How is minimal clinically important difference (MCID) reported in ophthalmology randomised controlled trials a systematic review

Topic: We reviewed the use of minimal clinically important difference (MCID) or related terminology, as well as the analysis of clinical relevance in ophthalmology trials, both in study design and in result reporting.

Clinical relevance: MCID is defined as “the smallest difference in any outcome of interest that patients perceive as beneficial or harmful.” It represents the minimum difference needed to consider two interventions as different or to justify a change in disease management.

Methods: We searched four databases (Medline, Embase, CENTRAL, and PubMed) from January 1, 2020, to April 15, 2024, for randomized clinical trials (RCTs) and protocols related to glaucoma, age-related macular degeneration (AMD), and diabetic retinopathy (DR). Primary outcomes were the presence of MCID or related terminology and its use in sample size estimation and result interpretation. The secondary outcome was the mention of practical importance or clinical relevance. The review followed PRISMA guidelines and was registered in PROSPERO (CRD42024536217).

Results: Sixty-four trials were included. Only three studies (4.7%), one in neovascular AMD and two in diabetic macular edema, used MCID or similar concepts for sample size calculation and interpretation. These addressed clinically significant changes in visual acuity, NEI-VFQ scores, and central subfield thickness. Nine trials (14.1%) mentioned clinical relevance or practical importance.

Conclusion: MCID is seldom used in ophthalmology RCTs. Most studies rely solely on statistical significance, which may not reflect meaningful clinical differences. Incorporating MCID in trial design can optimize sample size, improve interpretation, and enhance the clinical value of findings.

Jorge Monasterio-Bel, MD, FEBO, is a consultant ophthalmologist at the University Hospital of Burgos, Spain, with a clinical and academic interest in glaucoma. He completed his ophthalmology residency at the same institution and holds the Fellowship of the European Board of Ophthalmology (FEBO). He also holds an official Master’s degree in Health Sciences Research Methodology. He has received specialized glaucoma training in Spain and the United Kingdom, including experience at the Belfast Health and Social Care Trust. Dr. Monasterio-Bel is the author or co-author of multiple scientific publications and has presented more than 30 communications at national and international ophthalmology meetings. He is a member of the European Glaucoma Society and the World Glaucoma Association.