Conjunctival Vasculature Research Articles

Impact of scleral cautery on limbal vasculature after cataract surgery assessed using optical coherence tomography angiography.

We investigate the influence of scleral cautery during cataract surgery on limbal vascular density and remodeling using anterior segment optical coherence tomography angiography (AS-OCTA). Twenty eyes of 20 patients who underwent cataract surgery with a sclerocorneal incision were included. Patients were divided into two groups: non-cautery (n = 10) and cautery (n = 10). The area around the incision site was scanned using AS-OCTA before surgery and at 1, 3, 5, 7, 14, 21, 28, and 90 days postoperatively. Images were analyzed to depict conjunctival vasculature (surface to a depth of 200μm) and intrascleral vasculature (depth of 200 to 1000μm). Vascular density was evaluated using ImageJ software. In the non-cautery group, intrascleral vascular density significantly increased during the wound-healing period up to 21 days postoperatively. Cautery application completely diminished this effect, resulting in significantly reduced intrascleral vascular density in the cautery group compared to the non-cautery group until 5 days after surgery. On the seventh day and later, intrascleral vascular density in the cautery group recovered, but the vascular pattern did not return to its preoperative state even at 90 days after surgery. Conjunctival flap vascular density was reduced for 28 days after surgery, with cautery application further decreasing conjunctival vascular density. AS-OCTA enabled separate observation of conjunctival and intrascleral vasculature. Intrascleral blood flow significantly increased after cataract surgery, but scleral cauterization markedly blocked this effect. The vascular reconstruction process following cataract surgery continued for almost a month, with cautery application leading to prolonged vascular disruption and altered vascular patterns.

Eyes, menstruation and endometriosis.

Vicarious menstruation refers to cyclical bleeding outside the uterine cavity during the menstrual cycle. Haemolacria, or blood in tears, is a rare medical phenomenon that can occur with menstruation or in association with endometriosis. Endometriosis, defined by the presence of endometrial-like tissue in extra-uterine sites, affects around 10% of fertile women; the ocular system is one of the rarest sites it can be present in. Endometriosis usually requires a biopsy for diagnosis, and the anatomic difficulty of obtaining a biopsy of the ocular system makes ocular endometriosis diagnosis more obscure. However, few cases have been described in the literature and due to the psychological, physical, and social implications of haemolacria on the patient, treatment is of utmost importance. We reviewed the literature on ocular endometriosis and ocular vicarious menstruation with the aim to discuss the clinical presentation, necessary workup and various treatment modalities, while also shedding light on the connection between the eyes and endometriosis in general. It is hypothesised that uterine endometrial cells can travel lymphatically or haematogenously and deposit extra-uterine endometriotic lesions that bleed in response to hormonal changes in the menstrual cycle. Additionally, the conjunctival vasculature has been found to be responsive to hormonal changes due to the presence of oestrogen and progesterone receptors, causing bleeding at the corresponding sites, even without endometriotic lesions. Clinical correlation of the haemolacria with the menstrual cycle can suffice for a diagnosis of vicarious menstruation, and thus opens the possibility of treatment to provide symptomatic treatment for the patient.

INOCA affects more than the coronaries

Abstract Background Ischaemia with normal coronary arteries (INOCA) may result in disabling symptoms and has an association with adverse long-term prognosis. The diagnosis of INOCA necessitates invasive coronary angiography to perform a physiological evaluation of microvascular function. The conjunctiva has a readily assessable microvascular network in which physiological parameters can be evaluated. We compared conjunctival haemodynamics in patients with and without coronary microvascular disease (MVD) to assess if systemic microvascular dysfunction was present in this coronary artery disease sub-group. Methods In this study, we recruited patients undergoing invasive coronary angiography for the investigation of angina or angina equivalent symptoms. All patients had physiologically insignificant epicardial disease (FFR≥0.80) and underwent a physiological evaluation of coronary microvascular function. We compared a group with evidence of coronary MVD (IMR≥25 or CFR<2.0); to a group of controls without MVD (IMR<25 and CFR≥2.0). The conjunctival microvasculature was imaged using a previously validated combination of a smartphone and slit-lamp biomicroscope. The conjunctival vasculature was assessed using a semi-automated process of vessel diameter measurement and erythrocyte tracking to obtain haemodynamic parameters of microvascular function. Results A total of 111 patients were included (43 MVD and 68 controls). There were no differences in baseline demographics, co-morbidities, epicardial coronary disease severity or regular pharmacological therapies between the groups. Mean coronary flow reserve (CFR) was lower and mean index of microcirculatory resistance (IMR) higher in the MVD cohort (CFR 2.5±1.3 vs 5.2±2.5, p<0.001 and IMR 28.4±11.8 vs 13.7±5.0, p<0.001). A total of 2295 conjunctival vessels were analysed. The mean number of vessels per patient was 21.0±12.8 (3.2±3.5 arterioles and 14.8±10.8 venules). Significant reductions in axial/cross-sectional velocity, wall shear rate and wall shear stress were observed in the MVD cohort. Table 1 demonstrates a comparison of conjunctival physiological parameters between the groups. The most marked differences were observed in conjunctival arterioles. Due to the heterogenous size distribution of microvessels, arterioles were categorised into 2 diameter sub-groups (10–25 μm and 25–40 μm) for analysis (Table 2). Conclusion The reductions in microvascular blood flow velocity and rate that form the basis for the diagnosis of coronary microvascular dysfunction can be observed non-invasively in the bulbar conjunctiva microcirculation. Conjunctival vascular imaging may have utility as a non-invasive imaging modality to both diagnose microvascular dysfunction and augment conventional cardiovascular risk stratification. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): Belfast Trust Heart Trust Fund and Northern Ireland Chest Heart and Stroke

Effect of peripheral iridectomy on VEGF-A and TGF-\u03b2 levels in rabbit aqueous humour

BackgroundPeripheral iridectomy (PI), routinely performed during glaucoma filtration surgery, may contribute to scarring. This study aims to determine whether PI alters the concentrations of VEGF-A and TGF-β isoforms in the rabbit aqueous humour.MethodsAnterior chamber paracentesis (ACP) was performed in both eyes of six New Zealand white rabbits, with additional surgical PI performed in the right eyes. Eyes were examined on postoperative days (PODs) 1, 7, 30 and 60 by means of the tonopen, slit-lamp biomicroscopy, and bead-based cytokine assays for TGF-β and VEGF-A concentrations in the aqueous humor.ResultsACP caused a significant reduction in intraocular pressure (IOP) from mean preoperative 11.47 ± 1.01 mmHg to 5.67 ± 1.63 mmHg on POD 1 while PI did not cause further IOP reduction. Limbal conjunctival vasculature appeared slightly increased on POD 1 in both ACP and PI eyes with PI also causing mild bleeding from damaged iris vessels. Two PI eyes developed fibrinous anterior chamber reaction and/ or peripheral anterior synechiae. Aqueous VEGF-A levels were not significantly different between eyes treated with ACP and PI. Aqueous TGF-β concentrations distributed in the ratio of 4:800:1 for TGF-β1:TGF-β2:TGF-β3 respectively. While aqueous TGF-β2 was not significantly induced by either procedure at any time point, TGF-β1 and TGF-β3 were significantly induced above baseline levels by PI on POD 1.ConclusionPI increases the risk of inflammation. The combined induction of aqueous TGF-β1 and TGF-β3 by PI in glaucoma surgery may impact surgery success in glaucoma subtypes sensitive to these isoforms.

ANALYSIS OF CONJUNCTIVAL VASCULAR DENSITY IN SCLERAL CONTACT LENS WEARERS USING OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

PurposeTo investigate conjunctival vascular density (VD) using Anterior Segment Optical Coherence Tomography Angiography (OCTA) in Scleral Contact Lens (ScCL) wearers. MethodsIn this cross-sectional study, the conjunctival blood VD was assessed using OCTA with an anterior segment lens adapter. The nasal surface of each eye (6 ×6 mm) was scanned to a depth of 800 μm with ScCL and fifteen minutes after removing the lens. Conjunctival VD was defined as the percentage of the scanned volume occupied by vessels in which blood flow was measured. Measures of limbal indentation were subjectively determined by two independent observers using Anterior Segment Optical Coherence Tomography (AS-OCT). Comparisons between VD measurements before and after ScCL removal and correlations between conjunctival VD, time of use, vault and indentation values were also investigated. ResultsA total of 23 patients (3 females, 20 males) with keratoconus, with a mean age (years±SD) of 38.74±10.38 were included in the study. VD was significantly higher without ScCL (71.75%±2.97) than VD measured with ScCL (69.81%±2.63), p=0.02. A moderately negative correlation was found between indentation and vault (r=-0.44, p<0.05) and a positive tendency regarding the time of wearing ScCL and indentation (r=0.11 and r=0.068, respectively). ConclusionsUsing OCTA with an anterior segment lens adapter, the ocular surface blood VD was imaged and assessed with good repeatability and reliability. This study presents a new possible application of OCTA to investigate and monitor conjunctival vasculature in ScCL wearers. This results cautiously suggest that the repeated use of ScCL can cause vascular alterations in conjunctiva of the eyes of ScCL wearers, possibly due to a hidden hypoxia caused by prolonged limbal indentation.

Albumin Levels in Tear Film Modulate the Bioavailability of Medically-Relevant Topical Drugs.

The breakdown of blood-tear barrier that occurs with ocular pathology allows for large amounts of albumin to leak into the tear fluid. This process likely represents an important restriction to drug absorption in ophthalmology, as only the unbound drug is transported across the ocular tissue barriers to exert its pharmacologic effect. We aimed to investigate the effects of albumin levels in tears on the bioavailability of two commonly used ophthalmic drugs: tropicamide, an antimuscarinic that produces mydriasis and cycloplegia, and latanoprost, a PGF2α analog used for the treatment of glaucoma. Eight female beagle dogs underwent a randomized, vehicle-controlled crossover trial. For each dog, one eye received 30 µl of artificial tears (control) or canine albumin (0.4 or 1.5%) at random, immediately followed by 30 µl of 1% tropicamide (2 days, 24 h washout) or 0.005% latanoprost (2 days, 72 h washout) in both eyes. Pupil diameter (digital caliper) and intraocular pressure (IOP; rebound tonometry) were recorded at various times following drug administration (0 to 480 min) and compared between both groups with a mixed model for repeated measures. Albumin in tears had a significant impact on pupillary diameter for both tropicamide (P ≤ 0.001) and latanoprost (P ≤ 0.047), with no differences noted between 0.4% and 1.5% concentrations. Reduction in the maximal effect (pupil size) and overall drug exposure (area under the effect time-curve of pupil size over time) were significant for tropicamide (6.2–8.5% on average, P ≤ 0.006) but not for latanoprost (P ≥ 0.663). The IOP, only measured in eyes receiving latanoprost, was not significantly impacted by the addition of either 0.4% (P = 0.242) or 1.5% albumin (P = 0.879). Albumin in tear film, previously shown to leak from the conjunctival vasculature in diseased eyes, may bind to topically administered drugs and reduces their intraocular penetration and bioavailability. Further investigations in clinical patients and other commonly used ophthalmic medications are warranted.

Conjunctival Redness Response to Corneal Stimulation.

The conjunctiva is an integral component of the ocular surface, and its vasculature forms a terminal vascular bed of the human internal carotid artery. No research on the response of conjunctival vasculature to ocular surface stimulation exists; however, it is essential to understand the local physiological and pathological responses to such a stimulus. The purpose of this study was to characterize the ocular redness levels in healthy participants after the application of noxious corneal stimulation. A computerized Belmonte pneumatic esthesiometer was used to determine detection thresholds (using ascending method of limits) and to randomly deliver mechanical and chemical stimuli from levels of detection threshold to twice the threshold in 50% steps to the central cornea of 15 healthy subjects. For each suprathreshold stimulus, a spectrophotometer was used to measure ipsilateral and contralateral conjunctival redness before and after delivery of the corneal stimulus. Redness between the stimulated and unstimulated eyes was analyzed using dependent t tests. The effects of stimulus intensity and modality on conjunctival redness were analyzed using repeated-measures analysis of variance (ANOVA). Tukey honestly significant difference tests were used for all post hoc analyses. P ≤ .05 was considered statistically significant. In mechanical and chemical stimulation experiments, the stimulated eye became redder than the unstimulated eye (all t tests, P > .05). On average, redness increased from baseline as the corneal stimulus intensity increased with corneal stimulation (ANOVA, P < .05). Chemical stimulation produced greater conjunctival redness than did mechanical stimulation at all stimulation levels (ANOVA, P < .05; all Tukey honestly significant difference tests, P < .05). Stimulation of the central cornea by noxious mechanical and chemical stimuli evokes a dose-dependent autonomic conjunctival redness response. Chemical stimulation of the cornea seems to evoke a greater response compared with mechanical stimulation. This study serves as a basis for the characterization of the local stimulus-response neural circuitry relating nociceptive ocular surface stimuli to autonomic responses.

Quantitative Analysis of Conjunctival and Retinal Vessels in Fabry Disease.

Fabry Disease (FD) is a rare X-linked lysosomal storage disorder characterized by systemic and ocular involvement. It has been described an increasing in retinal and conjunctival vessel tortuosity and this feature represents an important marker for the disease. Currently, there is not an objective method to measure and quantify this parameter. We tested a new semi-automatic software measuring retinal and conjunctival vessel tortuosity from eye fundus and conjunctival digital images in a group of FD patients. We performed an observational case-control study evaluating three mathematical parameters describing tortuosity (sum of angle metric [SOAM], product of angle distance [PAD], triangular index [I2e]) obtained from fundus and conjunctival pictures of 11 FD patients and 11 age and sex-matched controls. Both eyes were considered. Mann–Whitney test was used to compare the FD group versus the control group and, within the FD group, male versus female patients. Linear regression analysis was performed to evaluate the possible association of retinal and conjunctival vessels tortuosity parameters with age and with specific markers of systemic disease's progression. The tortuosity parameters (SOAM, PAD and I2e) were significantly higher in retinal vessels and in conjunctival nasal vessels in FD patients in comparison with the controls (p=0.003, p=0.002, p=0.001 respectively for retina) (p=0.023, p=0.014, p=0.001 respectively for nasal conjunctiva). No significant association was found between retinal and conjunctival tortuosity parameters and increasing age or systemic involvement markers. Vessel tortuosity represents an important clinical manifestation in FD. A computer-assisted analysis of retinal and conjunctival vasculature demonstrated an increased vessels tortuosity in patients affected by Fabry disease. This non-invasive technique might be useful to help the diagnosis in early stages, to establish disease severity and monitor its progression.

Inter-visit measurement variability of conjunctival vasculature and circulation in habitual contact lens wearers and non-lens wearers

BackgroundThe inter-visit variation of measuring bulbar conjunctival microvasculature and microcirculation needs to be considered when the results from multiple visits are interpreted. This study examined the inter-visit variability of measuring conjunctival microvasculature and microcirculation in habitual contact lens (HCL) wearers and non-contact lens (NCL) wearers.MethodsTwenty-eight subjects were recruited including 13 HCL wearers (10 females and 3 males; mean age ± standard deviation, 25.8 ± 4.6 years) who had worn contact lenses on a daily basis for at least 3 years and 15 NCL wearers (10 females and 5 males, age 25.5 ± 4.0 years) were recruited. The temporal bulbar conjunctiva was imaged using a functional slit-lamp bio-microscope (FSLB) imaging system. FSLB imaging was performed in the morning when the HCL wearers did not wear their lenses. The measurements included conjunctival vessel diameter, vessel density, blood flow velocity and flow volume. In addition, conjunctival microvasculature was analyzed using monofractal (Dbox, representing vessel density) and multifractal (D0 representing vessel complexity) analyses. The repeated measurement was conducted at least one week after the first visit and both eyes of each participant were imaged. The coefficient of variation (CV) was calculated as the standard deviation of the differences between test and re-test then divided by the mean of the measurements. The intra-class correlation coefficient (ICC) was also calculated.ResultsNo significant differences of all vascular measurements in both the right and left eyes were found between two groups (P > 0.05). Between two measurements on two different visits, the CV was from 2.4% (vessel density D0) to 63.5% (blood flow volume Q) in HCL wearers and from 3.4% (D0) to 40.6% (blood flow volume) in NCL wearers. The ICC was from 0.60 (vessel diameter) to 0.81 (axial blood flow velocity VA) in HCL wearers and from 0.44 (Q) to 0.68 (cross-sectional blood flow velocity VS) in NCL wearers.ConclusionsThe measurement variability of the vessel density of the bulbar conjunctiva appeared to have the smallest inter-visit variation. The measurement variability of the vasculature and circulation in HCL wearers were similar to that in NCL wearers.

Ocular Biomarkers of Alzheimer's Disease: The Role of Anterior Eye and Potential Future Directions.

Globally, Alzheimer's disease (AD) is a growing health and economic challenge that has no effective cure. Recent clinical trials indicate that preclinical treatment may be required but a routine screening tool for AD has been elusive. Hence, a simple, yet sensitive biomarker for preclinical AD, when the disease is most likely to be amenable to treatment, is lacking. Due to several features, the eye has been explored for this purpose and, among the ocular tissues, the retina has received the most attention. Currently, major works investigating the potential AD diagnosis by detecting amyloid-β (Aβ) signatures in the retinal tissue are underway, while the anterior eye is more accessible for in vivo imaging and examination. This report provides a concise review of current literature on the anterior eye components, including the crystalline lens, cornea, and aqueous humor, in AD. We also discuss the potential for assessment of the corneal nerve structure and regeneration as well as conjunctival tissue for AD-related alterations. The crystalline lens has received considerable attention, but further research is required to confirm whether Aβ accumulates in the lens and whether it mirrors brain neuropathologic changes, particularly in preclinical AD. The rich corneal neural network and conjunctival vasculature also merit exploration in future studies to shed light on their potential association with AD pathologic changes.

Ocular Effects of Sulfur Mustard and Therapeutic Approaches.

Sulfur mustard (SM) is a strong blistering, highly reactive, lipophilic chemical war agent that causes injury in different organs including the skin, eyes, and respiratory tract. The Eyes are especially susceptible to the consequences of SM poisoning because of the aqueous and mucosal nature of conjunctiva and cornea. DNA alkylation and depletion of glutathione, are the most important mechanisms of SM action in the eye injuries. Acute clinical symptoms are including decrease in visual acuity, dryness, photophobia, blepharospasm, conjunctivitis, and complaints of foreign body sensation and soreness that gradually progress to severe ocular pain. Corneal abrasions, ulcerations, vesication, and perforations are common corneal consequences in SM injured victims. Appearance of chronic symptoms has been reported as chronic inflammation of the corneal and conjunctival vasculature, ischemia, lipid and cholesterol deposition, scarring in cornea, corneal thinning, opacification and perforation of the cornea, limbal stem cell deficiency (LSCD), and neovascularization. Different medical and surgical protocols have been documented in the management of SM-induced ocular injuries, including preservative-free artificial tears, topical steroids and antibiotic, mydriatic, antiglaucoma drops, therapeutic contact lenses, dark glasses and punctal plugs/cauterization, N-acetylcysteine, tarsorrhaphy, amniotic membrane transplantation, stem cell transplantation, and corneal transplantation. New drugs such as resolvin E1, topical form of essential fatty acids, thymosin β4, 43 amino-acid polypeptides, topical form of curcumin, newly formulated artificial tears, diquafosol, rebamipide, tretinoin, and oral uridineseems to be beneficial in the management of ocular lesion associated with sulfur mustard poisoning. Further studies are needed to approve these drugs in SM victims. J. Cell. Biochem. 118: 3549-3560, 2017. © 2017 Wiley Periodicals, Inc.

Automated Real-Time Conjunctival Microvasculature Image Stabilization.

The bulbar conjunctiva is a thin, vascularized membrane covering the sclera of the eye. Non-invasive imaging techniques have been utilized to assess the conjunctival vasculature as a means of studying microcirculatory hemodynamics. However, eye motion often confounds quantification of these hemodynamic properties. In the current study, we present a novel optical imaging system for automated stabilization of conjunctival microvasculature images by real-time eye motion tracking and realignment of the optical path. The ability of the system to stabilize conjunctival images acquired over time by reducing image displacements and maintaining the imaging area was demonstrated.

English

Hereditary hemorrhagic telangeiectasia (HHT) is an autosomal dominant genetic disorder that leads to vascular malformations. It was first recognized in the 19th century as a familial disorder with abnormal vascular structures causing bleeding from the nose and gastrointestinal tract. HHT is characterized by telangiectatic lesions of the nose, lips, lungs, brain, and spinal cord. The reported incidence in Europe and Japan is between 1:5000 and 1:8000; but is widely variable in other regions. It is seen more frequently in whites. Ocular involvement has been reported in patients with HHT. Although conjunctival telangiectasia is the most common manifestation, rarely intraocular vascular lesions such as retinal telangiectasia and arteriovenous malformations in the retina, are seen. We describe a patient with HHT who had an abnormal unilateral retinal vascular abnormality along with tortuous conjunctival vasculature in the other eye, which has not been reported till date.

Povidone iodine in the treatment of adenoviral conjunctivitis in infants

Context: Adenoviral conjunctivitis.Objective: To examine the effects of conjunctival irrigation with povidone iodine in infants with adenoviral conjunctivitis. Material and methods: An outbreak of adenovirus conjunctivitis occurred between September and December 2012 at the neonatal intensive care unit of our hospital. Forty-three infants with adenoviral conjunctivitis were examined in this study. Thirty-five eyes of 35 infants who had detailed ophthalmological examination and clinical scoring were included. The conjunctiva of 15 infants (Group 1) were irrigated with povidone iodine 2.5% solution and then treated with preservative-free artificial tears and preservative-free antibiotic drops. Twenty infants (Group 2) were treated only with the same drops with the same posology, without conjunctival irrigation with povidone iodine. Patients were examined two times a week until the complete recovery. Lid edema, conjunctival chemosis, fragility of conjunctival vasculature, pseudomembrane formation, and corneal involvement were scored clinically. Results: Twenty patients (57%) were female and 15 patients (43%) were male and mean age was 3.1 months (ranged from 1 to 4 months). No relation was found between gender and clinical scores. Statistically significant lower clinical scores were obtained from Group 1. The median recovery time was earlier in Group 1 (7 d) than Group 2 (12 d) (p = 0.001). Conclusion: Conjunctival irrigation with 2.5% povidone iodine is effective in the treatment of adenoviral conjunctivitis in infants.

Orthogonal polarization spectral imaging of conjunctival microcirculation

Orthogonal polarization spectral (OPS) imaging is an optical imaging technique that uses a handheld microscope and green polarized light to visualize the red blood cells in the microcirculation of organ surfaces. The purpose of this study was to evaluate whether OPS imaging can be used for the functional and morphological evaluation of microcirculation in the conjunctiva. To accomplish the aforementioned purpose, 21 eyes of 21 volunteer patients were examined. OPS images of the vasculature of the inferior conjunctiva and the nasal part of the bulbar conjunctiva were taken from each eye. The images were subsequently analyzed using a computer, and the following parameters were assessed: red blood cell velocity, blood vessel diameter, and functional capillary density. In addition, distinct qualitative aspects of the conjunctival microvasculature were characterized. OPS imaging facilitated both the observation of red blood cells that were flowing through conjunctival vessels on a white background, and the measurement of other quantitative and qualitative microvascular parameters. Significant differences between several measures of the inferior and nasal bulbar conjunctival microcirculations were found, including differences in the configurations of the vessel segments, the number of vessel segments, the number of bifurcations, the mean diffusion distance, and the functional capillary density. OPS imaging can be used to measure the diameters of microvessels, functional capillary density, and other parameters. Significant differences between the microcirculations of the inferior conjunctiva and the nasal bulbar conjunctiva were found, which indicates the necessity of using a standardized approach to examine the conjunctival vasculature. OPS imaging is suitable for both the functional and morphological evaluation of the conjunctival microcirculation.

The Effect of Rho-Associated Kinase Inhibition on the Ocular Penetration of Timolol Maleate

To assess the effects of Rho-associated kinase (ROCK) inhibition on the intraocular penetration of timolol maleate. Ex vivo porcine corneal penetration of timolol maleate, sotalol hydrochloride, or brinzolamide incubated with or without Y-27632 was determined in vertical Franz diffusion cells. The effect of ROCK inhibition on the vasodilation of porcine conjunctival vasculature was assessed by scanning electron microscopy (SEM) and immunohistochemical staining with subsequent laser-scanning confocal microscopy (LSCM). Experiments were conducted in New Zealand White (NZW) rabbits to assess the effect of ROCK inhibition on the intraocular distribution of timolol maleate. ROCK inhibition resulted in minimal alteration of ex vivo porcine corneal drug penetration of timolol, sotalol, or brinzolamide. SEM and LSCM experiments conducted with conjunctiva and sclera tissue in Franz diffusion cells suggested vasodilation in the conjunctival vasculature in the presence of Y-27632. Pretreatment of the eyes of NZW rabbits with Y-27632 resulted in aggregate fold reductions (1 hour, 0.25-fold; 4 hours, 0.45-fold) of timolol maleate drug concentrations in intraocular tissues (aqueous humor, lens, and iris) versus eyes not receiving Y-27632 pretreatment. Pretreatment with a vasoconstrictor, phenylephrine, resulted in a reversal of the effect of Y-27632 on diminished timolol maleate intraocular penetration in NZW rabbits. ROCK inhibition reduced the intraocular penetration of administered timolol maleate presumably due to increased systemic elimination through the conjunctival vasculature. It is anticipated that care in order and timing of ROCK inhibitor administration will be warranted for those patients who may be on a multiple topical drug regimen for primary open-angle glaucoma.

Increased Intraocular Pressure after Extensive Conjunctival Removal: A Case Report

A 50-year-old woman, who had undergone extensive removal of conjunctiva on the right eye for cosmetic purposes at a local clinic 8 months prior to presentation, was referred for uncontrolled intraocular pressure (IOP) elevation (up to 38 mmHg) despite maximal medical treatment. The superior and inferior conjunctival and episcleral vessels were severely engorged and the nasal and temporal bulbar conjunctival areas were covered with an avascular epithelium. Gonioscopic examination revealed an open angle with Schlemm's canal filled with blood to 360 degrees in the right eye. Brain and orbital magnetic resonance imaging and angiography results were normal. With the maximum tolerable anti-glaucoma medications, the IOP gradually decreased to 25 mmHg over 4 months of treatment. Extensive removal of conjunctiva and Tenon's capsule, leaving bare sclera, may lead to an elevation of the episcleral venous pressure because intrascleral and episcleral veins may no longer drain properly due to a lack of connection to Tenon's capsule and the conjunctival vasculature. This rare case suggests one possible mechanism of secondary glaucoma following ocular surgery.

Human conjunctival microvasculature assessed with a retinal function imager (RFI)

The conjunctival and cerebral vasculatures share similar embryological origins, with similar structural and physiological characteristics. Tracking the conjunctival microvasculature may provide useful information for predicting the onset, progression and prognosis of both systemic and central nervous system (CNS) vascular diseases. The bulbar conjunctival vasculature was imaged using a retinal function imager (RFI, Optical Imaging Ltd, Rehovot, Israel). Hemoglobin in red blood cells was used as an intrinsic motion-contrast agent in the generation of detailed noninvasive capillary-perfusion maps (nCPMs) and the calculation of the blood flow velocity. Five healthy subjects were imaged under normal conditions and again under the stress condition of wearing a contact lens. The retina was also imaged in one eye of one subject for comparison. The nCPMs showed the conjunctival microvasculature in exquisite detail, which appeared as clear as the retinal nCPMs. The blood flow velocities in the temporal conjunctival microvasculature were 0.86±0.08 (mean±SD, mm/s) for the bare eye and 0.99±0.11mm/s with contact lens wear. It is feasible to use RFI for imaging the conjunctival vasculature.

Visible Spectrum, Bi-Modal Ocular Biometrics

Most current ocular biometric systems are based on recognition and classification of unique iridial patterns typically captured in near infrared spectrum (NIR). However, eye images in the visible spectrum (e.g. RGB images) also reveal some iridial patterns in addition to the vascularity of the white of the eyes (mostly due to conjunctival and episcleral layers). These vascular patterns have rich and uniquely identifiable information. The combination of the aforementioned modalities provides an opportunity for bi-modal ocular biometrics using only visible spectrum captures. Multimodality improves the performance of biometric systems compared to single mode biometrics. In this work, a bi-modal ocular biometric system is described, where match scores from vasculature of the white of the eye and iris modalities are fused. We report the performance of this enhanced complementary biometric identification using UBIRIS v1 database. The proposed method, for a quality-vetted subset of UBIRIS v1 RGB ocular images, produces an area under receiver operating characteristic curve (AUC) of 0.9954 and an equal error rate (EER) of 0.0452. In comparison, individual modalities yield an AUC of 0.9822 and EER of 0.0759 for iris and an AUC of 0.9623 and an EER of 0.1022 for conjunctival vasculature. The proposed new algorithms may overcome constraints of using NIR imaging for iris and provide a better overall performance using only RGB eye images. We conclude that bi-modal iris–conjunctival fusion can improve the otherwise challenging RGB iris recognition.

Conjunctival vasculature patterns influencing the filtering bleb shape following trabeculectomy with limbal-based conjunctival flaps

To investigate the correlation between conjunctival vasculature factors and two types of functional bleb shape, cystic and diffuse, formed after trabeculectomy with limbal-based conjunctival flaps. Eighty-five eyes of glaucoma patients were consecutively enrolled. After 6 months, functioning blebs were classified as either cystic or diffuse. For each bleb type, the presence of neovascularized vessels in the dissected area (NVc) or the nondissected area (NVi), an avascular area (AVA), or a posterior tarsal artery (PTA) feeding the conjunctiva was analyzed. In 62 eyes with functioning blebs, there were 54 cystic and eight diffuse blebs. AVA was present in 96.3% of the cystic and 25.0% of the diffuse blebs. NVc was present in 100% of the cystic and 62.5% of the diffuse blebs, and NVi in 96.3% of the cystic and 12.5% of the diffuse blebs. A PTA was present in 87.5% of the diffuse blebs, but in only 3.7% of the cystic blebs. AVA, NVi, and NVc were significantly more frequent in cystic blebs, whereas a PTA was more frequent in diffuse blebs. The presence of a PTA in the blebs was negatively related to the presence of AVA, NVc, or NVi. Avoidance of damage to the PTA during conjunctival dissection might facilitate the formation of a diffuse filtration bleb. The conjunctival vasculature should be considered to avoid cystic avascular bleb formation in trabeculectomy with limbal-based flaps.