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Shyamanga Borooah, Vasileios Papastavrou, James R Cameron, Ashraf Khan, Andrew Browning, Baljean Dhillon; Multimodal imaging highlights novel phenotypic changes in late-onset retinal macular degeneration prior to loss of visual acuity. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2813.
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© ARVO (1962-2015); The Authors (2016-present)
Late-onset retinal macular degeneration(LORMD) is a rare but severe inherited macular degeneration whose early clinical diagnosis and monitoring has proven difficult.<br /> <br /> We use newer multimodal imaging to better define the phenotype of LORMD.
7 patients with genetically confirmed LORMD were investigated using ocular coherence tomography (OCT), indocyanine-green (ICG), and scanning laser ophthalmoscopy (SLO). SLO images were analysed using semi-automated software. This system was first validated using two masked graders. The average size of hypofluorescent patches and rate of progression was analysed on SLO.<br /> <br /> 8 age-sex matched controls were used for comparison in the OCT Studies. We measured choroidal thickness and neuroretinal thickness using Heidelberg segmentation software at the fovea. In order to measure deposit thickness at the macula photoreceptor/RPE thickness and neuroretinal retinal thickness were measured in the ETDRS regions. Microsoft Excel 2003-7 was used for all statistical analyses.
The average age of LORMD patients was 56.7 years(SD=5.2) with 5 males and 2 females whilst the control group was 57.9 years (SD=5.2) composed of 5 males and 3 females. Sizing of the hypofluorescent SLO patches was validated using Cronbach's method (α= 0.98). The average size of hypofluorescent patches was 3.6mm2 (range=0-26.8). There was a poor correlation with age and size of patches(R=0.12). The mean rate of progression was 2.5 mm2/year.<br /> <br /> There was no significant difference in neuroretinal thickness at the fovea. However, the choroid was significantly thinner in all LORMD cases (P<0.05) when compared with controls. Interestingly the photoreceptor/RPE layer was significantly thicker (P<0.05) in LORMD cases in the all the outer ETDRS regions only when compared with controls.
Although LORMD is a fully penetrant disease there is marked inter-patient variability. This paper confirms that in LORMD choroidal and sub-RPE deposit changes develop prior to neuroretinal loss. Furthermore the disease appears to have a greater propensity for the outer macula than the central macula and fovea in the early stages of disease.
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