Bruno Machado Fontes

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.

Evaluation of corneal shape and biomechanics before LASIK.

The preoperative evaluation is of critical importance for success in laser in situ keratomileusis (LASIK). This examination should fulfill 3 main purposes: counseling and educating the candidates, surgery planning, and screening for cases at higher risk for complications. It is critical to interview each refractive patient to assess their individual needs and to provide realistic expectations. A thorough ophthalmologic examination is mandatory, including specific complementary examinations to characterize many aspects of the cornea and the optics of the eye. In fact, it is notable that refractive surgery has motivated tremendous development for advanced diagnostic methods, among many others advancements and innovations in Ophthalmology. One of the most important aspects of the preoperative examination of LASIK candidates is to screen cases at risk for progressive ectasia.

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.

Visual outcomes after accommodating intraocular lens implantation.

PURPOSE: To evaluate and compare the visual outcomes and accommodative amplitude in cataract patients after implantation of the Crystalens intraocular lens (IOL) (Eyeonics) versus standard monofocal IOLs. SETTING: Ten clinics in a nationwide multicenter study in the United States. METHODS: A multicenter comparative interventional case series with masked randomized postoperative examination of 224 eyes of 112 patients was performed by a single observer. Patients were divided into 2 groups (56 patients; 112 eyes each) depending on which IOL was implanted (Crystalens or monofocal). Accommodation was measured using 1 objective (dynamic retinoscopy) and 2 subjective methods (defocus and near point of accommodation). Visual acuity measurements were performed under the same conditions with standard visual acuity charts. RESULTS: Uncorrected monocular near vision was significantly better in the Crystalens group than in the standard monofocal group, with 101 of 112 eyes (90%) and 17 of 112 (15%), respectfully, reading J3 or better postoperatively. All 56 Crystalens patients had a binocular uncorrected near visual acuity of J3 or better compared with 16 of 56 (29%) standard monofocal patients. The mean postoperative monocular (0.85 ± 0.30 [SD] versus 0.70 ± 0.19, P<.01) and binocular (1.16 ± 0.17 versus 1.01 ± 0.14, P<.01) distance uncorrected visual acuities were also better in the Crystalens group than in the control group. All patients in the study achieved a corrected distance visual acuity of 20/20 or better. Measures of accommodation were significantly higher in Crystalens patients than in the monofocal IOL patients (dynamic retinoscopy 2.42 ± 0.39 diopters [D] versus 0.91 ± 0.24 D, P<.01; monocular defocus 1.74 ± 0.48 D versus 0.75 ± 0.25 D, P<.01; monocular near point of accommodation 9.5 ± 3.1 inches versus 34.7 ± 9.8 inches, P<.01). Perceived accommodation (5.79 D) was significantly greater than the measured accommodation (1.96 to 2.42 D) in Crystalens patients (paired t test, P<.01). CONCLUSIONS: The Crystalens IOL provided better uncorrected near and distance visual outcomes than standard monofocal IOLs in all analyses performed. Patients perceived a greater accommodation than measured. Understanding why this occurred could lead to valuable advances in accommodating IOL technology.

Effects of age on corneal deformation by non-contact tonometry integrated with an ultra-high-speed (UHS) Scheimpflug camera

PURPOSE To correlate parameters derived from corneal deformation resulting from non-contact tonometry integrated with an ultra-high-speed (UHS) Scheimpflug camera (Oculus Corvis ST, Scheimpflug Technology; Wetzlar, Germany) with age in normal eyes from young patients. METHODS Observational, retrospective study involving one eye randomly selected from study participants, totaling 89 healthy eyes. The Scheimpflug images were taken with an ultra-high-speed camera during each measurement by the corvis ST. The deformation amplitude (DA) and other parameters (e.g., pachy apex, intraocular pressure, 1(st) A time, highest concavity-time, 2(nd) A time, 1(st) A Length, 2(nd) A Length, Wing-Dist, curvature radius highest concavity, curvature radius normal, Vin, Vout) measured by the corvis ST were correlated with age. The Kolmogorov-Smirnov test was applied, and Spearmans correlation test was utilized to evaluate the parameters measured by the Corvis ST and age. RESULTS Mean patient age was 27.50 ± 6.30 years. The highest concavity-time was the only studied parameter statistically significantly correlated to age (i.e., p=0.04, rs=0.18). All other corvis parameters were not correlated to age. This included DA (p=0.319), intraocular pressure (p=0.854), pachy apex (p=0.066), 1(st) A time (p=0.959), 2(nd) A time (p=0.561), 1(st) Length (0.552), 2nd Length (p=0.697), Wing-Dist (p=0.769), curvature radius HC (p=0.145), curvature radius normal (p=0.513), Vin (p=0.980) and Vout (p=0.592). CONCLUSIONS In healthy eyes, age and pressure or biomechanics as derived from the Corvis ST parameters were not associated with exception to highest concavity-time, i.e., the time from starting until the highest concavity is reached.

Staining patterns in dry eye syndrome: rose bengal versus lissamine green.

Purpose: To evaluate and compare corneal staining patterns of lissamine green (LG) versus rose bengal (RB) in patients with dry eye syndrome. Secondary objectives included addressing patients comfort after instillation and to correlate disease severity with staining patterns. Methods: Randomized, comparative, crossover series. Patients with previous diagnosis of mild to moderate dry eye syndrome were divided in 2 groups regarding dye instillation order (group A: RB first; group B: LG first). Both dyes were applied in regular intervals, and a staining score (van Bijsterveld scale) was used to correlate and compare the results. Disease severity was determined by the Ocular Surface Disease Index. Comfort was evaluated by patients answer in an objective questionnaire. Results: Sixty eyes of 30 consecutive patients (24 females and 6 males) were included. There was no statistical difference between groups regarding disease severity, sex, or age. LG and RB showed good clinical correlation in both groups (group A: r = 0.939, P < 0.001; group B: r = 0.915, P < 0.001). LG was better tolerated than RB (P = 0.003 in both groups). Overall, we found a low statistical correlation between disease severity and staining scores. Conclusions: Both LG and RB showed similar staining patterns. RB was found to provide greater patient discomfort. There was no correlation between disease severity (addressed by the ocular surface disease index questionnaire) and staining patterns (measured by the van Bijsterveld scale).

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.

Ocular Biomechanical Metrics by CorVis ST in Healthy Brazilian Patients

PURPOSE To evaluate ocular biomechanical metrics given by the CorVis ST (Oculus, Inc., Berlin, Germany) in a population of healthy Brazilian patients. METHODS An observational and cross-sectional study involving 1 eye randomly selected from 90 healthy patients. Studied parameters (including deformation amplitude, first applanation time, highest concavity time, second applanation time, first applanation length, second applanation length, curvature radius highest concavity, curvature radius normal, velocity in, and velocity out) derived from the CorVis ST were correlated to central corneal thickness from the Pentacam (Oculus, Inc.). Differences between data on the basis of gender were evaluated. RESULTS Mean patient age was 35.80 ± 12.83 years (range: 21.07 to 78.84 years). Mean central corneal thickness was 547.50 ± 32.00 μm (range: 490 to 647 μm) and mean spherical equivalent refraction was -3.29 ± 3.69 diopters (range: -9.50 to +10.37 diopters). Mean deformation amplitude was 1.05 ± 0.08 mm (range: 0.91 to 1.26 mm). Highest concavity time was 18.38 ± 0.93 ms (range: 16.95 to 21.07 ms). Intraocular pressure was 16.43 ± 2.15 mm Hg (range: 11.50 to 21.0 mm Hg). First applanation time was 8.32 ± 0.33 ms (range: 7.53 to 9.12 ms) and second applanation time was 23.80 ± 0.44 ms (range: 22.76 to 24.95 ms). First applanation length (max) was 2.07 ± 0.38 mm (range: 1.20 to 3.10 mm) and second applanation length (max) was 2.37 ± 0.47 mm (range: 1.33 to 4.12 mm). Curvature radius highest concavity was 11.09 ± 2.06 mm (range: 7.58 to 15.98 mm) and curvature radius normal was 7.59 ± 0.67 mm (range: 6.82 to 11.02 mm). Velocity in was 0.21 ± 0.05 m/s (range: 0.16 to 0.72 m/s) and velocity out was -0.33 ± 0.07 m/s (range: -0.72 to -0.20 m/s). Studied parameters were not associated with gender. CONCLUSIONS Eight of 11 ocular biomechanical metrics given by the CorVis ST were associated with central corneal thickness, but the influence of central corneal thickness on these measurements was low.

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.

Zika virus-related hypertensive iridocyclitis

Dear Editor: The epidemic of Zika virus infection in Brazil has lead to the description of new complications and manifestations such as Guillain-Barré syndrome in adults and microcephaly in newborns. Zika virus is a flavivirus transmitted to humans primarily through the bite of an infected Aedes species mosquito. It was first isolated and described in Africa, later spreading to Asia, Micronesia, Oceania, and to the Americas. It is thought that only 1 in 5 people infected with the Zika virus will become symptomatic. The most common systemic manifestations include: fever, arthralgia, malaise, and skin rash. More recently, retinal abnormalities were described in children with microcephaly attributed to Zika virus infection during pregnancy. The purpose of this letter is to describe a case of bilateral hypertensive iridocyclitis attributed to Zika virus in an otherwise healthy young male. A 39-year-old male physician was clinically diagnosed with Zika virus infection. This occurred in a neighborhood with an outbreak of this disease. He presented with classic signs of fever, diffuse maculopapular rash, and severe arthralgia. Systemic work-up ruled out other possible infectious such as Dengue, CMV, Herpes Simplex, Toxoplasmosis, Syphilis, Rubella, spondyloarthropathies, rheumatic diseases, and systemic vasculitis. One week after the systemic manifestations the patient complained of bilateral ocular discomfort for near tasks, blurry vision, and mild redness. Best-corrected visual acuity was 20/40 in each eye. Slit-lamp examination revealed moderate ciliary injection, mild anterior chamber reaction (1+ cells), and miosis in both eyes. Intraocular pressure (Goldmann applanation tonometry) was 40 and 28 mmHg in right and left eyes, respectively. He was treated with topical medications (steroids, cycloplegic and hypotensive agents) for several weeks. This achieved improvement of visual acuity, lowering of intraocular pressure, and complete resolution of symptoms. Although no specific protein-chain reaction (PCR) for Zika virus has been performed, it is very likely that this bilateral hypertensive iridocyclitis occurred secondary to Zika virus. Since it has been shown that the virus penetrates the blood-brain and ocular barriers, many other ocular findings (in addition to conjunctivitis and retinal abnormalities) might be observed in the future. Physicians should be attentive to ocular complaints when treating patients with Zika virus infection and refer patients to a specialist for complete ocular examination.