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Optometry and Vision Science Research Guide: Studies: Clinical trials, randomized and controlled

Research resources and information for vision science.
  Evidence-based research and practiceStudies: Clinical trials, interventional and observational

Clinical Trials and Research Registries

Clinical trial registries

Further reading

Active, recruiting and recently completed trials for the School of Optometry and Vision Science


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Clinical Trials at the University of Waterloo

Types of clinical studies

An interventional trial is a type of clinical study in which participants are assigned to groups that receive one or more intervention/treatment (or no intervention) so that researchers can evaluate the effects of the interventions on biomedical or health-related outcomes. The assignments are determined by the study's protocol. Participants may receive diagnostic, therapeutic, or other types of interventions.

A protocol is the written description of a clinical study. It includes the study's objectives, design, and methods. It may also include relevant scientific background and statistical information.

An intervention or treatment is a process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.1

In observational clinical studies, participants are identified as belonging to study groups and are assessed for biomedical or health outcomes. Participants may receive diagnostic, therapeutic, or other types of interventions, but the investigator does not assign participants to a specific interventions/treatment. A patient registry is a type of observational study. 1

Research Databases


1 How to read a study record. Published 2017 Dec. Accessed Jan 20, 2021.