Congenital hereditary endothelial dystrophy type I is a rare genetic eye condition that causes cloudy corneas from birth or early infancy. People with congenital hereditary endothelial dystrophy type I often have very blurry vision and light sensitivity, and parents may notice hazy-looking eyes. It is lifelong, but vision can be stable or slowly change over time. Treatment focuses on improving vision with glasses, low-vision aids, and sometimes corneal transplant to clear the cornea. Most children with congenital hereditary endothelial dystrophy type I grow and live normal lifespans, and regular eye care helps protect vision.
Overview
Congenital hereditary endothelial dystrophy type iSymptoms
People with Congenital hereditary endothelial dystrophy type I often have cloudy corneas from early childhood, causing blurred vision. Light sensitivity and glare are common; eyes may water. Doctors see a diffuse blue‑gray corneal haze in both eyes.
Outlook and prognosis
Most people with congenital hereditary endothelial dystrophy type I have lifelong cloudy corneas that can affect vision from infancy. Vision often stabilizes after early childhood, but depth perception and clarity may remain limited. Regular eye care and, in some, corneal surgery improve day-to-day function.
Causes and risk factors
Congenital hereditary endothelial dystrophy type I stems from an inherited genetic change that affects the cornea’s inner cell layer, usually passed in an autosomal-dominant pattern. Risk is highest with an affected parent. There are no lifestyle or environmental causes.
Genetic influences
Genetics are central in congenital hereditary endothelial dystrophy type I, which is inherited, usually in an autosomal recessive pattern. Specific gene variants disrupt the corneal endothelium from birth. Family history guides risk, and genetic testing can confirm diagnosis and carrier status.
Diagnosis
Doctors suspect it from typical corneal changes on a detailed eye exam and family history. Diagnosis of congenital hereditary endothelial dystrophy type I is confirmed with corneal imaging and genetic tests.
Treatment and drugs
Treatment for congenital hereditary endothelial dystrophy type I focuses on clearing and protecting the cornea to improve vision and comfort. Care may include saline drops or ointments to reduce corneal swelling, protective eyewear, and regular monitoring. If clouding significantly affects sight, corneal transplantation can restore clarity.
Symptoms
Cloudy or hazy vision that slowly gets worse can make reading, schoolwork, or driving more challenging. In congenital hereditary endothelial dystrophy type i (often shortened to CHED type i), the clear front window of the eye (the cornea) holds extra fluid and loses some of its transparency. The way this shows up can differ from one person to another, and it may change with age. Early on, this might look like more glare, trouble with small print, or a faint gray tint to the eyes.
Things may look out of focus at distance or up close. You might find reading fine print or seeing faces across a room takes extra effort. Vision often changes slowly with CHED type i.
The clear surface of the eye can look gray or milky. Friends or family may notice that the eyes appear slightly bluish or hazy. This cloudiness comes from swelling in the cornea.
Bright light can feel harsh and uncomfortable. Sunshine, oncoming headlights, or glossy pages may scatter light and wash out detail. Sunglasses or hats may help ease the glare.
Rings or starbursts can appear around lights, especially at night. Streetlights and headlights may look smeared, which can make night driving harder. Taking extra time and avoiding night driving when possible can help.
How people usually first notice Congenital hereditary endothelial dystrophy type i?
Many families first notice something is off when a newborn’s eyes look unusually cloudy or bluish-gray, and the baby may seem sensitive to light or keep the eyes closed more than expected. During the first check-ups, doctors often see persistent corneal clouding in both eyes and reduced visual responses, which raises concern for a corneal problem rather than an infection. This is how the first signs of congenital hereditary endothelial dystrophy type I are typically recognized, leading to an early referral to an eye specialist for confirmation and care.
Types of Congenital hereditary endothelial dystrophy type i
Congenital hereditary endothelial dystrophy type I is a genetic/congenital eye condition, and clinicians recognize more than one clinical variant based on how the cornea looks, how early signs appear, and the underlying mutations. People may notice different sets of symptoms depending on their situation. These variants can overlap, but they often differ in age at diagnosis, severity of cloudy corneas, and how much vision is affected over time. Understanding the main variants of CHED type I can help people and families make sense of the types of Congenital hereditary endothelial dystrophy type I they may hear about in clinic.
Classic CHED1
Onset is usually in infancy or early childhood with diffuse corneal clouding and light sensitivity. Vision may be mildly to moderately reduced and can fluctuate with infections or irritation. Corneal thickness is often increased on exam.
Late‑onset CHED1
Symptoms emerge later in childhood or adolescence with gradual haze and glare. Vision changes tend to be slower and sometimes subtler at first. People may first notice trouble in low‑contrast or bright‑light settings.
Asymmetric CHED1
One eye shows more haze or earlier changes than the other. Depth perception issues or favoring one eye can appear in daily tasks. Over time, the second eye may show similar features but often remains milder.
What genetics can tell you about symptoms
People with congenital hereditary endothelial dystrophy type I often develop cloudy corneas, light sensitivity, and reduced vision from birth because mutations disrupt the corneal endothelium’s job of keeping the cornea clear and dehydrated. Different gene changes can shift severity, speeding or slowing haze and vision loss.
Causes and risk factors
The main cause is a gene change that disrupts the cornea’s inner lining from birth.
Most people inherit it from a parent in a dominant pattern, and some cases start as a new change.
This gene change is present before early symptoms of Congenital hereditary endothelial dystrophy type I appear.
Some risks are modifiable (things you can change), others are non-modifiable (things you can’t).
Family history is the key risk, while eye injuries, infections, or ongoing irritation may worsen clouding but do not cause the disease.
Environmental and biological risk factors
Understanding what might raise or lower the chance of congenital hereditary endothelial dystrophy type i can help you know what to watch for and when to ask questions about early symptoms of congenital hereditary endothelial dystrophy type i. Doctors often group risks into internal (biological) and external (environmental). For this condition, most influences are present before birth, and outside exposures have not been shown to play a strong role. Below are the environmental and biological factors researchers have looked at so far.
Research has not found consistent links between common pregnancy exposures and congenital hereditary endothelial dystrophy type i. Avoiding high-dose radiation, lead, and mercury remains important for overall fetal health.
Infections such as rubella or toxoplasmosis can affect fetal eyes, but a direct connection to congenital hereditary endothelial dystrophy type i has not been shown. Routine prenatal care helps lower infection-related risks in general.
Conditions like uncontrolled diabetes or thyroid disease can influence fetal development overall, yet they have not been tied specifically to congenital hereditary endothelial dystrophy type i. Good control of these conditions supports healthier pregnancies.
Some birth conditions are more frequent with older parents, but there is no clear evidence that parental age changes the chance of congenital hereditary endothelial dystrophy type i. Reported cases occur across a wide range of parent ages.
Genetic risk factors
Congenital hereditary endothelial dystrophy type i is most often passed down in an autosomal dominant pattern, where a single gene change can be enough. The exact genetic causes of Congenital hereditary endothelial dystrophy type i are still being clarified, and different families may have different underlying changes. Risk is not destiny—it varies widely between individuals. Genetic testing can sometimes help but may be inconclusive if the responsible gene in a family has not yet been identified.
Autosomal dominant: A change in one copy of a relevant gene can lead to the condition. Each child of an affected parent has a 50% chance of inheriting the altered gene.
Family history: Having a parent or siblings with Congenital hereditary endothelial dystrophy type i increases personal risk. Patterns seen across generations help confirm inheritance.
De novo variants: Sometimes a new genetic change arises for the first time in a child. In those cases, parents may not carry the change even though the child is affected.
Variable expressivity: The same genetic change can cause different levels of corneal involvement among relatives. This means severity and age at recognition can vary within a family.
Incomplete penetrance: Some relatives may carry the genetic change but show few or no clear features. Family history can look like it “skips” a generation because of this.
Genetic heterogeneity: Similar clinical findings can result from changes in different genes. In some families with Congenital hereditary endothelial dystrophy type i, the exact gene has not yet been identified. This uncertainty can affect the chance of finding a causative variant on testing.
Testing limits: Multi-gene panels may not include every possible gene or detect all variant types for CHED type i. A negative result does not rule out a hereditary cause if the family pattern fits. Even so, genetic testing for Congenital hereditary endothelial dystrophy type i can help clarify risks for relatives and future pregnancies.
Related dystrophies: Some families show overlap with other dominantly inherited corneal endothelial dystrophies that share similar features. Clarifying the exact diagnosis helps guide which genes are most relevant to test.
Lifestyle risk factors
Congenital hereditary endothelial dystrophy type I is genetic; lifestyle habits do not cause it. However, daily choices can influence symptoms like haze, photophobia, and infection risk, and can affect recovery after treatments. Understanding how lifestyle affects congenital hereditary endothelial dystrophy type i can help reduce flares and protect vision.
Wear UV-blocking wraparound sunglasses to cut glare and photophobia from a hazy cornea. Use protective goggles during sports to prevent injuries that can worsen corneal swelling or scarring.
If you use scleral or soft lenses, follow meticulous cleaning and avoid sleeping in lenses. This lowers hypoxia and infection risk that can aggravate corneal edema in CHED1.
Rubbing creates microtrauma that can increase corneal swelling and discomfort. Manage itch with lubricating drops or cool compresses instead of rubbing.
Smoke, chlorine, and dusty air can inflame the ocular surface and intensify glare. Limiting exposure may reduce tearing and light sensitivity in CHED1.
Risk prevention
Congenital hereditary endothelial dystrophy type I is present from birth and affects the clear front window of the eye, which can blur vision over time. You can’t prevent the condition itself, but you can lower the chance of vision loss by spotting problems early and protecting the eyes day to day. Because early symptoms of congenital hereditary endothelial dystrophy type I can be subtle, regular check‑ins with an eye specialist matter. Prevention is about lowering risk, not eliminating it completely.
Schedule newborn, infant, and childhood eye checks with a pediatric ophthalmologist. Early monitoring helps catch clouding and vision changes before they cause lasting problems.
If surgery or other treatments are recommended, doing them at the right time can protect vision development. This may help prevent amblyopia (lazy eye) in young children.
Follow patching or vision therapy plans exactly as prescribed. Consistent practice helps both eyes learn to work and see as well as possible.
Use wide‑brim hats and UV‑blocking sunglasses to reduce glare and light sensitivity. Protecting from bright light can make daily activities more comfortable and may reduce eye rubbing.
Transmission
Congenital hereditary endothelial dystrophy type i is not contagious; it doesn’t spread through contact, droplets, pregnancy, or breastfeeding. In type I, a single altered copy of a gene from an affected parent can cause the condition, so each child has a 50% chance of inheriting it. Rarely, Congenital hereditary endothelial dystrophy type i can appear for the first time in a family because of a new gene change. If you’re wondering about how Congenital hereditary endothelial dystrophy type i is inherited, a genetics professional can explain family risks and discuss testing options.
When to test your genes
Consider genetic testing if you or a close relative have early-onset cloudy corneas, repeated corneal swelling, or a diagnosis of congenital hereditary endothelial dystrophy type I. Testing helps confirm the subtype, guide monitoring and timing of corneal care, and inform family planning. If you’re unsure, start with an eye specialist or genetic counselor.
Diagnosis
Blurred or hazy vision from infancy or early childhood can make it hard for kids to see the board at school or track a ball during play. For many, the first step comes when everyday activities start feeling harder. With congenital hereditary endothelial dystrophy type i, eye specialists usually recognize the corneal clouding and then use a few focused tests to confirm what’s causing it. The diagnosis of congenital hereditary endothelial dystrophy type i typically combines what the doctor sees during the exam with imaging and, in some cases, genetic tests.
Doctors examine the front of the eye for diffuse corneal clouding and a bluish-gray haze. These clinical features help distinguish this condition from infections or scarring.
A quick, painless measurement checks if the cornea is thicker than expected. Increased thickness supports the diagnosis by showing swelling from endothelial dysfunction.
This imaging estimates the number and shape of corneal endothelial cells. Abnormal or reduced cells point toward an endothelial dystrophy rather than a surface problem.
Cross‑sectional imaging shows corneal layers and edema in detail. Clear layer changes strengthen the clinical impression and help track severity over time.
Stages of Congenital hereditary endothelial dystrophy type i
Congenital hereditary endothelial dystrophy type i does not have defined progression stages. It tends to show up early in life and is usually described by how cloudy the cornea looks and how vision is affected, rather than by stepwise stages. Doctors usually make the diagnosis based on an eye exam and history; early symptoms of Congenital hereditary endothelial dystrophy type i may include light sensitivity, tearing, or eyes that look hazy or bluish-gray. Different tests may be suggested to help confirm the diagnosis and guide follow-up, such as corneal imaging and, in some cases, genetic testing.
Outlook and prognosis
Living with congenital hereditary endothelial dystrophy type I (CHED type I) often means managing cloudy vision from infancy or early childhood and the day-to-day effects that come with reduced clarity—glare sensitivity on bright days, trouble spotting faces across a room, or a child holding books very close. Many people ask, “What does this mean for my future?”, and the short answer is that vision can remain stable or slowly worsen over time, depending on how much the cornea swells and scars. Doctors call this the prognosis—a medical word for likely outcomes. For many, corneal clarity does not improve on its own; glasses or contact lenses may help some tasks, but they typically cannot reverse the underlying haze.
In terms of long-term vision, some children with CHED type I maintain functional sight for school and work, while others develop deeper clouding that interferes with reading, driving, or night vision. Early care can make a real difference, especially when eye pressure is monitored and treated if it rises, because secondary glaucoma can further reduce vision. If the cornea becomes too opaque, corneal transplant is the main option to restore transparency; success rates are generally good in expert centers, though graft rejection, infection, and need for repeat surgery remain possible. Understanding the prognosis can guide planning and expectations around milestones like school accommodations, driving evaluations, and timing of surgery.
CHED type I does not affect life expectancy, and mortality from the condition itself is not expected. That said, timely treatment of complications helps protect the best possible vision. Ask about early symptoms of CHED type I that may signal changes—more light sensitivity, worsening blur, or eye discomfort—and what steps to take if they appear. Talk with your doctor about what your personal outlook might look like, including whether genetic results or family history offer clues about how your vision may change over time.
Long-term effects
Living with hazy or fluctuating vision over years can affect reading, driving at dusk, or schoolwork. Some families first notice what feel like early symptoms of congenital hereditary endothelial dystrophy type I, such as morning haze that eases a bit later in the day. Long-term effects vary widely, and vision changes may progress slowly in many while staying relatively steady in others. If clouding becomes significant, corneal transplantation can improve clarity for many people with this condition.
Corneal swelling leads to gradual haze and reduced sharpness. In congenital hereditary endothelial dystrophy type I, this often worsens over years rather than weeks.
Vision may be blurrier in the morning and clear a bit later in the day. In this condition, that day-to-day swing can make reading or screen use inconsistent.
Glare and halos can be bothersome in bright sunlight or at night. This can limit night driving and make classroom or office lighting uncomfortable.
In children with congenital hereditary endothelial dystrophy type I, ongoing blur can affect visual development and school performance. Amblyopia or eye drifting is less common than in the recessive form but can occur if clarity is very poor.
How is it to live with Congenital hereditary endothelial dystrophy type i?
Living with congenital hereditary endothelial dystrophy type I often means navigating cloudy or hazy vision from early life, with brightness and glare making everyday tasks—reading signs, judging steps, or recognizing faces—more tiring than expected. Many find that consistent eye care, protective eyewear, and good lighting help, but school, work, and driving may require accommodations and regular follow-up with an eye specialist. Families, teachers, and coworkers often play a key role by offering practical support—like seating near the front, larger print, or flexible task timing—and by understanding that vision may fluctuate day to day. With planning and the right tools, people can stay active, learn effectively, and participate fully, even if some activities need adaptation.
Treatment and drugs
Treatment for congenital hereditary endothelial dystrophy type I focuses on improving vision, keeping the cornea clear, and preventing complications like eye irritation or infections. Lubricating eye drops or ointments can ease discomfort from dryness or surface irritation, and hypertonic saline drops may help draw out excess fluid to slightly reduce corneal swelling. Glasses or contact lenses can optimize vision, but when clouding is severe or vision remains poor, corneal transplant (keratoplasty) is often the main option to restore clarity. Your doctor may suggest protective steps—like treating amblyopia in children, managing light sensitivity, and monitoring for glaucoma—because early symptoms of congenital hereditary endothelial dystrophy type I can affect visual development. Not every treatment works the same way for every person, so eye specialists typically tailor the plan to age, vision needs, and how cloudy the cornea is.
Non-drug treatment
Non-drug care for congenital hereditary endothelial dystrophy type i (CHED type I) focuses on protecting vision, easing light sensitivity, and supporting development, especially in childhood. Non-drug treatments often lay the foundation for day-to-day functioning while families and clinicians consider timing for surgical options, if needed. Early symptoms of congenital hereditary endothelial dystrophy type i—like cloudy corneas or light aversion—can guide which supports to start first. Plans are tailored by age and vision needs, with regular follow-up to adjust as life changes.
Scheduled visits track corneal clarity, eye pressure, and vision changes. This helps time other treatments—like surgery—if and when they’re needed.
For children, patching the stronger eye or using vision exercises helps the brain develop clearer sight in the affected eye(s). Starting early gives the best chance to prevent “lazy eye.”
Impact-resistant glasses and UV-blocking sunglasses reduce glare and protect the eyes from injury. A wide-brim hat can further cut light sensitivity outdoors.
Light-filtering lenses can ease glare and photophobia from a hazy cornea in CHED type I. A low-contrast environment at home or school may also help comfort and function.
Your genes may have an impact on how drugs work for you
Genes can change how your body processes certain eye medicines, which may alter how well drops work or how you handle anesthesia during corneal procedures. Testing isn’t routine, but sharing family history helps your team tailor treatments and monitor responses closely.
Pharmacological treatments
Medicines for congenital hereditary endothelial dystrophy type I mainly aim to pull fluid out of the cornea to lessen haze and improve comfort. These options can ease day-to-day blur and light sensitivity, but they don’t reverse the underlying endothelial problem. Alongside drug therapy, corneal procedures and vision supports remain important. These medicines can ease early symptoms of congenital hereditary endothelial dystrophy type I like glare, tearing, and foggy vision, but many people eventually need surgery for clearer sight.
Sodium chloride 5% eye drops or ointment draw excess water out of the cornea to reduce swelling. Drops are typically used several times daily, with ointment at bedtime to help morning blur. Mild stinging can occur but usually settles.
Preservative‑free artificial tears, gels, or nighttime ointments improve surface moisture and comfort. They can lessen burning and gritty sensation that often comes with corneal edema in CHED type I. Use as needed during the day.
Netarsudil or ripasudil (off‑label) may help corneal endothelial function and reduce edema in some cases. Evidence in congenital hereditary endothelial dystrophy type I is limited, so doctors often try this only when standard measures fall short. Redness or mild irritation can occur.
Glycerin eye drops can give temporary clearing by dehydrating the cornea. They are usually used short‑term, sometimes in clinic before an exam or procedure. Blurring or stinging may follow for a few minutes.
Genetic influences
In many families, congenital hereditary endothelial dystrophy type I tends to appear across generations, pointing to a strong genetic role. Family history is one of the strongest clues to a genetic influence. Most often, the condition is passed on when an affected parent has one changed copy of a gene; this is known medically as autosomal dominant inheritance.
With this pattern, each child of an affected parent has a 1 in 2 (50%) chance of inheriting the condition. Symptoms and severity can differ between relatives, and in rare cases the gene change can arise for the first time in a child, so parents may not always have noticeable signs. People often ask whether congenital hereditary endothelial dystrophy type I is inherited; meeting with a genetic counselor and, when appropriate, doing genetic testing can clarify family risks and help with planning.
Is Congenital hereditary endothelial dystrophy type i genetic?
Genetics are central in congenital hereditary endothelial dystrophy type I, which is inherited, usually in an autosomal recessive pattern. Specific gene variants disrupt the corneal endothelium from birth. Family history guides risk, and genetic testing can confirm diagnosis and carrier status.
Pharmacogenetics—how genetics influence drug effects
In Congenital hereditary endothelial dystrophy type i, treatment usually centers on corneal surgery and supportive eye drops, so genetics rarely points to a single “right” eye medicine. That said, your genes can influence medicines used around surgery or in special circumstances. Not every difference in response is genetic, but pharmacogenetic testing for Congenital hereditary endothelial dystrophy type i may help guide dosing or drug choice if certain systemic medicines are needed. For example, if systemic immunosuppression such as tacrolimus is prescribed for a high‑risk corneal graft, common differences in a liver enzyme gene (CYP3A5) can change how quickly you clear the drug, so doctors often adjust the dose using genetics and blood levels. For pain control, opioids like codeine or tramadol rely on another enzyme (CYP2D6); people who convert these too quickly or too slowly may have more side effects or poor pain relief, so non‑opioid options are often preferred, especially in children. During anesthesia for transplant, a rare inherited enzyme issue can make a muscle relaxant such as succinylcholine last much longer, so sharing any family history of prolonged paralysis helps the team plan safely. After surgery, steroid eye drops can raise eye pressure in “steroid responders,” which tends to run in families, so close pressure checks and a tailored taper are important.
Interactions with other conditions
People with Congenital hereditary endothelial dystrophy type I often feel its impact mainly in the eyes, but it can interact with other conditions that affect vision and hearing. The most notable link is progressive sensorineural hearing loss; when both occur together, the combination is sometimes called Harboyan syndrome, so periodic hearing checks from childhood onward are wise. Some families also report relatives with later-onset corneal problems like Fuchs endothelial dystrophy; shared genetic variants may explain why certain conditions cluster together. In early life, persistent corneal clouding from CHED type I raises the risk of amblyopia (lazy eye) and nystagmus, making close coordination with pediatric eye specialists important to protect visual development. Because early symptoms of Congenital hereditary endothelial dystrophy type I can mimic congenital glaucoma, and the two can occasionally occur together, high eye pressure may further worsen corneal swelling and blur, so careful pressure monitoring matters. Before starting or changing treatment, let your care team know about any other eye or ear diagnoses so they can tailor choices and avoid adding stress to the corneal lining.
How genes can cause diseases
Humans have more than 20,000 genes, each carrying out one or a few specific functions in the body. One gene instructs the body to digest lactose from milk, another tells the body how to build strong bones and another prevents the body's cells from beginning to multiply uncontrollably and developing into cancer. As all of these genes combined are the building instructions for our body, a defect in one of these genes can have severe health consequences.
Through decades of genetic research, we know the genetic code of any healthy/functional human gene. We have also identified that in certain positions on a gene, some individuals may have a different genetic letter from the one you have. We call these hotspots "Genetic Variations" or "Variants" in short. In many cases, studies have been able to show that having the genetic letter "G" in the position makes you healthy, but having the letter "A" in the same position disrupts the gene function and causes a disease. Genopedia allows you to view these variants in genes and summarizes all that we know from scientific research, which genetic letters (Genotype) have good or bad consequences on your health or on your traits.
History
Throughout history, people have described babies whose eyes looked hazy or “milky” from the start, with light sensitivity and trouble fixing their gaze. Families sometimes remembered that a parent or grandparent had similar cloudy corneas since infancy. These everyday observations match what doctors now recognize as congenital hereditary endothelial dystrophy type I, a rare condition present from birth that mainly affects the clear front window of the eye.
First described in the medical literature as a form of early corneal clouding that seemed to run in families, it was initially grouped with other childhood corneal disorders. Early case reports focused on what could be seen: bluish‑gray corneas, tearing, and nystagmus (shaky eyes), with vision that ranged from mildly blurred to severely reduced. Over time, descriptions became more precise as specialists compared many families and noticed that this form tended to appear right at birth and to follow a dominant inheritance pattern—meaning it could pass from an affected parent to a child—separating it from look‑alike conditions that begin later or follow different inheritance patterns.
From early theories to modern research, the story of congenital hereditary endothelial dystrophy type I has been one of sorting out similar‑sounding diagnoses. For years, reports blended together cases that started in infancy with others that began in early childhood. This made it hard to predict outcomes or offer clear guidance. As medical science evolved, careful family histories, detailed eye exams, and later imaging of the cornea helped draw a sharper line between type I and other endothelial dystrophies.
Advances in genetics added another layer. Researchers studying generations with the same pattern of early corneal clouding used family trees to confirm the inherited nature of the condition and to distinguish it from recessive forms that appear when both parents carry a nonworking gene. While genetic testing is still improving and not every family will have an identifiable change on current panels, DNA research now explains why some families show consistent, birth‑onset corneal clouding across multiple generations.
In recent decades, awareness has grown alongside better newborn eye screening and referral to pediatric eye specialists. This has shifted the typical pathway from late recognition—when a child struggles to see letters on a chart—to early diagnosis in infancy, when supportive care and monitoring can begin. Understanding past confusion between similar conditions helps explain why you may see different names in older records, but today’s definitions more clearly place congenital hereditary endothelial dystrophy type I as a birth‑present, dominantly inherited corneal dystrophy with variable impact on vision.