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Oral Metformin for Treatment of ABCA4 Retinopathy (Stargardt Disease)


ABCA4 Retinopathy or Stargardt disease is rare genetic disorder that affects the retina — the tissue at the back of the eye that senses light. Stargardt is caused by mutations in a gene called ABCA4. This gene makes a protein that clears byproducts of vitamin A from inside photoreceptors. Photoreceptors are cells within the retina that detect the light and convert it to electrical signals that the brain decodes into “vision”. 

This disease causes vision loss mostly during childhood or adolescence. People don’t usually go completely blind, but vision loss progresses over time. Most of the vision loss in the central area of the retina, which is responsible for sharp, straight-ahead vision. 

Currently, there is no cure for Stargardt disease.


The objective of this study is to investigate the safety and potential efficacy of oral metformin in slowing the rate of change in photoreceptor degeneration in ABCA4 retinopathy (Stargardt disease).

Who is eligible to participate?

The National Eye Institute is looking for 44 participants to take metformin, a common drug used to control diabetes, during 24 months. The main eligibility criteria are: 

  • Age group: 12 years of age or older;
  • At least one definite mutation in ABCA4 and a typical clinical presentation of Stargardt disease (loss of central vision, for example);
  • Participants must have been diagnosed with Stargardt for at least two years with loss of vision of 0.025 mm/year. 

Participants of other clinical trials, those with health conditions that increase their risk of illness if taking metformin, including but not limited to uncontrolled diabetes, chronic liver or kidney disease, unstable high blood pressure or glycemic control, are not eligible to participate in the study.

Frequently Asked Questions

1. Why is this study being done? 
This is a research study. The purpose of this research study is to see if metformin is safe and possibly helps to slow the rate of Stargardt disease.

2. What is metformin? 
Metformin is a drug approved by the U.S. Food and Drug Administration (FDA) for the treatment of Type 2 diabetes. The use of metformin in this study is considered investigational, which means it has not been approved by the FDA to treat Stargardt. However, the FDA has given the National Eye Institute (NEI) permission to use metformin in this study. 

3. What will happen during the study? 
Participants will be asked to take metformin for 24 months and complete visits at the NIH Clinical Center for at least 36 months.

Participants will be seen by an eye doctor. They will take several tests to assess their vision and we will take pictures of the back of their eyes. These are all tests typically taken when visiting an eye doctor. 

4. If I already take metformin, can I participate? 
You should not be in the study if you are already taking metformin or have a known allergy to metformin.

5. Can I enroll my child in the study if she/he is younger than 12 years of age?
This clinical trial only allows participants 12 years of age or older.

6. Can my physician refer me to the study?
Yes, physicians can refer their patients to the clinical trial if they meet the eligibility criteria. They can contact Allison Bamji at

7. Is my vision going to improve with this procedure?
This is a safety and efficacy clinical trial that will investigate whether metformin can slow the progress of photoreceptor degeneration in ABCA4 retinopathy. The drug used in this clinical trial is not expected to revert existing vision loss. 


Below is information you might find useful when trying to determine whether you are eligible and willing to enroll in this clinical trial. For questions or detailed materials, please contact:  Allison Bamji, R.N., 301-451-3437;

Information about Stargardt disease 

Information about NEI Clinical Trials

Information about NEI’s Eye Clinic 

Information about other clinical trials

Last updated: September 29, 2021