Higher order aberrations in keratoconus .

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

A comparison of Scansys and Sirius tomography in healthy eyes.

PURPOSE: To assess the level of agreement and evaluate the reliability of measurements between two Scheimpflug imaging modalities, Scansys (MediWorks, China) and Sirius (CSO, Italy), in quantifying the anterior segment parameters in healthy eyes. METHODS: In a cross-sectional study, the right eyes of 38 healthy participants without any ocular or systemic diseases were examined. A range of anterior segment parameters including anterior and posterior flat and steep keratometry, central corneal thickness (CCT), thinnest corneal thickness (TCT), anterior chamber depth (ACD), anterior chamber angle (ACA), corneal volume, anterior chamber volume, and horizontal white to white diameter, derived from the sagittal curvature maps were measured. To evaluate the reliability of the measurements, intraclass correlation coefficient (ICC) and correlation coefficient were measured. Additionally, Bland-Altman plots were employed to examine the agreement in mean (bias line) and 95% limits of agreement between the two devices. RESULTS: The mean age was 31.5 ± 6.9 (range: 19-47) years. The ICC indicated that the majority of anterior segment parameters had an excellent or good level of reliability, surpassing the threshold of 0.9. Nevertheless, CCT and ACA exhibited a moderate level of reliability, with ICC values of 0.794 and 0.728, respectively. The correlation analysis showed a strong correlation for all the variables tested. The Bland-Altman plots revealed that the bias line was near zero and the 95% limits of agreement were narrow for most variables, except for the anterior flat and steep keratometry, which were found to range from - 0.57 to 0.84 D and - 0.68 to 0.87 D, respectively. CONCLUSION: Scansys and Sirius devices can be effectively used interchangeably for the evaluation of most anterior segment parameters; however, for anterior corneal curvatures, CCT and ACA, their alternative use is not recommended.

Interchangeability in Automated Corneal Diameter Measurements Across Different Biometric Devices: A Systematic Review of Agreement Studies.

PURPOSE: To provide an up-to-date review of the agreement in automated white-to-white (WTW) measurement between the latest topographic and biometric devices. METHODS: In this systematic review, PubMed, Web of Science, and Scopus databases were searched for articles published between 2017 and 2023, focusing on WTW agreement studies on adult, virgin eyes, with or without cataract and no other ocular comorbidities. Studies evaluating WTW measurements performed with autokeratometers, manual calipers, or manual image analysis were excluded. When available, the following metrics for the agreement of WTW measurements between pairs of devices were included: mean difference ± standard deviation, 95% limits of agreement (LoA), LoA width, 95% confidence interval (95 CI%), and intraclass correlation coefficient (ICC). RESULTS: Forty-one studies, covering comparisons for 19 devices, were included. Altogether, 81 paired comparisons were performed for 4,595 eyes of 4,002 individuals. The mean difference in WTW measurements between devices ranged from 0.01 mm up to 0.96 mm, with varying CI. The 95% LoA width ranged from 0.31 to 2.45 mm (median: 0.65 mm). The majority of pairwise comparisons reported LoA wider than 0.5 mm, a clinically significant value for phakic intraocular lens sizing. CONCLUSIONS: Nearly all analyzed studies demonstrated the lack of interchangeability of the WTW parameter. The corneal diameter, assessed by means of grayscale en-face image analysis, tended to demonstrate the lowest agreement among devices compared to other measured biometric parameters. [J Refract Surg. 2024;40(3):e182-e194.].

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

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

Corneal pseudoectasia: a case series.

OBJECTIVE: To raise awareness of conditions that can tomographically mimic corneal ectasia and describe the actions required to avoid misdiagnosis. METHODS: We report a retrospective case series of seven patients presenting at two tertiary care centers in Israel with a presumed diagnosis of keratoconus or post-refractive ectasia. Upon further examination, the ectasia diagnosis was reconsidered and eventually ruled out. RESULTS: Included were ten eyes of seven patients. Cases included bilateral diffuse Salzmann's nodular degeneration, ophthalmoplegia with strabismus which precluded proper fixation during the acquisition of tomography images, two cases of incorrect Pentacam parameter settings, a patient with a history of hyperopic laser-assisted in situ keratomileusis (LASIK) treatment in one eye and myopic LASIK in the fellow eye, a case of old post-photorefractive keratectomy (PRK) stromal haze, and a patient with posterior polymorphous corneal dystrophy. CONCLUSIONS: Tomography patterns mimicking corneal ectasia can appear in patients without ectatic pathology. The comprehensive ophthalmologist should be aware of such cases as they may substantially alter the treatment course and prognosis of these patients.

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

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

Outcomes after corneal crosslinking treatment in paediatric patients with keratoconus.

PURPOSE: This study aims to determine the efficacy and safety of accelerated corneal crosslinking in children with keratoconus. METHODS: The study enrolled 64 patients aged 16 years or younger, each contributing one eye for a total of 64 eyes for analysis. Participants underwent an accelerated form of corneal cross-linking with 15 min of ultraviolet A irradiation at a rate of 7 mW/cm2, resulting in a cumulative energy dose of 5.4 J/cm2. The primary outcome measures were best corrected visual acuity (BCVA) and corneal tomography at 6 and 12 months post-intervention. Parameters assessed included BCVA, spherical and cylindrical refraction, keratometry (K1 and K2), maximum keratometry (Kmax) and thinnest corneal thickness (TCT). These metrics were documented preoperatively and then again at 6 and 12 months postoperatively. In addition, any ocular or systemic conditions related to keratoconus were recorded for each participant. RESULTS: The results showed an improvement in BCVA at 12 months after surgery. K1 showed a decrease at both post-operative follow-ups while K2 remained constant throughout the observation period. Kmax showed a notable decrease at the 12 month postoperative follow-up. Although the TCT showed an initial decrease, it reached a stable state after 12 months of crosslinking. Refractive values remained stable at all subsequent examinations. Notably, no complications such as corneal opacity, non-healing epithelial defects or corneal infections occurred during the follow-up period. The most common ocular comorbidity was allergic conjunctivitis (34.4%). CONCLUSION: The findings suggest that accelerated corneal crosslinking treatment is effective in slowing or halting the progression of keratoconus. Furthermore, there were no persistent overt complications observed at 12 months after the procedure.

Prevalence of Keratoconus Based on Scheimpflug Corneal Tomography Metrics in a Pediatric Population From a Chicago-Based School Age Vision Clinic.

PURPOSE: Determine the pediatric prevalence of keratoconus (KC) using Scheimpflug corneal tomography. METHODS: A prospective observational study was done on subjects aged 3 to 18 years at the Princeton Vision Clinic, Chicago, IL. Scheimpflug tomography (Pentacam HR, OCULUS Optikgerate GmbH) scans (Belin/Ambrósio Enhanced Ectasia BAD3) yielded BAD Final D (Final D) and Back Elevation at the Thinnest Point (BETP) measurements. Criteria differentiating non-KC from KC suspects & KC were, Non-KC -Final D <2.00 in both eyes; KC suspect -Final D ≥2.00 and <3.00 in combination with BETP ≥18 µm for myopia and ≥28 µm for hyperopia/mixed astigmatism in at least one eye; and KC -Final D of ≥3.00 with BETP ≥18 µm for myopia or ≥28 µm for hyperopia/mixed astigmatism in at least one eye. Two thousand two hundred and six subjects were recorded, removing duplicate and poor-quality scans leaving 2007 subjects. RESULTS: Of 2007 subjects, six were classified as KC -prevalence of 1:334, three subjects were KC suspects -prevalence of 1:669, and total prevalence of KC suspects and KC was 1:223. CONCLUSION: The prevalence of KC in children is higher than previously reported, emphasizing the importance of sensitive screening for KC at its earliest manifestation as standard in pediatric comprehensive eye examinations.

Corneal Tomography in a Commercially Available Optical Coherence Tomography Device and Comparison With a Rotating Scheimpflug Camera.

OBJECTIVE: To compare the outcomes of corneal tomography obtained with an anterior-to-posterior segment optical coherence tomography device (Revo, Optopol Technologies Sp. z o.o.) and a rotating Scheimpflug camera (Pentacam AXL, Oculus Optikgeräte, Wetzlar, Germany). METHODS: In healthy subjects, agreement in stereometric parameters commonly used in cataract and refractive surgery was assessed. Comparison between the devices was performed using correlation coefficients, the Bland-Altman method, and a paired t test. RESULTS: Results of right eyes of 78 patients (47 women) aged 25.24±5.56 years were analyzed. The flat and steep anterior keratometry values were significantly higher for Revo than Pentacam (43.65±1.58 D vs. 42.99±1.47 D; P = 0.000, and 44.53±1.57 D vs. 43.82±1.49 D; P =0.000, respectively) and showed excellent correlation ( r =0.978 and 0.974, respectively). The results for maximal keratometry manifested a higher difference (45.89±1.69 D vs. 44.27±1.51 D for Revo and Pentacam, P =0.000) but were also strongly correlated ( r =0.871). Revo showed significantly lower corneal thickness values than Pentacam, both for apex pachymetry (535.54±32.45 vs. 550.74±31.55 µm; P =0.000) and for thinnest pachymetry (522.58±32.16 vs. 547.25±31.95 µm; P =0.000). The correlation coefficients for anterior and posterior corneal elevation at the thinnest point showed weak positive correlation ( r =0.179 and 0.185), while the correlation for corneal asphericity was moderate ( r =0.317). CONCLUSIONS: There was a significant difference between keratometric values obtained with Revo and the Pentacam AXL, although the measurements showed excellent correlation. Similar results were found for corneal thickness measurements, but not for corneal surface elevation and corneal asphericity.

Corneal Biomechanical Properties to Predict Prognosis of Abnormal Tomographic Corneas: A Prospective Cohort Study.

PURPOSE: To analyze the corneal biomechanical properties in patients with abnormal corneal tomography (ACT) and predict their stability using the biomechanical stability index (BSI). DESIGN: Prospective cohort study. METHODS: Setting: Multicenter study. STUDY POPULATION: This study included 385 eyes of 278 patients with stable ACT (n = 70), subclinical keratoconus (SKC, n = 65), keratoconus (n = 65), normal controls (NL, n = 142). Forty-three eyes with first-visit ACT were included in a separate cohort (follow-up ACT group). OBSERVATION PROCEDURE: Tomographical and biomechanical parameters (Pentacam and Corvis ST) were recorded. MAIN OUTCOME MEASURES: Nonparametric tests were used for comparison. Logistic regression was employed to introduce BSI to separate stable ACT and SKC accurately. An independent dataset of 43 first-visit ACT eyes was followed up for 1 year to validate BSI's accuracy and positive and negative predictive values (PPV, NPV). RESULTS: The tomographical and biomechanical parameters in patients with Stable ACT remained stable over the follow-up period (12.73 ± 2.57 months, P > .05). Stable ACT had 12/14 biomechanical parameters different (P < .05) from SKC but not different from NL (P > .05). With a cut-off value of 0.585, BSI demonstrated the strongest ability to distinguish between stable ACT and SKC (area under the receiver operating characteristic curve = 0.991), with 93.85% sensitivity and 97.14% specificity. During the 1-year follow-up of 43 eyes (follow-up ACT group), 30 remained stable. The accuracy, PPV, and NPV of the BSI were 95.35%, 100%, and 93.75%, respectively. CONCLUSIONS: Biomechanical properties of patients with stable abnormal tomography corneas were stronger than SKC and close to normal corneas, which may explain the reason for tomographic stability. The BSI may be useful for predicting disease progression in patients with ACT and the possible management of corneal cross-linking at the first visit.

Tomographic Predictors of Ectasia Development After Keratorefractive Surgery.

PURPOSE: The aim of this study was to identify the risk factors for postkeratorefractive surgery ectasia in unsuspicious tomographies and to report a new index coined diameter of peak locations (DPLs). METHODS: All patients who underwent keratorefractive surgery between 2011 and 2018 at Care-Vision Laser Centers, Israel, and later developed ectasia were included. For each ectasia case, 3 matched controls were selected. Demographic and preoperative, intraoperative, and postoperative data were collected. Multivariate analysis was performed to evaluate the interdependence of the variables. RESULTS: The retrospective study included 19 ectasia and 58 control eyes. There were no significant differences between the groups in ablation depth ( P = 0.73), preoperative spherical equivalent ( P = 0.12), percent tissue altered ( P = 0.71), residual stromal bed ( P = 0.73), and Ectasia Risk Score System ( P = 0.60). The anterior and the posterior symmetry index were significantly higher ( P < 0.001), and DPL was significantly tighter in the ectasia group ( P = 0.01). Binary multiple logistic regression found the symmetry index of the posterior cornea and DPL to be better predictors than age, percent tissue altered, Ectasia Risk Score System, residual stromal bed, and ablation depth. CONCLUSIONS: A higher posterior symmetry index and a tighter DPL are predictors of ectasia in patients with otherwise normal tomographies. A tight DPL implies a weak area in the cornea, which is thin and slightly bulging, increasing the risk of this area becoming ectatic.

Comparison of two different 360-degree intrastromal corneal rings combined with simultaneous accelerated-corneal cross-linking.

PURPOSE: to compare five-year outcomes of two complete intracorneal implants (MyoRing versus annular-shaped intracorneal implant [AICI]) combined with accelerated corneal cross-linking (A-CXL) in progressive KCN. METHODS: In this historical cohort study, preoperative and postoperative visual, refractive, tomographic, biomechanical, and aberrometric parameters of 27 eyes of 27 patients who underwent implantation of two complete rings (13 AICI and 14 MyoRing) combined with A-CXL were recorded. RESULTS: The mean age of patients in "AICI plus A-CXL" and "MyoRing plus A-CXL" groups were 28.1 ± 4.6 and 26.3 ± 3.8 years, respectively. All pre- and postoperative visual and refractive parameters between the two groups were not significantly different (p > 0.05). Comparing pre- and postoperative tomographic measurements showed that anterior corneal surface (ACS) flat-K and corneal thickness at pachymetric apex significantly improved for MyoRing plus A-CXL group after five years (p < 0.05). On the other hand, ACS K-max and mean-K values were significantly improved for AICI plus A-CXL group after five years (p < 0.05). Both groups revealed significant improvements in ACS steep-K and corneal astigmatism (p < 0.05). Five years after surgery, the high order aberration in the AICI group (2.60 ± 0.83) was significantly better than the MyoRing group (1.70 ± 0.43) (p = 0.007). CONCLUSIONS: Both complete intrastromal rings (MyoRing or AICI) combined with A-CXL significantly Improved visual, refractive, and corneal aberrometric, biomechanical, and tomographic parameters and halt the progression of KCN with comparable long-term outcomes.

Clinical Results of Accelerated Iontophoresis-Assisted Epithelium-on Corneal Cross-linking for Progressive Keratoconus in Children.

PURPOSE: To evaluate the clinical characteristics of pediatric patients with progression of keratoconus after accelerated iontophoresis-assisted epithelium-on corneal cross-linking (I-ON CXL) and to assess the efficacy and safety of re-treatment using accelerated epithelium-off CXL (epi-OFF CXL). METHODS: Sixteen eyes of 16 patients (mean age: 14.6 ± 2.5 years) with keratoconus underwent I-ON CXL. The main outcome measures were uncorrected distance visual acuity, corrected distance visual acuity, maximum keratometry index (Kmax), minimum corneal thickness, elevation front and elevation back measured at the thinnest point, total higher order aberrations root main square (HOA RMS), coma RMS, and spherical aberration. An increment of Kmax greater than 1.00 diopter (D) and a decrease of greater than 20 µm in pachymetry were considered to determine the progression of keratoconus. Patients with progression of keratoconus after I-ON CXL were re-treated using an epi-OFF CXL protocol. RESULTS: Two years after I-ON CXL, 12 patients showed progression of keratoconus, whereas 4 patients were stable. There was significant worsening of Kmax (P = .04) and steepest keratometric reading (P = .01). Furthermore, a significant correlation was documented between progression of keratoconus and age (P = .02). These patients were re-treated using an epi-OFF protocol and after 2 years all patients were stable, and a statistically significant reduction of the mean Kmax (P = .007), HOA RMS (P = .05), and coma RMS (P = 05) was observed. CONCLUSIONS: I-ON CXL was ineffective in the treatment of pediatric keratoconus in younger children, whereas it had an efficacy of 2 years in older children. Re-treatment using epi-OFF CXL proved effective to halt progression of keratoconus after I-ON CXL failure. [J Pediatr Ophthalmol Strabismus. 2024;61(1):44-50.].

Corneal topometric indices and proclivity toward corneal ectasia in vernal keratoconjunctivitis.

PURPOSE: To investigate changes in topometric corneal indices and proclivity toward corneal ectasia, as well as keratometric indices and anterior chamber dimensions in palpebral vernal keratoconjunctivitis (VKC). METHODS: This study included 80 patients with clinically established symptoms of grade 0 or grade 1 palpebral VKC (group 1) and 66 healthy participants (group 2). After a comprehensive ophthalmic examination including best-corrected visual acuity, intraocular pressure measurements and slit-lamp biomicroscopy, pachymetric indices and anterior chamber dimensions were measured using the Pentacam HR rotating Scheimpflug device. Topometric indices, which are particularly useful for determining proclivity toward corneal ectasia, were extracted from a topometric map. RESULTS: In groups 1 and 2, the mean ages were 13.11±5.22 and 16.45±5.09 years, respectively. The mean age at disease onset in group 1 was 10.09±5.03 years, and the mean disease duration was 36.23±8.43 months. Group 1 had significantly higher mean topometric indices than group 2, particularly the index of surface variance (P=0.001), index of vertical asymmetry (P=0.007), center keratoconus index (P=0.050), and Belin/Ambrosio enhanced ectasia total deviation value (P=0.032). Mean posterior corneal astigmatism differed significantly between groups 1 and 2 (P=0.003). CONCLUSIONS: Significantly higher mean topometric indices in VKC indicate a proclivity for corneal ectasia, which could be attributed to general changes in the corneal ultrastructure caused by persistent itching-induced eye rubbing.

Deep neural network with self-attention based automated determination system for treatment zone and peripheral steepened zone in Orthokeratology for adolescent myopia.

PURPOSE: The aim of this study is to develop an automatic model based on deep learning techniques for determining the Treatment Zone (TZ) and Peripheral Steepened Zone (PSZ) following Orthokeratology (OK) treatment. METHODS: A total of 1346 corneal topography maps were included in the study. A deep neural network based on the Segformer architecture was constructed to automatically detect TZ and PSZ. The model was optimized and trained multiple times, and the areas of TZ, PSZ, and TZ decentration were calculated based on the segmentation results. RESULTS: The mean Intersection over Union (mIoU) of the overall segmentation results of the model reached over 97% after multiple training with different optimization methods, and the IoU for the TZ and PSZ segmentation tasks were 98.08% and 94.54% in test set, respectively. Moreover, the model demonstrated high consistency with the expert annotation for the TZ segmentation, while a significant difference was found in the PSZ segmentation and expert annotation due to several interference factors. CONCLUSION: This study presents an efficient and repeatable system for clinical research, based on a deep neural network that accurately determines TZ and PSZ after OK treatment using the Segformer architecture. However, further deployment validation may be necessary.

Keratoconus in Down syndrome: Prevalence, risk factors, severity and corneal tomographic characteristics.

BACKGROUND: This study investigated the prevalence, risk factors and severity of corneal tomographic features of keratoconus in Down syndrome (DS). Additionally, previous studies indicate anomalous corneal features in DS, without keratoconus, this study characterised corneal features in DS without keratoconus. METHODS: This prospective observational study included participants with DS ≥10 years old. Keratoconus diagnosis, risk factors and corneal tomographic characteristics were recorded. Participants underwent slit-lamp biomicroscopy, Scheimpflug corneal tomography, corneal topography and autorefraction. A diagnosis of keratoconus (DS-KC), suspect keratoconus (DS-SK) and non-keratoconus (DS-NK) was made based on expert review of scans by three fellowship trained anterior segment ophthalmologists. Corneal tomography parameters from one eye of each participant were analysed. RESULTS: Keratoconus affected 50 (26.3%) of 190 participants, diagnosed by corneal tomography, topography or slit-lamp signs. Corneal hydrops affected 14.0% of DS-KC participants. Eye rubbing was a significant risk factor for keratoconus (p = 0.036). 175 (92%) participants could undertake corneal tomography of which tomography assessment alone identified 47 (26.9%) DS-KC participants, 64 (36.6%) DS-SK participants and 64 (36.6%) DS-NK participants. Significant differences (p < 0.001) were identified when the DS-KC, DS-SK and DS-NK groups were compared in maximum keratometry and posterior elevation at the thinnest point respectively: median (interquartile range) 50.20 (10.30D), 47.60 (1.95D), 46.50 (2.40D); 24.0 (38.00 µm), 10.00 (13.75 µm), 8.00 (6.00 µm). The DS-SK and DS-NK cohorts had similar minimum pachymetry, however, had several significantly different parameters among which included greater maximum keratometry, posterior elevation at the thinnest point in the DS-SK group. CONCLUSIONS: Keratoconus is common in DS. Keratoconus screening with corneal tomography is recommended for early detection.

Advanced Corneal Imaging in Keratoconus: A Report by the American Academy of Ophthalmology.

PURPOSE: To review the published literature on the diagnostic capabilities of the newest generation of corneal imaging devices for the identification of keratoconus. METHODS: Corneal imaging devices studied included tomographic platforms (Scheimpflug photography, OCT) and functional biomechanical devices (imaging an air impulse on the cornea). A literature search in the PubMed database for English language studies was last conducted in February 2023. The search yielded 469 citations, which were reviewed in abstract form. Of these, 147 were relevant to the assessment objectives and underwent full-text review. Forty-five articles met the criteria for inclusion and were assigned a level of evidence rating by the panel methodologist. Twenty-six articles were rated level II, and 19 articles were rated level III. There were no level I evidence studies of corneal imaging for the diagnosis of keratoconus found in the literature. To provide a common cross-study outcome measure, diagnostic sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) were extracted. (A perfect diagnostic test that identifies all cases properly has an AUC of 1.0.) RESULTS: For the detection of keratoconus, sensitivities for all devices and parameters (e.g., anterior or posterior corneal curvature, corneal thickness) ranged from 65% to 100%. The majority of studies and parameters had sensitivities greater than 90%. The AUCs ranged from 0.82 to 1.00, with the majority greater than 0.90. Combined indices that integrated multiple parameters had an AUC in the mid-0.90 range. Keratoconus suspect detection performance was lower with AUCs ranging from 0.66 to 0.99, but most devices and parameters had sensitivities less than 90%. CONCLUSIONS: Modern corneal imaging devices provide improved characterization of the cornea and are accurate in detecting keratoconus with high AUCs ranging from 0.82 to 1.00. The detection of keratoconus suspects is less accurate with AUCs ranging from 0.66 to 0.99. Parameters based on single anatomic locations had a wide range of AUCs. Studies with combined indices using more data and parameters consistently reported high AUCs. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Comparison of standard versus accelerated corneal collagen cross-linking for keratoconus: 5-year outcomes from the Save Sight Keratoconus Registry.

OBJECTIVE: To compare long-term effectiveness of Standard (UV intensity: 3 mW/cm2, duration: 30 min) vs Accelerated (UV intensity: 9 mW/cm2, duration: 10 min) corneal cross-linking (CXL) for stabilising keratoconus. METHODS: Data for this observational study were captured through a web-based registry system from the routine clinical practice (15 sites across Australia, New Zealand and Italy). The outcomes were compared using mixed-effects regression models. A total of 100 eyes (75 patients) who had standard CXL and 76 eyes (66 patients) who had accelerated CXL, with a follow-up visit at five-year post-CXL were included. RESULTS: Both CXL protocols were effective and safe in stabilising keratoconus and improving outcomes. The adjusted mean changes (95% CI) in outcomes were better in standard CXL than in accelerated CXL [visual acuity gain, 10.2 (7.9-12.5) vs 4.9 (1.6-8.2) logMAR letters; pinhole visual acuity 5.7 (3.5-7.8) vs 0.2 (-2.2 to 2.5) logMAR letters; Kmax -1.8 (-4.3 to 0.6) vs 1.2 (-1.5 to 3.9)D; K2 -0.9 (-2.2 to 0.3) vs 0.1 (-1.3 to 1.6)D; MCT -3.0 (-13.7 to 7.7) vs -11.8 (-23.9 to 0.4) µm (p values for visual acuity, pinhole visual acuity, Kmax: <0.05; for K2 and MCT: >0.05)]. The frequency of adverse events at the 5-year follow-up visit was low in both groups [standard, 5 (5%; haze 3; scarring 1, epithelial defect 1) and accelerated 3 (3.9%; haze 2, scarring 1)]. CONCLUSIONS: Both standard and accelerated CXL were safe and effective procedures for stabilising keratoconus in the long term. The standard CXL resulted in greater improvements in visual acuity and keratometry.

Comparison of corneal tomographic parameters between Hispanic and non-Hispanic patients.

PURPOSE: To compare corneal tomographic parameters between Hispanic White and non-Hispanic White patients using Pentacam data. METHODS: This retrospective study evaluated preoperative Pentacam data from 641 patients 50 years or older who underwent surgery for senile cataract and self-identified as Hispanic or non-Hispanic White. Patients of non-White race or multiethnic groups, or a history of surgery, trauma, or any abnormality of the cornea or anterior segment were excluded. Cornea and anterior segment parameters, as measured with Pentacam, were then compared between Hispanics and non-Hispanics. RESULTS: There were 352 Hispanic White and 289 non-Hispanic White patients. These included 231 men and 410 women, with a mean age of 69.5 ± 8.2 years. There were no significant differences between Hispanics and non-Hispanics in front or back keratometry or amount of front astigmatism. However, Hispanics had a greater amount of back astigmatism (0.36 ± 0.19 vs 0.32 ± 0.17 diopter, P = 0.04). Moreover, there was a statistically significant difference in front steep axis of the left eyes between Hispanics and non-Hispanics (97.8 ± 47.9 vs 108.2 ± 48.9 deg, P = 0.01), and a marginally significant difference in front steep axis of the right eyes (81.0 ± 48.2 vs 73.5 ± 49.9 deg, P = 0.06). Hispanics also had a lower vertex pachymetry (548.1 ± 34.5 vs 553.4 ± 37.4 µm, P = 0.04) and a smaller anterior chamber volume (134.7 ± 39.0 vs 146.1 ± 39.9 mm3, P < 0.001). CONCLUSIONS: There are some differences in cornea and anterior segment parameters between Hispanics and non-Hispanics 50 years or older who underwent surgery for senile cataract. However, such differences may not be clinically significant.

Accuracy comparison of tomography devices for ray tracing-based intraocular lens calculation.

PURPOSE: To evaluate the interchangeability of different tomography devices used for ray tracing-based intraocular lens (IOL) calculation. SETTING: Eye clinic, Castrop-Rauxel, Germany. DESIGN: Retrospective analysis. METHOD: Measurements from 3 Placido-Scheimpflug devices and 3 optical coherence tomography (OCT) devices were compared in 83 and 161 other eyes after cataract surgery, respectively. 2-dimensional matrices of anterior local corneal curvature and local corneal thickness are transferred to the ray-tracing software OKULIX. Calculations are performed with the same IOL in the same position of an eye with the same axial length. Differences in spherical equivalent (SE), astigmatism, and spherical aberration are evaluated. Furthermore, the influence of the size of the matrices (optical zone) on the accuracy is quantified. RESULTS: For the Placido-Scheimpflug devices, the deviations from the average of three measurements taken for each eye in SE (mean ± SD) were 0.17 ± 0.24 diopters (D), -0.26 ± 0.29 D, and 0.08 ± 0.39 D ( P < .001, analysis of variance [ANOVA]), for the centroids of the astigmatic differences 0.04 D/173 degrees, 0.14 D/93 degrees, and 0.10 D/7 degrees, and for the median of the absolute values of the vector differences 0.31 D, 0.33 D, and 0.29 D. For OCT devices, the corresponding results were 0.01 ± 0.21 D, -0.03 ± 0.21 D, and 0.02 ± 0.20 D ( P = .005, ANOVA); 0.18 D/120 degrees, 0.07 D/70 degrees, and 0.22 D/4 degrees; and 0.26 D, 0.30 D, and 0.33 D. The accuracy of the calculated spherical aberrations allows for an individual selection of the best fitting IOL model in most cases. CONCLUSIONS: The differences are small enough to make the devices interchangeable regarding astigmatism and spherical aberration. Although there are significant differences in SE between Scheimpflug and OCT devices, the differences between OCT devices are also small enough to make them interchangeable, but the differences between Placido-Scheimpflug devices are too large to make these devices interchangeable.