Larry A. Donoso

Genetic variants near TIMP3 and high-density lipoprotein–associated loci influence susceptibility to age-related macular degeneration

We executed a genome-wide association scan for age-related macular degeneration (AMD) in 2,157 cases and 1,150 controls. Our results validate AMD susceptibility loci near CFH (P < 10−75), ARMS2 (P < 10−59), C2/CFB (P < 10−20), C3 (P < 10−9), and CFI (P < 10−6). We compared our top findings with the Tufts/Massachusetts General Hospital genome-wide association study of advanced AMD (821 cases, 1,709 controls) and genotyped 30 promising markers in additional individuals (up to 7,749 cases and 4,625 controls). With these data, we identified a susceptibility locus near TIMP3 (overall P = 1.1 × 10−11), a metalloproteinase involved in degradation of the extracellular matrix and previously implicated in early-onset maculopathy. In addition, our data revealed strong association signals with alleles at two loci (LIPC, P = 1.3 × 10−7; CETP, P = 7.4 × 10−7) that were previously associated with high-density lipoprotein cholesterol (HDL-c) levels in blood. Consistent with the hypothesis that HDL metabolism is associated with AMD pathogenesis, we also observed association with AMD of HDL-c—associated alleles near LPL (P = 3.0 × 10−3) and ABCA1 (P = 5.6 × 10−4). Multilocus analysis including all susceptibility loci showed that 329 of 331 individuals (99%) with the highest-risk genotypes were cases, and 85% of these had advanced AMD. Our studies extend the catalog of AMD associated loci, help identify individuals at high risk of disease, and provide clues about underlying cellular pathways that should eventually lead to new therapies.

Management of posterior uveal melanoma

In recent years, there have been a number of advances in the diagnosis and management of patients with malignant melanoma of the posterior uvea (ciliary body and choroid). This review provides a brief update on the current status of diagnostic modalities, such as fluorescein angiography, ultrasonography, computed tomography, magnetic resonance imaging, fine needle aspiration biopsy, and the radioactive phosphorus uptake test. Following that is a more detailed review of the current controversy regarding the natural course of uveal melanomas and the available therapeutic modalities. Current indications, techniques, complications, and results are provided for various forms of management, such as observation, laser photocoagulation, plaque radiotherapy, charged particle radiotherapy, local tumor resection, enucleation, and orbital exenteration.

Innovations in 3D printing: a 3D overview from optics to organs

3D printing is a method of manufacturing in which materials, such as plastic or metal, are deposited onto one another in layers to produce a three dimensional object, such as a pair of eye glasses or other 3D objects. This process contrasts with traditional ink-based printers which produce a two dimensional object (ink on paper). To date, 3D printing has primarily been used in engineering to create engineering prototypes. However, recent advances in printing materials have now enabled 3D printers to make objects that are comparable with traditionally manufactured items. In contrast with conventional printers, 3D printing has the potential to enable mass customisation of goods on a large scale and has relevance in medicine including ophthalmology. 3D printing has already been proved viable in several medical applications including the manufacture of eyeglasses, custom prosthetic devices and dental implants. In this review, we discuss the potential for 3D printing to revolutionise manufacturing in the same way as the printing press revolutionised conventional printing. The applications and limitations of 3D printing are discussed; the production process is demonstrated by producing a set of eyeglass frames from 3D blueprints.

Space-occupying orbital masses in children. A review of 250 consecutive biopsies.

A review was done of 250 consecutive biopsies for orbital space-occupying lesions in children. Benign cystic lesions were by far the most common, accounting for 52% of the lesions. Inflammatory lesions, usually biopsied to exclude the diagnosis of rhabdomyosarcoma, accounted for 16%. Among the 250 biopsies there were 14 primary malignant tumors (6%), ten of which were rhabdomyosarcoma. Although rhabdomyosarcoma is not the most common space-occupying orbital lesion in children, clinicians should be familiar with its clinical features and proceed with immediate biopsy followed by appropriate irradiation and chemotherapy if the diagnosis is established. However, biopsy should only be undertaken if there is reasonable suspicion that the lesion could be rhabdomyosarcoma or other childhood orbital malignancy.

Efficacy of Panretinal Photocoagulation in Preventing Neovascular Glaucoma Following Ischemic Central Retinal Vein Obstruction

Ninety-three percent of eyes that develop neovascular glaucoma (NVG) following central retinal vein obstruction (CRVO) have an ischemic index greater than 50%. An ischemic index (percentage of retinal capillary nonperfusion) of 50% represents approximately 10 disc areas of retinal ischemia as determined by computer analysis of standard 30 degrees fluorescein angiograms. The difficulties of following patients clinically and angiographically at frequent intervals over extended periods of time, and the tendency for iris neovascularization (NVI) to develop and to progress rapidly to NVG with painful loss of vision emphasizes the importance of early recognition and treatment of high-risk eyes. In this prospective study (1976--81), 100 consecutive eyes with an ischemic CRVO pattern (average ischemic index 82%) received early argon laser panretinal photocoagulation (PRP) and none developed NVG unless another ischemic event occurred following treatment. Prophylactic PRP in high-risk ischemic CRVO eyes appears to eliminate virtually the devastating complications of NVG.

Adaptive changes in visual cell transduction protein levels: Effect of light

Long-term environmental light-mediated changes in visual cell transduction proteins were studied to assess the influence of rearing environment on their levels and their potential effects on intense light-induced retinal damage. The levels of rhodopsin, S-antigen and the alpha subunit of transducin were measured in whole eye detergent extracts, retinal homogenates or rod outer segments isolated from rats reared in weak cyclic light or darkness, and following a change in rearing environment. Rats changed from weak cyclic light to darkness had 22% more rhodopsin per eye than cyclic-light rats after 12-14 days in the new environment. Western trans-blot analysis of retinal proteins from these dark-maintained animals contained 65% higher levels of immunologically detectable alpha transducin; S-antigen levels were approximately 45% lower than in cyclic-light rats. In rats changed from the dark environment to weak cyclic light, rhodopsin levels decreased by 18% during a comparable period; retinal alpha transducin was 35% lower, S-antigen was 30% higher. At various times after the change in rearing environment, some rats were exposed to intense visible light to determine their susceptibility to retinal damage. Two weeks after an 8-hr exposure, cyclic-light reared rats had rhodopsin levels only 10% lower than control (2.1 nmol per eye). However, rhodopsin was 75% lower when cyclic-light rats were maintained in darkness for 2 weeks before intense light. For animals originally reared in darkness, rhodopsin was 78% lower following 8 hr of intense light, whereas only 30% rhodopsin loss occurred in dark-reared rats after previous maintenance for 2 weeks in weak cyclic-light.(ABSTRACT TRUNCATED AT 250 WORDS)

Mucosa specific lymphocytes in the human conjunctiva, corneoscleral limbus and lacrimal gland

Conjunctiva associated lymphoid tissue shows several similarities to mucosa associated lymphoid tissue of the gut and respiratory tract. These similarities have been described in relation to lymphocyte subpopulations and epithelial cell morphology. However, unlike the lymphoid tissue of the gut and respiratory tract, mucosa specific lymphocytes have not been described in the ocular mucosa. In this study we demonstrated the presence of mucosa specific lymphocytes bearing the Human Mucosal Lymphocyte-1 antigen (beta 7 integrin), in the human conjunctiva, limbus and lacrimal gland. The distribution of this subset of lymphocytes corresponded to the distribution of CD8+ T-cells and was found maximally in the epithelium of the epibulbar conjunctiva and in the lacrimal gland. The Human mucosal lymphocyte antigen may function to determine mucosal homing of this particular subset of CD8+ T-cells, which in turn, may have special function in immunological defense and tolerance mechanisms occurring at mucosal surfaces.

An Immunologically Privileged Retinal Antigen Elicits Tolerance Major Role for Central Selection Mechanisms

Immunologically privileged retinal antigens can serve as targets of experimental autoimmune uveitis (EAU), a model for human uveitis. The tolerance status of susceptible strains, whose target antigen is not expressed in the thymus at detectable levels, is unclear. Here, we address this issue directly by analyzing the consequences of genetic deficiency versus sufficiency of a uveitogenic retinal antigen, interphotoreceptor retinoid-binding protein (IRBP). IRBP-knockout (KO) and wild-type (WT) mice on a highly EAU-susceptible background were challenged with IRBP. The KO mice had greatly elevated responses to IRBP, an altered recognition of IRBP epitopes, and their primed T cells induced exacerbated disease in WT recipients. Ultrasensitive immunohistochemical staining visualized sparse IRBP-positive cells, undetectable by conventional assays, in thymi of WT (but not of KO) mice. IRBP message was PCR amplified from these cells after microdissection. Thymus transplantation between KO and WT hosts demonstrated that this level of expression is functionally relevant and sets the threshold of immune (and autoimmune) reactivity. Namely, KO recipients of WT thymi generated reduced IRBP-specific responses, and WT recipients of KO thymi developed enhanced responses and a highly exacerbated disease. Repertoire culling and thymus-dependent CD25+ T cells were implicated in this effect. Thus, uveitis-susceptible individuals display a detectable and functionally significant tolerance to their target antigen, in which central mechanisms play a prominent role.

A humanized model of experimental autoimmune uveitis in HLA class II transgenic mice

Experimental autoimmune uveitis (EAU) is a disease of the neural retina induced by immunization with retinal antigens, such as interphotoreceptor retinoid-binding protein (IRBP) and arrestin (retinal soluble antigen, S-Ag). EAU serves as a model for human autoimmune uveitic diseases associated with major histocompatibility complex (HLA) genes, in which patients exhibit immunological responses to retinal antigens. Here we report the development of a humanized EAU model in HLA transgenic (TG) mice. HLA-DR3, -DR4, -DQ6, and -DQ8 TG mice were susceptible to IRBP-induced EAU. Importantly, HLA-DR3 TG mice developed severe EAU with S-Ag, to which wild-type mice are highly resistant. Lymphocyte proliferation was blocked by anti-HLA antibodies, confirming that antigen is functionally presented by the human MHC molecules. Disease could be transferred by immune cells with a Th1-like cytokine profile. Antigen-specific T cell repertoire, as manifested by responses to overlapping peptides derived from S-Ag or IRBP, differed from that of wild-type mice. Interestingly, DR3 TG mice, but not wild-type mice, recognized an immunodominant S-Ag epitope between residues 291 and 310 that overlaps with a region of S-Ag recognized by uveitis patients. Thus, EAU in HLA TG mice offers a new model of uveitis that should represent human disease more faithfully than currently existing models.

S-antigen: Characterization of a pathogenic epitope which mediates experimental autoimmune uveitis and pinealitis in Lewis rats

S-antigen (48K protein) is a photoreceptor cell protein highly pathogenic for the induction of experimental autoimmune uveitis (EAU) and intimately involved in the visual process. EAU is characterized, in part, as a T-cell mediated autoimmune disease which results in a severe inflammation of the uveal tract, and pineal gland. In order to determine specific sites in S-antigen responsible for its pathogenicity we synthesized twenty-three peptides, corresponding to the entire 404 amino acid sequence, and tested each peptide for its ability to induce EAU in Lewis rats. One peptide, peptide M (18 amino acids in length), was found to be highly pathogenic and consistently induced an EAU that was identical to the disease caused by native S-antigen. Clinically, the disease that developed in the eye was characterized by iris and pericorneal hyperemia, followed by inflammatory exudates in the anterior and vitreous chambers. Histopathologically a severe inflammatory response was observed which resulted in the complete destruction of the photoreceptor cell layer of the retina. In order to more fully characterize this pathogenic site, 14 additional smaller peptides (eight to eighteen amino acids in length) corresponding to the left and right portions of peptide M were synthesized. Of these peptides, peptide M16L, M15L, and M12L induced EAU, further localizing this pathogenic site to a small well-characterized region of S-antigen consisting of twelve amino acids. In addition, animals with ocular inflammatory disease had an associated pinealitis characterized by a lymphocytic infiltration of the subcapsular and central area of the pineal gland. The significance of these findings and the relationship of S-antigen in the pathogenesis of EAU and other autoimmune diseases is discussed.