The role of the disc damage likelihood scale in glaucoma detection by community optometrists

Recent guidelines recommend disc damage likelihood scale (DDLS) is recorded for all referrals of suspected glaucoma from community optometrists to hospital eye services (HES) in Scotland. This study aimed to determine whether lower DDLS grades were associated with higher rates of discharge at the first visit to HES.

A retrospective analysis of 618 consecutive new referrals from community optometrists to a university hospital glaucoma service. 65 (10.5%) included DDLS graded by the community optometrist. A comprehensive eye examination and optical coherence tomography (OCT) was performed in the hospital glaucoma clinic and first visit discharge rate (FVDR) for different grades of DDLS compared. The relationship between DDLS and retinal nerve fibre layer (RNFL) thickness on OCT was also examined.

The FVDR for patients with DDLS recorded in the referral was 27.7% (18 of 65) compared to 25% (138 of 553) in those without DDLS (p = 0.631). The FVDR was 50% for those with a DDLS of 3 in the worse eye, decreasing to 32% and 21% for DDLS grades of 4 and 5 respectively. No patient with a DDLS ≥ 6 was discharged at the first visit and none with a DDLS < 4 (the cut off for consideration of referral in Scottish guidelines) were found to have glaucoma. There was a significant but weak inverse relationship between DDLS and RNFL thickness. The strongest relationship was with average RNFL thickness (r = -0.378, p < 0.01) followed by superotemporal (r = -0.359, p < 0.01) and inferotemporal (r = -0.353, p < 0.01) RNFL thickness.

In patients referred to HES with DDLS information included, lower DDLS grading was associated with higher odds of being discharged at the first visit. DDLS grading by community optometrists had a poor correlation with RNFL thickness measured using OCT.