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The Eye Clinic: Learn about clinical trials

How a Clinical Trial is Conducted

The researcher in charge of a clinical trial is called the principal investigator. The person who makes the arrangements for your visits and explains how the study works is called the clinic coordinator.

Volunteers for clinical trials must meet certain eligibility criteria, which may involve age, type, and stage of a particular eye condition, and previous treatment for the condition.

If you are eligible for a clinical trial and you agree to participate, you will be asked to sign an informed consent. This document explains the main purpose of the study, the eligibility criteria, the treatment, the possible risks and benefits, your rights as a patient, and what researchers expect from you. All of the doctors involved in the study follow a detailed treatment plan known as the study protocol. The protocol ensures that all participants are treated in a standard way.

Clinical trials are controlled, meaning that researchers compare the effects of a new treatment with those of another treatment. This is done by dividing study participants into groups. If you receive the new treatment, you are in the treatment group. If you are in the control group, you could receive the standard treatment for a particular eye condition. When a standard treatment does not exist, you may receive no treatment, a placebo, or a sham treatment.

A placebo may be used in clinical trials that test a medication. It is a harmless substance that looks like the real medication but has no direct effect on an eye condition. A sham treatment may be used in clinical trials that test a new surgery or device. A sham treatment, like a placebo, is safe and has no direct effect on an eye condition. Placebos and sham treatments are often used to understand both the positive and negative effects of a new treatment.

Researchers randomly assign participants to the treatment and control groups. In most studies, you have an equal chance of being assigned to each of the study groups. Though the study treatment may be effective in some cases, new treatments may have serious side effects or may not be effective. During the clinical trial, there is no way for you or your doctor to know which study group will have the best response to treatment.

In a nonmasked trial, both you and your doctor will know your group assignment. In a masked trial, you will not know your group assignment. In a double masked trial, neither you nor your doctor will know your group assignment. Double masked trials help to ensure that the results will not be affected by what you or your doctor might think about the treatment.

How are clinical trials in vision different from other clinical trials?

Eyes are one of many body parts that come in pairs. This feature gives researchers some additional options when they design the study. If an eye condition affects both of your eyes, one eye might be placed in the treatment group for a study and the other may be in the control group. Generally, the eye that will be treated is randomly assigned.

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Department of Health and Human Services NIH, the National Institutes of Health USA.gov