dilated eye exam is the best thing you can do for your eye health. It’s the only way to check for eye diseases early on, when they’re easier to treat — and before they cause vision loss.
Image by National Eye Institute (NEI)
Get a dilated eye exam
A dilated eye exam is the best thing you can do for your eye health. It’s the only way to check for eye diseases early on, when they’re easier to treat — and before they cause vision loss.
Image by National Eye Institute (NEI)
Get a dilated eye exam
A dilated eye exam is the best thing you can do for your eye health. It’s the only way to check for eye diseases early on, when they’re easier to treat — and before they cause vision loss.
Image by National Eye Institute (NEI)
Get a dilated eye exam
A dilated eye exam is the best thing you can do for your eye health. It’s the only way to check for eye diseases early on, when they’re easier to treat — and before they cause vision loss.
Image by National Eye Institute (NEI)
Get a dilated eye exam
A dilated eye exam is the best thing you can do for your eye health. It’s the only way to check for eye diseases early on, when they’re easier to treat — and before they cause vision loss.
Image by National Eye Institute (NEI)
Get a dilated eye exam
A dilated eye exam is the best thing you can do for your eye health. It’s the only way to check for eye diseases early on, when they’re easier to treat — and before they cause vision loss.
Image by National Eye Institute (NEI)
Get a dilated eye exam
A dilated eye exam is the best thing you can do for your eye health. It’s the only way to check for eye diseases early on, when they’re easier to treat — and before they cause vision loss.
Image by National Eye Institute (NEI)
Get a dilated eye exam
A dilated eye exam is the best thing you can do for your eye health. It’s the only way to check for eye diseases early on, when they’re easier to treat — and before they cause vision loss.
Image by National Eye Institute (NEI)
Woman checking her glasses
Image by National Eye Institute (NEI)
Vision with age-related macular degeneration
Image by National Eye Institute (NEI)
Vision with cataract
Image by National Eye Institute (NEI)
Vision with diabetic rethinopathy
Image by National Eye Institute (NEI)
Vision with glaucoma
Vision with glaucoma
Image by National Eye Institute (NEI)
Healthy Eyes
Image by National Eye Institute (NEI)
Healthy Eyes
Image by National Eye Institute (NEI)
Healthy Eyes
Image by National Eye Institute (NEI)
Healthy Eyes
Image by National Eye Institute (NEI)
Healthy Eyes
Image by National Eye Institute (NEI)
Get a dilated eye exam
A dilated eye exam is the best thing you can do for your eye health. It’s the only way to check for eye diseases early on, when they’re easier to treat — and before they cause vision loss.
Image by National Eye Institute (NEI)
2:19
Comprehensive Dilated Eye Exam
National Eye Institute, NIH/YouTube
1:56
Animation: Detecting age-related macular degeneration through a dilated eye exam.
National Eye Institute, NIH/YouTube
1:53
Animation: Detecting diabetic retinopathy through a dilated eye exam
National Eye Institute, NIH/YouTube
1:12
What are dilating eye drops?
EyeSmart — American Academy of Ophthalmology/YouTube
Dilated fundus examination
National Eye Institute (NEI), National Institutes of Health (NIH)
Pupillary response
Greyson Orlando
Right Eyeball
TheVisualMD
Tangier disease
National Eye Institute
Pupil
ROTFLOLEB
Mydriasis
OpenStax College
Intraocular lens
Janke
Drawing of a woman having her eyes examined by a doctor using a machine
NIDDK Image Library
Two-sided Adie's pupils of unknown etiology identified by an ophthalmologist
Casper
Ehlers-Danlos Syndrome
National Eye Institute
Sensitive content
This media may include sensitive content
Slit Lamp Exam
U.S. Air Force photo by Staff Sgt. Adawn Kelsey/Released
Mydriasis
Nutschig at en.wikipedia
Drawing of an eye with a dilated pupil
NIDDK Image Library
Child's Eye Exam
National Eye Institute, National Institutes of Health
Sensitive content
This media may include sensitive content
Eye exam
U.S. Air Force photo/Staff Sgt. Christopher Boitz
Eye exam
Petty Officer 1st Class Brian A. Goyak, U.S. Navy
Dilated fundus examination - Before
Nicko va
Pupil
National Eye Institute, National Institutes of Health
Dilated fundus examination - After
Nicko va
Dilated fundus examination
grendel|khan and Lady Byron
Sensitive content
This media may include sensitive content
Baby Eye Exam
U.S. Air Force photo/Staff Sgt. Marcus McDonald
Optical Coherence Tomography
National Eye Institute, National Institutes of Health
Iris (anatomy)
Shanon
Fundus Photography
National Eye Institute, National Institutes of Health
Drawing of an eye with a dilated pupil
NIDDK Image Library
An undilated pupil and dilated pupil
National Eye Institute (NEI)
Get a dilated eye exam
National Eye Institute (NEI)
Get a dilated eye exam
National Eye Institute (NEI)
Get a dilated eye exam
National Eye Institute (NEI)
Get a dilated eye exam
National Eye Institute (NEI)
Get a dilated eye exam
National Eye Institute (NEI)
Get a dilated eye exam
National Eye Institute (NEI)
Get a dilated eye exam
National Eye Institute (NEI)
Get a dilated eye exam
National Eye Institute (NEI)
Get a dilated eye exam
National Eye Institute (NEI)
Woman checking her glasses
National Eye Institute (NEI)
Vision with age-related macular degeneration
National Eye Institute (NEI)
Vision with cataract
National Eye Institute (NEI)
Vision with diabetic rethinopathy
National Eye Institute (NEI)
Vision with glaucoma
National Eye Institute (NEI)
Healthy Eyes
National Eye Institute (NEI)
Healthy Eyes
National Eye Institute (NEI)
Healthy Eyes
National Eye Institute (NEI)
Healthy Eyes
National Eye Institute (NEI)
Healthy Eyes
National Eye Institute (NEI)
Get a dilated eye exam
National Eye Institute (NEI)
Genetic Testing
Genetic Testing
Also called: DNA Testing, Mutation Screening, Genetic Test
Genetic testing is a type of test that analyze your cells or tissue to look for any changes in your DNA. Genetic tests may be used to identify increased risks of health problems, to choose treatments, or to assess responses to treatments.
Genetic Testing
Also called: DNA Testing, Mutation Screening, Genetic Test
Genetic testing is a type of test that analyze your cells or tissue to look for any changes in your DNA. Genetic tests may be used to identify increased risks of health problems, to choose treatments, or to assess responses to treatments.
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Use the slider below to see how your results affect your
health.
Your result is Negative.
A negative result means that the test did not find a genetic change known to cause disease.
Related conditions
Genetic testing looks for changes, sometimes called mutations or variants, in your DNA. Genetic testing is useful in many areas of medicine and can change the medical care you or your family member receives. For example, genetic testing can provide a diagnosis for a genetic condition such as Fragile X or information about your risk to develop cancer. There are many different kinds of genetic tests. There is no single genetic test that can detect all genetic conditions. The approach to genetic testing is individualized based on your medical and family history and what condition you’re being tested for.
Genetic tests are done using a blood or saliva sample and results are usually ready in a few weeks. Because we share DNA with our family members, if you are found to have a genetic change, your family members may have the same change. Genetic counseling before and after genetic testing can help make sure that you are the right person in your family to get a genetic test, you’re getting the right genetic test, and that you understand your results.
Genetic testing may be done for many different reasons, including to:
Find genetic diseases in unborn babies. This is one type of prenatal testing.
Screen newborn babies for certain treatable conditions
Lower the risk of genetic diseases in embryos that were created using assisted reproductive technology
Find out if you carry a gene for a certain disease that could be passed on to your children. This is called carrier testing.
See whether you are at increased risk of developing a specific disease. This may be done for a disease that runs in your family.
Diagnose certain diseases
Identify genetic changes that may be causing or contributing to a disease that you were already diagnosed with
Figure out how severe a disease is
Help guide your doctor in deciding the best medicine and dosage for you. This is called pharmacogenomic testing.
Genetic tests are often done on a blood or saliva sample. But they may also be done on samples of hair, skin, amniotic fluid (the fluid that surrounds a fetus during pregnancy), or other tissue. The sample is sent to a laboratory. There, a lab technician will use one of several different techniques to look for genetic changes.
For a blood test, a health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
For a saliva test, ask your health care provider for instructions on how to provide your sample.
You don't need any special preparations for genetic testing. But you may want to meet with a genetic counselor first to see if the test is right for you. Your counselor may talk with you about the risks and benefits of genetic testing and what different results can mean.
You should also think about getting genetic counseling after your test. Your counselor can discuss how your results may impact you and your family, both medically and emotionally.
There are no known risks to having a saliva test. There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
The physical risks of the different types of genetic testing are small. But there can be emotional, social, or financial drawbacks:
Depending on the results, you may feel angry, depressed, anxious, or guilty. This can be especially true if you are diagnosed with a disease that does not have effective treatments.
You may be worried about genetic discrimination in employment or insurance
Genetic testing may give you limited information about a genetic disease. For example, it cannot tell you whether you will have symptoms, how severe a disease might be, or whether a disease will get worse over time.
Some genetic tests are expensive, and health insurance might only cover part of the cost. Or they may not cover it at all.
Positive – the test found a genetic change known to cause disease.
Negative – the test did not find a genetic change known to cause disease. Sometimes a negative result occurs when the wrong test was ordered or there isn’t a genetic cause for that person’s symptoms. A “true negative” is when there is a known genetic change in the family and the person tested did not inherit it. If your test results are negative and there is no known genetic change in your family, a negative test result may not give you a definite answer. This is because you might not have been tested for the genetic change that runs in your family.
Uncertain – a variant of unknown or uncertain significance means there isn’t enough information about that genetic change to determine whether it is benign (normal) or pathogenic (disease causing).
A good way to think about genetic testing is as if you’re asking the DNA a question. Sometimes we don’t find an answer because we weren’t asking the right question or science just didn’t have the answer yet.
Genetic Testing | CDC. Sep 23, 2022 [accessed on Feb 23, 2022]
Genetic Testing: MedlinePlus. National Library of Medicine. Jun 11, 2021 [accessed on Feb 23, 2022]
What is genetic testing?: MedlinePlus Genetics [accessed on Feb 23, 2022]
Genetic Testing FAQ. Genome.gov [accessed on Feb 23, 2022]
Genetic testing and your cancer risk: MedlinePlus Medical Encyclopedia [accessed on Feb 23, 2022]
Normal reference ranges can vary depending on the laboratory and the method used for testing. You must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."
Additional Materials (21)
Genetic testing
Genetic testing fact sheet
Image by genome.gov
Genetic testing
Genetic testing existed before the Human Genome Project and the list of diseases that we can already screen for may be longer than you think.
Image by TheVisualMD
Genes and Genetic Defects
Genetic testing isn't new. In the 1960s, doctors were able to test newborn babies for certain rare single-gene disorders, such as phenylketonuria (PKU), a rare metabolic disease that causes mental retardation. (PKU can be prevented with a special diet if it's detected early, which was why it was critical to test newborns.)
Image by TheVisualMD
Mapping Your Future: Screening for Disease Risk
Image by TheVisualMD
Each person with Down syndrome has different talents and the ability to thrive.
Down syndrome is a lifelong condition. Services early in life will often help babies and children with Down syndrome to improve their physical and intellectual abilities. Most of these services focus on helping children with Down syndrome develop to their full potential. These services include speech, occupational, and physical therapy, and they are typically offered through early intervention programs in each state. Children with Down syndrome may also need extra help or attention in school, although many children are included in regular classes.
Image by CDC
genetic analysis
Biotechnology - DNA analysis and treatment
Image by OpenClipart-Vectors/Pixabay
Family history (medicine)
An extended family in Spain
Image by Ojedamd
Biotechnology
This diagram shows the basic method used for extraction of DNA.
Image by CNX Openstax
Genetic Counselor at Sanford Health Explains the Benefits to Genetic Testing
Video by Sanford Health/YouTube
What Is A Genetic Counselor & The Importance of Genetic Counselling | Ambry Genetics
Video by Ambry Genetics/YouTube
How Does The Genetic Testing Process Work? Genetic Testing FAQ | Ambry Genetics
Video by Ambry Genetics/YouTube
Should You Get Genetic Testing During Your Pregnancy?
Video by St. Louis Children's Hospital/YouTube
Debating Embryonic Genetic Testing -- The Doctors
Video by The Doctors/YouTube
Genetic Testing for Cancer — AMITA Health | NBC Chicago Ask the Doc
Video by AMITA Health/YouTube
MedGenome BRCA - Breast Cancer Genetic Testing
Video by MedGenome/YouTube
Genetic Testing for Hereditary Forms of Kidney Cancer - Brian Shuch, MD
Video by UCLA Health/YouTube
Do I need Genetic Testing for Ichthyosis?
Video by foundation for ichthyosis/YouTube
What Is Genetic Testing? Understanding the Process and Its Results
Video by uvahealth/YouTube
How to Understand Your Genetic Testing Results
Video by Breast Cancer Answers®/YouTube
Genetic Testing 101 for People with Rare Diseases
Video by National Organization for Rare Disorders (NORD)/YouTube
What's the difference between genetic and genomic testing?
Video by Cancer Treatment Centers of America - CTCA/YouTube
Genetic testing
genome.gov
Genetic testing
TheVisualMD
Genes and Genetic Defects
TheVisualMD
Mapping Your Future: Screening for Disease Risk
TheVisualMD
Each person with Down syndrome has different talents and the ability to thrive.
CDC
genetic analysis
OpenClipart-Vectors/Pixabay
Family history (medicine)
Ojedamd
Biotechnology
CNX Openstax
1:57
Genetic Counselor at Sanford Health Explains the Benefits to Genetic Testing
Sanford Health/YouTube
1:06
What Is A Genetic Counselor & The Importance of Genetic Counselling | Ambry Genetics
Ambry Genetics/YouTube
0:45
How Does The Genetic Testing Process Work? Genetic Testing FAQ | Ambry Genetics
Ambry Genetics/YouTube
3:04
Should You Get Genetic Testing During Your Pregnancy?
St. Louis Children's Hospital/YouTube
4:40
Debating Embryonic Genetic Testing -- The Doctors
The Doctors/YouTube
1:31
Genetic Testing for Cancer — AMITA Health | NBC Chicago Ask the Doc
AMITA Health/YouTube
2:10
MedGenome BRCA - Breast Cancer Genetic Testing
MedGenome/YouTube
1:37
Genetic Testing for Hereditary Forms of Kidney Cancer - Brian Shuch, MD
UCLA Health/YouTube
1:43
Do I need Genetic Testing for Ichthyosis?
foundation for ichthyosis/YouTube
2:01
What Is Genetic Testing? Understanding the Process and Its Results
uvahealth/YouTube
3:58
How to Understand Your Genetic Testing Results
Breast Cancer Answers®/YouTube
1:00:31
Genetic Testing 101 for People with Rare Diseases
National Organization for Rare Disorders (NORD)/YouTube
2:05
What's the difference between genetic and genomic testing?
Cancer Treatment Centers of America - CTCA/YouTube
Treatment
Low vision dosen't mean no vision---assisting low vision students in rural Nepal
Image by IAPB/VISION 2020
Low vision dosen't mean no vision---assisting low vision students in rural Nepal
Image by IAPB/VISION 2020
What's the Treatment for Bietti's Crystalline Dystrophy?
There is currently no proven treatment for BCD. Living with vision loss or low vision from BCD can be challenging. Having low vision means that even with glasses, contact lenses, medicine, or surgery, your vision loss makes it hard to do everyday tasks.
The good news is, there are things that can help — like low vision devices and rehabilitation (training) programs.
Source: National Eye Institute (NEI)
Additional Materials (1)
Low Vision
What is Low Vision Infographic. Information on low vision: causes, numbers, what we can do, and vision rehabilitation.
Image by NEHEP
Low Vision
NEHEP
Statistics
Illustration of rare disease incidence
Image by mcmurryjulie/Pixabay
Illustration of rare disease incidence
Image by mcmurryjulie/Pixabay
How Common Is Bietti Crystalline Dystrophy?
Bietti crystalline dystrophy has been estimated to occur in 1 in 67,000 people. It is more common in people of East Asian descent, especially those of Chinese and Japanese background. Researchers suggest that Bietti crystalline dystrophy may be underdiagnosed because its symptoms are similar to those of other eye disorders that progressively damage the retina.
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Bietti Crystalline Dystrophy
Bietti crystalline dystrophy (BCD) is an inherited eye disease that can lead to night blindness and other problems seeing. The disease is named for Dr. G. B. Bietti, an Italian ophthalmologist, who described three patients with similar symptoms in 1937. Read about causes, symptoms, and treatment for this rare disease.