Quantitative comparison of corneal surface areas in keratoconus and normal eyes (original) (raw)
Related papers
Corneal thickness and volume in subclinical and clinical keratoconus
International …, 2012
To evaluate corneal thickness and volume in subclinical and clinical keratoconus in Asian population with the aim of discriminating between normal and ectatic cornea. Eyes were placed into one of the following three groups: normal, subclinical, and mildmoderate keratoconus. Pentacam Scheimpflug imaging (Oculus Inc., Wetzlar, Germany) was performed for each participant to record thinnest corneal thickness, central corneal thickness, corneal volume (CV), peripheral corneal thickness (PCT) and percentage thickness increase (PTI) at 2, 4, 6, and 8 mm. The data were exported to SPSS for statistical analysis. Subjects comprised 52 normal, 15 subclinical keratoconus, and 32 mild-moderate clinical keratoconus eyes. Our results indicated that corneal thickness (CT) distribution, PTI, and CV in normal eyes were significantly different compared with subclinical and clinical keratoconus (P \ .05). Overall, subclinical group exhibited lower CT distribution and volume, and higher PTI in comparison with normal eyes. However, they showed higher CT distribution and volume, and lower PTI compared with keratoconus group. In addition, there was a smaller change in PCT and PTI from the thinnest point of the cornea to the periphery. The results of the present study indicate that CT parameters and CV were significantly different in normal versus subclinical group and in normal versus keratoconus group. These findings could help clinicians to better discriminate between normal and ectatic cornea.
Corneal thickness and volume and clinical and subclinical keratoconus
To evaluate corneal thickness and volume in subclinical and clinical keratoconus in Asian population with the aim of discriminating between normal and ectatic cornea. Eyes were placed into one of the following three groups: normal, subclinical, and mildmoderate keratoconus. Pentacam Scheimpflug imaging (Oculus Inc., Wetzlar, Germany) was performed for each participant to record thinnest corneal thickness, central corneal thickness, corneal volume (CV), peripheral corneal thickness (PCT) and percentage thickness increase (PTI) at 2, 4, 6, and 8 mm. The data were exported to SPSS for statistical analysis. Subjects comprised 52 normal, 15 subclinical keratoconus, and 32 mild-moderate clinical keratoconus eyes. Our results indicated that corneal thickness (CT) distribution, PTI, and CV in normal eyes were significantly different compared with subclinical and clinical keratoconus (P \ .05). Overall, subclinical group exhibited lower CT distribution and volume, and higher PTI in comparison with normal eyes. However, they showed higher CT distribution and volume, and lower PTI compared with keratoconus group. In addition, there was a smaller change in PCT and PTI from the thinnest point of the cornea to the periphery. The results of the present study indicate that CT parameters and CV were significantly different in normal versus subclinical group and in normal versus keratoconus group. These findings could help clinicians to better discriminate between normal and ectatic cornea.
[Corneal topography of keratoconus]
Klinika oczna, 1997
The present study was designed to evaluate the topography of a series of keratoconus patients. Using a computer-assisted videokeratography (Eye Sys) we determined the topographic findings of 85 eyes of 46 consecutive patients with keratoconus. We analysed some quantitative topographic parameters like: power at the apex, central corneal power, the amount of irregular astigmatism, distance between the apex and the visual axis, difference in central corneal power between the two eyes of the same individual and steepening of the inferior cornea compared with the superior cornea. Keratoconic topographic alterations were classified into two groups. Fifty seven of the cones (71%) could be described as peripheral with steepening of the cornea extending to the limbus. The remaining twenty three eyes (29%) had steepening confined to the central cornea. In many instances corneal topography was characterized by a high degree of nonsuperimposable mirror image symmetry (enantiomorphism) in the lo...
2021
Keratoconus is a progressive corneal disorder which is frequently asymmetric. The aetiology of keratoconus remains unclear, and the concept of keratoconus as an ectatic disorder has been challenged recently. We carried out a retrospective study in 160 eyes of 80 patients, to evaluate and compare interocular differences in corneal diameter and surface area in patients with unilateral/highly asymmetric keratoconus (UHAKC). Calculations were performed using raw topographic elevation data derived from topographic measurements using Orbscan II, and we extrapolated surface areas up to measured corneal diameter. We also evaluated inter-eye correlation, and correlation between corneal surface area, corneal diameter and keratoconus severity. Our results showed a statistically significant but not clinically important greater corneal diameter (12.14mm and 12.17 mm; p=0.04), and corneal surface area (paired t-test, p<0.0001; p=0.0009 respectively) in more affected eyes. Inter-eye comparison ...
Correlation of Anterior and Posterior Corneal Shape in Clinical Keratoconus
Investigative Ophthalmology & Visual Science, 2016
Purpose: To evaluate the correlation of the mean curvature and shape factors of both corneal surfaces for different corneal diameters measured with the Scheimpflug photography-based system in keratoconus eyes. Methods: A total of 61 keratoconus eyes of 61 subjects, aged 14 to 64 years, were included in this study. All eyes received a comprehensive ophthalmologic examination including anterior segment and corneal analysis with the Sirius system (CSO): anterior and posterior mean corneal radius for 3, 5, and 7 mm (aKM, pKM), anterior and posterior mean shape factor for 4.5 and 8 mm (ap, pp), central and minimal corneal thickness, and anterior chamber depth. Results: Mean aKM/pKM ratio around 1.20 (range, 0.95-1.48) was found for all corneal diameters (P = 0.24). Weak but significant correlations of this ratio with pachymetric parameters were found (r between 20.28 and 20.34, P , 0.04). The correlation coefficient between aKM and pKM was 0.92forallcornealdiameters.Astrongandsignificantcorrelationwasalsofoundbetweenapandpp(r0.92 for all corneal diameters. A strong and significant correlation was also found between ap and pp (r 0.92forallcornealdiameters.Astrongandsignificantcorrelationwasalsofoundbetweenapandpp(r 0.86, P , 0.01). The multiple regression analysis revealed that central pKM was significantly correlated with aKM, central corneal thickness, anterior chamber depth, and spherical equivalent (R 2 $ 0.88, P , 0.01) and that 8 mm pp was significantly correlated with 8 mm ap and age (R 2 = 0.89, P , 0.01). Conclusions: Central posterior corneal curvature and shape factor in the keratoconus eye can be consistently predicted from the anterior corneal curvature and shape factor, respectively, in combination with other anatomical and ocular parameters.
Vector Analysis of Evolutive Corneal Astigmatic Changes in Keratoconus
Investigative Opthalmology & Visual Science, 2011
PURPOSE. To evaluate by vector analysis the corneal astigmatic changes occurring in keratoconic corneas during a 3-year follow-up and to determine the relationship between these changes and other clinical changes. METHODS. Keratoconic eyes (n ϭ 114) of 75 patients ranging in age from 14 to 70 years were retrospectively reviewed in four different centers. In all cases, a 3-year follow-up was completed after the diagnosis of keratoconus. Visual, refractive, keratometric, aberrometric, internal astigmatism (IA), and pachymetric changes were evaluated during the follow-up. In addition, corneal astigmatic changes were evaluated by examining the following parameters, using a modification of the Alpins vectorial method: evolutive astigmatism (EA) and angle of error (AE). RESULTS. An increase in the magnitude of refractive (P ϭ 0.02) and corneal astigmatism (P ϭ 0.05) was found. The mean magnitude of EA was 1.21 Ϯ 0.97 D at 3 years, with no significant changes at each annual visit (P Ն 0.52). Mean absolute AE increased significantly by the end of the follow-up (P Ͻ 0.01). Absolute AE and the increase in corneal astigmatism were found to correlate at 2 years (r ϭ 0.675, P Ͻ 0.01). This correlation became poorer at 3 years (r ϭ 0.352, P ϭ 0.02). The magnitude of the EA was also found to be significantly correlated with central corneal thinning (r ϭ Ϫ0.441, P ϭ 0.02). Multiple regression analysis revealed that the magnitude of EA at 3 years correlated significantly with the baseline sphere and IA (R 2 ϭ 0.86, P Ͻ 0.01). CONCLUSIONS. Corneal vector astigmatic changes are related to some signs of keratoconus progression and are therefore predictive.
Purpose: To identify corneal epithelial- and stromal-thickness distribution patterns in keratoconus using spectral-domain optical coherence tomography (SD-OCT). Patients and Methods: We analyzed SD-OCT findings in 20 confirmed cases of keratoconus (group 1) and in 20 healthy subjects with corneal astigmatism $2 D (group 2). Epithelial and stromal thicknesses were measured at 11 strategic locations along the steepest and flattest meridians, previously located by corneal topography. Vertical mirrored symmetry superimposition was used in the statistical analysis. Results: The mean maximum keratometry measurements in groups 1 and 2 were 47.962.9 D (range, 41.8–52.8) and 45.661.1 D (range, 42.3–47.5), respectively, with mean corneal cylinders of 3.362.2 D (range, 0.5–9.5) and 3.661.2 D (range, 2.0–6.4), respectively. The mean epithelial thickness along the steepest meridian in group 1 was the lowest (37.464.4 mm) at 1.2 mm inferotemporally and the highest (59.364.4 mm) at 1.4 mm supranasally from the corneal vertex. There was only a small deviation in thickness along the steepest meridian in group 2, as well as along the flattest meridians in both groups. The stromal thickness distribution in the two groups was similar to the epithelial, while the stromal thickness was generally lower in group 1 than in group 2. Conclusions: SD-OCT provides details about the distribution of corneal epithelial and stromal thicknesses. The epithelium and stroma in keratoconic eyes were thinner inferotemporally and thicker supranasally compared with control eyes. The distribution pattern was more distinct in epithelium than in stroma. This finding may help improve the early diagnosis of keratoconus.