The role of fundus autofluorescence in late-onset retinitis pigmentosa (LORP) diagnosis

Structural evaluation in inherited retinal diseases

Ophthalmic genetics is a field that has been rapidly evolving over the last decade, mainly due to the flourishing of translational medicine for inherited retinal diseases (IRD). In this review, we will address the different methods by which retinal structure can be objectively and accurately assessed in IRD. We review standard-of-care imaging for these patients: colour fundus photography, fundus autofluorescence imaging and optical coherence tomography (OCT), as well as higher-resolution and/or newer technologies including OCT angiography, adaptive optics imaging, fundus imaging using a range of wavelengths, magnetic resonance imaging, laser speckle flowgraphy and retinal oximetry, illustrating their utility using paradigm genotypes with on-going therapeutic efforts/trials.

Occult inflammation detected by autofluorescence May Be the cause of idiopathic choroidal neovascularization

Purpose

To describe retinal pigment epithelium (RPE) disease detected by fundus autofluorescence (FAF) imaging in eyes with idiopathic choroidal neovascularization (ICNV).

Methods

A retrospective review of patients seen during a 14-month period with the diagnosis of ICNV was performed to identify patients with RPE disease, defined as hypo or hyperautofluorescent lesions on FAF. The presence of ICNV was confirmed by clinical history, ophthalmoscopic examination, fluorescein angiography (FA), and spectral domain-optical coherence tomography (SD-OCT). The clinical diagnosis of an underlying inflammatory condition was based on the FAF appearance of multiple punched-out hyper or hypoautofluorescent spots in the retinal fundus.

Results

The mean age was 27 years (range, 21-33 years). Best-corrected visual acuity ranged from 20/25 to 20/200 with a median visual acuity of 20/80. Ten eyes of 8 patients presented RPE abnormalities on FAF. Of the 10 study eyes, ICNV was observed in 8 eyes. ICNV appeared as a type 2 neovascular membrane at the macular area on FA, and SD-OCT revealed neurosensory detachment in all study eyes. FAF demonstrated abnormalities of the RPE that were not appreciated on clinical examination or by other imaging modalities.

Conclusions

FAF may reveal an underlying inflammatory condition in patients diagnosed as ICNV, modifying the diagnosis and management.

Spotlight on fundus autofluorescence

Fundus autofluorescence (FAF) imaging is based on the fluorescence from ocular endogenous fluorophores located in the retinal pigment epithelium and choroid, mainly lipofuscin and melanin. It is a noninvasive technique that provides information about the spatial distribution of lipofuscin/melanin and retinal pigment epithelium health status. An overview about the fluorophores responsible for FAF imaging and the usefulness of FAF imaging in the noninvasive assessment and monitoring of retinal diseases, such as age-related macular degeneration, diabetic retinopathy, diabetic macular edema, central serous chorioretinopthy, retinitis pigmentosa and retinal dystrophies, are discussed in this review.

Confocal scanning laser ophthalmoscopy versus modified conventional fundus camera for fundus autofluorescence

INTRODUCTION

Fundus autofluorescence (FAF) is a noninvasive imaging method to detect fundus endogenous fluorophores, mainly lipofuscin located in the retinal pigment epithelium (RPE). The FAF provides information about lipofuscin distribution and RPE health, and consequently an increased accumulation of lipofuscin has been correlated with ageing and development of certain retinal conditions. Areas covered: An exhaustive literature search in MEDLINE (via OVID) and PUBMED for articles related to ocular FAF in retinal diseases and different devices used for acquiring FAF imaging was conducted. Expert commentary: This review aims to show an overview about autofluorescence in the RPE and the main devices used for acquiring these FAF images. The knowledge of differences in the optical principles, acquisition images and the image post-processing between confocal scanning laser ophthalmoscopy and modified conventional fundus camera will improve the FAF images interpretation when are used as a complementary diagnosis and monitoring tool of retinal diseases.

Bilateral Concordance of the Fundus Hyperautofluorescent Ring in Typical Retinitis Pigmentosa Patients

BACKGROUND

It has long been assumed that in retinitis pigmentosa, disease presentation and progression are symmetrical. This study investigated whether hyperautofluorescent ring size, one known marker of disease progression, is symmetrical in typical RP patients.

MATERIALS AND METHODS

A total of 88 patients with typical retinitis pigmentosa were enrolled in the study. Each presented with a hyperautofluorescent ring when imaged at baseline with fundus autofluorescence (AF). Vertical and horizontal diameters were analyzed according to mode of inheritance and age group. Seven of 88 patients had data missing in one eye and were excluded from further analysis.

RESULTS

There was no significant relationship between hyperautofluorescent ring diameter and inheritance mode. There was a tendency toward smaller ring size with age and 3.7% of subjects displayed marked asymmetry in ring size between right and left eyes, although their electroretinogram results did not differ. Overall, when patients were considered as a group, there was a high correlation between right and left eyes' horizontal and vertical diameters (r=0.99, p<0.0001; r=0.98, p<0.0001). Comparing individual patients' eyes, and accounting for measurement error, a smaller majority of patients displayed symmetry of the hyperautofluorescent ring in both dimensions (85.7% in the vertical dimension, 87.3% in the horizontal dimension).

CONCLUSION

This study confirmed the highly symmetrical nature of the hyperautofluorescent ring in RP patients, except in a small subgroup. AF results, which provide less variability per image, and are consistently interpreted between different observers, may be a more sensitive and reliable method for testing symmetry than many functional tests.

Next-generation sequencing revealed a novel mutation in the gene encoding the beta subunit of rod phosphodiesterase

PURPOSE

To report the phenotypes caused by a novel mutation in the PDE6B gene in a family with two affected siblings and one affected cousin with a 2-year follow-up.

DESIGN

Three patients from a family with a history of retinitis pigmentosa underwent clinical evaluations. The affected patients' DNA was analyzed using next-generation sequencing and segregation analyses were performed for the family.

SETTING

Edward S. Harkness Eye Institute, New York Presbyterian Hospital.

PARTICIPANTS

Two siblings, one cousin, and five unaffected family members.

MAIN OUTCOME MEASURES

Macular appearance assessed by funduscopy, autofluorescence imaging, spectral-domain optical coherence tomography and visual function assessed by electroretinography.

RESULTS

The proband, brother, and cousin had rod-cone degeneration with cystoid macular edema. Fundus autofluorescence showed hyperautofluorescent ring constriction over time. Spectral-domain optical coherence tomography revealed retinal pigment epithelium atrophy, loss of external limiting membrane, retinal layer thinning, and reduction in ellipsoid zone length over time. Next-generation whole exome sequencing revealed a homozygous c.1923_1969ins6del47 nonsense PDE6B mutation, which has not been previously described, that segregated with the disease in the family.

CONCLUSIONS

The homozygous PDE6B mutation causes retinitis pigmentosa. Acetazolamide treatment improved visual acuity but rod degeneration continued. Despite having the same mutation and living in the same environment, the proband's brother progressed at a faster rate starting at a younger age, suggesting that gene modifiers may influence the expressivity of the phenotype. Next-generation sequencing, used to discover this mutation, is a practical new technology that can detect novel disease-causing alleles, where previous arrayed primer extension (APEX) technology could not.