Characterisation of reticular pseudodrusen and their central target aspect in multi-spectral, confocal scanning laser ophthalmoscopy

Abstract

To analyse reticular pseudodrusen (RPD) in patients with age-related macular degeneration (AMD) using multi-spectral (MS), confocal scanning laser ophthalmoscopy (cSLO). cSLO images (blue fundus autofluorescence [FAF; exc., λ = 488; em., λ = 500-700 nm], near-infrared reflectance [IR; λ = 820 nm], MS [blue reflectance (BR) λ = 488 nm, green reflectance (GR) λ = 515 nm, IR λ = 820 nm], as well as colour fundus photographs (CFP) were taken of 200 eyes from 100 AMD patients suspected to show RPD on the basis of funduscopy or previous fundus imaging. FAF and IR images were graded by two independent readers. If both readers concordantly confirmed the presence of RPD in both modalities, eyes were subsequently also graded for RPD in MS, BR, GR, green-blue enhanced mode (GBE), and CFP. Besides, FAF, IR, and MS images were evaluated for the presence of a target aspect, which represents a common feature of RPD lesions. The presence of RPD was confirmed using FAF and IR images by both readers in 130 eyes of 76 patients. In those eyes, both readers concordantly diagnosed RPD in MS images in 124 (95.4%) eyes (BR: 52 [40.0%], GR: 63 [48.5%], GBE: 101 [77.7%], CF: 27 [20.8%]). Cohen kappa statistics revealed excellent inter-observer agreement for MS (0.95) and GBE (0.85), substantial agreement for BR (0.75), GR (0.78), and moderate agreement for CFP (0.59). A target aspect within RPD lesions was detected in 45 of 130 (35.0%) included eyes using FAF and IR. The presence of a target aspect improved the recognition of RPD lesions in all modalities. If a target aspect was present, RPD were diagnosed in 45 eyes (100%) using MS (GBE: 42 eyes [93.3%], BR: 30 eyes [66.7%], GR: 37 eyes [82.2%], CFP: 17 eyes [37.8%]). Using MS cSLO, a target aspect could be identified in 75 of 130 (57.7%) included eyes. MS cSLO imaging is equivalent to FAF and IR in identifying RPD in AMD patients. Higher identification rates in BR and GR of those RPD lesions featuring a target aspect confirm the current hypothesis of RPD localisation and its progression further into the photoreceptor layers. MS seems to be more sensitive in identifying a central target aspect in RPD lesions compared to blue FAF and IR.