Thinnest Corneal Thickness Research Articles

Assessment of Keratoconus Risk in Very Asymmetric Ectasia Using Corneal Tomographic and Biomechanical Parameters.

To investigate the relationship between corneal tomographic or biomechanical parameters and risk of keratoconus in very asymmetric ectasia (VAE). This retrospective case-control single-centre study included patients with VAE and normal controls. The VAE group had clinical ectasia in one eye and normal topography (VAE-NT) in the fellow eye; VAE-NT eyes were selected for analysis. The control group was selected from corneal refractive surgery candidates; the right eye was enrolled. Scheimpflug-based corneal tomography (Pentacam) and corneal biomechanical assessment (Corvis ST) were performed. Univariate and multivariable logistic regression were performed using Cox proportional hazards models to evaluate keratoconus-associated risk factors. A two-piecewise linear regression model was applied to examine the threshold effect of selected vital paragmeters on the risk of keratoconus according to a smoothing plot. Threshold effect between tomographic integration and risk of keratoconus was observed. Discrepancy between the central corneal thickness and thinnest corneal thickness (discrepancy CCT vs TCT) greater than 5 μm, discrepancy between the apex corneal thickness and thinnest corneal thickness (discrepancy ACT vs TCT) greater than 3 μm, vector distance between CCT and TCT (distance CCT vs TCT) greater than 0.65 mm indicated a significant increased risk of keratoconus. Risk of keratoconus decreased when distance CCT vs TCT was less than 0.65 mm. Discrepancy CCT vs TCT, discrepancy ACT vs TCT, and distance CCT vs TCT can be used as indicators for risk assessment of early keratoconus.

Comparing Repeatability and Agreement between Commonly Used Corneal Imaging Devices in Keratoconus.

Keratometry and pachymetry are important for diagnosis and monitoring of keratoconus. Many corneal imaging units exist but comparison to determine repeatability and agreement are paramount for adequate keratoconus management in primary and secondary care. To evaluate the repeatability and agreement of a Placido disc-based videokeratoscope (Medmont-E300 topographer) used in primary care with spectral-domain optical coherence tomography (Revo-NX) and Scheimpflug corneal tomography (Pentacam-AXL) in secondary-care. This was a prospective, single-center study where one eye was randomized to have central and thinnest corneal thickness (CCT, TCT) and maximum, mean, steep and flat keratometry (Kmax, Kmean, Ksteep and Kflat), measured with all three devices. Three measurements were completed per device to assess intra-observer repeatability. 110 eyes from 110 patients with keratoconus were analyzed. Repeatability was best with the Pentacam for CCT, Kmax, Kmean, Ksteep and Kflat parameters (precision = 9.21,0.8,0.38,0.52,0.58). The Medmont had better repeatability than the Revo with Kmax, Kmean, Ksteep and Kflat (precision = 1.41,1.35,1.43,1.59). Revo had the best repeatability with TCT (precision = 3.81). The intraclass correlation coefficient was ˃0.94 for all parameters in all devices. Agreement was generally poor between devices. However, there was good agreement between Pentacam and Medmont Kflat measurements (P˃.05). Repeatability of keratometry parameters with the Pentacam and Medmont were greater than the Revo, suggesting a lower threshold for change for anterior corneal changes. The Revo had the greatest repeatability for TCT, suggesting a lower threshold for assessing thinning in disease progression and corneal-crosslinking safety. There was poor agreement between devices so devices cannot be used interchangeably.

Comparison of corneal measurements using two different Scheimpflug analyzers in Sirius and Pentacam devices

The aim was to compare measurements of anterior segment biometry parameters using two Scheimpflug tomographies, Pentacam and Sirius to assess the agreement. Prospective cross-sectional observational study. A total of 60 eyes of 30 healthy subjects were included and evaluated with Pentacam followed by Sirius imaging. Corneal indices were performed with two modalities in both eyes including; apical corneal thickness (ACT), corneal thickness at pupil site(PCT), thinnest corneal thickness (TCT), anterior chamber depth (ACD), chamber angle, chamber volume, cornea volume, mean front keratometry (FKm), the radius of corneal curvature at the anterior and posterior surface in steep and flat meridian, anterior astigmatism values, pupil diameter, and horizontal corneal diameter. The Bland–Altman graph and ICC (intra-class correlation were used to establish an agreement and present the similarity of the findings. Most parameters showed perfect agreement. In both devices, the ICC was more than 0.91 in all measurements except for ACD (ICC = 0.820), cylinder axis (ICC = 0.520), TCT(ICC = 0.881), ACT(ICC = 0.672), PCT (ICC = 0.882), chamber angle (ICC = 0.362), pupil diameter(ICC = 0.137). Pentacam yielded higher values that were significant in five parameters including 3.47 μm for TCT, 4.29 µm for PCT, 10.03 mm3 for chamber volume,2.67 mm3 for cornea volume, and 1.49 mm for pupil diameter but there was only a statistically significant difference in cornea volume and pupil diameter (p-value < 0.001). However, in Pentacam only the chamber angle value was 6.44 mm3 lower than Sirius, with a statistically significant difference (p-value < 0.001). Although these two devices had some statistically different results, it seems that they have a good agreement and correlation in most parameters.

Comparison of a New Scheimpflug Camera and Swept-Source Optical Coherence Tomographer for Measurements of Anterior Segment Parameters.

This study evaluated the differences and agreement between a new Scheimpflug camera (Scansys) and a swept-source anterior segment optical coherence tomographer (CASIA2) for measurements of the anterior segment of the eye in normal subjects. This prospective study included 84 eyes from 84 normal adult subjects who underwent three consecutive measurements with the Scansys and the CASIA2 in random order. The mean keratometry (Km), astigmatism magnitude (AST), J0, and J45 vectors for both anterior and posterior corneal surfaces, central corneal thickness (CCT), thinnest corneal thickness (TCT), and anterior chamber depth (ACD)were obtained by both devices. The difference between these two devices was assessed using paired ttest and violin plots. Bland-Altman plots and 95% limits of agreement (LoAs) were used to evaluate agreement. No statistically significant differences between the two devices were found for the anterior AST, anterior J45, and posterior J45 (P > 0.05). The remaining parameters were statistically significant (P ≤ 0.05), but the differences not clinically significant. The violin plots showed that the distribution and probability density of the measured parameters were similar for both devices. Bland-Altman plots revealed high agreement for the measured parameters between the Scansys and CASIA2, with narrow 95%LoAs. In terms of assessing parameters for the anterior segment, our study indicated that Scansys and CASIA2 generally showed significant agreement. The two devices used in this study's assessment of all the parameters can be used interchangeably in refractive analysis.

Mitochondrial DNA heteroplasmy analysis in keratoconus patients from China.

Background: Mitochondrial DNA (mtDNA) variants have been implicated in keratoconus (KC). The present study aimed to characterize the mtDNA heteroplasmy profile in KC and explore the association of mitochondrial heteroplasmic levels with KC. Methods: Mitochondrial sequencing of peripheral blood samples and corneal tomography were conducted in 300 KC cases and 300 matched controls. The number of heteroplasmic and homoplasmic variants was calculated across the mitochondrial genome. Spearman's correlation was used to analyze the correlation between the number of heteroplasmic variants and age. The association of mtDNA heteroplasmic level with KC was analyzed by logistic regression analysis. Moreover, the relationship between mitochondrial heteroplasmic levels and clinical parameters was determined by linear regression analysis. Results: The distribution of mtDNA heteroplasmic variants showed the highest number of heteroplasmic variants in the non-coding region, while the COX3 gene exhibited the highest number in protein-coding genes. Comparisons of the number of heteroplasmic and homoplasmic non-synonymous variants in protein-coding genes revealed no significant differences between KC cases and controls (all p > 0.05). In addition, the number of heteroplasmic variants was positively associated with age in all subjects (r = 0.085, p = 0.037). The logistic regression analyses indicated that the heteroplasmic levels of m.16180_16181delAA was associated with KC (p < 0.005). Linear regression analyses demonstrated that the heteroplasmic levels of m.16180_16181delAA and m.302A>C were not correlated with thinnest corneal thickness (TCT), steep keratometry (Ks), and flat keratometry (Kf) (all p > 0.05) in KC cases and controls separately. Conclusion: The current study characterized the mtDNA heteroplasmy profile in KC, and revealed that the heteroplasmic levels of m.16180_16181delAA were associated with KC.

Advanced Anterior Eye Segment Imaging for Ichthyosis.

This was a single-center prospective observational study. The study group consisted of five patients (P1-P5) aged 13-66 years. Multimodal imaging was performed, including slit-lamp examinations, swept-source optical coherence tomography (SS-OCT), and in vivo confocal microscopy (IVCM). All patients were diagnosed with moderate-to-severe dry eye disease (DED). The corneas showed a significant pattern of irregularity, with a significant difference between the corneal thickness at the apex (CAT) and the corneal thinnest thickness (CTT), exceeding 375 µm. Three patients were diagnosed with ectasia patterns based on SS-OCT. All patients showed abnormalities in at least one Fourier index parameter for at least one eye at 3 or 6 mm in the keratometric, anterior, or posterior analyses. IVCM examinations revealed changes in all corneal layers. By combining the results of multimodal imaging, we were able to detect preclinical abnormalities, distinguish characteristic changes common to ichthyosis, and reveal the depth and characteristics of corneal abnormalities. Therefore, patients with ichthyosis should be examined for DED and ectatic disorders early in clinical practice.

Biomechanical Analysis of Tomographically Regular Keratoconus Fellow Eyes Using Corvis ST.

Keratoconus is a bilateral, yet asymmetric disease. In rare cases, the second eye may show no signs of tomographic changes. The purpose of this study was to analyze the biomechanical characteristics in tomographically regular keratoconus fellow eyes. This retrospective, consecutive case series analyzed 916 eyes of 458 patients who presented to our keratoconus clinic between November 2020 and October 2022. Primary outcome measures included best-corrected visual acuity (BCVA), tomographic Scheimpflug analysis using Pentacam AXL (Oculus, Wetzlar, Germany), and biomechanical assessment using Corvis ST (Oculus, Wetzlar, Germany). Tomographic changes were assessed via analysis of the anterior and posterior curvature, K-max, thinnest corneal thickness (TCT), the Belin/Ambrosio Deviation Display (BAD-D), and the ABCD-Grading. Biomechanical changes were analyzed using Corvis Biomechanical Index (CBI) and Tomographic Biomechanical Index (TBI). Of 916 eyes, 34 tomographically regular fellow eyes (7.4%) were identified and included in the analysis. Overall, the mean BCVA was - 0.02 ± 0.13 logMAR. Tomographic analysis showed mean K-max of 43.87 ± 1.21 D, mean TCT of 532 ± 23 µm, and mean BAD-D of 1.02 ± 0.43. Biomechanical analysis demonstrated mean CBI of 0.28 ± 0.26 and mean TBI of 0.34 ± 0.30. While normal CBI-values were observed in 16(47%) of 34 eyes, only 13 eyes (38%) showed a regular TBI and only 7 eyes (21%) showed regular TBI and CBI. The sensitivity of CBI and TBI to detect a tomographically normal keratoconus fellow eye was 53% and 62%, respectively. A highly asymmetric corneal ectasia with regular tomographic finding in a fellow eye is rare among keratoconus patients. In such cases, a biomechanical analysis may be useful in detecting early signs of corneal ectasia. In our analysis, the TBI showed high sensitivity for detecting a biomechanical abnormality in tomographically regular fellow eyes.

Hypocalcemic cataract secondary to idiopathic hypoparathyroidism in an adolescent.

Idiopathic hypoparathyroidism is a rare endocrine disorder characterized by hypocalcemia secondary to inadequate parathyroid hormone secretion. Hypocalcemia-related cataract is most often observed in patients with postoperative hypoparathyroidism, whereas primary hypoparathyroidism-related cataract is rare and displays slow progression. Cataract usually occurs in people aged 18 to 50 years. Here, we describe a 17-year-old boy with bilateral cataract and a history of hypocalcemic tetany who was diagnosed with idiopathic hypoparathyroidism. Phacoemulsification with implantation of a monofocal aspherical intraocular lens was performed in the right eye; 6 months later, it was performed in the left eye. Elevated phosphorus and diminished calcium were observed in blood and aqueous humor. A deep anterior chamber, relatively thin central corneal thickness, large white-to-white distance, and thin lens were also observed. During follow-up, neither eye displayed intraocular lens decentration; best-corrected visual acuity was 20/20 in both eyes. These findings suggest that ophthalmologists should be vigilant when hypocalcemic tetany and cataract are present, especially in adolescents and young adults.

Corneal cross-linking for treatment of keratoconus relapse in post-keratoplasty eyes.

Keratoconus relapse after penetrating keratoplasty is a rare condition that may result in severe visual deterioration and corneal graft thinning. Therefore, treatment to stabilize the cornea should be considered. The purpose of this study was to evaluate the safety and efficacy of Corneal Cross-Linking (CXL) in eyes with relapse of keratoconus after penetrating keratoplasty for keratoconus. A retrospective review of eyes that developed keratoconus relapse following a penetrating keratoplasty and treated with CXL. The main outcome measures were change in maximal keratometry (Kmax), best-corrected distance visual acuity (BCVA), thinnest corneal thickness (TCT) and central corneal thickness (CCT), and complications. We identified 10 consecutive eyes of 9 patients. Preoperative median BCVA before the CXL and 1year after the CXL procedure remained stable (p = 0.68). The median (IQR) of Kmax improved from 63.2 (24.9) D before the CXL procedure to 62.2 (27.1) D at 1year postoperatively (P = 0.028). Median TCT and CCT also remained with no significant change 1year after CXL. No complications were noted following the procedure. CXL in eyes with keratoconus relapse after keratoplasty is a safe and effective procedure enabling not only visual stabilization but also might bring keratometry improvement. Routine follow-up after keratoplasty should be performed for early detection of keratoconus relapse and CXL is timely advised when such a relapse is documented.

Repeatability and Agreement between Scansys and Pentacam in Ocular Biological Parameters.

To assess the repeatability and agreement between Scheimpflug-based corneal topography, Scansys and Pentacam, in measuring ocular parameters in myopic eyes. A Grade-A tertiary hospital in Beijing, China. Cross-sectional study. The following measurements were performed in 204 patients undergoing pre-operative examinations for refractive surgery from the corneal curvature, astigmatism, corneal thickness, corneal volume, corneal asphericity, anterior chamber depth and volume, and pupil diameters. Repeatability was determined using intraclass correlation coefficient (ICC) with 95% confidence interval (95% CI), Cronbach's Alpha, coefficient of variation (CV), within-subject standard deviation (Sw), test-retest repeatability (TRT), and one-way analysis of variance (one-way ANOVA). The inter-device agreement was determined using paired t-test and Bland-Altman plots. Scansys showed good repeatability in the anterior and posterior corneal flattest meridian (Kf), steepest meridian (Ks), and mean (Km), axis of anterior corneal Ks, anterior corneal astigmatism, pupil central corneal thickness, central corneal thickness, corneal apex thickness, thinnest corneal thickness, corneal volume, photopic pupil diameter, anterior chamber depth and volume. In the agreement study, Bland-Altman plots showed that 95% LoA of corneal curvature, pupil central corneal thickness, corneal apex thickness, thinnest corneal thickness, and corneal volume generated by Scansys and Pentacam were narrow. There were no statistically significant differences in the anterior corneal Kf and Km. Scansys showed good repeatability in measuring corneal curvature of anterior and posterior surfaces, anterior corneal astigmatism, corneal thickness, corneal volume, photopic pupil diameter, anterior chamber volume and depth. Scansys and Pentacam can only be used interchangeably in measuring anterior corneal curvature.

The Biomechanical E-Staging: In Vivo Biomechanics in Keratoconus.

Belin's ABCD keratoconus classification system allows keratoconus staging based on the criteria of anterior (A) and posterior (B) corneal curvature, thinnest corneal thickness (C), and best spectacle-corrected visual acuity (D). These parameters also provide a progression assessment, but do not take corneal biomechanics into account. The analysis of corneal biomechanics by the Corvis ST (Oculus, Wetzlar, Germany) allows for separation of healthy and keratoconus corneas, based on the Corvis Biomechanical Index (CBI) and the Tomographic Biomechanical Index (TBI). As Corvis ST measurements are highly reliable and are independent of keratoconus severity, a biomechanical parameter was developed for keratoconus corneas based on the linear term of the CBI. This provides biomechanical keratoconus staging. The Corvis Biomechanical Factor (CBiF) is the basis for the introduction of the biomechanical E-staging, which augments the ABCD classification to the ABCDE classification, thus including the cornerstone of corneal biomechanics. This article highlights strengths and limitations of the ABCDE classification. "Unilateral keratoconus" supposedly turns out to be mostly a snapshot of a highly asymmetric keratectasia. Regular astigmatism is sometimes an important differential diagnosis to keratectasia and may be difficult to differentiate from it. Furthermore, the use of the biomechanical E-staging in daily practice for progression assessment of keratoconus and after its treatment by corneal cross-linking or implantation of intracorneal ring segments will be demonstrated and discussed.

Comparison of Hybrid Contact Lenses and Rigid Gas-Permeable Contact Lenses in Moderate and Advanced Keratoconus.

We aimed to compare the clinical results and topographic data of the new generation hybrid contact lens (HCL) and rigid gas-permeable contact lens (RGPCL) in patients with moderate and advanced keratoconus. In this prospective study, HCL users comprised group 1 and RGPCL users comprised group 2. Snellen uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), and lens-corrected visual acuity (LCVA); manifest spherical-cylindrical values; corneal topography measurements (flat keratometry [K1], vertical keratometry [K2], mean K, maximum K [Kmax], central corneal thickness [CCT], and thinnest corneal thickness [TCT]); and cone location were recorded. The study included 83 eyes of 51 patients in group 1 and 61 eyes of 40 patients in group 2. The groups were similar in age and gender (p>0.05). Mean LCVA (logMAR) was significantly lower than BCVA in both groups (p<0.001). The mean visual gain with contact lenses (Snellen chart) was 3.4±1.8 lines in group 1 and 4.0±2.1 lines in group 2. There was no significant difference between the two groups in BCVA, LCVA, or lines gained (p>0.05). There was also no significant difference between the two groups in terms of keratoconus stages, mean Kmax, CCT, TCT, or cone location (p>0.05), while mean UCVA (logMAR) and mean K were higher in group 2 (p<0.05). In both groups, the visual gain with lenses was higher in eyes with central cones, and there was significantly greater visual increase in group 2 (p=0.039). In moderate and advanced keratoconus, HCLs improved vision as much as RGPCLs and both lenses were more effective for central cones. Nevertheless, longer term of follow-up and larger numbers of patients are needed for long term follow-up results of HCL.

Analysis of corneal topographic and endothelial cell properties in newly diagnosed obstructive sleep apnea patients: A case-control study

PurposeTo investigate the topographic features and endothelial cell changes in the corneas of patients with newly diagnosed obstructive sleep apnea (OSA). BackgroundThis cross-sectional case-control study included 98 patients with OSA and 90 healthy controls. OSA was diagnosed on the basis of a polysomnographic sleep examination. Patients with OSA were grouped according to their apnea-hypopnea index (AHI) scores. Corneal topographic measurements were obtained using the Scheimpflug–Placido disk topographer, and keratometry values, anterior chamber parameters, thinnest corneal thickness, symmetry index (SI), keratoconus vertex (KV), and the Baiocchi-Calossi-Versaci index, including keratoconus (KC) screening indexes, were recorded. The corneal endothelium was visualizedby specular microscopy, and the endothelial cell density, coefficient of variability (CV), and percentage of hexagonal cells (HEX) were recorded. ResultsIn this study, 32 patients had mild, 34 patients had moderate, and 32 patients had severe OSA. The mean back KV (KVb) and back SI values were significantly higher in the OSA group than in the control group (P <0.001, P = 0.035, respectively). As body mass index (BMI) increased, KVb also increased significantly (r = 0.281; P = 0.009). The mean CV and HEX values differed significantly between the OSA and control groups (P = 0.012 and P = 0.002, respectively). In addition, a significant correlation was found between AHI and KVb and CV values (r = 0.315; P <0.001 and r = 0.231; P = 0.011, respectively). ConclusionsThis study revealed abnormal changes in the corneal endothelial morphology and topographic KC screening indexes in relation to OSA severity in patients and controls. Further research is required to determine the effect of BMI on corneal topographic findings in patients with OSA.

A strategy to treat coagulopathy in patients with massive hemorrhage

To investigate the topographic features and endothelial cell changes in the corneas of patients with newly diagnosed obstructive sleep apnea (OSA).This cross-sectional case-control study included 98 patients with OSA and 90 healthy controls. OSA was diagnosed on the basis of a polysomnographic sleep examination. Patients with OSA were grouped according to their apnea-hypopnea index (AHI) scores. Corneal topographic measurements were obtained using the Scheimpflug–Placido disk topographer, and keratometry values, anterior chamber parameters, thinnest corneal thickness, symmetry index (SI), keratoconus vertex (KV), and the Baiocchi-Calossi-Versaci index, including keratoconus (KC) screening indexes, were recorded. The corneal endothelium was visualizedby specular microscopy, and the endothelial cell density, coefficient of variability (CV), and percentage of hexagonal cells (HEX) were recorded.In this study, 32 patients had mild, 34 patients had moderate, and 32 patients had severe OSA. The mean back KV (KVb) and back SI values were significantly higher in the OSA group than in the control group (P <0.001, P = 0.035, respectively). As body mass index (BMI) increased, KVb also increased significantly (r = 0.281; P = 0.009). The mean CV and HEX values differed significantly between the OSA and control groups (P = 0.012 and P = 0.002, respectively). In addition, a significant correlation was found between AHI and KVb and CV values (r = 0.315; P <0.001 and r = 0.231; P = 0.011, respectively).This study revealed abnormal changes in the corneal endothelial morphology and topographic KC screening indexes in relation to OSA severity in patients and controls. Further research is required to determine the effect of BMI on corneal topographic findings in patients with OSA.

Comparison of corneal measurements in normal and keratoconus eyes using Anterior Segment Optical Coherence Tomography (AS-OCT) and Pentacam HR topographer

BackgroundKeratoconus (KC) is easily recognized by its unique topographic pattern, but it can be difficult to distinguish subclinical form of the disease from the normal cornea. Optovue anterior segment optical coherence tomography (AS-OCT) helps diagnose KC.Aim of the workTo assess and the level of agreement of Keratometry-readings (K), Central Corneal Thickness (CCT) and Thinnest Corneal Thickness (TCT) measurements obtained by Optovue AS-OCT and Wavelight Oculyzer Pentacam HR in two groups: KC eyes and normal eyes.Patients and methodsThis is a prospective clinical observational study. The study included 110 eyes divided into two groups. The study group included 62 eyes with topographic evidence of KC. The control group included 48 eyes of normal subjects with no topographic evidence of KC. All of the participants underwent full cycloplegic refraction, spectacle best-corrected distance visual acuity, comprehensive slit-lamp biomicroscopy and fundoscopy. All participants underwent corneal topography by Pentacam HR and AS-OCT.ResultsThere were highly significant differences between the studied groups as regarding BCVA, intraocular pressure and CCT measurements which were found to be lower among KC group compared to the control one. There were highly significant differences between the studied groups regarding TCT measurement detected by Pentacam HR and AS-OCT which was found to be lower among the keratoconus group compared to the control one (470.9, 455.7 versus 541.9 and 518.7 respectively).ConclusionBoth Scheimpflug-based imaging and AS-OCT provide comparable readings with a good agreement regarding corneal pachymetry in keratoconus group with accurate identification of KC eyes and healthy ones. However, there was a significant difference in K readings between both devices in Keratoconus and control group.

Assessment of Health Disparities and Barriers to Accessing Keratoconus and Crosslinking at a Tertiary Referral Center.

The aim of this study was to determine the barriers to accessing the crosslinking service in Auckland, New Zealand. This was a prospective 1-year study of patients at Auckland District Health Board. Studied parameters included age, sex, body mass index, ethnicity, New Zealand Deprivation (NZDep; an area-based measure of socioeconomic status, 1 = low deprivation-10 = high deprivation) score of residence, disease severity (maximum keratometry and thinnest corneal thickness), attendance, distance travelled, car ownership, employment status, and visual outcomes. Statistical analysis was performed using independent t tests, Pearson correlation, independent samples ANOVA, MANCOVA, and binomial logistic regression. Four hundred fifty-four patients with keratoconus were analyzed and had a mean age of 24.1 ± 0.8 years, mean body mass index of 33.0 ± 9.7 kg/m 2 , and 43% were female. Pacific Peoples consisted 40.2% of the population; Māori 27.2%; Europeans 21.2%; Asian 9.9%; and Middle Eastern, Latin American, and African (MELAA) 1.3%. The mean distance travelled was 12.5 ± 9.5 km, NZDep score was 6.8 ± 2.6, and attendance was 69.0 ± 42.5%. The lowest attendance was observed in Pacific Peoples (58.9%) and the highest was in Asians (90%) ( P = 0.019). The mean worst-eye visual acuity at attendance was 0.75 ± 0.47 logMAR (6/35). Unemployment was associated with worse best-eye visual acuity at FSA ( P = 0.01) and follow-up ( P < 0.05). Māori and Pacific Peoples had the highest NZDep ( P < 0.001), were younger at presentation ( P = 0.019), had higher disease severity ( P < 0.001), and worse visual acuity ( P < 0.001). Poor attendance was seen in this cohort. Pacific Peoples and Māori presented younger with worse disease severity and visual acuity but also had the highest nonattendance. These results suggest that deprivation, factors associated with ethnicity, and unemployment are potential barriers to attendance.

Repeatability of Scheimpflug based corneal tomography parameters in advanced keratoconus with thin corneas.

To determine the repeatability limits of corneal tomography parameters in patients with advanced and moderately thin keratoconic corneas to assist in planning thickness-based procedural interventions. Prospective, single-centre, repeatability study. Three tomography scans using the Pentacam AXL were obtained from patients with keratoconus with thinnest corneal thickness (TCT) ≦400 µm (sub-400 group) and compared to those with TCT = 450-500 µm (450-plus group). Eyes with previous crosslinking, intraocular surgery, or acute corneal hydrops were excluded. Eyes were age and gender-matched. The within-subject standard deviations for flat keratometry (K1), steep keratometry (K2), maximal keratometry (Kmax), astigmatism and TCT were used to calculate respective repeatability limits (r). Intra-class correlation coefficients (ICC) were also analysed. The sub-400 group comprised 114 eyes from 114 participants, and the 450-plus group comprised 114 eyes from 114 participants. In the sub-400 group, TCT was amongst the least repeatable parameters (33.92 µm; ICC 0.96), compared with the 450-plus group (14.32 µm; ICC 0.99, p < 0.01). In the sub-400 group, K1 and K2 of the anterior surface were the most repeatable parameters (r 3.79 and 3.22 respectively; ICC 0.97 and 0.98 respectively) compared with the 450-plus group (r 1.17 and 0.92 respectively; and ICC 0.98 and 0.99 respectively, p < 0.01). The repeatability of corneal tomography measurements is significantly reduced in sub-400 keratoconic corneas when compared to 450-plus corneas. Repeatability limits should be carefully considered when surgical interventions are planned for such patients.

Keratoconus tomographic indices in osteogenesis imperfecta

PurposeOsteogenesis imperfecta (OI) is a rare inherited disease affecting collagen-rich tissues. Ocular complications have been reported such as thin corneas, low ocular rigidity, keratoconus, among others. The purpose of this study is to characterize corneal tomographic features in OI patients compared to unaffected patients, with particular focus on commonly studied keratoconus indices.MethodsCross-sectional case–control study including 37 OI patients and 37 age-matched controls. Patients and controls underwent comprehensive ophthalmological examination including corneal Scheimpflug tomography with a Pentacam HR device (Oculus Optikgeräte GmbH, Wetzlar, Germany) to analyse and compare topometric, tomographic, pachymetric and Belin-Ambrósio Enhanced Ectasia Display III (BAD-D) data of both eyes of each patient.ResultsMost OI patients had type I disease (n = 24; 65%) but type III–VII patients were also included. Two patients had clinically overt bilateral keratoconus. OI patients had significantly higher maximum keratometry (45.2 ± 2.1 vs. 43.7 ± 1.2; p = 0.0416), front and back elevation (3.0 ± 3.3 vs. 2.1 ± 1.3, p = 0.0201; 11.1 ± 8.2 vs. 5.0 ± 3.7, p < 0.0001), index of surface variance (25.5 ± 13 vs. 17.4 ± 8.3; p = 0.0016), index of vertical asymmetry (0.21 ± 0.14 vs. 0.15 ± 0.06; p = 0.0215), index of height asymmetry (9.2 ± 14 vs. 6.0 ± 4.5; p = 0.0421), index of height decentration (0.02 ± 0.01 vs. 0.01 ± 0.01; p < 0.0001) and average pachymetric progression (1.01 ± 0.19 vs. 0.88 ± 0.14; p < 0.0001) readings. Thinnest corneal thickness and maximum Ambrósio relational thickness were significantly lower (477 ± 52 vs. 543 ± 26; 387 ± 95 vs. 509 ± 49; p < 0.0001). Two-thirds of OI patients had corneas with a minimum thickness < 500 µm. BAD-D value was significantly higher in OI patients (2.1 ± 1.4 vs. 0.9 ± 0.2; p < 0.0001).ConclusionOI patients showed significant changes in corneal profiles compared with healthy subjects. A high proportion of patients had tomographically suspect corneas when using keratoconus diagnostic indices. Further studies are warranted to assess the true risk of corneal ectasia in OI patients.

The Keratectasia Volume (KEV) in Corneal Topography to Evaluate the Effect of Corneal Collagen Cross-linking in Pediatric Keratoconus.

The study aimed to evaluate the keratectasia volume (KEV) before and after corneal cross-linking (CXL) in pediatric patients. This study included 40 eyes of 25 pediatric patients (10-19years) undergoing standard CXL. The support vector machine (SVM) algorithm was applied to transform mass pixels in corneal topography into a three-dimensioned model to calculate the KEV. The KEV, Kmax, K1, K2, Kave, keratectasia area (KEA), and thinnest corneal thickness (TCT) were determined before CXL and at 3, 6, and 12months after surgery. The correlation between KEV and other parameters (Kmax, TCT, max decentration, eccentricity, and so on) was calculated. The KEV was 4.75 ± 0.74 preoperatively and 4.43 ± 1.22 postoperatively at last follow-up (p < 0.002). There was strong positive correlation between the KEV and Kmax (r = 0.806, p < 0.0005). The preoperat ive KEV was 4.32 ± 0.69 in mild to moderate keratoconus (Kmax < 58D) and 5.27 ± 0.37 in advanced keratoconus (Kmax > 58D) (p < 0.0005, t-test). Postoperative KEV and K readings remained stable at the early stage, and the KEV showed a more drastic decreasing trend than Kmax at sixth month. Statistical significance was found in the KEV between preoperative and 6months after surgery (p < 0.0005), but not in Kmax and other parameters. In 83.3% (15 eyes out of 18 eyes) of the eyes, the preoperative KEV was greater than 4.6 in patients with significant flattening after CXL. Compared with K readings, the KEV can be regarded as a more sensitive index to evaluate the postoperative morphological changes after CXL in pediatric patients.

Age-related changes in Scheimpflug corneal densitometry and their correlations with corneal topographic measurements in a healthy Chinese population.

Objective measurement of corneal densitometry (CD) values can be used to assess corneal transparency and health status, to investigate corneal diseases, and to review anterior segment surgeries. However, literature regarding the association between CD and corneal parameters in healthy adolescent and older individuals is limited. This study investigated age-related changes in Scheimpflug CD values and their correlations with age, sex, and corneal topographic parameters. This retrospective cross-sectional observational study included 347 eyes from 181 consecutive healthy Chinese participants aged between 5 and 90 years. They were divided into 9 age groups: 5-9, 10-19, 20-29, 30-39, 40-49, 50-59, 60-69, 70-79, and 80-90 years. CD and corneal topographic measurements were measured using the Oculus Pentacam. To evaluate CD, the cornea was divided into 3 layers according to depth (anterior 120 µm, central, and posterior 60 µm), and into 4 annular regions according to diameter (0-2, 2-6, 6-10, and 10-12 mm). CD across different depths and regions was positively correlated with age (all P values <0.001). Of the 3 layers of corneal thickness, CD was highest in the anterior 120 µm and lowest in the posterior 60 µm (all P values <0.05). Among the 4 annular regions spanning the corneal diameter, the lowest CD values were 6-10, 2-6, and 0-2 mm at 5-29, 30-69, and 70-89 years, respectively. The highest CD values were 10-12 mm at 5-79 years, and 6-10 mm at 80-90 years (all P values <0.05). CD values of 10-12 mm in the anterior 120 µm corneal layer were significantly lower in men than in women (Z=-2.353; P=0.019). CD of 0-10 mm in each layer was not significantly different between sexes (all P values >0.05). Corneal topographic measurements, including flat-axis keratometry (K1), steep-axis keratometry (K2), and spherical aberration, were slightly positively correlated with age and CD (all P values <0.05). However, central corneal thickness (CCT) and thinnest corneal thickness (TCT), and age or CD showed no correlation (all P values >0.05). With age, CD, keratometry, and spherical aberration gradually increased, while the corneal thickness did not change significantly.