Cause Of Infectious Uveitis Research Articles

Trematode Granuloma: Journey of the Worm from the River Bed to the Agar Plate

Abstract Trematode granuloma has been reported as one of the common causes of infectious uveitis in paediatric age group in recent times in Tamil Nadu. These granulomas occur after exposure to the trematode-infested water resources. Studies from South India have established the cause of granuloma as trematode by histopathological and molecular diagnostics. The smaller granulomas responded to topical and oral steroids while larger lesions needed surgical excision. Untreated cases develop retro corneal membrane, cataract, glaucoma and even phthisis in the long run. Early identification and prompt treatment are needed to prevent visual morbidity in these children.

Etiologies and Demographic Distribution of Uveitis in a Referral Center in Iraq

Purpose: To determine the etiologies and demographic distribution of uveitis in a referral center in Baghdad, Iraq, and to compare the results with a similar study done in the same center in 2014. Study Design: Descriptive observational study. Place and Duration of Study: Ibn Al-Haitham Teaching Eye Hospital, Iraq, from January 2019 to June 2022. Patients and Methods: Two hundred and fourteen patients with uveitis were included. They underwent complete ocular and relevant systemic examination. Data was collected and analyzed using descriptive statistics. Comparison was done with the data retrieved from 2014. Results: Out of 264 patients, only 214 (81%) completed follow up. Others did not show up again due to Corona virus Pandemic. There were 122 (57%) females, 95 (44.3%) were unilateral, 62 (28.9%) were granulomatous, 62 (28.9%) were anterior, 42 (19.6%) were intermediate, 4 (1.8%) were posterior and 106 (49.7%) were panuveitis cases. Cause was identified in 161 (75.3%) patients while 53 (24.7%) were considered idiopathic. Out of 214 patients, 84 (39.2%) were due to infectious causes like tuberculosis, herpes (herpes zoster or simplex viruses), and toxoplasmosis. On the other hand, 130 (60.7%) cases were non-infectious for example, Vogt-Koyanagi-Harada disease, Behcet disease, connective tissue diseases such as Ankylosing Spondylitis, or idiopathic. Conclusion: A minor change was found from the 2014 study to 2023. Tuberculosis is now the most common cause of infectious uveitis instead of Toxoplasmosis. Furthermore, Idiopathic, Vogt-Koyanagi-Harada, and Behcet disease are the commonest causes of non-infectious uveitis.

Incidence of Uveitis in Local Population of Lahore

Uveitis tends to afflict younger age groups than other eye disorders like cataract and glaucoma, which typically affect the elderly. The frequency and prevalence of infectious ocular inflammation may vary greatly depending on the etiological agent and geographical location. This study found that the most frequent causes of infectious uveitis, which can account for up to 20% of all cases of uveitis in the developed world, are toxoplasmosis and herpetic infection. We found out that uveitis was more prevalent in the female population and that too in the younger age group having anterior uveitis more common.

The large Hellenic Study of Uveitis: epidemiology, etiologic factors and classification

PurposeTo analyse the demography, etiology, and classification of uveitis at a tertiary academic referral center.MethodsAn observational study was conducted on the archives of uveitic patients at the Ocular Inflammation Service of the Department of Ophthalmology at the University Hospital of Ioannina (Greece) from 1991 to 2020. This study aimed to investigate the epidemiological profile of patients, including their demographics and the main etiologic factors of uveitis.ResultsOut of 6191 cases with uveitis, 1925 were infectious, 4125 were non-infectious, and an overall of 141 masquerade syndromes were recorded. Among these cases, 5950 patients were adults, with a slight female predominance, while 241 were children (< 18 years old). Interestingly, 24.2% of cases (1500 patients) were associated with 4 specific microorganisms. Herpetic uveitis (HSV-1 and VZV/HZV) was the most common cause of infectious uveitis (14.87%), followed by toxoplasmosis (6.6%) and tuberculosis (2.74%). In 49.2% of non-infectious uveitis cases, no systematic correlation was found. The most frequent causes of non-infectious uveitis included sarcoidosis, white dot syndromes, ankylosing spondylitis, lens-induced uveitis, Adamantiades-Behçet disease, and idiopathic juvenile arthritis. Infectious uveitis was more common in the rural population, whereas non-infectious uveitis was more frequently recorded in the urban populationConclusionsAlthough our study was conducted on a predominantly white Caucasian population, it also reflects the effect of increasing immigration, improvements of diagnostic techniques, changes in referral patterns, and various actual changes in disease incidence.

Woman with black floaters in eye.

A 29-year-old female presented to the emergency department with decreased visual acuity and black floaters in the left eye after an insidious progression of a febrile illness with associated myalgias, headaches, and lymphadenopathy over a 4-week period. History revealed she had eaten undercooked venison several weeks before symptom onset. She was afebrile and neurologically intact, without evidence of vitreal or retinal abnormalities on bedside ultrasound. During ophthalmologic follow-up care 2 days later, she developed left nasal visual field deficit. Ophthalmology noted optic disk edema and steroid therapy was initiated for presumed optic neuritis. Subsequent magnetic resonance imaging was negative, and she was referred to a retinal specialist who identified focal active chorioretinitis and confirmed the diagnosis with serum antibody titers (Figure 1). Toxoplasmosis chorioretinitis is one of the most frequent causes of infectious uveitis affecting the posterior segment of the eye, which can cause severe vision loss. The most common cause is ingestion of undercooked meat or water with oocytes.1-3 Infections may be asymptomatic. However, ocular symptoms can occur as a result of initial infection or reactivation of previous infection.4 The classic retinal finding is the “headlight in fog sign” noted by a focal retinitis viewed through vitreous haze.5 Diagnosis is made clinically. Serum antibody titers confirm the diagnosis. A 4- to 6-week course of trimethoprim-sulfamethoxazole is the first-line therapy for sight-threatening lesions. Other scenarios or refractory cases may require regimens of azithromycin, pyrimethamine, atovaquone, leucovorin, glucocorticoids, and/or intravitreal clindamycin injections. Lifelong suppressive antitoxoplasmosis treatment is often necessary to prevent recurrence.6

Clinical Features of Infectious Uveitis in Children Referred to a Hospital-Based Eye Clinic in Italy.

Background and Objectives: To investigate the etiology, clinical features, ocular complications, and visual outcomes in children with infectious uveitis referred to a tertiary uveitis hospital-based service. Materials and Methods: Children with infectious uveitis were included in a retrospective cohort study. The data set was obtained after reviewing the medical records of pediatric patients with uveitis of different causes referred to our center during the period from 2009 to 2019. Clinical evaluations were performed at the time of diagnosis and the end of follow-up. Results: Uveitis of infectious origin was present in 57 (72 eyes) of 314 (18.1%) patients examined. The median age at presentation was 10.9 years (6.1-15.8), 52.6% of patients were female, and 47.4% were male. The main cause of infectious uveitis was viral (56.1% of cases), followed by Toxoplasma gondii infection (24.5%). The anatomical location of uveitis was posterior in 40.3%, anterior in 36.8%, panuveitis in 15.7%, and intermediate in 7% of cases. Ocular involvement was unilateral in 42 children (73.7%) and bilateral in 15 (26.3%) cases. The main causes of reduced visual acuity were cataract and maculopathy in 57.1% and 28.5% of cases, respectively. During the follow-up period, 75% of patients showed significant improvements in visual acuity. Conclusions: Specialist management in a tertiary referral eye care center facilitates early diagnosis and effective treatment of this serious cause of morbidity and vision loss in children.

Herpetic Uveitis: An Experience from a Tertiary Referral Center in Bulgaria

Introduction: The human Herpesviridae have been described as a leading cause of infectious uveitis. The most common manifestations are keratouveitis and iridocyclitis. The diagnosis is usually made on clinical grounds. The present therapy is based upon the inhibition of viral replication and the use of anti-inflammatory medications.&#x0D; Methods: A descriptive study was conducted on the records of 206 patients with uveitis from the Clinic of Ophthalmology at University Hospital Alexandrovska, Sofia, Bulgaria. The study period was from January 2012 until August 2019. The diagnosis was based on the clinical exam and, when necessary, on specialized testing – PCR on aqueous humor or vitreous material. We used descriptive statistical methods.&#x0D; Results: Out of 206 patients with intraocular inflammation, 46 (22.3%) were diagnosed with herpetic uveitis. Of them, 35 (76.1%) had anterior uveitis, 7 patients (15.2%) had panuveitis, and 4 patients (8.7%) had posterior uveitis. The mean age was 45.3 years. The leading complications were ocular hypertension, corneal leucoma, retinal detachment, and cataract. Antiviral therapy with acyclovir or valaciclovir, alone or with corticosteroids, was used in all groups.&#x0D; Conclusion: The herpesviruses are important causative agents of infectious uveitis. In our study, non-granulomatous, hypertensive anterior uveitis was the most common clinical entity. There were also a few patients with posterior and panuveitis. VZV was the most common etiologic agent. The panuveitis cohort had the worse prognosis for visual acuity, mostly as a result of retinal detachment. The posterior uveitis presented most frequently as focal retinochoroiditis with a good prognosis.

Infectious Uveitis in Horses and New Insights in Its Leptospiral Biofilm-Related Pathogenesis.

Uveitis is a sight-threatening eye disease in equids known worldwide that leads to considerable pain and suffering. By far the most common type of uveitis in Germany and neighboring countries is classical equine recurrent uveitis (ERU), which is caused by chronic intraocular leptospiral infection and is the main cause of infectious uveitis in horses. Other infectious causes are extremely rare and are usually clinically distinguishable from ERU. ERU can be treated very effectively by vitreous cavity lavage (vitrectomy). For proper indications of this demanding surgery, it is necessary to differentiate ERU from other types of uveitis in which vitrectomy is not helpful. This can be conducted on the basis of anamnesis in combination with ophthalmologic findings and by aqueous humor examination. During vitrectomy, vitreous material is obtained. These vitreous samples have historically been used for numerous etiologic studies. In this way, a chronic intraocular leptospiral infection has been shown to be the cause of typical ERU and, among other findings, ERU has also been recognized as a biofilm infection, providing new insights into the pathogenesis of ERU and explaining some thus far unexplainable phenomena of ERU. ERU may not only have transmissible aspects to some types of uveitis in humans but may also serve as a model for a spontaneously occurring biofilm infection. Vitreous material obtained during therapeutically indicated vitrectomy can be used for further studies on in vivo biofilm formation, biofilm composition and possible therapeutic approaches.

Rickettsial disease: An underestimated cause of posterior uveitis

Rickettsioses are worldwide distributed infectious disease caused by intracellular small Gram-negative bacteria transmitted to humans by the bite of contaminated arthropods, such as ticks. Systemic disease typically consists of a triad of high fever, headache, and skin rash. It usually has a self-limited course, but severe, life-threatening complications can sometimes occur. It may be clinically difficult to differentiate rickettsial diseases from other febrile illnesses. Rickettsial infection has been largely underestimated as a cause of infectious uveitis for long decades in the past. Conversely, recent data show that ocular involvement is much more common than previously thought, with retinitis, retinal vasculitis, and neuroretinitis being the most typical and frequent findings. Early clinical diagnosis of rickettsial disease, while awaiting laboratory test results, is essential for prompt initiation of appropriate antibiotic treatment to prevent systemic and ocular morbidity. The prevention remains the mainstay of rickettsial infection control.

Uveitis in Children

Uveitis in children is an important cause of ocular morbidity and severe vision loss. The diagnosis and the management are challenging in such population due to some unique presentations. Majority of the cases are idiopathic with infectious causes contributing to about one fifth of the cases. Various causes of infectious uveitis include tuberculosis, toxoplasmosis, toxocariasis. Anterior uveitis is the most common anatomical type of uveitis in children followed by almost equal incidence of posterior, intermediate and panuveitis. The examination is often difficult in children and diagnostic evaluation is challenging. The management requires multidisciplinary approach involving the rheumatologist and uveitis specialist. Exclusion of infectious and masquerade causes is of utmost importance before starting any immunomodulatory treatment. The primary aim of the treatment is to reduce the inflammation as early as possible to prevent complications. Corticosteroids are the main pillar stone for the management. The dosage and the route of the steroids should be optimized according to the growth and development of the child as it may have to be given for a longer duration. Steroid sparing agents such as methotrexate, cyclosporine, azathioprine and biologic agents are reserved for children refractory to treatment with steroids. Children tend to develop complications of uveitis more often than in adults, which include band keratopathy, cataract, glaucoma, cystoid macular edema, amblyopia and strabismus.

Evaluation of Infectious Uveitis at a Tertiary Referral Center in Turkey: A 31-year Retrospective Study.

Objectives:The aim of this study was to examine the demographic and clinical characteristics of patients with infectious uveitis over time.Methods:The records of a total of 2032 patients treated for uveitis were retrospectively analyzed and 369 eyes of 324 patients diagnosed with infectious uveitis were included in the study. The patients were divided into 2 groups according to the date of presentation. The first group comprised patients seen between January 1988 and August 2009, and patients who presented between September 2009 and April 2019 were classified in the second group.Results:The prevalence of infectious uveitis was 15.1% in the first group and 16.8% in the second group. A statistically significant decrease was observed in the number of toxoplasmosis patients in the second group (p=0.031). There was no significant difference in the number of patients with herpetic anterior uveitis (HAU) (p=0.215). A significant increase was recorded in the number of patients with tuberculosis and acute retinal necrosis (ARN) (p=0.006 and p=0.041, respectively). While there were no patients diagnosed with cytomegalovirus (CMV) anterior uveitis in the first group, 19 patients were diagnosed with the disorder in the second group. There was a decrease in the rate of legal blindness among the patients who were treated in the second period compared with the first period; however, this difference was not statistically significant (p=0.069).Conclusion:Toxoplasmosis and HAU were the 2 most common causes of infectious uveitis. The incidence of CMV anterior uveitis, tuberculosis-related uveitis, and ARN increased over the period studied.

Dexamethasone implant – An update

Uveitic entities may be infectious or noninfectious in etiology. Corticosteroids remain the first-line treatment for noninfectious posterior uveitis. Intravitreal injections of steroids have been useful in targeted therapy of the posterior segment. However, a host of systemic and local adverse effects limits the usefulness of steroids. Intravitreal implants of dexamethasone with sustained release of the drug over months are a more effective and safer option. Various formulations with varying dosage and lifespan such as retisert, ozurdex, and yutiq are available. Ozurdex has a very successful track record over numerous studies in treating posterior uveitis in adults and children. It is important to rule out infectious causes of uveitis before administering ozurdex. We can achieve optimal control of ocular inflammation with minimal systemic side effects when used judiciously.

Infectious Uveitis, Mechanisms, and Immunopathology

It is important to distinguish infectious uveitis from a noninfectious one for early treatment. Bacteria, viruses, fungi, parasites are the causes of infectious uveitis. Bacterial diseases causing uveitis are mainly syphilis, tuberculosis, Lyme disease, and brucellosis. HIV, HSV, VZV, CMV, EBV, measles, and rubella are frequent viral causes. The most common fungal uveitis causes are Candidiasis, Aspergillosis, Cryptococcosis, and Histoplasmosis. It is now widely accepted that uveitis is not caused by direct infectious agents and that microorganisms alter immüne response leading to autoimmune and inflammatory diseases. The mechanism observed in immunopathogenesis is the destruction of retinal visual cells due to an irreversible CD4 T cell response. The Th1 cells reach the target retinal tissue from the peripheral lymphoid system for specific retinal autoantigens and cause changes in photoreceptors, leading to an increase of Th1 cytokines by an inflammatory reaction in the uveitic eyes, whereas the cytokines of Th2 increase in the later stages. In addition to Th1 cells, Th17, regulator T cells, cytokines, autoantibodies, and neutrophils are also discussed in immunopathogenesis.

Toxoplasmosis in Germany.

With approximately 30% of the world population infected, Toxoplasma gondii is one of the most widespread pathogenic parasites in both humans and animals and a major problem for health economics in many countries. This review is based on the findings of individual studies, meta-analyses, and Cochrane Reviews retrieved by a selective literature survey of the Medline and Google Scholar databases. Current data indicate a high rate of Toxoplasma gondii infection in Germany, ranging from 20% to 77% depending on age (95% confidence interval for 18- to 29-year-olds [17.0; 23.1]; for 70- to 79-year-olds [72.7; 80.5]). Male sex, caring for a cat, and a body mass index of 30 or more are independent risk factors for seroconversion. Postnatally acquired (food-related) infec- tion is predominant, but maternal-to-fetal transmission still plays an important role. While most infections are asymptomatic, congenital toxoplasmosis and reactivated Toxoplasma encephalitis in immunosuppressed persons (transplant recipients and others) are sources of considerable morbidity. Toxoplasma gondii infection of the retina is the most common cause of infectious uveitis in Germany. The diagnosis and treatment of this type of parasitic infection are particular to the specific organs involved in the individual patient. Desirable steps for the near future include development of an effective treatment for the cystic stage and identifica- tion of biomarkers to assess the risk of reactivation and predict the disease course.

Real-Time Multiplex PCR Analysis in Infectious Uveitis

ABSTRACTIntroduction: Infectious uveitis is a serious inflammatory condition that often causes grave ocular morbidity including permanent vision loss and damage to the structures of the eye. The most common causes of infectious uveitis include herpesviruses and Toxoplasma gondii. Traditionally, these infections have been identified and differentiated based on characteristic clinical examination findings; however, there is often overlap between these presentations and the unique cause of a given patient’s infection is not always clear. Therefore, a reliable and fast method for definitively diagnosing infectious uveitis would be helpful and potentially sight-saving. Several groups have recently found experimental success with real-time multiplex polymerase chain reaction (PCR) techniques.Methods: A comprehensive review of the literature was undertaken to further understand the current state of real-time multiplex PCR and its clinical use. Search terms including “real time multiplex PCR”, “infectious uveitis”, and “uveitis diagnosis” were used. Appropriate English-language articles were included in this review.Results: Publications from four main groups (two from the United States, one from Japan, and one from India) citing success with real-time multiplex PCR were compared and contrasted. All four groups used the same technique to develop a highly sensitive and specific multiplex PCR analysis and found that their tests maintained high sensitivity and specificity during validation testing. These tests confirmed clinical suspicions in the majority of cases of infectious uveitis, but there were also cases of clinical misdiagnosis that were corrected based on molecular pathogen detection. These patients were then initiated on appropriate antimicrobial therapy with subsequent clinical improvement.Discussion: Real-time multiplex PCR is a highly sensitive and specific laboratory assay that allows for rapid and reliable molecular diagnosis of causative agents in infectious uveitis. This in turn facilitates swift initiation of effective therapy and prevents long-term ocular damage and vision loss.

Rapid Detection and Identification of Uveitis Pathogens by Qualitative Multiplex Real-Time PCR.

PurposeInfectious uveitis is a serious sight-threatening infection commonly caused by herpesviruses and Toxoplasma gondii. Etiologic diagnosis based on the clinical evaluation is often challenging. We developed and validated a multiplex real-time PCR assay coupled with high-resolution melting (HRM) for rapid detection and identification of herpes simplex viruses 1 and 2 (HSV-1 and HSV-2), varicella-zoster virus (VZV), cytomegalovirus (CMV), and T. gondii.MethodsThe assay was designed to target pathogen genome regions that yield products with distinct melting temperatures. Analytical specificity, sensitivity, and precision of HRM identification were determined. Clinical validation was performed by testing 108 intraocular fluids collected from eyes suffering with infectious uveitis (n = 30) and controls (n = 78).ResultsA nonoverlapping high-precision profile for each pathogen was generated following HRM (coefficient of variation 0%). The assay was highly sensitive, with a limit of detection of 20 genome copies for herpesviruses and 200 genome copies for T. gondii. The intra- and interassay variability of cycle threshold (Ct) measurement was ≤4% and ≤6%, respectively. Thirteen intraocular specimens collected from suspected cases of infectious uveitis were positive (mean Ct values varied from 19.4 to 27.7). Melting profiles of positive cases were consistent with HSV-2 (n = 5), VZV (n = 5), CMV (n = 2), and T. gondii (n = 1). Amplicon identities were confirmed by sequencing. Control intraocular samples from patients without a clinical diagnosis of infectious uveitis were all negative.ConclusionsThis assay allows rapid, sensitive, and reliable detection and identification of the most common known causes of infectious uveitis, making early pathogen information-based intervention possible.

Patterns of Uveitis at Two University-Based Referral Centres in Cape Town, South Africa

ABSTRACTPurpose: To analyze the pattern of uveitis at two tertiary hospitals in South Africa which has a high prevalence of HIV, TB and syphilis.Methods: Data of 198 patients were obtained retrospectively between August 2014 and August 2016, including patient demographics, clinical examination, special investigations and final diagnosis.Results: Infectious uveitis was the most common aetiological category (47%), followed by idiopathic (34.8%) and non-infectious (18.2%). Syphilis was the most common identifiable cause (16.2%). Other important causes were toxoplasmosis, herpes viruses, tuberculosis and HLA-B27. HIV positive patients, who constituted 40% of the study population, were more likely to present with a posterior or panuveitis (relative risk 1.50, 95% CI 1.19–1.89) and more likely to have an infectious cause compared to HIV negative patients (relative risk 2.47, 95% CI 1.82–3.35).Conclusions: This study emphasizes the importance of HIV testing and investigations for infectious causes of uveitis, especially syphilis, in this population.

Cytokines and Chemokines Involved in Acute Retinal Necrosis

To investigate which cytokines and chemokines are involved in the immunopathogenesis of acute retinal necrosis (ARN), and whether cytokine profiles are associated with clinical manifestations, such as visual outcome. Serum and aqueous humor (AH) samples of 19 patients with ARN were analyzed by multiplex immunoassay. Infectious controls consisted of 18 patients with rubella virus-associated Fuchs' uveitis and 20 patients with ocular toxoplasmosis all confirmed by intraocular fluid analyses. The control group consisted of seven paired AH and serum samples from seven noninflammatory control patients with age-related cataract. In each sample, 4 anti-inflammatory, 12 proinflammatory, 2 vascular, and 4 other immune mediators were measured. In addition, various clinical characteristics were assessed. In ARN, 10 of the 22 mediators, including most proinflammatory and vascular mediators such as IL-6, IL-8, IL-18, MIF, MCP-1, Eotaxin, IP-10, IL-15, sICAM-1, and sVCAM-1, were significantly elevated when compared to all controls. In addition, one anti-inflammatory mediator (IL-10) was significantly elevated in ARN as compared to the controls. No association was found between the time of sampling and the extent and levels of immune mediator expression. The pathogenesis of ARN is characterized by the presence of predominantly proinflammatory cytokines and chemokines with high expression levels as compared to other infectious causes of uveitis. There are no indications for an obvious Th-1 or Th-17 pathway. The combined data suggest that immune mediator expression is related to severity of disease, which is more fulminant in ARN, rather than to a specific uveitis entity.

Galectins expressed differently in genetically susceptible C57BL/6 and resistant BALB/c mice during acute ocular Toxoplasma gondii infection.

Ocular toxoplasmosis (OT) caused by Toxoplasma gondii is a major cause of infectious uveitis, however little is known about its immunopathological mechanism. Susceptible C57BL/6 (B6) and resistant BALB/c mice were intravitreally infected with 500 tachyzoites of the RH strain of T. gondii. B6 mice showed more severe ocular pathology and higher parasite loads in the eyes. The levels of galectin (Gal)-9 and its receptors (Tim-3 and CD137), interferon (IFN)-γ, IL-6 and IL-10 were significantly higher in the eyes of B6 mice than those of BALB/c mice; however, the levels of IFN-α and -β were significantly decreased in the eyes and CLNs of B6 mice but significantly increased in BALB/c mice after infection. After blockage of galectin-receptor interactions by α-lactose, neither ocular immunopathology nor parasite loads were different from those of infected BALB/c mice without α-lactose treatment. Although the expressions of Gal-9/receptor were significantly increased in B6 mice and Gal-1 and -3 were upregulated in both strains of mice upon ocular T. gondii infection, blockage of galectins did not change the ocular pathogenesis of genetic resistant BALB/c mice. However, IFN-α and -β were differently expressed in B6 and BALB/c mice, suggesting that type I IFNs may play a protective role in experimental OT.

An Update on Tubercular Uveitis

Tuberculosis (TB) is an important cause of infectious uveitis causing significant morbidity and mortality especially in endemic countries. Mycobacterium tuberculosis (MTb) may infect any tissue or organ in the body, lungs being the most commonly affected. Ocular TB occurs due to hematogenous dissemination of MTb or due to a hypersensitivity reaction to the bacteria. It may lead to a very severe inflammation and destruction of ocular tissues leading to an irreversible loss of vision. Infection of the eye by MTb most commonly involves the uveal tissue causing anterior, intermediate, and posterior or panuveitis. Awareness of the varied clinical manifestations is important to suspect the ocular TB which may often be difficult to confirm by diagnostic tests available. A timely diagnosis and management may help in preventing severe loss of vision and the eye.