Evaluation of the efficacy, safety, and stability of posterior chamber phakic intraocular lenses for correcting intractable myopic anisometropic amblyopia in a pediatric cohort.

BACKGROUND: Myopic anisometropic amblyopia in pediatrics is one of the most challenging clinical situations that can face an ophthalmologist. Conventional correction modalities for myopic anisometropia, using spectacles, contact lenses, and/or occlusion therapy, may not be suitable for some pediatric patients or for some ocular conditions. This may lead to the development of anisometropic amblyopia. The aim of the present study was to evaluate the visual and the refractive efficacy, safety, and stability of Posterior Chamber Phakic Intraocular Lenses (PC-pIOLs) for correcting myopic anisometropic amblyopia in a pediatric cohort. METHODS: This case series, prospective, interventional study was conducted at Watany Eye Hospital, Cairo, Egypt. It comprised children and teenagers with myopic anisometropic amblyopia and unsuccessful conventional therapy. After implantation of Intraocular Collamer Lenses "ICLs" (Visian ICL, Model V4c, STAAR Surgical, Monrovia, California, USA), postoperative follow-up visits were scheduled, with automated refraction and Pentacam imaging performed. RESULTS: The study enrolled 42 eyes of 42 patients. The age range was 3 to 18 years (mean ± SD = 10.74 years ±4.16). The mean preoperative spherical equivalent (SE) was - 12.85 D ± 2.74. The results declared a significant improvement in the postoperative Corrected Distance Visual Acuity "CDVA" (P value < 0.01) and SE (P value < 0.01). The efficacy index had a value of 1.18 ± 0.3 and the safety index was 1.09 ± 0.24. The follow-up visits had a mean ± SD of 14.67 months ±16.56 (range of 1 to 54 months). The results showed a refractive stability, with statistically insignificant improvements in the patients' visual acuity and refractive status on evaluating the enrolled pediatrics during the follow-up visits compared to the first postoperative visits. No postoperative complications were encountered. Worthy of mention is that there was a significant (80%) non-compliance with the prescribed postoperative occlusion therapy. CONCLUSIONS: The present study, with the longest reported follow-up range, declared the long-term efficacy, safety, and stability of Visian ICLs for correcting myopic anisometropic amblyopia in pediatrics. The reported non-compliance with occlusion therapy validates the early implantation of Visian ICLs in cases with failed conventional therapy to guard against anisometropic amblyopia.

Accuracy of the posterior corneal elevation values of Pentacam HR from different reference surfaces in early ectasia diagnosis.

PURPOSE: Detecting the accuracy of various posterior elevation (PE) indices of Pentacam HR, and correlating them with some possibly related factors or parameters, in a cohort with early keratoconus (KC). METHODS: A cross sectional study that was conducted at Eye World Hospital, Egypt. One hundred and two corneas were enrolled, including two groups; group 1 (50 corneas) having forme fruste or early KC, and group 2 (52 corneas) for healthy controls. Corneas were scanned using Pentacam HR (Oculus, Wetzlar, Germany). The investigated PE parameters were: PE from best fit sphere (BFS), PE from best fit toric ellipsoid (BFTE), PE from exclusion map of Belin Ambrosio's display (BAD), and PE from difference map of BAD. The four PE values were correlated to age, thinnest corneal thickness "TCT," posterior aberrations, and posterior Q value. RESULTS: All the investigated indices were significantly different in group 1 compared to group 2 (p < 0.001). Accuracy of PE parameters revealed the highest AUROC for PE from BFTE (AUROC = 0.989, and best cutoff > 4 um with sensitivity 96.00% and specificity 96.15%). PE from difference map was the least accurate. Correlation coefficients showed a significant correlation between all the studied PE parameters and some of the posterior aberrations (root mean square of higher order aberrations, vertical coma, and spherical aberrations), besides a significant correlation with posterior Q value. CONCLUSION: PE indices are sensitive detectors of early ectasia. PE from BFTE had the highest deduced AUROC. Alterations in PE values can significantly alter many posterior corneal aberrations and the posterior Q.

ELECTRORETINOGRAPHIC AND VISUAL-EVOKED POTENTIAL CHANGES IN RELATION TO CHELATION MODALITY IN CHILDREN WITH THALASSEMIA.

PURPOSE: To evaluate possible benefits of using electrophysiological investigations for detecting retinal and visual pathway changes and correlating them with chelation modality in children with thalassemia. METHODS: This study included 60 patients on single oral iron chelator (deferasirox) (Group 1), 60 on deferoxamine chelator (Group 2), and 60 controls (Group 3). Participants underwent full ophthalmologic examination, pattern visual-evoked potential, pattern electroretinogram, and multifocal electroretinogram. RESULTS: Fundus showed no abnormalities. Multifocal electroretinogram mean P1 amplitude showed statistically significant differences in all 5 rings, amplitudes being significantly lower in Groups 1 and 2 than Group 3; moreover, significantly lower in Group 2 than Group 1. There was a statistically significant difference between groups regarding P50 wave latency and N35-P50 of pattern electroretinogram amplitude (P < 0.001 and P < 0.001, respectively). However, there were no statistically significant differences between groups regarding N95 wave of pattern electroretinogram and pattern visual-evoked potential waves' amplitude and latency. Multiple regression analyses illustrated that chelator was the most important determinant for multifocal electroretinogram and P50 parameters. CONCLUSION: Preclinical electrophysiologic changes existed in thalassemics, more obvious in those on deferoxamine. Electrophysiologic studies analysis denotes an early toxic macular insult rather than optic nerve affection. Thus, regular follow-up using multifocal electroretinogram and pattern electroretinogram is recommended.

CORRELATION BETWEEN SUBFOVEAL CHOROIDAL THICKNESS AND FOVEAL THICKNESS IN THALASSEMIC PATIENTS.

PURPOSE: To assess the impact of two iron chelation modalities in thalassemic patients on foveal and subfoveal choroidal thickness. METHODS: The study included 60 ß-thalassemia major patients. They included 30 patients on oral deferasirox after a period of subcutaneous deferoxamine (Group 2) and 30 patients on subcutaneous deferoxamine (Group 3). Thirty age- and sex-matched healthy children were included as a control group (Group 1). All participants underwent a complete ophthalmologic evaluation and Spectral Domain Optical Coherence Tomography. RESULTS: Age, gender, intraocular pressure, best-corrected visual acuity, and refraction were not statistically different between the three studied groups. Ferritin level, pretransfusion hemoglobin, serum iron, and duration of thalassemia were not statistically different between the two thalassemic groups. Foveal thickness in Group 1 (225.15 ± 17.35 µm) was statistically higher than in Group 2 (210.53 ± 21.73 µm) (P < 0.001) and Group 3 (200.15 ± 7.34 µm) (P < 0.001). It was statistically higher in Group 2 than in Group 3 (P = 0.001). Subfoveal choroidal thickness in Group 1 (279.70 ± 32.54 µm) was statistically higher than in Group 2 (255.80 ± 19.20 µm) (P < 0.001) and Group 3 (248.28 ± 20.43 µm) (P < 0.001). It was statistically higher in Group 2 than in Group 3 (P < 0.05). CONCLUSION: Thalassemic patients can develop a significant decrease in foveal thickness because of the inevitable use of chelation therapy. Deferoxamine as a chelating agent can affect foveal thickness more than the oral form (deferasirox).

Application of a Revised Tissue Saving Protocol for Combined Topography-Guided Photorefractive Keratectomy and Cross-Linking in a Cohort Having Pellucid Marginal Degeneration.

Purpose: To evaluate the efficiency, safety, and stability of a revised tissue-saving treatment protocol in a cohort having pellucid marginal degeneration (PMD). Methods: A retrospective cohort study was conducted on patients with PMD and no previous treatments. A revised protocol of topo-guided photorefractive keratectomy to be followed by customized phototherapeutic keratectomy and then corneal crosslinking was evaluated by comparing the pre and postoperative outcomes regarding visual (subjective refraction) and topographic (using data from Sirius CSO topography software) outcomes. Results: There were both statistically significant and clinically relevant improvements in the postoperative parameters, where each of the unaided and corrected visual acuity, spherical equivalent, refractive cylinder, K readings, topographic cylinder, inferior minus superior difference at the 2- and 4- mm diameters, coma aberration, and higher order aberrations were significantly better postoperatively (all p values were less than 0.01, except for maximum k readings where the p-value was 0.017). The safety and efficacy indices for the surgical procedure were remarkably high (1.53 ± 0.70 and 0.90 ± 0.32, respectively). Conclusion: Our proposed tissue-saving protocol (which showed satisfactory results in keratoconus cases according to a previously published article by our research team) has proven its successful outcomes (both topographically and visually) in cases of PMD, which is a rare ectatic entity with guarded prognosis using the available conventional ectasia treatment modalities.

Novel Technique to Improve the Efficacy of Corneal Cross Linking in Cases of Post LASIK Ectasia.

Purpose: The aim of the present study was to validate the use of a novel technique that can improve the efficacy of corneal cross-linking (CXL) in cases with post LASIK ectasia. Methods: This is a retrospective, comparative study that was conducted on patients who sought medical advice at Ain Shams University Hospitals and Maadi Eye Subspeciality Center, Cairo, Egypt. It included two groups of patients with post LASIK ectasia. Group 1 included patients who performed our proposed protocol (topo-guided PRK, followed by customized phototherapeutic keratectomy "PTK" to transmit the laser treatment to the corneal stroma, then CXL). For group 2, accelerated CXL was performed. Subjective refraction and relevant topographic/tomographic parameters (Sirius topographer) compared between the two groups. Recorded follow-ups included the 2 to 3-month follow-up visit and the last visit (mean ± SD of 17.2 months ± 10.2). Results: Patients of group 1 (22 eyes of 22 patients) experienced significant improvements in most of the evaluated parameters at the 2- to 3-month follow-up visit and showed stability of the ectatic condition at the last follow-up visit, whereas patients of group 2 (10 eyes of 10 patients) showed stability of their ectatic condition at the 2- to 3-month follow-up visit, and one patient developed ectasia progression at the last follow-up visit. Conclusion: The present study validates the use of our novel protocol in cases having post LASIK ectasia with proven efficacy, safety, and stability, providing regularization for the corneal surface while simultaneously avoiding the unnecessary loss of cross-linking effect within the LASIK flap that no longer shares in the corneal biomechanical strength.

Introducing a Revised Tissue Saving Protocol for Combined Topography-Guided Photorefractive Keratectomy and Cross-Linking in Keratoconic Corneas.

PURPOSE: The aim of this study was to introduce a revised tissue-saving technique for combined topography-guided photorefractive keratectomy (PRK) and cross-linking for keratoconus (KC) treatment and to evaluate its efficacy, safety, and stability. METHODS: This retrospective, noncontrolled study was performed at Maadi Eye Subspecialty Center and Eye Care Center, Cairo, Egypt. The technique was performed on virgin keratoconic corneas with 3 different morphological patterns of ectasia. It involves performing topography-guided PRK before epithelial removal, followed by customized phototherapeutic keratectomy (PTK) that is tailored to each cornea after studying the treatment profile on the laser treatment screen. The electronic medical records were explored for preoperative and postoperative data, including subjective refraction and topographic data (using Sirius topographer). RESULTS: The study was conducted on 123 eyes of 93 patients with a mean age of 27.98 years ±6.06. The follow-up ranged from 6 to 36 months (mean ± SD of 16.2 months ±10.4). The results showed statistically nonsignificant differences among the 3 ectasia subgroups in treatment spherical equivalent, treatment maximum depth, thickness of removed epithelium, and thinnest residual stromal bed. There were statistically significant differences in almost all values between the preoperative and postoperative data, with significant postoperative patients' improvement ( P value <0.001). The subgroups' results were almost the same as the whole cohort's results. The safety and efficacy indices of the performed procedure showed remarkably high values (1.48 ± 0.21 and 0.87 ± 0.40, respectively). CONCLUSIONS: This revised protocol for KC management maximally preserves stromal tissue with proven efficacy, safety, and stability.

Comparison Between Pulsed and Continuous Accelerated Corneal Cross-Linking Protocols.

Purpose: To compare between two accelerated corneal cross-linking (A-CXL) protocols in the management of keratoconus (KC) as regard to the extent of corneal treatment. Methods: This retrospective, comparative study included patients having mild to moderate, progressive KC. The study population was divided into two groups; group 1 enrolled 103 eyes of 62 patients who received pulsed light A-CXL (pl-CXL) at a power of 30 mW/cm2 with an irradiation time of 4 minutes, while group 2 comprised 87 eyes of 51 patients who received continuous light A-CXL (cl-CXL) at a power of 12 mW/cm2 with an irradiation time of 10 minutes. Recordings of the central and peripheral demarcation line depths (DD), and the maximum (DDmax) and minimum (DDmin) DD, using anterior segment optical coherence tomography, were compared between the two studied groups one month after the treatment protocol. Treatment stability was also evaluated pre and postoperatively (one year following surgery) by comparing the refractive and keratometric outcomes in both groups. Results: The differences between the preoperative corneal thickness (minimum and central) and the epithelial thickness measurements between both groups were not statistically significant. Although group 1 had slightly larger central DD (223.4 ± 62.3 um), DDmax (240.4 ± 61.8 um), and DDmin (201 ± 54 um) than those of group 2 (221.8 ± 37 um, 229.1 ± 38.4 um, and 212 ± 37.2 um, respectively), the differences between both groups' measurements were not statistically significant. Also, the two groups showed statistically insignificant differences regarding the subjective refraction and the average and maximum keratometry pre and postoperatively, denoting visual, refractive, and keratometric stability in both groups. Conclusion: Longer duration cl-CXL seems to be as effective as pl-CXL regarding both postoperative stability and the extent of corneal tissue penetration by the ultraviolet treatment.

Assessment of Preoperative Risk Factors for Post-LASIK Ectasia Development.

Purpose: To evaluate preoperative risk factors (mainly those related to corneal topography/tomography) for post-LASIK ectasia development. Methods: A retrospective case review for post-LASIK ectasia for myopia or myopic astigmatism. The evaluated data included preoperative subjective refraction, method of flap creation, and topometric/tomographic parameters from Oculus Pentacam, including subjective curvature pattern, topometric, elevation, and pachymetric indices from the Belin Ambrosio display "BAD", and the Pentacam Random Forest Index (PRFI). Moreover, preoperative ectasia detection indices were calculated (including Percentage of Tissue Altered "PTA" index, Randleman Ectasia Risk Score System "ERSS", and Navarro Index for Corneal Ectasia "NICE"). Results: Twenty-four eyes of 15 patients were enrolled. Concerning the risk factors, age was lower than 25 in 19 eyes (79%); flaps were created using a microkeratome in 17 eyes (70.8%); thinnest pachymetry was lower than 510µm in eight eyes (33%); total deviation from BAD was higher than 1.6 in 50%; Ambrósio's relational thickness (ART) max was lower than 340 in 45.83%; PTA index was higher than 40% in 16%; ERSS was more than 3 points in 62.5%; NICE was higher than 8 points in three eyes (12.5%); PRFI index was more than 0.125 in 87.5%; two eyes (8%) had no identifiable risk factors. Conclusion: Current ectasia risk assessment criteria were insufficient for detecting a relatively large number of cases. There is an unequivocal need for more information, which may be derived from biomechanical assessment and epithelial thickness mapping. Novel corneal tomography indices derived from artificial intelligence may increase accuracy in characterizing ectasia susceptibility.

Challenges of personal protective equipment use among ophthalmologists during the COVID-19 pandemic: A multicenter international study.

PURPOSE: To explore the possible challenges and difficulties of using Personal Protective Equipment (PPE) in ophthalmic practice during the Coronavirus disease 2019 (COVID-19) pandemic. METHODS: This is a multicenter, international survey among practicing ophthalmologists across different countries. The survey was conducted from September 9th to October 24th, 2020. It included a total of 23 questions that navigated through the currently adopted recommendations in different clinical situations. The survey also assessed the convenience of using various PPE in ophthalmic practice and addressed the clarity of the examination field while using various PPE during clinical or surgical procedures. RESULTS: One hundred and seventy-two ophthalmologists completed the survey (101 from Egypt, 50 from the USA, and 21 from four other countries). The analysis of the responses showed that most ophthalmologists use face masks without significant problems during their examinations, while face shields followed by protective goggles were the most inconvenient PPE in the current ophthalmic practice. Moreover, most of the participants (133, 77.3%) noticed an increase in their examination time when using PPE. Furthermore, a considerable percentage of the respondents (70, 40.7%) stopped using one or more of the PPE due to inconvenience or discomfort. CONCLUSIONS: Due to the unique nature of the ophthalmic examination, certain PPE are not ophthalmologist-friendly. Innovative PPE should be tailored for prompt, more convenient, and clearer ophthalmological practice.

Endothelial cell loss rate after penetrating keratoplasty: optical versus therapeutic grafts.

Background: This study aimed to compare the rate of endothelial cell loss (ECL) after penetrating keratoplasty (PKP) for optical versus therapeutic grafts at 3-, 6-, and 12-month postoperatively. Furthermore, the study aimed to investigate postoperative graft viability and the rate of graft rejection during the first year of follow-up for both indications. Methods: This was a prospective, observational, comparative study that included patients who sought medical advice at the cornea outpatient clinic of Ain Shams University Hospitals, Cairo, Egypt. The study recruited 60 patients: group 1 included 30 transplanted corneas of 30 patients who underwent optical PKP for various indications, while group 2 included 30 transplanted corneas of 30 patients who underwent therapeutic PKP for unhealed, resistant infectious keratitis. Specular microscopy was performed for all patients at the 3-, 6-, and 12-month follow-up visits using Nidek CEM-530 specular microscopy. Postoperative clinical examinations were performed at the same follow-up visits to detect graft rejection. Results: There were no statistically significant differences between the groups concerning the postoperative timing of graft clarity or the rate of ECL at 3- and 6-months postoperatively; however, the rate of ECL was significantly greater in group 2 than in group 1 at 12-months postoperatively (P = 0.03), although the difference was small from a clinical point of view. Moreover, there was no statistically significant difference between the groups in terms of the graft rejection rate. Conclusions: Therapeutic PKP results were comparable to optical PKP with respect to graft viability, the rate of ECL, and the rate of graft rejection 1 year after grafting.

Revisiting the Robustness of Pentacam HR Indices Against Soft Contact Lens Wear.

PURPOSE: To evaluate various selected Pentacam HR indices in a cohort of soft contact lens (SCL) wearers before and after SCL discontinuation. METHODS: Ninety right eyes of 90 SCL wearers (group 1) were compared to healthy controls (group 2). For group 1 eyes, Pentacam HR images were captured within one hour of SCL removal and after one month of discontinuation. The evaluated indices included curvature, elevation, and pachymetric parameters. RESULTS: Elevation indices and two pachymetric indices (central corneal thickness and thinnest corneal thickness) did not show significant differences, either between the two groups or in group 1 after SCL discontinuation. Some pachymetric indices (average and maximum corneal pachymetry progression indices, and maximum Ambrosio's relational thickness index) showed statistically significant (P-value <0.001), yet clinically irrelevant differences. Contrarily, changes in curvature indices were both statistically significant (P-value <0.001) and clinically relevant. CONCLUSION: From a clinical point of view, many elevation and pachymetric indices are robust against SCL wear, and can be relied upon for corneal ectasia screening of SCL wearers, even without abstaining from wearing SCLs.

Introduction of longstanding complicated sulcus intraocular lens into the intact capsular bag.

AIM: To propose a surgical technique that successfully reopened the empty and intact capsular bag after long periods of closure, with repositioning of the intraocular lens (IOL) from the ciliary sulcus into its preferred habitat inside the capsular bag. METHODS: This is a case series, prospective, and interventional study. The technique was first performed on an aphakic high myope with a closed posterior capsule for 18y. Afterwards, five patients with recurrently displaced sulcus IOLs for a range of 1mo to 7y were performed for the same technique. During surgery, identifying a "telltale white line" was an important landmark for detecting the site of major adhesions between the edge of the capsulorhexis and the posterior capsule. These adhesions were freed using combined manual and viscoelastic dissection, followed by an easier freeing of adhesions along the whole capsular bag. The IOL was safely implanted, exchanged, or introduced from the sulcus into the fibrotic and closed capsular bag. Patients were followed up for a period ranging from 6 to 17mo postoperatively. RESULTS: All the patients experienced a remarkable improvement in their subjective refraction. Slit lamp examination showed a postoperative centralized IOL in the bag. The follow up visits confirmed visual and IOL stability. CONCLUSION: This newly-introduced surgical technique facilitates the reopening of the empty yet intact capsular bag that has been closed by fibrotic proliferations, with secured implantation of the IOL inside the capsular bag. Patients with inadvertent implantation of IOLs into the ciliary sulcus, yet having an intact capsular bag, can benefit from this technique.

Normative Values of Corneal Spherical Aberration, Pupil Size, and Other Key Refractive and Topographic Parameters in a Large Cohort of Egyptian Cataract Surgery Candidates.

PURPOSE: To determine the spherical aberration, pupil size, and other key refractive and topographic parameters in a large cohort of Egyptian cataract surgery candidates, and to investigate any existent relations between the spherical aberration and other possibly related parameters. METHODS: This is a cross-sectional, descriptive study that was conducted at Ain Shams University Hospitals, Cairo, Egypt. The study was performed on the right eyes of 1658 cataract surgery candidates. The mean corneal spherical aberration [Z4] and the pupil diameter, both photopic [P. Pupil] and mesopic [M. Pupil], were measured by the Oculus Keratograph 3, while the white-to-white corneal diameter [WTW], average keratometric readings [average K], axial length measurements [AL] and Anterior Chamber Depth [ACD] were all obtained from the IOL Master 500. RESULTS: The mean age was 65 ± 11.3 years. The mean value of the Z4 was +0.26 ± 0.12 µm [95% Confidence Interval "CI" (0.2570-0.2681)]. The mean values of the measured parameters were: P. Pupil 2.43 ± 0.87 mm [95% CI (2.3867-2.4700)], M. Pupil 4.61 ± 0.91 mm [95% CI (4.5683-4.6557)], WTW 11.72 ± 0.44 mm [95% CI (11.6969-11.7394)], average K 43.89 ± 1.89 D [95% CI (43.7938-43.9701)], AL 24.23 ± 2.21 mm [95% CI (24.1118-24.3166)], and ACD 3.16 ± 0.43 mm [95% CI (3.1414-3.1827)]. Weak statistically significant correlations were found between the Z4 and each of age (r = 0.049, p = 0.044), average K (r = 0.191, p < 0.001), and ACD (r = 0.122, p < 0.001). Multivariate analysis showed weaker relations between Z4 and both average K (beta coefficient= 0.091) and ACD (beta coefficient= 0.130), with an r2 = 0.024. CONCLUSION: This is the first normative data report of corneal spherical aberration [Z4], pupil size, and related refractive and topographic parameters in an old Egyptian population. The detected correlations have a weak clinical relevance and negate the existence of significant relations between the Z4 and the studied refractive and topographic parameters.

Orbscan 3 Versus Pentacam HR: Evaluating the Possible Interchangeable Use of Various Parameters.

PURPOSE: Many topography/tomography devices are available, and their interchangeable use is frequently questioned. This study aimed to compare the analogous indices of Orbscan 3 and Pentacam HR to detect whether the interchangeable use of the 2 devices is feasible. METHODS: This retrospective study was conducted at Eye World Hospital, Giza, Egypt. Displays of Orbscan 3 (Bausch & Lomb; Technolas Perfect Vision GmbH) and Pentacam HR (Oculus Optikegrate) for 660 healthy right eyes were explored for various analogous indices. Bland-Altman plots with 95% limits of agreement (LoA) were used for comparisons. RESULTS: The highest systematic error and lowest agreement existed in the front and back elevations from the best fit sphere (mean differences of 4.7 and 9.2 µm, respectively, and 95% LoA of -2.5 to 12.0 and -10.0 to 28.6, respectively). There was a relatively wide 95% LoA for each pachymetry at the corneal apex (-18 to 22 µm) and at the thinnest location (-22 to 22 µm), anterior chamber depth (-0.88 to 0.95 mm), flattest keratometry (-0.44 to 0.62 D), and steepest keratometry (-0.71 to 0.89 D). By contrast, the lowest systematic error and highest agreement existed for front and back best fit sphere radii of curvature (mean difference of 0.08 mm and 95% LoA of -0.08 to 0.24 and mean difference of 0.03 mm and 95% LoA of -0.17 to 0.23, respectively). CONCLUSIONS: This study negates the accuracy of the use of devices interchangeably regarding most parameters. Therefore, examinations with the 2 devices should not be regarded comparable.

Relation of Corneal Astigmatism with Various Corneal Image Quality Parameters in a Large Cohort of Naïve Corneas.

PURPOSE: To investigate the relationship between corneal astigmatism and corneal image quality parameters (i.e., root mean square [RMS] of some major corneal higher order aberrations [HOAs] "namely RMS of coma aberrations, RMS of trefoil aberrations, and RMS of spherical aberration [RMS-SA]" and Strehl ratio [SR] of point spread function [PSF]) by using the Sirius topographer (CSO Italia, Florence, Italy). PATIENTS AND METHODS: This cross-sectional study used the Sirius topographer to evaluate the naïve corneas of right eyes (n = 1,356). The study included three groups which were based on the mean anterior corneal astigmatism value (group 1, <1 D; group 2, 1-2 D; and group 3, >2 D). RESULTS: The corneal astigmatism showed statistically significant (yet narrow clinical) differences among the groups regarding all the examined parameters (P<0.001), except for the RMS-SA (which was statistically insignificant among the three groups). Correlation coefficients were weak between the corneal astigmatism and HOAs (correlation coefficient "r" not reaching 0.2 with any of the evaluated HOAs). CONCLUSION: Significant differences existed among the astigmatic groups regarding corneal HOAs, but the mean values were very close. The deduced relations between corneal astigmatism and corneal image quality parameters had limited clinical relevance. Thus, the corneal astigmatism should be evaluated separately from corneal image quality parameters, either when deciding between refractive correction modalities (customized versus optimized ablation techniques) or when evaluating corneal image quality of a naïve cornea.

Normative Values of Various Pentacam HR Parameters for Pediatric Corneas.

PURPOSE: To provide a normative database of several Pentacam parameters for a healthy pediatric population. METHODS: This was a retrospective study conducted at Al Watany Eye Hospitals, Cairo, Egypt. We explored the Pentacam HR database and collected the data of 432 normal right eyes of children and teenagers aged 3 to 18 years. The subjects were classified into the following 3 groups: group 1 (3-6 years, 17 eyes), group 2 (6-12 years, 126 eyes), and group 3 (12-18 years, 289 eyes). The parameters of the study cohort were compared with those of a healthy adult cohort. RESULTS: The mean age of the study cohort was 13.5 (13.2-13.8) years. There were significant differences in the following indices among the 3 age groups: anterior chamber (depth and volume), curvature (index of height decentration, index of vertical asymmetry, and center keratoconus index), elevation (front and back elevations from the best fit toric ellipsoid), and pachymetric (minimum and average pachymetric progression indices and average Ambrosio relational thickness) parameters (P values 0.001, 0.001, 0.002, 0.04, <0.001, <0.001, 0.03, 0.02, 0.01, and 0.03, respectively). CONCLUSIONS: There were significant differences in the normative values of several Pentacam indices between the pediatric and adult cohorts. Based on this finding, it is more credible to incorporate separate software cutoff values for pediatric patients. However, because there were no clinically significant differences in the parameters of the pediatric subgroups, there is no need to consider a separate cutoff value for each pediatric age range.

Pentacam HR Indices Variation in Normal Corneas with Different Corneal Thickness.

PURPOSE: To evaluate the effect of variable corneal thickness on Pentacam HR diagnostic indices in normal corneas. METHODS: Retrospective study was conducted at Al Watany Eye Hospital, Cairo, Egypt. Consecutive 160 eyes of young myopic subjects without KC were evaluated using Pentacam HR (WaveLight Allegro Oculyzer II, Erlangen, Germany). The elevation- and thickness-based indices were recorded. Enrolled corneas were categorized into three groups according to TCT quartiles; group 1 (39 eyes) included corneas with TCT <523 µm, group 2 (81 eyes) with TCT between 523 and 564 µm, while group 3 (40 eyes) enrolled TCT >564 µm. The possible effect of pachymetry on Pentacam HR indices was assessed using partial correlation tests. RESULTS: In normal corneas, back elevation from best fit sphere (BE from BFS) and that from best fit toric ellipsoid (BFTE) were the elevation indices that showed statistically significant differences among groups (P=0.013 and 0.019, respectively). Regarding pachymetric indices, maximum pachymetry progression index (PPI max) showed statistical significance (P=0.001). Partial correlations, after excluding age and refractive error effects, showed that TCT was correlated with BE from BFS, BE from BFTE, and PPI max (P=0.001, 0.001,0.002, respectively). CONCLUSIONS: Some Pentacam HR indices varied with different corneal thickness in normal corneas. This necessitates inclusion of pachymetric subgroups in the normative database. The use of the more robust indices (average pachymetry progression index and front elevations) is recommended in relatively thin or thick corneas.