The primary objective of this study is to quantify disease progression measured by best corrected visual acuity (BCVA) in the real-world setting among Choroideremia (CHM) participants. The secondary objectives are to describe demographic and baseline clinical characteristics among CHM participants and to match CHM participants in the Intelligent Research in Sight (IRIS®) Registry to Biogen's investigator sponsored trial (IST) study population using propensity score matching.

This study is a retrospective cohort study of CHM eyes and participants which will include all eligible participants and eyes with the first documented diagnosis of CHM from July 1st, 2013 to December 31st, 2019 that meet the study criteria. This study will be conducted using data from American Academy of Ophthalmology's (AAO) IRIS® Registry which captures CHM participant's demographics, clinical characteristics and clinical outcomes from 2013.

Key Inclusion Criteria:

Cohort 1: All CHM Participants

• Participants with a documented diagnosis of CHM identified by the presence of International Classification of Diseases (ICD)-9/10 or SNOMED coding:

  1. ICD-9: 363.55
  2. ICD-10: H31.2
  3. SNOMED-CT: 75241009

Cohort 2: Trial-Matched CHM Participants

• Male participants with a documented diagnosis of CHM identified by the presence of ICD-9/10 or SNOMED coding:

  1. ICD-9: 363.55
  2. ICD-10: H31.21
  3. SNOMED-CT: 75241009

Key Exclusion Criteria:

• N/A

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.

Main cohort will include all eligible CHM participants in IRIS registry. Trial-matched cohort will include only male CHM participants from Cohort 1 to match Biogen's IST study population using propensity score matching.

In accordance with Biogen's Clinical Trial Transparency and Data Sharing Policy on http://clinicalresearch.biogen.com/