Schwalbe's Line Research Articles

Anterior chamber angle evaluation with fourier-domain optical coherence tomography.

New advances in anterior segment optical coherence tomography (OCT) technology development allow visualizing the anterior chamber angle of the eye with high speed and high resolution. Fourier-domain (FD) OCT instruments working at 840 nm can reliably identify fine angle structures such as the Schwalbe's line. This paper demonstrates quantitative angle assessment with 840 nm FD-OCT and provides diagnostic cutoff values for occludable angle detection. This is useful for angle closure glaucoma diagnosis and management. Moreover, 840 nm FD-OCT is a useful tool for postsurgical evaluation in glaucoma patients.

Ocular signs in Wilson disease

A known patient of Wilson disease was admitted for fever. He was not on regular therapy for the same. His brother also suffered from the same illness. On examination, he had bilateral sunflower cataracts and Kayser-Fleischer (KF) rings [Figure 1]. He also had bilateral rigidity and batwing tremor.Figure 1: Sunflower cataract and Kayser-Fleischer ringWilson disease is an autosomal-recessive disorder of copper metabolism due to mutation of the ATP7B gene in chromosome 13 (13q14.3). Ocular signs of Wilson disease are sunflower cataract and KF rings. Sunflower cataract was first described by Siemerling and Oloff in 1922.[1] It occurs due to copper deposition in the anterior capsule. Posterior capsule deposition appears to be uniform. The sunflower consists of a central disc with radiating folds at the periphery. The radiating folds are thought to be due to the impression of the posterior surface of the iris on the anterior lens capsule, as proposed by Duke-Elder. The shape of the sunflower may be distorted if there is pupillary abnormality. This mechanism may not fully explain the sunflower shape as this appearance can also occur in the posterior capsule. Sunflower cataract has been reported to occur in other conditions like intraocular copper bodies (chalcosis) and primary biliary cirrhosis, and have been shown to regress either partially or completely following penicillamine therapy. Hereditary hyperferritinemia cataract syndrome (HHCS) is a newly described autosomal-dominant disorder characterized by early-onset cataracts and increased serum L-ferritin concentration, but without iron overload. These cataracts have a characteristic sunflower-like appearance and are due to crystalline deposition of ferritin.[2] KF was described by the German ophthalmologists Bernhard Kayser in 1902 and Bruno Fleischer in 1903.[3] This is not to be confused with Fleicher ring, seen in Keratoconus, which is due to iron deposition in the corneal limbus. KF ring is due to copper deposition in the descemet membrane of the cornea at the limbus. It starts from the Schwalbe line and extends till 5 mm on the corneal surface. It starts in the superior pole as an arc from the 10- to the 2 o’clock position, followed by a similar arc in the inferior pole, and finally encircles the cornea.[4] Free copper loosely bound to albumin enters the aqueous humor and then enters the descemet membrane. The peripheral deposition is attributed to the direction of the aqueous humor.[5] KF rings are usually detected by slit lamp examination, but can also be visible to the naked eye and do not obstruct vision. KF ring is seen in 95% of the patients with neurological manifestations and 65% with liver dysfunction. KF rings can also occur in intraocular copper bodies (chalcosis) and primary biliary cirrhosis. The ring resolves in the reverse order either completely or partially following penicillamine therapy[5] and after liver transplant.

Automatic Anterior Chamber Angle Assessment for HD-OCT Images

Angle-closure glaucoma is a major blinding eye disease and could be detected by measuring the anterior chamber angle in the human eyes. High-definition OCT (Cirrus HD-OCT) is an emerging noninvasive, high-speed, and high-resolution imaging modality for the anterior segment of the eye. Here, we propose a novel algorithm which automatically detects a new landmark, Schwalbe's line, and measures the anterior chamber angle in the HD-OCT images. The distortion caused by refraction is corrected by dewarping the HD-OCT images, and three biometric measurements are defined to quantitatively assess the anterior chamber angle. The proposed algorithm was tested on 40 HD-OCT images of the eye and provided accurate measurements in about 1 second.

Iridocorneal Endothelial Syndrome in a 16-Year-Old

We report iridocorneal endothelial syndrome in a male who presented at the age of 16 years with a 3-year history of complaints of blurred vision, altered pupillary shape, and monocular diplopia OD. The examination was notable for unilateral effacement of the iris architecture, stretch holes, corectopia, and localized ectropion uveae. Intraocular pressures were 41 mm Hg OD and 10 mm Hg OS. Gonioscopy revealed intermittent areas of broad synechiae anterior to Schwalbe's line alternating with a clinically normal appearance. The left eye and angle were unremarkable. Specular microscopy confirmed the presence of unilateral endothelial pleomorphism and polymegathism. To our knowledge, this is the earliest reported case of iridocorneal endothelial syndrome in a young man.

Anterior chamber angle imaging with optical coherence tomography

The technology of optical coherence tomography (OCT) has evolved rapidly from time-domain to spectral-domain and swept-source OCT over the recent years. OCT has become an important tool for assessment of the anterior chamber angle and detection of angle closure. Improvement in image resolution and scan speed of OCT has facilitated a more detailed and comprehensive analysis of the anterior chamber angle. It is now possible to examine Schwalbe's line and Schlemm's canal along with the scleral spur. High-speed imaging allows evaluation of the angle in 360°. With three-dimensional reconstruction, visualization of the iris profiles and the angle configurations is enhanced. This article summarizes the development and application of OCT for anterior chamber angle measurement, detection of angle closure, and investigation of the pathophysiology of primary angle closure.

Unusual presentation in Axenfeld-Rieger syndrome

We report an unusual presentation of a case of Axenfeld-Rieger (A-R) syndrome. A 14-year-old male presented with gradual dimness of vision for 1 year and redness of left eye for 3 days. The patient had megalocornea with Haab's striae in the right eye and posterior embryotoxon in both the eyes. In the left eye, there was a white cord-like structure traversing the anterior chamber with adhesions to iris tissue along its course. On two antiglaucoma medications, his intraocular pressure (IOP) was 22 mm Hg in the right eye and 18 mm Hg in the left eye. Gonioscopy revealed a cord-like structure originating at the level of Schwalbe's line. He underwent right eye trabeculectomy with mitomycin-C. This case highlights a rare presentation of a strange cord-like structure, a rare presentation of A-R syndrome.

Novel anterior-chamber angle measurements by high-definition optical coherence tomography using the Schwalbe line as the landmark

ObjectiveTo propose the Schwalbe line (SL) as a new anatomical landmark, independent of the scleral spur (SS) location, for assessing anterior chamber angle (ACA) width quantitatively with high-definition optical coherence...

Axenfeld-Rieger Syndrome Associated with Congenital Glaucoma and Cytochrome P4501B1 Gene Mutations

Developmental anomalies of the ocular anterior chamber angle may lead to an incomplete development of the structures that form the conventional aqueous outflow pathway. Thus, disorders that present with such dysfunction tend to be associated with glaucoma. Among them, Axenfeld-Rieger (ARS) malformation is a rare clinical entity with an estimated prevalence of one in every 200,000 individuals. The changes in eye morphogenesis in ARS are highly penetrant and are associated with 50% risk of development of glaucoma. Mutations in the cytochrome P4501B1 (CYP1B1) gene have been reported to be associated with primary congenital glaucoma and other forms of glaucoma and mutations in pituitary homeobox 2 (PITX2) gene have been identified in ARS in various studies. This case was negative for PITX2 mutations and compound heterozygote for CYP1B1 mutations. Clinical manifestations of this patient include bilateral elevated intraocular pressure (>40 mmHg) with increased corneal diameter (>14 mm) and corneal opacity. Patient also had iridocorneal adhesions, anteriorly displaced Schwalbe line, anterior insertion of iris, broad nasal bridge and protruding umbilicus. This is the first study from north India reporting CYP1B1 mutations in Axenfeld-Rieger syndrome with bilateral buphthalmos and early onset glaucoma. Result of this study supports the role of CYP1B1 as a causative gene in ASD disorders and its role in oculogenesis.

Rectification of Width and Area of the Ciliary Cleft in Dogs

The width and area of the ciliary cleft (CCW and CCA) according to ultrasound biomicroscopy was rectified to compare dogs of different body sizes/weights, including toy breed (TBG), small breed (SBG), medium breed (MBG) and large/giant breed groups (LGBG). A linear correlation was detected between the natural log of body weight and the ocular axial length (OAL) reflecting the ocular size (OS; r=0.81, p<0.001). A significant positive correlation was found between OAL and the distance of the Schwalbe's line to the anterior lenticular capsule (SLD; r=0.87, p<0.001), suggesting that SLD could rectify canine OS. Rectified CCW (r-CCW) and CCA (r-CCA) were calculated using SLD and fixed SLD as the SLD mean (SLDM). The SLDM was 2.55 mm in this study, and r-CCW and r-CCA were calculated as r-CCW = CCW x (2.55/SLD) and r-CCA = CCA x (2.55/SLD)(2). The CCW values of TBG, SBG and MBG were narrower than those of LGBG (p<0.05). There were significant statistical differences in CCA between all groups other than TBG and SBG (p<0.05). There were no significant differences in r-CCW and r-CCA in any of the groups. In addition, CCW/SLD did not show significant changes in dogs with different body sizes/weights. These results suggested that r-CCW, r-CCA and CCW/SLD can be used for comparison between dogs of different body sizes/weights.

High-Definition Optical Coherence Tomography Imaging of the Iridocorneal Angle of the Eye

To assess the ability of high-definition optical coherence tomography (HD-OCT) to image the anterior chamber angle. Forty-five consecutive subjects with phakic eyes underwent gonioscopy and anterior chamber angle imaging with HD-OCT adapted with a 60-diopter aspheric lens mounted over the imaging aperture. The patients' fixation was directed to the side using an external fixation light, and scans were taken of the temporal and nasal quadrants. The visibility of angle structures was assessed and the diagnosis of angle closure using HD-OCT was compared with that of gonioscopy. The majority of subjects were Chinese (91.1%) and female (62.2%). Cross-sectional HD-OCT allowed in vivo visualization of the scleral spur in 71 of 90 quadrants (78.9%) and the termination of the Descemet membrane (Schwalbe line) in 84 of 90 quadrants (93.3%). It was possible to image the trabecular meshwork in 56 quadrants (62.2%). Angle closure was observed in 17 eyes with gonioscopy and 12 eyes with HD-OCT (P = .12, McNemar test). The 2 modalities showed good agreement for angle closure diagnosis by quadrant (kappa = 0.65). The adapted HD-OCT provided magnified views of the anterior chamber angle and allowed visualization of the Schwalbe line and trabecular meshwork in most eyes.

Prognostic Value of Gonioscopy after Deep Sclerectomy

To ascertain gonioscopic characteristics and identify prognostic indicators related to intraocular pressure (IOP) after deep sclerectomy (DS). A transversal, prospective, and nonselected study was performed in 106 eyes (95 patients) after DS. Three surgeons performed all the surgeries and the gonioscopic examination, using the same protocol including 13 gonioscopic data. These data were evaluated for an association with postoperative IOP and time after surgery. A subscleral space was found in 91 eyes (85.8%), with visualization of the line of scleral flap in 48 eyes (45.3%). The trabeculo-Descemet membrane (TDM) was transparent in 46 eyes (43.4%), opaque in 4 cases, and pigmented in 18 eyes. This TDM was broken using Nd:YAG laser goniopuncture in 38 eyes(35.8%). Thin vessels around TDM were found in 58 eyes (54.7%), and blood remained in 25 eyes (23.5%). Gonioscopic variables significantly positively related with postoperative IOP were as follows: presence of subscleral space, scleral flap line view, and a Schwalbe line depressed. A narrow anterior chamber angle and iris synechia in TDM had a statistically significant negative effect on the postoperative IOP control. Similarly, eyes requiring Nd:YAG goniopuncture had a worse IOP control. The frequency of eyes with visible subscleral space and transparent TDM decreases with time after surgery (p=0.001). A visible subscleral space was a gonioscopic sign positively related to IOP control after surgery, although it decreased with follow-up. Eyes with goniopuncture, postoperative narrow angle, and iris synechia had worse postoperative IOP control. Although new vessels in TDM were a common finding after DS, the authors did not find any association with postoperative IOP.

Intrastromal Diathermal Keratostomy: A New Micropenetrating Clear-Cornea Glaucoma Procedure

The filtering intrastromal diathermal keratostomy (IDK) was developed to comply with the call for a low postoperative intraocular pressure (IOP) and a bleb morphology without a thin, cystic appearance. A diathermal microkeratostomy (150 to 200 microm) was created into the anterior chamber, anterior to the Schwalbe line through the floor of a surgical corneoscleral tunnel incision into the subconjunctival space. A newly developed, bipolar diathermal microneedle was used to create the keratostomy, replacing the Holmium laser used previously. Subconjunctival injections of 3 microg mitomycin C were used in each eye 1 week before the IDK to obtain maximum antiproliferative effect at the time of the operation. Nine patients (10 eyes) with complicated, refractory primary and secondary open-angle glaucoma are discussed. Histologic examination of the IDK and clinical postoperative ultrasound biomicroscopy showed an optimal appearance of the diathermal microkeratostomy. After 34 months (range 24 to 42 mo) the mean IOP was 11 mm Hg (SD+/-3, range 6 to 16) without medication in all 10 eyes. IDK revision with internal needling of postoperative subconjunctival fibrosis through the tunnel incision was performed in 5 eyes after an average of 3 months (range 0.2 to 7 mo). After 33 months (range 19 to 38 mo), the postrevision mean IOP was 10 mm Hg (SD+/-2, range 8 to 14) without medication in all 5 eyes. All 10 eyes showed noncystic diffuse blebs with optimal spongy subepithelial morphology: in 2 eyes the blebs were totally avascular and in 8 eyes they were relatively avascular. The preliminary results of the new clear-cornea IDK seem promising because of postoperative IOP of about 10 mm Hg despite a low dose of mitomycin C and noncystic bleb morphology.

Prevalence and mechanism of appositional angle closure in acute primary angle closure after iridotomy

A prospective observational case series to assess the prevalence of appositional angle closure in darkness among iridotomized Chinese eyes after acute primary angle closure (APAC) with the use of both clinical methods and ultrasound biomicroscopy. Sixteen Chinese patients who had history of APAC and subsequent successful treatment with laser peripheral iridotomy were examined. Fourteen additional control subjects were studied. Gonioscopy and ultrasound biomicroscopic examination were performed in the dark. Gonioscopic appearance of the angle was assessed, and quantitative measurements of the angle from the ultrasound biomicroscopic images were taken. Of the APAC eyes 55.6% had appositionally closed angle clinically and in 38.9% only Schwalbe's line was visible on gonioscopy. Ultrasound biomicroscopy confirmed structurally different anterior segments between eyes with APAC and the control eyes. In particular, the trabecular-ciliary-process distances were markedly different between the two groups. This study documented a high prevalence of appositional closure in iridotomized eyes after APAC in Chinese patients. The anteriorly positioned ciliary body, as documented in these cases by ultrasound biomicroscopy, is the likely mechanism of the angle crowding in this patient population.

A technique to harvest Descemet’s membrane with viable endothelial cells for selective transplantation

To describe a surgical technique using an artificial anterior chamber to facilitate harvest of Descemet's membrane (DM) and endothelium for corneal endothelial cell transplantation. Laboratory investigation. Corneoscleral buttons of seven human donor eyes were mounted endothelial side up on an artificial anterior chamber. Keeping the endothelial side with its usual concavity, a manual trephination was made on the posterior surface with a 9.0-mm trephine, inside the Schwalbe line and just past the DM in depth. The chamber was filled with air, causing the endothelial side of the donor cornea to assume a convex configuration. The DM along with its endothelium was separated from the posterior stroma using a blunt cyclodialysis spatula. Drops of trypan blue 0.3% and alizarin red S 0.2% (n = 6) were applied. The stained DMs were examined under a light microscope and photographed to calculate the percentage of endothelial cell damage. Histology was done on the unstained cornea. The DM carrying endothelium was successfully removed from the posterior stroma in all seven eyes. Although the DM appears to be very friable, all samples were removed in toto without rupture. Vital staining showed a mean endothelial cell loss of 8.46% (standard deviation (SD) 6.9). Direct light microscopy demonstrated the preservation of endothelial cell morphology. This technique appears to be a safe and straightforward method to harvest DM for endothelial cell transplantation. Further studies are underway to determine the optimal method of insertion of the obtained healthy DM with endothelial cells through small corneal incisions.

Posterior embryotoxon may not be a forme fruste of Axenfeld-Rieger’s Syndrome

Axenfeld-Rieger Syndrome is a disorder of morphogenesis which is autosomal dominantly inherited. One of the main ocular features associated with Axenfeld-Rieger is posterior embryotoxon, which is a prominent anteriorly displaced Schwalbe's line. This can be found in up to 15% of normal eyes, without any clinical significance or may represent a forme fruste of an anterior segment dysgenesis. Many large case series studies of Axenfeld-Rieger had used the presence of posterior embryotoxon with iris strands extending from the peripheral iris to Schwalbe's line, as inclusion criterion for this condition. We report a case of Axenfeld-Rieger syndrome without posterior embryotoxon and the abnormalities of the angle, but with other features to support the diagnosis of Axenfeld-Rieger Syndrome.

Immunolocalization of prostanoid EP receptor isotypes in human trabecular meshwork

Purpose. To assess the localization of the EP-type prostanoid receptors in the human trabecular meshwork (TM) and to determine their spatial distribution in relation to the contractile α-smooth muscle actin fibres.Methods. Cryosections of human anterior segments were obtained from 17 different donors and immunostained with different EP receptor subtype specific antibodies. Double staining for the EP2 receptor and smooth muscle actin was carried out. Western blots of TM protein samples were studied.Results. No specific staining for the EP1 receptor was observed. The antibodies against the EP2 receptor revealed in all donors intense staining of human trabecular cells throughout the meshwork. EP3 receptor specific staining was not detected. EP4 immunostaining was confined to the corneo-scleral region near Schwalbe's line. On western blots, the EP2 receptor was detected. In the posterior TM, the EP2 receptor staining was associated with the dense network of actin fibres.Conclusions. These immunocytochemical results present evidence that the EP2 receptor is the most abundantly expressed isotype of the PGE receptors in the human TM. This conclusion is in agreement with our previous findings at the transcript level. The relaxant responses of the TM to application of EP2 receptor agonists, and flow enhancement evoked by prostaglandin PGE1, may be explained by the close spatial association of the EP2 receptor with actin fibres.

The efficacy of latanoprost is independent of the width of the ciliary body face. Ritch R, Ishikawa H, Rothman R, Yu G, Liebmann JM. J Glaucoma 2002;11:239 -243.

In a prospective clinical trial, the relationship between the intraocular pressure-lowering efficacy of latanoprost 0.005% and the height of the ciliary body face exposed to the anterior chamber was assessed in untreated, latanoprost-naive patients with ocular hypertension or open-angle glaucoma. Fifty-four eyes (54 patients) were enrolled. The mean age of participants was 60.2 (±13.9) years. A radial, perpendicular ultrasound biomicroscopy image at the 6-o’clock position detailing the Schwalbe line, scleral spur, and iris insertion was obtained. The distance between these structures was measured and their relationship to the intraocular lowering pressure of latanoprost at 1, 2, 3, and 6 months was analyzed. The mean height of the trabecular meshwork was 0.72 (±0.1) mm and the mean height of exposed ciliary body face was 0.14 (±0.08) mm. The mean pretreatment intraocular pressure was 26.4 (±3.8) mm Hg. The mean pressure reduction from baseline was 7.1, 7.3, 7.8 and 7.7 mm Hg at 1, 2, 3 and 6 months, respectively. There was significant correlation between intraocular pressure lowering and the trabecular meshwork height at 1 month (P < 0.05) but not at 2, 3, or 6 months. There was no statistically significant correlation between intraocular pressure lowering and the height of exposed ciliary face. Although latanoprost lowers intraocular pressure by enhancing uveoscleral outflow, its efficacy is independent of the width of the ciliary body exposed to the anterior chamber.—Michael D. Wagoner

Corneal Myxoma

Background: Myxomas are rare benign tumors that can be found most frequently in the heart. We report the clinical and histological findings in a very rare case of corneal myxoma, which is only the sixth case in the literature. Case: A whitish elevated tumor of the anterior cornea developed in the left eye cornea of a 46-year-old man 2 years after luxation of the patient's lens into the anterior chamber and subsequent endothelial decompensation. The tumor covered the entire surface of the cornea except for the outer limbal periphery at Schwalbe's line. Observations: Histologically, the hypocellular tumor was characterized by scattered spindle- and stellate-shaped cells with wavy, randomly oriented collagen fibers in a myxomatous ground substance staining positively for acid mucopolysaccharides. Bowman's layer was absent. Immunohistochemically, the tumor cells were positive for vimentin. Ultrastructurally, the tumor cells had features characteristic of keratocytes with no basement membrane, much rough endoplasmic reticulum and vacuoles containing mucoid-like material. Conclusions: The ultrastructural observations support the hypothesis of a cellular origin of the myxoma from keratocytes. The tumor growth was most probably stimulated by chronic endothelial failure and bullous keratopathy.

Anterior Chamber Angle Anomalies Associated with Signs of Pigment Dispersion in a Group of Black Probands and Their First-Degree Relatives

To evaluate the presence of iridocorneal angle anomalies associated with signs of pigment dispersion among a group of black probands and their first-degree relatives. Eleven blacks who exhibited pigment dispersion syndrome (PDS) signs, including Krukenberg's spindles, moderate-to-heavy trabecular meshwork pigmentation, and peripheral lenticular/zonular pigmentation, received a complete eye examination that included gonioscopy. Overt iridocorneal angle abnormalities other than pigment deposition were photo-documented. Twenty-two first-degree relatives (6 siblings, 15 children, and 1 parent) of these probands underwent similar examination. Among the subjects, 5 of 11 probands (age range 13 to 59 years) and 4 of 22 relatives (age range 14 to 51 years) exhibited definite angle anomalies. The nine subjects with angle anomalies belonged to 7 of 11 separate families. The four relatives with angle anomalies did not have PDS according to our criteria, but two other relatives from two additional families did have signs consistent with clinical PDS. Types of angle anomalies included (1) peripheral anterior synechia-like lesions; (2) a prominent concavity of the peripheral iris at the 6-o'clock meridian; (3) a whitish, thread-like band of tissue near the iris base; (4) a prominent, externally-visible Schwalbe's line at the 6-o'clock meridian; and (5) a prominent, web-like confluence of exaggerated iris processes 360 degrees along the angle wall. Iris processes and prominent Schwalbe's lines were not considered abnormal or anomalous unless they were clearly atypical. Iridocorneal angle anomalies, other than pigment deposition, were common among our black group who exhibited signs of pigment dispersion as well as among their first-degree relatives. Further consideration should be given to the possibility that among some patient groups, overt goniodysgenesis could be part of a constellation of signs indicative of a pigment dispersion syndrome. Potentially, clinically detectable goniodysgenesis could prove to be a useful marker to identify certain subjects who carry PDS genetic traits but who have not expressed complete phenotypical disease.

Schwalbe line's cell in the normal and glaucomatous dog.

The canine iridocorneal angle contains an operculum, which is similar to that in nonhuman primates and consists of a peripheral extension of the inner cornea that overlies the anterior-most portion of the corneoscleral trabecular meshwork. This region contains cells, the Schwalbe line's (SL) cells, that have been found to have secretory and epithelial characteristics. This region of the iridocorneal angle represents the nonfiltering portion and becomes altered early during spontaneous glaucoma in the Beagle. The present study describes the SL cell for the first time in the dog and changes associated with canine primary open angle glaucoma. The iridocorneal angles from 18 Beagles with inherited glaucoma (3 months-8 years old) and 17 normal, age-matched Beagles were placed in 10% buffered formalin for light microscopic evaluation, or 2.5% glutaraldehyde for ultrastructural evaluation. Using at least three fields from each region of the iridocorneal angle (opercular, corneoscleral, and uveal) at x 1000 magnification, trabecular cell nuclei were counted. The operculum in the canine iridocorneal angle consisted of the peripheral extension of the corneal endothelium and underlying anterior-most corneoscleral meshwork, having no direct contact with the angular aqueous plexus. The SL cells associated with operculum-retained epithelial morphology (polyhedral in shape with rER, Golgi apparatus, and secretory vesicles) in both normal, pre-and early glaucomatous dogs. In animals with moderate and advanced stages the SL cells often became less epithelial and secretory in appearance. The number of SL cells in normal dogs declined by approximately one-third by the end of their first year with gradual loss thereafter. In the glaucoma group the decline was more substantial and continuous through the first three years. The SL cell is morphologically a distinct cell type within the canine iridocorneal angle that is specifically associated with the nonfiltering portion of the corneoscleral trabecular meshwork. Changes in the SL cells of the glaucomatous dog occurred with regard to age and progression of the disease.