Augusto Paranhos

Shifting trends in in vitro antibiotic susceptibilities for common ocular isolates during a period of 15 years.

PURPOSE To assess the in vitro susceptibility of the most common ocular bacterial isolates to several antibiotics and verify changing trends in the antibiotic susceptibility in a 15-year period. DESIGN Experimental study. METHODS All cultures positive for Staphylococcus aureus, coagulase-negative Staphylococcus (CNS), Streptococcus sp, and Pseudomonas sp in conjunctival (n = 4,585) and corneal (n = 3,779) samples from patients seen at the Federal University of São Paulo from 1985 to 2000 were evaluated. Cultures were performed in liquid and solid media, and susceptibility tests were done to amikacin, gentamicin, neomycin, tobramycin, ciprofloxacin, norfloxacin, ofloxacin, cephalothin, and chloramphenicol. RESULTS Amikacin and neomycin showed an improvement of their sensitivity during the study period (88%-95% and 50%-85%, respectively) for corneal and conjunctival samples. Gentamicin and tobramycin revealed a decrease of sensitivity in time, from 95% to less than 80% in corneal and conjunctival samples. Ciprofloxacin, norfloxacin, and ofloxacin had good sensitivity to all evaluated bacteria, better in conjunctiva (95%) than in cornea (90%). Sensitivity of S. aureus to cephalothin decreased during the study but was still 98% for CNS. Chloramphenicol had good sensitivity to S. aureus (85% in corneal and 92%in conjunctival samples), CNS (87% and 88.5%), and Streptococcus sp (95% and 96%). CONCLUSIONS Gentamicin, tobramycin, and cephalothin decreased their in vitro susceptibility to all tested pathogens. The fluoroquinolones remained a good choice in the treatment of ocular infections, with high suscep-tibility to all pathogens tested. Chloramphenicol also revealed an increase in its susceptibility to all bacteria evaluated.

Posture-induced Intraocular Pressure Changes: Considerations Regarding Body Position in Glaucoma Patients

Although glaucoma is a multifactorial disease, elevated intraocular pressure (IOP) remains the most important known risk factor. Different systemic and local factors are thought to influence an individuals IOP. There can be a clinically significant rise in IOP when going from upright to horizontal or inverted body positions. Although there is a significant interindividual variability, the magnitude of the IOP change is greater in glaucomatous eyes. As patients usually spend a significant portion of their lives in the horizontal position, mainly during sleep, this is highly relevant. In this review we discuss the relationship between postural changes and IOP fluctuation, including changes in both body and head position. The possible mechanisms involved and the main implications for glaucomatous eyes are discussed. Finally, considerations with regard to sleep position in glaucoma patients are made based on evidence in the literature.

Comparison of Different Spectral Domain OCT Scanning Protocols for Diagnosing Preperimetric Glaucoma

PURPOSE To compare the ability of spectral-domain optical coherence tomography (SDOCT) retinal nerve fiber layer (RNFL), optic nerve head (ONH), and macular measurements to detect preperimetric glaucomatous damage. METHODS The study included 142 eyes from 91 patients suspected of having the disease based on the appearance of the optic disc. All eyes had normal visual fields before the imaging session. Forty-eight eyes with progressive glaucomatous damage were included in the preperimetric glaucoma group. Ninety-four eyes without any evidence of progressive glaucomatous damage and followed untreated for 12.8 ± 3.6 years were used as controls. Areas under the receiver operating characteristic curves (AUC) were calculated to summarize diagnostic accuracies of the parameters. RESULTS The three RNFL parameters with the largest AUCs were average RNFL thickness (0.89 ± 0.03), inferior hemisphere average thickness (0.87 ± 0.03), and inferior quadrant average thickness (0.85 ± 0.03). The three ONH parameters with the largest AUCs were vertical cup-to-disc ratio (0.74 ± 0.04), rim area (0.72 ± 0.05), and rim volume (0.72 ± 0.05). The three macular parameters with the largest AUCs were GCC average thickness (0.79 ± 0.04), GCC inferior thickness (0.79 ± 0.05), and GCC superior thickness (0.76 ± 0.05). Average RNFL thickness performed better than vertical cup-to-disc ratio (0.89 vs. 0.74; P = 0.007) and GCC average thickness (0.89 vs. 0.79; P = 0.015). CONCLUSIONS SDOCT RNFL measurements performed better than ONH and macular measurements for detecting preperimetric glaucomatous damage in a cohort of glaucoma suspects. (ClinicalTrials.gov number, NCT00221897.).

Influence of keratometric readings on comparative intraocular pressure measurements with Goldmann, Tono-Pen, and noncontact tonometers.

Purpose: To evaluate the influence of keratometric measurements on the concordance of intraocular pressure (IOP) readings with three applanation tonometers. Patients and Methods: The IOPs of 404 eyes of 202 patients from a general eye clinic were measured by Goldmann, Tono‐Pen XL, and noncontact Nidek NT 2000 tonometers. Differences in the IOP measurements between Goldmann and the other two tonometers (▴IOPG‐TP and ▴IOPG‐NCT) were analyzed in the overall group and within three subgroups based on keratometry measures: flatter, intermediate, and steeper corneas (quartiles as cut‐off points). Regression analysis of &Dgr;IOP and keratometry measures was also performed. Right and left eyes were analyzed separately. Results: The IOP readings taken with the Goldmann tonometer were significantly higher than those taken with either of the other two tonometers within the overall study population. The &Dgr;IOP within the three keratometric subgroups was not statistically significant except for &Dgr;IOPG‐TP in the right eyes. Regression analysis showed that keratometry and &Dgr;IOPG‐TP and &Dgr;IOPG‐NCT had a significant but very weak coefficient of correlation in the right eye, but not in the left. Conclusion: Corneal curvature within the normal range does not have a clinically significant influence on the concordance of IOP readings obtained with Goldmann and Tono‐Pen or noncontact tonometers.

Intrinsically Photosensitive Retinal Ganglion Cell Activity Is Associated with Decreased Sleep Quality in Patients with Glaucoma

PURPOSE To use the pupillary light reflex and polysomnography to evaluate the function of intrinsically photosensitive retinal ganglion cells (ipRGCs) and to correlate this function with structural damage in glaucoma. DESIGN Cross-sectional study. PARTICIPANTS A study was conducted on both eyes of 45 participants (32 patients with glaucoma and 13 healthy subjects). METHODS For the pupillary reflex evaluation, patients were tested in the dark using a Ganzfeld system (RETIport; Roland Consult, Brandenburg, Germany); pupil diameter was measured with an eye tracker system. To preferentially stimulate ipRGCs, we used a 1-second 470-nm flash with a luminance of 250 cd/m(2). To stimulate different retinal photoreceptors, we used a 1-second 640-nm flash with a luminance of 250 cd/m(2). All of the subjects underwent polysomnography. Subjects underwent standard automated perimetry and optical coherence tomography (Cirrus HD-OCT; Carl Zeiss Meditec Inc, Dublin, CA). MAIN OUTCOME MEASURES Correlations between ipRGC activity, as measured by the pupillary light reflex, and polysomnography parameters, and correlations between retinal nerve fiber layer (RNFL) thickness and the pupillary light reflex and polysomnography parameters. RESULTS The mean patient ages in the healthy and glaucoma groups were 56.8±7.8 years and 61.5±11.6 years, respectively (P = 0.174). Patients with glaucoma had significantly lower average total sleep time, sleep efficiency, and minimum oxyhemoglobin saturation compared with the healthy subjects (P  = 0.008, P = 0.002, and P = 0.028, respectively). Patients with glaucoma had significantly higher arousal durations after falling asleep and more periodic limb movements (P = 0.002 and P = 0.045, respectively). There was an inverse correlation between the rapid eye movement latency and the peak of the pupillary response to the blue flash (P = 0.004). The total arousals were inversely correlated with the sustained blue flash response (P = 0.029). The RNFL thickness was associated with the peak and sustained responses to the blue flash (P  <  0.001 for both comparisons); however, RNFL thickness was only associated with the mean oxygen desaturation index among the polysomnography parameters (P = 0.023). CONCLUSIONS This study demonstrated that decreased ipRGC function caused by glaucoma affected pupillary response and sleep quality.

Association between corneal biomechanical properties and optic nerve head morphology in newly diagnosed glaucoma patients

Background:  To investigate the association between corneal biomechanics and optic nerve head morphology in newly diagnosed primary open‐angle glaucoma patients.

A positive association between intrinsically photosensitive retinal ganglion cells and retinal nerve fiber layer thinning in glaucoma.

PURPOSE To assess the integrity of intrinsically photosensitive retinal ganglion cells (ipRGCs) using the pupillary light reflex in glaucoma patients. METHODS A cross-sectional study was conducted, including 76 eyes from 38 patients with primary open-angle glaucoma and 36 eyes from 18 control subjects. The patients were tested in the dark with light stimuli using the Ganzfeld system, and the pupil diameter was measured with the assistance of an eye tracker consisting of two infrared cameras fit to an eyeglass frame. To preferentially stimulate ipRGCs, we used a 1-second 470-nm flash with a luminance of 250 cd/m(2). To stimulate different retinal photoreceptors (cones and rods), we used a 1-second 630-nm flash with a luminance of 250 cd/m(2). Standard automated perimetry (SAP), matrix frequency-doubling technology (FDT), and high-definition optical coherence tomography (Cirrus HD-OCT) were also performed. The correlation between the ipRGC-mediated sustained response following the pupillary light reflex and the structural and functional changes in glaucoma patients was analyzed using generalized estimating equation. RESULTS An association was observed between the average retinal nerve fiber layer (RNFL) thickness, as measured by Cirrus HD-OCT, and the sustained pupillary response to the blue flash (P = 0.024). The severity of glaucoma, based on the mean deviation of SAP (Hodapp-Anderson-Parrish system), was also associated with the sustained response to the blue flash (P = 0.006). CONCLUSIONS This study showed a correlation between the mean RNFL thickness and the pupillary light response. A decrease in the number of ipRGCs is potentially related to the reduced RNFL thickness.

Keratoconus prediction using a finite element model of the cornea with local biomechanical properties

PURPOSE The ability to predict and understand which biomechanical properties of the cornea are responsible for the stability or progression of keratoconus may be an important clinical and surgical tool for the eye-care professional. We have developed a finite element model of the cornea, that tries to predict keratoconus-like behavior and its evolution based on material properties of the corneal tissue. METHODS Corneal material properties were modeled using bibliographic data and corneal topography was based on literature values from a schematic eye model. Commercial software was used to simulate mechanical and surface properties when the cornea was subject to different local parameters, such as elasticity. RESULTS The simulation has shown that, depending on the corneal initial surface shape, changes in local material properties and also different intraocular pressures values induce a localized protuberance and increase in curvature when compared to the remaining portion of the cornea. CONCLUSIONS This technique provides a quantitative and accurate approach to the problem of understanding the biomechanical nature of keratoconus. The implemented model has shown that changes in local material properties of the cornea and intraocular pressure are intrinsically related to keratoconus pathology and its shape/curvature.

Factors associated with topographic changes of the optic nerve head induced by acute intraocular pressure reduction in glaucoma patients.

PurposeTo investigate factors associated with changes in optic nerve head (ONH) topography after acute intraocular pressure (IOP) reduction in patients with primary open-angle glaucoma (POAG).MethodsUntreated POAG patients (IOP >21 mm Hg) were prospectively enrolled. Systemic and ocular information were collected, including central corneal thickness (CCT) and corneal hysteresis (CH). All patients underwent confocal scanning laser ophthalmoscopy and tonometry (Goldmann) before and 1 h after pharmacological IOP reduction. The mean of three measurements was considered for analysis. Changes in each ONH topographic parameter were assessed (one eye was randomly selected), and those that changed significantly were correlated with patients systemic and ocular characteristics.ResultsA total of 42 patients were included (mean age, 66.7±11.8 years). After a mean IOP reduction of 47.3±11.9%, significant changes were observed in cup area and volume, and in rim area and volume (P<0.01), but not in mean cup depth (P=0.80). Multiple regression analysis (controlling for baseline IOP and magnitude of IOP reduction) showed that CH (r2=0.17, P<0.01) and diabetes diagnosis (r2⩾0.21, P<0.01) were negatively correlated with the magnitude of changes in ONH parameters, whereas the cup-to-disc ratio was positively correlated (r2=0.30, P<0.01). Age, race, disc area, and CCT were not significant (P⩾0.12). Including all significant factors in a multivariable model, only the presence of diabetes remained significantly associated with all ONH parameters evaluated (P<0.01).ConclusionsDifferent systemic and ocular factors, such as diabetes, CH, and the relative size of the cup, seem to be associated with the magnitude of changes in ONH topography after acute IOP reduction in POAG patients. These associations partially explain the ONH changes observed in these patients and suggest that other factors are possibly implicated in an individual susceptibility to IOP.

Corneal viscoelasticity differences between diabetic and nondiabetic glaucomatous patients.

PurposeTo investigate corneal viscoelasticity in primary open-angle glaucoma patients with and without diabetes mellitus, and to correlate corneal hysteresis (CH) with central corneal thickness (CCT). MethodsIn this cross-sectional study, 44 primary open-angle glaucoma patients [19 with diabetes (34 eyes) and 25 without diabetes (40 eyes)] underwent a complete ophthalmic examination. Data collected by masked investigators included CH and CCT using the Ocular Response Analyzer. The mean of 3 measurements was considered for each test. We analyzed the difference between the mean CH in both groups using a general linear model. Partial correlation coefficient between CH and CCT was also calculated. ResultsMean±SD age in diabetic and nondiabetic groups was 67.1±8.7 and 65.9±15.1, respectively (P=0.77). There was no significant difference regarding mean CCT between diabetic (531.7±31.3 μm) and nondiabetic (546.6±37.3 μm) groups (P=0.21). Patients with diabetes presented significantly higher CH values than patients without diabetes (9.1±1.9 mm Hg vs. 7.8±1.7 mm Hg, P=0.04). There was a significant and positive correlation between CH and CCT for all patients (r=0.407, P<0.001). ConclusionsPrimary open-angle glaucoma patients with diabetes have significantly higher CH values than those without diabetes. CH and CCT results were positively correlated. These findings merit further investigation to assess the role of different CH values on glaucoma evaluation and susceptibility.