Detection and characterisation of optic nerve and retinal changes in primary congenital glaucoma using hand-held optical coherence tomography

Abstract

Objective: To investigate (1) the feasibility of scanning the optic nerve (ON) and central retina with hand-held optical coherence tomography (HH-OCT) without sedation or anaesthesia in primary congenital glaucoma (PCG), (2) the characteristics of ON changes in comparison with adult primary open-angle glaucoma (POAG) in comparison with matched controls, (3) the sensitivity and specificity of ON parameters for diagnosis, and (4) changes of foveal morphology.

Methods and analysis: HH-OCT (Envisu 2300; Leica Microsystems) was used to investigate ON and foveal morphology of 20 children with PCG (mean age 4.64±2.79) and 10 adult patients with POAG (mean age 66.8±6.94), and compared with age-matched, gender-matched and ethnicity-matched healthy controls without sedation or anaesthesia.

Results: HH-OCT yielded useful data in 20 out of 24 young children with PCG. Patients with PCG had significantly deeper cup changes than patients with POAG (vs respective age-matched controls, p=0.014). ON changes in PCG are characterised by significant increase in cup depth (165%), increased cup diameter (159%) and reduction in rim area (36.4%) as compared with controls with high sensitivity (81.5, 74.1% and 88.9%, respectively) and specificity (85.0, 80.0% and 75.0%, respectively). Patients with PCG have a significantly smaller width of the macula pit (p<0.001) with non-detectable external limiting membrane.

Conclusion: HH-OCT has the potential to be a useful tool in glaucoma management for young children. We have demonstrated the use of HH-OCT in confirming a diagnosis of glaucoma within the studied cohort and found changes in disc morphology which characterise differently in PCG from POAG.

Keywords: child health (paediatrics); diagnostic tests/investigation; imaging.

Figure 1

Hand-held optical coherence tomography (HH-OCT) images of the optic nerve (ON) (A) and fovea (B) of the left eye of patient 6: (A) horizontal B-scan through the centre (deepest excavation) of the optic disc; the disc diameter was defined as an interval between the edges of Bruch’s membrane (red line), the cup diameter as the distance between the nasal and temporal internal limiting membrane (green dotted line) 150 µm anterior to the plane of the disc (blue line), the rim area consisted of the area anterior to the same plane (white dotted lines) within the disc edges (white vertical lines) and the internal limiting membrane (green dotted lines); maximal cup depth (vertical yellow line) was measured using a line perpendicular to the line between the cup diameter (blue line) and the deepest point of the cup; RNFL thickness was measured at 6° from disc margins (red dotted lines). (B) Horizontal B-scan of the fovea with labelled individual retinal layers (BM, Bruch’s membrane; ILM, inner limiting membrane; RNFL, retinal nerve fibre layer; GCL, ganglion cell layer; INL, inner nuclear layer; IPL, inner plexiform layer; IS, inner segment; ONL, outer nuclear layer; ELM, external limiting membrane; OPL, outer plexiform layer; OS, outer segment; RPE, retinal pigment epithelium). Retinal layer thickness was measured in the centre of the fovea, in the paracentral area (from 1° nasally to 1° temporally) and nasally and temporally (from 2° to 6°). The green line connecting the most prominent positions of the ILM nasally and temporally was used to define the foveal width; the yellow line indicates the foveal depth (the axial distance from the green line to the deepest point of the foveal pit); the area in blue indicates the foveal pit area. (C) Horizontal spectral domain–optical coherence tomography B-scan images of the optic nerve (top) and fovea (bottom) of patient 20 with primary congenital glaucoma in the left eye (PCG, middle column), an unaffected left eye (left column) and an eye of a healthy age-matched, gender-matched and ethnicity-matched control child (right column). On the ON scan, a larger and deeper cup is seen in PCG. On the foveal scan, the ELM is not visible in PCG while it is distinctly seen in the unaffected eye and in the healthy control.

Figure 2

Cross-sectional schematic diagrams representing mean values of optic nerve head parameters of patients with primary congenital glaucoma, adult open-angle glaucoma and matched healthy controls for each group (numeric values represent mean±SE). The upper horizontal dotted lines represent the horizontal offset (150 µm) used to determine cup diameters and the lower horizontal dotted lines indicate disc horizontal diameters. The vertical dotted lines show the margins of the rim areas. CDR, cup:disc ratio; N, nasal; RNFL, retinal nerve fibre layer; T, temporal.

Figure 3

(A–I) Distribution of optic nerve head parameters in patients with primary congenital glaucoma (PCG) and healthy controls. Horizontal dotted lines show optimal sensitivity and specificity thresholds for the optic nerve parameters that were highly sensitive and specific for PCG detection. BM, Bruch’s membrane; RNFL, retinal nerve fibre layer. (K) Optimal sensitivity and specificity thresholds, sensitivity and specificity analysis for optic nerve head parameters in patients with primary congenital glaucoma compared with healthy controls.