Cornea

Bron AJ, Argüeso P, Irkec M, Bright FV. Clinical staining of the ocular surface: mechanisms and interpretations. Prog Retin Eye Res 2015;44:36-61.Abstract

In this article we review the mechanism of ocular surface staining. Water-soluble dyes are excluded from the normal epithelium by tight junctions, the plasma membranes and the surface glycocalyx. Shed cells can take up dye. A proportion of normal corneas show sparse, scattered time-dependent, punctate fluorescein uptake, which, we hypothesise, is due to a graded loss of the glycocalyx barrier, permitting transcellular entry into pre-shed cells. In pathological staining, there is little evidence of 'micropooling' at sites of shedding and the term 'punctate erosion' may be a misnomer. It is more likely that the initial event involves transcellular dye entry and, in addition, diffusion across defective tight junctions. Different dye-staining characteristics probably reflect differences in molecular size and other physical properties of each dye, coupled with differences in visibility under the conditions of illumination used. This is most relevant to the rapid epithelial spread of fluorescein from sites of punctate staining, compared to the apparent confinement of dyes to staining cells with dyes such as lissamine green and rose bengal. We assume that fluorescein, with its lower molecular weight, spreads initially by a paracellular route and then by transcellular diffusion. Solution-Induced Corneal Staining (SICS), related to the use of certain contact lens care solutions, may have a different basis, involving the non-pathological uptake of cationic preservatives, such as biguanides, into epithelial membranes and secondary binding of the fluorescein anion. It is transient and may not imply corneal toxicity. Understanding the mechanism of staining is relevant to the standardisation of grading, to monitoring disease and to the conduct of clinical trials.

Karamichos D, Zieske JD, Sejersen H, Sarker-Nag A, Asara JM, Hjortdal J. Tear metabolite changes in keratoconus. Exp Eye Res 2015;132:1-8.Abstract

While efforts have been made over the years, the exact cause of keratoconus (KC) remains unknown. The aim of this study was to identify alterations in endogenous metabolites in the tears of KC patients compared with age-matched healthy subjects. Three groups were tested: 1) Age-matched controls with no eye disease (N = 15), 2) KC - patients wearing Rigid Gas permeable lenses (N = 16), and 3) KC - No Correction (N = 14). All samples were processed for metabolomics analysis using LC-MS/MS. We identified a total of 296 different metabolites of which >40 were significantly regulated between groups. Glycolysis and gluconeogenesis had significant changes, such as 3-phosphoglycerate and 1,3 diphosphateglycerate. As a result the citric acid cycle (TCA) was also affected with notable changes in Isocitrate, aconitate, malate, and acetylphosphate, up regulated in Group 2 and/or 3. Urea cycle was also affected, especially in Group 3 where ornithine and aspartate were up-regulated by at least 3 fold. The oxidation state was also severely affected. Groups 2 and 3 were under severe oxidative stress causing multiple metabolites to be regulated when compared to Group 1. Group 2 and 3, both showed significant down regulation in GSH-to-GSSG ratio when compared to Group 1. Another indicator of oxidative stress, the ratio of lactate - pyruvate was also affected with Groups 2 and 3 showing at least a 2-fold up regulation. Overall, our data indicate that levels of metabolites related to urea cycle, TCA cycle and oxidative stress are highly altered in KC patients.

Crnej A, Omoto M, Dohlman TH, Dohlman CH, Dana R. Corneal inflammation after miniature keratoprosthesis implantation. Invest Ophthalmol Vis Sci 2015;56(1):185-9.Abstract

PURPOSE: To compare corneal inflammation after syngeneic and allogeneic penetrating keratoplasty (PK) with miniature Keratoprosthesis (m-KPro) implantation in mice. METHODS: BALB/C (syngeneic) or C57BL/6 (allogeneic) corneas were transplanted onto BALB/C host beds as part of PK or m-KPro implantation. Corneal inflammation was assessed by determining the frequencies of CD45(+) leukocytes, CD4(+) T cells, CD11b(+) cells, and Gr-1(+) granulocytes/monocytes by flow cytometry at 2, 4, and 8 weeks post transplantation. In addition, expression levels of the proinflammatory cytokines TNF-α and IL-1β were analyzed using real-time qPCR at 8 weeks post transplantation. RESULTS: Cell frequencies in the syngeneic (syn) and allogeneic (allo) m-KPro groups were higher compared with the syngeneic and allogeneic PK groups, respectively, at all time points. However, after week 4, frequencies of all analyzed immune cells were higher in the alloPK group as compared with synKPro group. At 8 weeks, the expression of TNF-α was higher in synKPro, alloPK, and alloKPro groups compared with the naïve and synPK groups. The expression of IL-1β was significantly higher in both KPro groups as compared with PK groups. CONCLUSIONS: Although the m-KPro device augments the inflammatory response in the cornea after its implantation, allogenicity (of the carrier tissue) is also a significant contributor to corneal inflammation. These data suggest that using syngeneic or decellularized corneal tissue as a Boston-KPro carrier could reduce the postoperative inflammation response.

Choi W, Byun YJ, Jung E, Noh H, Hajrasouliha AR, Sadrai Z, Chang EJ, Lee JH, Lee HK. Chemokine decoy receptor D6 mimicking trap (D6MT) prevents allosensitization and immune rejection in murine corneal allograft model. J Leukoc Biol 2015;97(2):413-24.Abstract

Although corneal allotransplantation is performed in the immune-privileged cornea, many grafts are still rejected after transplantation. This study examined the role of chemokine receptor D6 expression in a corneal allograft rejection, investigated the modulation of D6 expression in cells, and determined the effect of D6 on graft survival. Interestingly, D6 was highly expressed in CD45 -: cells and the corneal epithelium of accepted corneal allografts. From the mouse corneal allograft model, TGF-β was found to play a key role in D6 up-regulation, leading to reduced CCL2, CCL5, and CCL3. To modulate D6 chemokine binding, a D6MT was developed and showed effective chemokine trapping through SPR and FACS assays. By treating corneal allografts with D6MT, the allograft survival rate was improved, and (lymph) angiogenesis was reduced. Direct allosensitization and DC LN homing was drastically reduced in the mouse corneal allograft model. These findings suggest that TGF-β is a positive regulator of D6 expression, and it is a potential therapeutic target to enhance the survival of corneal allografts.

Grassi CM, Crnej A, Paschalis EI, Colby KA, Dohlman CH, Chodosh J. Idiopathic vitritis in the setting of Boston keratoprosthesis. Cornea 2015;34(2):165-70.Abstract

PURPOSE: The aim of this study was to revisit the clinical paradigm attributed to Boston keratoprosthesis recipients presenting with idiopathic vitreous inflammation. METHODS: A retrospective chart review was performed of keratoprosthesis recipients at Massachusetts Eye and Ear Infirmary, from January 2000 to August 2013, for demographic data, indication(s) for surgery, timing and presentation of vitreous inflammation, and best-corrected visual acuity at baseline, on presentation, and after resolution of vitritis. RESULTS: Twenty-three (23 eyes) of 346 patients developed idiopathic vitreous inflammation after keratoprosthesis implantation. Six of 23 patients presented with signs and symptoms similar to infectious endophthalmitis but were culture negative. The proportion of patients who fit the previous paradigm of sudden painless loss of vision without external signs of infection ("sterile vitritis") at their first presentation with vitritis was only 4 of 23. Vision decline was variable (median, 9 lines on Snellen chart; range, 0-24), as was time to recovery of best vision (median, 8.9 weeks; range, 0.9-36.7). Nine eyes had repeat bouts (43 episodes in 23 patients). Ten of 43 episodes did not recover to baseline vision. Seventeen of 23 eyes with idiopathic vitritis after keratoprosthesis later developed other complications. CONCLUSIONS: The current paradigm for idiopathic vitritis after keratoprosthesis implantation includes sudden painless loss of vision with full recovery of vision on treatment with periocular corticosteroids. However, idiopathic vitritis after keratoprosthesis can also mimic infectious endophthalmitis with pain and external signs of inflammation. Visual loss can be gradual. Vision may not recover to baseline despite treatment. Vitritis may be a part of a common pathway of chronic inflammation after keratoprosthesis.

Kheirkhah A, Dohlman TH, Amparo F, Arnoldner MA, Jamali A, Hamrah P, Dana R. Effects of corneal nerve density on the response to treatment in dry eye disease. Ophthalmology 2015;122(4):662-8.Abstract

PURPOSE: To evaluate whether levels of corneal subbasal nerve fiber length (SNFL) in dry eye disease (DED) could prognosticate the level of improvement in signs and symptoms after treatment. DESIGN: Phase IV, double-masked, randomized clinical trial. PARTICIPANTS: Sixty patients with meibomian gland dysfunction-associated DED and 27 age-matched controls. METHODS: Patients with DED were randomized to receive topical artificial tears, loteprednol etabonate 0.5%, or loteprednol etabonate 0.5%/tobramycin 0.3% twice daily for 4 weeks. At baseline, in vivo confocal microscopy of central cornea was performed in both eyes. Patients with DED were divided into 2 subgroups: those with low baseline SNFL and those with near-normal baseline SNFL for this purpose (the cutoff point: the mean SNFL in controls minus 2 standard deviations). Clinical signs and symptoms at baseline and after 4 weeks of treatment were compared between the subgroups with low and near-normal SNFL for all therapeutic groups. MAIN OUTCOME MEASURES: Symptom questionnaires, corneal fluorescein staining (CFS), conjunctival staining with lissamine green, tear break-up time, Schirmer's test, and SNFL. RESULTS: In patients with DED, baseline SNFL (17.06±5.78 mm/mm(2)) was significantly lower than in controls (23.68±3.42 mm/mm(2), P = 0.001). In the artificial tear and loteprednol groups, although no significant improvement in any sign or symptom was noted in patients with low baseline SNFL (<16.84 mm/mm(2)), subjects with near-normal baseline SNFL (≥16.84 mm/mm(2)) showed significant improvement in both symptoms and CFS score (all P < 0.05). In the loteprednol/tobramycin group, no significant change was evident for any sign or symptom in either subgroup of low or near-normal baseline SNFL. CONCLUSIONS: Significant improvements in CFS and patient symptomatology after DED treatment were evident only in the subgroup with near-normal corneal SNFL. Consideration of SNFL may assist in explaining the variability of patients' response to DED therapy.

Chauhan SK, Jurkunas U, Funaki T, Dastjerdi M, Dana R. Quantification of allospecific and nonspecific corneal endothelial cell damage after corneal transplantation. Eye (Lond) 2015;29(1):136-44.Abstract

PURPOSE: To investigate the effect of host immunity (allospecific) and surgical manipulation (non-allospecific) on corneal endothelial cells (CECs) in corneal transplantation. METHODS: Draining lymph nodes and grafted C57BL/6 corneas were harvested from syngeneic recipients, allograft acceptors, and allograft rejectors (BALB/c) 1, 3, and 8 weeks after transplantation. We analyzed CEC apoptosis using an ex vivo cornea-in-the-cup assay, and visualized cell-to-cell junctions using immunohistochemical staining (ZO-1). Automatic cell analysis using Confoscan software was used to measure CEC density as well as changes in CEC morphology by quantifying the coefficient of variation in cell size (polymegethism) and shape (pleomorphism). RESULTS: The cornea-in-the-cup assay showed that allogeneic acceptor T cells and to an even greater extent rejector T cells (but not syngeneic T cells) induced CEC apoptosis. CEC density after corneal transplantation was significantly reduced in allogeneic acceptors compared with syngeneic grafts (P<0.001), and CEC density was even further reduced in the allo-rejector group compared with the allo-acceptor group. Allogeneic grafts showed a greater increase in the coefficient of variation in cell size (polymegethism) when compared with syngeneic grafts 1 week after transplantation (P=P<0.001). However, pleomorphism was not significantly different between syngeneic and allo-acceptor grafts, indicating that polymegethism (but not pleomorphism or cell density) is a sensitive indicator of the effect of alloimmunity on CECs. CONCLUSIONS: Our data demonstrate that host alloimmunity rather than surgical manipulation alone is the major cause of CEC damage in corneal transplantation, and such morphologic changes of CECs can be detected before the clinically visible onset of allograft rejection.

Papakostas TD, Le H-G, Chodosh J, Jacobs DS. Prosthetic replacement of the ocular surface ecosystem as treatment for ocular surface disease in patients with a history of stevens-johnson syndrome/toxic epidermal necrolysis. Ophthalmology 2015;122(2):248-53.Abstract

PURPOSE: To report the visual outcomes of prosthetic replacement of the ocular surface ecosystem (PROSE) treatment in patients with ocular surface disease related to Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN). DESIGN: Retrospective cohort study. SUBJECTS: We included 86 patients (167 eyes) with history of SJS/TEN who underwent PROSE treatment from January 1, 2006, to January 1, 2011. METHODS: Etiology, previous interventions, change in visual acuity, change in visual function, and duration of follow-up are reported. Paired t test and Friedman test with Dunn's post hoc test for multiple comparisons were used for statistical analysis. MAIN OUTCOME MEASURES: Visual acuity at last follow-up and visual function based on the National Eye Institute 25-item Visual Functioning Questionnaire (NEI VFQ-25) at 6 months. RESULTS: We treated 35 males and 51 females with a history of SJS/TENS; median age was 36 years. The most common reported etiologies for SJS/TENS were antibiotics (n = 25), ibuprofen (n = 15), and lamotrigine (n = 11). The median visual acuity at the initial visit was 20/60 (range, 20/400-20/25; 0.48 logarithm of the minimum angle of resolution [logMAR]), and the visual acuity at completion of customization was 20/25 (range, 20/200-20/20; 0.096 logMAR; P < 0.001), with no decline in median acuity at the end of follow-up. Median duration of follow-up was 16 months. There was a significant improvement in the visual function of the patients based on the NEI VFQ-25 questionnaire (mean of 48 points at baseline vs. mean of 72 points at 6 months; P < 0.001). In addition, there was also an improvement in the self-reported general health of the patients (mean of 57 points at baseline vs. mean of 65 points at 6 months; P < 0.01). CONCLUSIONS: In a large cohort of patients with chronic ocular surface disease related to SJS/TEN, PROSE treatment offers sustained and significant large improvement in visual function and acuity.

Gipson IK, Spurr-Michaud S, Tisdale A, Menon BB. Comparison of the transmembrane mucins MUC1 and MUC16 in epithelial barrier function. PLoS One 2014;9(6):e100393.Abstract
Membrane-anchored mucins are present in the apical surface glycocalyx of mucosal epithelial cells, each mucosal epithelium having at least two of the mucins. The mucins have been ascribed barrier functions, but direct comparisons of their functions within the same epithelium have not been done. In an epithelial cell line that expresses the membrane-anchored mucins, MUC1 and MUC16, the mucins were independently and stably knocked down using shRNA. Barrier functions tested included dye penetrance, bacterial adherence and invasion, transepithelial resistance, tight junction formation, and apical surface size. Knockdown of MUC16 decreased all barrier functions tested, causing increased dye penetrance and bacterial invasion, decreased transepithelial resistance, surprisingly, disruption of tight junctions, and greater apical surface cell area. Knockdown of MUC1 did not decrease barrier function, in fact, barrier to dye penetrance and bacterial invasion increased significantly. These data suggest that barrier functions of membrane-anchored mucins vary in the context of other membrane mucins, and MUC16 provides a major barrier when present.
Hong J, Liu Z, Hua J, Wei A, Xue F, Yang Y, Sun X, Xu J. Evaluation of age-related changes in noninvasive tear breakup time. Optom Vis Sci 2014;91(2):150-5.Abstract
PURPOSE: To establish normal noninvasive tear film breakup time (NI-BUT) values in the Chinese population and investigate age-related changes in NI-BUT using a newly developed Keratograph. METHODS: Forty normal volunteers with a mean age of 32.8 ± 16.7 years were recruited for this study. Clinical and demographic data, including age, gender, fluorescein tear film breakup time (FBUT), and Schirmer I test values were collected from the subjects. Noninvasive tear film breakup time was measured using a new method based on a corneal topographer equipped with a modified scan software. The correlations between the NI-BUT, age, and gender were determined. RESULTS: In total, a significant difference between the NI-BUT and the FBUT was found (4.9 ± 2.4 seconds vs. 9.0 ± 3.0 seconds; p < 0.001). No statistically significant difference in the NI-BUT was observed between the male and female subjects (5.5 ± 2.0 seconds vs. 4.5 ± 2.5 seconds; p = 0.137). In addition, no significant correlation was detected between the NI-BUT and age (0.143, p = 0.321). CONCLUSIONS: The NI-BUT values found in this study are much lower than those of previous reports. Our results show no significant differences in tear film stability with age. The tear physiology of the Chinese population may not be the same as in Western populations.
Karamichos D, Funderburgh ML, Hutcheon AEK, Zieske JD, Du Y, Wu J, Funderburgh JL. A role for topographic cues in the organization of collagenous matrix by corneal fibroblasts and stem cells. PLoS One 2014;9(1):e86260.Abstract
Human corneal fibroblasts (HCF) and corneal stromal stem cells (CSSC) each secrete and organize a thick stroma-like extracellular matrix in response to different substrata, but neither cell type organizes matrix on tissue-culture polystyrene. This study compared cell differentiation and extracellular matrix secreted by these two cell types when they were cultured on identical substrata, polycarbonate Transwell filters. After 4 weeks in culture, both cell types upregulated expression of genes marking differentiated keratocytes (KERA, CHST6, AQP1, B3GNT7). Absolute expression levels of these genes and secretion of keratan sulfate proteoglycans were significantly greater in CSSC than HCF. Both cultures produced extensive extracellular matrix of aligned collagen fibrils types I and V, exhibiting cornea-like lamellar structure. Unlike HCF, CSSC produced little matrix in the presence of serum. Construct thickness and collagen organization was enhanced by TGF-ß3. Scanning electron microscopic examination of the polycarbonate membrane revealed shallow parallel grooves with spacing of 200-300 nm, similar to the topography of aligned nanofiber substratum which we previously showed to induce matrix organization by CSSC. These results demonstrate that both corneal fibroblasts and stromal stem cells respond to a specific pattern of topographical cues by secreting highly organized extracellular matrix typical of corneal stroma. The data also suggest that the potential for matrix secretion and organization may not be directly related to the expression of molecular markers used to identify differentiated keratocytes.
Gilbert AL, Jakobiec FA, Chodosh J, Eliott D. A comparison of retrokeratoprosthetic membrane and conjunctival inflammatory responses to silicone oil. J Ophthalmic Inflamm Infect 2014;4:15.Abstract
Silicone oil continues to be an important aid in retinal detachment surgery. We report a case in which disparate responses to silicone oil were noted in the conjunctiva and intraocularly. Intraocularly, the oil permeated a fibrous membrane that formed behind a keratoprosthesis, the first example of this phenomenon. We detail the histological response to the oil at this site as well as a distinctly different reaction present to oil in the conjunctiva of the same eye. The divergence of histological responses provides a demonstration of the eye's apparent retained capacity to protect against intraocular inflammation, despite multiple previous surgeries.
Gonzalez-Saldivar G, Lee GN, Chodosh J, Freitag SK, Stacy RC. Dacryops in the setting of a Boston type II keratoprosthesis. Ophthalmic Plast Reconstr Surg 2014;30(3):e73-5.Abstract
Dacryops of the lacrimal tissue can develop under diverse circumstances. Recent evidence suggests that scarring or obstruction of the lacrimal ducts may lead to their dilatation and formation of a cystic structure. Patients who undergo repeated orbital surgery may therefore be at greater risk of dacryops formation. In this report, a patient who underwent multiple corneal and glaucoma procedures including Boston type II keratoprosthesis, after acid burns to both eyes, is described. Over time, a fluid-filled collection developed in the lower orbit. On surgical exploration and incision, fluid was drained from a cystic lesion which abutted the lacrimal gland and spanned the upper and lower orbits. The lesion was removed and was proven by histopathology and immunohistochemistry to be dacryops. This is the first known case of dacryops associated with Boston type II keratoprosthesis.

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