Jay M. Stewart

Prevalence, clinical features, and causes of vision loss among patients with ocular toxocariasis.

Background: To describe the prevalence, clinical features, and causes of vision loss among patients with ocular toxocariasis seen at a uveitis referral center. Methods: A review was completed of the charts of patients with ocular toxocariasis who were examined between 1977 and 1996 at the Francis I. Proctor Foundation of the University of California at San Francisco. The prevalence of ocular toxocariasis among all uveitis patients seen at the center was determined. Demographic features, symptoms, and signs in all patients were evaluated. Results: Ocular toxocariasis occurred in 22 (1.0%) of 2,185 uveitis patients. The mean patient age was 16.5 years. Inflammation was usually unilateral (90.9%). Toxocara uveitis presented as a granuloma in the peripheral retina in 50% of cases, as a granuloma in the macula in 25% of cases, and as a moderate to severe vitreous inflammation mimicking endophthalmitis in 25% cases. The primary causes of vision loss were vitritis (52.6%), cystoid macular edema (47.4%), and traction retinal detachment (36.8%). Conclusions: Ocular toxocariasis is an uncommon cause of uveitis that mainly affects younger patients. Inflammation is typically unilateral and presents as either a granuloma in the peripheral or posterior retina or a moderate to severe vitreous inflammation mimicking endophthalmitis.

Structural Factors That Mediate Scleral Stiffness

PURPOSE The intent of this study was to correlate measures of structurally relevant biochemical constituents with tensile mechanical behavior in porcine and human posterior sclera. METHODS Posterior scleral strips 6 x 25 mm were harvested from 13 young porcine and 10 aged human eyes and stored frozen at -20 degrees C. Mechanical hysteresis from 10 consecutive load cycles to a peak stress of 1.0 MPa was recorded via a custom-built soft tissue tester. In a parallel study, tissue adjacent to the mechanical test specimens was apportioned for each of five assays measuring: total collagen content, nonenzymatic cross-link density, elastin content, glycosaminoglycan content, and water content. RESULTS The average porcine scleral modulus at 1% strain was 75% less than that measured for human tissue (0.65 +/- 0.53 MPa versus 2.60 +/- 2.13 MPa, respectively; P < 0.05). However, the average strain energy absorbed per loading cycle was similar (6.09 +/- 2.54 kJ/m(3) vs. 5.96 +/- 2.69 kJ/m(3) for porcine and human sclera respectively; P > 0.05). Aged human sclera had relatively high fluorescence due to nonenzymatic cross-link density (2200 +/- 368 vs. 842 +/- 342; P < 0.05) and low hydroxyproline content (0.79 +/- 0.17 microL/mL/g versus 1.21 +/- 0.09 microL/mL/g; P < 0.05) while other measured biochemical factors were statistically similar (P > 0.05). CONCLUSIONS Aged human tissue had superior mechanical stiffness despite reduced collagen content, partially because of the accumulation of nonenzymatic cross-links. Differences in collagen content and cross-link density either had no effect or offsetting effects on the ability of the tissues to absorb strain energy.

Predictors of an unsatisfactory response to pentavalent antimony in the treatment of American visceral leishmaniasis

Although treatment of visceral leishmaniasis with pentavalent antimony is usually successful, some patients require second-line drug therapy, most commonly with amphotericin B. To identify the clinical characteristics that predict an inadequate response to pentavalent antimony, a case-control study was undertaken in Teresina, Piaui, Brazil. Over a two-year period, there were 19 cases of VL in which the staff physicians of a hospital prescribed second-line therapy with amphotericin B after determining that treatment with pentavalent antimony had failed. The control group consisted of 97 patients that were successfully treated with pentavalent antimony. A chart review using univariate and multivariate analysis was performed. The cure rate was 90% with amphotericin B. The odds ratio for the prescription of amphotericin B was 10.2 for children less than one year old, compared with individuals aged over 10 years. Patients who presented coinfection had an OR of 7.1 while those on antibiotics had an OR of 2.8. These data support either undertaking a longer course of therapy with pentavalent antimony for children or using amphotericin B as a first-line agent for children and individuals with coinfections. It also suggests that chemoprophylaxis directed toward bacterial coinfection in small children with VL may be indicated.

Ocular surface fluid contamination of sutureless 25-gauge vitrectomy incisions.

Purpose: To determine whether 25-gauge transconjunctival sutureless vitrectomy incisions are more likely to allow the inflow of ocular surface fluid than sutured vitrectomy incisions. Methods: Four groups of cadaver eyes underwent three-port vitrectomy in a laboratory setup. Groups A and B had 25-gauge vitrectomy, with and without conjunctival displacement, respectively, and were left unsutured. Group C had 25-gauge vitrectomy with suturing of the sclerotomies. Group D had 20-gauge sutured vitrectomy. In all groups, India ink was applied to the ocular surface after the procedure, and the intraocular pressure (IOP) was varied to simulate postoperative IOP changes. Histology of the incisions was performed. Results: Ink particles were identified in the wound in over two-thirds of eyes that underwent 25-gauge sutureless vitrectomy. Conjunctival displacement had no effect on ink ingress. Sutured 25- and 20-gauge incisions did not demonstrate ink particles in the wound. Conclusions: Twenty-five-gauge transconjunctival sutureless vitrectomy incisions, with or without conjunctival displacement, allowed the entry of ocular surface fluid into the eye in this laboratory model. Based on the limited number of eyes examined in this study, sutureless vitrectomy techniques may carry an increased risk of bacterial contamination that could predispose to endophthalmitis. Suturing may protect against ocular surface fluid ingress.

Collagen cross-links reduce corneal permeability.

PURPOSE To investigate the relationship between corneal permeability and nonenzymatic cross-link density. METHODS Corneas were dissected from 90 cadaveric porcine eyes. Samples were incubated for 24 hours with control solution or methylglyoxal at concentrations of 0.01%, 0.10%, and 1.00%. Nonenzymatic cross-link density in treated and control groups was quantified by papain digest and fluorescence spectrophotometry. Control and treated corneas were mounted in a customized Ussing-type chamber connected to vertical tubing, and specific hydraulic conductivity was determined according to the descent of a column of degassed saline at room temperature. Permeability to diffusion of fluorescein in a static chamber was determined for a similar set of corneal samples. RESULTS Methylglyoxal treatment effectively increased nonenzymatic cross-link content, as indicated by the average fluorescence for each group. Specific hydraulic conductivity (m(2)) was reduced with increasing cross-link density. Similarly, the permeability coefficient for the fluorescein solute consistently decreased with increasing methylglyoxal concentration, indicating diffusion impedance resulting from the treatment. CONCLUSIONS Nonenzymatic cross-link density in the cornea can be significantly increased by treatment with methylglyoxal. Porcine cornea showed a nonlinear reduction in solute permeability and specific hydraulic conductivity with increasing cross-link density. This model suggests that age-related nonenzymatic cross-link accumulation can have a substantial impact on corneal permeability.

Effects of corneal cross-linking on contrast sensitivity, visual acuity, and corneal topography in patients with keratoconus.

Purpose: To assess the effects of corneal collagen cross-linking (CXL) on contrast sensitivity (CS), visual acuity, and corneal topography investigating possible predictors of efficacy. Methods: Sixty-eight eyes of 34 patients with progressive keratoconus were enrolled in this prospective study. CXL was performed in one eye and the other eye was left untreated as a control. CS, best spectacle–corrected visual acuity (BSCVA), simulated keratometry in the steepest meridian (SimK-s), mean power in the central 3-mm zone (C-MP), mean power in the paracentral 3- to 5-mm zone (P-MP), maximum keratometric power in the central zone (C-Kmax), and maximum keratometric power in the paracentral zone (P-Kmax) were evaluated at baseline, 40 days, 3 months, 6 months, 1 year, and after 2 years of follow-up. Results: Treated eyes showed an improvement (P < 0.001) of +0.16 logCS and −0.16 logarithm of the minimum angle of resolution (logMAR) and a reduction in SimK-s of −0.61 diopter (D), C-Kmax −1.11 D, P-Kmax −0.99 D, C-MP −0.39 D, and P-MP −0.30 D. Of the treated eyes, 43.3% had a decrease in C-Kmax greater than 1 D, 50% by 0 to 0.99 D, and 6.7% had an increase of up to +0.89 D. Treated eyes with keratometric apex in the central 3-mm zone (CKA) improved BSCVA −0.19 logMAR and CS +0.19 logCS; whereas in treated eyes with paracentral keratometric apex (PKA), the improvement was −0.13 logMAR and +0.16 logCS. Conclusions: CXL with riboflavin and UV-A improved CS and inhibited the progression of keratoconus. As a predictor of treatment efficacy, eyes with CKA showed greater improvement in BSCVA after CXL when compared with eyes with PKA.

Retinal Findings in Patients with Alport Syndrome: Expanding the Clinical Spectrum

Aims: To describe previously unreported retinal findings in patients with Alport Syndrome (AS), as well as review the range of ophthalmic manifestations. Methods: Retrospective review of clinical records of patients with AS. Results: Nine patients with AS were identified, of whom three had no eye findings, four showed classic features of AS, and two had new findings, bull’s eye and vitelliform maculopathy. The genetic mutation responsible for the disease in the patient with vitelliform subretinal deposits was identified. Conclusions: Patients with AS can present with a variety of ophthalmic manifestations. Bull’s eye maculopathy and vitelliform deposits can be features of AS. The mechanism of these new macular findings remains unknown. Possible pathophysiological overlap with other maculopathies including age-related macular degeneration is discussed.

Infection after blepharoplasty with and without carbon dioxide laser resurfacing

PURPOSE To determine the rate of infection in patients who underwent blepharoplasty with and without carbon dioxide laser resurfacing. DESIGN A retrospective, nonrandomized, consecutive case series. PARTICIPANTS Eighteen hundred sixty-one patients who underwent upper or lower blepharoplasty, with or without carbon dioxide laser resurfacing. METHODS Charts of patients who underwent blepharoplasty, with or without laser resurfacing, were analyzed for the presence of postoperative infection, method of treatment, and possible sequelae. MAIN OUTCOME MEASURES The rate of infection (%) was determined for each group of patients. RESULTS Infection occurred in 0.2% of patients who underwent blepharoplasty without laser resurfacing and 0.4% of patients who had adjunctive laser resurfacing. No permanent functional or cosmetic sequelae resulted from the episodes of infection. CONCLUSIONS Infection after blepharoplasty without laser resurfacing is uncommon, indicating that topical antibiotic ointment prophylaxis is a sufficient postoperative regimen. The use of adjunctive laser resurfacing may increase the infection rate slightly.

Pathophysiology of diabetic macular edema.

Visual impairment associated with diabetes mellitus (DM) and diabetic eye disease may result from DME (DME), macular ischemia, vitreous hemorrhage, or diabetic tractional retinal detachment. Of all these causes, DME is the most common cause of vision loss in this patient population. Data from the Wisconsin Epidemiologic Study of Diabetic Retinopathy suggest that the 14-year incidence of DME is 26%. DME is clinically seen as thickening of the retina. The Early Treatment Diabetic Retinopathy Study has further classified it to assist physicians in decision-making regarding its treatment. On angiography, it is seen as leakage in the macula with dye pooling in areas of longstanding macular edema. The reasons for visual loss in DME are multifactorial and include light scattering, impaired cell-to-cell interaction and disturbances of normal ionic balances in the retina. The study of pathophysiology looks at the detailed malfunctioning that arises from or-alternately-causes disease. This article will attempt to explain the still elusive pathophysiology of DME.

Exogenous collagen cross-linking reduces scleral permeability: modeling the effects of age-related cross-link accumulation.

PURPOSE To investigate the relationship between scleral permeability and nonenzymatic cross-link density. METHODS Scleral discs 18 mm in diameter were dissected from the medial and lateral equatorial regions of 60 cadaveric porcine eyes. Samples were incubated for 24 hours with control solution or methylglyoxal at concentrations of 0.001%, 0.01%, 0.10%, and 1.00%. Nonenzymatic cross-link density in treated and control groups was quantified with the use of papain digest and fluorescence spectrophotometry. Treated scleral discs were mounted in a customized Ussing-type chamber connected to vertical tubing, and specific hydraulic conductivity was determined according to the descent of a column of degassed saline at room temperature. Permeability to diffusion of fluorescein in a static chamber was determined for another set of treated scleral samples. RESULTS Methylglyoxal treatment effectively increased nonenzymatic cross-link content, as indicated by the average fluorescence for each group. Specific hydraulic conductivity (m(2)) was reduced with increasing cross-link density. Similarly, the permeability coefficient for the fluorescein solute consistently decreased with increasing methylglyoxal concentration, indicating diffusion impedance from the treatment. CONCLUSIONS Nonenzymatic cross-link density can be significantly increased by treatment with methylglyoxal. Porcine sclera showed a nonlinear reduction in solute permeability and specific hydraulic conductivity with increasing cross-link density. This model indicates that age-related nonenzymatic cross-link accumulation can have a substantial impact on scleral permeability.