Towards a FHIR Specification for Research in Ophthalmology: Designing the EyeMatics Core Data Set for Multi-Centric Data Integration.

Introduction: EyeMatics (Eye disease "treated" with interoperable medical informatics) is a clinical use case in Germany's Medical Informatics Initiative (MII). The objective of EyeMatics is to improve the understanding of the treatment effects of intravitreal injections, the most frequent procedure to treat retinal diseases. To achieve this, as part of the efforts, medical data of multiple hospital sites must be integrated into a local FHIR repositories using a common set of FHIR profiles.

Methods: A panel of medical and technical experts was formed to create a project-specific core data set. The core data set is compiled from different preliminary work like previously existing data models, the data donation of a synthetic patient encounter scenario, screenshots of UI forms used at the local sites and relevant MII profiles.

Results: Complex profiling and custom code systems were required to represent central ophthalmic concepts such as visual acuity using FHIR. A common pattern for representing eye laterality in FHIR Observation resources was established. The resulting profiles are available in a public GitHub repository.

Conclusion: While our FHIR profiles will be sufficient for EyeMatics, our experience shows that the clinical complexity of basic ophthalmological observations requires some deviations from standard FHIR modelling patterns and would be limited by gaps in terminology if deployed elsewhere. Our experience indicates that project-specific FHIR profile development is possible within a short time frame but may harbor risks of contributing to a growing number of fragmented implementations unless closely coordinated or based on common data models. To counteract this, future ophthalmic MII extension modules should attempt to integrate both profiles described here and international standard data models for ophthalmology.