Iron is a necessary mineral for many of the body’s functions, including vision. But too much iron – or problems with utilizing, storing, or transporting iron properly – can lead to vision loss in the form of conditions such as age-related macular degeneration and hyperferritinemia syndrome, according to recent research findings.
Age-related macular degeneration (AMD) is regarded as the leading cause of vision loss for people over the age of 50. The macula, a small portion of the retina which is responsible for sharp and detailed vision, deteriorates over time when the retinal pigment epithelium (RPE) surrounding the macula oxidizes – triggering an inflammatory response.
While smoking, poor diet, and lack of exercise typically contribute to oxidation of the retina, research has found that iron may also increase a person’s risk of AMD, according to Dr. Joshua Dunaief, professor of ophthalmology at the University of Pennsylvania School of Medicine.
“Iron accumulates in the body with age because we continue to absorb it from our diets, but we excrete very little,” Dunaief said. “Iron may accumulate to even higher levels in diseased retinas because low oxygen levels (hypoxia) or inflammation can cause cells to retain iron.”
Normally the RPE has ways to prevent iron from entering the retina when iron levels are high, but if iron export from cells is unregulated, iron may accumulate in the eye and degrade the macula. Dunaief’s research has shown that the oral iron chelator deferiprone may be a possible treatment for AMD if iron accumulation was one of the causes for its development. Iron chelation therapy is the removal of excess iron from the body with special drugs.
“Deferiprone can protect the retinas of mice by entering the retina and removing iron from it,” said Dunaief, whose lab is currently testing additional drugs to prevent iron accumulation in the eye.
Oftentimes the storage protein for iron, ferritin, can reach the eye instead of the mineral itself. The result is hereditary hyperferritinemia cataract syndrome (HHCS), an inherited condition of early-onset cataracts which could be dangerously confused with hemochromatosis (iron overload) unless a person is diagnosed using the full iron panel:
- Hemoglobin: the iron-containing protein in the blood that carries iron and oxygen to cells; this test measures how well the body is using iron
- Transferrin-iron saturation percentage (TS%): a measure of iron carried by the protein transferrin in the serum; represented by fasting serum iron divided by total iron binding capacity (TIBC), multiplied by 100%
- Serum ferritin: indicates the amount of iron stored in the body, via the protein ferritin
People with HHCS typically have normal TIBC and TS% test results but elevated serum ferritin levels (Hyperferritinemia means high ferritin in the blood). A liver biopsy will show that the patient does not have iron overload. An ophthalmologist confirms diagnosis of HHCS.
But how can the body’s storage sites for iron be full without iron overflowing into other organs? The answer is that a genetic mutation has turned off the body’s ability to make ferritin in response to changing iron levels. This means that ferritin is constantly being made no matter whether iron levels are high or low. In HHCS, components of ferritin accumulate in the eye lens and crystalize – disrupting the light transmission which enables a person to see.
If an HHCS patient is falsely diagnosed with hemochromatosis, phlebotomies used to remove excess iron from the body could make the person become iron deficient. Right now, the only known treatment for HHCS is cataract surgery.