Implantation of asymmetrical corneal intrastromal rings: A case series.

This case series reports eight eyes with keratoconus treated with laser implantation of one or two segments of progressive thickness corneal intrastromal ring (PT-ICRS). In this case series, it was evident that the insertion of PT-ICRS induces more pronounced corneal flattening at the thickest point, causing a reduction in distortion (coma) and lower astigmatism, resulting in a remarkable improvement in vision. Compared to the implementation of traditional intrastromal rings, the PT-ICRS variant showed superior results despite the small sample size. However, the same degree of asymmetry enhancement was not observed in cases in which a 330° PT-ICRS was implanted, despite the improvement in visual results when replacing a 320° traditional ring with a 330° PT-ICRS. These conclusions are limited as this is a case series with few cases.

Outcomes of accelerated corneal cross-linking for pediatric and adult keratoconus: a comparative study.

PURPOSE: To compare the visual, refractive, and topographic outcomes of a high irradiance accelerated corneal crosslinking (ACXL) protocol after a 12-month follow-up between pediatric and adult patients with progressive keratoconus (KC). METHODS: Retrospective, comparative, cohort study. Patients with KC were divided into two groups: pediatric (≤ 18 years) and adult (> 18 years). All of them were managed with epi-OFF ACXL (30 mW/cm2, 8 min, pulsed 1:1 on and off = 7.2 J/cm2). Visual, refractive, and topographic values were measured preoperatively and at 1, 3, 6, and 12 months postoperative. KC progression, defined as a Kmax increase of ≥ 1D during follow-up, was recorded. RESULTS: Eighty-nine eyes (53 patients) were included for analysis; 45 (50.6%) eyes were from pediatric patients and 44 (49.4%) from adults. At one-year follow-up, pediatric patients experienced significantly higher rates of progression (22.2% vs. 4.5%, p = .014). Contrariwise, female gender (Beta = - 3.62, p = .018), a baseline uncorrected visual acuity of Snellen ≥ 20/60 (Beta = - 5.96, p = .007), and being ≥ 15 years at ACXL treatment (Beta = - 0.31, p = .021) were associated with non-progressive disease. A significant improvement in best-corrected visual acuity, Kmin, Km, and Kmax was recorded in both groups. Overall, 86.5% of eyes from both groups showed Kmax stabilization or improvement. CONCLUSIONS: Despite the similarity in visual, refractive, and topographic outcomes in both groups, younger age was associated with KC progression after ACXL at one year of follow-up.

Prevalence of Keratoconus Among High School Students in Southern Brazil: A Community-Based Study.

OBJECTIVES: This study aimed to determine the prevalence of keratoconus (KC) in teenagers who live in Southern Brazil and detect any possible associated factors. METHODS: This prospective, observational, mobile clinic-based cross-sectional study collected data from students between 14 and 21 years from seven high schools who were living in the Greater Porto Alegre metropolitan region in Southern Brazil. Subjects were clinically surveyed and examined using a slitlamp and rotational Scheimpflug corneal tomography system. All data were collected at the mobile clinic during a single visit. RESULTS: Eight-hundred twenty-six students were evaluated (357 boys and 469 girls) with an average age of 16.7±1.2 years. Six subjects were classified as having KC (four girls), yielding a prevalence rate of 0.73% (95% confidence interval, 0.27%-1.57%) or one per 137 teenagers in Southern Brazil. Logistic regression showed an association between KC and positive history of eye rubbing ( P =0.02). CONCLUSION: According to our investigation, this is the first KC prevalence study in South America using the latest technologies (Scheimpflug imaging). The prevalence of KC among teenagers in Southern Brazil is within the highest reported worldwide. We also found an association between KC and history of eye rubbing. Keratoconus is not an uncommon disorder in our population, and the efforts to identify the disease and reduce its risk factors in an earlier phase are justified.

Keratoconus Frequency and Associated Risk Factors Among Patients Younger Than 18 Years With Significant Refractive Errors.

INTRODUCTION: Keratoconus is an ectatic corneal disorder that causes low vision secondary to high myopia, irregular astigmatism, and loss of corneal transparency. In children, the disease behaves aggressively, progresses rapidly, is diagnosed at advanced stages, and presents an increased risk for corneal transplantation; however, only few studies in children have been conducted. PURPOSE: The aims of this study were to determine the frequency of keratoconus in patients younger than 18 years who underwent the Pentacam study because of high myopia or high astigmatism in the oblique axis, analyze topographic criteria and classify them into severity groups, and identify associated risk factors. METHODS: This was a retrospective observational cross-sectional study in which Pentacam examinations were analyzed. Frequency of keratoconus was determined and patients were classified according to visual acuity and severity scales. Medical records were reviewed to identify associated risk factors. RESULTS: Four hundred twenty-six patients younger than 18 years were included, 40 (9.4%) had keratoconus according to Pentacam criteria. The mean age at diagnosis was 14.9 years, with male predilection (75%). Atopy was the only statistically significant risk factor, present in 85%. Family history was present in 7.5%. There were no differences in the distribution in groups according to visual acuity or Amsler-Krumeich scale. Most frequent ABCD classification was A2 (35.6%), B4 (47.9%), and C0 (35.6%), posterior curvature radius being a significant severity criterion. CONCLUSIONS: The study found that frequency of keratoconus in children is higher than previously reported. Atopy has a clear and possible causal association. Early detection should be sought to reduce the risk of progression. Pentacam is a fundamental tool for early diagnosis using simple criteria.

Asimetría interocular en el queratocono pediátrico / Interocular Asymmetry in Pediatric Keratoconus

El queratocono es una ectasia corneal bilateral asimétrica, en etapas iniciales no se evidencia la afectación binocular. El conocimiento del grado de asimetría en el queratocono pediátrico permite tomar decisiones oportunas en el manejo de los pacientes. Se realizó este trabajo con el objetivo de describir las características clínicas y el tratamiento de tres casos pediátricos con diferente grado de asimetría interocular del queratocono, atendidos en la consulta provincial de ectasias corneales pediátricas en Ciego de Ávila. Los pacientes mostraron diferencia entre ambos ojos de los signos clínicos, la refracción y las variables topográficas. Al paciente dos se le diagnosticó queratocono en un ojo, sin evidencias clínicas ni topográficas de la enfermedad en el ojo contralateral. Todos los pacientes mostraron astigmatismo miópico compuesto en ambos ojos y se les indicó corrección óptica. Al paciente uno se le corrigió con cristales, al dos con lentes de contacto rígidos de gas permeable y al tercero con piggyback en un ojo y lentes de contacto rígidos de gas permeable en el otro. Presentaron, además, una ambliopía asociada y se les orientó tratamiento oclusivo y tareas de visión cercana en los pacientes dos y tres. Es frecuente encontrar asimetría interocular en pacientes pediátricos con queratocono por la diferencia de progresión entre ambos ojos. El seguimiento periódico permite diagnosticar la enfermedad en el ojo contralateral en pacientes con diagnóstico de queratocono en un ojo, indicar una corrección óptica individualizada, sobre todo en presencia de anisometropía, y monitorizar la evolución de la ambliopía refractiva asociada con frecuencia(AU)

Keratoconus is an asymmetric bilateral corneal ectasia, in early stages binocular involvement is not evident. Knowledge of the degree of asymmetry in pediatric keratoconus allows timely decisions in patient management. This research was carried out with the objective of describing the clinical characteristics and the treatment of three pediatric cases with different degree of interocular asymmetry of keratoconus, treated in the provincial consultation of pediatric corneal ectasia in Ciego de Avila. Patients showed difference between both eyes in clinical signs, refraction and topographic variables. Patient two was diagnosed with keratoconus in one eye, with no clinical or topographic evidence of the disease in the contralateral eye. All patients showed compound myopic astigmatism in both eyes and optical correction was indicated. Patient one was corrected with glasses, patient two with rigid gas permeable contact lenses and patient three with piggyback in one eye and rigid gas permeable contact lenses in the other eye. They also presented an associated amblyopia and were directed occlusive treatment and near vision tasks in patients two and three. It is common to find interocular asymmetry in pediatric patients with keratoconus due to the difference in progression between the two eyes. Periodic follow-up makes it possible to diagnose the disease in the contralateral eye in patients diagnosed with keratoconus in one eye, to indicate individualized optical correction, especially in the presence of anisometropia, and to monitor the evolution of frequently associated refractive amblyopia(AU)

Piggyback corneal como alternativa en el tratamiento del queratocono / Corneal Piggyback as an Alternative in the Treatment of Keratoconus

El queratocono es una afección inflamatoria, es una ectasia corneal que se caracteriza por un aumento de la curvatura corneal. Se describe como una enfermedad progresiva y asimétrica asociada con cambios estructurales en la organización del colágeno corneal. Existen diferentes opciones terapéuticas con el objetivo de estabilizar la superficie corneal, mejorar la visión y evitar su progresión. El sistema piggyback consiste en adaptar un lente rígido de gas permeable con alta permeabilidad al oxígeno sobre un lente de contacto hidrofílico, es ideal para pacientes que requieren la óptica de un lente de contacto rígido, pero tienen dificultades con su material. Se indica cuando existe una intolerancia a los lentes rígidos de gas permeable, en córneas irregulares y con curvaturas avanzadas. Se presenta una paciente de 24 años de edad con diagnóstico de queratocono desde los 10 años de edad que se corregía con lente rígido de gas permeable. Acudió a consulta del servicio de córnea del Instituto Cubano de Oftalmología Ramón Pando Ferrer, en el año 2010 porque comenzó a presentar intolerancia a los lentes. Debido a que la paciente no presentaba criterio quirúrgico y tenía una agudeza visual mejor corregida con lentes de 1,0 en ambos ojos, se decidió realizar el tratamiento con piggyback corneal. Pese al seguimiento, como parte de la progresión de la enfermedad, a los 10 años de mantenerse con el piggyback, presentó un hidrops corneal agudo, el cual fue tratado. En la actualidad la paciente mantiene seguimiento anual por consulta, sin progresión del queratocono y sin complicaciones con el tratamiento de piggyback corneal(AU)

Keratoconus is an inflammatory condition, a corneal ectasia characterized by increased corneal curvature. It is described as a progressive and asymmetric disease associated with structural changes in the organization of corneal collagen. There are different therapeutic options to stabilize the corneal surface, improve vision and prevent progression. The piggyback system consists of fitting a rigid gas permeable lens with high oxygen permeability over a hydrophilic contact lens, it is ideal for patients who require the optics of a rigid contact lens, but have difficulties with its material. It is indicated when there is intolerance to rigid gas permeable lenses, in irregular corneas and with advanced curvatures. We present a 24-year-old female patient with a diagnosis of keratoconus since she was 10 years old, which was corrected with a rigid gas permeable lens. She went to the cornea service of the Cuban Institute of Ophthalmology Ramón Pando Ferrer, in 2010 because she began to present intolerance to lenses. Since the patient did not present surgical criteria and had a visual acuity better corrected with 1.0 lenses in both eyes, it was decided to perform corneal piggyback treatment. Despite the follow-up, as part of the progression of the disease, after 10 years of piggyback, she presented an acute corneal hydrops, which was treated. At present, the patient maintains annual follow-up via consultation, without progression of keratoconus and without complications with the corneal piggyback treatment(AU)

Long-term follow-up of repeated corneal cross-linking for progressive keratoconus in young patients / Acompanhamento a longo prazo do retratamento com cross-linking corneano para ceratocone em progressão em pacientes jovens

ABSTRACT Objective: To evaluate the long-term safety and efficacy of repeated corneal cross-linking in eyes of children and adolescents with progressive keratoconus. Methods: This retrospective study included nine eyes of nine consecutive patients with progressive keratoconus who underwent repeated corneal cross-linking 3.9 (range of 1.6 to 5.6) years after a primary one. All patients were followed for a mean period of 9.11 (range of 6 to 11) years after first treatment and 5.44 (range of 4 to 9) years, after corneal cross-linking retreatment. Results: Nine eyes of nine patients (six male) with progressive keratoconus underwent primary corneal cross-linking from 2009 to 2011. Despite the stability achieved with the epi-off corneal cross-linking, keratoconus continued to progress after some time. Mean time to documented evidence of keratoconus progression after primary corneal cross-linking was 3.9 (range of 1.6 to 5.6) years. All eyes were retreated as soon as progression was noted. At the last follow-up visit, 5.44 (range of 4 to 9) years after repeated corneal cross-linking, there was a significant decrease of 2.02 D in mean maximum topographic K-value (p = 0.045) and 1.95D in mean topographic K-value (p = 0.007). Conclusion: Repeated corneal cross-linking seems to be a safe and effective procedure to halt keratoconus progression after a primary corneal cross-linking failure.

RESUMO Objetivo: Avaliar a segurança e a eficácia a longo prazo da repetição do cross-linking corneano em olhos de crianças e adolescentes com ceratocone progressivo. Métodos: Estudo retrospectivo que incluiu nove olhos de nove pacientes consecutivos com ceratocone progressivo, que foram submetidos a retratamento com cross-linking corneano de 3,9 (variação de 1,6 a 5,6) anos após tratamento primário com cross-linking corneano. Todos os pacientes foram acompanhados por um período médio de 9,11 (variação de 6 a 11) anos após o primeiro tratamento e 5,44 (variação de 4 a 9) anos após retratamento com cross-linking corneano. Resultados: Nove olhos de nove pacientes (seis homens) com progressão do ceratocone foram submetidos a cross-linking corneano primário de 2009 a 2011. Apesar da estabilidade alcançada com o epi-off cross-linking corneano, o ceratocone continuou a progredir após algum tempo. O tempo médio para evidência documentada de progressão do ceratocone após cross-linking corneano primário foi de 3,9 (intervalo de 1,6 a 5,6) anos. Todos os olhos foram retratados com cross-linking corneano, assim que a progressão foi observada. Na última consulta de acompanhamento, 5,44 (variação de 4 a 9) anos após a repetição do cross-linking corneano, houve diminuição significativa de 2,02 D na média da curvatura máxima (p = 0,045) e 1,95 D na média da curvatura média (p = 0,007). Conclusão: O retratamento com cross-linking corneano parece ser um procedimento seguro e eficaz para interromper a progressão do ceratocone após falha primária do cross-linking corneano.

Late-onset distal-apical intracorneal ring-segments keratopathy: an analysis of a large sample in a multicenter study.

PURPOSE: To review the prevalence and describe the characteristics, of cases with late-onset intracorneal ring segments (ICRS) keratopathy in a multicenter study. METHODS: A retrospective multicentric case-series study was performed in a specialized keratoconus service, from Buenos Aires, Argentina. An electronic clinical chart from patients with ICRS keratopathy between January 1999 and January 2019 was reviewed. We included cases with late-onset distal-apical ICRS keratopathy, which was defined as a persistent corneal lesion developed 12 months or later after implantation, located over, around, or closer to the ICRS. All the surgeries were performed by a manual corneal tunnel creation technique. Samples were taken to rule out infectious etiology. RESULTS: From 5217 eyes that underwent ICRS implantation, 13 cases (0.24%) were detected. The keratopathy onset was 72 ± 42.98 months (29-133) after ICRS implantation. Cultures were negative in all cases. An ICRS exchange was made for five cases in stage I and four in stage II. Four cases presented with partial ICRS extrusion in stage III. ICRS exchange was possible in two of them and a penetration keratoplasty was necessary for the rest. All cases remained stable 1 year after surgical procedures. CONCLUSIONS: A late-onset distal-apical ICRS keratopathy was detected with low prevalence (0.24%) in a large sample. It was classified into three stages according to its severity. Different treatments were selected for each stage, obtaining stable results 1 year after treatment.

Colombian Ocular Diseases Epidemiology Study (CODES): incidence and sociodemographic characterisation of keratoconus between 2015 and 2020.

OBJECTIVE: To estimate the incidence and describe the demographic characteristics of keratoconus (KC) in Colombia using national health registry data between January 1st 2015 and December 31th 2020. METHODS AND ANALYSIS: We conducted a nationwide, population-based study using the Integrated Social Protection Information System from the Colombian Ministry of Health, the unique official database in the country. We used the International Classification of Diseases code for KC (H186) to identify the number of new cases of KC and estimate the incidence rates both overall and according to age and sex. We made a standard morbidity ratio map to graph Colombia's morbidity risk of KC onset. RESULTS: Of 50 372 424 subjects, 21 710 had KC between 2015 and 2020. However, due to the COVID-19 pandemic, all the incidence rates of this study were based on the 18 419 reported until 2019. The incidence rate in the general population was 10.36 (95% CI 10.08 to 10.64) per 100 000 inhabitants. The incidence peak among males was in their early 20s and females in their late 20s. The overall male to female incidence rate ratio was 1.60. Regarding the distribution of the disease, most cases were reported in Bogotá (48.64%), Antioquia (14.04%) and Cundinamarca (10.38%). CONCLUSION: We performed the first nationwide, population-based study of KC in Latin America, finding distribution patterns similar to those reported in the literature. This study provides valuable information on the epidemiology of KC in Colombia, which is helpful in the development of policies for the diagnosis, prevention and treatment of the disease.

Results of one decade of optical keratoplasty in pediatric patients.

BACKGROUND: Keratoplasty in the pediatric population has been considered a high-risk procedure. OBJECTIVE: To know the demographic data of patients younger than 18 years treated with optical keratoplasty, indications for surgery and its results. MATERIAL AND METHODS: A retrospective study was carried out at Conde de Valenciana Ophthalmology Institute, in which the medical records of patients younger than 18 years treated with optical keratoplasty from 2009 to 2019 were analyzed. RESULTS: A total of 53 eyes were included. The most common diagnosis and procedure were keratoconus and penetrating keratoplasty, respectively. Mean initial visual acuity was 2.05 ± 0.99 logMAR, and 0.82 ± 1.33 at last visit. Survival time was 130.34 months. Four failures were recorded. As for associated surgeries, corneal wound closure was recorded in seven eyes prior to transplant; during the keratoplasty procedure, anterior vitrectomy in two eyes, and after the transplant, Ahmed valve implantation and re-suture. A total of eight eyes had glaucoma, five of them diagnosed prior to transplantation. Regarding rejection, 15 eyes had an episode during follow-up, and mean time to transplant rejection was 10.8 months. CONCLUSION: Prolonged graft survival can be achieved with better knowledge and management of different associated factors.

ANTECEDENTES: La queratoplastia en población pediátrica ha sido considerada un procedimiento de alto riesgo. OBJETIVO: Conocer datos demográficos de pacientes menores de 18 años tratados con queratoplastia óptica, indicaciones de la cirugía y sus resultados. MATERIAL Y MÉTODOS: Se realizó un estudio retrospectivo en el Instituto de Oftalmología Conde de Valenciana, en el que se revisaron expedientes de pacientes menores de 18 años tratados con queratoplastia óptica de 2009 a 2019. RESULTADOS: Un total de 53 ojos fueron incluidos. El diagnóstico y el procedimiento más comunes fueron el queratocono y la queratoplastia penetrante. El promedio de agudeza visual inicial fue de 2.05 ± 0.99 logMAR y en la última visita, 0.82 ± 1.33. El tiempo de supervivencia del injerto fue de 130.34 meses. Se registraron cuatro fallas. En cuanto a las cirugías asociadas, antes del trasplante se registró cierre de herida corneal en siete ojos y durante la queratoplastia, vitrectomía anterior en dos ojos y después del trasplante, implante de válvula de Ahmed y resutura. Un total de ocho ojos tuvieron glaucoma, cinco con diagnóstico antes del trasplante. Respecto al rechazo, 15 ojos tuvieron un episodio durante el seguimiento y el tiempo promedio de rechazo al trasplante fue de 10.8 meses. CONCLUSIÓN: Se puede lograr una supervivencia prolongada del injerto con el mejor conocimiento y manejo de los diferentes factores asociados.

Natural history and predictors for progression in pediatric keratoconus.

We studied the demographic and clinical predictors associated with keratoconus progression in a pediatric population. Retrospective cohort study. We evaluated 305 eyes without previous surgeries from 168 patients, 9 to < 18 years old, and with a minimum 36-month follow-up in a hospital corneal ambulatory. We used Kaplan-Meyer survival curves; the dependent variable (main outcome measure) was the interval time (months) until the event, defined as an increase of 1.5 D in the maximum keratometry (Kmax), obtained with Pentacam. We evaluated the predictors: age (< or ≥ 14 years), sex, keratoconus familial history, allergy medical history, and the baseline tomographic parameters: mean keratometry (Km), Kmax (< or ≥ 55 D); and thinnest pachymetry (TP). We used log-rank tests and compared median survival times for right (RE)/left eyes (LE) and better (BE)/worse eyes (WE). A p value < 0.05 was considered significant. The patients' mean ± SD age was 15.1 ± 2.3 years old; 67% were boys, 30% were < 14 years, 15% had keratoconus familial history, and 70% were allergic. The general Kaplan-Meyer curves showed no differences between RE/LE or BE/WE. RE with allergy and LE with Kmax ≥ 55 D had smaller survival times ((95%CI 9.67-32.1), p 0.031 and (95%CI 10.1-44.1), p 0.042, respectively). For BE and WE, Kmax ≥ 55 D had smaller survival times ((95% CI 6.42- ), p 0.031 and (95%CI 8.75-31.8), p 0.043, respectively). Keratoconus progression was similar between RE/LE and BE/WE. Steepest corneas are predictors of faster progression. Allergy is also a predictor of keratoconus progression in RE.

Corneal ectasia detection by epithelial pattern standard deviation from OCT.

PURPOSE: To test the ability of the corneal epithelial pattern standard deviation (PSD) to distinguish between normal and cases with corneal ectatic condition. SETTING: Instituto de Olhos Renato Ambrósio, Rio de Janeiro, Brazil. DESIGN: Cross-sectional retrospective study. METHODS: Patients were stratified into 4 groups based on clinical data and corneal tomography. Groups 1 and 2 comprised 1 eye randomly selected from 105 patients with normal corneas (N) and 86 patients with bilateral keratoconus (KC). Groups 3 and 4, respectively, comprised 11 ectatic eyes with no surgical treatment for KC (very asymmetric ectasia [VAE]-E) from patients whose fellow eyes (61) presented with normal topographic patterns (VAE-NT). Corneas were scanned using an OCT system (RT Vue) and Scheimpflug corneal tomography (Pentacam) and also had biomechanical assessment through the Corvis ST. Corneal epithelial thickness maps were analyzed, and the PSD value was calculated. The area under the receiver operating characteristic curve analysis was used to evaluate the diagnostic accuracy of the indices. RESULTS: A total of 105 normal eyes, 86 keratoconic eyes, and 11 ectatic eyes whose fellow eyes (61) presented normal topographic patterns were evaluated. Epithelial PSD was significantly different across the 4 groups ( P < .0001). The pairwise comparison revealed that the normal group presented significantly lower values than both ectasia groups (KC and VAE-E, P < .0001) and the VAE-NT group ( P = .0008). There was no statistical significant difference between KC and VAE-E ( P = .4284), while they were significantly higher than the VAE-NT group ( P < .0001 and P = .0004). CONCLUSIONS: Epithelial PSD can be used to detect abnormal epithelial thickness patterns. Corneal epithelial thickness changes could be detected accurately in patients with KC, even in the form fruste of the disease.

Biomechanics in Keratoconus Diagnosis.

Purpose: To prospectively review the importance of biomechanical assessment in the screening, diagnosis, prognosis, individualized planning, and clinical follow-up for ectatic corneal diseases.Methods: We demonstrate two commercially available devices to assess the corneal biomechanics in vivo, the Ocular Response Analyzer (ORA, Reichester, NY, USA) and the Corvis ST (Oculus, Wetzlar, Germany). Novel devices have been demonstrated to provide in vivo biomechanical measurements, including Brillouin optical microscopy and OCT elastography. Conclusion: The integration of biomechanical data and other data from multimodal refractive imaging using artificial intelligence demonstrated the ability to enhance accuracy in diagnosing ectatic corneal diseases.

Avaliação das aberrações de alta ordem em pacientes com ceratocone inicial / Assessment of high-order aberrations in patients with early keratoconus

RESUMO Objetivo Identificar alterações de aberrometria de alta ordem em diferentes graus de ceratocone. Métodos Estudo transversal, retrospectivo, observacional. Foram analisados 54 pacientes (108 olhos) diagnosticados com ceratocone pelo mesmo especialista em córnea por meio dos critérios ABCD de Belin/Ambrósio Enhanced Ectasia, utilizando-se o tomógrafo Pentacam® HR 70900 (Oculus Wetzlar, Alemanha). Além disso, foram feitas análises qualitativa e quantitativa das aberrações de alta ordem desses mesmos pacientes por meio do OPD-Scan III-NIDEK. Resultados Por meio da avaliação de ambos os olhos dos pacientes com os critérios de Belin-Ambrósio, constatou-se presença de ceratocone em 34 pacientes. Ademais, por meio da análise estatística, constatou-se relação direta entre a asfericidade posterior e o desenvolvimento do ceratocone, com p<0,001 (referência: p<0,05). Por meio da análise do OPD-Scan III-NIDEK, as principais aberrações de alta ordem encontradas nos pacientes com ceratocone foram coma, trefoil e aberração esférica. Conclusão O raio da curvatura posterior é a primeira variável a se alterar com o desenvolvimento do ceratocone, o que se faz perceptível na análise da asfericidade posterior por meio o Pentacam®. Além disso, a alteração da paquimetria e da asfericidade posterior influencia diretamente o desenvolvimento de aberrações de alta ordem em pacientes com ceratocone.

ABSTRACT Objective To identify higher order aberrometry changes in different degrees of keratoconus. Methods Cross-sectional, retrospective, observational study. Fifty-four patients (108 eyes) diagnosed with keratoconus by the same corneal specialist using the Belin/Ambrósio Enhanced Ectasia ABCD criteria were analyzed, using the Pentacam® HR 70900 tomograph (Oculus Wetzlar, Germany). In addition, qualitative and quantitative analysis of higher order aberrations in these patients was performed using the OPD-Scan III-NIDEK. Results Through the evaluation of both eyes of the patients according to the criteria of Benin Ambrósio, the presence of KCN was verified in 34 patients. Furthermore, through statistical analysis, a direct relationship was found between posterior asphericity and the development of KCN; p<0.001 (reference: p<0.05). Through the analysis of the OPD scan, the main higher order aberrations found in patients with KCN were Coma, Trefoil and Spherical Aberration (AE). Conclusion The posterior curvature radius is the first variable to change with the development of the KCN, which is noticeable in the analysis of posterior asphericity in Pentacam. In addition, alterations in pachymetry and posterior asphericity directly influence the development of higher order aberrations in patients with KCN.

Characteristics of Higher-Order Aberrations in Different Stages of Keratoconus.

OBJECTIVES: To characterize higher-order aberrations (HOAs) in clinical and subclinical keratoconus (KC). METHODS: The study included 33, 36, and 26 patients with clinical, topographic (no clinical signs), and pretopographic (normal topography and no clinical signs) KC and 30 controls. Ocular and corneal HOAs for the 4-mm pupils were measured using a wavefront sensor and expanded up to the sixth order of Zernike polynomials. The magnitudes of trefoil, coma, tetrafoil, secondary astigmatism, and spherical aberration were calculated via Zernike vector analysis and used as HOA parameters along with total HOAs. Area under the receiver operating characteristic curve (AUROC) values for each wavefront parameter for pretopographic KC were compared. RESULTS: Control eyes and eyes with pretopographic KC had significantly lower ocular or corneal total HOAs and Zernike vector terms than those with clinical KC and topographic KC, except for ocular tetrafoil between topographic KC and pretopographic KC and spherical aberration among all groups. The AUROCs for corneal total HOAs and corneal coma for pretopographic KC and control eyes were 0.781 (100% sensitivity and 47% specificity) and 0.735 (73% sensitivity and 73% specificity), respectively. CONCLUSION: Corneal total HOAs and corneal coma exhibited a potential ability to discriminate pretopographic KC from normal control eyes.

Evaluation of corneal biomechanical behavior in vivo for healthy and keratoconic eyes using the stress-strain index.

PURPOSE: To evaluate the characteristics of corneal material properties in healthy individuals and keratoconic patients using the stress-strain index (SSI). SETTING: Vincieye Clinic in Milan, Italy, and Instituto de Olhos Renato Ambrósio in Rio de Janeiro, Brazil. DESIGN: Retrospective observational cross-sectional study. METHODS: Records of 1221 patients were divided into 3 groups: healthy corneas (n = 728), bilateral keratoconus (KC, n = 388), and very asymmetric ectasia (VAE, n = 105) when patients presented with clinical ectasia in 1 eye and normal topography (VAE-NT) in the fellow eye. All patients were examined with Pentacam HR and Corvis ST. Severity of KC cases was stratified according to the Pentacam topographic KC classification. The SSI distribution across the different groups and its correlation with age, biomechanically corrected intraocular pressure (bIOP), and central corneal thickness (CCT) were assessed. RESULTS: A statistically significant difference between healthy individuals and each of the keratoconic groups ( P < .001) was observed, and a progressive reduction in the SSI was observed across the groups. A significant correlation was observed between the SSI and age in all groups ( P < .010) but KC severe subgroup ( P = .361). No correlation between the SSI and bIOP and CCT was observed in all KC subgroups and VAE-NT groups ( P > .050). Among healthy eyes, there was only a mild correlation between the SSI and bIOP ( R = 0.12, P = .002) and CCT ( R = 0.13, P = .001). CONCLUSIONS: This study estimates the in vivo corneal material properties in healthy individuals and patients with KC using a new method. The SSI showed a progressive deterioration within the advance in disease stages while being relatively independent of bIOP and CCT but positively correlated with age.

Correlation between Placido-disc and rotating Scheimpflug keratometric findings before and after corneal crosslinking in children with keratoconus.

PURPOSE: To evaluate correlation between Placido-disc and rotating Scheimpflug keratometric findings in children with progressive keratoconus (KC) before and after corneal crosslinking (CXL) and investigate whether these limits of agreement varied according to disease severity. SETTING: Department of Ophthalmology of São Paulo Hospital, São Paulo, Brazil. DESIGN: Prospective nonrandomized open study. METHODS: Data obtained using rotating Scheimpflug-based tomography and Placido-disc-based topography devices were collected from preoperative and last follow-up postoperative children with KC operated on using standard CXL protocol. Correlation and agreement analyses were performed between the 2 devices before and after CXL to obtain keratometric (K) findings. RESULTS: 44 eyes from 44 patients aged 8 to 16 years were analyzed at all timepoints. All parameters were found to be strongly correlated before ( r = 0.84 to 0.99, P < .001) and after ( r = 0.93 to 0.99, P < .001) CXL. The mean Scheimpflug measurements of flat K, steep K, Kmax, mean K, and corneal astigmatism were higher than Placido-disc measurements in a preoperative period. This mean difference decreased in postoperative, but, with exception of Kmax and corneal astigmatism, Scheimpflug measurements remained higher. The mean parameter measurements from both devices decreased after CXL; 95% limits of agreement between instruments were wide for all parameters and decreased in postoperative and in mild KC. CONCLUSIONS: Keratometry measurements obtained using rotating Scheimpflug and Placido-disc technology were found to be closely correlated but not interchangeable before and after CXL in pediatric patients. Agreement between devices was better after CXL and in mild KC than in advanced KC.

Correction methods for noncontact intraocular pressure measurement in patients with keratoconus and healthy individuals.

PURPOSE: The objective of this study was to investigate the usefulness of four different algorithms to correct noncontact intraocular pressure measurement errors in keratoconus patients and normal individuals. METHODS: Noncorrected intraocular pressure and corrected intraocular pressures were measured in one eye of 34 patients with keratoconus and 34 age- and gender-matched healthy controls using Corvis Scheimpflug Technology. The correlation of noncorrected intraocular pressure and corrected intraocular pressures with age, axial length, corneal shape, thickness, and biomechanics was calculated. Corrected intraocular pressures were compared with noncorrected intraocular pressure using paired t test and Bland-Altman plots (95% limits of agreement). RESULTS: The noncorrected intraocular pressure correlated with corneal thickness and biomechanical parameters in both groups (all p≤0.047), and front and back mean keratometry in the keratoconus group (r=-0.39, p=0.02, and r=0.39, p=0.02, respectively). After adjustment with different intraocular pressure correction algorithms, biomechanically corrected intraocular pressure showed a minimal correlation with corneal features and a nonsignificant difference with noncorrected intraocular pressure in the healthy group (-0.1 ± 1.1 mmHg, p=0.58; 95% limits of agreement: -2.3 to 2.1 mmHg). CONCLUSIONS: Measuring intraocular pressure using noncontact tonometry and its corrected forms with a corneal thickness-based simple linear formula in patients with keratoconus is associated with many errors. Using more complex formulas that take into consideration more corneal stiffness parameters in addition to corneal thickness, such as biomechanically corrected intraocular pressure formula, may be more reliable and beneficial in this group of patients.

Absence of significant genetic alterations in the VSX1, SOD1, TIMP3, and LOX genes in Brazilian patients with Keratoconus.

PURPOSE: To identify inherited or acquired mutations in the VSX1, SOD1, TIMP3 and LOX genes from the combined analysis of corneal and blood samples from patients with Keratoconus. METHODS: The casuistry was consisted of samples of peripheral blood and corneal epithelium from 35 unrelated patients with Keratoconus who were submitted to corneal crosslink treatment. Also, blood and corneal epithelium samples from 89 non-keratoconic patients were used to compose the control group. Ophthalmologic evaluations included a clinical examination, topography and tomography. DNA samples were extracted from peripheral blood and from corneal epithelium in both groups and all coding regions of the VSX1, SOD1, TIMP3 and LOX genes were amplified by polymerase chain reaction, denatured and subjected to polyacrylamide gel electrophoresis. Mutational screening was performed by single-strand conformation polymorphism and direct DNA sequencing. RESULTS: No pathogenic variant was found in all coding regions of VSX1, SOD1, TIMP3 and LOX genes, we detected only few SNPs (single-nucleotide polymorphisms). Among the polymorphisms stand out three of them, corresponding to the synonymous exchange of amino acids: exon 3 of VSX1 Ala182Ala and exon 3 of TIMP3 His83His and Ser87Ser; in patients with Keratoconus and also in control subjects. All the polymorphisms were found in samples of corneal epithelium and corresponding blood. CONCLUSION: There is absence of KC pathogenic related to mutations in the VSX1, SOD1, TIMP3 and LOX genes in the studied patients.