Corneal graft rejection is accompanied by apoptosis of the endothelium and is prevented by gene therapy with bcl-xL

Corneal transplants normally enjoy a high percentage of survival, mainly because the eye is an immune-privileged site. When allograft failure occurs, it is most commonly due to rejection, an immune-mediated reaction that targets the corneal endothelium. While the exact mechanism by which the endothelium is targeted is still unknown, we postulate that corneal endothelial cell loss during allograft failure is mediated by apoptosis. Furthermore, because corneal endothelial cells do not normally regenerate, we hypothesize that suppressing apoptosis in the graft endothelium will promote transplant survival. In a murine model of transplantation, TUNEL staining and confocal microscopy showed apoptosis of the graft endothelium occurring in rejecting corneas as early as 2 weeks posttransplantation. We found that bcl-xL protected cultured corneal endothelial cells from apoptosis and that lentiviral delivery of bcl-xL to the corneal endothelium of donor corneas significantly improved the survival of allografts. These studies suggest a novel approach to improve corneal allograft survival by preventing apoptosis of the endothelium.

Proteomic analysis of human meibomian gland secretions

BACKGROUND/AIM

Human tears contain hundreds of proteins that may exert a significant influence on tear film stability, ocular surface integrity, and visual function. The authors hypothesise that many of these proteins originate from the meibomian gland. This study's aim was to begin to develop the proteomic methodology to permit the testing of their hypothesis.

METHODS

Meibomian gland secretions were collected from the lower eyelids of adult volunteers and placed in a chloroform-methanol mixture. Samples were partitioned in a biphasic system and non-lipid phase materials were reduced, alkylated, and trypsin digested to obtain peptides for protein identification. This peptide mixture was separated by micro-capillary reverse phase chromatography and the effluent examined by nano-electrospray MS and data dependent MS/MS. SEQUEST software was used to identify proteins from the MS/MS spectra.

RESULTS

The methodological approach to date has permitted the identification of more than 90 proteins in human meibomian gland secretions. Proteins include the alpha2-macroglobulin receptor, IgA alpha chain, farnesoid X activated receptor, interferon regulatory factor 3, lacritin precursor, lactotransferrin, lipocalin 1, lysozyme C precursor, potential phospholipid transporting ATPase IK, seven transmembrane helix receptor (also termed somatostatin receptor type 4), testes development related NYD-SP21 (also termed high affinity IgE receptor beta subunit), and TrkC tyrosine kinase.

CONCLUSIONS

These findings indicate that the meibomian gland secretes a number of proteins into the tear film. It is quite possible that these proteins contribute to the dynamics of the tear film in both health and disease.

Molecular mechanisms of immunity in corneal allotransplantation and xenotransplantation

Corneal allotransplantation is the most common and successful form of solid organ transplantation in humans. In uncomplicated cases, the two-year graft survival rate is over 90%. This extraordinary success can be attributed in part to various features of the normal cornea and anterior segment that together account for their ‘immune-privileged’ status. However, despite this success, a significant number of corneal grafts fail and immunological rejection remains by far the leading cause of graft failure. Studies on animal models of corneal transplantation have yielded a wealth of information on the molecular and cellular features of graft rejection, and have established that this process is mediated primarily by CD4+ T cells of the T helper 1 (Th1) phenotype. In addition, studies have elucidated that certain facets of allosensitisation differ between corneal and other solid organ transplants. On the basis of these findings, novel experimental strategies selectively targeting the afferent or efferent arms of corneal alloimmunity have provided promising results in preventing corneal allograft rejection in the laboratory. Finally, because of the global shortage of human donor corneas, there is currently renewed interest in the possibility of using corneas from other species for transplantation into human eyes (xenotransplantation). Preliminary studies on animal models of corneal xenotransplantation have documented both antibody-mediated and cell-mediated responses that might play important roles in the accelerated rejection observed in corneal xenotransplants. This review synthesises the principal concepts emerging from studies of the molecular mechanisms in corneal transplant immunology.

[Angiogenesis and lymphangiogenesis in the cornea. Pathogenesis, clinical implications and treatment options]

BACKGROUND

Whereas the normal cornea is devoid of blood and lymphatic vessels,both can invade the cornea secondary to a variety of corneal diseases and after surgery. This not only reduces visual acuity, but also renders such a cornea high-risk, if subsequent corneal transplantation is performed.

METHODS

A PUBMED-based literature search was carried out.

RESULTS

Current knowledge on pathogenesis, clinical implications and treatment modalities for corneal neovascularization is discussed.

CONCLUSIONS

Novel anti-angiogenic and antilymphangiogenic therapeutic strategies should reduce blindness associated with corneal neovascularization and subsequent graft rejection.

Nutrient intake in women with primary and secondary Sjögren's syndrome

OBJECTIVE

Recently, it has been proposed that dietary factors may contribute to the etiology and progression of Sjögren's syndrome, and that nutritional intervention may modify the severity of pathological abnormalities. The objective of this study was to determine whether the nutrient intake of women with primary (1 degrees SS) or secondary (2 degrees SS; ie with systemic lupus erythematosus (2 degrees SS/SLE) or rheumatoid arthritis (2 degrees SS/RA) Sjögren's syndrome is significantly different than that of age- and gender-matched controls.

DESIGN

Women with Sjögren's syndrome were asked to complete the 97 General Purpose Semi-Quantitative Food Frequency Questionnaire, which consists of a list of 147 separate food items that represent the major sources of multiple nutrients. Nutritional data were evaluated in terms of absolute and energy-adjusted nutrient amounts and analyzed by ANOVA.

RESULTS

Our results showed: (a) greater intake of energy, glutamate, carbohydrates, lactose, phosphorus, caffeine and unsupplemental thiamin and riboflavin in 1 degrees SS, as well as supplemental calcium in 2 degrees SS/SLE, compared with controls; (b) greater nutrient intake of energy, protein, glutamate, methionine, tryptophan, carbohydrates, lactose, supplemental calcium and phosphorus, sodium, caffeine and unsupplemental calcium, riboflavin and thiamin in 2 degrees SS/RA, relative to 1 degrees SS and/or 2 degrees SS/SLE; (c) higher energy-adjusted values for supplemental calcium in 2 degrees SS/SLE, and for vitamin A and supplemental iron and zinc in 2 degrees SS/RA, compared with other groups; and (d) higher energy-adjusted intake of supplemental calcium, and a lower energy-adjusted intake of unsupplemental vitamin C, polyunsaturated fat, linoleic acid, omega-3 fatty acid, and specific other unsaturated fatty acids, in the Sjögren's syndrome group as a whole, relative to controls.

CONCLUSIONS

Our findings demonstrate that nutrient intake is altered in Sjögren's syndrome.

Hormone replacement therapy and dry eye syndrome

CONTEXT

Postmenopausal hormone replacement therapy (HRT) use is common in the United States. Some research suggests that estrogen may have detrimental effects on the tear film and could influence the development of dry eye syndrome, but few data are available on this relationship.

OBJECTIVE

To determine the relationship of HRT and dry eye syndrome.

DESIGN, SETTING, AND PARTICIPANTS

The Women's Health Study, a large cohort study in which 25 665 postmenopausal women provided information about use of HRT at baseline (1992), 12, and 36 months and dry eye syndrome at 48 months.

MAIN OUTCOME MEASURES

(1) Clinically diagnosed dry eye syndrome, as reported by participants; (2) severe symptoms (both ocular dryness and irritation either constantly or often); and (3) either clinically diagnosed dry eye syndrome or severe symptoms, compared between women who used HRT vs those who did not.

RESULTS

For the combined end point of either clinically diagnosed dry eye syndrome or severe symptoms, the multivariable-adjusted odds ratios were 1.69 (95% confidence interval [CI], 1.49-1.91) for estrogen use alone and 1.29 (95% CI, 1.13-1.48) for estrogen plus progesterone/progestin use compared with no HRT use. Each 3-year increase in the duration of HRT use was associated with a significant 15% (95% CI, 11%-19%) elevation in risk of clinically diagnosed dry eye syndrome or severe symptoms. Results were similar for the combined end point of clinically diagnosed dry eye syndrome and severe symptoms.

CONCLUSIONS

These data suggest that women who use HRT, particularly estrogen alone, are at increased risk of dry eye syndrome. Physicians caring for women who are taking or considering HRT should be apprised of this potential complication.

Immune response to intragraft antigen in draining lymph nodes after corneal transplantation is mediated by interleukin-12

To examine the molecular basis of immunity generated to intragraft antigens and determine whether it differs between acceptor and rejector hosts, we used a novel in vitro system to assay the T cell response to a specific antigen, ovalbumin (OVA), in the graft. OVA-containing corneas were orthotopically grafted into syngeneic or allogeneic hosts. Draining cervical lymph nodes (cLN) were assayed for OVA-specific T cell proliferation and cytokine production. In addition, cytokine production was assayed in cultures of antigen-presented cells (APC) isolated from cLN cultured with OVA-specific DO11.10 T cells and OVA. OVA-specific immunity was detected only in the draining cLN of mice following allogeneic, but not syngeneic, grafting, and this immunity was evident well before any demonstrable alloresponse in the graft. In addition, cLN cells from mice that accepted their corneal allografts produced significantly less interferon-gamma (IFN-gamma) when stimulated in culture than cells harvested from cLN of rejector hosts. Moreover, APC isolated from cLN of acceptor hosts produced significantly lower levels of IL-12. These data suggest that the induction of immunity to corneal antigens in the draining cLN occurs via an interleukin-12 (IL-12) and IFN-gamma-dependent mechanism. Targeting this process may serve as an effective immunomodulatory strategy in corneal transplantation.

Phacoemulsification in patients after allogeneic bone marrow transplantation

OBJECTIVE

To study the outcomes of phacoemulsification in allogeneic bone marrow transplant (allo-BMT) recipients.

DESIGN

Retrospective, noncomparative, interventional case series.

METHODS

Retrospective study of 34 eyes of 19 consecutive patients who had visually significant cataracts after allo-BMT and subsequently underwent phacoemulsification.

MAIN OUTCOME MEASURES

Best-corrected vision at the last follow-up visit and development of postoperative complications.

RESULTS

Surgery was done at a mean interval of 37 months after BMT, and the mean postoperative follow-up was 13 months. Twenty-one eyes (62%) had subnormal Schirmer I scores as a result of graft-versus-host disease (GVHD) involving the lacrimal gland. Of these, 71% (15 eyes) additionally had significant ocular surface epitheliopathy because of conjunctival GVHD. Frequent lubrication (95%), punctal occlusion (76%), topical steroids (33%), and other topical immunosuppressive therapies (14%) were used to manage GVHD-induced ocular surface disease before cataract surgery. Twelve patients (63%) also received systemic steroids and immunosuppressives. Patients proceeded to surgery only after their ocular surface disease was well controlled. Early postoperative complications included intraocular pressure elevation (three eyes), worsening of dry eye syndrome (two eyes), and corneal thinning (one eye). Posterior capsular opacification (PCO) requiring laser capsulotomy occurred in 44% of eyes. In eyes with preoperative conjunctival GVHD, 47% had recurrence with cessation of immunosuppressive therapy after surgery. Visual acuity at last follow-up visit was 20/30 or better in 33 (97%) eyes.

CONCLUSIONS

Phacoemulsification is an effective procedure in restoring vision in patients who have cataracts develop after BMT. However, coexisting ocular disease must be recognized and aggressively treated both before and after surgery to ensure good visual outcomes.

Role of CD4+ and CD8+ T cells in allorecognition: lessons from corneal transplantation

Corneal transplantation represents an interesting model to investigate the contribution of direct vs indirect Ag recognition pathways to the alloresponse. Corneal allografts are naturally devoid of MHC class II+ APCs. In addition, minor Ag-mismatched corneal grafts are more readily rejected than their MHC-mismatched counterparts. Accordingly, it has been hypothesized that these transplants do not trigger direct T cell alloresponse, but that donor Ags are presented by host APCs, i.e., in an indirect fashion. Here, we have determined the Ag specificity, frequency, and phenotype of T cells activated through direct and indirect pathways in BALB/c mice transplanted orthotopically with fully allogeneic C57BL/6 corneas. In this combination, only 60% of the corneas are rejected, while the remainder enjoy indefinite graft survival. In rejecting mice the T cell response was mediated by two T cell subsets: 1) CD4+ T cells that recognize alloantigens exclusively through indirect pathway and secrete IL-2, and 2) IFN-gamma-producing CD8+ T cells recognizing donor MHC in a direct fashion. Surprisingly, CD8+ T cells activated directly were not required for graft rejection. In nonrejecting mice, no T cell responses were detected. Strikingly, peripheral sensitization to allogeneic MHC molecules in these mice induced acute rejection of corneal grafts. We conclude that only CD4+ T cells activated via indirect allorecognition have the ability to reject allogeneic corneal grafts. Although alloreactive CD8+ T cells are activated via the direct pathway, they are not fully competent and cannot contribute to the rejection unless they receive an additional signal provided by professional APCs in the periphery.

The critical role of lymph nodes in corneal alloimmunization and graft rejection

PURPOSE

To elucidate the role of draining cervical lymph nodes (CLNs) in corneal alloimmunity.

METHODS

Fully mismatched orthotopic corneal transplantation was performed in BALB/c hosts that had their CLNs excised before transplantation (CLN(-)). Normal hosts (CLN(+)), splenectomized mice (Sp(-)), and those without either CLNs or spleen (CLN(-)/Sp(-)) served as comparison groups. To determine the contribution of CLNs to alloimmunity more directly, CLN(-) mice were reconstituted by grafting LNs from other BALB/c mice to their cervical lymphatic chains, thus deriving CLN(-/+) mice. Tetramethyl rhodamine isothiocyanate's (TRITC) flow to draining CLNs was used as a measure of afferent lymph flow. Graft survival and allospecific delayed-type hypersensitivity (DTH) were used as measures of alloreactivity.

RESULTS

Fifty percent of normal control and 12% of Sp(-) hosts accepted the allografts. In contrast, 100% of CLN(-) and 88% of CLN(-)/Sp(-) hosts accepted allografts indefinitely (P < 0.01). Additionally, all CLN(-) hosts failed to demonstrate allospecific DTH (P < 0.001). CLN(-/+) mice reconstituted with LN from naïve animals showed graft survival rates and DTH responses that were indistinguishable from those of naïve CLN(+) mice. Of particular interest, however, is that mice reconstituted with CLNs from hosts with rejected corneal grafts had swift rejection of subsequent corneal grafts and exhibited strong donor-specific DTH. In contrast, mice reconstituted with CLNs from hosts with accepted corneal grafts showed rejection of subsequent corneal grafts in a manner that was indistinguishable from rejection in naïve CLN(+) hosts.

CONCLUSIONS

Draining CLNs play a critical role in allosensitization and rejection. In contrast to the spleen, draining CLNs do not appear to play a critical role in tolerance induction in corneal transplantation.

Blockade of CD40-CD154 costimulatory pathway promotes survival of allogeneic corneal transplants

PURPOSE

To determine the effect of systemic anti-CD154 monoclonal antibody on the survival of orthotopic murine corneal transplants.

METHODS

BALB/c mice were used as recipients of syngeneic, multiple minor histocompatability (H)-disparate, or major histocompatibility complex MHC-mismatched corneal transplants. Recipient beds were either avascular (normal risk) or neovascularized (high risk). Mice were randomized to receive either anti-CD154 antibody or control immunoglobulin by intraperitoneal injection at surgery and once weekly after surgery. After orthotopic corneal transplantation, all grafts were evaluated for signs of rejection by slit lamp biomicroscopy over 8 weeks. The high-risk transplants were continuously observed until week 18 after the therapy was discontinued at week 8. Allospecific delayed-type hypersensitivity (DTH) was evaluated after transplantation in high-risk graft recipients. Frequency of interferon (IFN)-gamma-secreting T cells in the hosts was measured by enzyme-linked immunospot (ELISPOT) assay.

RESULTS

In normal-risk transplantation, the 8-week survival rate improved from 25% in control mice to 88% in anti-CD154-treated hosts of minor H-disparate grafts (P = 0.0087) and from 78% in control mice to 100% in anti-CD154-treated recipients of MHC-mismatched transplants (P = 0.177). Of particular significance, in high-risk transplantation, anti-CD154 therapy dramatically enhanced the survival of both minor H- and MHC-disparate corneal transplants to 100% (P = 0.0001) and 92% (P = 0.0002), respectively. In addition, the anti-CD154-treated mice did not exhibit allospecific immunity. However, termination of anti-CD154 led to some loss in graft survival, especially among high-risk minor H-disparate grafts. The frequency of IFN-gamma-producing T cells was significantly reduced in anti-CD154-treated hosts.

CONCLUSIONS

Continuous suppression of the CD40-CD154 costimulatory pathway promotes the acceptance of corneal transplants, regardless of the degree of allodisparity or preoperative risk. The beneficial effect of anti-CD154 treatment may be due in part to inhibition of Th1-mediated responses.

Efficacy and tolerability outcomes after punctal occlusion with silicone plugs in dry eye syndrome

PURPOSE

Silicone punctal plugs are widely used to conserve moisture in tear-deficient eyes. We studied the efficacy and tolerability of punctal plugs in symptom reduction and improvement of ocular surface disease parameters in dry eye syndrome.

METHODS

We reviewed the records of 50 consecutive patients with dry eye syndrome who were symptomatic despite maximally tolerable lubricant therapy and had bilateral lower punctal plug insertion. After plug insertion, all patients (41 women and nine men) had 6 months or more of follow-up. The subjects ranged in age from 22 to 57 years (mean, 30 years). We recorded subjective and objective improvement of ocular surface disease, frequency of lubricant use, need for upper punctal occlusion, and occurrence of complications after plug insertion. We determined plug retention rates using Kaplan-Meier analyses and assessed associated factors using Cox proportional hazards models.

RESULTS

Six months after initial plug placement, 43 of 50 patients (86%) were symptom free, 28 of them (56%) with plugs alone, and 38 patients (76%) had stopped using lubricants on a daily basis. Spontaneous loss of plugs was common, especially in the initial 3 months of follow-up. Considering all plugs, the estimated probability of plug retention was 63% after 6 months of follow-up. Puncta refitted after initial plug loss were twice as likely to lose the replacement plug (P =.02). Upper punctal plugs showed a 4.3-fold higher risk of loss compared with plugs inserted in lower puncta (P <.0001).

CONCLUSIONS

There is both a reduced dependency on artificial lubricants and relief of symptoms of dry eye after punctal plugs. However, spontaneous plug loss occurs in a substantial minority of patients. Patient education and close follow-up, particularly in the first 3 months, is recommended to detect plug loss and ensure adequate control of the disease.

Effect of androgen deficiency on the human meibomian gland and ocular surface

The purpose of this study was to determine whether the chronic use of antiandrogen medications leads to meibomian gland dysfunction, altered lipid profiles in meibomian gland secretions, decreased tear film stability, and evaporative dry eye. Subjects taking antiandrogen therapy for prostatic indications, as well as age-related controls, were asked to complete a questionnaire that assessed dry eye symptoms and then were given a complete anterior segment examination. Moreover, meibomian gland secretions were obtained from each eye and analyzed by high-performance liquid chromatography/mass spectrometry for the relative content of cholesterol, cholesterol esters, wax esters, diglycerides, triglycerides, and specific molecular species in the diglyceride fraction. Our results demonstrate that patients taking antiandrogen treatment, compared with age-related controls, had a: 1) significant increase in the frequency of appearance of tear film debris, an abnormal tear film meniscus, irregular posterior lid margins, conjunctival tarsal injection, and orifice metaplasia of the meibomian glands; 2) significant increase in the degree of ocular surface vital dye staining; 3) significant decrease in the tear film breakup time and quality of meibomian gland secretions; and 4) significant increase in the frequency of light sensitivity, painful eyes, and blurred vision. In addition, the use of antiandrogen pharmaceuticals was associated with significant changes in the relative amounts of lipids in meibomian gland secretions. Our findings indicate that chronic androgen deficiency is associated with meibomian gland dysfunction and dry eye.

Interleukin-1 receptor antagonist therapy and induction of anterior chamber-associated immune deviation-type tolerance after corneal transplantation

PURPOSE

Topical treatment with interleukin 1 receptor antagonist (IL-1ra) can promote corneal allograft survival by suppressing induction of allodestructive immunity. The purpose of these experiments was to determine whether IL-1ra could also promote induction of allo-protective tolerogenic pathways, including anterior chamber-associated immune deviation (ACAID), which has been shown to participate in long-term survival of corneal transplants.

METHODS

Corneal buttons from BALB/c (syngeneic) or C57BL/6 (fully mismatched allogeneic) mice were orthotopically grafted onto BALB/c recipients. Topical IL-1ra or vehicle alone was applied to grafts three times daily. Donor-specific ACAID was measured in allogeneic grafted mice at 4 and 8 weeks after transplantation by ear-challenging grafted hosts with donor-derived splenocytes 1 week after SC immunization. In separate experiments, grafted mice were treated for 4 weeks before injecting ovalbumin (OVA) into their anterior chambers to determine their capacity to induce antigen-specific ACAID.

RESULTS

Treatment with IL-1ra did not promote, or inhibit, induction of donor-specific ACAID compared with vehicle-treated controls at either the early or late time points studied. However, IL-1ra treatment after transplantation led to significantly earlier restoration of the grafted eyes' capacity for inducing ACAID to soluble antigen (OVA).

CONCLUSIONS

Promotion of OVA-specific ACAID by IL-1ra suggests that suppression of IL-1-mediated mechanisms contributes to recovery of the anterior segment's immunosuppressive microenvironment at least 1 month earlier than would otherwise be seen after corneal transplantation. However, IL-1ra treatment does not alter induction of donor-specific ACAID after transplantation, suggesting that its anti-inflammatory activities do not lead to an ACAID-inducing signal per se. This suggests that IL-1ra promotes graft survival almost exclusively by virtue of suppressing inflammation and not by directly promoting tolerance or antigen-specific regulatory pathways.

Topical soluble tumor necrosis factor receptor type I suppresses ocular chemokine gene expression and rejection of allogeneic corneal transplants

OBJECTIVE

To determine the effect of topical soluble tumor necrosis factor receptor type I (sTNFR-I) on survival of murine orthotopic corneal transplants and on ocular chemokine gene expression after corneal transplantation.

METHODS

BALB/c mice (N = 50) were used as recipients of multiple minor H-disparate corneal transplants from B10.D2 donors. After orthotopic corneal transplantation, mice were randomized in a masked fashion to receive either topical sTNFR-I or vehicle 3 times daily, and all grafts were evaluated for signs of rejection and neovascularization by slitlamp biomicroscopy for 8 weeks. Ocular chemokine gene expression in sTNFR-I- and vehicle only-treated groups was determined using a multiprobe ribonuclease protection assay.

RESULTS

Hosts treated with topical sTNFR-I experienced significantly enhanced corneal allograft survival compared with animals treated with vehicle alone (P =.01). Moreover, postoperative messenger RNA levels of RANTES and macrophage inflammatory protein-1beta in sTNFR-I-treated eyes were substantially suppressed compared with vehicle-treated eyes. Vehicle-treated eyes bearing rejected allografts expressed higher levels of messenger RNA for both chemokines than control eyes bearing accepted allografts.

CONCLUSIONS

Topical treatment with sTNFR-I promotes the acceptance of allogeneic corneal transplants and inhibits gene expression of 2 chemokines (RANTES and macrophage inflammatory protein-1beta) associated with corneal graft rejection.

CLINICAL RELEVANCE

Our findings support the feasibility of a topical anticytokine strategy as a means of reducing corneal allograft rejection without resorting to the use of potentially toxic immunosuppressive drugs.

Twenty-five-year panorama of corneal immunology: emerging concepts in the immunopathogenesis of microbial keratitis, peripheral ulcerative keratitis, and corneal transplant rejection

PURPOSE

To describe the most recent advances in our understanding of the cellular and molecular mechanisms involved in the immunopathogenesis of corneal immunoinflammatory disorders including microbial keratitis, peripheral ulcerative keratitis. and allograft rejection.

METHODS

Review of the published peer-reviewed literature that has contributed significantly to our modern understanding of corneal immunology. In addition, the authors have summarized the information in conceptual diagrams that highlight the critical cellular and molecular pathways that lead to corneal immune responses in the two most thoroughly studied corneal immune disorders, herpes simplex keratitis (HSK) and transplant rejection.

RESULTS

In spite of the wide array of molecular and cellular factors that mediate corneal immunity, critical mechanistic facets are shared by the various corneal immunoinflammatory disorders. These include activation and migration of local antigen-presenting cells (APCs), including Langerhans cells (LCs), upregulation in pleiotropic proinflammatory cytokines such as interleukin-1 (IL-1) and tumor necrosis factor-alfa (TNF-alpha) that can mediate a wide array of immune functions in addition to up-regulating protease expression. and chemokines that play a critical role on the one hand in attracting nonantigen-specific inflammatory cells such as neutrophils and on the other in attracting CD4+ T helper type 1 (Th1) cells that mediate most of the destruction in the cornea.

CONCLUSIONS

In the last 25 years, we have seen our field develop from a descriptive stage into a new phase where the fundamental processes that mediate and effect corneal immunity are being accurately deciphered. It is anticipated that this new knowledge will allow development of specific molecular and genetic therapeutic strategies that could target critical steps in the immunopathogenesis of disease without the untoward side-effects of nonspecific generalized immune suppression that still remains the standard of care today.

Photodynamic biologic tissue glue in perforating rabbit corneal wounds

OBJECTIVE

To evaluate the in vivo wound modulating effects of a new biologic tissue adhesive.

BACKGROUND DATA

Biological tissue glue can serve as an important adjunct technology in the treatment of a number of ocular conditions, including closure of corneal wounds. These experiments were performed to evaluate the wound healing effects of a new photodynamic biologic tissue glue (PBTG) in perforating rabbit corneal incisions.

METHODS

Perforating corneal wounds were created in 12 pigmented rabbits. Two perforating incisions were made 180 degrees apart 2 mm from the limbus. One incision in each eye was closed with a single interrupted 10-0 nylon suture, and the other closed with PBTG. Rabbits were followed biomicroscopically and sacrificed at 1-, 3-, and 7-week intervals for histological evaluation of their corneal wounds.

RESULTS

There were no clinical signs of PBTG-related toxicity in any of the rabbits. Compared to control wounds, all glued corneas had greater epithelial filling, less stromal edema, and fewer inflammatory cells at the 1-, 3-, and 7-week stages and showed greater overall wound maturation.

CONCLUSION

Our data suggest that PBTG is an effective and nontoxic tissue adhesive that accelerates normal corneal wound healing.

ICAM-1 deficiency suppresses host allosensitization and rejection of MHC-disparate corneal transplants

BACKGROUND

We used a murine model of orthotopic corneal transplantation to determine whether host deficiency in ICAM-1 promotes survival of corneal grafts with different degrees of allodisparity.

METHODS

ICAM-1-/- and wild-type C57BL/6 (ICAM-1+/+) received corneal grafts from the following strains of mice: BALB/c (fully mismatched), BALB.b (mismatched at multiple minor H only), or B10.D2 [including major histocompatibility complex (MHC) mismatch]. Graft rejection, induction of allospecific delayed-type hypersensitivity (DTH) responses, and leukocytic infiltration of grafts were measured.

RESULTS

There were no differences in long-term survival of allografts that were either fully mismatched or had only minor H disparity in ICAM-1+/+ vs. ICAM-1-/-hosts. However, whereas B10.D2 grafts were accepted in only 58% of the ICAM-1+/+ hosts, graft survival in ICAM-1-/- recipients was 100% (P=0.006). Moreover, none of the ICAM-1-/- mice receiving B10.D2 grafts developed allospecific DTH.

CONCLUSIONS

Prolonged survival seen in MHC-mismatched grafts in ICAM-1-/- mice, along with a suppressed DTH response to donor alloantigens after transplantation, suggest that ICAM-1 is associated with recipient sensitization to MHC alloantigens.

Prevention of allergic eye disease by treatment with IL-1 receptor antagonist

PURPOSE

To determine the impact of interleukin-1 (IL-1) inhibition using IL-1 receptor antagonist (IL-1Ra) in a mouse model of allergic eye disease.

METHODS

A/J mice sensitized and challenged with cat dander in the eye were treated with topical IL-1Ra or vehicle alone. Control mice were treated with IL-1Ra or vehicle but sensitized and challenged with phosphate-buffered saline alone. Immediately after the final allergen challenge, the mice were observed for behavioral changes and assessed for lid injection and chemosis. The animals were then killed, eyes and attached lids were removed for either RNA extraction or histology, and draining lymph nodes were removed for either RNA extraction or in vitro stimulation assays. Differences in chemokine message between experimental and control groups-were determined by RNase protection assays.

RESULTS

Treatment with IL-1Ra in allergen-challenged animals significantly reduced allergen-induced changes in photosensitivity (60%, P = 0.0002), chemosis (50%, P = 0.0151), and injection (86.7%, P = 0.0068) compared with vehicle-treated controls. Interleukin-1Ra reduced the number of degranulated mast cells and caused a significant reduction in the number of eosinophils infiltrating the conjunctival matrix (P<0.001) after allergen challenge. Examination of chemokine mRNA taken from the conjunctiva and draining lymph nodes by RNase protection assay showed a profound decrease in the production of a number of C-C chemokines.

CONCLUSIONS

These findings suggest that IL-1Ra is suppressing allergic eye disease by a down-modulation of the recruitment of eosinophils and other inflammatory cells essential for the immunopathogenesis of ocular atopy.

Differential chemokine gene expression in corneal transplant rejection

PURPOSE

To evaluate the differential gene expression of chemokines after corneal transplantation and to determine the chemokines associated with allograft rejection.

METHODS

Orthotopic mouse corneal transplantation was performed in two fully mismatched-strain combinations using C57BL/6 (H-2b) and BALB/c (H-2d) mice as recipients and BALB/c and C57BL/6 mice as donors. Normal nonsurgical eyes served as negative control specimens and syngeneic transplants (isografts) as control specimens for the alloimmune response. Chemokine gene expression in accepted and rejected allografts and appropriate control specimens was determined by a multiprobe RNase protection assay system.

RESULTS

In eyes with rejected allografts, there was overexpression of regulated on activation normal T-cell expressed and secreted (RANTES), macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, MIP-2, and monocyte chemotactic protein (MCP)-1 in both C57BL/6 and BALB/c recipients. In addition, C57BL/6 eyes with rejected allografts expressed very high levels of interferon-gamma-inducible protein of 10 kDa (IP-10) mRNA, in contrast to BALB/c eyes with rejected allografts, in which IP-10 expression remained very low. In contrast, lymphotactin gene expression increased only slightly in rejected allografts, and eotaxin mRNA, which was also detected in normal eyes, remained unchanged among isograft and allograft groups. T-cell activation gene (TCA)-3 mRNA was not detected in any of the assayed eyes.

CONCLUSIONS

Increased expression of mRNA for select chemokines of the CXC (alpha) and CC (beta) families is associated with corneal allograft rejection. Significantly elevated IP-10 gene expression in high-rejector C57BL/6, but not in low-rejector BALB/c, hosts suggests that differential activation of chemokines may be related to differences in alloimmune reactivity observed among different murine strains.

Role of tumor necrosis factor receptors TNFR-I (P55) and TNFR-II (P75) in corneal transplantation

BACKGROUND

To determine the role of tumor necrosis factor-alpha (TNF-alpha) receptor (TNFR) function in corneal allograft immunology.

METHODS

Animals with gene-targeted deficiency in TNFR-I (p55-/-), TNFR-II (p75-/-), or combined TNFR-I/TNFR-II deficiency (p55-/-p75-/-) and their wild-type controls were used as recipients of fully-mismatched (BALB/c; n=88) or multiple minor alloantigen-mismatched (BALB.b; n=62) orthotopic corneal transplants to determine the effect of selective deficiency in one or both TNF-alpha receptors on corneal allograft survival. Grafted recipients were followed biomicroscopically for signs of rejection, and survival data were analyzed by the Kaplan-Meier method.

RESULTS

There was no discernible difference in survival of fully-mismatched BALB/c corneal grafts in p55-/- (n=12; P=0.76) or in double-knockout p55-/-p75-/- (n=13; P=0.41) as compared with wild-type C57BL/6.129 hosts. However, the survival of BALB/c allografts was lower in p75-/- (n=10; median survival 20 days) as compared with control C57BL/6 (n=30; median survival 30 days) hosts (P=0.02). In contrast, there was no discernible effect in survival of minor alloantigen-disparate BALB.b corneal grafts in p75-/- (n=13; P=0.95) or in combined p55-/-p75-/-(n=10; P=0.17) hosts as compared with C57BL/6 (n=9) and C57BL/6.129 (n=10) wild-type controls, respectively. However, there was a profound enhancement in the survival of BALB.b allografts in p55-/- recipients (n= 10; median survival 35 days) as compared to wild-type C57BL/6.129 (n=10; median survival 25 days) controls (P<0.01).

CONCLUSIONS

Our data suggest that the two TNF-alpha receptors largely play discrete roles in mediating rejection of murine corneal allografts. TNFR-I (p55) function seems to be integral to the rejection of minor-disparate grafts, and its selective suppression leads to enhancement of allograft survival. In contrast, TNFR-II (p75) function appears to be associated with enhanced survival of major histocompatibility complex-disparate allografts. The combined deletion of TNFR functionality in p55-/-p75-/- confers no net advantage or disadvantage to major histocompatibility complex or minor alloantigen-disparate grafts.

Androgens and dry eye in Sjögren's syndrome

Sjögren's syndrome is an extremely complex and currently incurable autoimmune disorder, which occurs primarily in females, and is associated with lacrimal gland inflammation, meibomian gland dysfunction, and severe dry eye. We hypothesize that androgen deficiency, which reportedly occurs in primary and secondary Sjögren's syndrome (e.g., systemic lupus erythematosus, rheumatoid arthritis), is a critical etiologic factor in the pathogenesis of dry eye syndromes. We further hypothesize that androgen treatment to the ocular surface will promote both lacrimal and meibomian gland function and alleviate both "aqueous-deficient" and "evaporative" dry eye. Our results demonstrate that androgens regulate both lacrimal and meibomian gland function, and suggest that topical androgen administration may serve as a safe and effective therapy for the treatment of dry eye in Sjögren's syndrome.

Expression of cell adhesion molecules on limbal and neovascular endothelium in corneal inflammatory neovascularization

PURPOSE

To investigate the expression of cell-adhesion molecules on corneolimbal and neovascular endothelium and the associated leukocyte infiltration in an experimental model of inflammatory corneal neovascularization (NV).

METHODS

Corneal NV was induced in BALB/c mice by placement of nylon sutures. Interleukin-1 receptor antagonist (IL-1ra) was used topically to determine whether suppression of IL-1 could affect adhesion molecule expression and leukocytic infiltration. At set time points, corneal samples were analyzed immunohistochemically for expression of P-selectin, E-selectin, intercellular adhesion molecule (ICAM)-1, vascular adhesion molecule (VCAM)-1, and platelet- endothelial adhesion molecule (PECAM)-1. Leukocytic infiltration at different time points was quantified histologically. In companion experiments mice deficient in ICAM-1 were investigated to determine the functional relevance of this molecule in corneal leukocyte infiltration.

RESULTS

Significant enhanced expression of ICAM-1 was detected on the corneolimbal vascular endothelium as early as 8 hours and on the newly formed corneal NV by day 3, and treatment with IL-1ra led to significant suppression of this expression. IL-1ra-induced suppression of ICAM-1 expression was accompanied by a profound decrease in corneal leukocytic infiltration by 44.6% at day 1 (P < 0.003), 71.8% at day 3 (P < 0.001), 60.1% at day 7 (P < 0.001), and 63.8% at day 14 (P < 0.001), compared with control corneas. Similarly, in ICAM-1 knockout mice, the corneal leukocytic infiltration was 50.3%, 52.9%, and 36.4%, compared with wild-type control animals on day 1 (P < 0.001), day 7 (P < 0.005), and day 14 (P < 0.001), respectively. Expression of PECAM-1 was constitutively present on perilimbal vascular endothelium and had no response to IL-1ra treatment. No significant expression of P-selectin, E-selectin, or VCAM-1 was detected in this experimental model.

CONCLUSIONS

These results suggest that leukocytic infiltration in this model of inflammatory corneal NV is closely associated with ICAM-1 expression, and that topical IL-1ra displays corneal anti-inflammatory effects, largely by suppressing ICAM-1 expression on vascular endothelial cells.

Early expression of proinflammatory cytokines interleukin-1 and tumor necrosis factor-alpha after corneal transplantation

This study's aim was to determine the early postoperative expression of proinflammatory cytokines interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) by corneal grafts. BALB/c (n = 90) and C57BL/6 (n = 90) murine recipients were grafted with donor corneas from either syngeneic or allogeneic mice. At 7 and 14 days after surgery, corneal grafts were excised and the recipient rims separated from the donor tissue. Corneal segments were cultured and assayed for cytokines by enzyme-linked immunosorbent assay (ELISA). There was profound upregulation in expression of both IL-1alpha and TNF-alpha after corneal transplantation. Among both low-rejecting BALB/c and high-rejecting C57BL/6 hosts, levels of IL-1alpha were significantly (p < 0.01) more marked in allogeneic as compared to syngeneic grafts. TNF-alpha overexpression was similarly more marked in allogeneic as compared to syngeneic grafts in both BALB/c and C57BL/6 hosts, although the difference was generally more marked among high-rejecting C57BL/6 recipients. In the case of both IL-1alpha and TNF-alpha, the principal source of cytokine expression in the transplanted tissue was the recipient rim. There is significant overexpression of both IL-1alpha and TNF-alpha during the first 2 weeks after transplantation in both syngeneic and allogeneic orthotopic corneal grafts. However, whereas in syngeneic grafts cytokine expression generally decreases after the first postoperative week, significantly elevated cytokine levels are sustained in allogeneic grafts, implicating IL-1 and TNF-alpha as mediators of the alloimmune response in corneal transplantation.

Does androgen insufficiency cause lacrimal gland inflammation and aqueous tear deficiency?

PURPOSE

The current investigators have shown that androgen treatment suppresses inflammation and stimulates the function of lacrimal glands in mouse models of Sjögren's syndrome. Recently, others have hypothesized that androgen insufficiency induces an autoimmune process in lacrimal tissue, leading to inflammation, a Sjögren's syndrome-like pathology, and aqueous tear deficiency. The purpose of the present study was to test this hypothesis.

METHODS

Lacrimal glands were obtained from adult testicular feminized (Tfm) and control mice; castrated rats, guinea pigs, and rabbits; and castrated rats without anterior or whole pituitary glands and were processed for histology and image analysis. Tear volumes were measured in mice, in patients taking antiandrogen medications, and in age-matched human control subjects.

RESULTS

Tfm mice, which are completely resistant to classical androgen action, did not have increased lymphocyte infiltration in their lacrimal glands or decreased tear volumes. No inflammation was evident in lacrimal tissues of male or female rats, guinea pigs, or rabbits 12 to 31 days after castration, no inflammation existed in rat lacrimal glands 15 to 31 days after orchiectomy and pituitary removal, and no aqueous tear deficiency was apparent in patients receiving antiandrogen therapy.

CONCLUSIONS

Androgen deficiency may promote the progression of Sjögren's syndrome and its associated lacrimal gland inflammation, meibomian gland dysfunction, and severe dry eye. However, androgen insufficiency alone does not cause lacrimal gland inflammation, a Sjögren's syndrome-like pathology in lacrimal tissue, or aqueous tear deficiency in nonautoimmune animals and humans.

High levels of plasma C-reactive protein and future risk of age-related cataract

PURPOSE

Chronic intraocular inflammation, with or without systemic inflammation, is associated with increased risk of cataract. Whether systemic inflammation alone is associated with cataract is unknown. This study examined the association between plasma C-reactive protein (CRP), a marker of systemic inflammation, and risk of cataract.

METHODS

In the Physicians' Health Study, we recently analyzed plasma CRP levels in baseline blood specimens from 543 men who later developed cardiovascular disease, and 543 who did not. These data provided a cost-efficient means to explore whether baseline plasma CRP is associated with future risk of age-related cataract. After excluding 252 men with prior diagnosis of cataract or missing data, we followed the remaining 834 men defined by baseline CRP level for 11 years for incident cataract. We used proportional hazards regression models, stratified by cardiovascular disease status.

RESULTS

Baseline CRP was significantly higher among men who later developed cataract than levels among those who remained free of cataract, P = 0.02 (median 1.53 versus 1.23 mg/L). In a multivariable model adjusted for cardiovascular disease, randomized aspirin and beta carotene assignments, age, diabetes, cigarette smoking, alcohol consumption, body mass index, exercise, and parental history of myocardial infarction, the levels of CRP remained significantly associated with development of cataract (P = 0.001); but the association was less significant in a model using log CRP levels (P = 0.038). In exploratory analyses of a threshold effect, the excess risk was significant only among men with levels at or above the 97.5th centile (6.17 mg/L); compared to those with lower levels, the relative risk in these men was 3.00 (95% confidence interval, 1.53 to 5.91; P = 0.002). Relative risks associated with CRP levels at or above versus below the 85th, 90th, and 95th percentiles were not significant (relative risks 1.29, 1.50, and 1.77, respectively).

CONCLUSIONS

Overall, our results suggest that elevated levels of CRP are associated with future risk of cataract in these apparently healthy men. This early report raises the possibility that systemic inflammation may play a role in the pathogenesis of age-related cataract.

Corneal transplantation in young children with congenital hereditary endothelial dystrophy. Multicenter Pediatric Keratoplasty Study

PURPOSE

To describe the surgical success rate and visual results of penetrating keratoplasty in a series of young children with congenital hereditary endothelial dystrophy and to summarize the current literature on outcomes of keratoplasty for congenital hereditary endothelial dystrophy, with particular attention to the timing of surgery.

METHODS

The authors conducted a retrospective study of children aged 12 years and younger who underwent penetrating keratoplasty between 1975 and 1994 at four participating eye centers, and who were followed for at least 6 months postoperatively. For this report, 21 corneal transplants performed in 16 eyes of nine patients with congenital hereditary endothelial dystrophy were studied. Patients' median age at the time of first keratoplasty was 40 months (range, 3 months to 10 years).

RESULTS

During a mean follow-up period of over 70 months (range, 6 to 240 months), 11 (69%) of 16 eyes retained full graft clarity. The 2-year survival rate of first grafts was 71% (95% confidence interval, 47% to 95%). Postoperative visual acuity improvement of 1 or more Snellen lines was seen in five of 10 eyes in which the patients were old enough for accurate assessment of visual acuity; however, just four of these 10 eyes attained a visual acuity of 20/200 or better.

CONCLUSIONS

Penetrating keratoplasty for congenital hereditary endothelial dystrophy in children has a reasonable chance of surgical success when performed at a young age; however, the prognosis for improved visual acuity in children appears to be more guarded. Decisions on the timing of surgical intervention for congenital hereditary endothelial dystrophy should be made on a case-by-case basis. Although the threat of irreversible amblyopia in untreated eyes and good surgical success rates even among very young children argue for the consideration of relatively early surgical intervention in the most severely affected cases, there is evidence to support delaying surgery in some cases.

TNF-alpha regulates corneal Langerhans cell migration

Langerhans cells (LC) belong to the dendritic cell family and mediate Ag presentation in the cornea and ocular surface. Under normal physiological conditions, the central cornea is devoid of LC. Centripetal migration of LC plays a critical role in promoting immunoinflammatory responses in the eye including allograft rejection and herpetic keratitis. The molecular mechanisms responsible for ocular LC migration are poorly understood. To examine whether TNF-alpha mediates corneal LC migration and to establish the interaction of IL-1 and TNF-alpha in regulating LC migratory capacity, we utilized gene-targeted knockout mice lacking IL-1 receptor I (IL-1RI-/-), TNF receptor I (p55-/-), TNF receptor II (p75-/-), or both (p55-/-p75-/-). LC migration was induced by thermal cautery or cytokine injection and enumerated by an immunofluorescence assay. Migration of LC after cauterization and TNF-alpha injection was significantly depressed in both p55-/- and p75-/- mice. Similarly, in the first 72 h after intracorneal injection of IL-1alpha, LC migration was reduced in p55-/-, p75-/-, and p55-/-p75-/- mice. In contrast, injection of TNF-alpha in IL-1RI-/- mice led to normal migration of corneal LC indistinguishable from wild-type controls. These results suggest that the IL-1 induction of corneal LC migration is largely mediated by TNFR function, whereas TNF-alpha induction of LC migration is independent of IL-1RI activity. Moreover, the data suggest that both p55 and p75 signaling pathways are important in mediating LC migration in the cornea.

Corneal transplantation in antibody-deficient hosts

PURPOSE

To examine the role of donor-specific antibodies, with or without complement, in rejection of orthotopic corneal transplants by using mice as recipients in which the genes for the heavy chain of immunoglobulin or the third complement component have been eliminated by homologous recombination.

METHODS

BALB/c corneas were transplanted into eyes of B-cell-deficient (n=17) or wild-type control C57BL/6 (n=30) mice and into eyes of complement (C3)-deficient (n=15) or wild-type control 129-C57BL/6 (n=13) mice. After surgery all grafts were evaluated over 8 weeks in a masked manner by biomicroscopy for signs of rejection.

RESULTS

The rates of corneal transplant rejection were similar among B-cell-deficient and C3-deficient mice compared with rejection rates in their respective wild-type control subjects. This similarity applied to the time course of rejection and to cumulative survival rates.

CONCLUSIONS

Neither donor-specific antibody nor the third component of complement play essential roles in acute rejection of orthotopic corneal allografts in mice.

Interleukin 1 receptor antagonist suppresses allosensitization in corneal transplantation

OBJECTIVE

To delineate the mechanisms by which topical interleukin 1 receptor antagonist (IL-1RA) treatment promotes orthotopic corneal allograft survival.

METHODS

Corneal buttons were prepared from eyes of C57BL/6 mice and placed orthotopically in normal or neovascularized (high-risk) eyes of BALB/c mouse recipients. Topical IL-1RA (or vehicle alone) was applied to grafts 3 times daily until the grafted eyes were enucleated. Corneal specimens were evaluated for content of Langerhans cells. A week after enucleation, 1 group of recipients was tested for allospecific delayed-type hypersensitivity elicited by intrapinnae injections of donor splenocytes. In companion experiments, a second group of mice that underwent transplantation, IL-1RA treatment, and enucleation was challenged with orthotopic skin grafts from B10.D2 donor mice (sharing minor H antigens with C57BL/6 mice) to determine whether the second group of mice could reject grafts bearing corneal donor minor H alloantigens in an accelerated fashion.

RESULTS

Mice whose orthotopic corneal allografts were treated topically with IL-1RA acquired neither donor-specific delayed-type hypersensitivity (P<.001) nor the capacity to reject orthotopic donor-type skin allografts in an accelerated manner (P<.05), whereas controls treated with vehicle alone developed delayed-type hypersensitivity and rejected B10.D2 grafts in an accelerated manner. Moreover, IL-1RA-treated grafts placed in both high-risk (P = .01) and normal-risk (P = .004) eyes displayed significantly reduced levels of infiltrating Langerhans cells compared with vehicle-treated controls.

CONCLUSIONS

Topical IL-1RA promotes corneal allograft survival in large part by preventing activity of recipient Langerhans cells, and thereby preventing these cells from inducing systemic allosensitization. These data suggest that IL-1 plays a key role in promoting allosensitization when corneal allografts are placed orthotopically.

CLINICAL RELEVANCE

Suppression of allosensitization by topical IL-1RA may prove a clinically useful method for enhancing corneal transplant survival.

Topical modulation of interleukin-1 activity in corneal neovascularization

PURPOSE

To determine whether inflammatory corneal neovascularization (CNV) is associated with interleukin-1 (IL-1) activity and if so, to assess the efficacy of topical interleukin-1 receptor antagonist (IL-1ra) to suppress CNV.

METHODS

Inflammatory CNV was induced on day 0 by placement of paracentral intrastromal sutures in BALB/c murine eyes. Quantification of IL-1alpha and -beta cytokine levels was done by a sandwich enzyme-linked immunosorbent assay (ELISA) on the supernatants of incubated corneas excised at specified time points after induction of CNV (n = 6 per time point studied). To study suppression of CNV by IL-1ra, animals were divided into treatment subgroups that received topical 20 mg/ml of IL-1ra mixed in 0.2% sodium hyaluronate (n = 28) or placebo (vehicle) alone (n = 22) 3 times daily during days 0-35. Other groups of animals received placebo for 1 (n = 10) or 2 (n = 14) weeks before being switched and retained on IL-1ra. Neovascularization was assessed biomicroscopically and graded by using a standardized scheme.

RESULTS

Induction of CNV stimulus was associated with a significant surge in the expression of both IL-1alpha (p < 0.001) and IL-1beta (p < 0.001) as early as 2 h after the stimulus, which peaked at 24 h, before decreasing substantially in the case of IL-1beta and returning to basal levels by day 7. Topical application of IL-1ra led to a significant suppression of CNV for the duration of therapy only if initiated early after induction of the neovascular stimulus. Initiation of therapy 1 week after CNV induction was associated only with a transient suppression in the angiogenic response.

CONCLUSION

Our data strongly implicate IL-1 as a critical mediator in the early phase of CNV and suggest that IL-1ra can be an effective modality in suppressing CNV if initiated sufficiently early after the inflammatory neovascular stimulus.

A systematic overview of the incidence of posterior capsule opacification

OBJECTIVE

Reported rates of posterior capsule opacification (PCO) vary widely and are based on various definitions of PCO, varying lengths and intervals of follow-up, and the use of different surgical techniques, intraocular lens (i.o.l.) designs, and methods of IOL implantation. This study was designed to obtain a more precise overall estimate of the incidence of PCO and to explore factors that might influence the rate of PCO development.

DESIGN

A meta-analysis.

METHODS

Published articles were selected for study based on a computerized MEDLINE search of the literature and a manual search of the bibliographies of relevant articles. Articles meeting selected inclusion criteria were reviewed systematically, and the reported data were abstracted and synthesized using the statistical techniques of meta-analysis.

MAIN OUTCOME MEASURE

Pooled estimates of the proportion of eyes developing PCO at three postoperative timepoints--1 year, 3 years, and 5 years--were measured.

RESULTS

There is significant heterogeneity among published rates of PCO. The overall pooled estimates (95% confidence limits) of the incidence of PCO were 11.8% (9.3%-14.3%) at 1 year, 20.7% (16.6%-24.9%) at 3 years, and 28.4% (18.4%-38.4%) at 5 years after surgery. There is no evidence of a significant decline in PCO incidence during the study period.

CONCLUSIONS

Visually significant PCO develops in more than 25% of patients undergoing standard extracapsular cataract extraction or phacoemulsification with posterior chamber intraocular lens implantation over the first 5 years after surgery. Patient characteristics, surgical techniques, and differences in research design and reporting may account for some of the variability in reported rates. However, no specific factors were identified in the authors' analysis. More precise estimates of incidence and identification of risk factors for PCO will depend on the development of a standardized measurement of PCO and wider adoption of more rigorous study methodology.

The epidemic of Acanthamoeba keratitis: where do we stand?

PURPOSE

To review from a historical perspective the recent epidemic of Acanthamoeba keratitis and its association with the use of contact lenses and to provide a summary of recent techniques that have allowed earlier diagnosis and treatment.

METHODS

The authors reviewed available literature on Acanthamoeba keratitis from 1973 to the present, with emphasis on the history of the epidemic and its association with contact lenses, identification of risk factors, preventive measures, and current diagnostic techniques. We also estimated the annual incidence of Acanthamoeba keratitis during 1985 through 1987 from available data.

RESULTS

Before the popularization of soft-contact-lens wear, Acanthamoeba keratitis was extremely rare; however, an epidemic began in the early 1980s, and the number of cases increased dramatically beginning in 1984. By 1985, the association of this infection with the use of contact lenses was firmly established, and in 1987, the infection was shown to occur more commonly among men, as well as in contact-lens wearers who failed to disinfect their lenses as frequently as recommended, swam while wearing lenses, or used homemade instead of commercially prepared saline solution. Adoption of "disposable" contact lenses in the late 1980s did not decrease the risk of Acanthamoeba keratitis, and concerns remain regarding the effectiveness of some contact-lens disinfectants; however, recent advances in diagnosis and treatment have improved the prognosis. The annual incidence during 1985 through 1987 was conservatively estimated at 1.65 to 2.01 cases per million contact-lens wearers. It is unclear whether the incidence is declining.

CONCLUSION

Acanthamoeba keratitis has now been recognized worldwide, and there are clear associations of this infection with improper contact-lens hygiene, particularly contact with water. Recent methods allow earlier diagnosis and thus improved outcomes. The epidemic provides a valuable lesson on how a new technology can be associated with unforeseen complications and exemplifies how rapid dissemination of epidemiologic information can aid in controlling an emergent epidemic.

Interleukin-1 receptor antagonist suppresses Langerhans cell activity and promotes ocular immune privilege

PURPOSE

To determine whether the capacity of Langerhans cells (LCs) to abrogate ocular immune privilege can be suppressed by the topical application of interleukin-1 receptor antagonist (IL-1ra).

METHODS

Cautery was applied to corneas of BALB/c mice on day 0 to induce centripetal migration of LCs. Immune privilege was tested by the ability to induce anterior chamber-associated immune deviation (ACAID) to intracamerally injected soluble antigen 1 to 2 weeks after cautery application. The number of LCs was enumerated by immunofluorescent staining. In other experiments, freshly procured Thy-1-depleted epidermal cells, with or without LC depletion, were injected directly into virgin murine corneas before testing for ACAID. All test animals were randomized for treatment with either topical IL-1ra or placebo in a masked fashion for 1 to 2 weeks after induction of LC migration and before intracameral injection of antigen.

RESULTS

Intracorneal injection of freshly procured LC-depleted epidermal cells into normal eyes failed to abrogate ACAID, whereas LC-containing cell populations uniformly led to loss of immune privilege (P < 0.01). Topical treatment with IL-1ra led to retention of the cauterized eyes' capacity for ACAID induction (P < 0.01) and to a profound (>80%) suppression of LC migration compared with untreated controls (P < 0.01). Additionally, topical IL-1ra treatment of eyes with intracorneally injected LCs preserved immune privilege and ACAID induction (P < 0.001).

CONCLUSIONS

IL-1 mediates mechanisms of immunity in corneal inflammation that subvert the normal eye's immune privileged state. However, its antagonism with topical administration of IL-1ra preserves ocular immune privilege and ACAID through suppression of LC function.

Corneal transplantation in children with Peters anomaly and mesenchymal dysgenesis. Multicenter Pediatric Keratoplasty Study

OBJECTIVE

The purpose of the study is to describe graft and visual outcomes of penetrating keratoplasty among young children with Peters anomaly and associated mesenchymal dysgeneses.

DESIGN

The design was a multicenter retrospective analysis of the indications and outcome in pediatric keratoplasty.

PARTICIPANTS

The records of all children aged 12 years and younger who underwent penetrating keratoplasty for mesenchymal dysgenesis between January 1975 and May 1993 at the participating centers were reviewed.

MEASURES

The data were analyzed regarding graft survival and postoperative visual acuity.

RESULTS

Forty-seven corneal transplants in 36 eyes of 29 patients with mesenchymal dysgenesis were studied. The majority of eyes operated on (30) had Peters anomaly (83%). Patients' mean age at the time of keratoplasty was 7 months. After a mean follow-up period of 38 months, 61% of eyes retained full graft clarity. One and 3-year survival rates were 79% (95% confidence interval [CI] = 65%-93%) and 62% (95% CI = 45%-79%), respectively. Postoperative corneal ulcers/nonhealing epithelial defects (P = 0.03), and additional noncorneal surgical procedures at the time of transplantation (P = 0.05) were associated with graft failure. Provision of postoperative optical aids (P = 0.01) was associated with better postoperative visual acuity levels.

CONCLUSIONS

Penetrating keratoplasty for Peters anomaly and related mesenchymal dysgeneses in young children has a reasonable chance of success during the critical years of visual maturation and is associated with satisfactory visual results in one third to half the cases. The data suggest that complicated cases requiring additional surgical procedures have a worse prognosis.

Immunity causing blindness: five different paths to herpes stromal keratitis

Herpes stromal keratitis (HSK) is a blinding infectious disease that results from an array of immunopathogenic processes, including herpes simplex virus 1 (HSV-1)-specific T helper 1 (Th1) and Th2 cells, cytotoxic T cells and antibodies. As discussed here by Wayne Streilein and colleagues, strategies designed to prevent and treat this syndrome must be aware of the fact that the disease is multifactorial in its cause and pathogenesis.

Posterior capsule opacification after cataract surgery in patients with uveitis

PURPOSE

To compare the incidence rate of posterior capsule opacification (PCO) after phacoemulsification and standard extracapsular cataract extraction (P/ECCE) in eyes with antecedent uveitis with the incidence rate in eyes without any history of intraocular inflammation.

DESIGN

Review of records of 108 eyes of 78 patients with uveitis and 122 eyes of 106 patients with no uveitis who underwent P/ECCE. Rates of PCO were compared by the log-rank test of differences in the Kaplan-Meier survival curves. Proportional hazards regression models provided estimates of the relative risks of PCO among uveitic compared to nonuveitic eyes.

MAIN OUTCOME MEASURES

Performance of neodymium: YAG laser posterior capsulotomy was used as a proxy measure for the main outcome of visually significant PCO.

RESULTS

Study patients ranged in age from 6 to 81 years (median, 44.5 years) among those with uveitis and 27 to 96 years (median, 68.5 years) among those without uveitis (P = 0.0001). Crude incidence rates for visually significant PCO were 54% over a mean follow-up of 4.3 years in uveitic cases and 40% over a mean follow-up of 3.9 years among nonuveitic cases (P = 0.02). Estimates of PCO incidence (95% confidence interval) in uveitic eyes derived from the Kaplan-Meier models were 38.5% (range, 28.9%-48.2%) at 1 year and 56% (range, 45.8%-66.3%) at 3 years, and estimates among nonuveitic eyes were 11.5% (range, 6.2%-16.8%) at 1 year and 38.4% (range, 29%-47.8%) at 3 years. These rates of PCO among patients with uveitis and those patients without uveitis differed significantly by the log-rank test (P = 0.004). However, after adjusting for the younger age of patients with uveitis, the rates of PCO were no longer statistically different.

CONCLUSIONS

The apparent higher rate of PCO in patients with uveitis is primarily due to their younger age at the time of surgery. A moderately increased independent risk of PCO from uveitis cannot, however, be ruled out by this study.

Topical interleukin 1 receptor antagonist promotes corneal transplant survival

BACKGROUND

Interleukin (IL)-1 is a potent proinflammatory cytokine that plays a critical role in initiating and maintaining immunogenic inflammation. We performed a series of experiments to determine whether the topical application of IL-1 receptor antagonist (IL-1ra) can prolong corneal transplant survival in the murine model of orthotopic allotransplantation.

METHODS

For all experiments, C57BL/6 corneas were transplanted into BALB/c (major histocompatibility and minor histocompatibility-disparate) eyes. "High-risk" transplants were transplants that had been sutured into BALB/c recipient beds with corneal neovascularization induced by placement of three interrupted sutures in the host cornea 2 weeks earlier. Both risk groups were divided in a masked fashion into treatment subgroups that received either 20 mg/ml of IL-1ra mixed in 0.2% sodium hyaluronate vehicle (n=28) or placebo alone (n=25). All transplants were evaluated for 8 weeks after surgery for signs of rejection. At the end of follow-up, corneal specimens were processed for enumeration of Langerhans cells and histopathological evaluation.

RESULTS

Survival rates of both normal-risk and high-risk transplants increased significantly among the IL-1ra-treated animals compared with untreated controls by both stratified Mantel-Haenszel (P=0.02) and Kaplan-Meier survival (P=0.03) analyses. Furthermore, both normal- and high-risk IL-1ra-treated grafts had significantly less inflammation and Langerhans cells infiltration compared with untreated controls.

CONCLUSIONS

Topical treatment with IL-1ra has a significantly positive effect in promoting corneal allograft survival.

Corneal topography after selective suture removal for astigmatism following keratoplasty

BACKGROUND AND OBJECTIVE

The authors sought to determine whether the immediate corneal topographic changes induced by selective suture removal for astigmatism after keratoplasty were stable over time.

PATIENTS AND METHODS

Computerized videokeratoscopic images were obtained prior to and immediately following suture removal in 14 patients, and then again at the next postoperative visit 4 to 6 weeks later. These images were analyzed and statistically compared for central corneal power and vector of the central 3-mm corneal astigmatism.

RESULTS

Most of the topographic changes induced by suture removal occurred immediately. However, continued shifting in corneal curvature did take place over the subsequent 4 to 6 weeks. Unpredictable shifts were more pronounced in patients whose surgery had been performed more than 20 months prior to suture removal.

CONCLUSION

Computerized videokeratoscopy graphically elucidates continued shifts in corneal topography following the removal of sutures for the control of astigmatism after keratoplasty.

Visual outcomes prognosticators in juvenile rheumatoid arthritis-associated uveitis

PURPOSE

The purpose of the study is to delineate the visual prognosticators in juvenile rheumatoid arthritis-associated uveitis.

METHODS

The records of 43 patients with juvenile rheumatoid arthritis-associated uveitis who were observed for at least 6 months were studied retrospectively. Bivariate and multivariate statistical models were applied to more than 40 parameters to determine the relative odds of visual rehabilitation among patients with each characteristic.

RESULTS

Thirty-seven (86%) patients were females and 6 (14%) males. The mean known age of uveitis onset was 13 years, with females having, on average, 4 years earlier onset of disease compared to males (P = 0.04). Ninety-three percent had chronic, 5% had recurrent, and 2% had an acute monophasic disease course. Of the 76 affected eyes, 93% were nongranulomatous and 97% had iridocyclitis. The mean overall duration of uveitis was 146 months, with females suffering from a significantly longer duration of active disease than did males (P < 0.001). Nineteen (44%) patients underwent cataract extraction, and 16 (37%) underwent vitrectomy. Thirty (70%) of the patients experienced visual improvement with their therapy. When controlling for potential confounders, male sex (P = 0.006), shorter duration of uveitis (P = 0.007), older age at disease onset (P = 0.02), and a shorter delay in presentation to a subspecialist (P = 0.02) were associated significantly with visual acuity improvement. Visual acuity at presentation (P = 0.001), use of systemic nonsteroidal anti-inflammatory drugs (P = 0.01), older age at disease onset (P = 0.02), absence of glaucomatous neuropathy (P = 0.02), and male sex (P = 0.03) were correlated strongly with a final visual acuity outcome of 20/40 or better.

CONCLUSION

Juvenile rheumatoid arthritis-associated uveitis is a serious disease with a guarded visual prognosis. It is hoped that increased awareness of its prognosticators will lead to treatment and referral patterns that have the best chance of minimizing the likelihood of visual impairment in patients with juvenile rheumatoid arthritis.

Prognosticators for visual outcome in sarcoid uveitis

PURPOSE

The purpose of the study is to delineate the visual prognosticators in sarcoid-associated uveitis given the current standards of care.

METHODS

The records of 60 patients with sarcoid-associated uveitis who were observed for at least 6 months were studied retrospectively. Multivariate regression models using the generalized estimating equations approach to adjust for the correlation between fellow eyes were applied to determine disease, patient, and treatment characteristics that altered the odds of visual rehabilitation.

RESULTS

One hundred twelve eyes of 43 women and 17 men who met the inclusion criteria were identified. Seventy-seven percent of patients were white, 15% black, and 8% of Hispanic origin. Uveitis developed in the patients at a mean age of 42 (range, 4-82) years. Of the 112 affected eyes, 81% had granulomatous and 15% nongranulomatous uveitis. Most patients (66%) had anterior or intermediate uveitis alone. Ninety-one percent had chronically smoldering disease; another 7% had recurrent flares, and only 1 patient had a monophasic acute course to her uveitis. Vision-threatening complications developed in many patients, including 58% in whom cystoid macular edema developed and 25% in whom media opacities developed, requiring cataract surgery or vitrectomy or both. Overall, 34% of treated eyes and 51% of patients had final visual acuities that were superior to their acuities at presentation. The factors most significantly associated with a final visual acuity of worse than 20/40 after controlling for potential confounders were as follows: delay in presentation to a subspecialist (odds ratio [OR] = 2.94, P = 0.05), total duration of uveitis (OR = 1.04, P = 0.09), development of cystoid macular edema (OR = 0.37, P = 0.07) or glaucoma (OR = 4.54, P = 0.02), presence of intermediate (OR = 5.00, P = 0.01) or posterior uveitis (OR = 8.33, P = 0.04), and systemic steroid use (OR = 0.30, P = 0.03) were the parameters most strongly correlated with a lack of visual acuity improvement. Delay in presentation to a subspecialist (OR = 20.00, P = 0.01), development of glaucoma (OR = 50.00, P = 0.005), presence of intermediate (OR = 25.00, P = 0.02) or posterior uveitis (OR = 50.00, P = 0.02), black race (OR = 11.11, P = 0.02), (log) visual acuity at presentation (OR = 0.05, P = 0.0001), and use of systemic steroids (OR = 0.07, P = 0.02).

CONCLUSION

Multivariate outcomes analysis, particularly after correcting for the correlation between fellow eyes, is a useful analytic tool for optimization of standards of care and for disease risk stratification to aid both physicians and patients.