Table 2

Sources of ascertainment of index patients

Source No of patients ascertained
Diagnostic index of department of clinical genetics24
Practising ophthalmologists2
Practising optometrists0
Record book of visual function unit at BMEH14
Schools for deaf including schools with special units3
SENSE (National Deafblind and Rubella Association)3
Psychiatric services for the deaf (Queen Elizabeth Hospital Birmingham)4
Total index patients31
Number of secondary cases18
Total probands in prevalence study49

  • ↵18 probands were ascertained more than once.

  • ↵The assessed relatives who were living in the city of Birmingham in June 1994 and who were aged over 15 years.