Data is sourced from ophthalmic payments systems, maintained by primary care services in NHS Shared Services Partnership (NWSSP).
Prior to 2023-24, similar services to Wales General Ophthalmic Services (WGOS) 1 were offered through GOS 1 and GOS 6 claims. For WGOS optical vouchers, similar services were offered through GOS 3 and GOS 4.
Sight test data collected through WGOS 1 is subject to some estimation. Due to the scale of the number of sight tests, the information from only 1 in 50 sight tests is recorded to a database. This means that the information from that sample is scaled up to estimate the number of sight tests by eligibility criteria.