Online survey about keratoconus management by optometrists.

Purpose: The aim of the study was to survey keratoconus management by optometrists in India. Methods: A validated online survey questionnaire was circulated to all optometrists from India who had completed 4 years of optometry programs. Practitioners were asked general contact lens practice questions and keratoconus management-related questions. For analysis, data were imported into SPSS (IBM Corp. 2011). Results: A total of 159 optometrists responded to the questionnaire, of whom 10.7% of practitioners had >10 years of experience and the remaining 89.3% had <10 years. Only 45.3% of respondents had corneal topography in their practice. Approximately 55% of practitioners prescribed gas permeable (GP) lenses. Around 77.4% of practitioners considered that a combination of multiple factors is necessary for keratoconus investigations. In addition, 91.8% of practitioners used the keratoconus severity classification. Also, 73% of practitioners consider that GP contact lens (CL) fitting is more difficult in keratoconic eyes than in healthy eyes. The average number of GP diagnostic lenses used in keratoconus CL fittings was 3.93 ± 1.92. A majority of practitioners calculate back optic zone radius (BOZR) using the manufacturer's guidelines (based on manual keratometry [39.6%] or based on corneal topography [40.3%]). Around 40.3% of respondents prefer to refer patients to another optometrist for CL fitting before consulting an ophthalmologist for surgical intervention. Finally, half of the respondents participate in co-management with ophthalmologists after surgical treatment (54.1%). Conclusion: This study provides details about the management of keratoconus by optometrists in India. Keratoconus patient care could be improved with new evidence-based guidelines for the management and referral of these patients that would provide guidance on GP CL fitting procedures. Furthermore, it determines referral criteria and enhances co-management between optometrists and ophthalmologists.

The effect of smoking on corneal densitometry and endothelial cell morphology.

PURPOSE: We investigated corneal endothelial morphology and corneal densitometry in smokers and compared our results with findings observed in non-smokers. MATERIALS AND METHODS: This cross-sectional observational study included 100 participants (50 smokers, 50 non-smokers) aged 18-80 years in whom corneal endothelial morphology was analysed using a non-contact Tomey EM-4000 specular microscope (Tomey Corporation, Japan). The Pentacam HR system was used to measure corneal densitometry spatially in three concentric zones (from the centre to the periphery) and at three different corneal depths (from the anterior to the posterior aspects). Endothelial morphology findings and corneal densitometry values were recorded in all participants, and these results were compared between smokers and non-smokers. RESULTS: Endothelial morphology and corneal densitometry analysis showed significantly lower endothelial cell counts (Num) in smokers (228 cells/mm2 vs. 246 cells/mm2, p = 0.02) in addition to increased maximum cell area (Max) values (986.5 µm2 vs. 935 µm2, p = 0.04). We observed no statistically significant intergroup difference in corneal densitometry values (p > 0.05 for each zone); however, we observed a moderately positive correlation between densitometry values in the 6-10 mm concentric zone and between the all total corneal zones and number of pack-years in smokers. CONCLUSIONS: Our study highlights that among the morphometric corneal endothelial variables analysed in this study, only the Num value was significantly correlated with smoking. We observed no statistically significant intergroup difference in corneal densitometry values in this study; however, a positive correlation was observed between the number of pack-years and corneal densitometry findings. Therefore, as the pack-years increase, the increase in corneal densitometry values may indicate a decrease in corneal clarity, considering the possible contribution of secondary factors such as age.

The contribution of ocular residual astigmatism to anterior corneal astigmatism in refractive astigmatism eyes.

To determine the distribution of ocular residual astigmatism (ORA) in astigmatic eyes and the influence on the anterior corneal (ACA) and refractive astigmatism (RA). A total of 165 children met the inclusion criteria. Right eyes' data were analyzed. Using Thibos vector analysis to calculate ORA. Spearman correlation analysis was used to obtain the correlation between the magnitude of ORA, ACA and RA. The median magnitude of ORA in astigmatic eyes was 0.57 D, with interquartile range was 0.42 D. And they were main against-the-rule (57.6-75.8%) and oblique astigmatism (13.9-34.5%) ORA. The ORA in 140 eyes (84.8%) acted as an offset to ACA, meanwhile, 25 eyes (15.2%) superimposed it. About 98% (97.9-98.4%) against-the-rule and 75% (73.9-82.5%) oblique ORA counteracted ACA, nevertheless, all with-the-rule ORA had a superimposed effect on ACA. For with-the-rule ACA, about 86% (85.4-85.9%) ORA worked to offset it. There was statistically correlations between ORA and ACA (r = 0.17, P = 0.03), ORA and RA (r = - 0.27, P = 0.001). The magnitude of ocular residual astigmatism was relatively small in children's astigmatic eyes. Both against-the-rule and oblique ORA can counteract with-the-rule ACA.

[Corneal topography in practice]. / Topographie cornéenne en pratique.

Corneal surface analysis is now more and more accurate. Corneal topography is a gold standard in corneal pathology follow-up: keratoconus, corneal grafts, orthokeratology. In refractive surgery, cornea ectasia post-Lasik must be avoided. Analyzing anterior and posterior surface can detect forme fruste keratoconus FFKC. Topography allows also better predictability of premium intraocular implants surgery. Topography is key examination and its interpretation is essential.

[Distribution of corneal thickness in the Tunisian population: Study by anterior segment optical coherence tomography]. / Distribution de l'épaisseur cornéenne centrale dans la population tunisienne : étude par tomographie en cohérence optique du segment antérieur.

GOALS: To describe the distribution of the central corneal thickness (CCT) in the Tunisian population. METHODS: A prospective descriptive study was performed in 201 right eyes of 201 randomly selected healthy Tunisian subjects without glaucoma. We measured the spherical error by autorefraction, the axial length using A-scan ultrasound biometry and the central corneal thickness using anterior segment optical coherence tomography (DRI TRITON OCT). RESULTS: We examined 201 eyes. The mean age was 47±13.5 years (18 to 77 years). The M/F sex ratio was at 0.46 (137 women and 64 men). The mean CCT was 508,1µm (standard deviation 31,5µm) and ranged from 440 to 600µm. In our population 43.8% had a CCT less than 500µm, and 89.1% had a CCT less than 550µm. No statistically significant correlation was observed between CCT and age, sex, spherical error or axial length. CONCLUSION: Central corneal thickness in the Caucasian Tunisian population is less than CCT in the European and Asian populations. CCT is independent of age, sex, spherical error or axial length. These results must be confirmed by larger multicentric studies.

Repeatability of automatic measurements by a new anterior segment optical coherence tomographer combined with Placido topography and agreement with 2 Scheimpflug cameras.

PURPOSE: To evaluate the repeatability of automatic measurements by a new anterior segment optical coherence tomographer (AS-OCT) combined with Placido topography and their agreement with those provided by 2 rotating Scheimpflug cameras. SETTING: G.B. Bietti Foundation IRCCS, Rome, Italy. DESIGN: Evaluation of a diagnostic test instrument. METHODS: Unoperated eyes and eyes with previous myopic excimer laser surgery were analyzed. Three consecutive scans were acquired with an AS-OCT device (MS-39) and 1 with 2 rotating Scheimpflug cameras (Pentacam HR and Sirius). The following parameters were evaluated: simulated keratometry, posterior and total corneal power, total corneal astigmatism, corneal asphericity, thinnest corneal thickness, central epithelial thickness, corneal diameter, and aqueous depth. Repeatability was assessed using test-retest variability, the coefficient of variation (CoV), and the intraclass correlation coefficient; agreement was assessed by the 95% limits of agreement. RESULTS: The study comprised 96 unoperated eyes and 43 eyes with previous myopic excimer laser surgery. High repeatability was achieved in both groups, as shown by a CoV less than 1.0% for most parameters. The repeatability of epithelial thickness was slightly lower than that of the whole corneal thickness, although the CoV was still good (1.87% in unoperated eyes; 3.28% in post-refractive surgery eyes). Moderate repeatability was found for total corneal astigmatism measurements, with a CoV greater than 20.0%. Agreement with Scheimpflug cameras was high for aqueous depth and thinnest corneal thickness and moderate for most other parameters. CONCLUSION: The high repeatability of automatic measurements by the new AS-OCT device supports its use in clinical practice.

Validation of Fourier analysis of videokeratographic data.

PURPOSE: The aim was to assess the repeatability of Fourier transfom analysis of videokeratographic data using Pentacam in normal (CG), keratoconic (KC) and post-CXL (CXL) corneas. METHODS: This was a prospective, clinic-based, observational study. One randomly selected eye from all study participants was included in the analysis: 62 normal eyes (CG group), 33 keratoconus eyes (KC group), while 34 eyes, which had already received CXL treatment, formed the CXL group. Fourier analysis of keratometric data were obtained using Pentacam, by two different operators within each of two sessions. Precision, repeatability and Intraclass Correlation Coefficient (ICC), were calculated for evaluating intrassesion and intersession repeatability for the following parameters: Spherical Component (SphRmin, SphEcc), Maximum Decentration (Max Dec), Regular Astigmatism, and Irregularitiy (Irr). Bland-Altman analysis was used for assessing interobserver repeatability. RESULTS: All parameters were presented to be repeatable, reliable and reproductible in all groups. Best intrasession and intersession repeatability and reliability were detected for parameters SphRmin, SphEcc and Max Dec parameters for both operators using ICC (intrasession: ICC > 98%, intersession: ICC > 94.7%) and within subject standard deviation. Best precision and lowest range of agreement was found for the SphRmin parameter (CG: 0.05, KC: 0.16, and CXL: 0.2) in all groups, while the lowest repeatability, reliability and reproducibility was detected for the Irr parameter. CONCLUSIONS: The Pentacam system provides accurate measurements of Fourier tranform keratometric data. A single Pentacam scan will be sufficient for most clinical applications.

Interaction between Corneal and Internal Ocular Aberrations Induced by Orthokeratology and Its Influential Factors.

PURPOSE: To investigate the interaction between corneal, internal, and total wavefront aberrations (WAs) and their influential factors during orthokeratology (OK) treatment in Chinese adolescents. METHODS: Thirty teenagers (n = 30 eyes) were enrolled in the study; spherical equivalent refraction (SE), corneal curvature radius (CCR), central corneal thickness (CCT), WAs, and the difference in limbal transverse diameter and OK lens diameter (ΔLLD) were detected before and after one-month OK treatment. Every component of WAs was measured simultaneously by iTrace aberrometer. The influential factors of OK-induced WAs were analyzed. RESULTS: SE and CCT decreased while CCR increased significantly (P < 0.01). Higher-order aberrations (HOAs), Spherical aberrations (SAs), and coma increased significantly (P < 0.01). Corneal horizontal coma (Z31-C) and corneal spherical aberrations (Z40-C) increased (P < 0.01). The HOAs, coma, SAs, Z31-C, Z31-T, Z40-C, and Z40-T were positively correlated with SE and CCR (P < 0.01). Z3-1-C showed negative correlations with (ΔLLD) and positive correlations with SE (P < 0.05). CONCLUSIONS: The increase in OK-induced HOAs is mainly attributed to Z31 and Z40 of cornea. Z3-1 in the internal component showed a compensative effect on the corneal vertical coma. The degree of myopic correction and increase in CCR may be the essential influential factors of the increase in Z31 and Z40. The appropriate size of the OK lens may be helpful to decrease OK-induced vertical coma.

Topographic outcomes after corneal collagen crosslinking in progressive keratoconus: 1-year follow-up.

PURPOSE:: We aimed to report and analyze topographic and refractive outcomes following corneal collagen crosslinking (CXL) in patients with progressive keratoconus (KC). METHODS:: We performed a retrospective, analytical, and observational study of 100 eyes from 74 progressive KC patients who underwent CXL at the Eye Hospital of Paraná. Keratometric values were analyzed preoperatively as well as 3 and 12 months postoperatively. RESULTS:: For a total of 100 eyes, 68 belonged to male patients. The mean age of our study population was 19.9 ± 5.61 years. The average visual acuity and topographic parameters overall were stable after 1 year (p<0.05). After 3 months, steepest keratometry reading (K2) and maximum keratometry (Kmax) were significantly decreased (p<0.05). Regarding topographic astigmatism (dK), there was no significant difference between the 3-month and 12-month follow-ups. When we made comparisons between genders following CXL, there were no significant differences related to the changes in Kmax, K2, and spectacle-corrected distance visual acuity (SCDVA). CONCLUSIONS:: CXL promoted stabilization or improvement of keratometric values and visual acuity. We found that keratoconus apex stability may be achieved 3 months after the procedure. There was no significant difference in keratometric and refractive values measured between male and female patients.

Evaluation of Goldmann applanation tonometry, rebound tonometry and dynamic contour tonometry in keratoconus / Evaluación del tonómetro de aplanamiento de Goldmann, el tonómetro de rebote y el tonómetro de contorno dinámico en los casos de queratocono

Purpose: To compare the intraocular pressure (IOP) measurements obtained with the rebound tonometry (RT), dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) in keratoconic corneas and to investigate the effects of central corneal thickness (CCT) and corneal radius of curvature (CR) on IOP measurements. Methods: Sixty-three eyes of 63 keratoconus patients were enrolled in this cross-sectional study. IOP was measured on each subject always in the same order, ICare RT-Pascal DCT-GAT, after a minimum interval of 10min between measurements. CCT and CR were measured using a rotating Scheimpflug camera before the IOP measurements in all subjects. One way repeated measures ANOVA and Pearson correlation coefficient analysis was used for the statistical assessment. Results: Mean IOP for all enrolled eyes was 11.72±2.59mmHg for GAT, 9.34±3.29mmHg for RT, and 15.42±3.31mmHg for DCT. There were statistically significant differences among the three tonometers; GAT and RT (P<0.001), GAT and DCT (P<0.001), and RT and DCT (P<0.001). GAT and RT were significantly positively correlated with CCT (r=0.288, P=0.025 and r=0.483, P<0.001, respectively). RT was also significantly positively correlated with CR (r=0.550, P<0.001). DCT was not significantly correlated with CCT (r=0.115, P=0.377) nor CR (r=−0.179, P=0.168). Conclusions: DCT has overestimated but RT has underestimated IOP readings according to GAT measurements in keratoconic corneas. DCT may be the most appropriate tonometer to use in keratoconus for the measurements of IOP, because DCT do not appear to be dependent upon CCT and CR (AU)

Objetivo: Comparar las mediciones de la presión intraocular (PIO) obtenidas con el tonómetro de rebote (RT), el tonómetro de contorno dinámico (DCT) y el tonómetro de aplanamiento de Goldmann (GAT) en córneas con queratocono, e investigar los efectos del espesor central de la córnea (CCT) y los radios de curvatura de la córnea (CR) en las mediciones de la PIO. Métodos: Este estudio transversal se realizó sobre sesenta y tres ojos de un número igual de pacientes con queratocono. Se midió la PIO de cada sujeto siempre en el mismo orden, ICare RT-Pascal DCT-GAT, tras un intervalo mínimo de diez minutos entre mediciones. Las mediciones de CCT y CR se realizaron utilizando una cámara Scheimpflug rotatoria, antes de medir la PIO en todos los sujetos. Se utilizaron los análisis de coeficiente de correlación de Pearson y la ANOVA de una vía de medidas repetidas para realizar la valoración estadística. Resultados: La PIO media para todos los ojos estudiados fue de 11,72±2,59mmHg para GAT, 9,34±3,29mmHg para RT, y 15,42±3,31mmHg para DCT. Se produjeron diferencias estadísticamente significativas entre los tres tonómetros; GAT y RT (P<0,001), GAT y DCT (P<0,001), RT y DCT (P<0,001). GAT y RT reflejaron una relación significativamente positiva con CCT (r=0,288, P=0,025 y r=0,483, P<0,001, respectivamente). RT reflejó también una correlación significativamente positiva con CR (r=0,550, P<0,001). DCT no reflejó una correlación significativa con CCT (r=0,115, P=0,377) ni con CR (r=0,179, P=0,168). Conclusiones: El tonómetro DCT sobreestimó las mediciones de la PIO, y el RT subestimó las mismas, con arreglo a las mediciones de GAT en las córneas con queratocono. DCT ha demostrado ser el tonómetro más adecuado para utilizar en las mediciones de la PIO en los casos de queratocono, ya que no parece depender de CCT y CR (AU)

Topographic outcomes after corneal collagen crosslinking in progressive keratoconus: 1-year follow-up / Resultados topográficos após crosslinking de colágeno corneano em ceratocone progressivo: 1 ano de seguimento

ABSTRACT Purpose: We aimed to report and analyze topographic and refractive outcomes following corneal collagen crosslinking (CXL) in patients with progressive keratoconus (KC). Methods: We performed a retrospective, analytical, and observational study of 100 eyes from 74 progressive KC patients who underwent CXL at the Eye Hospital of Paraná. Keratometric values were analyzed preoperatively as well as 3 and 12 months postoperatively. Results: For a total of 100 eyes, 68 belonged to male patients. The mean age of our study population was 19.9 ± 5.61 years. The average visual acuity and topographic parameters overall were stable after 1 year (p<0.05). After 3 months, steepest keratometry reading (K2) and maximum keratometry (Kmax) were significantly decreased (p<0.05). Regarding topographic astigmatism (dK), there was no significant difference between the 3-month and 12-month follow-ups. When we made comparisons between genders following CXL, there were no significant differences related to the changes in Kmax, K2, and spectacle-corrected distance visual acuity (SCDVA). Conclusions: CXL promoted stabilization or improvement of keratometric values and visual acuity. We found that keratoconus apex stability may be achieved 3 months after the procedure. There was no significant difference in keratometric and refractive values measured between male and female patients.

RESUMO Objetivos: Relatar e analisar os resultados topográficos e refracionais após crosslinking de colágeno corneano (CXL) em pacientes com ceratocone (KC) progressivo. Métodos: Estudo retrospectivo analítico e observacional incluindo 100 olhos de 74 pacientes com KC progressivo submetidos a CXL no Hospital de Olhos do Paraná. Valores ceratométricos foram analisados no pré-operatório, 3 e 12 meses de pós-operatório. Resultados: Em um total de 100 olhos, 68 eram do sexo masculino. A idade média foi de 19,9 ± 5,61. As médias de parâmetros topográficos e acuidade visual em geral, tiveram estabilidade após 1 ano de follow-up (p<0,05). Após 3 meses, a ceratometria mais curva (K2) e a ceratometria máxima (Kmax) tiveram reduções estatisticamente significativas (p<0,05). Em relação ao astigmatismo topográfico (dK), não houve diferença estatisticamente significativa aos 3 e 12 meses de seguimento. Comparando ambos os sexos após o procedimento, não houve diferenças estatisticamente significativas relacionadas às mudanças em Kmax, K2 e acuidade visual corrigida. Conclusões: CXL promoveu a estabilidade ou melhora dos valores ceratométricos e da acuidade visual. Encontramos que a estabilidade do ápice do KC pode ser obtida nos três primeiros meses de follow-up. Não houve diferença estatisticamente significativa nos valores topográficos e refracionais medidos entre pacientes do sexo masculino e feminino.

Repeatability and Agreement of Orbscan II, Pentacam HR, and Galilei Tomography Systems in Corneas With Keratoconus.

PURPOSE: To assess the repeatability and agreement of keratometry and pachymetry measurements obtained using 3 tomographers in eyes with keratoconus. DESIGN: Reliability analysis. METHODS: setting: Institutional. STUDY POPULATION: Fifty eyes of 50 participants with keratoconus. observational procedure: Steep keratometry, flat keratometry, central corneal thickness (CCT), and thinnest corneal thickness (TCT) measurements using Galilei, Orbscan II, and Pentacam HR. MAIN OUTCOME MEASURES: Repeatability was assessed using within-subject standard deviation (SW), coefficient of variation (CV), and intraclass correlation coefficient (ICC). Bland-Altman plots and 95% limits of agreement (LoA) were used to evaluate agreement between device pairs. RESULTS: For all studied parameters, ICC was >0.97 with the least repeatable measurements obtained using Orbscan II. Mean steep keratometry values were similar while mean flat keratometry values were significantly different between all devices. The Galilei and Pentacam HR had the lowest 95% LoA for both CCT and TCT. There were no significant differences in mean CCT between Galilei and Pentacam HR. Mean Orbscan II CCT measurements were not significantly different overall but had wide 95% LoA with Pentacam HR (-47.95 to 58.09 µm) and Galilei (-43.70 to 53.91 µm). Mean Orbscan II CCT measurements were significantly lower when an acoustic factor of 0.92 was applied (-33.6 µm vs Pentacam HR, P < .001; -33.6 µm vs Galilei; P < .001). CONCLUSIONS: Keratometric and pachymetric measurements of keratoconic eyes obtained by Galilei, Orbscan II, and Pentacam were disparate. Measurements were less repeatable with Orbscan II compared with Pentacam HR and Galilei, although overall repeatability was high for all instruments.

Imágenes Scheimpflug útiles en el diagnóstico de desprendimiento de la membrana de Descemet / Useful Scheimpflug images for the diagnosis of Descemet membrane detachment

El desprendimiento de la membrana de Descemet es una complicación infrecuente de la cirugía intraocular que puede resultar devastadora si no se diagnostica y se trata a tiempo. Habitualmente está asociado a la cirugía de la catarata, aunque tiene múltiples etiologías. Existen tratamientos muy variados, desde la simple observación hasta la queratoplastia penetrante. Se presenta una paciente femenina de 66 años de edad, con antecedentes de salud, quien fue operada de catarata del ojo derecho por la técnica de facoemulsificación con implante de lente intraocular de cámara posterior sin complicaciones aparentes durante la cirugía. En el posoperatorio presentó a las 24 horas edema corneal tres cruces con tensión ocular normal, el cual se mantuvo durante la primera semana a pesar del tratamiento intensivo con cloruro de sodio hipertónico y antinflamatorios esteroideos. No se recogieron alteraciones del endotelio corneal previas a la cirugía. En las imágenes de Scheimpflug del pentacam se observó desprendimiento de la membrana de Descemet en distintos puntos. Se realizó neumopexia y a las 24 horas la córnea se encontraba transparente(AU)

Descemet´s membrane detachment is an uncommon complication of the intraocular surgery that can be devastating if it is not diagnosed and treated on time. It is usually associated to cataract surgery, although has multiple etiologies. Treatments vary from the simple observation to the penetrating keratoplasty. This is the case of a 66 year-old woman, with a history of health problems, who was operated on of cataract in her right eye through the phacoemulsification technique with posterior chamber intraocular lens implantation without apparent complications during surgery. After 24 hours, she presented with corneal edema, three crosses and normal ocular pressure. She remained with the same condition during the first week despite treatment with hypertonic sodium chloride and steroid anti-inflammatory drugs. There were no alterations in the corneal endothelium before surgery. Scheimpflug images in Pentacam showed Descemet´s membrane detachment in several sites. It was decided to apply pneumopexia which rendered transparent cornea after other 24 hours(AU)

Intraobserver repeatability and interobserver reproducibility of corneal measurements in normal eyes using an optical coherence tomography-Placido disk device.

PURPOSE: To study intraobserver and interobserver reproducibility of corneal topography and aberrometry measurements using a device combining optical coherence tomography (OCT) and a Placido disk (Visante Omni). SETTING: Singapore National Eye Centre, Singapore. DESIGN: Prospective nonrandomized study. METHOD: Measurements of simulated keratometry (K), anterior mean curvature, spherical anterior and posterior elevations, 4.5 mm diameter zone aberrometry (spherical aberration, asphericity, astigmatism), pachymetry, and white-to-white (WTW) diameter were taken in normal right eyes. Mean biases and limits of agreement (LoA) were obtained using Bland-Altman analysis. RESULTS: Regarding intraobserver repeatability, the mean biases for simulated K, anterior mean curvature, spherical anterior/posterior elevation, 4.5 mm zone aberrometry, pachymetry, and WTW diameter were not statistically significant (P > .05). The LoA for the anterior mean curvature measurements were flat K, -3.96 diopters (D) and 4.86 D; steep K, -4.50 D and 4.27 D; mean K, -2.48 D and 2.09 D. The LoA for WTW were -9.90 mm and 8.74 mm. Regarding interobserver reproducibility, the mean biases for simulated K, anterior mean curvature, spherical anterior/posterior elevation, 4.5 mm zone aberrometry, pachymetry, and WTW diameter were not statistically significant (P > .05). The LoA for anterior mean curvature were flat K, -4.05 D and 4.13 D; steep K, -5.08 D and 3.85 D; mean K, -2.65 D and 2.29 D. The LoA for WTW diameter were -8.79 mm and 8.24 mm. CONCLUSIONS: The OCT-Placido device had high intraobserver and interobserver clinical reproducibility for measurements of simulated K, 4.5 mm zone aberrometry, pachymetry, and standard anterior/posterior corneal elevation. However, intraobserver and interobserver reproducibility of anterior mean curvature measurements and WTW diameter was lower. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Diagnóstico del queratocono subclínico por topografía de elevación / Diagnosis of the subclinical keratoconus through elevation topography

OBJETIVO: definir parámetros más eficaces de la topografía de elevación para la detección del queratocono subclínico. MÉTODOs: se estudiaron con topografía Galilei las córneas de 15 pacientes con diagnóstico clínico de queratocono (grupo 1: n = 23 ojos), de 12 pacientes con queratocono subclínico diagnosticados por topografía de elevación (grupo 2: n = 18) y un grupo control de 13 pacientes miopes distribuidos por sexo, edad y equivalente esférico refractivo (grupo 3: n = 25). Se analizaron los siguientes parámetros: localización del ápex, elevación de las caras anterior y posterior de la córnea, paquimetría mínima y profundidad de cámara anterior. RESULTADOS: la ubicación más frecuente del ápex fue en el sector inferotemporal (52,1 %). El promedio de máxima elevación de la cara anterior fue 40,83 ± 17,75 mm en el grupo 1 y de 16,89 ± 8,22 mm en el grupo 2, donde ambos fueron significativamente diferentes al grupo control (p < 0,02). El promedio de la máxima elevación de la cara posterior fue 73,35 ± 17,73 mm en el grupo 1 y 41,22 ± 9,94 mm en el grupo 2. Ambos resultados fueron significativamente diferentes al grupo control (p < 0,00). El mínimo espesor y la profundidad de cámara anterior también mostraron diferencias estadísticamente significativas entre los grupos estudiados. CONCLUSIONES: los parámetros de elevación de cara anterior, posterior, paquimetría y profundidad de cámara anterior, medidos en la topografía de elevación con Galilei, difieren significativamente entre individuos normales y con queratocono clínico y subclínico.

OBJECTIVE: to define the most effective parameters of corneal elevation topography for subclinical keratoconus screening. METHODS: Galilei topography system-based study included corneas from 15 patients with clinical diagnosis of keratoconus (group 1, n = 23 eyes), from 12 patients with subclinical keratoconus (group 2, n = 18 eyes) and a control group of 13 myopic subjects paired in gender, age and refractive spherical equivalent (group 3, n = 25). The following parameters were analyzed: location of the apex, anterior and posterior corneal elevation, minimal pachyimetry and anterior chamber depth. RESULTS: the most frequent location of the apex was at the inferotemporal sector (52 %). Mean anterior maximum elevation was 40,83 ± 17,75 mm in group 1 and 16,89 ± 8,22 mm in group 2; these results were significantly different from the control group (p < 0,02). Mean posterior maximum elevation was 73,35 ± 17,73 mm in group 1 and 41,22 ± 9,94 mm in group 2, both showing a statistically significant difference from that of the control group (p < 0,00). Minimal corneal thickness and anterior chamber depth also showed statistically significant differences among the three groups. CONCLUSIONS: statistically significant differences were found in anterior and posterior elevation, minimal corneal thickness and anterior chamber depth parameters, as measured by the Galilei system, between the normal myopic subjects, and those with clinical and subclinical keratoconus.

[Difference and distance between the central and thinnest points of the cornea: impact of refractive state, age and ocular side]. / Differenz und Entfernung zwischen zentraler und dünnster Stelle der Hornhaut: Einfluss von Refraktion, Alter und Augenseite.

BACKGROUND: The aim of the study was to quantify the difference in corneal thickness between the central and thinnest points (∆PachyZ-PachyD), the distance between the center of the cornea and its thinnest point (vector length PachyD) and to explore the impact of refractive state, age and ocular side. PATIENTS AND METHODS: This was a multicenter, retrospective, cross-sectional study and medical records of 16,872 eyes were reviewed. The Orbscan® (Bausch and Lomb) procedure was used for pachymetry and keratometry. RESULTS: The results showed that ∆PachyZ-PachyD and vector length PachyD were higher in hyperopic eyes (∆PachyZ-PachyD: 11.99 ± 12.08 µm, vector length PachyD: 0.85 ± 0.44 mm) compared to myopic eyes (∆PachyZ-PachyD: 9.2 ± 7.86 µm, vector length PachyD: 0.7 ± 0.37 mm; p < 0.001). Refractive state, age and ocular side demonstrated an independent, statistically significant impact on ∆PachyZ-PachyD and vector length PachyD. CONCLUSIONS: As a result of the significant impact of refractive state, age and ocular side on ∆PachyZ-PachyD and vector length PachyD, these variables should be considered in a normative data collection.

Evaluation of central corneal thickness after cataract surgery, penetrating keratoplasty and long-term soft contact lens wear.

PURPOSE: The aim of this study was to compare central corneal thickness (CCT) between corneas of normal healthy eyes (cNHE), corneas of eyes that had undergone cataract surgery by clear corneal phacoemulsification with implantation of an intracapsular intraocular lens (cIOL), corneal grafts after penetrating keratoplasty (gPK) and corneas of long-term soft contact lens wearers (cCL). METHODS: The study design was a consecutive cross-sectional trial. CCT was measured using rotating Scheimpflug camera (Pentacam, software version 1.16r04) in 80 cNHE, 79 cIOL, 46 gPK and 78 cCL. Analysis of variance (one-way ANOVA) was performed to compare differences of mean values between these four groups. Pearson's or Spearman's correlation coefficient (r) was determined between CCT value and age, follow up time after penetrating keratoplasty (timePK) or contact lens wearing time (timeCL). RESULTS: Means of CCT measurements were comparable between cNHE (mean CCT±standard deviation, 554±36µm), cIOL (551±40µm) and gPK (534±52µm) as determined by one-way ANOVA. Mean CCT values in cCL (537±37µm) were statistically significantly lower in comparison to cNHE (p=0.026, 95% CI=1.43-31.44). There was no linear correlation between age and CCT values of cNHE and cIOL (p=0.841, r=-0.031 and p=0.931, r=0.011, respectively). No linear relationship was determined between CCT values of cCL and timeCL (p=0.315, r=-0.125). CCT values of gPK did not correlate with timePK (p=0.738, r=0.054). CONCLUSIONS: The data reported here indicate that in the same statistical model among CCT values of cNHE, cIOL and gPK only long-term soft contact lenses (CL) wearer have significantly lower CCT measurements.

Distribution of radii of curvature of anterior and posterior best fit sphere in a normal population: the Tehran Eye Study.

PURPOSE: To determine the distribution and determinants of the radii of curvature of the anterior and posterior best fit spheres (ABFS and PBFS) of the cornea in a sample from the general normal population of Tehran. METHODS: A stratified random cluster sampling was used to select samples from the first 4 districts of Tehran proportionate to the population of each stratum. We examined the distribution of the ABFS and PBFS, as measured with the Orbscan II in different groups of age, sex, and refractive error, and determined their relationship with other variables by using both univariate and multiple regression analyses. Valid data was collected from 800 eyes, and analyses were done with data from 399 right eyes only. RESULTS: Mean ABFS and PBFS in the studied sample were 43.31±1.79D and 52.67±3.04D, respectively. ABFS increased with age while PBFS showed no significant association; both showed significant inter-sex differences. In the multiple linear regression model, both ABFS and PBFS significantly correlated directly with age and average keratometry, and inversely with corneal diameter; PBFS correlated directly with anterior chamber depth as well. Mean PBFS/ABFS ratio was 1.22±0.05 which significantly decreased with age and was significantly higher in females. CONCLUSION: Knowledge of normal ranges of ABFS and PBFS and their determinants, including age, mean keratometry, and corneal diameter, as well as the choice of measurement device, is necessary for comparing information from different populations and interpreting results.

Anterior segment characteristics of keratoconus eyes in a sample of Asian population.

PURPOSE: To assess changes in anterior segment parameters of keratoconus eyes at different stages of the disease in a sample of the Asian population. METHODS: Files of 32 patients (48 eyes) diagnosed as clinical keratoconus were assessed and the following parameters noted: central corneal thickness (CCT), thinnest corneal thickness (TCT), location of thinnest pachymetry, anterior chamber depth (ACD) at the centre from posterior corneal surface, ACD at 1, 2 and 3mm inferior-paracentral, ACD at thinnest pachymetry, anterior chamber volume (ACV) and anterior chamber angle (ACA). For analysis, keratoconus eyes were classified into 3 subgroups according to mean keratometry readings (mild: K≤47.0D, moderate: 47.0

Evaluation of the consistency of total spherical aberration before and after aspherical intraocular lens implantation.

PURPOSE: To analyze the consistency between preoperatively estimated and postoperatively measured total spherical aberration and to evaluate the feasibility of personalized selection of an aspherical intraocular lens (IOL) based on the corneal spherical aberration measured by the Scheimpflug photography system (Pentacam). METHODS: A total of 47 patients (82 eyes) with age-related cataract received a comprehensive ophthalmologic examination. Corneal spherical aberration was measured by using the Scheimpflug photography system. Patients with corneal spherical aberration < or = 0.3 microm were implanted with a zero-spherical aberration advanced optics (AO) aspherical intraocular lens and those with corneal spherical aberration > 0.3 microm received a Tecnis ZA9003 aspherical lens (-0.27 microm spherical aberration). Preoperative total remnant spherical aberration was estimated and actual total spherical aberration was measured 3 months postoperatively. The consistency between preoperative and postoperative spherical aberration was analyzed by t-test, correlation analysis, and Blant-Altman plots. RESULTS: The estimated and measured values of total spherical aberration were (0.189 +/- 0.151) microm and (0.141 +/- 0.131) microm, with a statistical difference (t = 5.347, P < 0.01). For 45 eyes implanted with AO lenses, preoperatively estimated and postoperatively measured total spherical aberration were (0.268 +/- 0.137) microm and (0.214 +/- 0.103) microm. For 37 eyes implanted with Tecnis ZA9003, preoperative estimate of total spherical aberration was (0.092 +/- 0.103) microm and postoperative measured value was (0.054 +/- 0.106) microm. Statistical significance was noted, as was a positive linear correlation between preoperative and postoperative values (gamma = 0.846, P < 0.01). Bland-Altman analysis showed high consistency between the estimated and measured spherical aberration. CONCLUSION: The estimated total spherical aberration measured preoperatively differed from the value measured postoperatively, but the two values showed good agreement. It is clinically feasible to conduct personalized selection of aspherical IOL based on Scheimpflug photography system (Pentacam) to measure corneal spherical aberration.