Using methanol to preserve retinas for immunostaining

BACKGROUND

Experimental studies on retinal vasculature and retinal ganglion cells (RGCs) investigating the developmental and pathological conditions of the retina mainly rely on whole-mount retinal immunostaining. Methanol, an auxiliary fixed medium for retinal whole-mount preparations, has been used in some studies; however, its application in short- and long-term storage of retinas for further study has not been well described. We aimed to evaluate methanol use as a preservation treatment for further immunostaining of the retina.

METHODS

We generated oxygen-induced retinopathy (OIR) and optic nerve crush (ONC) mouse models and used their retinas for analysis. We pipetted cold methanol (-20°C) on the surface of the retina to help fix the tissues while promoting permeability, after which the retinas were stored in cold methanol (-20°C) for 1, 6, or 12 months before being evaluated using various optical techniques. Thereafter, retinal whole-mount immunostaining was performed to analyse retinal neovascularisation and retinal hypoxia in OIR model, and retinal ganglion cell survival rate in ONC model.

RESULTS

Quantitative analysis revealed no significant differences in the fixed retinas after long-term storage in terms of retinal vasculature or retinal hypoxia in the OIR model. Similarly, no significant difference was found in RGC survival rate after long-term storage in methanol. These results suggest that methanol can be used as a storage medium when preserving retinal whole-mount samples.

CONCLUSIONS

Cold (-20°C) methanol can serve as an effective medium for long-term storage of fixed retinas, which is useful for further research.

Peripheral ischaemic retinopathy and neovascularisation in a patient with subacute streptococcus mitis-induced bacterial endocarditis

Objective: To describe a patient with peripheral retinal ischaemia and neovascularisation who was diagnosed with streptococcus mitis-induced bacterial endocarditis. Methods: Retrospective analysis of case report. A 57-year-old man presented with a history of a rapidly progressive, bilateral, painless visual loss. He also suffered from pain in the neck and lower back and a weight loss of 10 kg. He underwent a full ophthalmologic work-up, laboratory investigations, and imaging of the spine. Results: BCVA was reduced to 20/40 in the right eye and 20/32 in the left eye. Fundoscopy showed rare intra-retinal haemorrhages including few Roth spots and cotton wool lesions. Fluorescein angiography demonstrated large areas of peripheral retinal ischaemia and neovascularisation. Imaging of the spine showed spondylodiscitis on several levels. Further imaging and blood cultures confirmed bacterial endocarditis of the mitral valve. Streptococcus mitis was subsequently identified as the causative organism. Conclusion: Peripheral retinal ischaemia and neovascularisation were previously unrecognised as a feature of infectious endocarditis. Therefore, their presence, apart from the classic Roth spots, should prompt the consideration of infectious endocarditis in the etiologic work-up.

Choroidal melanoma treated with stereotactic fractionated radiotherapy and prophylactic intravitreal bevacizumab: The Dunedin Hospital experience

INTRODUCTION

Choroidal melanoma (CM) is the most common primary ocular malignancy in adults. This study reviewed the Dunedin Hospital (DH) experience in the treatment of CM with stereotactic fractionated radiotherapy (SRT) and the outcome of prophylactic use of intravitreal injection bevacizumab (PIB) in preventing radiation retinopathy (RR).

METHODS

A retrospective study was conducted of patients at DH who underwent SRT for CM with and without PIB from 1 January 2001 to 31 January 2012. In DH, some patients who had SRT following the introduction of intravitreal bevacizumab in December 2006 were also treated with PIB with the expectation that this might reduce the risk of developing RR, although the evidence of its effectiveness in this respect is not clear. The primary outcome measure was local progression as monitored with regular ultrasound. Secondary outcome measures were metastatic progression incidence, enucleation incidence, no functional vision incidence, overall survival, disease-specific mortality, incidence of RR, and radiotherapy to clinical diagnosis of RR time.

RESULTS

Twenty-seven patients who were followed up at DH were reviewed after a mean follow-up of 5.1 years (range 0.4-12.6). Fourteen patients received PIB. The local progression, metastatic progression and enucleation rate were 4%, 8% and 11%, respectively. The no functional vision (hand movements or less) rate was 62%. Overall survival was 63%, but only three (11%) deaths were due to metastatic choroidal melanoma. Incidence of RR was 57% and 54% for those that received PIB and those who did not, respectively. PIB did not reduce the rate of RR (P = 1.00).

CONCLUSION

This study reaffirmed that SRT achieves very good local control and eye retention rates. PIB did not appear to reduce the radiation retinopathy rate in this study, and more studies are required especially Phase II and III trials to determine PIB efficacy in preventing RR.