Table 1.

Minimum target and achieved recruitment quotas

Criteria	Target (N = 60)	Actual (N = 66)*
Age (years)
Caregiver of child 3–5 years	n = 1	n = 6
Caregiver of child 6–11 years	n = 1–2	n = 9
Child (6–11 years)	n = 3–4	n = 8
Adolescent (12–17 years)	n = 3–4	n = 10
Adult (18 years and over)	n = 3–4	n = 33
RP genotype
RLBP1 RP	n = 1–2	n = 8
RPE65 RP	n = 1–2	n = 1
RPE65 LCA	n = 1–2	n = 12
X-linked/RPGR RP	n = 1–2	n = 16
PRPF31 RP	n = 1–2	n = 2
Rhodopsin gene (RHO)	n = 1–2	n = 2
Patient-reported severity of RP
Very mild	n = 1–2	n = 0
Mild	n = 1–2	n = 6
Moderate	n = 1–2	n = 17
Severe	n = 1–2	n = 17
Very severe	n = 1–2	n = 10
Visual acuity* score of the left eye
Mild (> 60 letters)	n = 1–2	n = 21
Moderate (36–60 letters)	n = 1–2	n = 13
Severe (5–35 letters)	n = 1–2	n = 11
Very severe (< 5 letters)	n = 1–2	n = 10
N/A (blind)	N/A	n = 2
Visual acuity* score of the right eye
Mild (> 60 letters)	n = 1–2	n = 24
Moderate (36–60 letters)	n = 1–2	n = 13
Severe (5–35 letters)	n = 1–2	n = 10
Very severe (< 5 letters)	n = 1–2	n = 7
N/A (blind)	N/A	n = 2

n = 1 caregiver was included in the total sample twice, as they were interviewed separately about their two children with RP/LCA. For the concept elicitation interviews, counts were included for each child separately however, the caregiver only completed the cognitive debriefing of the ViSIO-ObsRO once

*Visual acuity score as defined by ETDRS (Early Treatment Diabetic Retinopathy Study) letter score (if every letter read correctly on that line and all lines above it on the chart) [26]