Anterior Elevations Research Articles

Higher order aberrations in keratoconus‏.

Keratoconus is a progressive disorder of the cornea that causes thinning (Sedaghat et al. in Sci Rep 11(1):11971, 2021), ectasia, and irregular astigmatism, resulting in poor visual acuity that cannot be corrected with standard sphero-cylindrical spectacle lenses. One feature distinguishing keratoconic corneas is ocular aberrations, manifesting up to five or six times the amount of higher-order aberrations than a normal, healthy eye. These aberrations can cause visual disturbances even at the very early stages of the disease. In the past, a diagnosis was derived from clinical symptoms, but technological advances have revealed multiple pre-clinical features, allowing for the differentiation between keratoconic and normal eyes at a much earlier stage. These include anterior and posterior corneal surface elevations, the corneal pachymetry profile, corneal epithelial patterns, wavefront aberration metrics, and corneal biomechanics (Sedaghat et al. in Sci Rep 11(1):11971, 2021).This review discusses the aberrations associated with keratoconus, how to measure them, and treatment methods to minimize their negative influence. Early diagnosis can lead to early treatment and may allow for arresting progression, thereby improving the long-term prognosis. With the acceleration of refractive surgery, it is important to identify patients with keratoconus, as they are usually contraindicated for refractive surgery.

Normative Topographic Anterior and Posterior Corneal Astigmatism: Axis Distribution and Its Relations with Ocular and Biometric Parameters.

Corneal astigmatism correction is a key factor when planning refractive treatment for ametropies with intraocular lenses. We aim to obtain normative anterior and posterior corneal astigmatism (ACA and PCA, respectively) data in a local population and to describe their axis distribution and their association with other parameters. A total of 795 patients with no ocular diseases were evaluated with corneal tomography and optical biometry. Only data of the right eye were included. Mean ACA and PCA were 1.01 ± 0.79 and 0.34 ± 0.17 D, respectively. Vertical steep axis distribution was 73.5% for ACA and 93.3% for PCA. Axis orientation between ACA and PCA matched best for vertical orientation (especially 90° to 120°). Vertical ACA orientation frequency decreased with age, with a more positive sphere and less ACA. Vertical PCA orientation frequency increased with higher PCA. Eyes with vertical ACA orientation were younger and showed a greater white-to-white (WTW) measurement, anterior corneal elevations, ACA and PCA. Eyes with vertical PCA orientation were younger and showed greater anterior corneal elevations and PCA. Normative ACA and PCA data in a Spanish population were presented. Steep axis orientations presented differences with age, WTW, anterior corneal elevations and astigmatism.

Anterior segment characteristics in normal and keratoconus eyes evaluated with a new type of swept-source optical coherence tomography.

This study aimed to evaluate and compare the discriminating ability of corneal elevation maps generated using a swept-source optical coherence tomography (SS-OCT) (SS-OCT ANTERION, Heidelberg Engineering, Heidelberg, Germany), which was estimated with different reference surfaces, to distinguish normal corneas from those with keratoconus and keratoconus suspect. A total of 126 eyes of patients, which comprised 43, 37, and 46 keratoconus, keratoconus suspects, and normal controls, respectively, were included in this study. The anterior and posterior elevations at the thinnest point under the best-fit sphere (BFS) and toric-ellipsoid (BFT), respectively, and other corneal parameters were measured using the SS-OCT. In addition, the receiver operating characteristic (ROC) curve analysis and cut-off value were calculated to evaluate the diagnostic ability of the corneal elevation values in differentiating keratoconus and keratoconus suspects from normal eyes. The mean total keratometric and corneal elevation values were significantly higher in the keratoconus group than in the other groups. Pachymetric parameters exhibited the lowest values for keratoconus. In addition, ROC curve analyses showed a high accuracy of the thinnest point anterior and posterior BFT for both keratoconus and keratoconus suspects and normal controls (area under the ROC were 0.969 and 0.961, respectively). Furthermore, the optimal cut-off point of the posterior elevation at the thinnest point under BFT was 16.44 μm (sensitivity and specificity of 86% and 98%, respectively) for differentiating keratoconus from normal and keratoconus suspect eyes. The elevation map using the BFS and BFT references measured with the anterior segment SS-OCT is considered an effective indicator for keratoconus diagnosis. Therefore, the anterior segment SS-OCT can effectively differentiate keratoconus from suspected keratoconus and normal corneas by measuring parameters such as posterior and anterior elevations, pachymetry, and keratometry.

Changes in Corneal Morphology and Biomechanics in Cases of Small Incision Lenticule Extraction with Prophylactic Accelerated Collagen Cross-Linking.

Purpose To study the corneal morphology and biomechanics in cases of small incision lenticule extraction with prophylactic accelerated collagen cross-linking (SMILE Xtra). Methods This study was a retrospective study. 28 eyes of 14 patients with moderate-high risk of postoperative ectasia according to the Randleman scoring system underwent SMILE Xtra procedure. Outcome data were recorded including uncorrected distance visual acuity (UDVA), manifest refraction spherical equivalent (MRSE), surface regularity index (SRI), surface asymmetry index (SAI), simulated keratometry (SimK), posterior axial curvature (PAC), anterior and posterior corneal elevations (ACE and PCE), central corneal thickness (CCT), corneal resistance factor (CRF), corneal hysteresis (CH), and cornea-compensated intraocular pressure (IOPcc). The follow-up period was 12 months. Results There were 28, 26, 22, 12, and 10 eyes enrolled at postoperative 1st day and 1st, 3rd, 6th, and 12th months, respectively. The UDVA improved from 1.27 ± 0.18 logMAR preoperatively to -0.06 ± 0.04 logMAR postoperatively (P < 0.05). The MRSE improved from -5.05 ± 1.15 D preoperatively to -0.14 ± 0.30 D postoperatively (P < 0.05). SAI, SimK, PAC, PCE, and CCT all changed significantly at 1st month postoperatively (P < 0.05) and stabilized during the remainder of the follow-up (P > 0.05). There was no significant change in SRI or ACE before and after surgery (P > 0.05). CRF, CH, and IOPcc all decreased significantly at 1st month postoperatively (P < 0.05) and remained stable afterwards (P > 0.05). Conclusions The changes in the corneal morphology and biomechanics remained stable after SMILE Xtra, and there was no sign of postoperative ectasia or refractive regression. Combined with the improvement of visual and refractive results, SMILE Xtra may be a promising method for corneal refractive surgeries in patients at risk.

Effect of intracorneal ring segments on posterior corneal topography in eyes with keratoconus

PurposeTo analyze the changes in the anterior and posterior corneal surfaces measured with a Scheimpflug imaging device in keratoconus patients implanted with intracorneal ring segments (ICRS) and to correlate those changes with the visual outcomes. MethodsThis prospective interventional case series study included 92 eyes of 60 patients with keratoconus who underwent Kerarings (Mediphacos, Belo Horizonte, Brazil) ICRS implantation. Keratometric (K) readings, corneal asphericity (Q value) and elevations of both anterior and posterior corneal surfaces were evaluated using a Scheimpflug imaging device preoperatively and at 1, 3, 6 and 12 months after surgery. ResultsThe mean best corrected visual acuity (BCVA) improved from 0.61 to 0.19 logMAR at 12 months after surgery. Both anterior and posterior corneal surfaces showed significant flattening with statistically significant reduction of the mean anterior K reading by 3.39 D and the mean posterior K reading by 0.39 D (p<0.001) at 12 months. Statistically significant change of the anterior Q to a less negative value (from -1.05 to -0.36) was observed (p<0.001) with no significant change of the posterior Q value. Improvement of the anterior Q was significantly correlated to better postoperative BCVA (p=0.03). Better postoperative BCVA significantly correlated to better preoperative BCVA, flatter preoperative anterior and posterior K, less prolate anterior Q value and lower anterior elevations. ConclusionsICRS implantation has a significant flattening effect on both anterior and posterior corneal surfaces. Improvement of corneal asphericity is correlated to better visual outcome. Certain preoperative parameters were predictive factors of the postoperative visual improvement.

Efecto de los segmentos anulares intracorneales en la topografía corneal posterior en ojos con queratocono

PurposeTo analyze the changes in the anterior and posterior corneal surfaces measured with a Scheimpflug imaging device in keratoconus patients implanted with intracorneal ring segments and to correlate those changes with the visual outcomes. MethodsThis prospective interventional case series study included 92 eyes of 60 patients with keratoconus who underwent Kerarings (Mediphacos, Belo Horizonte, Brazil) intracorneal ring segments implantation. Keratometric (K) readings, corneal asphericity (Q value) and elevations of both anterior and posterior corneal surfaces were evaluated using a Scheimpflug imaging device preoperatively and at one, 3, 6 and 12 months after surgery. ResultsThe mean best corrected visual acuity (BCVA) improved from 0.61 to 0.19 logMAR at 12 months after surgery. Both anterior and posterior corneal surfaces showed significant flattening with statistically significant reduction of the mean anterior K reading by 3.39 D and the mean posterior K reading by 0.39 D (P<.001) at 12 months. Statistically significant change of the anterior Q to a less negative value (from −1.05 to −0.36) was observed (P<.001) with no significant change of the posterior Q value. Improvement of the anterior Q was significantly correlated to better postoperative BCVA (P=.03). Better postoperative BCVA significantly correlated to better preoperative BCVA, flatter preoperative anterior and posterior K, less prolate anterior Q value and lower anterior elevations. ConclusionsImplanted with intracorneal ring segments implantation has a significant flattening effect on both anterior and posterior corneal surfaces. Improvement of corneal asphericity is correlated to better visual outcome. Certain preoperative parameters were predictive factors of the postoperative visual improvement.

Abstract 17085: An Anomalous Outcome Of Renal Transplant

Case Presentation: A 65 year old man with diabetic renal disease developed acute dyspnea at rest on the first post-operative day after an uncomplicated deceased donor renal transplant. He was hypertensive, tachycardic, and hypoxemic. His electrocardiogram showed anterior ST elevations with reciprocal inferior ST depressions and his chest x-ray revealed pulmonary edema. He was given anti-platelet therapy, nitroglycerin, beta blocker and taken emergently for angiography. He had a thrombotic occlusion of a co-dominant anomalous left circumflex artery arising from the ostium of a moderate caliber right coronary artery. He underwent successful percutaneous coronary intervention. His post-revascularization echocardiogram showed a hypokinetic to akinetic inferior wall with preserved global left ventricular systolic function. Coronary CT for further assessment of the course of the anomalous artery was not pursued given minimal benefit and the risk of worsening graft function. He was discharged on dual anti-platelet therapy, beta blocker and a statin. Discussion: There is no consensus about risk stratification before renal transplant. Our patient’s pre-operative exercise treadmill test (ETT) showed reduced functional capacity at 5.6 metabolic equivalents, failure to reach target heart rate, with 1.0 mm down sloping ST depression in infero-lateral leads with no ischemic symptoms. While our patient had an equivocal ETT, his lack of angina argued against further work-up. Post-operatively, a pro-inflammatory state, increased shear stress, acquired thrombophilia and immunosuppressive medications can all contribute to plaque rupture with thrombus formation. Atherosclerosis due to diabetes and renal disease coupled with mechanical factors such as passive compression at the intraarterial course, acute angle take-off or valve-like closure of the slit orifice may have subjected our patient with an anomalous left circumflex artery to an acute ST-elevation MI.

Interpretation of Variation in Corneal Parameters with Age using Pentacam: A Cross-sectional Study

Introduction: Previous equipments used to study cornea were mostly Placido based which could only analyse anterior surface of cornea, while Pentacam is based on elevation based imaging method that helps to study the curvature of cornea, its elevation and thickness profile more accurately. There are numerous studies published to study the thickness of cornea, this study outlines the importance of changes introduced in various corneal parameters with age which in itself is an important factor with possible positive correlation. Aim: To determine various corneal parameters and to interpret the variations in these with increasing age. Materials and Methods: This cross-sectional study included a cohort of 60 healthy patients attending Outpatient Department of Ophthalmology from July 2019 to February 2020. Two sets of values were determined, studied and compared between different age groups. First set of values included, keratometry values in the flat (K1) and steep (K2) and maximal keratometry values of the front surface (Kmax). Second set of values included, Anterior Elevations (AE), Posterior Elevations (PE), PE minus AE from Best Fit Sphere of 8 mm (BFS) and PE from the Best-fit Toric Ellipsoid (BFTE), apex thickness (CCT), pachymetry at the thinnest-point thickness (TCT),average corneal Pachymetry Progression Indices (PPI avg) and average Ambrosio’s Relational Thickness indices (ART avg). Based on age, three groups were created with 20 participants in each, Group A with age 18 to 25 years, Group B with age between 26 and 40 years and Group C with age more than 40 years. Scanning of all study subjects was done using Pentacam. Mann-Whitney U test and Spearman correlation test were used for the statistical analysis. Results: The average age was 21±2.42 years in group A, 30.9±4.3 years in group B and 42.45±1.65 years in group C. When AE, PE and PE-AE values were compared among three age groups, results were highly significant with p-value &lt;0.00001. Thus, the elevation indices from BFS were found to be correlated with age. On comparison of PPI average between group A and B, group B and C values were statistically insignificant (p-values 0.51 and 0.19, respectively).Though in comparison between Group A and C, average corneal PPI avg was found to be of statistical significance (p-value=0.048). Average ART indices (ART avg) was found to produce highly statistically significant results among 3 groups (p-value &lt;0.00001). Conclusion: The corneal parameters are significantly altered from their normative values with age. This study outlines that elevations indices and avg ART values are significantly altered with increasing age.

Correlation of corneal elevations measured by Scheimpflug corneal imaging with severity of keratoconus

PurposeTo evaluate the correlation of corneal elevation and difference elevation with severity of keratoconus. MethodsAnterior and posterior corneal elevations with both conventional and enhanced best-fit spheres (using rotating Scheimpflug camera) were measured. Front and back difference elevation were extrapolated from difference map of Belin/Ambrỏsio Enhanced Ectasia Display of the Scheimpflug system. Data from corneal elevations and difference elevations were correlated with maximum keratometry, minimal corneal thickness, and severity of keratoconus as assessed by Amsler-Krumiech classification of keratoconus. ResultsNinety eyes of 55 keratoconus patients of different clinical stages were evaluated. There was a significant positive correlation between keratoconus severity and corneal elevations (anterior and posterior elevation as measured with both conventional and enhanced best-fit spheres) and also between keratoconus severity and corneal elevation differences (P < 0.001 and r > 0.625 for all). Maximum keratometry (Kmax), mean keratometry (Kmean), and all corneal elevations and difference elevations were highly correlated (P < 0.001 and r > 0.840 for all). A significant negative correlation was found between minimum corneal thickness and all corneal elevations and difference elevations (P < 0.001 and r < 0.711 for all). Receiver operating characteristic (ROC) curve analyses showed that anterior and posterior difference elevations have the best predictive accuracy for grading keratoconus severity. ConclusionEvaluation of corneal elevation and difference elevation data obtained from Scheimpflug corneal imaging is useful for grading severity of keratoconus.

Normative Pentacam anterior and posterior corneal elevation measurements: effects of age, sex, axial length and white-to-white.

To provide normal corneal elevation data for a large Caucasian population and to determine the impacts on these data of age, sex, axial length (AXL) and horizontal white-to-white (WW). Centro Internacional de Oftalmología Avanzada, Madrid, Spain. Retrospective, cross-sectional, observational. In this retrospective, cross-sectional, observational study, anterior and posterior corneal elevations were measured in 789 right eyes of subjects with no ocular disease at the thinnest corneal location in relation to a fixed 8-mm best-fit sphere using the Pentacam, and AXL and WW were measured with the IOLMaster. A multiple linear regression model was used to assess the effects of age, sex, AXL and WW on the elevation data. Mean subject age was 50.5 ± 15years (range 17-93years); 64% were women. Mean anterior and posterior corneal elevations were 1.99 ± 1.75µm (- 7 to 10µm) and 7.70 ± 5.7µm (- 6 to 28µm). Anterior corneal elevations were higher by 0.165μm and 0.033μm for every mm reduction in AXL and every year reduction in age, respectively. Sex and WW were not significant predictors of anterior elevations (R2 = 7.7%). Posterior corneal elevation increased by 0.186μm/year of age, 0.707μm/mm reduction in WW and 0.819μm/mm reduction in AXL. This variable was also 0.866μm greater in men (R2 = 34.4%). Anterior corneal elevations decrease with age and are higher for shorter AXL but are not influenced by sex or WW. Posterior corneal elevations increase with age, decreasing AXL, decreasing WW and are higher in men.

Age-related variations in corneal geometry and their association with astigmatism: The Yamagata Study (Funagata).

To investigate how aging affects corneal geometry in Japanese adults, and the association between corneal geometry and astigmatism.We included 421 participants who had undergone systemic and ophthalmological examinations in 2015 in Funagata town, Yamagata, Japan. Corneal topographic data were obtained using anterior-segment optical coherence tomography (CASIA SS-1000). Astigmatism was evaluated using power vector analyses where J0 represents the power of the orthogonal astigmatism. Positive values of J0 indicate with-the-rule astigmatism, while negative values indicate against-the-rule (ATR) astigmatism.Regarding age-related variations in corneal geometry, the anterior elevations at axis 0° and 180° decreased, and those at axis 90° and 270° increased with increasing age in linear regression analyses, demonstrating horizontal steepening and vertical flattening of the corneal surface. There were no significant age-related variations in posterior elevations and pachymetry findings, including central corneal thickness. Regarding age-related variations in orthogonal astigmatism, the mean values of J0 and corneal J0 (cJ0) decreased by –0.014 and –0.015 per year of increase in age, indicating astigmatic shift toward ATR. Regarding the correlation between corneal geometry and astigmatism, the shift toward ATR was positively correlated with horizontal steepening and vertical flattening, in accordance with the age-related corneal variations. In addition, the posterior surface of the cornea also has an association with this shift to some extent.The results of our population-based study demonstrated that the age-related variation in astigmatism is associated with geometrical changes in the cornea, especially those in the anterior surface of the cornea.

Anterior Segment Changes After Femtosecond Laser-Assisted Implantation of a 355-Degree Intrastromal Corneal Ring Segment in Advanced Keratoconus.

To study anterior segment changes after implantation of a Keraring with a 355-degree arc length in central advanced keratoconus. Thirty eyes of 22 patients with advanced central keratoconus (grade 3) and absent corneal scarring underwent femtosecond laser-assisted (VisuMax) implantation of a Keraring 355-degree arc length intrastromal corneal ring segment (ICRS) with a segment thickness of 300 μm. Comprehensive ocular evaluations were performed preoperatively and postoperatively to assess uncorrected distance visual acuity, corrected distance visual acuity, K1, K2, Kmax, corneal volume, anterior chamber depth, corneal elevations, and actual segment position 6 months after the procedure. Corrected distance visual acuity in decimal notation improved significantly from 0.22 ± 0.17 to 0.49 ± 0.22 (P < 0.01). Statistically significant changes were found in the measured parameters with marked reconstruction of the cornea and anterior chamber. However, the actual depth percent of the ring segment was 61.7% ± 5.9%, which was shallower than the intended depth of 80% of corneal thickness. These findings may help explain the marked improvement in visual parameters obtained from the Keraring 355 degrees in advanced central keratoconus. In addition, these types of rings may be a safe, effective, and minimally invasive way to avoid corneal grafting in advanced keratoconus with a clear cornea.

Evaluation of Scheimpflug Tomography Parameters in Subclinical Keratoconus, Clinical Keratoconus and Normal Caucasian Eyes.

Objectives:To evaluate tomographic and topographic parameters in subclinical and clinical keratoconus eyes by comparing them with normal eyes in a young Caucasian population.Materials and Methods:This cross-sectional study included 88 normal eyes (control group), bilateral data from the preclinical stage of 24 progressive keratoconus eyes (bilateral subclinical keratoconus group), 40 fellow eyes of patients with unilateral keratoconus (fellow eyes group) and 97 eyes with mild keratoconus (clinical keratoconus group). Topographic and tomographic data, data from enhanced elevation maps and keratoconus indices were measured in all study eyes using Scheimpflug tomography. Receiver operating characteristic (ROC) curve analysis was used to assess individual parameters to discriminate eyes of patients with subclinical and clinical keratoconus from control eyes. The sensitivity and specificity of the main effective parameters were evaluated and optimal cut-off points were identified to differentiate subclinical keratoconus and keratoconus from normal corneas.Results:Comparison of all subclinical and clinical keratoconus eyes from the normal group revealed significant differences in most diagnostic parameters. The ROC curve analysis showed high overall predictive accuracy of several Pentacam parameters (overall D value, anterior and posterior elevations and difference elevations, pachymetry progression index, index of surface variance, index of height decentration and keratoconus index) in discriminating ectatic corneas from normal ones. These outcomes were proportionally less pronounced in all subclinical keratoconus eyes than in the clinical keratoconus eyes. Pachymetric readings were progressively lower in the bilateral subclinical keratoconus eyes and sensitivity and specificity of the analyzed tomographic and topographic parameters were higher than the fellow eyes group when differentiating subclinical keratoconus from healthy corneas.Conclusion:Scheimpflug tomography parameters such as D value, elevation parameters, progression index and several surface indices can effectively differentiate keratoconus from normal corneas in a Caucasian population. Nevertheless, a combination of different data is required to distinguish subclinical keratoconus.

Anterior Segment Parameters in Patients With Wilson Disease.

To investigate anterior segment parameters in patients with Wilson disease (WD). In this cross-sectional study, 22 patients with WD (study group) and 22 healthy subjects (control group) were enrolled. Each participant underwent a comprehensive ophthalmic assessment including best-corrected visual acuity, slit-lamp biomicroscopy, fundus examination, and intraocular pressure. Anterior segment parameters were measured by the Sirius anterior segment analyzer system (Costruzione Strumenti Oftalmici, Florence, Italy). Mean central corneal thickness was 522 ± 47 μm in the study group and 568 ± 37 μm in the control group (P < 0.001). Mean flat keratometry was 42.4 ± 1.7 diopter (D) in the study group and 41.5 ± 1.16 D in the control group (P = 0.011); mean steep keratometry was 43.4 ± 2.0 and 42.4 ± 1.4 D in the study and control groups, respectively (P = 0.025). The anterior corneal elevation value was 5.5 ± 3.2 μm in the study group and 4.08 ± 2.2 μm in the control group (P = 0.029); the mean posterior corneal elevation value was 15.1 ± 6.0 and 10.1 ± 4.1 μm in the study and control groups, respectively (P = 0.002). The mean anterior chamber depth was 2.97 ± 0.3 μm in the study group and 3.16 ± 0.3 μm in the control group (P = 0.01); the mean horizontal visible iris diameter was 11.9 ± 0.4 and 12.2 ± 0.4 μm in the study and control groups, respectively (P = 0.001). This study indicates that patients with WD have differences in the anterior segment parameters including central corneal thickness, keratometric values, anterior and posterior elevations, horizontal visible iris diameter, and anterior chamber depth when compared with healthy controls.

Topographic typology in a consecutive series of refractive surgery candidates.

The term 'keratoconus (KC) suspect' is used as a blanket term to refer to any deviation of virgin cornea shape toward KC features. We intend to subclassify such topographies in meaningful and informative designations. Pentacam corneal topographies of 199 consecutive refractive surgery candidates (398 eyes) are examined. Features of steepness, inferior-superior asymmetry, focal steepening, thinning, and bounded anterior or posterior elevations are observed in the quad map. Scissoring on retinoscopy, loss of best spectacle-corrected visual acuity, and iron ring deposition were looked for. Through iterative observation and refinement of classification criteria-partly taken from the literature-all eyes were designated a specific topographic diagnosis, i.e., circumventing the usage of the expression KC 'suspect'. Topographies of 308, 48, 21, 13, 6, 1, and 1 (collectively 398 eyes) were designated: normal, 'atypical normal,' forme fruste KC, posterior KC, subclinical/mild KC, superior KC, and pseudo-KC, respectively. Current imaging modalities of the cornea and our accumulated experience in refractive science allow assignment of distinctive designations for abnormal corneal shapes along the topography spectrum. We devised and used the expressions: normal, atypical normal, forme fruste (arrested-incomplete) KC, posterior KC, subclinical (active latent) KC, superior KC, and pseudo-keratoconus. Identification of 1.5% (mild) KC highlights the importance of screening for ultraviolet cross-linkage candidacy in refractive surgery referrals.

Thick keratoconic cornea associated with posterior polymorphous corneal dystrophy

We herein report a case of bilateral unusually thick non-edematous keratoconic corneas with associated endothelial features of posterior polymorphous corneal dystrophy (PPCD). We report the case of a 27-year-old myopic woman who presented for refractive surgery. Slit lamp exam showed bilateral corneal protrusion with diffuse deep stromal and endothelial vesicular opacities and small paracentral bands. Topography showed generalized advanced corneal steepening in both eyes with increased anterior and posterior central corneal elevations in comparison to the best fit sphere. Ultrasound pachymetry showed central corneal thickness of 605μm (RE) and 612μm (LE). On specular biomicroscopy, cell density of 2503 cells/mm2 RE and 1526 cells/mm2 LE with significant cellular pleomorphism and polymegathism were noted. Clinical and paraclinical findings together suggest the presence of simultaneous keratoconus and PPCD. The literature has suggested an association between PPCD and steep cornea. Moreover, many reports have also described cases of associated PPCD and keratoconus with characteristic thinning and ectasia, in comparison to the unusual thick corneas noted in our patient, despite the absence of edema. Identification of genetics factors is further needed to clarify this association. This case describes a patient whose corneas present features of both keratoconus and PPCD and is unique due to the presence of increased corneal thickness despite the absence of edema.

Accelerated corneal collagen cross-linking in pediatric keratoconus: One year study

PurposeTo evaluate the safety and effectiveness of accelerated corneal collagen crosslinking (CXL) in pediatric keratoconus. DesignProspective non-randomized observational study. Methods33 eyes of 25 children with keratoconus were included. The corneal epithelium was mechanically removed. Next, riboflavin/hydroxypropyl methylcellulose solution) was applied for 10min. Accelerated CXL (10mW/cm2 for 9min), was accomplished. Visual acuity, slit lamp examination, refraction, keratometry readings, pachymetry, anterior and posterior elevations, average progression indices, and Q values were recorded. The follow-up visits were scheduled on one day, 3 days, 7 days, one month and then on 3, 6, 12 months after the procedure. ResultsIt was statistically significant improvement of the mean UAVA, AVA, and the mean corneal astigmatism (P<.0001). The mean corneal thickness showed a significant reduction. The preoperative mean K max reading was reduced from 49.12±3.7D preoperatively to 47.9±3.7D at 12 months. The mean max anterior elevation, average progression index and Q value showed statistically significant improvement. No significant impact on posterior elevation was recorded. Serious complications were not encountered in this study. ConclusionAccelerated CXL shows a stabilization and beneficial clinical outcomes in pediatric keratoconus. It seems an effective and safe procedure in this age group. Effects of accelerated CXL on the posterior corneal surface will need further evaluation.

Clinical results of transepithelial corneal collagen cross-linking in the treatment of keratoconus

To evaluate the effect of transepithelial corneal collagen cross-linking (CXL) in the treatment of keratoconus. Prospective study. Sixteen eyes of 16 patients with keratoconus underwent transepithelial CXL, and the fellow eyes were considered as the controls. The mean age was (22.4±6.5) years old. In the CXL group, topical anesthesia (0.1% tetracaine) was given for 15 minutes, and 0.5% riboflavin was applied until saturated in the anterior chamber. Then an ultraviolet A irradiance of 3 mW/cm(2) on the cornea was performed for 30 minutes. Postoperative corneal reepithelization time was recorded. Preoperative and postoperative examinations included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive error, topography, corneal biomechanical parameters, thinnest corneal thickness, and endothelial cell density. The mean corneal reepithelization time was 1.0(1.0 to 2.0) days. In the transepithelial CXL group, at the end of the 12-month follow-up, CDVA and refractive outcomes were significantly improved (P<0.05). Maximum K-value, anterior and posterior elevations were significantly decreased by (-2.23 ± 2.82)D (t=-3.153, P=0.007), (-4.69 ± 4.99) μm (t=-3.758, P=0.002), and (-13.94 ± 25.81) μm (t=-2.160, P=0.047), respectively. Corneal hysteresis, corneal resistance factor, thinnest corneal thickness, and endothelial cell density showed no significant difference (P>0.05). The differences in the changes of UDVA, CDVA, spherical equivalent refraction, and maximum K-value between the CXL and control groups were significant at 12 months (P<0.05). Transepithelial CXL is effective in optimizing the irregular corneal surface of keratoconus, and might halt its progression. (Chin J Ophthalmol, 2016, 52: 525-530).

Corneal elevation in a large number of myopic Chinese patients.

To establish a normative database for corneal elevation in Chinese myopic patients who underwent refractive surgery, and analyze the association of corneal elevation with sex, age, and ocular parameters. A total of 3000 eyes in 1500 patients were evaluated with the Pentacam. Anterior and posterior elevations were measured at the apex and thinnest point. Normative thresholds were defined according to the Tukey method. Univariate and multivariate analyses were performed to assess the association of corneal elevation with sex, age, and ocular parameters. Normal upper limits for corneal elevation in adult Chinese were 4.95μm, 5.25μm, 6.2μm, and 11.0μm at the anterior apex, anterior thinnest point, posterior apex, and posterior thinnest point, respectively. Thinner corneal pachymetry at the apex and greater anterior corneal astigmatism tended to show greater anterior corneal elevation values. Younger age, greater anterior corneal astigmatism, lower anterior and posterior keratometry, and shallower anterior chamber depth resulted in greater posterior corneal elevation values. Locally derived thresholds may offer higher sensitivity and specificity when screening eyes for myopic refractive surgery, and keratoconic and post-orthokeratology eyes. Anterior and posterior corneal elevation at the apex and thinnest point were associated significantly with anterior corneal astigmatism, showing a positive correlation.

Effects of Collagen Cross-Linking on the Corneal Optical and Topographic Characteristics in Progressive Keratoconus

Aim: To determine the significant changes which occur in the corneal parameters, including pachymetry, after corneal collagen cross linking (CXL) by means of Scheimpflug imaging. Methods: Standard CXL procedure was done for 40 eyes diagnosed as progressive keratoconus (KCN). The following parameters were monitored pre, six months and 1 year post operatively: uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), refractive spherical equivalent (S.E), keratometry1 (K1) and keratometry2 (K2), apex and thinnest point pachymetries, thinnest point coordinates (X,Y) minimum (Min.), maximum (Max.), average (Avg.) pachymetric progression indices, Max. Anterior and posterior elevations. Pentacam (Oculus, Wetzlar, Germany) imaging was used to monitor the corneal parameters of the study. Paired sample T test was used for statistical analysis. Results: Following parameters of the study did not show significant changes after CXL: UCVA: (P= 0.65), BCVA: (P= 0.076), S.E: (P= 0.343), Thinnest point X coordinate: (P=0.545), Thinnest point Y coordinate: (P= 0.144), Max. Anterior elevation (P= 0.508) and the following parameters showed significant changes: K1: (P= 0.001), K2: (P= 0.015), Apex pachymerty: (P <0.001), Thinnest point pachymetry: (P <0.001), Max. Post. Elevation: (P= 0.001) and all (Max., Min., Avg.) pachymetric progression indices: (P <0.001 for all 3). The most significant changes occurred in pachymetric progression indices. Conclusion: We could show six months to 1 year after CXL procedure, the corneal thickness is lower than its baseline and keratometric changes have been settled during this period. UCVA, BCVA have not been changed significantly and the pachymetric progression indices are the most significant parameters to have changes, when evaluating them by Pentacam. Validity of Scheimpflug imaging of the corneas after CXL should be determined in further studies.