An ocular model of adenovirus type 5 infection in the NZ rabbit.
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Ocular adenoviral infections occur worldwide, and currently, there is no ocular animal model for evaluating new antivirals or studying pathogenesis. With a paired-eye design, an ocular model was developed in 32 New Zealand rabbits following topical and intrastromal inoculation with a clinical isolate of adenovirus type 5 (Ad5 McEwen). Clinical signs of infection--conjunctivitis, corneal edema, subepithelial infiltrates, and iritis--and seroconversion were evaluated. Replicating virus on the ocular surface was determined by serial ocular titers. Reproducible acute ocular infection was demonstrated in 32 of 32 infected eyes (100%), with mean viral replication lasting for 8.3 days. Peak ocular viral titers (10(3) plaque forming units/ml) were achieved on day three after inoculation and represented a 2 log increase (100 times) over day one. Ocular viral replication was associated with acute conjunctivitis (24/34 eyes, 75%), and delayed-onset presumed immune-mediated clinical disease was associated with: blepharoconjunctivitis (21/32 eyes, 66%), iritis (29/32 eyes, 91%), corneal edema (32/32 eyes, 100%), and subepithelial corneal infiltrates (30/32 eyes, 94%). Seroconversion was demonstrated in 26 of 31 rabbits (84%). The study concludes that a potentially useful animal model of adenoviral ocular infection can be attained. (+info)
Changes in the refractive index of the stroma and its extrafibrillar matrix when the cornea swells.
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The transparency of the corneal stroma is critically dependent on the hydration of the tissue; if the cornea swells, light scattering increases. Although this scattering has been ascribed to the disruption caused to the arrangement of the collagen fibrils, theory predicts that light scattering could increase if there is an increased mismatch in the refractive indices of the collagen fibrils and the material between them. The purpose of this article is to use Gladstone and Dale's law of mixtures to calculate volume fractions for a number of different constituents in the stroma, and use these to show how the refractive indices of the stroma and its constituent extrafibrillar material would be expected to change as more solvent enters the tissue. Our calculations predict that solvent entering the extrafibrillar space causes a reduction in its refractive index, and hence a reduction in the overall refractive index of the bovine stroma according to the equation n'(s) = 1.335 + 0.04/(0.22 + 0.24 H'), where n'(s) is the refractive index and H' is the hydration of the swollen stroma. This expression is in reasonable agreement with our experimental measurements of refractive index versus hydration in bovine corneas. When the hydration of the stroma increases from H = 3.2 to H = 8.0, we predict that the ratio of the refractive index of the collagen fibrils to that of the material between them increases from 1.041 to 1.052. This change would be expected to make only a small contribution to the large increase in light scattering observed when the cornea swells to H = 8. (+info)
Topographical thickness of the epithelium and total cornea after overnight wear of reverse-geometry rigid contact lenses for myopia reduction.
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PURPOSE: To investigate topographical thickness changes of the epithelium and total cornea measured with optical coherence tomography (OCT) after overnight wear of rigid gas-permeable lenses. METHODS: Reverse geometry design CRT (Dk=100) rigid (test) lenses (Paragon Vision Sciences, Mesa, AZ) were randomly fitted on one eye of each of 20 neophyte subjects (mean age, 24.6 +/- 2.7 years) and the other eye was fitted with an alignment tricurve rigid lens of the same material (control). Epithelial and total corneal thickness was measured at intervals of 10 degrees across a 10-mm zone of the horizontal meridian of the cornea, before and after overnight wear. Refractive error was measured with an autorefractor. These measurements were repeated 20 and 60 minutes and 3, 6, and 12 hours after lens removal. RESULTS: After one night of lens wear, myopia decreased in the test eye by 1.18 +/- 0.81 D, which was significantly different from baseline (P<0.001). No significant change was found in the control eye. Twelve hours after removal, two thirds of the myopic reduction was still present. Different topographical swelling patterns were induced by the two lens designs, with greatest swelling occurring in the center with the control lens and in the midperiphery with the test lenses (polynomial regression: P<0.005). Significantly greater central corneal swelling was found with the control lens than the test lens (6.9% +/- 3.1% vs. 4.9% +/- 2.0%, respectively, P=0.006). The effect on epithelial thickness differed between lenses and depended on both position and time (F(48,912)=2.3; P=0.000). Immediately after removal of the test lens, the central epithelium was 5.1% +/- 4.5% thinner than baseline, and all other locations (P<0.005 post hoc tests) and the epithelium in the midperiphery showed significant thickening (1.9% on the temporal side and 2.4% on the nasal side, both P<0.006 compared with the baseline). There were no significant changes in epithelial thickness with the control lens during the study period (post hoc tests: P>0.05). CONCLUSIONS: The optical coherence tomograph is a sensitive instrument that can detect small changes in epithelial and corneal thickness across the entire cornea. Topographical thickness changes of the epithelium and total cornea induced by one night of reverse-geometry lens wear appear to be associated with the decrease of myopia. (+info)
Corneal endothelial safety of intracameral preservative-free 1% xylocaine.
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PURPOSE: To evaluate the effect of intracameral preservative-free 1% xylocaine on the corneal endothelium as an adjuvant to topical anaesthesia during phacoemulsification and Acrysof foldable IOL implantation. MATERIAL & METHODS: This is a prospective, controlled, randomised, double-masked study. 106 patients with soft to moderately dense (Grade 1-3) senile cataract and corneal endothelial cell density of >1500/mm2 were randomised to the xylocaine group (n=53) and control group(n=53). Central endothelial specular microscopy and ultrasound corneal pachymetry were performed preoperatively. On the first postoperative day the eyes were evaluated for corneal oedema and Descemet's folds. Ultrasound corneal pachymetry was performed at 1, 3 and 12 months. Specular microscopy was performed at 3 and 12 months. Cell loss was expressed as a percentage of preoperative cell density. Six patients could not complete one year follow-up. Chi-square and paired t test (2 tail) statistical tests were applied for analysis. RESULTS: Four (7.54%) patients in the xylocaine group and 5 (9.43%) in the control group had a few Descemet's folds associated with mild central stromal oedema. Corneal thickness increased from 549.3micro +/- 37.2micro to 555.5micro +/- 36.5micro in the xylocaine group and from 553.1micro +/- 36.2micro to 559.3micro +/- 40.5micro in the control group at the one-month postoperative visit. Thickness returned to the preoperative level in xylocaine group 549.6micro +/- 34.5micro and control group 554.7micro +/- 41.1micro at three months. (P=0.484) The percentage of cell loss was 4.47 +/- 2.53% in the xylocaine group and 4.49 +/- 3.09% in the control group at one year. (P=0.97) CONCLUSION: Intracameral preservative-free 1% xylocaine does not appear to affect corneal endothelium adversely during phacoemulsification. (+info)
Objective measurements of corneal light-backscatter during corneal swelling, by optical coherence tomography.
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PURPOSE: To demonstrate that corneal light-backscatter can be measured objectively during corneal swelling by optical coherence tomography (OCT). METHODS: One eye (randomly selected) of 20 non-contact-lens wearers (10 men and 10 women; mean age, 35.6 +/- 9.6 years) was patched during 3 hours of soft contact lens (SCL) wear. The contralateral eye acted as the control. Central corneal images were captured before and after SCL wear at 20-minute intervals over 100 minutes using optical coherence tomography (OCT) to obtain corneal thickness and light-backscatter profiles. OCT backscattered light of the epithelial layer (decided by the thickness measurements) and 10 equally divided layers of the remaining cornea were analyzed with a custom software program. Two baseline measurements were taken at different visits before lens wear to test the repeatability of light-backscatter measurements. RESULTS: From two baseline measurements, repeated measurements showed good repeatability of normalized backscatter results. Immediately after contact lens removal, total central corneal thickness increased significantly by 13.8% +/- 2.3% (mean +/- SD) compared with baseline (P = 0.0001, paired t-test) and then decreased during the deswelling course. Corneal backscattered light changed significantly (repeated-measures ANOVA [Re-ANOVA]: F((50, 950)) = 2.22, P = 0.0001) after lens wear, and a significant increase in backscatter was found in the epithelial layer (36.4%) and the most posterior corneal layer (35.6%) immediately after lens removal (post hoc test, P = 0.005). There was a strong correlation (r = 0.9375, P < 0.05) between the change in backscatter and corneal swelling during the deswelling period. The backscatter recovery rate was approximately the same for both epithelial and posterior layers after lens removal. CONCLUSIONS: Light-backscattering analysis with OCT seems to be a promising and repeatable method of objectively measuring corneal backscatter. This study has demonstrated that corneal backscattered light increased in the anterior and posterior layers of the cornea during corneal swelling induced by contact lens wear and eye closure. (+info)
Animal compound-free medium and poloxamer for human corneal organ culture and deswelling.
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PURPOSE: Eliminating fetal calf serum (FCS) from corneal organ culture (OC) media has long been a challenge. This study was an assessment of a new animal compound-free (ACF) medium for corneal storage and of its combination with poloxamer for end-of-storage corneal deswelling. METHODS: A randomized controlled study with masked assessment compared the ACF medium to standard commercialized media containing 2% FCS and their combination with dextran for deswelling. Paired human corneas were randomly allocated at procurement, one to the ACF medium and the other to the FCS media, and then assessed at day (D)2 and D30 of OC storage and after 48 hours of deswelling. Comparison criteria were endothelial cell density (ECD) and morphometry by a corneal analyser, quality of endothelial visualization (using saline), EC mortality (trypan blue), corneal thickness, corneal transparency, and folding. Fifty-six corneas (28 pairs) with ECD of 2000 cells/mm(2) or more were enrolled. Data were compared using paired tests with P < 0.01 deemed significant. RESULTS: Parameters were similar at baseline (D2) between groups. Daily EC loss during the 30 days of storage was reduced with the ACF compared with standard (-0.31% +/- 0.30% vs. -0.88% +/- 0.38%, P < 0.001). With poloxamer 188 (Lutrol F68; BASF, Ludwigshafen, Germany), EC loss was substantially reduced (-1.43% +/- 3.60 vs. -15.41% +/- 10.13%, P < 0.001) and morphometry better preserved, despite thickness reduction, transparency improvement and folding reduction comparable to dextran. After 30 days of storage in ACF medium and deswelling in poloxamer 188, ECD was 30% higher (2466 +/- 447 cells/mm(2) vs. 1729 +/- 281 cells/mm(2), P < 0.001). ACF medium alone and combined with poloxamer 188 considerably facilitated EC visualization at D30 and after deswelling. CONCLUSIONS: The ACF medium combined with poloxamer 188 for deswelling showed superiority over standard FCS medium in its ability to preserve EC viability and facilitate endothelial visualization. This innovative use of poloxamer for deswelling appears far less toxic than does dextran. (+info)
Increased expression of inflammatory cytokines and matrix metalloproteinases in pseudophakic corneal edema.
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PURPOSE: To evaluate the expression of inflammatory cytokines and matrix metalloproteinases in the corneal epithelium in pseudophakic corneal edema (PCE). METHODS: Tissue sections were prepared from formalin-fixed, paraffin-embedded blocks of corneal buttons removed from 20 patients with PCE during penetrating keratoplasty (PKP) and from 11 age-matched control eyes enucleated because of uveal melanoma. Expression of interleukin (IL)-1beta, -6, and -8; vascular endothelial growth factor (VEGF); and matrix metalloproteinase (MMP)-1, -3, and -9 proteins in the corneal epithelium was evaluated by immunohistochemistry. Digital image analysis was performed to quantify the expression of the various cytokines and MMPs. A mean intensity stain index (ISI), based on the staining density and the area stained, was calculated from digital images captured from sequential areas of the corneal epithelium. RESULTS: The expression of most of the inflammatory cytokines and MMPs was significantly higher in the corneal epithelium of PCE corneal buttons than in the control specimens. MMP-9 had the highest expression when compared with the control (ISI = 55.08 +/- 23.71 in PCE compared with 0.169 +/- 0.156 in the control; P < 0.0001). Significantly higher ISIs were also recorded for MMP-1 (16.14 +/- 8.49 vs. 1.13 +/- 1.79; P < 0.0001), IL-1beta (62.62 +/- 27.23.97 vs. 1.61 +/- 1.27; P < 0.0001), IL-8 (37.91 +/- 21.18 vs. 4.24 +/- 3.60; P < 0.0001), and VEGF (81.67 +/- 26.22 vs. 19.40 +/- 16.85; P = 0.0001). The expression of MMP-3, IL-6, and TNF-alpha in PCE was not different from control expression. Significant positive correlations were found between the expression of IL-1beta and MMP-9 (r(2) = 0.37; P = 0.015), between VEGF and IL-8 (r(2) = 0.22; P = 0.042), and a significant correlation was found between the expression of MMP-3 and TNF-alpha (r(2) = 0.5197; P = 0.0007). The expression of TNF-alpha correlated significantly with the patient's age (r(2) = 0.28; P = 0.0195). CONCLUSIONS: The corneal epithelium in PCE expresses high levels of cytokines and matrix-degrading enzymes, which are associated with inflammation, wound healing, angiogenesis, and tissue degradation. The expression of these mediators may partially explain the pathologic features associated with this disease, such as bulla formation, recurrent epithelial desquamation, and corneal neovascularization. (+info)
Overnight orthokeratology lens wear can inhibit the central stromal edema response.
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PURPOSE: To investigate the overnight corneal edema response during overnight orthokeratology (OK). METHODS: Eighteen young adult myopic subjects wore reverse-geometry lenses in Boston XO material (nominal Dk/t 46 x 10(-9) cm.mL O2/s.mL.mmHg) on an overnight wearing schedule for 1 month. Another 10 subjects wore conventional rigid gas-permeable (GP) lenses of similar Dk/t in one eye only, on an identical schedule. Corneal stromal thicknesses in the center, midperiphery, and periphery were measured by optical pachometry in the morning after lens removal, after 1, 4, 10, and 30 nights of wear. Changes from baseline for OK, GP and no-lens eyes were compared by repeated-measures ANOVA and protected post hoc t-tests. RESULTS: The central stroma swelled significantly less in OK than in GP eyes (P < 0.001, ANOVA), and less than with no lens wear (P < 0.001, ANOVA) throughout the study. Overnight edema levels consistent with Dk/t were found on day 1 in the midperiphery (3.5 mm from apex) and periphery (5.0 mm) with both OK and GP lenses. The overnight edema response decreased significantly through the study with both lens types. Recovery to baseline stromal thickness during the day was demonstrated for GP eyes and for OK eyes in the central and peripheral cornea. CONCLUSIONS: Overnight wear of reverse-geometry OK lenses inhibited the central stromal edema response. Overnight edema levels consistent with Dk/t were found in the corneal midperiphery and periphery. Adaptation of the edema response occurred with continuing overnight lens wear. The results suggest that central pressure exerted by the flat-fitting base curve of the OK lens acts locally as a "clamp" to inhibit overnight central corneal swelling. (+info)