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<h4>PURPOSE</h4><p>To evaluate corneal biomechanical metrics with tomographic parameters (given by the Oculus Pentacam) and refractive data in a population of healthy Brazilian patients.</p> <h4>METHODS</h4><p>Observational, cross-sectional study of 150 consecutive patients (53 men and 97 women; 260 eyes). Age, gender, central keratometric readings (central K), central corneal thickness (CCT), anterior chamber depth (ACD), spherical equivalent refraction, corneal hysteresis, and corneal resistance factor (CRF) were assessed and analyzed. </p> <h4>RESULTS</h4><p>Mean patient age was 46.5±21.04 years, average central K was 43.59±1.54 diopters (D), CCT was 545.05±35.41 µm, ACD was 2.96±0.52 mm, spherical equivalent refraction was –1.16±3.48 D, corneal hysteresis was 10.17±1.82, and CRF was 10.14±1.8 (range: 5.45 to 15.1). Mean CRF and corneal hysteresis were distinct among gender: CRF 10.326 in women and 9.810 in men (<i>P</i>=.0266); corneal hysteresis 10.421 in women and 9.727 in men (<i>P</i>=.0031). A negative correlation was found between both CRF and corneal hysteresis with age (r=–0.1255, <i>P</i>=.0434; and r=–0.2445, <i>P</i>=.0001, respectively). No association was found between CRF and average central K (r=0.0633, <i>P</i>=.3086), ACD (r=–0.0474, <i>P</i>=.4498), or spherical equivalent refraction (r=0.1028, <i>P</i>=.1061). Corneal hysteresis was not associated with age and average central K (r=0.0572, <i>P</i>=.3573), ACD (r=0.0060, <i>P</i>=.9236), or spherical equivalent refraction (r=0.0975, <i>P</i>=.1253). Corneal resistance factor and corneal hysteresis were positively associated with CCT (r=0.5760, <i>P</i>=0; and r=0.4655, <i>P</i>=0, respectively).</p> <h4>CONCLUSIONS</h4><p>Corneal biomechanical metrics of healthy Brazilian patients were associated with CCT, gender, and age. Corneal steepness, ACD, and spherical equivalent refraction did not affect corneal hysteresis and CRF values in the studied population. [<cite>J Refract Surg</cite>. 2008;24:941-945.]</p> <h4>AUTHORS</h4> <p>From Federal University of Sao Paulo (Fontes, Nosé); Fluminense Federal University, Rio de Janeiro (Ambrósio, Alonso, Velarde); and Renato Ambrósio Eye Institute, Rio de Janeiro (Ambrósio, Alonso, Jardim), Brazil.</p> <p>The authors have no proprietary interest in the materials presented herein. Dr Ambrósio is a consultant for Oculus and Reichert.</p> <p>Correspondence: Bruno M. Fontes, MD, Av das Acacias 150 bl 2 apto 1001, Barra da Tijuca, Rio de Janeiro – RJ, 22776-000, Brazil. Tel/Fax: 21 3151 3599; E-mail: <a href="mailto:brunomfontes@terra.com.br">brunomfontes@terra.com.br</a></p> <p>Received: March 15, 2007</p> <p>Accepted: September 19, 2007</p> <p><b>Posted online: April 30, 2008</b></p>

Progressive ''iatrogenic'' ectasia or keratectasia is a very severe complication of laser vision correction procedures. This is more common after LASIK, in which the lamellar cut promotes a larger biomechanical impact than the excimer laser ablation. However, ectasia has been also reported after surface ablation. Considering the severity of such complication, prevention is the best approach. Preoperative abnormal topography has been classically considered as the most important risk factor for ectasia development. Other risk factors are young age, high myopic corrections, low residual stromal bed and thin cornea. Multiple laser retreatments and thick flaps are additional risk factors, as are postoperative trauma or intense eye rubbing. However, there are mysteries related to the cases that develop ectasia with no identifiable risk factors, and also to the cases of successful LASIK that remain stable despite of multiple risk factors (including abnormal topography). Corneal ectasia may occur due to two distinct mechanisms: 1. preoperative abnormal (weak) corneal stroma; and 2. severe biomechanical impact (weakening) from the procedure. While these mechanisms are distinct, there is an association and overlapping between the level of susceptibility of any cornea and the biomechanical impact of the procedure. Corneal tomography and biomechanical assessment provide an advanced understanding of the cornea that augments the sensitivity to identify a very mild (forme fruste keratoconus) form of ectasia, that may still present with relatively normal front surface topography. Such an enhanced screening approach not only augments the sensitivity to detect susceptible cases, but also provides higher specificity for a cornea with irregular topography, considered as a keratoconus suspect, that may be suitable for laser vision correction.

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. Keywords: Cornea; Corneal diseases; Corneal topography; Biomechanics; Keratoconus. RESUMOObjetivo: Avaliar a sensibilidade, especificidade e acurácia de parâmetros biomecânicos e anatômicos do segmento anterior isolados na diferenciação de córneas saudáveis e com ceratocone. Métodos: Estudo tipo série de casos comparativa. Pacientes com ceratocone e controles saudáveis foram pareados (idade e sexo) e submetidos a exame oftalmológico completo, incluindo avaliação biomecânica (ORA) e tomográfica (Pentacam). Ceratometria central média, astigmatismo corneano, espessura corneana central, profundidade da câmara anterior, volume corneano, CH e CRF foram estabelecidos, avaliados e comparados. Curvas ROC (Receiver operating characteristic) foram utilizadas para identificar o melhor valor de corte que apresentasse a maior sensibilidade e especificidade na discriminação entre ceratocone e córneas saudáveis para cada dado estudado. Resultados: Setenta e sete olhos de 43 pacientes com ceratocone (24 homens e 19 mulheres) e 86 olhos de pacientes saudáveis (24 homens e 19 mulheres) foram incluídos no estudo. Curvas ROC mostraram baixa acurácia na predição do diagnóstico de ceratocone em todos os parâmetros isolados estudados. Maior sensibilidade encontrada foi 79,...

We report a case of a new syndrome, late asymmetric vault of the AT45 Crystalens intraocular lens (IOL) (Eyeonics Inc.). The late vault, which occurred in 6 month after implantation of the IOL, caused a decrease in uncorrected distance and near acuities and minus-cylinder axis perpendicular to the haptics. Treatment with neodymium:YAG laser capsulotomy and fibrotic band release was successful.

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