Perifoveal müller cell depletion in a case of macular telangiectasia type 2

Progressive inner retinal neurodegeneration in non-proliferative macular telangiectasia type 2

PURPOSE

Patients with non-proliferative macular telangiectasia type 2 (MacTel) have ganglion cell layer (GCL) and nerve fibre layer (NFL) loss, but it is unclear whether the thinning is progressive. We quantified the change in retinal layer thickness over time in MacTel with and without diabetes.

METHODS

In this retrospective, multicentre, comparative case series, subjects with MacTel with at least two optical coherence tomographic (OCT) scans separated by >9 months OCTs were segmented using the Iowa Reference Algorithms. Mean NFL and GCL thickness was computed across the total area of the early treatment diabetic retinopathy study grid and for the inner temporal region to determine the rate of thinning over time. Mixed effects models were fit to each layer and region to determine retinal thinning for each sublayer over time.

RESULTS

115 patients with MacTel were included; 57 patients (50%) had diabetes and 21 (18%) had a history of carbonic anhydrase inhibitor (CAI) treatment. MacTel patients with and without diabetes had similar rates of thinning. In patients without diabetes and untreated with CAIs, the temporal parafoveal NFL thinned at a rate of -0.25±0.09 µm/year (95% CI [-0.42 to -0.09]; p=0.003). The GCL in subfield 4 thinned faster in the eyes treated with CAI (-1.23±0.21 µm/year; 95% CI [-1.64 to -0.82]) than in untreated eyes (-0.19±0.16; 95% CI [-0.50, 0.11]; p<0.001), an effect also seen for the inner nuclear layer. Progressive outer retinal thinning was observed.

CONCLUSIONS

Patients with MacTel sustain progressive inner retinal neurodegeneration similar to those with diabetes without diabetic retinopathy. Further research is needed to understand the consequences of retinal thinning in MacTel.

Multilayer Retinal Correspondence of the Structural and Vascular Anomalies in Eyes With Early Macular Telangiectasia Type 2

Purpose

To assess the correspondence between interdigitation zone (IZ) reflectivity, ellipsoid zone (EZ) loss, inner retinal layer reflectivity, patterns of capillary dilation, and telangiectasia in eyes with early macular telangiectasia type 2 (MacTel).

Patients and Methods

Twenty-eight eyes of 22 patients with grade 0-2 MacTel (according to the MacTel project classification) and 28 healthy control eyes were included in this study. Multimodal imaging, including optical coherence tomography (OCT) angiography, adaptive optics flood illumination ophthalmoscopy (AO-FIO) and blue light reflectance (BLR), was performed. The EZ, IZ, and outer plexiform layer (OPL) were analyzed on the structural OCT C-scans. The vascular density (VD) was measured on the binarized and skeletonized angiograms of the superficial vascular plexus and deep capillary complex. The vascular diameter index (VDI) was calculated by dividing the binarized VD by the skeletonized VD.

Results

On AO-FIO, cone density in the MacTel zone was significantly lower in MacTel eyes than in controls, even in areas located outside the EZ loss (P < 0.001). A distinctive pattern of IZ reflectivity attenuation extended beyond the area of EZ attenuation. The shape and size of a strong OPL hyper-reflectivity corresponded to the MacTel white area (MacTel zone) seen on BLR. Capillary dilation and rarefaction were colocalized with this area, extending beyond visible telangiectasia. The VDI was higher in MacTel eyes than in controls (P < 0.001).

Conclusions

These findings suggest that in early MacTel eyes, photoreceptor signal alteration, OPL hyper-reflectivity, and capillary dilation, potentially associated with Müller cell dysfunction, precede the EZ loss.

High-throughput ultrastructural analysis of macular telangiectasia type 2

Introduction

Macular Telangiectasia type 2 (MacTel), is an uncommon form of late-onset, slowly-progressive macular degeneration. Associated with regional Müller glial cell loss in the retina and the amino acid serine synthesized by Müller cells, the disease is functionally confined to a central retinal region - the MacTel zone.

Methods

We have used high-throughput multi-resolution electron microscopy techniques, optimized for disease analysis, to study the retinas from two women, mother and daughter, aged 79 and 48 years respectively, suffering from MacTel.

Results

In both eyes, the principal observations made were changes specific to mitochondrial structure both outside and within the MacTel zone in all retinal cell types, with the exception of those in the retinal pigment epithelium (RPE). The lesion areas, which are a hallmark of MacTel, extend from Bruch's membrane and the choriocapillaris, through all depths of the retina, and include cells from the RPE, retinal vascular elements, and extensive hypertrophic basement membrane material. Where the Müller glial cells are lost, we have identified a significant population of microglial cells, exclusively within the Henle fiber layer, which appear to ensheathe the Henle fibers, similar to that seen normally by Müller cells.

Discussion

Since Müller cells synthesize retinal serine, whereas retinal neurons do not, we propose that serine deficiency, required for normal mitochondrial function, may relate to mitochondrial changes that underlie the development of MacTel. With mitochondrial changes occurring retina-wide, the question remains as to why the Müller cells are uniquely susceptible within the MacTel zone.

Unusual morphology of foveal Müller glia in an adult human born pre-term

The fovea of the human retina, a specialization for acute and color vision, features a high concentration of cone photoreceptors. A pit on the inner retinal aspect is created by the centrifugal migration of post-receptoral neurons. Foveal cells are specified early in fetal life, but the fovea reaches its final configuration postnatally. Pre-term birth retards migration resulting in a small pit, a small avascular zone, and nearly continuous inner retinal layers. To explore the involvement of Müller glia, we used serial-section electron microscopic reconstructions to examine the morphology and neural contacts of Müller glia contacting a single foveal cone in a 28-year-old male organ donor born at 28 weeks of gestation. A small non-descript foveal avascular zone contained massed glial processes that included a novel class of 'inner' Müller glia. Similar to classic 'outer' Müller glia that span the retina, inner Müller glia have bodies in the inner nuclear layer (INL). These cells are densely packed with intermediate filaments and insert processes between neurons. Unlike 'outer' Müller glia, 'inner' Müller glia do not reach the external limiting membrane but instead terminate at the outer plexiform layer. One completely reconstructed inner cell ensheathed cone pedicles and a cone-driven circuit of midget bipolar and ganglion cells. Inner Müller glia outnumber foveal cones by 1.8-fold in the outer nuclear layer (221,448 vs. 123,026 cells/mm2). Cell bodies of inner Müller glia outnumber those of outer Müller glia by 1.7-fold in the INL (41,872 vs. 24,631 cells/ mm2). Müller glia account for 95 and 80% of the volume of the foveal floor and Henle fiber layer, respectively. Determining whether inner cells are anomalies solely resulting from retarded lateral migration of inner retinal neurons in pre-term birth requires further research.

New insights on the role of microRNAs in retinal Müller glial cell function

MicroRNAs belong to the family of non-coding RNAs that participate in cell proliferation, cell death and development. The Müller glial cells are the inherent and specific neuroglia cells in the retinal organisation and play significant roles in retinal neuroprotection, organisational maintenance, inflammation and immunity, regeneration, and the occurrence and development of retinal diseases. However, only a few studies report the underlying mechanism of how miRNAs drive the function of Müller glial cells in the development of retinal diseases. This review aims to summarise the roles of miRNAs in retinal Müller glial cell function, including gliogenesis, inflammation and immunity, regeneration, the development of retinal diseases, and retinal development. This review may point out a novel miRNA-based insight into retinal repair and regeneration. MiRNAs in Müller glial cells may be considered a diagnostic and therapeutic target in the process of retinal repair and regeneration.

Müller Glial Cells in the Macula: Their Activation and Cell-Cell Interactions in Age-Related Macular Degeneration

Müller glia, the main glial cell of the retina, are critical for neuronal and vascular homeostasis in the retina. During age-related macular degeneration (AMD) pathogenesis, Müller glial activation, remodeling, and migrations are reported in the areas of retinal pigment epithelial (RPE) degeneration, photoreceptor loss, and choroidal neovascularization (CNV) lesions. Despite this evidence indicating glial activation localized to the regions of AMD pathogenesis, it is unclear whether these glial responses contribute to AMD pathology or occur merely as a bystander effect. In this review, we summarize how Müller glia are affected in AMD retinas and share a prospect on how Müller glial stress might directly contribute to the pathogenesis of AMD. The goal of this review is to highlight the need for future studies investigating the Müller cell's role in AMD. This may lead to a better understanding of AMD pathology, including the conversion from dry to wet AMD, which has no effective therapy currently and may shed light on drug intolerance and resistance to current treatments.

Relevance of multicolor imaging, its component channels, and fundus autofluorescence in describing macular telangiectasia type-2 (MacTel) lesion characteristics

PURPOSE

The aim of the study was to describe imaging characteristics and detection rates of phenotypic features in macular telangiectasia type-2 (MacTel) on multicolor (MC), blue reflectance (BR), green reflectance (GR), infrared reflectance (IR), and fundus autofluorescence (FAF) and to evaluate sensitivity, specificity, and predictive values across modalities.

METHODS

In this monocentric observational study, 282 eyes of 148 patients with MacTel underwent color fundus photograph, MC, BR, GR, IR, FAF, spectral-domain optical coherence tomography (SD-OCT), OCT-angiography (OCT-A), and fundus fluorescein angiography (FFA). Grading was done by two graders qualitatively and quantitatively for the presence of the following prespecified MacTel findings [crystals, right-angle vessels (RAVs), plaques, subretinal neovascularization (SRNV), and MacTel area]. Across each imaging modality, the detection rate of RAVs and SRNV was compared with reference standard OCT-A (RAVs and SRNV) and FFA (SRNV), whereas that of plaques was compared with reference standard SD-OCT.

RESULTS

MC identified overall MacTel characteristics in 92.7% of eyes. Regarding the presence, number, and quadrants of RAVs and the presence and number of crystals, MC and GR had superior detection rates as well as the highest sensitivity and negative predictive value. Retinal plaques were better detected using FAF (97%), followed by MC (88%). In proliferative MacTel, SRNV was identified in 86% and 79% of eyes on MC and IR, respectively. While BR clearly delineated MacTel area in 100% eyes, FAF was able to ascertain a larger area of involvement in proliferative MacTel.

CONCLUSION

The findings demonstrate the ability of MC, its component channels, and FAF to describe MacTel characteristics qualitatively and quantitatively.

Surgical Management of Full-Thickness Macular Holes in Macular Telangiectasia Type 2: A Global Multicenter Study

PURPOSE

To report on macular hole repair in macular telangiectasia type 2 (MacTel2).

DESIGN

Global, multicenter, retrospective case series.

PARTICIPANTS

Patients undergoing surgery for MacTel2-associated full-thickness macular hole (MTMH).

METHODS

Standardized data collection sheet distributed to all surgeons.

MAIN OUTCOME MEASURES

Anatomic closure and visual outcomes of MTMH.

RESULTS

Sixty-three surgeries in 47 patients with MTMH were included from 30 surgeons. Mean age was 68.1 years, with 62% female, 72% White, 21% East or South Asian, 2% African American, and 2% Hispanic or Latino. Procedures included 34 internal limiting membrane (ILM) peeling alone, 22 ILM flaps, 5 autologous retinal transplantations (ARTs), 1 retinotomy, and 1 subretinal bleb. For ILM peeling, preoperative visual acuity (VA) was 0.667 ± 0.423 logarithm of the minimum angle of resolution (logMAR). Minimum hole diameter (MHD) was 305.5 ± 159.4 μm (range, 34-573 μm). Sixteen of 34 ILM peels (47%) resulted in MTMH closure. At postoperative month 6, VA was stable at 0.602 ± 0.516 logMAR (P = 0.65). VA improved by at least 2 lines in 43% and at least 4 lines in 24%. For ILM flaps, preoperative VA was 0.878 ± 0.552 logMAR. MHD was 440.8 ± 175.5 μm (range, 97-697 μm), which was significantly larger than for ILM peels (P < 0.01). Twenty of 22 ILM flaps (90%) resulted in MTMH closure, which was significantly higher than for ILM peels (P < 0.01). At postoperative month 6, VA improved to 0.555 ± 0.405 logMAR (P < 0.05). VA improved by at least 2 lines in 56% and at least 4 lines in 28%. For ARTs, preoperative VA was 1.460 ± 0.391 logMAR. MHD was 390.2 ± 203.7 μm (range, 132-687 μm). All 5 ARTs (100%) resulted in MTMH closure. At postoperative month 6, VA was stable at 1.000 ± 0.246 logMAR (P = 0.08). Visual acuity improved at least 2 lines in 25%.

CONCLUSIONS

Surgical closure of macular holes improved VA in 57% of MTMHs. Internal limiting membrane flaps achieved better anatomic and functional outcomes than ILM peeling alone. Autologous retinal transplantation may be an option for refractory MTMHs.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Unraveling the mysteries of macular telangiectasia 2: the intersection of philanthropy, multimodal imaging and molecular genetics. The 2022 founders lecture of the pan American vitreoretinal society

PURPOSE

Offer a personal perspective on the scientific advances on macular telangiectasia type 2 (MacTel2) since the launch of the MacTel Project in 2005.

DESIGN

Literature review and personal perspective.

METHODS

Critical review of the peer-reviewed literature and personal perspective.

RESULTS

Generous financial support from the Lowy Medical Research Institute laid the foundations of the MacTel Project. MacTel Project investigators used state of the art multimodal retinal imaging and advanced modern biological methods to unravel many of the mysteries surrounding MacTel2. Major accomplishments includes elucidation of the pathogenic role that low serine levels, elevated 1-deoxysphingolipids and other mechanisms induce mitochondrial dysfunction which lead to Müller cell and photoreceptor degeneration; the use of objective measures of retinal structures such as the area of ellipsoid zone disruption as an outcome measure in clinical trials; the demonstration that the ciliary neurotrophic factor slows down retinal degeneration and the development of a new severity scale classification based on multimodal imaging findings.

CONCLUSIONS

MacTel2 is a predominantly metabolic disease characterized by defects in energy metabolism. Despite relatively good visual acuities, MacTel2 patients experience significant visual disability. The Mac Tel Project has been instrumental in advancing MacTel2 knowledge in the past two decades.

Intraretinal pigmented cells in retinal degenerative disease

PURPOSE

Invasion of pigmented cells into the retina occurs in retinal degenerative diseases, such as macular telangiectasia type 2 (MacTel) and retinitis pigmentosa (RP). These intraretinal pigmented cells may be derived from the retinal pigment epithelium (RPE), but differences and similarities between intraretinal pigmented cells and RPE have so far not been well characterised.Clinicopathologic case report.

METHOD

Here, we compared intraretinal pigment cells with RPE cells by immunohistochemistry. Immunohistological stains for classic RPE markers (RPE65, CRALBP and KRT18) and blood vessel markers (lectin and collagen 4) were done on sections from postmortem eye tissue from two MacTel donors, an RP donor and a control donor.

MAIN OUTCOME MEASURES

Presence of specific immunohistochemistry markers on intraretinal pigmented and RPE cells.

RESULTS

We found that intraretinal pigmented cells did not express RPE65 and CRALBP, with a small subset expressing them weakly. However, they all expressed KRT18, which was also present in normal RPE cells. Interestingly, we also found clusters of KRT18-positive cells in the retina that were not pigmented.

CONCLUSIONS

Our findings suggest that RPE cells invading the retina dedifferentiate (losing classic RPE markers) and can be pigmented or unpigmented. Therefore, the number of RPE cells invading the retina in retinal degenerative disease may be underappreciated by funduscopy.

Relation of interdigitation zone changes and right-angle vessels in Macular Telangiectasia Type-2 (MacTel)

BACKGROUND

To study the relation between interdigitation zone (IDZ) and right-angle vessel (RAV) in Macular Telangiectasia Type-2 (MacTel).

METHODS

A total of 43 eyes of 38 patients with presence of definite RAV on colour fundus photograph (Gass and Blodi-only stage-3) were confirmed on multimodal imaging. The relation of IDZ changes and associated ellipsoid zone (EZ) alterations on spectral-domain optical coherence tomography (OCT) with RAV were studied at baseline and these OCT changes were followed up in 15 eyes over a mean of 3.86 years.

RESULTS

A total of 58 RAVs were found in the 43 eyes and 53/58 (91.3%) RAVs were associated with IDZ alterations in 39 eyes. On follow-up, IDZ attenuation progressed to IDZ loss and subsequent EZ attenuation and loss. A pre-existing IDZ loss was associated with subsequent EZ defect (P = 0.002). In 36 eyes that had OCT angiography, eyes with RAV showed deep capillary plexus telangiectasia in all 36 (100%) eyes and 32/36 (89%) eyes showed IDZ changes with or without EZ loss.

CONCLUSIONS

IDZ attenuation and/or loss are associated with RAV and may serve as predictor of EZ loss in MacTel.

Müller cell vulnerability in aging human retina: Implications on photoreceptor cell survival

Müller glial cells (MC) support various metabolic functions of the retinal neurons, and maintain the homeostasis. Oxidative stress is intensified with aging, and in human retina, MC and photoreceptors undergo lipid peroxidation and protein nitration. Information on how MC respond to oxidative stress is vital to understand the fate of aging retinal neurons. This study examined age-related changes in MC of donor human retina (age: 35-98 years; N = 18 donors). Ultrastructural and immunohistochemical observations indicate that MC undergo gliosis and increased lipid peroxidation, and show osmotic changes with advanced aging (>80 years). Photoreceptor cells also undergo oxidative-nitrosative stress with aging, and their synapses also show clear osmotic swelling. MC respond to oxidative stress via proliferation of smooth endoplasmic reticulum in their processes, and increased expression of aquaporin-4 in endfeet and outer retina. In advanced aged retinas (81-98 years), they showed mitochondrial disorganisation, accumulation of lipids and autophagosomes, lipofuscin granules and axonal remnants in phagolysosomes in their inner processes, suggesting a reduced phagocytotic potential in them with aging. Glutamine synthetase expression does not alter until advanced aging, when the retinas show its increased expression in endfeet and Henle fiber layer. It is evident that MC are vulnerable with normal aging and this could be a reason for photoreceptor cell abnormalities reported with aging of the human retina.

Baseline demographic, clinical and multimodal imaging features of young patients with type 2 macular telangiectasia

PURPOSE

Macular telangiectasia (MacTel) type 2 is observed in patients in their 5th-8th decades of life. The clinical and imaging findings in younger patients is unknown in larger cohorts. The study purpose is to report prevalence, baseline clinical and spectral domain optical coherence tomography (SDOCT) findings in young MacTel patients below 40 years.

METHODS

This hospital-based, multicentre, retrospective, cross-sectional study included patients between 2011 and 2023. Retinal photographs from multiple imaging techniques were evaluated to diagnose and stage type 2 MacTel and describe their SDOCT findings. Imaging characteristics were correlated with clinical stages and visual acuity.

RESULTS

Among all MacTel patients seen in hospital, prevalence of young MacTel cases less than age 40 was 1.77% (32/1806; 62 eyes). Youngest participant was 34 years, while mean age was 38.44 ± 1.795 years. Sixteen patients (50%) were diabetics. Perifoveal greying (n = 56, 90%) and perifoveal hyperreflective middle retinal layers (n = 47, 76%) were the most prevalent clinical and SDOCT imaging finding respectively. Less than 10% (n = 6) eyes had proliferative disease. Presence of retinal pigment clumps (RPC) (7% vs. 67%; p = 0.002) coincided with proliferative MacTel. Poor vision was associated with presence of outer retinal layer SDOCT findings like outward bending of inner retinal layers (p = 0.047), RPC (p = 0.007), subfoveal neurosensory detachment (p = 0.048) and subretinal neovascular membrane (p = 0.001).

CONCLUSION

Type 2 MacTel before age 40 is rare, common in women and diabetics, and affects vision in advanced stage. Disease symmetry, comparison with older cases, and longitudinal SDOCT changes in such patients require further study.

Recent advances and prospects for lipid-based nanoparticles as drug carriers in the treatment of human retinal diseases

The delivery of cures for retinal diseases remains problematic. There are four main challenges: passing through multiple barriers of the eye, the delivery to particular retinal cell types, the capability to carry different forms of therapeutic cargo and long-term therapeutic efficacy. Lipid-based nanoparticles (LBNPs) are potent to overcome these challenges due to their unique merits: amphiphilic nanoarchitectures to pass biological barriers, vary modifications with specific affinity to target cell types, flexible capacity for large and mixed types of cargos and slow-release formulations for long-term treatment. We have reviewed the latest research on the applications of LBNPs for treating retinal diseases and categorized them by different payloads. Furthermore, we identified technical barriers and discussed possible future development for LBNPs to expand the therapeutic potential in treating retinal diseases.

Intravitreal Bevacizumab for Choroidal Neovascular Membrane in Macular Telangiectasia Type 2

We report a case of macular telangiectasia type 2 with an associated choroidal neovascular membrane and its treatment. A 54-year-old female presented with a history of gradual vision loss in both eyes. A physical exam showed visual acuity of 20/40 in both eyes and significant metamorphopsia in the right eye. A fundus examination of the right eye was remarkable for right-angled vessels in the juxtafoveal region and subretinal fibrosis temporal to the fovea. A fundus examination of the left eye revealed intraretinal crystals in the juxtafoveal region and right-angled vessels. Optical coherence tomography and angiography confirmed the diagnosis of macular telangiectasia type 2 as well as the presence of a choroidal neovascular membrane in the right eye. The patient was treated with 18 intravitreal injections of anti-vascular endothelial growth factor agent in the right eye for two years, with five to six weeks between each treatment, which resulted in the membrane's stability. Our report suggests that anti-vascular endothelial growth factor therapy via intravitreal injection may be beneficial in treating choroidal neovascular membranes in patients with macular telangiectasia type 2.

Macular and Plasma Xanthophylls Are Higher in Age-related Macular Degeneration than in Normal Aging: Alabama Study on Early Age-related Macular Degeneration 2 Baseline

Purpose

Quantification of retinal xanthophyll carotenoids in eyes with and without age-related macular degeneration (AMD) via macular pigment optical volume (MPOV), a metric for xanthophyll abundance from dual wavelength autofluorescence, plus correlations to plasma levels, could clarify the role of lutein (L) and zeaxanthin (Z) in health, AMD progression, and supplementation strategies.

Design

Cross-sectional observational study (NCT04112667).

Participants

Adults ≥ 60 years from a comprehensive ophthalmology clinic, with healthy maculas or maculas meeting fundus criteria for early or intermediate AMD.

Methods

Macular health and supplement use was assessed by the Age-related Eye Disease Study (AREDS) 9-step scale and self-report, respectively. Macular pigment optical volume was measured from dual wavelength autofluorescence emissions (Spectralis, Heidelberg Engineering). Non-fasting blood draws were assayed for L and Z using high-performance liquid chromatography. Associations among plasma xanthophylls and MPOV were assessed adjusting for age.

Main Outcome Measures

Age-related macular degeneration presence and severity, MPOV in fovea-centered regions of radius 2.0° and 9.0°; plasma L and Z (μM/ml).

Results

Of 809 eyes from 434 persons (89% aged 60-79, 61% female), 53.3% eyes were normal, 28.2% early AMD, and 18.5% intermediate AMD. Macular pigment optical volume 2° and 9° were similar in phakic and pseudophakic eyes, which were combined for analysis. Macular pigment optical volume 2° and 9° and plasma L and Z were higher in early AMD than normal and higher still in intermediate AMD (P < 0.0001). For all participants, higher plasma L was correlated with higher MPOV 2° (Spearman correlation coefficient [Rs] = 0.49; P < 0.0001). These correlations were significant (P < 0.0001) but lower in normal (Rs = 0.37) than early and intermediate AMD (Rs = 0.52 and 0.51, respectively). Results were similar for MPOV 9°. Plasma Z, MPOV 2°, and MPOV 9° followed this same pattern of associations. Associations were not affected by supplement use or smoking status.

Conclusions

A moderate positive correlation of MPOV with plasma L and Z comports with regulated xanthophyll bioavailability and a hypothesized role for xanthophyll transfer in soft drusen biology. An assumption that xanthophylls are low in AMD retina underlies supplementation strategies to reduce progression risk, which our data do not support. Whether higher xanthophyll levels in AMD are due to supplement use cannot be determined in this study.

Co occurrance of Macular Telangiectasia type 2 with hemorrhagic polypoidal choroidal vasculopathy and response to anti-vascular endothelial growth factor

We report the case of a 57-year-old female patient who presented with defective vision in the right eye due to large hemorrhagic pigment epithelial detachment with subretinal hemorrhage near the arcades with scattered retinal pigment epithelium (RPE) alteration at the macula and minimal vitreous hemorrhage inferiorly. The left eye showed right angle perifoveal dipping venule with RPE alteration temporal to the fovea, intraretinal RPE stellate plaque at the macula area. Multimodal imaging features including color fundus photo, red-free photograph, optical coherence tomography (OCT), enhanced depth imaging OCT, fundus fluorescein angiography, indocyanine green angiography, and OCT angiography were studied along with treatment response. One eye showed features of macular telangiectasia Type 2 (MacTel 2) with polypoidal choroidal vasculopathy (PCV) (hemorrhagic type) and the other eye showed features of MacTel 2 with pachychoroid pigment epitheliopathy. This report highlights the hitherto undescribed co-occurrence of MacTel 2 with bilateral pachychoroid and with unilateral hemorrhagic PCV in one eye and its favorable outcome with anti-vascular endothelial growth factor therapy.

Tamoxifen retinopathy

Tamoxifen (TAM) is a selective estrogen receptor modulator that is used in the treatment of breast cancer. As there are estrogen receptors in the retina, retinal pigment epithelium, and choroid, these tissues may also be affected by TAM. We describe the reported effects of TAM on the retina and choroid. Medical databases were searched using relevant keywords and the results were extracted and pooled. The incidence of retinal/choroidal toxicity ranged from 0.9% to 12%. There was a wide range for the time of exposure before the development of TAM retinopathy (3 weeks to 13 years). While functional measurements may be appropriate for assessment of TAM retinopathy, they have not been effective for screening patients. There is no generally accepted screening modality, but serial funduscopy and optical coherence tomography imaging seem to be the most reasonable approach for detecting early TAM-induced retinal toxicity.

Tamoxifen Retinopathy and Macular Telangiectasia Type 2: Similarities and Differences on Multimodal Retinal Imaging

PURPOSE

Tamoxifen-induced retinopathy (TR) and macular telangiectasia type 2 (MacTel) share a highly similar retinal phenotype. In this study, we aimed to evaluate differences and similarities that may point toward underlying mechanisms linking both disease entities.

DESIGN

Retrospective, cross sectional study.

SUBJECTS

Patients diagnosed with MacTel or TR.

METHODS

Patients underwent multimodal retinal imaging, including color fundus photography, spectral-domain OCT, fundus autofluorescence, fluorescein angiography, and OCT angiography (if available). Age, age of onset, best-corrected visual acuity, and bilaterality of changes were evaluated. Patients' eyes were graded for different morphologic characteristics by 4 experienced graders.

MAIN OUTCOME MEASURES

Phenotypical characterization and comparison of frequencies of retinal characteristics of TR and MacTel on multimodal imaging.

RESULTS

Twenty-eight eyes of 14 patients with TR and 118 eyes of 59 patients with MacTel were included. Age, age of onset, and best-corrected visual acuity were similar in both cohorts. All but 1 patient showed bilateral changes. In patients with MacTel, neurodegenerative changes and vascular alterations were equally present, whereas in patients with TR, neurodegenerative changes usually prevailed. Predilection sites within the central retina differed between the 2 diseases: most findings in patients with TR were limited to the foveal center, whereas changes in patients with MacTel were present throughout a slightly larger region ("MacTel area"), with an epicenter temporal to the foveal center. Distinct morphologic features included the distribution of retinal crystals, the size and position of ellipsoid zone breaks, and the presence of hyperreflective changes on OCT images. Focal hyperpigmentation and neovascular membranes were only present in eyes with MacTel.

CONCLUSIONS

Macular telangiectasia and TR share a highly similar retinal phenotype, especially in early disease stages. Subtle differences on multimodal retinal images may help distinguish between these 2 disease entities. Our findings indicate the involvement of Müller cells in both diseases, which may explain the observed phenotypic characteristics and similarities.

OUTER FOVEAL DEFECTS IN TYPE-2 MACULAR TELANGIECTASIA

PURPOSE

To report characteristics of outer foveal defects (OFDs) in type-2 macular telangiectasia (MacTel) on spectral domain optical coherence tomography.

METHODS

This was a single-center observational study. From a registry of 745 patients with MacTel, patients with OFDs were characterized. All patients underwent multimodal imaging including color fundus photography, confocal blue reflectance, fundus autofluorescence, and spectral domain optical coherence tomography. Staging of eyes was done using the Gass and Blodi classification. Spectral domain optical coherence tomography characteristics in the central 1 mm of the macula in eyes with OFD are reported.

RESULTS

Outer foveal defect was observed in 21 eyes of 15/745 (2%) patients with MacTel. These defects were bilateral in 6/15 (40%) patients and seen in stage 2 MacTel eyes. In order of prevalence, foveal parameters seen in OFD included hyper-reflective dots in outer retina in 19/21 (90%), ellipsoid zone loss in 18/21 (86%) eyes, interdigitation zone loss in 17/21 (81%) eyes, outer retinal hyporeflective cavitation in 14 (67%) eyes, hyporeflective cavitation at foveal pit in 8 (38%) eyes, and loss of external limiting membrane in 1 (5%) eye. The mean baseline length of the foveal ellipsoid zone loss was 240.17 ± 117.249 µm. The mean baseline central subfield thickness was 155.43 ± 17.215 µm. A total of 8/11 eyes (73%) showed an increase in size of OFD on follow-up.

CONCLUSION

Outer foveal defect in MacTel eyes is characterized predominantly by foveal loss of ellipsoid zone and interdigitation zone with relative preservation of external limiting membrane.

Non-vasogenic cystoid maculopathies

Besides cystoid macular edema due to a blood-retinal barrier breakdown, another type of macular cystoid spaces referred to as non-vasogenic cystoid maculopathies (NVCM) may be detected on optical coherence tomography but not on fluorescein angiography. Various causes may disrupt retinal cell cohesion or impair retinal pigment epithelium (RPE) and Müller cell functions in the maintenance of retinal dehydration, resulting in cystoid spaces formation. Tractional causes include vitreomacular traction, epiretinal membranes and myopic foveoschisis. Surgical treatment does not always allow cystoid space resorption. In inherited retinal dystrophies, cystoid spaces may be part of the disease as in X-linked retinoschisis or enhanced S-cone syndrome, or occur occasionally as in bestrophinopathies, retinitis pigmentosa and allied diseases, congenital microphthalmia, choroideremia, gyrate atrophy and Bietti crystalline dystrophy. In macular telangiectasia type 2, cystoid spaces and cavitations do not depend on the fluid leakage from telangiectasia. Various causes affecting RPE function may result in NVCM such as chronic central serous chorioretinopathy and paraneoplastic syndromes. Non-exudative age macular degeneration may also be complicated by intraretinal cystoid spaces in the absence of fluorescein leakage. In these diseases, cystoid spaces occur in a context of retinal cell loss. Various causes of optic atrophy, including open-angle glaucoma, result in microcystoid spaces in the inner nuclear layer due to a retrograde transsynaptic degeneration. Lastly, drug toxicity may also induce cystoid maculopathy. Identifying NVCM on multimodal imaging, including fluorescein angiography if needed, allows guiding the diagnosis of the causative disease and choosing adequate treatment when available.

Use of OCT Angiography to Diagnose and Manage Atypical Presentations of Macular Telangiectasia Type 2

Macular telangiectasia Type 2 (MacTel) is a bilateral acquired retinal disease characterized by both vascular changes and atrophy of the retina. The purpose of this case series is to highlight the use of optical coherence tomography angiography (OCTA) as a non-invasive imaging modality to distinguish atypical MacTel from other macular conditions with similar presentations. We performed a retrospective review of patients referred to our academic retinal practice with unconfirmed or misdiagnosed MacTel between July 2017 and July 2021. Patients' OCTA imaging findings were reviewed to guide the appropriate diagnosis and management of atypical MacTel. Fifteen eyes from eight patients were included in this study. Six patients were referred with previous diagnoses of either full-thickness macular hole, lamellar hole, vitreomacular traction (VMT), postoperative cystoid macular edema (CME), or diabetic macular edema (DME). Two patients were referred to us to confirm the diagnosis of MacTel. OCTA revealed telangiectatic vessels in the temporal parafovea of all 15 eyes. OCTA also highlighted previously undiagnosed subretinal neovascularization (SRNV) in seven eyes. OCTA imaging is a valuable imaging modality to distinguish MacTel from other macular conditions, whose treatment courses vary substantially. Due to its ease of use, it holds immense potential in the future as treatments for non-proliferative MacTel emerge.

Distribution of macular pigments in macular telangiectasia type 2 and correlation with optical coherence tomography characteristics and visual acuity

Background

To estimate macular pigment values in macular telangiectasia (MacTel) Type 2 in comparison with healthy subjects in the South Indian population across different spatial profiles and to quantify the regional differences of macular pigment optical density (MPOD) in MacTel Type 2.

Methods

In this prospective cross-sectional study, healthy controls and patients diagnosed with various stages of MacTel Type 2 underwent MPOD measurement using dual-wavelength autofluorescence technique with Spectralis HRA + OCT.

Results

Sixty eyes of 31 healthy subjects and 41 eyes of 22 MacTel type 2 patients were included. We found an overall decrease in MPOD values in MacTel type 2 patients (-0.109, -0.11, -0.001) in comparison with healthy subjects (0.38, 0.23, 0.06) at 1°, 2° & 6° foveal eccentricities (P < 0.001). In various stages of MacTel type 2, the mean MPOD was found to be higher in the peripheral region compared to the central region. We found a significantly lower mean MPOD in the central region in association with specific optical coherence tomography (OCT) parameters like inner retinal cavities (P = 0.035) and ellipsoid zone disruption (P = 0.034).

Conclusions

In MacTel type 2, MPOD distribution varies in different spatial profiles with higher MPOD levels in the peripheral region compared to the central region. The macular pigment levels are associated with inner retinal cavities and ellipsoid zone disruption seen on OCT.

Visual acuity after cataract surgery in Macular Telangiectasia Type 2 Stage 3 to 5

BACKGROUND

The purpose of this study was to evaluate visual acuity after cataract surgery in eyes with Macular Telangiectasia (MacTel) Type 2.

METHODS

Single-center retrospective cohort study of patients with MacTel Type 2 who underwent cataract surgery and were managed at the same institution. Patients underwent pre-operative assessment by a retinal specialist with examination and optical coherence tomography (OCT) at the same institution. The main outcome measure was the post-operative change in best corrected visual acuity (BCVA). Secondary study outcomes were achieving post-operative BCVA better than Snellen acuity of 20/40 and time to BCVA loss by two lines or more (10 or more ETDRS letters).

RESULTS

A total of 20 eyes (11 patients) underwent cataract surgery and were followed for a median of 25.5 months (IQR 17.5-44.2 months). The median post-operative BCVA improvement was 10.5 letters (IQR 3.50-20.25). Nuclear sclerosis severity [β = 8.99 (95% CI 3.35, 14.6), p = 0.00177] was associated with post-operative change in BCVA and central foveal ellipsoid zone (EZ) breaks [OR 1.33 × 10^-9 (95% CI 5.12 × 10^-10-3.43 × 10^-9), p < 0.001] on OCT was inversely correlated with post-operative BCVA > 20/40 using a multivariate generalized linear model. Central foveal EZ breaks [HR 1.77 × 10⁹ (95% CI 3.86 × 10⁸, 8.11 × 10⁹), p < 0.001] and MacTel Type 2 disease stage [HR 2.83, (95% CI 1.12, 7.12), p = 0.027] were independently associated with shorter time to vision loss of two lines or more in a multivariate Cox regression model.

CONCLUSIONS

Visual acuity significant improved after cataract surgery in eyes with MacTel Type 2 regardless of disease severity. The presence of central foveal EZ breaks may predict poorer post-operative visual acuity and subsequent vision loss from disease progression.

Metabolism Dysregulation in Retinal Diseases and Related Therapies

The human retina, which is part of the central nervous system, has exceptionally high energy demands that requires an efficient metabolism of glucose, lipids, and amino acids. Dysregulation of retinal metabolism disrupts local energy supply and redox balance, contributing to the pathogenesis of diverse retinal diseases, including age-related macular degeneration, diabetic retinopathy, inherited retinal degenerations, and Macular Telangiectasia. A better understanding of the contribution of dysregulated metabolism to retinal diseases may provide better therapeutic targets than we currently have.

Specific ablation of Hippo signalling component Yap1 in retinal progenitors and Müller cells results in late onset retinal degeneration

Yes-associated protein (YAP) is a major component of the Hippo pathway involved in development, growth, repair and homeostasis. Nonsense YAP1 mutations in humans result in autosomal dominant coloboma. Here, we generated a conditional knockout mouse model in which Yap1 was specifically deleted in embryonic retinal progenitor cells (RPCs) and in mature Müller cells using a Chx10-Cre driver. Our data demonstrated that the conditional ablation of Yap1 in embryonic RPCs does not prevent normal retinal development and caused no gross changes in retinal structure during embryonic and early postnatal life. Nevertheless, Yap1 deficient in retinal Müller cells in adult mice leads to impaired visual responses and extensive late-onset retinal degeneration, characterized by reduced cell number in all retinal layers. Immunofluorescence data further revealed the degeneration and death of rod and cone photoreceptors, bipolar cells, horizontal cells, amacrine cells and ganglion cells to varying degrees in aged knockout mice. Moreover, alteration of glial homeostasis and reactive gliosis were also observed. Finally, cell proliferation and TUNEL assay revealed that the broad retinal degeneration is mainly caused by enhanced apoptosis in late period. Together, this work uncovers that YAP is essential for the normal vision and retinal maintenance, highlighting the crucial role of YAP in retinal function and homeostasis.

Spectral domain OCT features in type 2 macular telangiectasia (type 2 MacTel): its relevance with clinical staging and visual acuity

BACKGROUND

To report spectral domain optical coherence tomography (SDOCT) imaging findings in type 2 macular telangiectasia (MacTel) and correlate them with clinical stages and visual acuity.

METHODS

This retrospective, cross-sectional study included type 2 MacTel cases who underwent SDOCT imaging with Spectralis machine. Macular SDOCT images were analysed. Imaging features were tested for correlation with different clinicals stages and visual acuity.

RESULTS

212 eyes of 108 type 2 MacTel patients were included. Hyperreflective middle retinal layer (87%) was the most frequently detected abnormality. This was followed by inner retinal cavities (49%), outward bending of inner retinal layers (35%), retinal pigment clumps (35%) and foveal contour irregularity (31%). Hyperreflective middle retinal layers (p < 0.001), inner (p = 0.032) and outer retinal (p = 0.002) cavities and internal limiting membrane drape (p = 0.031) were associated with poor vision in non-proliferative group and presence of retinal pigment clumps (p = 0.002), subretinal fluid (p = 0.037) and foveal contour irregularity (p < 0.001) were associated with poor vision in proliferative group.

CONCLUSION

The described SDOCT features are practical for the diagnosis and staging in type 2 MacTel. Presence of hyperreflective middle retinal layers, hyporeflective inner and outer retinal cavities and internal limiting membrane drape were associated with poor vision in the non-proliferative group while retinal pigment clumps and subretinal neovascular membrane were associated with proliferative group and poor vision. Further long-term studies are required to describe the progressive and sequential changes on SDOCT.

OCT-angiography for diagnosis and response to treatment of subretinal neovascularization secondary to idiopathic macular telangiectasia type 2

Idiopathic macular telangiectasia type 2 (MacTel 2) is a slow and progressive bilateral condition that affects middle-aged and elderly individuals. Vision loss is generally mild and occurs over the course of many years. The development of sub-retinal neovascularisation (SRNV) can occur late in the disease process, and lead to more dramatic vision loss. A report is presented of 2 cases of MacTel 2 in which optical coherence tomography angiography (OCTA) was essential for the diagnosis of secondary SRNV. The commercially available OCTA Cirrus AngioPlex 5000 platform (Zeiss, Jena, Germany) was used. Subretinal neovascularization was detectable in both cases in OCTA at the level of the deep capillary plexus and the avascular layer. OCTA also allowed us to monitor disease progression and monitor response to anti-VEGF therapy.

Anti-retinal IgG antibodies in patients with early and advanced type 2 macular telangiectasia

Type 2 idiopathic macular telangiectasia (MacTel-2) is a progressive adult-onset macular disease associated with bilateral perifoveal vascular changes, Muller cell degeneration and increased blood-retinal barrier permeability. The pathophysiological mechanisms of MacTel-2 remain unclear, however it was previously reported that anti-retinal antibodies in MacTel-2 patients was a significant feature of the disease. In this study, we aimed to compare the prevalence of anti-retinal antibodies in patients MacTel-2, healthy controls and patients with other retinal diseases. MacTel-2 patients diagnosed with multimodal imaging were enrolled and their disease severities were graded using spectral-domain optical coherence tomography. For comparison, patients with age-related macular degeneration (AMD), inherited retinal diseases (IRDs) or no retinal disease (healthy controls) were recruited as controls. Blood serum samples were screened for immunoglobulin G anti-retinal antibodies by western blotting, followed by densitometry analysis. Odds ratios (OR) with 95% confidence intervals (CI) were calculated and p < 0.05 considered statistically significant. Overall, anti-retinal antibody-positive cases were older (64 ± 15 vs 53 ± 17 years, p < 0.001) and females were more likely to develop anti-retinal antibodies (OR: 2.41, CI: 1.12-5.18). The frequency of anti-retinal antibody detection in MacTel-2 patients (n = 42, 36%) was not significantly different from healthy controls (n = 52, 25%) or IRDs patients (n = 18, 25%) and the majority of MacTel-2 patients had no anti-retinal antibodies. In contrast, the frequency of anti-retinal antibody detection was significantly higher in patients with AMD (n = 15, 73%, p < 0.001). The lack of a greater anti-retinal antibody frequency or specificity in the MacTel-2 cohort suggests that antibody mediated immunological mechanisms may play a less significant role in MacTel-2 disease pathogenesis.

Clinical Features of Untreated Type 2 Macular Telangiectasia and Efficacy of Anti-Vascular Endothelial Growth Factor Therapy in Macular Neovascularization

Objectives:

To compare best corrected visual acuity (BCVA), central macular thickness (CMT), and central choroidal thickness (CCT) in patients with type 2 macular telangiectasia (MacTel 2) and a control group and to evaluate the efficacy of intravitreal anti-vascular endothelial growth factor (anti-VEGF) treatment in MacTel 2 patients with macular neovascularization (MNV).

Materials and Methods:

We conducted a retrospective chart review of consecutive MacTel 2 patients who underwent a full ophthalmologic examination including BCVA and dilated fundus examination with slit-lamp biomicroscopy, fluorescein angiography, and optical coherence tomography imaging at baseline and follow-up visits. BCVA, CMT, and CCT were compared between all identified patients (n=26) and a control group (n=30). A subgroup analysis was performed among eyes with MNV (n=7) before and after treatment.

Results:

CMT and CCT were significantly lower in the MacTel 2 group compared to the control group. Forty-one treatment-naive eyes without MNV proliferation showed no significant change in BCVA, CMT, or CCT during follow-up. Eight eyes of 7 MacTel 2 patients developed MNV during follow-up. All of the patients were treated with intravitreal anti-VEGF.

Conclusion:

It is important to closely follow MacTel 2 patients for MNV development. To avoid adverse effects, we prefer to monitor patients who have not yet developed MNV. Patients with proliferative MacTel 2 with decreasing visual function may benefit from intravitreal anti-VEGF treatment.

Imaging endpoints for clinical trials in MacTel type 2

INTRODUCTION

Macular Telangiectasia type 2 (MacTel) is a bilateral neurodegenerative disease associated with dysfunction in the serine and lipid metabolism resulting in loss of Muller cells and photoreceptors. Typical structural changes include vascular abnormalities, loss of retinal transparency, redistribution of macular pigment and thinning of the central retina with photoreceptor loss. The presence and extent of photoreceptor loss, as visible on Optical Coherence Tomography (OCT) ("disease severity scale"), correlate with functional loss and the limitation of photoreceptor loss appears to be the most promising therapeutic approach. Ongoing clinical trials of ciliary neurotrophic factor (CNTF) implants for the treatment of MacTel are using this outcome to evaluate efficacy. An ideal outcome measure provides the ability to quantify the extent of the disease progression with precision and reproducibility.

METHODS

This review describes the changes and findings on different imaging techniques including fluorescein- and OCT angiography, blue light reflectance, 1- and 2-wavelength autofluorescence and OCT.

RESULTS

The possibilities of objective quantification of the severity of MacTel and correlation with functional characteristics such as best-corrected visual acuity (BCVA) and microperimetry and their applications as quantitative imaging endpoints for clinical treatment trials are discussed. OCT and especially en face OCT could be demonstrated as precise and reproducible methods to quantify the area of photoreceptor loss, which correlated highly significantly with functional loss in microperimetry.

CONCLUSION

The analysis of the area of photoreceptor loss on en face OCT is the most reliable imaging endpoint for treatment trials in MacTel. This method is already being used in ongoing randomized trials.

Macular Telangiectasia type 2: multimodal assessment of retinal function and microstructure

PURPOSE

To assess the impact of neurodegenerative morphologic alterations due to macular telangiectasia type 2 (MacTel) on microperimetry (MP) and multifocal electroretinography (mfERG).

METHODS

Thirty-five eyes of 18 patients with MacTel were examined using spectral domain optical coherence tomography (SD-OCT), fundus autofluorescence (FAF), mfERG and MP. Software was used to match SD-OCT B-scans with the corresponding retinal sensitivity map and multifocal electroretinograms (mfERGs), thus enabling direct structure/function correlation.

RESULTS

Loss of the ellipsoid zone (EZ) had the strongest negative association with retinal sensitivity (16.77 dB versus 4.58 dB, adj. p < 0.001) of all parameters examined, and a limited negative effect on mfERGs (0.32 SD versus -1.97 SD adj. p = 0.121). Ellipsoid zone (EZ) irregularity was associated with reduced MP values but preserved mfERGs. There was a significant association between areas of inner retinal hyporeflectivity and loss of MP sensitivity (adj. p < 0.001) but the reduction in sensitivity was less than in locations with EZ loss. Areas of mfERG abnormality showed similar sensitivity loss with either inner retinal hyporeflectivity or EZ loss (adj. p = 0.063). In areas with EZ loss alone, preservation of the external limiting membrane (ELM) was associated with higher MP values than in areas with additional ELM loss; the integrity of the ELM alone was not associated with changes either in MP or mfERG. Increased FAF was observed in 51% of eyes, mixed/reduced FAF in 40%, and no abnormality was detected in 9% of eyes.

CONCLUSION

The data suggest both MP and mfERG to be useful non-invasive modalities for detecting localised macular dysfunction in MacTel. The findings suggest a different sensitivity of the two modalities to inner and outer retinal changes in macular function and are therefore complementary.

Lutein and Zeaxanthin Distribution in the Healthy Macula and Its Association with Various Demographic Factors Examined in Pseudophakic Eyes

The macular pigment consisting of lutein (L) and zeaxanthin (Z) protects photoreceptors via its antioxidative and barrier activities. This study aimed to determine L and Z distribution in the healthy macula and their association with various demographic factors. Macular pigment optical density (MPOD) was measured using fundus autofluorescence spectroscopy in 352 pseudophakic eyes with no fundus diseases. Pseudophakia was chosen to avoid the influence of cataract in the measurement of fundus autofluorescence. The mean patient age was 72.3 ± 8.6 years. MPOD was analyzed separately in three zones, i.e., A: a central area within a radius of 0.5°, mainly containing Z; B: a ring area with radii from 0.5° to 1.3°, containing Z and L; C: a ring area with radii from 1.3° to 9°, containing L. Multivariate analyses were performed with MPOD as the dependent variable and sex, supplement intake, smoking habits, glaucoma, diabetes, age, body mass index (BMI), skin carotenoid levels, retinal thickness, retinal volume, axial length as the independent variables. The mean total MPOD volume within 9° eccentricity was 20,121 ± 6293. Age was positively associated with MPOD in all zones. Supplement and BMI were positively and negatively associated with MPOD in zones B and C. Smoking was negatively associated with MPOD in zone A. This study revealed the standard MP values of aged Japanese, which resulted to be higher than the previously reported values in other races. Age was found to have a positive association with MP values. L in the outer foveola was affected by BMI and supplements, but Z in the foveola was not. The amount of Z in the Müller cell cone may not be changed easily by factors such as hunger and satiety in the context of preservation of homeostasis in the human body, but tobacco had a negative effect on Z.

Early-stage macular telangiectasia type 2 vascular abnormalities are associated with interdigitation zone disruption

PURPOSE

To investigate the relationship between disruption in different photoreceptor layers and deep capillary plexus (DCP) telangiectasias in eyes with macular telangiectasia type 2 (MacTel).

METHODS

35 eyes (21 patients) with MacTel imaged with optical coherence tomography angiography (OCTA) were included. Circumscribed areas of DCP telangiectasia were traced from OCTA slabs and the corresponding spectral-domain OCT (SD-OCT) slabs were used to visualize the photoreceptor layer interdigitation zone (IZ) and ellipsoid zone (EZ). IZ attenuation, IZ loss, and EZ loss were graded by reviewing en face SD-OCT slabs for hypo-reflective areas and confirming their status on cross-sectional views. Total area of photoreceptor disruption and overlap with DCP telangiectasia were evaluated with respect to OCT-based MacTel stage. Longitudinal changes were evaluated in a subset of patients with follow-up imaging.

RESULTS

Overlap of DCP telangiectasia with IZ attenuation significantly decreased with MacTel severity, while overlap with IZ and EZ loss significantly increased. Overlap with IZ loss peaked in moderate MacTel (Stages 3-5). Longitudinal imaging showed that new EZ loss at 6 months was largely predicted by baseline IZ loss.

CONCLUSIONS

Worsening MacTel severity is characterized by greater overlap between DCP telangiectasia and zones of increasing severity of photoreceptor disruption, with EZ loss enlarging over time within areas of preexisting IZ disruption. We suggest that IZ disruption may indicate early photoreceptor dysfunction that eventually progresses to EZ loss, with IZ loss being a more reliable metric than IZ attenuation. Additional studies will be necessary to further explore long-term photoreceptor changes and evaluate their relationship with visual function in MacTel.

The "Neuro-Glial-Vascular" Unit: The Role of Glia in Neurovascular Unit Formation and Dysfunction

The neurovascular unit (NVU) is a complex multi-cellular structure consisting of endothelial cells (ECs), neurons, glia, smooth muscle cells (SMCs), and pericytes. Each component is closely linked to each other, establishing a structural and functional unit, regulating central nervous system (CNS) blood flow and energy metabolism as well as forming the blood-brain barrier (BBB) and inner blood-retina barrier (BRB). As the name suggests, the “neuro” and “vascular” components of the NVU are well recognized and neurovascular coupling is the key function of the NVU. However, the NVU consists of multiple cell types and its functionality goes beyond the resulting neurovascular coupling, with cross-component links of signaling, metabolism, and homeostasis. Within the NVU, glia cells have gained increased attention and it is increasingly clear that they fulfill various multi-level functions in the NVU. Glial dysfunctions were shown to precede neuronal and vascular pathologies suggesting central roles for glia in NVU functionality and pathogenesis of disease. In this review, we take a “glio-centric” view on NVU development and function in the retina and brain, how these change in disease, and how advancing experimental techniques will help us address unanswered questions.

Two years outcomes of treating full-thickness macula hole associated with idiopathic macular telangiectasia type 2 by internal limiting membrane inverted flap technique: Case reports

RATIONAL

Macular telangiectasia (MacTel) is an uncommon ocular disorder that can lead to legal blindness. MacTel type 2 is characterized by a bilateral loss of macular transparency, the presence of white crystals on the retina, aberrant blood vessel growth, and neurodegeneration of the macula. Full-thickness macular holes (FTMHs) are a prominent cause of vision reduction in MacTel type 2, and the standard care for an FTMH is pars plana vitrectomy (PPV) to restore the FTMH and best-corrected visual acuity (BCVA). However, surgical outcomes in previous reports were not good, with a lack of closure or a reopening of the FTMH, compared with those with an idiopathic FTMH. Thus, this study aimed to determine the surgical outcomes of PPV with the inverted ILM flap technique for the treatment of FTMHs with a 2-year postoperative follow-up in three patients with MacTel type 2.

PATIENT CONCERNS

This study involved 3 patients who had been diagnosed with MacTel type 2 at a local eye clinic and who was subsequently referred to our department for a more detailed examination.

DIAGNOSES

Three patients were diagnosed with MacTel type 2 using dilated ophthalmoscopy, fluorescein angiography, and optical coherence tomography (OCT) in both eyes. A FTMH was developed and visual acuity decreased during follow-up period in all of the patients.

INTERVENTIONS

Each patient underwent PPV in 1 eye using the inverted ILM-flap technique, gas tamponade, and prone positioning.

OUTCOMES

The FTMH was successfully closed in the 3 cases after the surgery. OCT showed that the FTMH remained closed at the last follow-up examination in 2 patients and vision improved to 20/20 and 20/25. In the other patient, the hole was closed temporarily after surgery, but was reopened at 6 months. The vision had improved to 20/60 until the hole was reopened, and it was 20/100 at the final follow-up examination.

LESSONS

Although only 3 patients were examined, the inverted ILM-flap technique may be an effective and safe method to close an FTMH in patients with MacTel type 2. However, the surgery cannot prevent the reopening of the hole when the retinal atrophy progresses.

The preproliferative stage in type 2 macular telangiectasia (MacTel type 2)

PURPOSE

To study clinical and imaging features of various stages of macular telangiectasia (MacTel type 2).

METHODS

In this retrospective study, cases of MacTel type 2 with fluorescein angiography (FA), optical coherence tomography (OCT) and OCT-angiography (OCTA) imaging were included. Based on angiographic perifoveal fluorescence, two groups were formed: group 1: diffuse hyperfluoroscence and group 2: diffuse + focal hyperfluoroscence. Later, based on OCT features, group 2 was subdivided into group 2A: without SRNVM and group 2B: with SRNVM. Clinical, FA, OCT and OCTA features were analysed. Eyes showing conversion to the proliferative stage at final visit were noted.

RESULTS

Ninety-four eyes of 48 patients were included. Group 1 (n = 28) showed diffuse perifoveal hyperfluoroscence, hyperreflective middle retinal layers, absent SRNVM (p = 0.006) on OCT and dilated perifoveal capillaries in deep capillary plexus (DCP) on OCTA. Group 2A (n = 40) showed diffuse + focal perifoveal hyperfluoroscence, hyperreflective middle retinal layers (p = 0.001), hyporeflective outer retina cavities (p = 0.021), absent SRNVM with dilated and bunching perifoveal capillaries (p = 0.004) in DCP. Group 2B (n = 26) showed late diffuse + focal perifoveal hyperfluoroscence, foveal contour irregularity (p = 0.002), retinal pigment clumps (p = 0.015) and SRNVM on OCT with bunching of capillaries in DCP and vessels in outer retina (p = 0.002). Five eyes showed conversion to group 2B at final visit.

CONCLUSION

There exists a distinct disease stage called "preproliferative" MacTel type 2 showing clinical features of non-proliferative disease, diffuse + focal perifoveal hyperfluoroscence on FA, absent SRNVM on OCT and bunching perifoveal capillaries in DCP on OCTA. Its identification is important for suspecting proliferative disease, planning management and follow-up visit accordingly.

Microvascular changes precede visible neurodegeneration in fellow eyes of patients with asymmetric type 2 macular telangiectasia

IMPORTANCE

Macular telangiectasia type 2 (MacTel) is bilateral disease with characteristic alterations of the macular capillary network along with decreased macular pigment in the parafoveal area. The purpose of this study was to highlight that some eyes show microvascular changes which precede any visible neuronal changes on spectral-domain optical coherence tomography (SD-OCT).

METHODS

This observational study was conducted at a tertiary eye institute. From a registry of 630 patients with MacTel, we identified 4 patients with typical MacTel characteristics in only one eye with no visible changes on colour photographs or SD-OCT in the fellow eye. These 4 patients had findings of MacTel documented by colour fundus photograph, multicolour imaging (MCI), fundus autofluorescence (FAF), confocal blue reflectance (CBR), SD-OCT, and OCT-Angiography (OCT-A) in one eye. OCT-A was performed in MacTel patients using the High-resolution Spectralis (Heidelberg Engineering) module with a full-spectrum probabilistic approach and we employed a 30° x 15° (~8.8 mm × 4.4 mm) scan pattern covering the macula. MCI was done at the end so as to avoid fading the confocal blue reflectance hyperreflectivity seen in MacTel.

RESULTS

On OCT-A, all 4 fellow eyes showed telangiectasia and foveal avascular zone changes in the superficial and deep capillary plexuses with no changes on SD-OCT. None of the eyes showed typically increased reflectance on CBR around the foveal area.

CONCLUSION

These findings show that microvascular changes on OCT-A may occur before visible neurodegenerative changes on OCT, providing new insights into the course of the disease.

Müller cells and astrocytes in tractional macular disorders

Tractional deformations of the fovea mainly arise from an anomalous posterior vitreous detachment and contraction of epiretinal membranes, and also occur in eyes with cystoid macular edema or high myopia. Traction to the fovea may cause partial- and full-thickness macular defects. Partial-thickness defects are foveal pseudocysts, macular pseudoholes, and tractional, degenerative, and outer lamellar holes. The morphology of the foveal defects can be partly explained by the shape of Müller cells and the location of tissue layer interfaces of low mechanical stability. Because Müller cells and astrocytes provide the structural scaffold of the fovea, they are active players in mediating tractional alterations of the fovea, in protecting the fovea from such alterations, and in the regeneration of the foveal structure. Tractional and degenerative lamellar holes are characterized by a disruption of the Müller cell cone in the foveola. After detachment or disruption of the cone, Müller cells of the foveal walls support the structural stability of the foveal center. After tractional elevation of the inner layers of the foveal walls, possibly resulting in foveoschisis, Müller cells transmit tractional forces from the inner to the outer retina leading to central photoreceptor layer defects and a detachment of the neuroretina from the retinal pigment epithelium. This mechanism plays a role in the widening of outer lameller and full-thickness macular holes, and contributes to visual impairment in eyes with macular disorders caused by conractile epiretinal membranes. Müller cells of the foveal walls may seal holes in the outer fovea and mediate the regeneration of the fovea after closure of full-thickness holes. The latter is mediated by the formation of temporary glial scars whereas persistent glial scars impede regular foveal regeneration. Further research is required to improve our understanding of the roles of glial cells in the pathogenesis and healing of tractional macular disorders.

Retinal toxicities of systemic anticancer drugs

Newer anticancer drugs have revolutionized cancer treatment in the last decade, but conventional chemotherapy still occupies a central position in many cancers, with combination therapy and newer methods of delivery increasing their efficacy while minimizing toxicities. We discuss the retinal toxicities of anticancer drugs with an emphasis on the mechanism of toxicity. Uveitis is seen with the use of v-raf murine sarcoma viral oncogene homolog B editing anticancer inhibitors as well as immunotherapy. Most of the cases are mild with only anterior uveitis, but severe cases of posterior uveitis, panuveitis, and Vogt-Koyanagi-Harada-like disease may also occur. In the retina, a transient neurosensory detachment is observed in almost all patients on mitogen-activated protein kinase kinase (MEK) inhibitors. Microvasculopathy is often seen with interferon α, but vascular occlusion is a more serious toxicity caused by interferon α and MEK inhibitors. Crystalline retinopathy with or without macular edema may occur with tamoxifen; however, even asymptomatic patients may develop cavitatory spaces seen on optical coherence tomography. A unique macular edema with angiographic silence is characteristic of taxanes. Delayed dark adaptation has been observed with fenretinide. Interestingly, this drug is finding potential application in Stargardt disease and age-related macular degeneration.

Effect of selectively knocking down key metabolic genes in Müller glia on photoreceptor health

The importance of Müller glia for retinal homeostasis suggests that they may have vulnerabilities that lead to retinal disease. Here, we studied the effect of selectively knocking down key metabolic genes in Müller glia on photoreceptor health. Immunostaining indicated that murine Müller glia expressed insulin receptor (IR), hexokinase 2 (HK2) and phosphoglycerate dehydrogenase (PHGDH) but very little pyruvate dehydrogenase E1 alpha 1 (PDH-E1α) and lactate dehydrogenase A (LDH-A). We crossed Müller glial cell-CreER (MC-CreER) mice with transgenic mice carrying a floxed IR, HK2, PDH-E1α, LDH-A, or PHGDH gene to study the effect of selectively knocking down key metabolic genes in Müller glia cells on retinal health. Selectively knocking down IR, HK2, or PHGDH led to photoreceptor degeneration and reduced electroretinographic responses. Supplementing exogenous l-serine prevented photoreceptor degeneration and improved retinal function in MC-PHGDH knockdown mice. We unexpectedly found that the levels of retinal serine and glycine were not reduced but, on the contrary, highly increased in MC-PHGDH knockdown mice. Moreover, dietary serine supplementation, while rescuing the retinal phenotypes caused by genetic deletion of PHGDH in Müller glial cells, restored retinal serine and glycine homeostasis probably through regulation of serine transport. No retinal abnormalities were observed in MC-CreER mice crossed with PDH-E1α- or LDH-A-floxed mice despite Cre expression. Our findings suggest that Müller glia do not complete glycolysis but use glucose to produce serine to support photoreceptors. Supplementation with exogenous serine is effective in preventing photoreceptor degeneration caused by PHGDH deficiency in Müller glia.

MICROSTRUCTURAL CHANGES IN CYSTOID MACULAR EDEMA IN RETINITIS PIGMENTOSA AFTER INTRAVITREAL DEXAMETHASONE IMPLANT INJECTION

PURPOSE

To evaluate microstructural changes in cystoid macular edema in retinitis pigmentosa after intravitreal dexamethasone implant injection.

METHODS

In an extended cohort of a randomized trial of intravitreal dexamethasone implant for the management of retinitis pigmentosa-associated cystoid macular edema, microstructural changes during six months after the treatment were evaluated using spectral-domain optical coherence tomography.

RESULTS

Forty-two eyes were included, and all had cystoid space in the inner nuclear layer (INL) at baseline. No eyes showed subretinal fluid, and 28.6% showed hyperreflective foci. Among 38 eyes with cystoid space both in the INL and outer nuclear layer/Henle's layer, 13 (34.2%) showed complete resolution and 12 (31.6%) showed cystoid space only in the INL at 2 months after injection, whereas others showed persistent cystoid space in both layers. After complete resolution, cystoid space recurrence was earlier in the INL than in the outer nuclear layer/Henle's layer. Multivariable analysis showed that greater cystoid space area in the INL and outer nuclear layer/Henle's layer, presence of macular leakage, and longer intact external limiting membrane at baseline were associated with greater cystoid space area decrease after the treatment.

CONCLUSION

Resolution and recurrence pattern of retinitis pigmentosa-associated cystoid macular edema after dexamethasone treatment showed that the INL is the primary layer of cystic change, and this suggests its pathogenesis is most likely caused by Müller cell dysfunction.

Outcome of Off-Label AREDS 2 Supplementation for the Treatment of Macular Degeneration in Non-Proliferative Idiopathic Type 2 Macular Telangiectasia

Purpose

To evaluate if off-label Age-Related Eye Disease Study 2 (AREDS2) supplementation prevents visual and anatomical deterioration in non-proliferative Idiopathic Macular Telangiectasia Type 2 (IMT2).

Patients and Methods

This is a single-center retrospective, comparative study of 82 IMT2 eyes treated with AREDS2 from January 1st, 2013 to January 1st, 2018. The study analysis consisted of a non-comparative arm, which included all AREDS2 eyes, and a comparative arm (27 AREDS2 and 42 untreated eyes) that only included eyes with complete follow-up data. Eyes were evaluated at baseline, 12 and 24 months. Better/worse eye sub-analysis was performed in the comparative study arm. Primary outcomes were best corrected visual acuity (BCVA) and optical coherence tomography (OCT) anatomical characteristics including largest cavitation diameter, central macular thickness (CMT), and length of ellipsoid zone (EZ) loss at 24 months.

Results

In the non-comparative arm, AREDS2 eyes showed stable BCVA (0.28 ± 0.18 logMAR at baseline vs 0.26 ± 0.19 logMAR at 24 months; p = 0.35) and OCT anatomical features after 24 months of supplementation. In the comparative arm, BCVA mean difference was greater for untreated eyes at 24 months (−0.09 ± 0.15 vs 0.03 ± 0.11 logMAR; p = <0.001). AREDS2 eyes had decreased cavitary diameter and EZ loss compared to untreated eyes at the study endpoint (p = 0.01 and p = 0.02, respectively). CMT remained stable for both cohorts throughout the study. For better/worse eye analysis, untreated eyes had worse BCVA at 24 months in both better and worse eyes (both p = 0.01). For anatomical outcomes, increases in both EZ loss (p = 0.04) and cavitary diameter (p = 0.001) among untreated eyes were only significant for eyes with worse baseline BCVA.

Conclusion

Our results suggest that off-label AREDS2 supplementation in non-proliferative IMT2 may prevent anatomical and visual deterioration in a subset of eyes.

FUNCTIONAL AND STRUCTURAL EFFECTS OF NONDAMAGING RETINAL LASER THERAPY FOR MACULAR TELANGIECTASIA TYPE 2: A Randomized Sham-Controlled Clinical Trial

PURPOSE

Macular telangiectasia (MacTel) Type 2 is a progressing neurovascular disease of the macula, currently lacking effective treatment. This study assessed the effect of nondamaging retinal laser therapy (NRT) compared with sham.

METHODS

Twelve MacTel patients were enrolled in this double-masked, controlled, randomized clinical trial. For the nine patients with both eyes eligible, one eye was randomized to NRT or sham and the other received alternate treatment. For three patients with only one eye eligible, that eye was randomly assigned either NRT or sham. Ellipsoid zone disruption, best-corrected visual acuity, and macular automated perimetry at 12 months served as structural and functional measures.

RESULTS

Eleven eyes were randomized to sham and 10 to NRT. Baseline best-corrected visual acuity was 66 letters (20/50) for sham and 72 letters (20/40) for NRT (P = 0.245). Ellipsoid zone disruption area was 298 µm2 in sham and 368 µm2 in NRT (P = 0.391). At 12 months, ellipsoid zone disruption increased by 24% in sham and decreased by 34% in NRT (P < 0.001). Best-corrected visual acuity measures remained stable during follow-up compared with baseline. At 1 year, the mean macular sensitivity was 28 dB in the NRT group, compared with 26 dB in sham.

CONCLUSION

Nondamaging retinal laser therapy was safe and well tolerated in patients with MacTel and resulted in structural and functional improvements, which could represent a protective effect of laser-induced hyperthermia. Longer follow-up and larger number of patients should help corroborate these effects.

Relevance of Multicolor Imaging in Type 2 Macular Telangiectasia

Purpose

To report the imaging characteristics of various clinical features in idiopathic macular telangiectasia (MacTel 2) on multicolor imaging (MCI) and compare its accuracy vis-à-vis color fundus photograph (CFP) and fluorescein angiography (FA).

Methods

In this retrospective observational study, 54 eyes of 27 patients with MacTel 2 were included after institutional review board approval. Multimodal imaging with CFP, optical coherence tomography (OCT), MCI, and FA was done. Images were analyzed to identify and describe the clinical findings in MacTel 2. Sensitivity, specificity, and positive and negative predictive values were computed for the various imaging modalities in MacTel 2.

Results

In this study, the MCI identified all the different clinical features of MacTel 2 in 100% of cases. The confocal blue reflectance (BR) image was more sensitive than CFP (100% vs. 96.3%) in identifying the loss of retinal transparency in MacTel 2. For other clinical features such as right-angled vessels, superficial retinal crystals, and retinal pigment epithelial hyperplasia/plaques, the sensitivity of BR, and green reflectance (GR) image, was comparable to that of CFP. Confocal infrared reflectance (IR) images showed poor sensitivity in identifying the non-proliferative features in MacTel 2 (P < 0.001). Loss of retinal transparency was not picked up on IR image. Other features such as right-angled vessels, superficial retinal crystals, and pigment plaques were seen in 20%, 4.6%, and 26.3% of cases, respectively. However, confocal IR images were superior to FA (100% vs. 47%) and CFP (100% vs. 15%) in identifying the extent and location of subretinal neovascular membrane. The confocal BR and GR images were unable to identify the choroidal neovascular membrane (P < 0.001).

Conclusion

MCI is a useful and non-invasive imaging modality to identify the clinical features in MacTel 2. MCI can be used as a complementary imaging tool to CFP, FA, and OCT.

CHARACTERIZING RETINAL-CHOROIDAL ANASTOMOSIS IN MACULAR TELANGIECTASIA TYPE 2 WITH OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

PURPOSE

To characterize structural and angiographic findings in macular telangiectasia Type 2 (MacTel 2) and examine associations with visual acuity.

METHODS

MacTel 2 patients with complete ophthalmologic examination, including fundus photography, autofluorescence, spectral-domain optical coherence tomography, and projection-resolved optical coherence tomography angiography, were retrospectively evaluated.

RESULTS

There were 43 eyes of 22 patients with a mean age 63.9 (±10.3) years. Six patients had diabetes. Twenty-one eyes (48.8%) had retinal-choroidal anastomoses (RCAs) without any evidence of neovascularization extending laterally in a plane above or below the retinal pigment epithelium. None of the eyes had hemorrhage, lipid, or signs of subretinal exudation. When present, an average of 55 (±33.7) individual RCAs were clustered primarily in temporal juxtafoveal region of involved eyes. Right-angle veins were seen in all 21 eyes with RCAs, and hyperpigmentation was present in 18 (P < 0.001 for both). A conical collection of hyperreflective material spanning from Bruch membrane past external limiting membrane of ≥200-μm basal diameter was found in 21 eyes and labeled outer retinal hyperreflective lesion. Retinal-choroidal anastomoses occurred in clusters, often within the outer retinal hyperreflective lesion. This lesion colocalized with focal thinning of the outer nuclear layer and was surrounded by a larger defect in the ellipsoid zone. The presence of diabetes (P = 0.015), outer retinal hyperreflective lesion (P = 0.006), RCA (P = 0.005), and ellipsoid zone defect extent (P < 0.001) were associated with decreased visual acuity.

CONCLUSION

Retinal-choroidal anastomoses occur in eyes with MacTel 2 without signs of exudation. Retinal-choroidal anastomoses occur in numerous clusters particularly in the temporal juxtafoveal macula. Diabetes, ellipsoid zone defect extent, RCAs, and the outer retinal hyperreflective lesion predict poorer vision in MacTel 2.