Cystinosis affects all the body’s organs, and can severely impact vision, if not properly managed.
Whether you, your child or a loved one have been diagnosed with cystinosis, understanding how cystinosis affects the eye is important for patients to manage their condition.
This website provides helpful information about ocular health that you can discuss with your eye care specialist and healthcare team.
Cystinosis is a genetic disease that occurs when a person inherits a CTNS gene with a specific mutation from each parent. To inherit cystinosis, both parents must have the mutated CTNS gene.
A properly working CTNS gene produces a ‘transporter’ that specifically removes cystine from inside the cell. In people with cystinosis, the transporter doesn’t work properly because of the gene mutation, so the cystine gets trapped inside the cells and builds up, forming crystals.
Typically, the crystal buildup primarily affects the kidneys and the eyes, making them vulnerable to damage. Unfortunately, damage to the eye caused by this buildup cannot be reversed. However, with appropriate medical intervention, the accumulation of crystals can be effectively managed.
Crystal buildup affects all parts of the eyes, specifically the cornea. This accumulation can lead to a condition called corneal cystine crystal accumulation. It can cause sensitivity to light – known as photophobia – as well as blurry vision, corneal erosions, and, in severe cases, vision loss.
The most common gland affected by cystinosis is the thyroid gland, leading to hypothyroidism. Other endocrine-related complications may include growth hormone deficiency, and diabetes.
In some cases, cystinosis can affect muscle tissues, leading to muscle weakness and impaired muscle function, which may result in reduced muscle strength.
Cystinosis can lead to liver enlargement (hepatomegaly) and dysfunction. It can also cause damage to the pancreas, leading to impaired pancreatic function.
Deposits of cystine crystals in kidney cells cause damage to the kidney tubules, which can lead to electrolyte imbalances, and the progression of chronic kidney disease (CKD) over time.
Cystinosis is a multi-system condition that impacts the kidneys, endocrine system, muscles, liver, pancreas, and yes, the eyes.
To learn more about the impacts of cystinosis, click on an affected body part.
Cystinosis is a multi-system condition that can impact the kidneys, endocrine system, muscles, liver, pancreas, and yes, the eyes.
To learn more about the impacts of cystinosis, swipe below.
The symptom most patients notice first is photophobia, a sensitivity to light that causes discomfort. Photophobia may begin by age 3 or even earlier. An early sign is occasional eye blinking in light. As more crystals build up, eye blinking in light becomes more frequent. Eventually, dark glasses may be needed outside most or all the time and possibly even inside.
Over time, as more crystals build up in the cornea, other symptoms and complications may occur, including:
While crystals in the cornea start to accumulate in infancy, patients can be asymptomatic for some time, meaning that even though the eyes are experiencing crystal buildup, they aren’t yet showing symptoms of the condition.
All parts of the eye can be affected by cystinosis. The cornea – the front, clear part of the eye – may be impacted the most. A healthy cornea is very important because it:
Corneal nerves are responsible for the sensations of touch, pain, and temperature; they also play an important role in the blink reflex, wound healing, tear production and secretion. Damage to the layers of the cornea affect corneal nerves, and can result in severe eye pain.
In people with cystinosis, cystine crystals build up in the layers of the cornea. At first, cystine crystals mainly start building up along the outer edges of the front layers of the cornea. Over time, cystine crystal buildup continues, progressing into the center of the corneal layers and into the back layers of the cornea. Eventually, all layers of the cornea become packed with crystals.
The accumulation of these cystine crystals interferes with the normal functioning of corneal cells and tissues; this eventually could lead to serious irreversible damage to corneal cells and results in harmful effects which can include:
Corneal Deposits: Crystal deposits can result in a cloudy or hazy appearance of the cornea, affecting its transparency and causing serious irreversible damage to the cornea cells.
Corneal Sensitivity: The presence of cystine crystals in the cornea can cause increased sensitivity to light (photophobia) and discomfort. The reason for this is because the crystals are irritating the corneal surface and sensory nerve endings, leading to pain, burning, and a gritty feeling in the eye.
Corneal Erosions: Cystine crystals can cause damage to the outermost layer of the cornea. This damage can result in corneal erosion which can cause episodes of eye pain, redness, tearing, and inflammation.
Visual Impairment: As the cystine crystals accumulate and affect corneal transparency, the ability to see clearly becomes difficult. The cloudy appearance of the cornea can lead to blurred or distorted vision. In severe cases, vision loss can be significant and impact daily activity.
Without intervention, cystine crystals will continue to build up in the cornea.
Keeping track of the amount or density of crystals in the cornea is a good way for eye care specialists to see changes over time. The buildup of corneal crystals can lead to uncomfortable and painful symptoms, as well as difficulty with daily activities.
Eye care specialists typically use a slit lamp to take photos of the crystals in the cornea. They may use a scale from 0 (no crystals) to 3 (packed with crystals) or verbal descriptors to describe crystal density and depth of crystal accumulation.
Crystal density across layers of the cornea:
It’s a good idea to document crystal density after every slit lamp exam with the doctor.
This information allows doctors to modify a treatment plan based on current presentation.
Every six months or so, consider documenting the level of discomfort in sunlight or bright light, from “no discomfort or difficulty” to “extreme difficulty with light that requires staying inside.”
Additional symptoms to track include:
People with cystinosis deal with ocular symptoms from an early age, through the adolescent and teen years, all the way to adulthood. It’s important to manage corneal cystine crystal accumulation throughout your whole life.
Since healthy eyesight is a critical part of daily life, it’s a good idea to document and share ocular symptoms with your eye care specialist so symptoms can be monitored as they change over time. By establishing a baseline for each eye symptom, and then capturing gradual fluctuations, the doctor is able to evaluate the status of crystal buildup, so action can be taken to modify treatment plans to meet changing needs.
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