June 2017
Volume 58, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2017
Quantitative assessment of photoreceptor degeneration by confocal scanning laser ophthalmoscopy in two mouse models of retinitis pigmentosa
Author Affiliations & Notes
  • Harry O Orlans
    Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, United Kingdom
    Oxford Eye Hospital, Oxford, United Kingdom
  • Alun R Barnard
    Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, United Kingdom
    Oxford Eye Hospital, Oxford, United Kingdom
  • Robert E MacLaren
    Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, United Kingdom
    Oxford Eye Hospital, Oxford, United Kingdom
  • Footnotes
    Commercial Relationships   Harry Orlans, None; Alun Barnard, None; Robert MacLaren, None
  • Footnotes
    Support  MRC/Fight for Sight
Investigative Ophthalmology & Visual Science June 2017, Vol.58, 4874. doi:
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      Harry O Orlans, Alun R Barnard, Robert E MacLaren; Quantitative assessment of photoreceptor degeneration by confocal scanning laser ophthalmoscopy in two mouse models of retinitis pigmentosa. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4874.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Imaging techniques such as ocular coherence tomography (OCT) have revolutionised the assessment of retinal disease in both humans and animal models. In degenerative states or following surgery, where normal lamellar architecture of the retina may be disorganised, segmentation technology may be insufficient to accurately quantify outer nuclear layer (ONL) loss, particularly if this is non-uniform. Here we describe a novel technique for the in vivo quantification of outer retinal degeneration using the confocal scanning laser ophthalmoscope (cSLO) and validate this in two mouse models of retinitis pigmentosa.

Methods : Transgenic mice carrying an Nrl-EGFP allele and homozygous for either knock-out of rhodopsin (Nrl-EGFP, Rho-/-) or heterozygous for knock-in of P23H mutant rhodopsin (Nrl-EGFP, RhoP23H/+) were used in this study. These novel strains have green fluorescent rods which undergo a progressive degeneration. Fundus imaging was performed at three weekly intervals by infrared reflectance and blue light fluorescence cSLO. Mean grey values (mGV), which quantify average fluorescence levels within retinal cSLO images, were compared for degenerate and age-matched Nrl-EGFP, non-degenerate (Nrl-EGFP, Rho+/+) controls. Mice were sacrificed at a range of post-natal ages and photoreceptor layer (PRL) thickness measured by histology was correlated with mGV.

Results : Mean grey value positively correlated with corresponding PRL thickness as measured histologically (r2=0.75, P<0.0001). Recorded mGV significantly decreased over time in the Rho-/- and RhoP23H/+ groups but was maintained in Rho+/+ mice (P<0.001 for effect of time in both degenerate groups; P<0.0001 for both Rho-/- versus Rho+/+ and RhoP23H/+ versus Rho+/+, two-way ANOVA). This corresponded to ONL thinning as measured by OCT and histology. The mGV of superior retina was significantly greater than that of inferior retina in RhoP23H/+ (P<0.0001) but not age-matched Rho-/- (P=0.57) mice which reflected histological findings.

Conclusions : Fluorescence labelling of rod photoreceptors permits in vivo characterisation of models of retinitis pigmentosa and may provide new insights into patterns of degeneration or rescue effect after treatment. Mean grey value can be used in such cases to quantify the degree of ONL degeneration and can identify regional variations in photoreceptor loss.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

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