Clinical and Experimental Ophthalmology最新文献

Background: The Feline Leukaemia Virus Subgroup C Receptor 1 (FLVCR1) has been recognized as a heme exporter essential for erythropoiesis, and emerging research identifies its novel function as a choline transporter. Mutations in FLVCR1 have been associated with the pathogenesis of retinitis pigmentosa (RP); however, the roles of FLVCR1 in retina remain unexplored. This study aims to elucidate the connection between FLVCR1 and RP and investigate potential therapeutic interventions.

Methods: Utilizing CRISPR/Cas9 technology, we established retina-specific Flvcr1 knockout (SKO) and rod-specific Flvcr1 knockout (RKO) mouse models to investigate the in vivo functions of FLVCR1 in the retina. We performed optical coherence tomography (OCT) to assess the retinal thickness, electroretinography (ERG) to test the retinal function and histopathological sections and staining to analyse the pathological changes. Additionally, we administered choline supplementation treatment (CST) to evaluate its potential efficacy in alleviating symptoms of retinal degeneration.

Results: Genotyping and immunoblotting analyses confirmed the successful establishment of the SKO and RKO mouse models. Retinal degeneration in SKO mice manifested at postnatal day 14, while its onset in RKO mice occurred at P25, including diminished scotopic electroretinogram (ERG) responses, progressive degeneration of photoreceptor cells, infiltration of microglia into the outer nuclear layer (ONL) and disruption of mitochondrial homeostasis. Notably, we found that choline supplementation in RKO mice alleviated the associated phenotypes.

Conclusions: We developed two innovative mouse models and revealed that FLVCR1 is critical for maintaining mitochondrial homeostasis and supporting photoreceptor survival. Choline supplementation serves as a therapeutic intervention for RP caused by FLVCR1 mutations.

Background: Endophthalmitis requiring multiple ocular tissue sampling for microbiological testing is uncommon and has not been previously studied. This study aims to analyse cases with at least two ocular tissue samplings and testing of different ocular samples against culture yields.

Methods: A 27-year prospective observational study using data from the Victorian Endophthalmitis Registry, managed through the REDCap data platform. The study included 314 patients (317 eyes) who underwent at least two aqueous or vitreous specimen collections. The primary outcome measures included microbiological culture results from repeat and multiple intraocular samples and identification of isolated microorganisms.

Results: The overall initial culture positivity rate was 75.7%, while the culture positivity rate at the second intervention was 34.7%. First vitreous taps had the highest culture yield (72.6%) among different sample types. Notably, 19.5% of eyes with initial negative vitreous cultures had subsequent positive results. Further analysis showed that 24.4% of eyes with initial negative vitreous cultures had corresponding positive aqueous cultures. Additionally, 12.2% of eyes with negative initial vitreous taps yielded positive cultures from vitreous biopsies or washings from vitrectomy. Staphylococcus and Streptococcus species were the main pathogens isolated (40.4% and 31.3% of cases respectively).

Conclusions: Our study demonstrated the trends and utility of repeated and different ocular tissue sampling in challenging endophthalmitis. Aqueous taps are most useful at the first biopsy, beyond which it has little diagnostic value. A second sampling can be valuable in patients who are initially culture-negative. Surgical specimens contribute meaningfully to the overall culture yield and enhance cumulative culture positivity.

Background: Familial exudative vitreoretinopathy (FEVR) is a disorder of retinal blood vessel development characterised by impaired retinal angiogenesis. While FZD4 mutations are established genetic causes of FEVR, the molecular mechanisms underlying pathological neovascularisation remain poorly understood.

Methods: CRISPR/Cas9 was used to generate the Fzd4^M105V mouse model. Comprehensive vascular phenotyping entailed retinal wholemount imaging, analysis of hyaloid vessel regression and immunohistochemical evaluation of the deep retinal vasculature. Flow cytometry sorting and single-cell RNA sequencing (scRNA-seq) were used to characterise the expression profiles of retinal endothelial cells (ECs) in mice.

Results: The FZD4^M105V model recapitulated key FEVR features including retinal aneurysmal vessels in adult mice, developmental abnormalities in juveniles, impaired deep vascular formation, delayed hyaloid regression, vascular leakage and reduced endothelial proliferation. ScRNA-seq revealed distinct transcriptional profiles in pathological EC clusters and tip cells. KEGG analysis revealed that the EC clusters were enriched in focal adhesion, Rap1, PI3K-Akt and apelin signalling pathways, whereas tip cells were enriched in the VEGF, chemokine, NF-κB and TNF signalling pathways. We further identified four novel candidate markers of pathological neovascularisation: Ctss, Ccl4, Ccl3 and Apoe. Subsequent validation confirmed the upregulation of CTSS and CCL4 within neovascular lesions, supporting their functional role in pathological angiogenesis.

Conclusions: We established a novel mouse model of pathological neovascularisation with a missense mutation and elucidated the expression profiles of retinal ECs. The identified pathways and novel biomarkers-particularly CTSS and CCL4-provide new insights for further pathogenesis investigation of FEVR.

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Answers to questions published in previous issue

Background: Both age-related macular degeneration (AMD) and inherited retinal disease (IRD) can present with outer retinal atrophy at the macula. Distinguishing between IRD and geographic atrophy (GA) secondary to AMD is important for appropriate management, particularly as disease-specific treatments become available. This study investigates the utility of genetic testing for suspected IRDs in individuals with atypical macular atrophy.

Methods: Twenty-four participants aged over 50, presenting with macular atrophy atypical for AMD, underwent clinical assessments, multimodal retinal imaging and exome-based sequencing covering known IRD genes. Three retinal ophthalmologists reviewed genetic and clinical data to reach a consensus for the underlying cause of macular atrophy and identified a set of features that challenge an AMD diagnosis and suggest a higher likelihood of an IRD.

Results: The panel judged 58% of atypical atrophy cases as likely being an IRD. Of these suspected cases, 57% (33% of the entire cohort) received IRD genetic confirmation (PRPH2, ABCA4 or MT-TL1 [m.3243A>G]-related IRD). The remaining cases were classified as GA (29%) or did not reach consensus on the likely diagnosis (13%). Clinical features aiding in the differentiation of IRD from GA included symptom onset before age 50, family history, distinctive autofluorescence patterns (speckled, reticular or widespread), extensive atrophy and absence of subretinal drusen.

Conclusion: IRD genetic testing is valuable if a positive identification is achieved, but negative results neither rule out IRD nor confirm AMD. Limitations in our ability to robustly differentiate IRD-related atrophy from GA, especially in advanced lesions, need further research to improve diagnostic accuracy.

Background: To characterise stromal curvature and curvature ratios in keratoconus (KCN) using anterior segment OCT, and to evaluate the implications of using single-, two-, and three-surface refractive models for corneal power estimation in ectatic eyes.

Methods: Retrospective observational study. Anterior segment OCT measurements (MS-39, CSO) were analysed. Anterior, stromal, and posterior curvature radii were computed across five concentric zones (2.0-6.0 mm) using a floating best-fit sphere, and curvature ratios were subsequently derived: anterior-to-stromal (ASR), stromal-to-posterior (SPR), and anterior-to-posterior (APR). Corneal power was calculated using one-, two-, and three-surface models. KCN severity was classified according to the Belin ABC grading stage and ASR, SPR, and APR were stratified accordingly.

Results: Data from 944 keratoconic eyes were analysed. Peripheral zones (6.0 mm) exhibited reduced variability in curvature measurement compared to central zones (3.0 mm). Differences between simplified (one- and two-surface) and three-surface power models correlated moderately with increased APR and SPR values. ASR, SPR, and APR all increased progressively with advancing ABC grade.

Conclusion: In advanced keratoconus, three-surface modelling yields different corneal power estimates versus simplified models in KC; prospective outcome studies are needed to assess clinical impact. Stromal curvature and its derived ratios provide novel structural metrics that change with KCN severity. Curvature ratio increase -especially APR and SPR- reflects posterior steepening and anterior-posterior decoupling, with possible implications for staging and surgical planning.