Guillermo Coca Velarde

Corneal Biomechanical Metrics and Anterior Segment Parameters in Mild Keratoconus

PURPOSE To compare corneal hysteresis (CH), corneal resistance factor (CRF), spherical equivalent (SE), average central keratometry (K-Avg), corneal astigmatism (CA), corneal volume (CV), anterior chamber (AC) depth, and central corneal thickness (CCT) between patients with mild keratoconus and healthy controls and to estimate the sensitivity and specificity of CH and CRF in discriminating mild keratoconus from healthy corneas. DESIGN Comparative case series. PARTICIPANTS Sixty-three eyes (40 patients) with mild keratoconus (group 1) and 80 eyes from 40 gender- and age-matched controls (group 2). METHODS Patients underwent a complete clinical eye examination, corneal topography (Humphrey ATLAS; Carl Zeiss Meditec, Dublin, CA), tomography (Pentacam; Oculus, Wetzlar, Germany), and biomechanical evaluations (ocular response analyzer; Reichert Ophthalmic Instruments, Depew, NY). The receiver operating characteristic (ROC) curve was used to identify cutoff points that maximized sensitivity and specificity in discriminating mild keratoconus from normal corneas. MAIN OUTCOME MEASURES Corneal hysteresis, CRF, SE, K-Avg, CA, CV, AC depth, and CCT. The diagnostic performance of CH and CRF for detecting mild keratoconus was assessed using the ROC curve. RESULTS In group 1 versus group 2, the SE values (mean+/-standard deviation) were -3.55+/-2.87 diopters (D) versus -1.46+/-3.09 D (P = 0); K-Avg, 45.09+/-2.24 versus 43.24+/-1.54 D (P = 0); CA, 3.15+/-1.87 versus 1.07+/-0.83 D (P = 0); CV, 57.3+/-2.12 versus 60.86+/-3.39 mm3 (P = 0); AC depth, 3.19+/-0.35 versus 3.05+/-0.43 mm (P = 0.0416); CCT, 503+/-34.15 versus 544.71+/-35.89 microm (P = 0); CH, 8.50+/-1.36 versus 10.17+/-1.79 mmHg (P = 0); CRF, 7.85+/-1.49 versus 10.13+/-2.0 mmHg (P = 0). The ROC curve analyses showed a poor overall predictive accuracy of CH (cutoff, 9.64 mmHg; sensitivity, 87%; specificity, 65%; test accuracy, 74.83%) and CRF (cutoff, 9.60 mmHg; sensitivity, 90.5%; specificity, 66%; test accuracy, 76.97%) for detecting mild keratoconus. CONCLUSIONS The values for CH, CRF, CV, and CCT were statistically lower and those for SE, K-Avg, CA, and AC depth were statistically higher in patients with mild keratoconus compared with controls. Corneal hysteresis and CRF were poor parameters for discriminating between mild keratoconus and normal corneas. FINANCIAL DISCLOSURE(S) Proprietary or commercial disclosure may be found after the references.

Ocular response analyzer measurements in keratoconus with normal central corneal thickness compared with matched normal control eyes.

PURPOSE To compare corneal hysteresis (CH) and corneal resistance factor (CRF) in eyes with keratoconus with a central corneal thickness (CCT) ≥ 520 μm with CH and CRF in matched controls, and to estimate the sensitivity and specificity of these parameters for discriminating between the two groups. METHODS This prospective, comparative case series comprised 19 eyes of 19 patients with keratoconus with CCT ≥ 520 μm and 19 eyes of 19 healthy sex-, age-, and CCT-matched patients who underwent a complete clinical eye examination, corneal topography, tomography, and biomechanical evaluation. The receiver operating characteristic (ROC) curve was used to identify cutoff points that maximized the sensitivity and specificity for discriminating between groups. RESULTS Central corneal thickness was 543.1 ± 13.9 μm (range: 520 to 568 μm) in the keratoconus group and 545 ± 12.5 μm (range: 527 to 575 μm) in the control group (P=.6017). Corneal hysteresis was 9.22 ± 1.44 mmHg (range: 6.2 to 11.35 mmHg) in the keratoconus group and 10.58 ± 1.91 mmHg (range: 7.34 to 13.53 mmHg) in the control group (P=.0075). Corneal resistance factor was 8.62 ± 1.52 mmHg (range: 5.60 to 11.20 mmHg) in the keratoconus group and 10.30 ± 1.92 mmHg (range: 6.95 to 14.12 mmHg) in the control group (P=.0049). The ROC curve analyses showed a poor overall predictive accuracy of CH (cutoff, 9.90 mmHg; sensitivity, 78.9%; specificity, 63.2%; test accuracy, 71.05%) and CRF (cutoff, 8.90 mmHg; sensitivity, 68.4%; specificity, 78.9%; test accuracy, 73.65%) for detecting keratoconus in the eyes studied. CONCLUSIONS Corneal hysteresis and CRF were statistically lower in the keratoconus group compared with the control group. Given the large overlap, both CH and CRF had low sensitivity and specificity for discriminating between groups.

Biomechanical and Tomographic Analysis of Unilateral Keratoconus

PURPOSE To evaluate and compare tomographic, clinical, and biomechanical data of patients with unilateral keratoconus and healthy controls. METHODS Observational, case-control study. Complete clinical eye examination was followed by topographic (ATLAS), tomographic (Pentacam), and biomechanical (Ocular Response Analyzer) evaluation. Cases were sex- and age-matched with healthy individuals for controls. RESULTS Four patients had unilateral keratoconus, and eight healthy patients served as controls. Central corneal thickness was 508±16 μm in the keratoconus group, 531±12.7 μm in the fellow eye group, and 528.6±40.7 μm in the control group (P>.125, all comparisons). Central keratometry was 43.70±2.70 diopters (D) in the keratoconus group, 42.84±1.43 D in the fellow eye group, and 43.81±1.94 D in the control group (P>.45, all comparisons). Corneal astigmatism was 3.30±2.24 D in the keratoconus group, 1.38±1.49 D in the fellow eye group, and 1.34±1.13 D in the control group (P=.037 between the keratoconus and control groups; P=.25 between the keratoconus and fellow eye groups). Corneal hysteresis was 8.13±2 mmHg in the keratoconus group, 8.96±0.86 mmHg in the fellow eye group, and 9.89±1.33 mmHg in the control group (P>.064, all comparisons). Corneal resistance factor was 7.96±2.43 mmHg in the keratoconus group, 8.92±1.39 mmHg in the fellow eye group, and 9.90±2.24 mmHg in the control group (P>.33, all comparisons). CONCLUSIONS Corneal hysteresis and corneal resistance factor values were not statistically different among the groups; however, a trend for lower values was found for keratoconus and fellow eyes compared to controls. Data should be interpreted with caution because of the small sample.

Ability of corneal biomechanical metrics and anterior segment data in the differentiation of keratoconus and healthy corneas.

PURPOSE To evaluate the sensitivity, specificity, and test accuracy of corneal biomechanical metrics and anterior segment data in differentiating keratoconus from healthy corneas. METHODS Comparative case series. Patients with and without keratoconus (gender and age-matched) were submitted for complete eye examinations including corneal hysteresis (CH) and corneal resistance factor (CRF) as measured by the Ocular Response Analyzer and anterior segment data as gathered through Pentacam assessments. The anterior segment data measurement included average central keratometric readings (K-Ave), corneal astigmatism (CA), central corneal thickness (CCT), anterior chamber depth (AC depth) and corneal volume (CV). All parameters were assessed, compared and analyzed. A receiver operating characteristic (ROC) curve was used to identify the best cutoff point by which to maximize the sensitivity and specificity of discriminating keratoconus from normal corneas for each data category. RESULTS Seventy seven eyes from forty three patients (24 male, 19 female) with keratoconus and eighty six eyes from forty three (24 male, 19 female) healthy controls were enrolled. ROC curve analysis showed poor overall predictive accuracy for all studied parameters in differentiating keratoconus from normal corneas. The highest sensitivity (79.2%) was obtained for both AC depth and CH (cutoff points 3.22 mm and 9.39 mmHg respectively). The best specificity (89.5%) and test accuracy (80.34%) were obtained for CA (cutoff point of 2.2 D). CONCLUSION When considered together, studied parameters showed statistical differences between groups. However, when considered independently they presented low sensitivity, specificity and test accuracy in differentiating keratoconus from healthy corneas.

Corneal biomechanical evaluation in healthy thin corneas compared with matched keratoconus cases

PURPOSE To evaluate and compare corneal hysteresis (CH) and corneal resistance factor (CRF) in healthy eyes with a central corneal thickness (CCT) < 505 µm with CH and CRF in gender-, age-, and CCT-matched keratoconus cases, and to estimate the sensitivity and specificity of these parameters for discriminating between the two groups. METHODS Prospective, comparative case series. In total 46 eyes from 30 healthy patients with CCT < 505 µm, and 42 eyes from 30 CCT-, gender- and age-matched keratoconus cases were enrolled. Biomechanical metrics (CH and CRF) were measured using the Ocular Response Analyzer (ORA) and then compared. A receiver operating characteristic (ROC) curve was used to identify cut-off points to maximize the sensitivity and specificity for discriminating between the groups. RESULTS The CCT was 485.96 ± 17.61 µm (range, 438 - 505) in healthy thin corneas and 483.64 ± 16.19 µm (range, 452 - 505) in keratoconus; p=0.5225. CH was 8.63 ± 1.23 mmHg (range, 5.95 - 12.2) and 8.07 ± 1.17 mmHg (range, 4.9 - 9.85), respectively; p=0.0312. CRF was 8.43 ± 1.29 mmHg (range, 5.45 - 11.10) and 7.22 ± 1.34 mmHg (range, 4.7 - 9.45), respectively; p<0.001. ROC curve analysis showed a poor overall predictive accuracy of CH (cut-off, 8.95 mmHg; sensitivity, 63%; specificity, 23.8%; test accuracy, 44.30%) and CRF (cut-off, 7.4 mmHg; sensitivity, 28.3%; specificity, 40.5%; test accuracy, 34.12%) for detecting keratoconus in the eyes studied. CONCLUSION CH and CRF were statistically lower in keratoconus than in healthy thin corneas. However, CH and CRF offered very low sensitivity and specificity for discriminating the groups.

Activity of systemic lupus erythematosus in end-stage renal disease patients: study in a Brazilian cohort.

Background: Dialysis has been associated with lupus remission. We studied the prevalence of systemic lupus erythematosus (SLE) as a cause of end-stage renal disease (ESRD) in the metropolitan area of Rio de Janeiro and assessed disease activity in SLE patients on dialysis. Methods: Of 3,535 ESRD patients, 63 had SLE (1.8%). Fifty-seven entered the study (54 females, 3 males, 38 ± 10 years). Hemodialysis consisted of 3 sessions per week of about 4 h duration, blood flow of about 400 ml/min, bicarbonate dialysate ([Ca2+] = 2.5–3.5 mEq/l) at 500 ml/min and cellulose acetate or polysulfone dialyzers. Activity was initially defined as: non-renal (nr) SLE disease activity index (SLEDAI) of >0; use of at least 20 mg/day of prednisone; and/or any dose of another activity-controlling drug. Fifty-seven ESRD patients without SLE were used as controls. Results:Eighteen SLE patients were under drug treatment; of the remaining, 30 had an nrSLEDAI of >0 totaling 48 patients (84%) initially labeled as active. An apparent activity was also present in 21 controls (37%). Of those, 19 had an nrSLEDAI of <4. With a cutoff of ≧4, figures in each group would be 49 and 4%. Under this criterion, age was the only significant predictor of flare in our SLE ESRD population in a multivariate logistic regression model. Activity remained high in patients who were on dialysis for >5 years (7/18, 39%). Conclusion: SLE accounted for 1.8% of our ESRD patients. Application of SLEDAI to dialysis patients may require consideration of confounding factors related to the ESRD state. Even with a score of ≧4 as a cutoff, SLE activity in dialysis patients was high (49%) and long-lasting. Age was the major determinant of flare.

Central corneal thickness and biomechanical changes after clear corneal phacoemulsification.

PURPOSE To evaluate central corneal thickness (CCT) and ocular biomechanical properties in patients before and after clear corneal phacoemulsification. METHODS Corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated intraocular pressure (IOPcc), and Goldmann-correlated IOP (IOPg) were measured with the Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments) in 36 consecutive patients (47 eyes) who underwent clear corneal phacoemulsification. Central corneal thickness was measured with the Pentacam (Oculus Optikgeräte GmbH). All measurements were performed prior to surgery and at follow-up at 1, 7, and 30 days postoperatively. RESULTS Central corneal thickness was higher at 1 and 7 days compared to preoperatively (P<.05) but not at 30 days. Corneal hysteresis was lower at 1 day than preoperatively (P<.05) but not at 7 and 30 days. Corneal resistance factor was lower at 1, 7, and 30 days compared to preoperatively (P<.05). Corneal-compensated IOP was slightly lower at 1, 7, and 30 days compared to preoperatively, but was not statistically significant (P>.05). Goldmann-correlated IOP was statistically significantly lower at 1 and 7 days than preoperatively (P<.05). CONCLUSIONS Clear corneal phacoemulsification led to a change in ocular biomechanical properties. The increase in CCT after phacoemulsification was followed by a reduction in CRF and CH. Mean IOPcc was similar before and after phacoemulsification, indicating that IOPcc may be a more accurate indicator of true IOP than IOPg.

Influence of papain in biofilm formed by methicillin-resistant Staphylococcus epidermidis and methicillin-resistant Staphylococcus haemolyticus isolates

Methicillin-resistant Staphylococcus epidermidis (MRSE) and methicillin-resistant Staphylococcus haemolyticus (MRSHa) are important coagulase-negative staphylococci. They are often isolated from bacteremia in humans mainly due to their ability to form biofilm on the surfaces of medical devices. Papain is a complex mixture of proteolytic enzymes and peroxidases extracted from the latex of Carica papaya and it is recognized by accelerating the healing process of wounds. This study aimed to evaluate the ability of the MRSE and MRSHa isolates to produce biofilms. Besides this, the ability of papain to inhibit the formation of biofilms or to disrupt the ones already formed by those bacteria was analyzed. Thirty MRSHa and 30 MRSE were isolated from bacteremia and used in this study. It was observed that papain has ability to reduce biofilms formed by MRSE (p < 0.06) and by MRSHa (p = 0.0005). In addition, papain was able to disrupt mature biofilms made by MRSE (p = 0.014). No antibacterial activity of papain was observed for any isolates of MRSE and MRSHa tested. Papain has been demonstrated as a potential product for reducing biofilm.

Ocular Pulse Amplitude in Patients with Asymmetric Primary Open-Angle Glaucoma

Aim: To evaluate ocular pulse amplitude (OPA) using the dynamic contour tonometer (DCT) in patients with asymmetric primary open-angle glaucoma (POAG) and asymmetric intra-ocular pressure (IOP). Methods: The participants consisted of 48 patients (96 eyes) with asymmetric POAG. Three measurements of IOP and OPA were taken using DCT. The diagnosis of asymmetry required a difference of glaucomatous visual field loss greater than 6 dB in the global index MD and a difference of 5 mmHg in IOP measured by Goldmann tonometry between the more affected and the contra-lateral eye. All participants underwent full ophthalmologic clinical assessment including ultrasonic pachymetry and biometric measurements. Exclusion criteria were corneal diseases or scars, topical or systemic glaucomatous medications, and previous ocular surgery. Results: No difference (p = 0.142) was found between the axial length measurements of the better eyes group (22.95 ± 0.91 mm) and worse eyes group (22.85 ± 0.97 mm). There was a statistically significant difference (p = 0.011) between the central corneal thickness values of the better eyes group (537.08 ± 29.54 μm) and worse eyes group (534.40 ± 29.87 μm). The OPA values of the better eyes group (3.32 ± 1.14 mmHg) were significantly lower (p = 0.001) than those obtained in the worse eyes group (3.83 ± 1.27 mmHg). When correcting the OPA readings by the IOP there was no statistical difference between groups (p = 0.996). Conclusion: Higher OPA values were found in eyes with higher IOP levels and advanced glaucoma’s lesions in asymmetric hypertensive POAG patients. However, after the OPA correction by the IOP levels there was no more statistical difference between eyes.

A novel technique for the assessment of total liver blood flow in pregnancy: interrater and intrarater agreements

OBJECTIVE To improve the technique for hepatic blood flow examination, with the objective of investigating the role for Doppler flowmetry of the liver in monitoring pregnant females with pre-eclampsia. METHODS Two physicians independently examined a group of 50 healthy pregnant females. The main difference in the proposed technique is the measurement of the vessel cross-sectional area and the adjustment of the Doppler samples according to the diameter of each vessel. The portal vein was studied by using two approaches: in the epigastrium, to measure the diameter, and in the intercostal, for Doppler sample collection. The common hepatic artery was studied by using the epigastric approach. The average of three measurements of each vessel, in each subject, with intrarater and interrater agreements, was compared. RESULTS The intraclass correlation coefficient for the intrarater flow measurements of the hepatic artery and portal vein ranged from 0.98 to 0.99 (p < 0.0001). The intraclass correlation coefficients for the interrater flow measurements was 0.93 for the flow of the portal vein (p < 0.0001), 0.94 for the flow of the hepatic artery (p < 0.0001) and 0.96 for the measurement of the portal vein diameter (p < 0.0001). CONCLUSION The new technique for evaluation of blood flow to the liver displayed excellent reproducibility, possibly because of the adjustment of the Doppler samples according to the diameter of each vessel. Advances in knowledge: This approach will add reliability to the method. It opens a vast field of investigation given the importance of liver vascular lesions in pre-eclampsia.