Treatment with interleukin-33 is non-toxic and protects retinal pigment epithelium in an ageing model of outer retinal degeneration.

The leading cause of central vision loss, age-related macular degeneration (AMD), is a degenerative disorder characterized by atrophy of retinal pigment epithelium (RPE) and photoreceptors. For 15% of cases, neovascularization occurs, leading to acute vision loss if left untreated. For the remaining patients, there are currently no treatment options and preventing progressive RPE atrophy remains the main therapeutic goal. Previously, we have shown treatment with interleukin-33 can reduce choroidal neovascularization and attenuate tissue remodelling. Here, we investigate IL-33 delivery in aged, high-fat diet (HFD) fed mice on a wildtype and complement factor H heterozygous knockout background. We characterize the non-toxic effect following intravitreal injection of IL-33 and further demonstrate protective effects against RPE cell death with evidence of maintaining metabolic retinal homeostasis of Cfh+/-~HFD mice. Our results further support the potential utility of IL-33 to prevent AMD progression.

Treatment of diabetic retinopathy through neuropeptide Y-mediated enhancement of neurovascular microenvironment.

Diabetic retinopathy (DR) is one of the most severe clinical manifestations of diabetes mellitus and a major cause of blindness. DR is principally a microvascular disease, although the pathogenesis also involves metabolic reactive intermediates which induce neuronal and glial activation resulting in disruption of the neurovascular unit and regulation of the microvasculature. However, the impact of neural/glial activation in DR remains controversial, notwithstanding our understanding as to when neural/glial activation occurs in the course of disease. The objective of this study was to determine a potential protective role of neuropeptide Y (NPY) using an established model of DR permissive to N-methyl-D-aspartate (NMDA)-induced excitotoxic apoptosis of retinal ganglion cells (RGC) and vascular endothelial growth factor (VEGF)-induced vascular leakage. In vitro evaluation using primary retinal endothelial cells demonstrates that NPY promotes vascular integrity, demonstrated by maintained tight junction protein expression and reduced permeability in response to VEGF treatment. Furthermore, ex vivo assessment of retinal tissue explants shows that NPY can protect RGC from excitotoxic-induced apoptosis. In vivo clinical imaging and ex vivo tissue analysis in the diabetic model permitted assessment of NPY treatment in relation to neural and endothelial changes. The neuroprotective effects of NPY were confirmed by attenuating NMDA-induced retinal neural apoptosis and able to maintain inner retinal vascular integrity. These findings could have important clinical implications and offer novel therapeutic approaches for the treatment in the early stages of DR.

Restoring retinal neurovascular health via substance P.

Regulation of vascular permeability plays a major role in the pathophysiology of visually threatening conditions such as retinal vein occlusion and diabetic retinopathy. Principally, several factors such as vascular endothelial growth factor (VEGF), are up-regulated or induced in response to hypoxia thus adversely affecting the blood-retinal barrier (BRB), resulting in retinal edema and neovascularisation. Furthermore, current evidence supports a dysregulation of the inner retinal neural-vascular integrity as a critical factor driving retinal ganglion cell (RGC) death and visual loss. The principal objective of this study was to interrogate whether Substance P (SP), a constitutive neurotransmitter of amacrine and ganglion cells, may protect against N-methyl-d-aspartate (NMDA)-induced excitotoxic apoptosis of ganglion cells and VEGF-induced vessel leakage in the retina. Tight junctional protein expression and a Vascular Permeability Image Assay were used to determine vascular integrity in vitro. The protective effect of SP on RGC was established in ex vivo retinal explants and in vivo murine models. After NMDA administration, a reduction in TUNEL+ cells and a maintained number of Brn-3a+ cells were found, indicating an inhibition of RGC apoptosis mediated by SP. Additionally, SP maintained endothelial tight junctions and decreased VEGF-induced vascular permeability. In conclusion, administration of SP protects against NMDA apoptosis of RGC and VEGF-induced endothelial barrier breakdown.

Müller Cells Stabilize Microvasculature through Hypoxic Preconditioning.

BACKGROUND/AIMS: Hypoxia of the retina is a common pathogenic drive leading to vision loss as a result of tissue ischemia, increased vascular permeability and ultimately retinal neovascularisation. Here we tested the hypothesis that Müller cells stabilize the neurovascular unit, microvasculature by suppression of HIF-1α activation as a result of hypoxic preconditioning. METHODS: Tube Formation Assay and In vitro Vascular Permeability Image Assay were used to analyze angiogenesis and vascular integrity. Seahorse XF Cell Mito Stress Test was used to measure mitochondrial respiration. Gene and protein expression were examined by qRTPCR, ELISA and western blot. RESULTS: Hypoxic insult induces a significant induction of proangiogenic factors including vascular endothelial growth factor (VEGF) and angiopoietinlike 4 (ANGPTL-4) resulting in angiogenesis and increased vascular permeability of vascular endothelial cells. Hypoxic preconditioning of a human retinal Müller glia cell line significantly attenuates HIF-1α activation through the inhibition of mTOR and concomitant induction of aerobic glycolysis, stabilizing endothelial cells. CONCLUSION: Hypoxic preconditioning of Müller cells confers a robust protection to endothelial cells, through the suppression of HIF1α activation and its downstream regulation of VEGF and ANGPTL-4.

Interleukin-33 regulates tissue remodelling and inhibits angiogenesis in the eye.

Age-related macular degeneration (AMD) is the leading cause of central vision loss worldwide. Loss of retinal pigment epithelium (RPE) is a major pathological hallmark in AMD with or without pathological neovascularization. Although activation of the immune system is implicated in disease progression, pathological pathways remain diverse and unclear. Here, we report an unexpected protective role of a pro-inflammatory cytokine, interleukin-33 (IL-33), in ocular angiogenesis. IL-33 and its receptor (ST2) are expressed constitutively in human and murine retina and choroid. When RPE was activated, IL-33 expression was markedly elevated in vitro. We found that IL-33 regulated tissue remodelling by attenuating wound-healing responses, including reduction in the migration of choroidal fibroblasts and retinal microvascular endothelial cells, and inhibition of collagen gel contraction. In vivo, local administration of recombinant IL-33 inhibited murine choroidal neovascularization (CNV) formation, a surrogate of human neovascular AMD, and this effect was ST2-dependent. Collectively, these data demonstrate IL-33 as a potential immunotherapy and distinguishes pathways for subverting AMD pathology. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Short-term safety of dexamethasone implant for treatment of macular edema due to retinal vein occlusion, in eyes with glaucoma or treated ocular hypertension.

PURPOSE: To report the short-term safety of dexamethasone implants to treat macular edema due to retinal vein occlusion (RVO), in eyes with treated glaucoma or ocular hypertension at baseline using an as-needed re-treatment regimen. METHODS: Retrospective clinical database study from two centers using the same electronic medical record system. Extracted data included: intraocular pressure (IOP), visual acuity (VA), central 1 mm retinal thickness (CRT) by optical coherence tomography, phakic status, number of injections, glaucoma treatment, and peri-operative complications. RESULTS: Thirty-three eyes of 33 patients on IOP-lowering treatment for glaucoma or ocular hypertension (OHT) at baseline and mean IOP of 16 mmHg at baseline received one to four (mean, 1.8; median, 1) dexamethasone implants over 18 months for RVO-related macular edema. Fourteen eyes (42 %) had IOP of ≥21 mmHg, and three eyes (9 %) had IOP of ≥35 mmHg at one or more visits during the study period. Nine of 14 eyes (64 %) with raised IOP required additional topical treatment only for a mean (SE) period of 8.5 months (3.2), while the remaining five eyes (36 %) required long-term additional IOP-lowering treatment for a mean (SE) of 16 months (1.44). Surgery for IOP lowering was not required in any eye. Mean VA (SE) improved from 44 (3) ETDRS letters at baseline to 47 letters (5) at 2 months (p = 0.049), 48 (8) letters at 6 months and 46 (4) letters at 12 months. Mean CRT (SE) improved from 530 (25) µm at baseline to 323 (27) µm at 2 months (p < 0.001), 498 (76) µm at 6 months, and 359 (25) µm at 12 months (p < 0.001). CONCLUSION: The short-term IOP rise after intravitreal dexamethasone implant in eyes with glaucoma or ocular hypertension at baseline was acceptable and consistent with previous reports in patients without preexisting glaucoma. Treated OHT or glaucoma may not be a strict contraindication against the use of dexamethasone implant, but close monitoring of IOP is required.

Role of interleukin 33/ST2 axis in the immune-mediated pathogenesis of age-related macular degeneration.

BACKGROUND: Age-related macular degeneration is a leading cause of irreversible blindness. Altered immune responses drive degeneration, in response to oxidative stress and hypoxia-induced regulation of metabolism. We tested the hypothesis that toll-like receptor activation of retinal pigment epithelium and cellular metabolic switch upregulate interleukin 33, which acts through its receptor ST2 to activate both choroidal stromal fibroblasts and mast cells. By such mechanisms, the fibrosis and insidious degeneration, which we observe clinically, is accentuated. METHODS: Retinal pigment epithelial cells (ARPE-19 and B6-RPE07) were stimulated with toll-like receptor ligands, and energetic pathways were assessed through lactate production and the expression of glycolytic enzymes. Expression profile and secretion of interleukin 33 were determined by RT-PCR and western blots. Function and expression profile of bone-marrow-derived mast cells and human choroidal fibroblasts were also assessed. FINDINGS: The production of lactate, determining aerobic glycolysis, increased after stimulation of retinal pigment epithelial cells with LPS or poly(I:C), indicating an increase in the glycolytic activity after toll-like receptor stimulation. Increased levels of GLUT1 transcripts, and upregulation of GAPDH expression corroborated this finding. Furthermore, increased expression of interleukin 33 was dependent on a glycolytic metabolic switch and was enhanced under hypoxic conditions. ST2 was highly expressed in retinal pigment epithelium, choroidal mast cells, and choroidal fibroblasts in mouse and man. ST2+ bone-marrow-derived mast cells generated a spectrum of inflammatory cytokines and PGS2 when cultured with interleukin-33-rich retinal pigment epithelium supernatant. Interleukin-33 treatment impaired fibroblast migration and gel contraction alongside suppression of MMP-2 and MMP-9 expression. INTERPRETATION: Our data highlight an unrecognised link between retinal pigment epithelium bioenergetic status and tissue remodelling of choroidal stroma. Our findings suggest that the interleukin 33/ST2 axis and changing bioenergetic sources are potential therapeutic targets to inhibit progression of age-related macular degeneration. FUNDING: National Institute for Health Research, National Eye Research Centre.

Diet and cataract: a case-control study.

We conducted a case-control study to assess the association between diet and risk of cataract in Athens, Greece. Totals of 314 cases and 314 frequency-matched controls of both sexes, aged 45-85 years and attending the ophthalmology department of a major teaching hospital in Athens, Greece, were included in the study. All participants were interviewed using a semi-quantitative food-frequency questionnaire, covering the average frequency of consumption of about 120 food items. Analyses were conducted through multiple logistic regression. The analysis was carried out taking cataract as a general outcome (all types of cataract combined) and repeated by the specific type of cataract. We found significant inverse associations of cataract with dietary consumption of fish (OR = 0.69, p < 0.001), vegetables (OR = 0.47, p < 0.001), fruits (OR = 0.53, p < 0.001), and potatoes (OR = 0.76, p = 0.004), while consumption of meat was positively associated with cataract (OR = 1.46, p = 0.001). High intake of total fat (OR = 2.00, p < 0.001) and cholesterol (OR = 1.65, p < 0.001) increased the risk of cataract. There was a protective association between cataract risk and intake of carbohydrates (OR = 0.39, p < 0.001), carotene (OR = 0.56, p < 0.001), vitamins C and E (OR = 0.50, p < 0.001 and OR = 0.50, p < 0.001 respectively). We identified an association between the risk of cataract and several food groups and nutrients. Diets rich in fruits, vegetables, fish, pulses and starchy foods may protect against cataract. In addition, high intake of vitamins C and E and carotene with reduction of intake in total fat and cholesterol may be beneficial. Dietary advice along these lines may provide adequate public health guidelines for the delay of age-related cataract.

Replenishing IRAK-M expression in retinal pigment epithelium attenuates outer retinal degeneration.

Chronic inflammation is a constitutive component of many age-related diseases, including age-related macular degeneration (AMD). Here, we identified interleukin-1 receptor-associated kinase M (IRAK-M) as a key immunoregulator in retinal pigment epithelium (RPE) that declines during the aging process. Rare genetic variants of IRAK3, which encodes IRAK-M, were associated with an increased likelihood of developing AMD. In human samples and mouse models, IRAK-M abundance in the RPE declined with advancing age or exposure to oxidative stress and was further reduced in AMD. Irak3-knockout mice exhibited an increased incidence of outer retinal degeneration at earlier ages, which was further exacerbated by oxidative stressors. The absence of IRAK-M led to a disruption in RPE cell homeostasis, characterized by compromised mitochondrial function, cellular senescence, and aberrant cytokine production. IRAK-M overexpression protected RPE cells against oxidative or immune stressors. Subretinal delivery of adeno-associated virus (AAV)-expressing human IRAK3 rescued light-induced outer retinal degeneration in wild-type mice and attenuated age-related spontaneous retinal degeneration in Irak3-knockout mice. Our data show that replenishment of IRAK-M in the RPE may redress dysregulated pro-inflammatory processes in AMD, suggesting a potential treatment for retinal degeneration.

Disengagement and loss to follow-up in intravitreal injection clinics for neovascular age-related macular degeneration.

BACKGROUND/OBJECTIVES: Timely assessment and treatment of patients with neovascular AMD (nAMD) are crucial to preservation of vision. Loss to follow up (LTFU) in these patients is a problem but this has not been systematically investigated. SUBJECTS/METHODS: A retrospective review of electronic medical records of patients with nAMD first treated with anti-VEGF therapy from 1st Jan 2014 to 31st Dec 2018, was conducted in January 2021. Any patient not seen for more than 12 months was classed as no longer attending. RESULTS: Of the 1328 patients who attended between 2014 and 2018, 348 had failed to attend and were eligible for inclusion in this study. Reasons noted for discontinuation of care: discharged by clinician (33.3%), died (20.7%), moved to another unit outside of area (17.5%), stopped attending due to ill-health (13.5%), discharged due to failure to attend (5.6%) and patient choice to no longer attend (4.6%). There were 16 (4.6%) who did not receive any further appointments despite clinician request for follow-up. After 5 years, 50.5% of patients were no longer attending for treatment. Age was a factor in failure to attend, with 7 out of 12 patients aged >100 years no longer being followed up, compared to 1 out of 11 of 50-59 year-olds. CONCLUSIONS: When analysing visual outcomes in an AMD service it is important to characterise the patients who are lost to follow up. The outcomes for this group may be avoidably poor and understanding the factors influencing LTFU rate is crucial to addressing shortcomings in a hospital AMD service.

Replenishing Age-Related Decline of IRAK-M Expression in Retinal Pigment Epithelium Attenuates Outer Retinal Degeneration.

Unchecked, chronic inflammation is a constitutive component of age-related diseases, including age-related macular degeneration (AMD). Here we identified interleukin-1 receptor-associated kinase (IRAK)-M as a key immunoregulator in retinal pigment epithelium (RPE) that declines with age. Rare genetic variants of IRAK-M increased the likelihood of AMD. IRAK-M expression in RPE declined with age or oxidative stress and was further reduced in AMD. IRAK-M-deficient mice exhibited increased incidence of outer retinal degeneration at earlier ages, which was further exacerbated by oxidative stressors. The absence of IRAK-M disrupted RPE cell homeostasis, including compromised mitochondrial function, cellular senescence, and aberrant cytokine production. IRAK-M overexpression protected RPE cells against oxidative or immune stressors. Subretinal delivery of AAV-expressing IRAK-M rescued light-induced outer retinal degeneration in wild-type mice and attenuated age-related spontaneous retinal degeneration in IRAK-M-deficient mice. Our data support that replenishment of IRAK-M expression may redress dysregulated pro-inflammatory processes in AMD, thereby treating degeneration.

Heat shock protein 70 (HSP70) is critical for the photoreceptor stress response after retinal detachment via modulating anti-apoptotic Akt kinase.

Photoreceptor apoptosis is a major cause of vision loss in many ocular diseases. Significant progress has been made to elucidate the molecular pathways involved in this process, yet little is known about proteins counteracting these apoptotic pathways. It is established that heat shock proteins (HSPs) function as molecular helper proteins (chaperones) by preventing protein aggregation and facilitating refolding of dysfunctional proteins, critical to the survival of all organisms. Here, we investigated the role of HSP70 on photoreceptor survival after experimental retinal detachment (RD) in mice and rats. We found that HSP70 was up-regulated after RD and associated with phosphorylated Akt, thereby preventing its dephosphorylation and further activation of cell death pathways. Administration of quercetin, which inhibits HSP70 and suppresses Akt phosphorylation significantly increased photoreceptor apoptosis. Similarly, RD-induced photoreceptor apoptosis was augmented in mice carrying hypomorphic mutations of the genes encoding HSP70. On the other hand, administration of geranylgeranylacetone, which induces an increase in HSP70 significantly decreased photoreceptor apoptosis after RD through prolonged activation of Akt pathway. Thus, HSP70 may be a favorable potential target to increase photoreceptor cell survival after RD.

Hemodialysis-induced alterations in macular thickness measured by optical coherence tomography in diabetic patients with end-stage renal disease.

BACKGROUND/AIMS: To evaluate changes in macular thickness measured by optical coherence tomography (OCT) during a hemodialysis (HD) session in diabetic patients with end-stage renal disease. METHODS: 72 eyes of 36 diabetic patients with and without macular edema were evaluated before and immediately after an HD session. Average and maximum macular thicknesses in the central disk (6 mm in diameter) and total macular volume were measured. RESULTS: In the eyes with diabetic macular edema, maximum macular thickness within the central disk of 6 mm, and mainly in its peripheral parts, was significantly reduced by 31.18 ± 4.18 µm after HD (p < 0.001). Average macular thickness and total macular volume were also significantly reduced (p = 0.003 and 0.015, respectively). In diabetic eyes without edema, maximum macular thickness decreased significantly by 11.21 ± 1.98 µm after HD (p < 0.001), while average macular thickness and total macular volume decreased slightly (p = 0.034, p = 0.043). Best-corrected visual acuity failed to change. We found a significant association of macular thickness changes with osmolality reduction and the presence of macular edema. CONCLUSION: HD decreases macular thickness in diabetic patients with macular edema, while there exists a less-pronounced effect in diabetic eyes without edema.

Unravelling the therapeutic potential of IL-33 for atrophic AMD.

Age-related macular degeneration (AMD), a degenerative disease affecting the retinal pigment epithelium (RPE) and photoreceptors in the macula, is the leading cause of central blindness in the elderly. AMD progresses to advanced stages of the disease, atrophic AMD (aAMD), or in 15% of cases "wet" or neovascular AMD (nAMD), associated with substantial vision loss. Whilst there has been advancement in therapies treating nAMD, to date, there are no licenced effective treatments for the 85% affected by aAMD, with disease managed by changes to diet, vitamin supplements, and regular monitoring. AMD has a complex pathogenesis, involving highly integrated and common age-related disease pathways, including dysregulated complement/inflammation, impaired autophagy, and oxidative stress. The intricacy of AMD pathogenesis makes therapeutic development challenging and identifying a target that combats the converging disease pathways is essential to provide a globally effective treatment. Interleukin-33 is a cytokine, classically known for the proinflammatory role it plays in allergic disease. Recent evidence across degenerative and inflammatory disease conditions reveals a diverse immune-modulatory role for IL-33, with promising therapeutic potential. Here, we will review IL-33 function in disease and discuss the future potential for this homeostatic cytokine in treating AMD.

Retinoblastoma cells are inhibited by aminoimidazole carboxamide ribonucleotide (AICAR) partially through activation of AMP-dependent kinase.

5-Aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside (AICAR), an analog of AMP, is widely used as an activator of AMP-kinase (AMPK), a protein that regulates the responses of the cell to energy change. We studied the effects of AICAR on the growth of retinoblastoma cell lines (Y79, WERI, and RB143). AICAR inhibited Rb cell growth, induced apoptosis and S-phase cell cycle arrest, and led to activation of AMPK. These effects were abolished by treatment with dypiridamole, an inhibitor that blocks entrance of AICAR into cells. Treatment with the adenosine kinase inhibitor 5-iodotubericidin to inhibit the conversion of AICAR to ZMP (the direct activator of AMPK) reversed most of the growth-inhibiting effects of AICAR, indicating that some of the antiproliferative effects of AICAR are mediated through AMPK activation. In addition, AICAR treatment was associated with inhibition of the mammalian target of rapamycin pathway, decreased phosphorylation of ribosomal protein-S6 and 4E-BP1, down-regulation of cyclins A and E, and decreased expression of p21. Our results indicate that AICAR-induced activation of AMPK inhibits retinoblastoma cell growth. This is one of the first descriptions of a nonchemotherapeutic drug with low toxicity that may be effective in treating Rb patients.

Study of Xbal and Pvull polymorphisms of estrogen receptor alpha (ERα) gene in girls with precocious/early puberty.

PURPOSE: Studies examining association of estrogen receptor alpha (ERα) polymorphisms with early puberty are scarce and results are controversial; data in Caucasian girls are lacking. Main objective was to determine association of Xbal and Pvull polymorphisms of ERα gene in Greek girls with precocious/early puberty METHODS: We studied 107 girls with idiopathic precocious/early puberty and 81 young women with pubertal maturation within normal age (controls). Pubertal stage, height SDS (HSDS), and BMI z-score were determined in patients. In controls, height was measured and menarcheal age was self-reported. All participants in the study were genotyped for XbaI and PvuII polymorphisms of the ERα gene. RESULTS: There was no significant difference in XbaI and PvuII polymorphisms between patients and controls. Homozygous, xx and pp, girls had an earlier onset of puberty, although non-significant, than heterozygous or with no polymorphisms p = 0.9; in girls with pubertal onset <7 years, the association tended to become significant, p = 0.09. Girls with xxpp genotype were significantly taller, HSDS 1.63, p = 0.014. In controls, homozygosity for Xbal (xx) and PvuII (pp) was associated with significantly earlier menarche than in women with no polymorphism, p = 0.013 and p = 0.026, respectively, and xxpp genotype was associated with taller adult height, p = 0.017. CONCLUSION: XbaI and PvuII polymorphisms are not related to idiopathic precocious/early puberty. Early pubertal girls homozygous for both polymorphisms presented earlier onset of puberty, although statistically non-significant, and taller height than girls heterozygous or without these polymorphisms. Homozygosity for both polymorphisms is associated with earlier menarche and taller adult height.

Interleukin-33 regulates metabolic reprogramming of the retinal pigment epithelium in response to immune stressors.

It remains unresolved how retinal pigment epithelial cell metabolism is regulated following immune activation to maintain retinal homeostasis and retinal function. We exposed retinal pigment epithelium (RPE) to several stress signals, particularly Toll-like receptor stimulation, and uncovered an ability of RPE to adapt their metabolic preference on aerobic glycolysis or oxidative glucose metabolism in response to different immune stimuli. We have identified interleukin-33 (IL-33) as a key metabolic checkpoint that antagonizes the Warburg effect to ensure the functional stability of the RPE. The identification of IL-33 as a key regulator of mitochondrial metabolism suggests roles for the cytokine that go beyond its extracellular "alarmin" activities. IL-33 exerts control over mitochondrial respiration in RPE by facilitating oxidative pyruvate catabolism. We have also revealed that in the absence of IL-33, mitochondrial function declined and resultant bioenergetic switching was aligned with altered mitochondrial morphology. Our data not only shed new light on the molecular pathway of activation of mitochondrial respiration in RPE in response to immune stressors but also uncover a potentially novel role of nuclear intrinsic IL-33 as a metabolic checkpoint regulator.

Clinical pathophysiology of thyroid eye disease: The Cone Model.

The clinical features of thyroid eye disease are dictated by the orbit's compartmentalisation; particularly, the muscle cone, which is delimited by the rectus muscles, their inter-muscular septa and the posterior sclera. The cone is anchored to the orbit apex and contains the posterior globe, the muscle bellies, a fat pad, and the blood circulation, optic nerve, and CSF sheath. It is surrounded by mobile extraconal fat, retained by the orbital septum.Thyroid eye disease is caused by expansion of muscle bellies and fat within the cone. Mechanical properties of the cone determine that the disease partitions into three phases: circumferential expansion, with forward displacement of extraconal fat; axial elongation, with increasing cone pressure; impedance of posterior venous outflow, with cone oedema and venous flow reversal.Venous flow reversal can be observed in the conjunctival circulation. It is initially transient, accompanying rises in cone pressure caused by eye movements, but later becomes permanent. It is a useful clinical sign that locates diseased muscles and anticipates venous compressive crises.Strabismus arises when inflamed rectus muscles, swollen by hydrated glycosaminoglycans, lose contractility and compliance. The incomitance is moderated by increasing stiffness affecting all the rectus muscles, as they are stretched during cone expansion.Immunomodulation, which rapidly reduces cone volume, relieving muscle elongation and stiffness, may paradoxically unmask strabismus. However, ciclosporin A suppresses late post-inflammatory fibrosis and only 4 of 71 patients so-treated required strabismus surgery.The cone model also accounts for the variety of clinical presentations of thyroid eye disease.