Clinical Trials

What is a clinical trial?

Clinical trials are medical research studies in which people volunteer to participate. Carefully conducted clinical trials are the safest and fastest way to find treatments that work in people. A clinical trial is used to evaluate the safety and effectiveness of a new procedure, medication or device to prevent, diagnose or treat an eye disease or disorder. There are four different phases to a clinical trial. The time from a phase one to a phase four trial can take many years.

What are the different phases of a clinical trial?

Phase 1 Trial

These are the earliest trials in the life of a new drug or treatment. They are usually small trials, recruiting anything up to about 30 patients. Phase one trials are undertaken to determine the safety of a potential treatment. People recruited to phase one trials often have advanced eye disease. This work has to be completed first, as safety is the most important issue to resolve before wider testing of the potential new treatment.

Phase 2 Trial

This type of trial tests the potential new treatment in a larger number of volunteers to learn more about how the body responds to the treatment, the optimal dose of the treatment and how the treatment affects a certain eye condition. If the results of phase two trials show that a new treatment may be as good as existing treatment or better, they move to Phase three. Determining the safety of the drug is a large component of phase two testing and sometimes phase one and phase two trials are run at the same time.

Phase 3 Trial

Treatments only move into a phase three clinical trial if phases one and two suggest that a substance might actually be useful and safe in ways that patients would regard as important. Phase three trials are usually much larger than phase one or two, sometimes involving hundreds or thousands of patients in many different settings. Phase three trials are usually randomised. This means the researchers put the people taking part into two or more groups at random. One group gets the new treatment and the other the standard treatment or a placebo (non-active) treatment.

Phase 4 Trial

Phase four trials are performed after a drug has been shown to work and has been granted a license. They are performed in order to understand more about the treatment, by evaluating its safety and effectiveness in larger numbers of patients, subgroups of patients, and to compare and/or combine it with other available treatments. The time from a phase one to a phase four trial can take many years.

Are there clinical trials ongoing in Ireland?

There are a large number of clinical trials that are already at phase one and two stage worldwide for retinal degenerations, especially in the area of gene therapy. These trials are to determine the optimal dose that is safe to give to an individual. If these trials are successful, they may progress to phase three trials that will test the new therapy on larger numbers of people across many countries, which may include Ireland.

Every trial has a set of ‘entry criteria’ that you must meet in order to be a suitable participant. In the case of retinal degenerations, many therapies will rely on correcting the exact gene that is faulty and so one of the criteria for involvement in a trial will be knowing the gene responsible for your condition. This is why our Target 5000 project is so important. Target 5000 aims to identify the exact genetic profile of the estimated 5,000 people affected by a retinal degenerative condition in Ireland. If you have a condition such as retinitis pigmentosa (RP), Leber congenital amaurosis (LCA), Usher syndrome, Stargardt disease, Leber hereditary optic neuropathy (LHON) or others, you can get involved in Target 5000 by contacting the Fighting Blindness Research Manager on 01 6789 004 or

Target 5000 will facilitate he development of a national register of inherited retinopathies which is essential for the progress of genetics research and the enablement of clinical trials. This will also strengthens Ireland’s position as a potential location for clinical trials.

What happens if I agree to enter a trial but then change my mind?

You are free to leave a trial at any time without obligation to explain why.

How can I find out more information about clinical trials?

The Irish Platform for Patients, Science and Industry (IPPOSI) provide an excellent source of information about clinical trials on Clinical trials that are currently being conducted worldwide can be found on and can be searched by condition and trial location.

Clinical trials are extremely important; doctors, other healthcare professionals and patients need evidence from clinical trials to know which treatments work best. Some patients may benefit from participating in a clinical trial if the experimental drug turns out to be effective. However there are no guarantees that a study participant will receive any direct benefit from participation in a clinical trial.

By volunteering to participate in clinical trials, participants help advance what we know about medical interventions. In doing so, clinical trial participants can play an important role in the approval of new drugs and devices for treating other patients.