Table 2 Differential diagnosis of posterior scleritis
From: Choroidal involvement in non-infectious posterior scleritis
| Â | Posterior scleritis | |||
|---|---|---|---|---|
Typical clinical characteristics | ||||
 Laterality | Mostly unilateral | Unilateral or bilateral | Bilateral (second eye involvement within 2 weeks) | Unilateral |
 Presenting symptoms | Acute painful vision loss (typically worse at night or on eye movements) | Painless vision loss | Blurred vision, photophobia, ocular pain. Associated systemic symptoms depending on disease stage. | Painless visual changes (rarely painful when necrotic). Can be asymptomatic. |
 Associated clinical signs | Anterior scleritis, anterior uveitis, vitreous inflammation, choroidal folds, optic disc edema. | Round/oval serous retinal detachment with or without detachment of retinal pigment epithelium (RPE), RPE changes (focal or multifocal). No associated inflammatory signs. | Granulomatous anterior uveitis, vitritis, diffuse choroiditis, Dalen-Fuchs nodules, sunset glow fundus, optic disc edema. Frequent associated skin changes, CNS findings (incl. Cerebrospinal fluid pleocytosis) | Pigmented or amelanotic elevated choroidal mass, lipofuscin often present. Serous RD and/or sentinel vessel possible. Associated inflammation rare. |
 Response to steroids | Improvement of pain and imaging findings | Can worsen presenting signs and symptoms | Improvement of pain and imaging findings | None |
Multimodal imaging findings | ||||
 B-scan ultrasound | T-sign, increased thickness of the posterior coats (> 2.0 mm), nodular subtype possible (sessile or dome shaped lesion with high internal reflectivity) | Serous RD possible | Serous RD possible | Dome-shaped or mushroom-shaped choroidal lesion with typically low to medium internal reflectivity. Choroidal excavation and serous RD possible. |
 OCT | Choroidal folds, serous retinal detachment, macular oedema | Subretinal fluid (SRF) (can be multifocal), RPE-detachment(s), intraretinal fluid (IRF) possible, atrophic RPE-changes possible | Serous retinal detachment with typical fibrinous septa | Dome-shaped solid choroidal mass, accompanying SRF possible |
 EDI-OCT | Localized choroidal thickening in affected eye in acute stages, choroidal thinning after treatment or in advanced stages | Diffuse choroidal thickening, dilated large vessels in Haller’s layer with thinning of overlying smaller vessels in Sattler’s layer and choriocapillaris | Choroidal thickening in acute stages, choroidal thinning after treatment or in advanced stages | Dome-shaped solid choroidal mass with smooth surface |
 FA | Early pinpoint leaks with late pooling in cases with subretinal fluid | Focal leak in acute phase (typically described as ‘ink blot’ or ‘smokestack’ leakage pattern). Multifocal leakage (‘hot spots’) and pooling under detached RPE possible. Disc leak absent. | Focal areas of delayed choroidal perfusion, multiple pinpoint regions of leakage at the RPE-level, disc hyperfluorescence | Multiple areas of pinpoint leakage |
 ICGA | Choroidal vasculitis, zonal choroidal hyperfluorescence (± pinpoint leakage), choroidal perfusion delay, enlargement of draining choroidal veins, and hypofluorescent dark dots | Early phase: large, dilated, densely packed choroidal vessels. Mid-to late-phase: choroidal vascular hyperpermeability (focal or multifocal hyperfluorescent staining with indistinct borders). | Early phase: hyperfluorescence. Early-to-mid-phase: hypofluorescence. | Mixed pattern of fluorescence, blockage of fluorescence in pigmented lesions |