Researchers of a new study found that the extent of retina swelling in patients with retinitis pigmentosa (RP) can be reduced by the consumption of iodine.

Patients with retinitis pigmentosa (RP) often experience a condition known as cystoid macular edema (CME), which is the swelling of the retina. This condition can lead to loss of night and side vision along with impaired central vision.

A new study by researchers from the Massachusetts Eye and Ear, Harvard Medical School, and Boston University School of Medicine found that the consumption of iodine can reduce retinal swelling by a significant amount.

The study was conducted on 212 non-smoking patients, aged between 18 and 69 years. The researchers used optical coherence tomography to measure central foveal swelling due to CME in the patients. Researchers also measured total dietary iodine consumption through spot urine samples.

Researchers found that patients with the lowest urinary iodine levels had retinas with the most swelling.

"Additional study is required to determine whether an iodine supplement can limit or reduce the extent of CME in patients with RP," said lead author Michael A. Sandberg in a press statement.

The Institute of Medicine has set the Recommended Dietary Allowance (RDA) for iodine in adult men and women at 150 μg per day. Individuals who add tablet salt to their food regularly should use iodized salt. One teaspoon of iodized salt contains approximately 400 μg iodine. Most iodine-containing multivitamins have at least 150 μg iodine, but only about half of the types of multivitamins in the U.S. contain iodine.

There are no tests to confirm if you have enough iodine in your body. When iodine deficiency is seen in an entire population, it is best managed by ensuring that common foods that people eat contain sufficient levels of iodine

Iodine deficiency is associated with goiter and hypothyroidism. When severe iodine deficiency occurs during pregnancy, it is associated with cretinism and increased neonatal and infant mortality. In addition, mild iodine deficiency is associated with thyroid enlargement and learning disabilities in children. Additional factors that can exacerbate the effects of iodine deficiency include coexistent deficiencies of iron, selenium, and vitamin A, and the ingestion of foods such as cassava or millet that contain goitrogenic substances, according to the Centers For Disease Control and Prevention.

Findings of the study were published online in the July issue of JAMA Ophthalmology. The project was funded by the National Eye Institute, Massachusetts Lions Eye Research Fund, Inc and the Foundation Fighting Blindness.