Search

Purpose: To compare the corneal biomechanical parameters in healthy corneas with symmetric and asymmetric bow-tie topographic patterns., Methods: In this cross-sectional study, 144 eyes were divided based on inferior-superior asymmetry value (I-S) into symmetric (zero I-S: - 0.50 to + 0.50 D) and asymmetric bow-tie topographic patterns with inferior (positive I-S: + 0.51 to + 1.4 D) or superior (negative I-S: - 2.5 to - 0.51 D) steepening. The biomechanical assessment was performed using Corvis ST and ocular response analyzer (ORA). A general linear model univariate analysis was used to compare the parameters, while the central corneal thickness, intraocular pressure, and age were considered covariates., Results: Only the peak distance (PD) at the highest concavity phase (P = 0.007) and tomographic biomechanical index (TBI, P = 0.001) showed statistically significant differences between the three groups. For TBI, this difference was statistically significant between the positive I-S group separately with the zero I-S group (P < 0.001), and with the negative I-S group (P = 0.022). For PD, the significant difference was between the negative I-S group separately with zero I-S (P = 0.019), and positive I-S groups (P = 0.018). There was a statistically significant correlation between the I-S value with PD (r = 0.281, P = 0.001) and TBI (r = 0.170, P = 0.044)., Conclusions: Most corneal biomechanical parameters are not statistically significant compared to the zero I-S group. However, superior steepening is associated with a stiffer response based solely on the shorter PD values seen in this group, and the group with the inferior steepening shows the highest or more suspicious values based on TBI., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Abstract: The advent of refractive surgery and corneal cross-linking for ectatic disease has further highlighted the need to recognize early or subclinical ectatic disease. Historical systems depend on anterior corneal changes that occur late in the disease course and are commonly associated with visual loss. Tomographic imaging allows for the acquisition of posterior corneal surface data and corneal thickness distribution. This led to the development of modalities to diagnose early or subclinical keratoconus and to screen patients for refractive surgery.This article reviews the modern methods for assessing changes in posterior corneal surface and pachymetric distribution, now accepted by the major cornea societies to be the hallmarks of ectatic disease. Screening tools utilized by the commonly used tomographic imaging devices are discussed, and the difference between screening for ectasia and diagnosing keratoconus is highlighted. The Belin ABCD staging and classification system and the ABCD Progression Display are reviewed as a new grading and monitoring system that can be used for earlier intervention and prevention of visual loss in keratoconus., Competing Interests: M. W. Belin serves as a consultant to OCULUS GmbH. He receives no royalties for any of the software mentioned in this article. The remaining authors have no conflicts of interest to disclose., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Purpose : To compare the corneal cone location on different maps and instruments, and their agreements, with elevation maps. Methods : In 90 left eyes with bilateral keratoconus, the apex of cone location was determined based on the maximum simulated keratometry (Kmax) location on the anterior sagittal curvature map by Pentacam HR, the maximum curvature on the mean curvature map by ATLAS 9000, most elevated point of the island of positive elevation relative to the best fit sphere on the front and back corneal elevation maps by Pentacam HR, and thinnest point on the thickness map by Pentacam HR and Orbscan, and the thinnest points on pachymetry and epithelial thickness maps by RTVue OCT. Results : There was a significant difference among the location on different maps along the x - and y -axes ( p < .001). The lowest agreement with the cone apex on both front and back elevation maps was for the anterior sagittal curvature map and the highest agreement for the Pentacam thickness map. The majority of keratoconus cone apexes were displaced in the inferotemporal direction on the different maps except for the epithelial thickness maps. Conclusions : Despite the variability between different devices and methods; the thickness map on the Pentacam HR showed the highest correlation with the front and back elevation maps, while the RTVue epithelial thickness map showed the poorest correlation. Based on this study, epithelial thickness maps and anterior curvature maps should be utilized with caution to determine the location of the cone.

Before the advent of modern tomographic imaging and corneal cross-linking (CXL), diagnosis and treatment of ectatic disease were limited to disease severity where changes on the anterior corneal surface lead to visual complaints. Rigid contact lenses and/or penetrating keratoplasty addressed late stage disease, as identifying early or subclinical disease was not possible, or its need appreciated. The emergence of CXL as a viable treatment to alter the natural progression of keratoconus heightened the need for improved diagnostics.Several methods have been described in the literature to evaluate and document progression in keratoconus, but there has been no consistent definition of ectasia progression. Newer imaging techniques (ie, tomography) allowed the detection of earlier ectatic disease, before visual loss and subjective complaints. The Belin ABCD classification/staging system was introduced on a Scheimpflug imaging system [Pentacam, (Oculus GmbH, Wetzlar, Germany)] to address previous shortcomings. The ABCD system utilizes 4 parameters: Anterior ("A") and posterior ("B" for Back) radius of curvature taken from a 3.0 mm optical zone centered on the thinnest point, "C" is minimal Corneal thickness, and "D" best spectacle Distance visual acuity. The first 3 parameters (A, B, C) are machine-generated objective measurements that can be used to determine progressive change.The staging system is not limited to a specific commercial entity and can be incorporated in any tomographic imaging system. The ABCD Progression Display graphically displays each parameter and shows when statistical change above measurement noise is reached. This should allow the clinician the ability to diagnose progressive disease at a much earlier stage than was previously possible, with the confidence that earlier intervention could prevent visual loss.

Purpose: To investigate the changes in corneal backward scattering using Scheimpflug tomography (densitometry) 6 months after intrastromal corneal ring segments (Keraring) implant for keratoconus and to correlate with clinical results., Methods: Along with standard ophthalmic examination, Scheimpflug tomography using Pentacam HR was performed to document corneal densitometry and corneal shape. A densitometry map was displayed using grayscale units (GSUs) ranging from 0 to 100 (minimum to maximum light scattering) in 4 concentric annuluses: central 2-, 2- to 6-, 6- to 10-, 10- to 12-, and total 12-mm corneal diameter and at 3 different depths: anterior 120 μm, posterior 60 μm, middle (varying accordingly to the total thickness), and total thickness., Results: The changes in mean corneal densitometry values for anterior, central, and posterior layers were 3.82 ± 3.13, 2.70 ± 1.78, and 1.68 ± 1.52 GSU, respectively, and for annuluses of 0 to 2, 2 to 6, 6 to 10, and 10 to 12 mm were 2.96 ± 2.60, 4.53 ± 2.28, 2.09 ± 1.74, and 0.45 ± 3.93 GSU, respectively. The mean values increased for all corneal layers (P < 0.05), except in the peripheral 10- to 12-mm annulus (P> 0.05). The highest increase was in the annulus 2 to 6 mm of the anterior layer (5.72 ± 3.70 GSU). Changes in the mean densitometry showed a significant correlation with the mean of average keratometry changes only for the front corneal surface and changes in the Q-values for both corneal surfaces in the 2- to 6-mm annulus for all layers., Conclusions: Significant increase in the corneal densitometry mainly in the anterior 2- to 6-mm annulus of the cornea is associated with the position of the ring segment implant. More studies are needed to elucidate the relevance of such findings.

Purpose: To investigate descriptions and inclusion criteria of keratoconus used in randomized trials assessing the efficacy of surgical and nonsurgical interventions., Methods: Systematic review: we searched (Pre-)Medline and the Cochrane Library from inception until December 2018 and checked the reference lists of included articles and reviews. We included randomized trials assessing the efficacy of any kind of keratoconus treatment. No language restrictions were imposed. We assessed articles against the inclusion criteria, extracted relevant data including any kind of keratoconus description, and examined the methodological quality., Results: Searches retrieved 459 nonduplicate records, and we included 57 randomized controlled trials investigating 9 different surgical interventions with the most used primary outcome measure being maximum keratometry. Only 15 (26.3%) described eligibility parameters regarding keratoconus staging/classification, of which 12 studies used the Amsler-Krumeich classification. Eleven studies were published before 1997 (before publication of the Consolidated Standards of Reporting Trials statement), and none of these described the use of a classification. From 1997 onward, 15 of 46 studies (32.6%) described the incorporation of a classification system (P = 0.051). The average methodological quality of included trails was modest., Conclusions: The evidence from randomized trials, even after introduction of the Consolidated Standards of Reporting Trials statement, remains ill-formed regarding a careful definition of keratoconus. This is unfortunate because imprecisions regarding the specification of included patients preclude clinicians to assess applicability, that is, the extent to which they can use inferences drawn from study participants regarding efficacy and adverse events in the care of individual patients.

Objective: To assess the anatomical changes produced by implantation of the complete intracorneal ring (MyoRing; DIOPTEX, GmbH, Linz, Austria) on the different corneal anatomical layers as measured by the ABCD keratoconus staging system 6 months after operation., Methods: Seventeen eyes of 17 keratoconic patients implanted with MyoRing using the femtosecond laser were assessed preoperatively and postoperatively. Distance uncorrected visual acuity and distance corrected visual acuity (DCVA), refraction, and Scheimpflug tomography with Pentacam HR were determined for each patient. The 4 ABCD parameters were recorded, which include the anterior and posterior radius of curvature from a 3.0-mm optical zone centered on the thinnest point (TP) (A & B, respectively), the thinnest corneal thickness (C), and DCVA (D)., Results: Statistically significant improvement (preoperatively vs. postoperatively) in the DCVA (0.40±0.21 vs. 0.67±0.20 in decimal notation, P=0.001) associated with significant flattening effect was observed in both anterior (6.02±0.40 vs. 7.18±0.54 mm, P<0.001) and posterior (4.49±0.41 vs. 4.66±0.40 mm, P=0.001) radius of curvature. There was no significant change in the corneal thickness at the TP (P=0.981). The largest magnitude of change occurred on the anterior surface as measured by the "A" parameter. The average ABCD keratoconus staging before MyoRing implantation was A4B4C2D2 and changed to A1B4C2D1 6 months after ring implantation., Conclusion: Despite the placement of MyoRings in the posterior one-third of the cornea, the greatest changes in curvature occurred on the anterior corneal surface. The ABCD classification and staging system allows for a differential assessment of the different anatomical layers and may prove useful in better understanding of the geometric (structural) and functional changes after MyoRing implantation, as well as with other corneal procedures.

Purpose: We aim to design two sampling methods, the grid and sectoral methods, to provide more precise detection of focal corneal scar changes with time following pterygium excision with the Pentacam imaging system., Methods: This is a retrospective study of our previous prospective observational case series. Thirty patients underwent primary pterygium excision with adjuvant topical mitomycin-C application were followed up and imaged with Pentacam system at postoperative weeks 1, 4, 12 and month 18. Grid and sectoral methods were used to sample density changes (in grayscale units, GSU) over the scarred areas as well as the clear pole of the same cornea., Results: Using the grid method, the average corneal densities were 39.4, 37.1, 36.7 and 34.7 GSU at postoperative 1, 4, 12 weeks and 18 months, respectively. On the other hand, using the sectoral method, the average corneal densities were 35.3, 33.3, 32.5 and 31.9 GSU at postoperative 1, 4, 12 weeks and 18 months, respectively. Paired t tests achieved statistical significance when comparing all follow-up time points to first postoperative visit. A statistically significant effect of time on the average density was shown on ANOVA (p < 0.001) using both analyses over the scarred areas, but not over the clear pole of the same cornea (p > 0.05)., Conclusion: Our novel approach to monitor corneal density changes using the grid or sectoral sampling methods seemingly enhances the power in monitoring density changes in corneal scars when compared to conventional total-diameter average densitometry.

Purpose: To improve the detection of corneal ectasia susceptibility using tomographic data., Design: Multicenter case-control study., Methods: Data from patients from 5 different clinics from South America, the United States, and Europe were evaluated. Artificial intelligence (AI) models were generated using Pentacam HR (Oculus, Wetzlar, Germany) parameters to discriminate the preoperative data of 3 groups: stable laser-assisted in situ keratomileusis (LASIK) cases (2980 patients with minimum follow-up of 7 years), ectasia susceptibility (71 eyes of 45 patients that developed post-LASIK ectasia [PLE]), and clinical keratoconus (KC; 182 patients). Model accuracy was independently tested in a different set of stable LASIK cases (298 patients with minimum follow-up of 4 years) and in 188 unoperated patients with very asymmetric ectasia (VAE); these patients presented normal topography (VAE-NT) in 1 eye and clinically diagnosed ectasia in the other (VAE-E). Accuracy was evaluated with ROC curves., Results: The random forest (RF) provided highest accuracy among AI models in this sample with 100% sensitivity for clinical ectasia (KC+VAE-E; cutoff 0.52), being named Pentacam Random Forest Index (PRFI). Considering all cases, the PRFI had an area under the curve (AUC) of 0.992 (94.2% sensitivity, 98.8% specificity; cutoff 0.216), being statistically higher than the Belin/Ambrósio deviation (BAD-D; AUC = 0.960, 87.3% sensitivity, 97.5% specificity; P = .006, DeLong's test). The optimized cutoff of 0.125 provided sensitivity of 85.2% for VAE-NT and 80% for PLE, with 96.6% specificity., Conclusion: The PRFI enhances ectasia diagnosis. Further integrations with corneal biomechanical parameters and with the corneal impact from laser vision correction are needed for assessing ectasia risk., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Objective: To investigate the visual and anatomical outcomes of Boston keratoprosthesis (Kpro) type 1 reimplantation., Design: Subgroup analysis of multicentre prospective cohort study., Participants: Of 303 eyes that underwent Kpro implantation between January 2003 and July 2008 by 1 of 19 surgeons at 18 medical centres, 13 eyes of 13 patients who underwent reimplantation of Boston Kpro type 1 were compared with 13 eyes of 13 diagnosis-matched patients who underwent initial implantation., Methods: Forms reporting preoperative, intraoperative, and postoperative parameters were prospectively collected and analyzed. Main outcome measures were Kpro retention and logMAR visual acuity., Results: After a mean follow-up time of 17.1 ± 17.6 months, the retention of both initial and repeat Kpro implantation was 92.3% (12/13 in both groups), and 62% of initial implantation and 58% of repeat implantation eyes achieved visual acuity better than 20/200. Vision worse than 20/200 was often due to glaucoma or posterior segment pathology. Best-recorded logMAR visual acuity was significantly improved postoperatively in both groups (p < 0.001), and there was no statistically significant difference in final logMAR visual acuity between the 2 groups (p = 0.89). Sterile keratolysis (n = 4) and fungal infection (n = 5) were the most common causes of initial Kpro failure in the repeat Kpro group. The single failure in the repeat Kpro implantation group was due to fungal keratitis, and in the control group it was related to Kpro extrusion., Conclusions: Repeat Kpro implantation is a viable option after failed initial Kpro, with visual and anatomical outcomes comparable to those of initial procedures., (Copyright © 2018 Canadian Ophthalmological Society. Published by Elsevier Inc. All rights reserved.)

Purpose: To report 5 cases of advanced unilateral keratoconus documented by sequential tomographic evaluation., Methods: Retrospective review over a 10-year period at a single practice identifying patients with unilateral keratoconus by advanced imaging throughout the follow-up period., Results: Five patients were identified with progressive keratoconus in 1 eye and no changes in the fellow eye based on full tomographic evaluation and analysis of both anterior and posterior corneal surfaces and corneal thickness with a mean follow-up period of 59 months (range 39-86)., Conclusions: Keratoconus is believed to be a bilateral disease that can present asymmetrically. We present 5 cases that appear to be true unilateral keratoconus with no associated mechanical environmental factors.

Purpose: To evaluate long-term changes in mean keratometry, astigmatism, true net power (TNP), and total corneal refractive power (TCRP) of corneas after primary pterygium excision., Methods: This is a prospective observational series conducted at a tertiary teaching hospital eye center in Hong Kong. A total of 31 eyes of 31 patients with primary pterygium excision were included. Patients with recurrent or double-headed pterygia or a history of corneal scars from previous trauma, infection, or surgery were excluded. Data were collected prospectively at postoperative weeks 1, 4, 12, and month 18., Results: Mean keratometry of the anterior cornea was 44.3 diopters (D) [95% confidence interval (CI): 43.6-44.9 D] at week 1, 44.3 D (95% CI: 43.6-44.9 D, standard error = 0.3) at week 4, 44.3 D (95% CI: 43.7-44.9 D) at week 12, and 44.1 D (95% CI: 43.5-44.7 D) at month 18. Mean astigmatism of the anterior cornea was 1.1 D (95% CI: 0.7-1.4 D), 1.0 D (95% CI: 0.7-1.3 D), 0.9 D (95% CI: 0.6-1.1 D), and 1.0 D (95% CI: 0.7-1.3 D) at postoperative 1, 4, 12 weeks, and 18 months, respectively. Mean keratometry, astigmatism of the anterior and posterior cornea, TNP and TCRP at 2.0-mm, 3.0-mm, 4.0-mm rings and zones remained unchanged on all follow-up visits (P = 1 for all comparisons)., Conclusions: Keratometric values including TNP and TCRP were stable as soon as 1 week after pterygium excision. This information might help clinicians in planning subsequent intraocular surgery that requires biometric assessment for intraocular lens implantation.

Purpose: To evaluate the long-term change in average corneal densities at 18 months after primary pterygium excision with topical adjuvant mitomycin-C application, particularly the relationship between anterior and posterior corneal layer densities., Methods: Prospective observational case series. Patients were imaged with the Pentacam at 18 months after their surgery. Average corneal densities were the primary outcome and were compared with postoperative weeks 1, 4, and 12 data using paired t test., Results: In all, 31 eyes of 31 patients were recruited. Mean age at time of operation was 62.0 ± 9.4 years. Mean best-corrected logarithm of the minimal angle of resolution visual acuity at 18 months was 0.14. The mean total anterior, central, and posterior average corneal densities were 30.6, 25.9, and 20.5 respectively. Compared with postoperative week 1 data, the anterior layer was reduced by 12.7% (P = 0.0144); however, there was no significant change in the central and posterior layers (P = 0.5353 and 0.0858, respectively). Subgroup analyses did not support the use of a 10- to 12-mm annulus as opposed to total-diameter data, and density reduction effect at 18 months from week 12 and week 1 seemed to be stronger in males (P = 0.0074 and 0.0042, respectively)., Conclusions: Anterior corneal scars continued to diminish in density with time. Previous finding of a significant increase in posterior layer density at postoperative week 12 is likely not a result of optical phenomenon caused by a less dense anterior layer. Sex difference in terms of scar remodeling may be present.

Purpose: To report logarithm of the minimal angle of resolution (logMAR) visual outcomes of the Boston keratoprosthesis type 1., Design: Prospective cohort study., Methods: Preoperative, intraoperative, and postoperative parameters of 300 eyes of 300 patients who underwent implantation of a Boston keratoprosthesis type 1 device between January 2003 and July 2008 by 1 of 19 surgeons at 18 medical centers were collected., Results: After an average of 17.1 ± 14.8 months, visual acuity improved significantly (P < .0001) to a mean final value of 0.89 ± 0.64 (20/150). There were also significantly fewer eyes with light perception (6.7%; n = 19; P < .0001), although 3.1% (n = 9) progressed to no light perception. There was no association between age (P = .08), sex (P = .959), operative side (P = .167), or failure (P = .494) and final visual acuity. The median time to achieve 20/200 visual acuity was 1 month (95% confidence interval 1.0-6.0) and it was retained for an average of 47.8 months. Multivariate analysis, controlling for preoperative visual acuity, demonstrated 2 factors associated with final visual outcome: chemical injury was associated with better final vision (P = .007), whereas age-related macular degeneration was associated with poorer vision (P < .0001)., Conclusions: The Boston keratoprosthesis type 1 is an effective device for rehabilitation in advanced ocular surface disease, resulting in a significant improvement in visual acuity. Eyes achieved a mean value of 20/150 (0.89 ± 0.64 logMAR units) after 6 months and this was relatively stable thereafter. The best visual prognosis is observed in chemical injury eyes, whereas the worst prognosis is in aniridia, although the latter has limited visual potential., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Purpose: Corneal densitometry is an inherent feature of the Pentacam device. We aim to assess the changes in corneal scar density with serial Scheimpflug images following primary pterygium excision with topical application of mitomycin-C., Methods: We recruited patients who underwent primary, single-headed pterygium excision with topical adjuvant mitomycin-C. Scheimpflug images were taken at postoperative weeks 1, 4, and 12, and all patients received topical corticosteroid and antibiotic treatment for at least 4 weeks postoperatively. Corneal scar densities were generated by the software for analysis. Secondary outcome measures included intraocular pressures and pterygium recurrence at the end of 12 weeks. Changes in corneal densities between weeks 12, 4, and 1 were calculated., Results: We recruited 31 eyes of 31 patients, of whom 16 were male patients and 15 were female patients, with 19 left and 12 right eyes. Mean age at operation was 62.0 ± 9.4 years. Mean reduction in density of the anterior 120 μm of cornea was -3.07 [95% confidence interval (CI), -6.600 to 0.460] and -3.455 (95% CI, -6.787 to -0.122) at postoperative 4 and 12 weeks, respectively, and mean reduction percentage was -4.7% (95% CI, -10.7% to 1.3%) and -6.3% (95% CI, -11.8% to -0.7%), respectively. No steroid response or pterygium recurrence was reported., Conclusions: Corneal densitometry is an objective measure to detect scar changes in zones and layers. The overall reduction of density was evident at 12 weeks postoperatively. These results might serve as baseline figures for future studies in assessing modulation of corneal scars over time.

Background: Despite extensive knowledge regarding the diagnosis and management of keratoconus and ectatic corneal diseases, many controversies still exist. For that reason, there is a need for current guidelines for the diagnosis and management of these conditions., Purpose: This project aimed to reach consensus of ophthalmology experts from around the world regarding keratoconus and ectatic diseases, focusing on their definition, concepts, clinical management, and surgical treatments., Methods: The Delphi method was followed with 3 questionnaire rounds and was complemented with a face-to-face meeting. Thirty-six panelists were involved and allocated to 1 of 3 panels: definition/diagnosis, nonsurgical management, or surgical treatment. The level of agreement considered for consensus was two thirds., Results: Numerous agreements were generated in definitions, methods of diagnosing, and management of keratoconus and other ectatic diseases. Nonsurgical and surgical treatments for these conditions, including the use of corneal cross-linking and corneal transplantations, were presented in a stepwise approach. A flowchart describing a logical management sequence for keratoconus was created., Conclusions: This project resulted in definitions, statements, and recommendations for the diagnosis and management of keratoconus and other ectatic diseases. It also provides an insight into the current worldwide treatment of these conditions.

Scheimpflug cross-sectioning anterior segment imaging offers significant advantages over traditional placido based curvature analysis and ultrasound pachymetry. The accurate measurement of both the anterior and posterior corneal surfaces and the anterior and posterior lens allows for the creation of a three-dimensional reconstruction of the anterior segment. Changes on both the posterior cornea and/or corneal thickness map are earlier indicators of ectatic change than would otherwise be identifiable with only anterior curvature and ultrasonic pachymetry. Scheimpflug imaging also covers significantly more of the cornea than was possible with placido based devices. This added coverage is critical in the proper diagnosis of peripheral diseases such as pellucid marginal degeneration (PMD).

Objective: To report the retention rate of the Boston keratoprosthesis type 1 and to identify risk factors for keratoprosthesis loss., Design: Cohort study., Participants: A total of 300 eyes of 300 patients who underwent implantation of the Boston keratoprosthesis type I device between January 2003 and July 2008 by 19 surgeons at 18 medical centers., Methods: Forms reporting preoperative, intraoperative, and postoperative parameters were prospectively collected and subsequently analyzed at a central data collection site., Main Outcome Measures: Keratoprosthesis retention., Results: A total cumulative number of 422 life-years of device implantation are included in this analysis. The average duration of follow-up was 17.1 ± 14.8 months, with a range of 1 week to >6.1 years. Ninety-three percent of the 300 Boston keratoprosthesis implants were retained at their last follow-up, corresponding to a retention time of 396 patient-years or 1.42 years/keratoprosthesis. The probability of retention after 1 year and 2 years was 94% and 89%, respectively. During the study period, 21 (7%) eyes failed to retain the device; the reasons for keratoprosthesis loss include sterile keratolysis (9), fungal infections (8), dense retroprosthetic membranes (3), and bacterial endophthalmitis (1). Multivariate analysis demonstrated 3 independent risk factors for keratoprosthesis loss: autoimmune cause (hazard ratio [HR], 11.94; 95% confidence interval [CI], 3.31-43.11), ocular surface exposure requiring a concomitant tarsorrhaphy (HR, 3.43; 95% CI, 1.05-11.22), and number of prior failed penetrating keratoplasties (HR, 1.64; 95% CI, 1.18-2.28)., Conclusions: The Boston keratoprosthesis type 1 seems to be a viable option for eyes that are not candidates for penetrating keratoplasty (PK). Ocular surface disease due to an autoimmune cause demonstrated the lowest retention rate., Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article., (Copyright © 2013 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Objective: The purpose of this study was to identify possible risk factors for retroprosthetic membrane (RPM) development in a large, multicenter cohort of patients receiving a Boston type 1 keratoprosthesis., Design: Cohort study., Participants: The final analysis included 265 eyes of 265 patients who underwent implantation of a Boston keratoprosthesis type I device between January 2003 and July 2008 by 1 of 19 surgeons at 18 medical centers., Methods: Forms reporting preoperative, intraoperative, and postoperative parameters were prospectively collected and subsequently analyzed at a central data collection site., Main Outcome Measures: The primary outcome was the presence or absence of an RPM during the follow-up period., Results: The average age of patients was 63.3±19.1 years, 48.5% of the patients were female, and 52.5% of procedures were performed on the right eye. The mean follow-up time was 17.8±14.9 months. The majority (85.4%; n = 222) had undergone an average of 2.2±1.2 (range, 1-8) penetrating keratoplasties before keratoprosthesis implantation, and 38 eyes (14.6%) received a primary keratoprosthesis. The overall RPM formation rate was 31.7% (n = 84). The most significant risk factor for RPM development was infectious keratitis (as a surgical indication for keratoprosthesis surgery itself), resulting in a rate of RPM formation of 70.6%. As an independent risk factor, the hazard ratio (HR) of RPM development in these eyes was 3.20 (95% confidence interval, 1.66-6.17). Aniridia was also an independent risk factor for RPM development (HR, 3.13; 95% confidence interval, 1.10-8.89)., Conclusions: Formation of RPM is a common complication of keratoprosthesis surgery, occurring in approximately one-third of cases. Eyes at the highest risk of RPM development are those receiving corneal replacement for infectious keratitis and aniridia., (Copyright © 2012 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Purpose: To describe pachymetric progression indices (PPI) of the Pentacam HR (Oculus Optikgeräte GmbH) and the concept of relational thickness, and to test their accuracy for differentiating keratoconic and normal corneas compared with single-point thickness values., Methods: One hundred thirteen individual eyes randomly selected from 113 normal patients and 44 eyes of 44 patients with keratoconus were studied using the Pentacam HR by acquiring central corneal thickness (CCT), thinnest point (TP), position of the TP and PPI at minimal (PPI Min) and maximal (PPI Max) meridians, and the average (PPI Ave) of all meridians. Relational thickness parameters were calculated as the ratios of TP and CCT and PPI values. Mann-Whitney U test assessed differences in groups for each variable. Receiver operating characteristic (ROC) curves were calculated for all variables and pairwise comparisons were performed., Results: Statistically significant differences were noted between normal and keratoconic eyes for all parameters (P<.001), except for horizontal position of TP (P=.79). The best parameters, named Ambrósio's Relational Thickness (ART), were ART-Ave (TP/PPI Ave) and ART-Max (TP/PPI Max) with areas under the ROC curves of 0.987 and 0.983, respectively. The best cutoffs were 424 μm and 339 μm for ART-Ave and ART-Max, respectively. Pachymetric progression indices and ART had a greater area under the curve than TP and CCT (P<.001); TP (0.955) had a greater area under the curve than CCT (0.909; P=.002)., Conclusions: Tomographic-derived pachymetric parameters were better able to differentiate normal and keratoconic corneas than single-point pachymetric measurements. Further studies are needed to evaluate the role of tomography in identifying early forms of ectasia as well as ectasia risk among LASIK candidates., (Copyright 2011, SLACK Incorporated.)

Purpose: To examine whether clinically significant differences exist in corneal elevation data from a sampling of countries worldwide., Setting: International multicenter., Design: Evaluation of diagnostic test or technology., Methods: One randomly selected eye of normal adults from 8 countries spanning 6 continents was examined using the Pentacam Eye Scanner. Anterior and posterior elevations were measured at the apex and thinnest point. Differences between countries were assessed by Kruskal-Wallis. Normative thresholds were defined according to the Tukey method., Results: The study examined 1 eye of 555 patients. Median elevations were similar across countries. Upper limits of normal for collective international data were 3.5 μm, 6.0 μm, 7.5 μm, and 13.5 μm at the anterior apex, anterior thinnest point, posterior apex, and posterior thinnest point, respectively. These and country-specific thresholds were similar to normal values from previous data; however, country-specific thresholds flagged additional eyes in China, Egypt, and India. Those thresholds were 4.5 μm at the anterior thinnest point (China and Egypt), 7.4 μm at the posterior apex (India), and 11.0 μm and 12.0 μm at the posterior thinnest point (China and Egypt, respectively)., Conclusions: In general, international variations were clinically insignificant; thus, current screening guidelines maintained their applicability. Notable exceptions were China, Egypt, and India, where country-specific thresholds may better reflect the test populations and minimize potential false negative results from screening., Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. Additional disclosures are found in the footnotes., (Published by Elsevier Inc.)

Purpose: To discuss the implications of the current nomenclature and use of current diagnostic modalities on the classification and treatment of pellucid marginal degeneration and keratoconus., Design: Perspective analysis of the literature., Methods: Analysis of published reports on the various treatment methods for pellucid marginal degeneration and keratoconus, and the technologies used in these studies to support the diagnosis and classification of these ectatic disorders., Results: Many studies exploring the different treatment modalities for pellucid marginal degeneration and keratoconus rely mainly on anterior curvature maps to establish the diagnosis of these ectatic disorders, and either do not utilize or disregard information provided by pachymetric maps and posterior elevation maps. In addition, the interchangeability of the nomenclature used to describe these disorders in the literature makes it even more difficult for the clinician to determine the applicability of the results to their patient population., Conclusions: We propose that future studies minimally include anterior and posterior elevation maps, anterior curvature topography, and full pachymetric maps. This will allow practitioners a better understanding of the study population, and allow them to ascertain when and in whom the treatment modality being explored may be applicable., (Published by Elsevier Inc.)

Purpose: To characterize central corneal thickness, curvature, and posterior surface elevation in eyes with Fuchs dystrophy that underwent Descemet membrane endothelial keratoplasty (DMEK) for endothelial decompensation and to compare these characteristics with those in normal eyes., Methods: Pre- and postoperative corneal tomography was prospectively evaluated using Pentacam (Oculus Optikgeräte GmbH) imaging on 29 eyes with Fuchs dystrophy treated with DMEK. Results were compared with data from a separate cohort of 198 normal eyes., Results: In the Fuchs cohort, the mean preoperative central corneal thickness was 656 μm (range: 574 to 731 μm). This significantly exceeded the mean thickness of 542 μm in the normal cohort (range: 439 to 611 μm, P<.0001) although the cohort thickness ranges overlapped. One month after DMEK, mean central corneal thickness decreased significantly to 539 μm (range: 465 to 669 μm, P<.0001) with no further significant decrease between 1 and 3 months after DMEK (mean difference = -4 μm, P=.39). In the Fuchs cohort, keratometry (average Sim K and delta K) did not change significantly after DMEK (P=.41 and P=.44, respectively); pre- and postoperative values were comparable to those in the normal cohort. The mean forward displacement of the posterior surface increased by 69 μm 1 month after DMEK (P<.0001) without further significant change between 1 and 3 months., Conclusions: After DMEK, central corneal thickness in the Fuchs dystrophy cohort decreased significantly and the posterior corneal surface displaced forward, without significant change in anterior keratometric values or keratometric astigmatism. The preoperative central corneal thickness range in eyes with confluent central guttata overlapped the range in normal corneas., (Copyright 2010, SLACK Incorporated.)

Purpose: We present a case of advanced bilateral pellucid marginal degeneration (PMD) with unilateral hydrops to show the unique properties of Scheimpflug imaging and its ability to display the clinical and topographic findings of PMD not seen on traditional placido-based topography., Methods: Case report and literature review., Results: A 51-year-old man was referred with a presumptive diagnosis of bilateral keratoconus with unilateral hydrops. Complete topographic evaluation showed a band of inferior thinning adjacent to the limbus and a Scheimpflug cross-sectional image consistent with PMD., Conclusions: We show the value of Scheimpflug-based topography and pachymetry maps to accurately depict the unique disease characteristics of PMD.

Purpose: To compare two methods of measuring central cornea thickness (CCT) in eyes that have undergone laser in situ keratomileusis (LASIK)., Design: Prospective clinical trial., Methods: The corneal thickness from 104 eyes of 53 consecutive patients undergoing the one-year follow-up after LASIK was measured with both the Pentacam (Oculus, Inc, Wetzlar, Germany) and ultrasonic pachymetry. All patients were examined at one clinical setting, where first Pentacam imaging was performed by one technician and then ultrasound pachymetry was performed by a masked second technician. The results were compared., Results: The average age of the patient population was 38 years (range, 22 to 56 years) of those who underwent the one-year follow-up examination an average of 406 days (range, 264 to 579 days) after LASIK. The mean CCT measurement was 506 +/- 29.5 microm (range, 454 to 574 microm) with the Pentacam topographer and 505 +/- 31.7 microm (range, 433 to 576 microm) with ultrasound pachymetry. The average difference (Pentacam minus ultrasound) was 1.4 +/- 10.4 microm (range, -21.8 to 23.4 microm)., Conclusions: The Pentacam's CCT measurement and that of ultrasound pachymetry show good correlation. Pentacam pachymetry may be substituted for ultrasound in the post-LASIK patient.

Purpose: To study long-term changes in posterior corneal elevation after laser in situ keratomileusis (LASIK) using Scheimpflug topography (Pentacam, Oculus, Inc.) in eyes 1 year after LASIK., Setting: Department of Ophthalmology, Albany Medical Center, and a private practice, Albany, New York, USA., Methods: One hundred two myopic eyes of 52 consecutive patients presenting for their 1-year follow-up were prospectively evaluated using the Pentacam to determine elevation changes to the posterior corneal surface between preoperative and 1-year postoperative measurements. Changes in posterior elevation were performed by comparing the best-fit sphere preoperatively and postoperatively with a fixed reference sphere determined by the central 9.0 mm preoperative cornea. Statistical and graphical analyses were performed., Results: One hundred two post-LASIK eyes (mean correction -4.33 diopters; mean ablation depth 68.70 microm; mean estimated residual bed thickness 327 microm) had a mean posterior displacement of -0.47 microm +/- 3.48 (SD) (range -10.0 to +7 microm). The mean follow-up period was 13.6 months (range 8.8 to 19.3 months)., Conclusions: In this population, no patient had significant forward protrusion of the posterior corneal surface a mean of 14 months after LASIK. The posterior cornea in post-LASIK myopic eyes was very stable. Contrary to results in previous studies, progressive changes to the posterior corneal surface did not routinely occur after LASIK performed within established parameters.

Purpose: To describe a novel topographic curvature pattern, vertical D, which was present in some keratoconus suspects. This pattern was detected retrospectively in 2 patients who developed post-LASIK ectasia and prospectively in 4 patients who had other corneal abnormalities suggestive of keratoconus., Design: Retrospective interventional case series and prospective cross-sectional study., Participants: After vertical D topographic curvature patterns were noted in 2 patients (3 eyes) who developed post-LASIK ectasia, 1168 consecutive potential refractive surgical candidates (2336 eyes) evaluated at a refractive center were screened to detect this vertical D pattern., Methods: Placido disc-based curvature topography, ultrasound pachymetry, and elevation-based Scheimpflug topography were performed on these patients., Main Outcome Measures: Corneal curvature topographic patterns, central keratometry, inferior-superior and nasal-temporal ratios, skewed radial axis value, Humphrey Atlas PathFinder corneal analysis, corneal thickness, and corneal anterior and posterior elevation., Results: Four additional patients (7 eyes) with vertical D patterns were found (prevalence, 0.34%). In addition to this vertical D pattern, these patients had central corneal thickness < 500 microm and/or posterior corneal protrusion > 20 microm or positive results on keratoconus detection analyses. The 10 eyes with the vertical D pattern had more horizontal (nasal-temporal ratio) than vertical (inferior-superior ratio) curvature asymmetry: 0.98+/-0.04 diopters versus 0.44+/-0.2 diopters (paired t test, P<0.001)., Conclusions: We propose that vertical D is a novel corneal curvature pattern reflecting horizontal asymmetry that was present in keratoconus suspect patients even if standard keratoconus analyses' results were negative.

Purpose: To report indications, practices, complications, and outcomes from the first multicenter study on the Boston Type 1 keratoprosthesis., Design: Prospective, noncomparative, interventional case series., Participants: We analyzed 141 Boston Type 1 keratoprosthesis surgical procedures, from 17 surgical sites, done from January 2003 through September 2005 in 136 eyes of 133 patients., Methods: Forms reporting 70 preoperative, intraoperative, and postoperative parameters were collected and analyzed at a central data collection site (Cornea Consultants of Albany, Albany Medical College, Albany, New York)., Main Outcome Measures: Visual acuity (VA) and keratoprosthesis survival., Results: Common preoperative diagnoses were graft rejection, in 73 eyes (54%) (average prior grafts, 2.24); chemical injury (20 eyes [15%]); bullous keratopathy (19 eyes [14%]); and herpes simplex virus keratitis (9 eyes [7%]). Additionally, 82 eyes (60%) had preoperative glaucoma. Preoperative best-corrected VA ranged from 20/100 to light perception, and was <20/200 in 96% of eyes. At an average follow-up of 8.5 months (range, 0.03-24; standard deviation, 6.1; median, 12), postoperative vision improved to > or =20/200 in 57%. Among eyes at least 1 year after the operation (62 eyes), vision was > or =20/200 in 56% of eyes and > or =20/40 in 23%. At an average follow-up of 8.5 months, graft retention was 95%. Severe visual loss or failure to improve from keratoprosthesis was usually secondary to comorbidities such as advanced glaucoma, macular degeneration, or retinal detachment., Conclusions: The Boston Type 1 keratoprosthesis seems, based on early follow-up, to be a viable option after multiple failed corneal grafts or in some situations of a poor prognosis for primary penetrating keratoplasty.

Purpose: To study the changes in posterior corneal elevation after laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) using Scheimpflug topography with the Pentacam anterior segment imaging system (Oculus, Inc.)., Setting: Department of Ophthalmology, Albany Medical Center, and a private clinical practice, Albany, New York, USA., Methods: In this prospective study, 121 consecutive myopic eyes (103 LASIK and 18 PRK) were evaluated preoperatively and postoperatively with the Pentacam to determine elevation changes in the posterior corneal surface. Changes in posterior elevation were calculated by comparing the best-fit sphere preoperatively and postoperatively to a fixed reference sphere using the central 9.0 mm preoperative cornea. Statistical and graphic analyses were performed., Results: The 103 LASIK eyes had a mean correction of -3.76 diopters (D) and a mean ablation depth of 62.1 microm. The mean estimated residual bed thickness (RBT) (329 microm) demonstrated a mean posterior displacement of 2.64 +/- 4.95 microm. The 18 PRK eyes had a mean correction of -2.69 D and a mean ablation depth of 53.2 microm. The mean estimated RBT (464 microm) had a mean posterior displacement of -0.88 +/- 4.64 microm. The difference in the mean posterior corneal displacement between the LASIK and the PRK eyes was not statistically significant (P>.05, Student t test)., Conclusions: There was no statistically significant difference in posterior corneal displacement between the LASIK and PRK patients. The changes in PRK and LASIK eyes appeared to be within acceptable measurement variation. Contrary to previous reports, ectatic changes to the posterior corneal surface did not routinely occur after LASIK surgery.

PurposeTo report logarithm of the minimal angle of resolution (logMAR) visual outcomes of the Boston keratoprosthesis type 1.DesignProspective cohort study.MethodsPreoperative, intraoperative, and postoperative parameters of 300 eyes of 300 patients who underwent implantation of a Boston keratoprosthesis type 1 device between January 2003 and July 2008 by 1 of 19 surgeons at 18 medical centers were collected.ResultsAfter an average of 17.1 ± 14.8 months, visual acuity improved significantly (P < .0001) to a mean final value of 0.89 ± 0.64 (20/150). There were also significantly fewer eyes with light perception (6.7%; n = 19; P < .0001), although 3.1% (n = 9) progressed to no light perception. There was no association between age (P = .08), sex (P = .959), operative side (P = .167), or failure (P = .494) and final visual acuity. The median time to achieve 20/200 visual acuity was 1 month (95% confidence interval 1.0-6.0) and it was retained for an average of 47.8 months. Multivariate analysis, controlling for preoperative visual acuity, demonstrated 2 factors associated with final visual outcome: chemical injury was associated with better final vision (P = .007), whereas age-related macular degeneration was associated with poorer vision (P < .0001).ConclusionsThe Boston keratoprosthesis type 1 is an effective device for rehabilitation in advanced ocular surface disease, resulting in a significant improvement in visual acuity. Eyes achieved a mean value of 20/150 (0.89 ± 0.64 logMAR units) after 6 months and this was relatively stable thereafter. The best visual prognosis is observed in chemical injury eyes, whereas the worst prognosis is in aniridia, although the latter has limited visual potential.

Purpose: To assess the reliability of successive Corvis ST® measurements (CST, Oculus, Wetzlar, Germany) in keratoconus (KC) ≥ 2 years after accelerated corneal crosslinking (9 mW/cm2, 10 min, 5.4 J/cm2) compared to untreated KC corneas. Methods: Three successive CST measurements per eye were performed in ≥ 2 years after CXL (CXLG, n = 20 corneas of 16 patients) and a control group consisting of non-operated, ABC-stage-matched KC corneas according to Belin's ABCD KC grading (controls, n = 20 corneas, 20 patients). Main outcome measures included maximal keratometry (Kmax), the Belin/Ambrósio-Enhanced-Ectasia-Deviation-Index BAD-D; the biomechanical parameters A1 velocity, deformation amplitude (DA) ratio 2 mm, Ambrósio relational thickness to the horizontal profile (ARTh), integrated radius, stiffness parameter A1 (SP-A1), and the Corvis Biomechanical Factor (CBiF, the linearized term of the Corvis Biomechanical Index). Mean values, standard deviations, and Cronbach's alpha (CA) were calculated. Results: Both groups were tomographically comparable (BAD: 11.5 ± 4.7|11.2 ± 3.6, p = 0.682, Kmax: 60.5 ± 7.2|60.7 ± 7.7, p = 0.868 for controls|CXLG, paired t-test). A1 velocity (mean ± SD: 0.176 ± 0.02|0.183 ± 0.02, p = 0.090, CA: 0.960|0.960), DA ratio 2 mm (6.04 ± 1.13|6.14 ± 1.03, p = 0.490, CA: 0.967|0.967), integrated radius (12.08 ± 2.5|12.42 ± 1.9, p = 0.450, CA: 0.976|0.976), and CBiF (4.62 ± 0.6|4.62 ± 0.4, p = 0.830, CA: 0.965|0.965) were also comparable (controls|CXLG). ARTh was significantly higher in controls (177.1 ± 59, CA: 0.993) than after CXL (155.21 ± 65, p = 0.0062, CA: 0.993) and SP-A1 was significantly higher after CXL (59.2 ± 13, CA: 0.912) than in controls (52.2 ± 16, p = 0.0018, CA: 0.912). Conclusion: ARTh and SP-A1 differed significantly between controls and CXLG. Biomechanical measurements were generally of excellent reliability in both groups. CXL seems to affect biomechanical measurements of human corneas over more than 2 years. [ABSTRACT FROM AUTHOR]

Purpose. To present the youngest age ever reported for acute corneal hydrops with total corneal edema in a child with advanced bilateral keratoconus. Methods. Patient presentation in ophthalmic clinic. The patient underwent various clinical tests and examinations including anterior segment optical coherence tomography (AS-OCT) and Scheimpflug corneal tomography. Results. A 5-year-old girl presented with uncorrected distance visual acuity (UDVA) of 0.4 in the right eye and nonmeasurable UDVA associated with severe photophobia in her left eye of a 3-day duration. Intraocular pressure using the iCare tonometer was 14 and 5 mmHg in the right and left eyes, respectively. An old corneal hydrops scar and posterior subcapsular cataract (PSC) in the right eye and a total limbus to limbus corneal hydrops in the left eye were observed on slit-lamp examinations. Scheimpflug corneal tomography was possible in the right eye but, due to excessive irregularity and scaring, was not possible in the left eye. Corneal thinning and scarring were evident in the anterior segment optical coherence tomography in the right eye and very edematous cornea associated with stromal cleft and epithelial bullae in the left eye. A management plan consisting of topical hypertonic solution and ointment was started to reduce her symptoms. Conclusion. Acute corneal hydrops may be the presenting sign of keratoconus; however, extensive hydrops involving the total cornea area at a very young age is very rare and has not been previously reported in the literature. [ABSTRACT FROM AUTHOR]

Purpose: To assess the change in corneal pachymetry after a novel epithelium-on (EpiSmart®) corneal crosslinking procedure (CXL). Methods: Eyes treated as part of the open-label, non-controlled arm of the study "Collagen Crosslinking with Ultraviolet-A in Asymmetric Corneas" (NCT01097447) were examined at baseline, 3-, 6- and 12-months post-CXL. Thinnest pachymetry readings based on Pentacam (OCULUS GmbH, Wetzlar, Germany) were recorded. Results: A total of 101 eyes met the study inclusion criteria. Thinnest pachymetric readings at baseline averaged 451 ± 50 microns. The mean (± SD) minimum thickness was 450 ± 46 microns at 3 months, 452 ± 47 microns at 6 months, and 451 ± 48 microns at 12 months post-CXL. The changes from baseline (mean ± SE) at 3, 6, and 12 months post-CXL were − 1.2 ± 1.5 microns, 0.5 ± 1.6 microns, and 0.4 ± 1.6 microns, respectively. Student's t-tests showed no statistically significant change in pachymetry from baseline for any exam period. Conclusion: This study demonstrated that, after EpiSmart® epithelium-on CXL, there was no substantial corneal thinning observable on Scheimpflug tomography out to 12 months. [ABSTRACT FROM AUTHOR]

Purpose: To assess the effectiveness of a novel treatment for patients with advanced corneal ectasia and loss of visual acuity (VA). Conductive keratoplasty (CK) is performed to improve VA followed by epithelium-on (epi-on) corneal crosslinking (CXL) to stabilize the cornea after CK. Methods: Retrospective, exploratory cohort study. Patients with keratoconus or postsurgical ectasia and best spectacle-corrected distance VA (CDVA) ≤ 20/40 were included. Conductive keratoplasty was performed (ViewPoint CK System, Refractec, Inc., Bloomington, MN); followed a day later by epi-on CXL (CXLUSA/CXLO, Bethesda, MD/CXLO Encinitas, CA). Measures included uncorrected distance visual acuity (UDVA) and CDVA, as well as refractive and tomographic measures and tomographic indices. Results: Data from 50 eyes of 45 patients were analyzed. Mean follow-up was 15.1 ± 12.2 months (range: 2 to 51). Overall, UDVA and CDVA improved postoperatively. Subjective refraction and tomographic metrics did not show consistent changes, but changes in tomographic indices were associated with treatment follow-up time. At the 1-year visit, mean UDVA significantly improved over baseline (P = 0.009) by approximately 3 lines; mean CDVA improved significantly (P = 10− 5) by approximately 2 lines. No eye lost lines of CDVA. Change in the Index of Surface Variance (ISV) was associated with treatment, and the D-Index trended over follow-up time. Conclusion: Conductive keratoplasty with a proprietary epi-on CXL treatment improved vision in patients with advanced ectasia This CK/epi-on CXL treatment offers the possibility of improved VA for patients with compromised vision due to ectasia. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the correlation between changes in maximum keratometry (Kmax) and ABC values from the ABCD Progression Display (Pentacam) in progressive keratoconus (KC) and to evaluate whether the ABC changes were able to detect progression earlier than Kmax. Setting: Humanitas Clinical and Research Center, Rozzano, Milan, Italy. Design: Retrospective study. Methods: Kmax, ABC values, and thinnest point (ThCT) were recorded at the day of corneal crosslinking (CXL) (T0) and previous follow-up (T-1). In patients without earlier progression in Kmax, follow-up examination (T-2) was used to determine whether any of the ABC parameters reached statistical significance for progression. Results: Seventy-six eyes of 63 patients scheduled for CXL with documented progression (Kmax increase of >1.00 diopter) were included. There was a significant, albeit moderate, correlation between the change in Kmax between T0 and T-1 and the change in both A ([rho] = 0.391) and B values ([rho] = 0.339). There was no significant correlation between the change in Kmax between T0 and T-1 and the change in either C or ThCT. In patients with T-2 examinations, 16 (51.6%) of 31 patients showed a statistically significant change on the ABCD progression display that was not detected with Kmax. Conclusions: This study showed a significant, but moderate, correlation between the change in Kmax and the change in A and B values in progressive KC. Moreover, more than half of the cases showed documented progression earlier with the ABCD progression display than that detected by standard Kmax changes. This study suggests possible changes in progression criteria to allow for earlier intervention. [ABSTRACT FROM AUTHOR]

Recent advances in the diagnosis and treatment of ectatic corneal disease have mandated a more modern staging system. The new Belin ABCD keratoconus staging system incorporates anterior and posterior curvature centered on the thinnest point of the cornea, thinnest pachymetry values and distance visual acuity in grades from 0-4. By including posterior curvature and thickness measurements based on the thinnest point, as opposed to apical, the new staging system better reflects anatomical changes seen in keratoconus and other ectatic diseases. [ABSTRACT FROM AUTHOR]

Aims/Purpose: Keratoconus (KC) is biomechanically characterized by a decreased resistance to deformation when compared to healthy corneas. The aim of this presentation is to give an overview about the development and clinical application of the recently introduced Homburg Biomechanical E‐Staging (BEST) for KC. Methods: The Corvis ST (Oculus, Germany) non‐contact pneumotonometer measures the corneal deformation after applying a standardized air puff. It calculates the quasi‐binary indices Corvis Biomechanical Index (CBI) and Tomographic Biomechanical Index (TBI) to separate healthy from ectatic corneas, without, however providing a biomechanical KC severity stage. The Homburg BEST based on the linearized CBI provides information about biomechanical KC severity in form of E‐stages 0 to 4, thus augmenting the existing tomographic ABCD KC classification by including corneal biomechanics. Several studies and results about the development and clinical application of the Homburg BEST are presented. Results: The Homburg BEST was developed based on two independent KC datasets (Homburg: n = 448, Milano/Rio: n = 860). Since 2022, it has been integrated into the Corvis ST software, thus providing a biomechanical KC severity and progression assessment. The software based on several individual biomechanical parameters indicates KC progression like tomographic progression parameters. However, it is influenced by corneal thickness measurements, increases within the first postoperative months after corneal crosslinking (CXL) and indicates postoperative KC stabilization more than 1 year after CXL. Intracorneal ring segment implantation permanently affects corneal thickness in the midperiphery and contributes to slightly higher postoperative BEST values. Conclusions: Although with limitations, the Homburg BEST enables a biomechanical staging and progression assessment in KC by considering several biomechanical parameters as an addition to the previously purely tomographic or even topographic analysis. [ABSTRACT FROM AUTHOR]