Autofluorescence of treated retinoblastoma

Diagnostic imaging of retinal astrocytomas: A case-series

OBJECTIVES

To use multimodal imaging techniques to characterise features of retinal astrocytomas (RA) which would aid practitioners distinguish them from other causes of non-pigmented fundal lesions.

METHODS

Retrospective analysis of notes and imaging of 17 patients diagnosed with RA at a single centre between January 2012 and June 2021 was conducted. Demographics, examination findings and imaging including colour fundus photography, optical coherence tomography (OCT), infra-red (IR) and ultrasound (US) were analysed. These were compared to differential diagnoses, including retinoblastomas, amelanotic choroidal melanomas, choroidal metastases and idiopathic scleromas.

RESULTS

Fourteen patients (82%; 14/17) had idiopathic RA and three (18%; 3/17) were associated with tuberous sclerosis. Mean age at presentation was 43 years. Twelve patients (71%; 12/17) were asymptomatic. Thirteen (76%; 13/17) had better than 6/12 vision, with 41% (7/17) better than 6/6. All lesions were creamy-white. There were two distinct appearances, seven (39%; 7/18) were poorly-defined translucent retinal elevations and eleven (61%; 11/18) were well-defined solid opaque retinal masses. Six (33%; 6/18) displayed clustered, calcified spherules giving them the pathognomonic 'mulberry-like' appearance. On OCT, all appeared as dome-shaped retinal thickening with disruption of the inner retinal layers and nine (60%; 9/15) had intra-retinal cystic spaces giving a 'moth-eaten' appearance. Mean basal diameter and thickness on OCT was 2.93 mm and 0.86 mm, respectively. High internal reflectivity on US was noted in 92% (11/12).

CONCLUSIONS

RAs display characteristic clinical, demographic and imaging features which can aid differentiating them from other non-pigmented fundal lesions. We advise using multiple imaging modalities when diagnosing these lesions.

Fundus autofluorescence imaging

Fundus autofluorescence (FAF) imaging is an in vivo imaging method that allows for topographic mapping of naturally or pathologically occurring intrinsic fluorophores of the ocular fundus. The dominant sources are fluorophores accumulating as lipofuscin in lysosomal storage bodies in postmitotic retinal pigment epithelium cells as well as other fluorophores that may occur with disease in the outer retina and subretinal space. Photopigments of the photoreceptor outer segments as well as macular pigment and melanin at the fovea and parafovea may act as filters of the excitation light. FAF imaging has been shown to be useful with regard to understanding of pathophysiological mechanisms, diagnostics, phenotype-genotype correlation, identification of prognostic markers for disease progression, and novel outcome parameters to assess efficacy of interventional strategies in chorio-retinal diseases. More recently, the spectrum of FAF imaging has been expanded with increasing use of green in addition to blue FAF, introduction of spectrally-resolved FAF, near-infrared FAF, quantitative FAF imaging and fluorescence life time imaging (FLIO). This article gives an overview of basic principles, FAF findings in various retinal diseases and an update on recent developments.

The radioprotector ortho-phospho-L-tyrosine (pTyr) attenuates the side effects of fractionated irradiation in retinoblastoma mouse models but also decreases the local tumour control

BACKGROUND

Radiotherapy (RT) is used to treat retinoblastoma (Rb), the most frequent ocular tumour in children. Besides eradicating the tumour, RT can cause severe side effects including secondary malignancies. This study aimed to define whether the radioprotector ortho-phospho-L-tyrosine (pTyr) prevents RT-induced side effects and affects local tumour control in a xenograft and a genetic orthotopic Rb mouse model.

METHODS

B6;129-Rb1tm3Tyj/J (Rb^+/-) and Y79-Rb cell-xenografted nude mice were fractionated external beam irradiated (15 fractions of 5Gy 6MV photons during 3weeks) with or without pTyr pre-treatment (100mg/kg BW, 16h prior to each irradiation). One, three, six and nine months after RT, tumour control and RT toxicity were evaluated using in vivo imaging and histology. We also analysed pTyr dependant post irradiation cell survival and p53 activity in vitro.

RESULTS

In vitro pTyr pre-treatment showed no radioprotection on Y79 cells, but led to p53 stabilisation in unirradiated Y79 cells and to a facilitation of radiation-induced p21 up-regulation, confirming a modulation of p53 activity by pTyr. In both mouse models, secondary tumours were undetectable. In Rb^+/- mice, pTyr significantly lowered RT-induced greying of the fur, retinal thickness reduction and photoreceptor loss. However, in the xenografted Rb model, pTyr considerably decreased RT-mediated tumour control, which was observed in 16 out of 22 control eyes but in none of the 24 pTyr treated eyes.

CONCLUSIONS

In Rb^+/- mice pTyr significantly prevents RT-induced greying of the fur as well as retinal degeneration. However, since non-irradiated control mice were not used in our study, a formal possibility exists that the effect shown in the retina of Rb^+/- mice may be due to ageing of the animals and/or actions of pTyr alone. Unfortunately, as tested in a xenograft model, pTyr treatment reduced the control of Rb tumours.

Establishment of a novel retinoblastoma (Rb) nude mouse model by intravitreal injection of human Rb Y79 cells - comparison of in vivo analysis versus histological follow up

Retinoblastoma (Rb) is the most frequent primary intraocular tumour in children and, if left untreated, can cause death. Preclinical animal models that mimic molecular, genetic, and cellular features of cancers are essential for studying cancer and searching for promising diagnosis and treatment modalities. There are several models described for Rb, but none of them fully meet our requirements. The aim of this study was to create a novel xenograft-nude mouse-model with broad application possibilities, which closely resembles the clinical observations of Rb patients and which could be used to investigate the development and spread of the tumour by using scanning laser ophthalmoscopy/optical coherence tomography (SLO/OCT) as well as histology methods. We injected human retinoblastoma Y79 cells intravitreally in both eyes of immune-deficient nude mice. The incidences of retinoblastoma as well as growth velocity were analysed 3, 6, 9 and 12 weeks after cell injection in vivo by SLO/OCT as well as ex vivo by electron microscopy (EM) and hematoxylin/eosin (HE) staining. Moreover, internal organs were histologically screened for potentially occurring metastases. Three weeks post-injection, animals developed a retinoblastoma, and after five weeks tumour growth resulted in swelling of the eyes in individual animals, showing a similar phenotype to that of untreated Rb patients at advanced stages of tumour-development. After 12 weeks, 67.5% of all analysed eyes (29 of 42) contained a retinoblastoma. At early stages of Rb development, the SLO/OCT analysis correlated with the histology results. If the tumours were too large, only histological investigations were feasible. The ultrastructural characteristics of the xenograft-tumours were very similar to those described for patient's tumours. In one mouse, brain metastases were observed. Our retinoblastoma mouse model closely resembles the human disease. SLO/OCT can be used for the detection of Rb at early stages of development and could be used for monitoring the success of future therapies.

Summary: We present a novel retinoblastoma nude xenograft mouse model which closely resembles the human disease and allows broad application possibilities and a comparison of in vivo and histological analysis.

Spectral-Domain Optical Coherence Tomography and Fundus Autofluorescence Features in a Case of Typical Retinocytoma

Purpose

To report spectral-domain optical coherence tomography (OCT) and fundus autofluorescence (FAF) features observed in a case of typical retinocytoma.

Methods

Case report.

Results

A 17-year-old girl on routine ophthalmologic evaluation for headache had an elevated translucent lesion with peripheral pigmentation and adjacent chorioretinal atrophy close to the disc in the nasal retinal quadrant of the left eye. The lesion was confirmed to be retinocytoma on fluorescein angiography. Optical coherence tomography revealed a hyperreflective layer akin to preserved nerve fiber layer overlying the lesion in most of the scans. Symmetrical hyporeflective spaces in the underlying choroid and at places sudden disruption of choroid was also observed in the area of choroidal atrophy. Fundus autofluorescence revealed areas of hyperfluorescence, isofluorescence, and hypofluorescence in the different regions of the lesion. These features on FAF were consistent with posttreatment regressed retinoblastoma. Scleral hyperreflectivity on OCT as well as unmasked hyperfluorescence on FAF was observed in areas of chorioretinal atrophy.

Conclusions

We report novel findings of superficial hyperreflective layer presumed to be preserved nerve fiber layer in a case of typical retinocytoma as well as FAF features consistent with regressed retinoblastoma.

Fundus autofluorescence findings of choroidal osteoma

PURPOSE

To describe fundus autofluorescence (FAF) characteristics associated with choroidal osteomas and their secondary complications.

METHODS

Retrospective descriptive case series of six eyes of five patients with choroidal osteomas. Findings of FAF correlated with visual acuity, clinical features, lesion characteristics, and findings from other imaging modalities.

RESULTS

All 6 choroidal osteomas (100%) had totally or partially calcified, orange portions that were isoautofluorescent. Partial decalcification also produced areas of hyperautofluorescence and granular hypoautofluorescence corresponding to overlying retinal pigment epithelium mottling in 3 eyes (50%). Total decalcification with retinal pigment epithelial atrophy produced decreased FAF in 2 eyes (33%). Serous retinal detachment was present in 3 eyes (50%). When the overlying retinal pigment epithelium was viable, hyperautofluorescence as a result of elongation of the outer segments of photoreceptor was observed. In one eye where geographic atrophy of the retinal pigment epithelium was present, FAF was decreased even in the presence of serous retinal detachment. Portions of three partially or totally decalcified osteomas within the treatment field of photodynamic therapy for choroidal neovascularization were hypoautofluorescent. Four eyes (67%) had reduced foveal FAF and visual acuity <20/20, while both eyes with foveal isoautofluorescence had normal (20/20) visual acuity.

CONCLUSION

Calcified portions of choroidal osteomas not previously treated with photodynamic therapy were isoautofluorescent. Decalcification and secondary complications of serous retinal detachment, choroidal neovascularization, and geographic atrophy altered foveal autofluorescence and were associated with reduced visual acuity.