Cellular and plasma fibronectin in the aqueous humour of primary open-angle glaucoma, exfoliative glaucoma and cataract patients

Aqueous humor proteomic analysis of acute angle-closure glaucoma with visual field loss

Background

Acute angle-closure glaucoma (AACG) is an ophthalmic emergency that occurs over the course of hours or days and may cause irreversible blindness if not treated immediately. In most cases, optic nerve damage is the cause of visual field (VF) loss in AACG. There has been no reliable biomarker found to evaluate optic nerve damage to date. Aqueous humor (AH) proteome analysis might reveal the proteomic alterations in AACG and provide helpful clues in the search for an AH biomarker of optic nerve damage and VF loss.

Methods

In this study, we used the AH proteome to explore the functions of differentially expressed proteins (DEPs) during disease progression. The AH proteins from the early-stage group and late-stage group were extracted and analyzed by the data-independent acquisition (DIA) method. The DEPs functions were annotated, and parallel reaction monitoring (PRM) was used to validate the key DEPs.

Results

A total of 87 DEPs were found. Gene Ontology analysis showed that most DEPs were enriched in immunology, hemodynamics, and apoptosis. Ingenuity pathway analysis found that vascular endothelial growth factor (VEGF) signaling, the production of reactive oxygen species (ROS) in macrophages, and the nuclear factor erythroid 2-related factor 2 (NRF2)-mediated oxidative stress response were active pathways in the late stage of AACG. The mechanism of retinal ganglion cell (RGC) death was hypothesized on the basis of DEP functional analysis. A total of 20 DEPs were validated by using PRM, and prostaglandin-H2 D-isomerase was found to have the potential to evaluate optic nerve damage.

Conclusions

This study showed that AH proteomic analysis could reveal the proteomic alterations in the pathogenesis of VF loss in AACG and help to provide objective protein biomarkers to evaluate VF loss. These findings will benefit the application of the AH proteome to clinical research.

Candidate Glaucoma Biomarkers: From Proteins to Metabolites, and the Pitfalls to Clinical Applications

Glaucoma is an insidious group of eye diseases causing degeneration of the optic nerve, progressive loss of vision, and irreversible blindness. The number of people affected by glaucoma is estimated at 80 million in 2021, with 3.5% prevalence in people aged 40-80. The main biomarker and risk factor for the onset and progression of glaucoma is the elevation of intraocular pressure. However, when glaucoma is diagnosed, the level of retinal ganglion cell death usually amounts to 30-40%; hence, the urgent need for its early diagnosis. Molecular biomarkers of glaucoma, from proteins to metabolites, may be helpful as indicators of pathogenic processes observed during the disease's onset. The discovery of human glaucoma biomarkers is hampered by major limitations, including whether medications are influencing the expression of molecules in bodily fluids, or whether tests to validate glaucoma biomarker candidates should include human subjects with different types and stages of the disease, as well as patients with other ocular and neurodegenerative diseases. Moreover, the proper selection of the biofluid or tissue, as well as the analytical platform, should be mandatory. In this review, we have summarized current knowledge concerning proteomics- and metabolomics-based glaucoma biomarkers, with specificity to human eye tissue and fluid, as well the analytical approach and the main results obtained. The complex data published to date, which include at least 458 different molecules altered in human glaucoma, merit a new, integrative approach allowing for future diagnostic tests based on the absolute quantification of local and/or systemic biomarkers of glaucoma.

Aqueous Fibronectin Correlates With Severity of Macular Edema and Visual Acuity in Patients With Branch Retinal Vein Occlusion: A Proteome Study

Purpose

Large-scale protein analysis may bring important insights into molecular changes following branch retinal vein occlusion (BRVO). Using proteomic techniques this study compared aqueous humor samples from patients with BRVO to age-matched controls.

Methods

Aqueous humor samples from treatment naive patients with BRVO complicated by macular edema (n = 19) and age-matched controls (n = 18) were analyzed with label-free quantification nano liquid chromatography - tandem mass spectrometry (LFQ nLC-MS/MS). The severity of macular edema was measured as central retinal thickness (CRT) with optical coherence tomography. Control samples were obtained prior to cataract surgery. Proteins were filtered by requiring quantification in at least 50% of the samples in each group without imputation of missing values. Significantly changed proteins were identified with a permutation-based calculation with a false discovery rate at 0.05.

Results

In BRVO, 52 proteins were differentially expressed. Regulated proteins were involved in cell adhesion, coagulation, and acute-phase response. Apolipoprotein C-III, complement C3, complement C5, complement factor H, fibronectin, and fibrinogen chains were increased in BRVO and correlated with CRT. Fibronectin also correlated with best corrected visual acuity (BCVA) and vascular endothelial growth factor (VEGF). Monocyte differentiation antigen CD14 (CD14) and lipopolysaccharide-binding protein (LBP) were upregulated in BRVO. Contactin-1 and alpha-enolase were downregulated in BRVO and correlated negatively with CRT.

Conclusions

Multiple proteins, including complement factors, fibrinogen chains, and apolipoprotein C-III, correlated with CRT, indicating a multifactorial response. Fibronectin correlated with BCVA, CRT, and VEGF. Fibronectin may reflect the severity of BRVO. The proinflammatory proteins CD14 and LBP were upregulated in BRVO.

Glucocorticoid-induced cell-derived matrix modulates transforming growth factor β2 signaling in human trabecular meshwork cells

Aberrant remodeling of trabecular meshwork (TM) extracellular matrix (ECM) may induce ocular hypertensive phenotypes in human TM (hTM) cells to cause ocular hypertension, via a yet unknown mechanism. Here, we show that, in the absence of exogenous transforming growth factor-beta2 (TGFβ2), compared with control matrices (VehMs), glucocorticoid-induced cell-derived matrices (GIMs) trigger non-Smad TGFβ2 signaling in hTM cells, correlated with overexpression/activity of structural ECM genes (fibronectin, collagen IV, collagen VI, myocilin), matricellular genes (connective tissue growth factor [CTGF], secreted protein, acidic and rich in cysteine), crosslinking genes/enzymes (lysyl oxidase, lysyl oxidase-like 2–4, tissue transglutaminase-2), and ECM turnover genes/enzymes (matrix metalloproteinases-MMP2,14 and their inhibitors-TIMP2). However, in the presence of exogenous TGFβ2, VehMs and GIMs activate Smad and non-Smad TGFβ2 signaling in hTM cells, associated with overexpression of α-smooth muscle actin (α-SMA), and differential upregulation of aforementioned ECM genes/proteins with new ones emerging (collagen-I, thrombospondin-I, plasminogen activator inhibitor, MMP1, 9, ADAMTS4, TIMP1); with GIM-TGFβ2-induced changes being mostly more pronounced. This suggests dual glaucomatous insults potentiate profibrotic signaling/phenotypes. Lastly, we demonstrate type I TGFβ receptor kinase inhibition abrogates VehM-/GIM- and/or TGFβ2-induced upregulation of α-SMA and CTGF. Collectively, pathological TM microenvironments are sufficient to elicit adverse cellular responses that may be ameliorated by targeting TGFβ2 pathway.

Fibronectin has multifunctional roles in posterior capsular opacification (PCO)

Fibrotic posterior capsular opacification (PCO), one of the major complications of cataract surgery, occurs when lens epithelial cells (LCs) left behind post cataract surgery (PCS) undergo epithelial to mesenchymal transition, migrate into the optical axis and produce opaque scar tissue. LCs left behind PCS robustly produce fibronectin, although its roles in fibrotic PCO are not known. In order to determine the function of fibronectin in PCO pathogenesis, we created mice lacking the fibronectin gene (FN conditional knock out -FNcKO) from the lens. While animals from this line have normal lenses, upon lens fiber cell removal which models cataract surgery, FNcKO LCs exhibit a greatly attenuated fibrotic response from 3 days PCS onward as assessed by a reduction in surgery-induced cell proliferation, and fibrotic extracellular matrix (ECM) production and deposition. This is correlated with less upregulation of Transforming Growth Factor β (TGFβ) and integrin signaling in FNcKO LCs PCS concomitant with sustained Bone Morphogenetic Protein (BMP) signaling and elevation of the epithelial cell marker E cadherin. Although the initial fibrotic response of FNcKO LCs was qualitatively normal at 48 h PCS as measured by the upregulation of fibrotic marker protein αSMA, RNA sequencing revealed that the fibrotic response was already quantitatively attenuated at this time, as measured by the upregulation of mRNAs encoding molecules that control, and are controlled by, TGFβ signaling, including many known markers of fibrosis. Most notably, gremlin-1, a known regulator of TGFβ superfamily signaling, was upregulated sharply in WT LCs PCS, while this response was attenuated in FNcKO LCs. As exogenous administration of either active TGFβ1 or gremlin-1 to FNcKO lens capsular bags rescued the attenuated fibrotic response of fibronectin null LCs PCS including the loss of SMAD2/3 phosphorylation, this suggests that fibronectin plays multifunctional roles in fibrotic PCO development.

Role of Fibronectin in Primary Open Angle Glaucoma

Primary open angle glaucoma (POAG) is the most common form of glaucoma and the 2nd most common cause of irreversible vision loss in the United States. Nearly 67 million people have the disease worldwide including >3 million in the United States. A major risk factor for POAG is an elevation in intraocular pressure (IOP). The increase in IOP is believed to be caused by an increase in the deposition of extracellular matrix proteins, in particular fibronectin, in a region of the eye known as the trabecular meshwork (TM). How fibronectin contributes to the increase in IOP is not well understood. The increased density of fibronectin fibrils is thought to increase IOP by altering the compliance of the trabecular meshwork. Recent studies, however, also suggest that the composition and organization of fibronectin fibrils would affect IOP by changing the cell-matrix signaling events that control the functional properties of the cells in the trabecular meshwork. In this article, we will discuss how changes in the properties of fibronectin and fibronectin fibrils could contribute to the regulation of IOP.

Fibronectin regulates growth factor signaling and cell differentiation in primary lens cells

Lens epithelial cells are bound to the lens extracellular matrix capsule, of which laminin is a major component. After cataract surgery, surviving lens epithelial cells are exposed to increased levels of fibronectin, and so we addressed whether fibronectin influences lens cell fate, using DCDML cells as a serum-free primary lens epithelial cell culture system. We found that culturing DCDMLs with plasma-derived fibronectin upregulated canonical TGFβ signaling relative to cells plated on laminin. Fibronectin-exposed cultures also showed increased TGFβ signaling-dependent differentiation into the two cell types responsible for posterior capsule opacification after cataract surgery, namely myofibroblasts and lens fiber cells. Increased TGFβ activity could be identified in the conditioned medium recovered from cells grown on fibronectin. Other experiments showed that plating DCDMLs on fibronectin overcomes the need for BMP in fibroblast growth factor (FGF)-induced lens fiber cell differentiation, a requirement that is restored when endogenous TGFβ signaling is inhibited. These results demonstrate how the TGFβ-fibronectin axis can profoundly affect lens cell fate. This axis represents a novel target for prevention of late-onset posterior capsule opacification, a common but currently intractable complication of cataract surgery.

Human aqueous humor proteome in cataract, glaucoma, and pseudoexfoliation syndrome

Twenty-nine human aqueous humor samples from patients with eye diseases such as cataract and glaucoma with and without pseudoexfoliation syndrome were characterized by LC-high resolution MS analysis. In total, 269 protein groups were identified with 1% false discovery rate including 32 groups that were not reported previously for this biological fluid. Since the samples were analyzed individually, but not pooled, 36 proteins were identified in all samples, comprising the constitutive proteome of the fluid. The most dominant molecular function of aqueous humor proteins as determined by GO analysis is endopeptidase inhibitor activity. Label-free protein quantification showed no significant difference between glaucoma and cataract aqueous humor proteomes. At the same time, we found decrease in the level of apolipoprotein D as a marker of the pseudoexfoliation syndrome. The data are available from ProteomeXchange repository (PXD002623).

The potentialities proteomic analysis of ocular fluids and tissues in different ophthamic disordeers

The article presents a review of current researches in using the proteomic analysis for different eye diseases diagnosis. Special attention is paid to tear fluid and aqueous humor mass-spectrometry results in primary open-angle glaucoma, and to the possibility of using this method for diagnosis at disease early stages.

Pseudoexfoliation Syndrome and Pseudoexfoliation Glaucoma: A Review of the Literature with Updates on Surgical Management

Pseudoexfoliation syndrome (PES) is a systemic disorder caused by progressive accumulation of extracellular material over various tissues. PES usually determines increased intraocular pressure, changes in the anatomical aspects of the optic nerve, and visual field alterations leading to the diagnosis of pseudoexfoliation glaucoma (PEG). Use of topical medical treatment usually leads to poor results in terms of long-term follow-up but many surgical techniques, such as Argon Laser or Selective Laser Trabeculoplasty, have been proposed for the management of PEG affected patients. The present paper is a review on the pseudoexfoliation syndrome and pseudoexfoliation glaucoma with an update on surgical management.

Biomarkers of primary open-angle glaucoma

Primary open-angle glaucoma (POAG) is a primary neuronal disease of the optic nerve without a definable cause, and is often associated with increased intraocular pressure. Worldwide, POAG is the second leading cause of blindness; there are 45 million people today with POAG and bilateral blindness is present in 4.5 million of these. In order to elucidate the possible etiologic factors in POAG, we have cataloged all known biomarkers in the aqueous humor, trabecular meshwork, optic nerve and blood into four categories, namely extracellular matrix (ECM), cell signaling molecules, aging/stress and immunity-related changes. We present a theoretical model to show possible signaling pathways of the ECM, cell signaling and innate immune response through activation of Toll-like receptor 4. Our article suggests that ECM and innate immune biomarkers are the lead candidates for developing the 'POAG biomarker signature'. We suggest that current research is critical to pinpoint the causes of the disease so that new treatment modalities can become available for better regulation of the intraocular pressure and neuroprotection of the optic nerve.

New insights into autoantibody profiles from immune privileged sites in the eye: a glaucoma study

Glaucoma is a chronic neurodegenerative disease and one of the leading causes of blindness. Autoantibody based immune processes are assumed to be involved in its pathogenesis. However, it is still unclear to what extent autoantibody patterns found in the eye (aqueous humor) are congruent to systemic autoantibodies (blood). Consistency would underline the specificity of known serum antibody markers for glaucoma. In this study we used antigen microarrays to analyze autoantibody reactivities in sera and corresponding aqueous humor samples of primary open-angle glaucoma patients (N=37) and non-glaucomatous controls (N=31). Compared to control subjects several divergent immunoreactivities were identified for the glaucoma group in both body fluids. Interestingly, 20% of the tested antigens revealed increased immunoreactivities (e.g., against HSP27, MBP, and α-1-antitrypsin) and 7.5% decreased immunoreactivities (e.g., against GFAP and β-L-crystallin), thus demonstrating a significant alteration of the autoantibody profiles in glaucoma patients. Using an artificial neural network in combination with a unique serum autoantibody pattern on prospective sera we were able to detect glaucoma with a specificity and sensitivity of approximately 93%. The intraindividual comparison revealed a strong correlation of detected immunoreactivities in sera and comparative aqueous humor samples in both study groups. These results emphasize the specificity of immunoreactions found in blood samples of glaucoma patients. Furthermore they indicate the necessity of analyzing not only up-regulated but also down-regulated antibody reactivities, which might be likewise relevant for the understanding of other diseases.

Antibodies to α B-Crystallin, Vimentin, and Heat Shock Protein 70 in Aqueous Humor of Patients with Normal Tension Glaucoma and IgG Antibody Patterns Against Retinal Antigen in Aqueous Humor

PURPOSE

To show the existence of IgG antibodies against retinal antigens in aqueous humor of normal tension glaucoma patients.

METHODS

Forty-two patients were included in this study. Aqueous humor was collected from control subjects (CO; n = 21) and patients with normal tension glaucoma (NTG; n = 21). Western blot methods against bovine retinal antigens were used to detect the IgG antibody patterns. The complex antibody repertoires were analyzed by multivariate statistical techniques. Mass spectrometry was used to identify the most important antigens.

RESULTS

Very complex IgG antibody patterns against retinal antigens were found in all analyzed aqueous humor samples. Our multivariate approach could quantify differences in immunoreactivities, and including all peaks, the analysis of discriminance revealed a statistical significant difference between the patterns of the NTG and the CO group (p < 0.001). The antigen band at 21 kDa was identified as alpha B-crystallin, the 57-kDa antigen band as vimentin, and one at 70 kDa as heat shock protein 70.

CONCLUSIONS

We could demonstrate that complex IgG antibody patterns against retina exist in aqueous humor. The significant differences in the antibody pattern of the glaucoma group compared with the nonglaucoma group in aqueous humor confirm the results of previous studies using sera of glaucoma patients. These differences in antibody patterns might be further evidence for an autoimmune involvement in the pathogenesis of some glaucoma patients.

Cataract and glaucoma surgery in pseudoexfoliation syndrome: a review

Pseudoexfoliation syndrome is a risk factor in cataract surgery because of the increased weakness of zonular apparatus and reduced pupillary dilatation. The surgical outcome of using phacoemulsification in the central zone, inducing minimal stress on the zonules, inserting a capsular tension ring in selected cases, and stretching the pupil mechanically in eyes with miotic pupils, may turn out to be uneventful in most cases. Postoperative fibrosis with subsequent shrinkage of the capsule is increased in these eyes, and these centripetal forces will further loosen the zonular fibres. Late in-the-bag intraocular lens dislocation is therefore anticipated to become a growing problem in the future. Despite the dysfunctioning of the blood-aqueous barrier in eyes with pseudoexfoliation syndrome, the frequency of postoperative inflammatory reaction is low due to the improvements made in surgical technique and equipment in recent years. Glaucoma frequently occurs in eyes with pseudoexfoliation syndrome. Compared with primary open-angle glaucoma, optic damage is more pronounced in these eyes at the time of diagnosis and response to medical therapy is poorer. Although responses to argon laser therapy and filtering surgery are roughly similar between the two types of glaucoma, there are indications that primary laser trabeculoplasty has a higher success rate in pseudoexfoliation glaucoma than in primary open-angle glaucoma.

Increased postoperative concentrations of tenascin-C in wound fluid

BACKGROUND

Tenascin-C (Tn-C) is the most studied member of a family comprising large oligomeric glycoproteins in the extracellular matrix. The function of Tn-C still is unclear, and the levels of Tn-C in human wound fluid have not been studied.

METHODS

The participants in this study were 24 patients referred for elective major gastrointestinal surgery. Concentrations of Tn-C and procollagen propeptides type 1 and type 3 in serum and wound fluid were measured after surgery.

RESULTS

In wound fluid, Tn-C was present on postoperative day 1, and the concentration increased from day 5 up to day 7.

CONCLUSIONS

The concentration of Tn-C increases postoperatively in wound fluid. The concentration of Tn-C in wound fluid is markedly higher than that of serum. The differences in expression between Tn-C and the procollagen propeptides may reflect different tasks of these extracellular matrix proteins.

Intraocular and plasma levels of cellular fibronectin in patients with uveitis and diabetes mellitus

AIMS

To determine intraocular and plasma levels of cellular fibronectin (cFN) in patients with uveitis or diabetes mellitus (DM) and to assess the association with disease activity, macular oedema, and vascular leakage on fluorescein angiography. In addition, to examine whether cFN is locally produced in the eye.

METHODS

Intraocular and plasma levels of cFN were determined by ELISA in 39 patients with uveitis (23 active, 16 non-active), in 11 patients with DM (eight with and three without diabetic retinopathy) and in 17 control patients. The influence of diabetic retinopathy, inflammatory activity, vascular leakage, and macular oedema (MO) on intraocular and plasma cFN levels was studied. Local production of cFN was determined by calculating absolute and relative intraocular to plasma ratios. Aqueous and vitreous levels of cFN were compared.

RESULTS

No differences in plasma cFN levels were found between patients with uveitis, DM, or controls. Intraocular cFN levels were significantly raised in patients with uveitis and DM, specifically in those with active disease (active uveitis and active diabetic retinopathy versus controls: p = 0.001 and 0.002 respectively). Further, intraocular cFN levels were significantly elevated in patients with macular oedema or vascular leakage, irrespectively of whether associated with uveitis or DM (p = 0.001 and 0.002). Intraocular cFN levels were consistently higher in the vitreous than the aqueous. Intraocular production of cFN was documented by elevated absolute and relative intraocular to plasma ratios in nine out of 11 patients tested.

CONCLUSIONS

Elevated intraocular cFN levels were found in uveitis and DM, especially in those with active processes, intraocular vascular damage, and MO. These results suggest that locally produced cFN levels reflect intraocular vascular damage.

Role of transforming growth factor-beta1 and its latent form binding protein in pseudoexfoliation syndrome

Pseudoexfoliation (PEX) syndrome is a common and clinically important systemic condition characterized by the pathologic production and accumulation of an abnormal fibrillar extracellular material in many intra- and extraocular tissues. Recent evidence suggests that it is a type of elastosis associated with the excess synthesis of elastic microfibrillar components such as fibrillin-1. Since transforming growth factor (TGF)-beta is a major modulator of extracellular matrix formation, the potential involvement of TGF-beta and its latent form binding protein (LTBP) in this aberrant matrix process was investigated. The expression of various isoforms of TGF-beta and LTBP was investigated in the anterior segment tissues of PEX and control eyes on the protein and mRNA level by light and electron microscopic immunohistochemistry, in situ hybridization, and semiquantitative RT-PCR. TGF-beta1 and TGF-beta2 levels were measured in aqueous humor and serum of PEX and control patients by ELISA. Cultures of Tenon's capsule fibroblasts were established to study the effect of TGF-beta1 on fibrillin-1 mRNA expression by Northern blot analysis. Significantly increased concentrations of both total and active TGF-beta1 were measured in the aqueous humor of PEX eyes without and with glaucoma as compared to control eyes, whereas levels of TGF-beta2 were not significantly different. The expression of TGF-beta1, LTBP-1, and LTBP-2, but not TGF-beta2, was markedly increased in anterior segment tissues of PEX eyes, particularly in the non-pigmented epithelium of the ciliary body, on both the mRNA and the protein level. Latent TGF-beta1 staining was consistently associated with PEX material deposits and could be released by proteolytic processing. Double immunolabeling revealed clear co-localization of LTBP-1 and -2 with latent TGF-beta1 and with fibrillin-1 on PEX fibrils. The expression of mRNA coding for fibrillin-1 was up-regulated in vitro by TGF-beta1. This study provides evidence for a significant role of TGF-beta1 and the LTBPs 1 and 2 in PEX syndrome. The results suggest that increased levels of latent and active TGF-beta1 in the aqueous humor of PEX patients, derived from enhanced local synthesis and activation, promote the buildup of the abnormal extracellular elastic material characteristic of PEX syndrome. They further support a dual role for LTBPs, both as integral structural components of PEX fibers and as a means of matrix anchorage of latent TGF-beta1, representing one possible mechanism for the regulation of TGF-beta1 activity in PEX eyes. Future therapeutic strategies might focus on TGF-beta1 antagonistic approaches.

Membranous proliferation of lens epithelial cells on acrylic, silicone, and poly(methyl methacrylate) lenses

PURPOSE

To determine whether intraocular lens (IOL) material influences the membranous proliferation of lens epithelial cells (LECs) on the anterior surface of the IOL.

SETTING

Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan.

METHODS

This prospective study included 87 eyes of 87 consecutive patients who had cataract surgery with IOL implantation. Patients were randomly assigned to receive a single-piece poly(methyl methacrylate) (PMMA) IOL, a 3-piece silicone IOL, or a 3-piece acrylic IOL. Postoperatively, the IOL optic was examined by slitlamp microscopy at 1 and 10 days and 1, 2, and 3 months to determine the incidence, duration, and extent of membranous LEC proliferation. The optic was also examined at 6, 9, and 12 months if proliferation persisted.

RESULTS

Thirteen eyes were excluded from analysis because of incomplete coverage of the IOL rim by the anterior capsule margin; 74 remaining eyes were studied. All patients obtained good postoperative visual acuity (20/25 or better). Incidence (P =.0024) and duration (P =.0002) of membranous LEC proliferation with the acrylic IOL was greater than with the other 2 types. Proliferation on the acrylic IOL was more extensive than on the PMMA IOL 10 days postoperatively (P <.05) and on the silicone IOL at 10 days (P <.01) and 1 month (P <.01). However, LEC proliferation on the 3 types of IOLs usually decreased by the third postoperative month, and proliferation did not disturb visual acuity.

CONCLUSIONS

The material of an IOL influenced membranous proliferation of LECs on its anterior surface. Proliferation on the acrylic IOL persisted longer than on the other 2 types but did not cause visual symptoms.

Exfoliation syndrome

Exfoliation syndrome (XFS) is an age-related disease in which abnormal fibrillar extracellular material is produced and accumulates in many ocular tissues. Its ocular manifestations involve all of the structures of the anterior segment, as well as conjunctiva and orbital structures. Glaucoma occurs more commonly in eyes with XFS than in those without it; in fact, XFS has recently been recognized as the most common identifiable cause of glaucoma. Patients with XFS are also predisposed to develop angle-closure glaucoma, and glaucoma in XFS has a more serious clinical course and worse prognosis than primary open-angle glaucoma. There is increasing evidence for an etiological association of XFS with cataract formation, and possibly with retinal vein occlusion. XFS is now suspected to be a systemic disorder and has been associated preliminarily with transient ischemic attacks, stroke, systemic hypertension, and myocardial infarction. Further ramifications await discovery. Deposits of white material on the anterior lens surface are the most consistent and important diagnostic feature of XFS. The classic pattern consists of three distinct zones that become visible when the pupil is fully dilated. Whereas the classic picture of manifest XFS has been often described, the early stages of beginning exfoliation have not been well defined. Next to the lens, exfoliation material is most prominent at the pupillary border. Pigment loss from the iris sphincter region and its deposition on anterior chamber structures is a hallmark of XFS. Despite extensive research, the exact chemical composition of exfoliation material (XFM) remains unknown. An overproduction and abnormal metabolism of glycosaminoglycans have been suggested as one of the key changes in XFS. The protein components of XFM include both noncollagenous basement membrane components and epitopes of the elastic fiber system such as fibrillium. Regardless of etiology, typical exfoliation fibers have been demonstrated electron microscopically in close association with the pre-equatorial lens epithelium, the nonpigmented ciliary epithelium, the iris pigment epithelium, the corneal endothelium, the trabecular endothelium, and with almost all cell types of the iris stroma, such as fibrocytes, melanocytes, vascular endothelial cells, pericytes, and smooth muscle cells. The presence of XFS should alert the physician to the increased risks of intraocular surgery, most commonly zonular dehiscence, capsular rupture, and vitreous loss during cataract extraction. Heightened awareness of this condition and its associated clinical signs are important in the detection and management of glaucoma, and preoperative determination of those patients at increased risk for surgical complications.