Different Stages Of Keratoconus Research Articles

Is there a relationship between the keratoconus and the peripapillary choroidal vasculature?

To evaluate the peripapillary/parapapillary choroidal vascular parameters in the keratoconus (KC) and to determine the relationship between topography parameters and the peripapillary/parapapillary choroidal vascular parameters. Ninety eyes of ninety patients with different stages of KC and 29 eyes of twenty-nine patients without KC were enrolled in the study. Patients with KC were divided into three groups according to the Amsler-Krumeich classification scale. The choroidal vasculature was assessed by choroidal vascular parameters [such as parapapillary choroidal microvascular density (pCMVd) and peripapillary choroidal vascularity index (pCVI)]. These parameters were also evaluated for correlation with other parameters. The retinal nerve fibre layer thickness (RNFLT) of the superior-temporal area and the pCVI were decreased in group 3 compared to the control group (superiror-temporal RNFLT: 122.27 ± 21.43 vs 139.90 ± 21.7, p = 0.01 and pCVI: 67.04 ± 4.14 vs 69.99 ± 4.38, p = 0.04). The superior-temporal RNFLT was decreased in group 3 compared to group 2 (122.27 ± 21.43 vs 141.83 ± 25.58, p = 0.006). There was a negative correlation between pCVI and average simulated keratometry (mean sim K), but this association was weak (r = -0.29 p = 0.001). This study demonstrated that there may be changes in pCVI in patients with grade 3 KC and that there may be an association between pCVI and mean sim K. As KC grade increases, pCVI may decrease. Furthermore, pCVI may have a negative correlation with mean sim K.

Associations between endothelial cell characteristics and corneal topography findings in different stages of keratoconus.

This study aimed to compare and correlate specular microscope indices and corneal topography indices in different stages of keratoconus. Two hundred forty-six eyes of 123 participants were enrolled in the study. Corneal topography was performed using Sirius (CSO, Italy), with a rotating Scheimpflug camera and a Placido disc topographer. Corneal endothelial cell indices were assessed using a specular microscope (Nidek CEM-530, Japan). Eyes were graded as keratoconus stages 0-4 according to the Amsler-Krumeich classification. Corneal topography and endothelial cell indices were compared among the groups, and the correlations between them were analyzed. The mean age of the patients was 23.26 ± 6.75years (range, 14-47years). Forty-eight cases were male (39%) and 75 were female (61%). There were no statistically significant age (p = 0.578) or sex ratio (p = 0.529) differences between the groups. Twenty-nine eyes were included in the control group (11.78%), while 41 (16.67%) had stage 1 keratoconus, 88 (35.77%) had stage 2, and 88 (35.77%) had stage 3. Measurement was not possible in stage 4 keratoconus. No statistically significant difference was determined in specular microscopy values according to the stage of keratoconus, except for the number of analyzed cells (NUM) (p > 0.05). The lowest NUM values were observed in stages 1, 2, and 3, with values of 184.34 ± 67.62 cells/mm2, 155.07 ± 59.48 cells/mm2, and 127.06 ± 64.39 cells/mm2, respectively (p = 0.001). In the keratoconus group, weak statistically significant negative correlations were observed between NUM and SimK1, SimK2, KVf, BCVf, KVb, and BCVb, while a weak positive correlation was noted between NUM and central corneal thickness (p < 0.05). NUM seems to decrease, while endothelial cell density exhibits no significant changes, with the progression of keratoconus. It appears that as keratoconus index values increase, NUM may decrease in different stages of keratoconus.

Corneal Layer Thickness Mapping With Optical Coherence Tomography in Different Stages Reveals Pathologic Processes of Keratoconus.

The aim of this study was to characterize the corneal layer thickness profile in different stages of keratoconus (KC). Patients with clinical or subclinical KC without a history of contact lens use were retrospectively enrolled. We evaluated 164 eyes, including 69 clinical KC, 32 topographic KC (no clinical signs), 22 very asymmetric ectasia with normal topography and no clinical signs of ectasia (VAE-NT), and 41 control eyes. The corneal epithelial, stromal, and total thicknesses in a 10-mm diameter were evaluated using swept-source anterior segment optical coherence tomography. The epithelial thickness in the control and VAE-NT groups was thicker inferiorly than superiorly. While epithelial thickness parameters between the VAE-NT and control groups did not differ, significant stromal thinning was observed in the paracentral inferior and midperipheral temporal areas. The epithelium in the topographic and clinical KC groups was thinner than that in the control and VAE-NT groups, with focal thinning of the epithelium in the inferior-temporal area. In clinical KC, stromal thinning increased mainly in the central and paracentral inferior/temporal areas. With KC progression, the thinnest epithelial points tended to be placed temporally and inferiorly. Corneal layer thickness mapping using swept-source optical coherence tomography in a 10-mm diameter cornea across various severities of KC, from very mild to advanced, revealed that epithelial and stromal thicknesses changed with KC severity and was involved in the pathogenesis of KC progression. Pathological changes in the stroma may precede those in the epithelium. Epithelial compensatory mechanisms in clinical and topographic KC may not have fully emerged in VAE-NT.

Quantitative evaluation of morphological and functional changes in meibomian glands and lipid layer thickness in patients with and without keratoconus.

To quantitatively evaluate the morphological parameters of meibomian glands (MGs) and lipid layer thickness (LLT) in patients with keratoconus (KC). In this prospective, cross-sectional study, 164 eyes of 164 keratoconus patients and 64 eyes of 64 age-matched control subjects were included. An advanced automatic MG analyzer was used to quantitatively measure the morphological and functional parameters of MGs. Morphological and functional parameters of MGs, LLT, and other ocular surface parameters were compared between the control and KC groups. The mean meibomian gland diameter, length, square, and gland area ratio (GA) were all significantly decreased in the KC group (all P < 0.05), while no significant difference was observed in the gland tortuosity index (TI) and gland signal index (SI) between the KC and control groups (all P > 0.05). There was no significant difference in the number of total and incomplete blinking among patients with different stages of keratoconus (all P > 0.05). The gland diameter, square, and TI were all negatively associated with KC severity (all P < 0.05), while no significant difference was observed among all stages of KC in gland length, GA, and SI (all P > 0.05). Moreover, the LLTs were positively correlated with the gland diameter, square, GA, and TI and negatively correlated with anterior corneal curvature or KC severity (all P < 0.05). Atrophic morphological changes in the meibomian glands were closely correlated with the severity of keratoconus. Gland diameter may be a sensitive functional morphology metric of meibomian glands in patients with keratoconus.

Методы тонометрии при кератоконусе

Measurement of intraocular pressure (IOP) in keratoconus is associated with significant difficulties. Thus, because of corneal protrusion and changes in its biomechanics, the most common method of IOP measurement, applanation tonometry, provides significant error. The emergence of novel methods that are less dependent on corneal biomechanics has partially eliminated this error. These methods include tonometry based on new principles and dynamic contour tonometry. One of the "gold standards" for IOP measurement is Goldmann tonometry. Most foreign studies compare Goldman tonometry and one or more of the above-mentioned novel methods. However, in keratoconus, Goldman tonometry underestimates the IOP level and is therefore non-informative. Few studies compare IOP measurements and Maklakov tonometry. Finally, very few studies have compared IOP measurements at various stages of keratoconus, and their results are controversial. Comparing tonometry at different stages of keratoconus and studying fundamental changes in the hydrodynamics in keratoconus are relevant tasks in ophthalmology today. KEYWORDS: cornea, keratoconus, tonometry, intraocular pressure, hydrodynamics, gold standard. FOR CITATION: Averich V.V., Volzhanin A.V. Tonometry in keratoconus. Russian Journal of Clinical Ophthalmology. 2024;24(1):36–40 (in Russ.). DOI: 10.32364/2311-7729-2024-24-1-7.

Биомеханические свойства роговицы в норме и при прогрессирующем кератоконусе

A prospective study of corneal stiffness parameter of 173 eyes of 173 healthy subjects with different refractions as well as 41 eyes with keratoconus was carried out. The study groups were comparable in age and gender composition. Correlation was performed between corneal stiffness parameter (Stiffness Parameter (SP-A1), minimum corneal thickness (MCT) and biomechanically compensated intraocular pressure (bIOP) determined using Pentacam HR and Corvis ST (OCULUS, Germany), as well as the anteroposterior chamber (APC) value and patient age. Based on multivariate regression analysis, the correlation between corneal stiffness index SPA1, minimum corneal thickness (MCT) and biomechanically compensated IOP (bIOP) in healthy subjects (p = 0.00001, p = 0.005, respectively) as well as in patients with keratoconus (p = 0.00000, p = 0.0032, respectively) was established. Using the obtained data, the tables for determination of corneal stiffness in healthy subjects and patients with different stages of keratoconus, depending on the minimal thickness and level of biomechanically compensated intraocular pressure, were compiled. Application of the tables will allow in practical work to quickly analyze corneal stiffness index which can be used as an important diagnostic criterion in patients with keratectasia. Keywords: corneal stiffness index, biomechanically compensated intraocular pressure, correlation dependence.

The influence of different factors on corneal biomechanical properties in norm and in progressive keratoconus

A prospective study of corneal stiffness parameter of 174 eyes of 174 healthy subjects with different refractions as well as 56 eyes with keratoconus was carried out. The study groups were comparable in age and gender composition. Correlation was performed between corneal stiffness parameter (Stiffness Parameter (SP-A1), minimum corneal thickness (MCT) and biomechanically compensated intraocular pressure (bIOP) determined using Pentacam HR and Corvis ST (OCULUS, Germany), as well as the anteroposterior chamber (APC) value and patient age. Based on multivariate regression analysis, the correlation between corneal stiffness index SPA1, minimum corneal thickness (MCT) and biomechanically compensated IOP (bIOP) in healthy subjects (p = 0.00001, p = 0.005, respectively) as well as in patients with keratoconus (p = 0.00000, p = 0.0032, respectively) was established. Using the obtained data, the tables for determination of corneal stiffness in healthy subjects and patients with different stages of keratoconus, depending on the minimal thickness and level of biomechanically compensated intraocular pressure, were compiled. Application of the tables will allow in practical work to quickly analyze corneal stiffness index which can be used as an important diagnostic criterion in patients with keratectasia.

Measuring the agreement of keratometry readings of four devices in eyes with keratoconus.

To determine the keratometry measurement agreement using Sirius corneal topography and Scheimpflug camera, Tomey corneal topography, Topcon autokeratorefractometer, and Tomey OA-2000 optical biometry in eyes with different severity of keratoconus. In this retrospective study 115 eyes in different stages of keratoconus were divided into 2 groups of mild (stage 1), and moderate to severe keratoconus (stages 2, 3), according to the Amsler-Krumeich classification. Keratometry measurements were obtained using Sirius corneal topography and Scheimpflug camera (phoenix V3.7.01.08), Tomey corneal topography (Tms SW22C-200S-200), Topcon autokeratorefractometer (KR8900), and Tomey optical biometry (OA-2000 Opt-Meas V.4E). In group 1 All devices demonstrated fair agreement in average keratometry values (95% LoA range > 1 D). However, it was poorer for group 2 (95% LOA range > 3 D). In group 1 Bonferroni test revealed statistically significant difference in average K readings among (Topcon autokeratorefractometer 8900 and Tomey OA-2000 biometry, p < 0.01), and between (Tomey topography and Topcon autokeratorefractometer, p < 0.05). Also in group 2 significant difference was observed in the average keratometry of the most instruments (p < 0.01) except for the (Tomey topography and Topcon autokeratorefractometer) and (Tomey topography and Tomey OA-2000 biometry. According to our investigation in mild, moderate and severe keratoconus the agreement in K reading between Topcon autokeratorefractometer, OA-2000 optical biometry, Sirius topography and Tomey topography was poor. The agreement declines especially in the steep meridian and it was not acceptable clinically. These devices should not be applied interchangeably.

Keratoviz-A multistage keratoconus severity analysis and visualization using deep learning and class activated maps

&lt;span lang="EN-US"&gt;The detection of keratoconus has been a difficult and arduous process over the years for ophthalmologists who have devised traditional approaches of diagnosis including the slit-lamp examination and observation of thinning of the corneal. The main contribution of this paper is using deep learning models namely Resnet50 and EfficientNet to not just detect whether an eye has been infected with keratoconus or not but also accurately detect the stages of infection namely mild, moderate, and advanced. The dataset used consists of corneal topographic maps and pentacam images. Individually the models achieved 97% and 94% accuracy on the dataset. We have also employed class activated maps (CAM) to observe and help visualize which areas of the images are utilized when making classifications for the different stages of keratoconus. Using deep learning models to predict the detection and severity of the infection can drastically speed up and provide accurate results at the same time.&lt;/span&gt;

Predicting the Keratoconus Disease Severity Based on Pachymetric Progression Indices Measured by Pentacam

Background Keratoconus (KCN) is a bilateral, progressive, and non-inflammatory disorder in the cornea, which results in thinning and protrusion of the cornea. Objective This study aims to determine the effectiveness of using pachymetric progression indices (PPIs) in grading the severity of KCN disease. Methods In this study, 76 patients with different stages of KCN were enrolled. The severity of KCN was graded according to maximum keratometry, cornea thickness, and spherical equivalent. The PPIs measured by Pentacam and the demographic characteristics were recorded and their correlation with the severity of KCN was assessed. Results In terms of KCN severity, 18% of patients were at grade 1, 31% at grade 2, 42% at grade 3, and 7% at grade 4. The power of PPIs in predicting KCN grade 4, grade 3 and grade 2 based on the area under the curve ranged from 0.722 to 0.993. Conclusion The PPIs (Minimum, Maximum, Average) can predict the severity of KCN disease with good sensitivity and specificity.

Characteristics of Higher-Order Aberrations in Different Stages of Keratoconus.

To characterize higher-order aberrations (HOAs) in clinical and subclinical keratoconus (KC). The study included 33, 36, and 26 patients with clinical, topographic (no clinical signs), and pretopographic (normal topography and no clinical signs) KC and 30 controls. Ocular and corneal HOAs for the 4-mm pupils were measured using a wavefront sensor and expanded up to the sixth order of Zernike polynomials. The magnitudes of trefoil, coma, tetrafoil, secondary astigmatism, and spherical aberration were calculated via Zernike vector analysis and used as HOA parameters along with total HOAs. Area under the receiver operating characteristic curve (AUROC) values for each wavefront parameter for pretopographic KC were compared. Control eyes and eyes with pretopographic KC had significantly lower ocular or corneal total HOAs and Zernike vector terms than those with clinical KC and topographic KC, except for ocular tetrafoil between topographic KC and pretopographic KC and spherical aberration among all groups. The AUROCs for corneal total HOAs and corneal coma for pretopographic KC and control eyes were 0.781 (100% sensitivity and 47% specificity) and 0.735 (73% sensitivity and 73% specificity), respectively. Corneal total HOAs and corneal coma exhibited a potential ability to discriminate pretopographic KC from normal control eyes.

Anterior and posterior corneal higher-order aberrations in early diagnosis and grading of keratoconus

ABSTRACTClinical relevanceEvaluation of corneal higher-order aberrations can be used clinically to diagnose early cases of keratoconus as well as to classify the severity of keratoconus.BackgroundTo investigate the anterior and posterior corneal higher-order aberrations (HOAs) up to the sixth order and their ability to identify early keratoconus (KCN) as well as differentiate different severities of KCN using cross-validation analysis.MethodsThis prospective cross-sectional comparative study was performed at a tertiary eye hospital in Tehran, Iran, in 2019. The study sample consisted of 95 eyes of 95 patients with KCN and 53 eyes of 53 normal individuals. The eyes with KCN were classified into three groups based on the Amsler–Krumeich classification system: group 1 (mild KCN), group 2 (moderate KCN), and group 3 (severe KCN). Corneal wavefront analysis was performed using Pentacam HR.ResultsBased on the magnitude of AUC, posterior vertical secondary coma (Z5−1) had an excellent discriminant ability (AUC: 0.91) and anterior vertical coma (Z3−1) and anterior vertical secondary coma (Z5−1) had a good discriminant ability (0.8 < AUC < 0.89) for differentiating eyes with mild KCN from normal eyes. The anterior and posterior primary spherical aberrations (Z4°) had an excellent ability (AUC > 0.9), and anterior secondary spherical aberration (Z6°) had a good ability (AUC: 0.83) for differentiating moderate from mild KCN. In the differentiation of severe from moderate KCN, anterior and posterior primary aspherical aberrations (Z4°) had a good AUC value (AUC > 0.8).ConclusionComa-like aberrations had a good discriminant ability between normal eyes and eyes with mild KCN. Spherical aberrations showed a good ability for differentiating between different stages of KCN. The cut-off values reported in this study can be used for early detection of KCN as well as classification of KCN severity.

Dissecting the Profile of Corneal Thickness With Keratoconus Progression Based on Anterior Segment Optical Coherence Tomography.

PurposeTo characterize the corneal and epithelial thickness at different stages of keratoconus (KC), using a deep learning based corneal segmentation algorithm for anterior segment optical coherence tomography (AS-OCT).MethodsAn AS-OCT dataset was constructed in this study with 1,430 images from 715 eyes, which included 118 normal eyes, 134 mild KC, 239 moderate KC, 153 severe KC, and 71 scarring KC. A deep learning based corneal segmentation algorithm was applied to isolate the epithelial and corneal tissues from the background. Based on the segmentation results, the thickness of epithelial and corneal tissues was automatically measured in the center 6 mm area. One-way ANOVA and linear regression were performed in 20 equally divided zones to explore the trend of the thickness changes at different locations with the KC progression. The 95% confidence intervals (CI) of epithelial thickness and corneal thickness in a specific zone were calculated to reveal the difference of thickness distribution among different groups.ResultsOur data showed that the deep learning based corneal segmentation algorithm can achieve accurate tissue segmentation and the error range of measured thickness was less than 4 μm between our method and the results from clinical experts, which is approximately one image pixel. Statistical analyses revealed significant corneal thickness differences in all the divided zones (P < 0.05). The entire corneal thickness grew gradually thinner with the progression of the KC, and their trends were more pronounced around the pupil center with a slight shift toward the temporal and inferior side. Especially the epithelial thicknesses were thinner gradually from a normal eye to severe KC. Due to the formation of the corneal scarring, epithelial thickness had irregular fluctuations in the scarring KC.ConclusionOur study demonstrates that our deep learning method based on AS-OCT images could accurately delineate the corneal tissues and further successfully characterize the epithelial and corneal thickness changes at different stages of the KC progression.

Assessment and Correlation of Corneal Endothelial Cell Changes in Different Stages of Keratoconus in Non-contact Lens Wearers.

The endothelial changes in keratoconus are of interest because these can affect the surgical plan in management. Previously, many studies have evaluated the endothelium in eyes with keratoconus, but there is no common consensus on change in endothelial cell density (ECD) with studies showing variable results. This study aimed to compare and correlate endothelial cell parameters in different stages of keratoconus using specular microscope. This cross-sectional, cohort, comparative study included 162 eyes of 96 patients with keratoconus in one or both eyes. Corneal endothelial cell parameters were assessed with SP-1P specular microscope (Topcon Co., Tokyo, Japan). Corneal topography and thickness data were obtained from Sirius tomographer (Costruzione Strumenti Oftalmici, Florence, Italy). Eyes were divided into keratoconus stage 0 to 4 according to ABCD classification. Comparison and correlation of endothelial cell parameters in different stages were done. There were 21.6% eyes (35) in stage 0, 29.6% eyes (48) in stage 1, 29.0% eyes (47) in stage 2, and 19.8% eyes (32) in stage 3 of keratoconus. Measurement was not possible in stage 4 keratoconus. Among the stages 0, 1, 2, and 3, the ECD was 3024, 3051, 3025, and 3043 cells/mm2; coefficient of variation was 27.2, 27.6, 26.8, and 27.4; and frequency of hexagon cells was 61.5, 63.7, 63.3, and 62.3, respectively (P > .05). The number of analyzed cells was 232, 209, 185, and 169 in stages 0, 1, 2, and 3, respectively (P < .001). No significant difference was found in minimum, maximum, and average cell area between the stages (P > .05). A weak Spearman rank correlation of ECD, coefficient of variation, and frequency of hexagon cells was found between eyes with keratoconus stages 0 and 1 and stages 2 and 3 (r = -0.05, P = .65; r = -0.11, P = .37; r = 0.05, P = .67, respectively). No significant correlation was found in the number of cells analyzed and minimum, maximum, and average cell area between the stages (P > .05). Endothelial cell parameters do not show any significant changes and correlation up to stage 3 of keratoconus in non-contact lens wearers.

Evaluation of Corneal Endothelial Changes and Corneal Tomographic Parameters in Eyes with Keratoconus

Purpose: To evaluate changes in corneal endothelium and its correlation with tomographic parameters in different stages of keratoconus (KC).Methods: This study was conducted on 95 eyes of 70 patients with KC attending to Mansoura ophthalmic center and 40 normal controls with matching age and sex in the period from April 2018 till May 2019. All individuals were subjected to full history and ocular examination. In addition Oculus pentacam was performed to diagnose KC, grades and assessment of Keratometry, thickness at the apex, thinnest corneal thickness and Anterior and Back elevation, while Specular microscopy was performed to assess the endothelial cell counting, Coefficient of variation (C/V) and Hexagonal cell ratio.Results: There were highly statistically significant differences among KC cases and the control group as regards endothelial count, C/V and hexagonal cell ratio. In addition such changes had a positive correlation with the degree of KC. Conclusion: There were significant corneal endothelial changes as well as Corneal Tomographic alterations among eyes with KC compared to normal ones and these changes have a positive correlation with the severity of KC. Specular microscopic examinations in patients with KC provide important data in addition to topography.

Corneal densitometry in different stages of keratoconus

Purpose: The aim of this study was to evaluate corneal clarity in keratoconic patients using corneal densitometry. Methods: comparing corneal densitometry results among keratoconic patients and normal individual was measured over a 12- mm diameter area, divided by annular concentric zones and depths. Keratoconus was classified according to the topographic keratoconus classification, from March 2019 to March 2020 in Ophthalmic center Mansoura University, Egypt. Results: Group 1: 20 eyes diagnosed as manifest grade 1 keratoconus; Group 2: 20 eyes diagnosed as manifest grade 2 keratoconus; Group 3: 20 eyes diagnosed as manifest grade 3 keratoconus; Group 4: 20 eyes diagnosed as manifest grade 4 keratoconus; with 40 eyes normal topographic parameter a control group. the comparison between the studied groups regarding anterior (120 mm), central (from 120 mm to the last 60 mm) and posterior (last 60 mm) layers measurements showed increase in corneal densitometry reading in 0-2 mm, 2-6 mm, 6-10 mm, 10-12 mm zones in keratoconous patient and compared to control group, there was significantly increased in densitometry readings in keratoconous eyes and was related to keratoconous severity. Conclusions: The densitometry readings increase in keratoconic eyes with higher values with increasing severity of keratoconus. Whitch may add valuable data for early diagnosis of keratoconus.

Corneal endothelial cells changes in different stages of Keratoconus: a multi-Centre clinical study

PurposeTo assess the corneal endothelial cells morphology and count in keratoconus patients and their correlation with different stages of keratoconus.MethodsProspective non randomized multi-centric clinical study included 150 eyes of 150 keratoconus patients. Four centers in Egypt participated in this study included: Departments of Ophthalmology in Alexandria University, Tanta University and Port Said University and Alex I-Care hospital. Pentacam (Wavelight Oculyzer II) and specular microscopy (Tomey EM-3000) were done to all eyes. Keratoconic eyes were classified according to Amsler classification into stage 1, 2 and 3. Stage 1 included 99 eyes, stage 2 included 32 eyes & stage 3 included 19 eyes.ResultsThe mean age of keratoconus patients was 24.07 ± 6.154 years. Forty five cases were males (30%) and 105 cases were females (70%). There was statistically significant difference in endothelial cell density (p < 0.001) and coefficient of variation (p = 0.012) between different stages of keratoconus eyes. Regarding cell surface area, there was statistically significant difference in cell surface area between different stages of keratoconus eyes (p < 0.001). In addition, for cell morphology, there was statistically significant difference between different stages of keratoconus eyes (p < 0.001).ConclusionsQualitative and quantitative structural changes were seen in endothelial cells of keratoconus eyes by using specular microscopy. For stages 1 and 2, keratoconus may not affect the corneal endothelim significantly. The endothelium in stage 3 shows significant changes regarding polymegathism and pleomorphism.

Agreement of keratometric readings measured using rotating Scheimpflug imaging, auto-refractokeratometer, and biograph in eyes with keratoconus.

To determine agreement in keratometric readings obtained using rotating Scheimpflug imaging with Pentacam, biograph with Lenstar LS900, and Topcon KR-8100P auto-keratorefractometer in eyes with different stages of keratoconus. A total of 89 eyes of 58 patients with keratoconus were examined in this study, retrospectively. The eyes were divided into two groups: mild group (group 1: 42 eyes) (Amsler-Krumeich stage 1) and moderate-to-severe group (group 2: 47 eyes) (Amsler-Krumeich stage 2, 3, 4). The keratometric readings measured using the Pentacam Scheimpflug system, Lenstar LS900, and Topcon KR-8100P auto-keratorefractometer were compared between the groups. The effects of the measurements of anterior chamber depth, Q value, axial length, central corneal thickness (CCT), and maximum value of keratometry (Kmax) on the differences of devices for keratometric readings were investigated. The mean values of the keratometric readings obtained using the Lenstar were steeper than with the Pentacam and Topcon, especially in group 2. In group 1, the mean K2 values measured using the Lenstar were significantly steeper than with the Topcon (p < 0.05); however, the devices were accordant for the other keratometric readings. In group 2, there was an agreement between the Pentacam and Topcon for the mean K1 and Km values; however, there were significant differences between the devices for the other values. The Q value and CCT had a negative correlation, and Kmax had a positive correlation with the differences of Lenstar-Pentacam and Lenstar-Topcon (p < 0.01). According to our results, Pentacam-Topcon and Pentacam-Lenstar can be used interchangeably for keratometry in mild stages of keratoconus. The keratometric readings of Lenstar were found steeper than the other devices with increasing grades of keratoconus. None of these devices can be used interchangeably in moderate-to-severe stages of keratoconus.

Changes in the Optical Corneal Densitometry, Visual Acuity, and Refractive Error after the Annular Intracorneal Inlay Implantation.

Purpose:To investigate the changes in the optical corneal densitometry as an objective method in assessing the corneal light back-scattering before and 1 year after the annular intracorneal inlay (AICI) implantation into the keratoconic corneas.Methods:Changes in the optical corneal densitometry, visual acuity, refractive, and tomographical status were assessed before and 1 year after the AICI implantation into the corneas with different stages of keratoconus. Optical corneal densitometry was evaluated using the Pentacam-HR in 0–2, 2–6, 6–10, and 10–12 mm rings in the anterior 120 μ, central layers, posterior 60 μ and also the total value were measured for cornea in the Grey Scale Unit criterion.Results:Totally, 34 patients with keratoconus were studied; the uncorrected and best corrected visual acuity were increased after the surgery (0.98 ± 0.25 to 0.53 ± 0.30 logMAR, P < 0.001 and 0.26 ± 0.18 to 0.19 ± 0.14, P = 0.007 logMAR, respectively); the spherical equivalent was decreased from −4.45 ± 2.25 to − 2.06 ± 2.01 D (P = 0.004). AICI implantation led to an increase in the amount of optical corneal densitometry in 0–2 mm central, 2–6 mm central, 6–10 mm central, total central, 2–6 mm posterior, and 2–6 mm total rings (all, P < 0.05); however, a decrease was observed in 0–2 mm anterior ring (P = 0.049). Results of statistical analysis showed that the total optical corneal densitometry, anterior total, and posterior total back-scattering did not change after the AICI implantation (all, P > 0.05).Conclusions:Our results revealed a significant improvement in the visual function, including refractive error and visual acuity following the AICI implantation. Changes in the optical corneal densitometry were different in distinct regions and layers however, the total amount did not change after the AICI implantation.

Repeatability and reliability of measurements obtained by the combined Scheimpflug and Placido-disk tomography in different stages of keratoconus.

The objective of this study is to evaluate the repeatability and reliability of corneal parameters in different stages of keratoconus patients using a combined Scheimpflug-Placido disc analysis system. In this prospective study, three consecutive measurements were performed by the same observer using Scheimpflug-Placido disc anterior segment analysis device in keratoconus patients. Flattest and steepest simulated keratometry and corneal volume, corneal aberrations, thinnest corneal thickness, symmetry index, keratoconus vertex and Baiocchi-Calossi-Versaci index were recorded. Keratoconic eyes were divided into four stages using the Amsler-Krumeich classification. Repeatability was evaluated using within the subject standard deviation, repeatability index (Ri) and coefficient of variation; reliability was evaluated by intraclass correlation coefficient (ICC). Pearson correlation coefficients were used to assess the correlation between the parameters evaluated. Two hundred sixty-one eyes of 261 keratoconus patients were included in the study. The repeatability for all corneal curvature parameters decreased as the keratoconus severity increased, and there is a positive correlation between keratometry of the apex and corneal curvature parameters (p < 0.05) except mean simulated keratometry. The corneal aberrations were repeatable in all keratoconus subgroups (Ri < 0.34 μm). There are also positive correlations between keratometry of apex and corneal aberrations (p < 0.05) except total high-order root mean square and spherical aberration. The reliability was excellent (ICC > 0.90) for all indices except keratoconus vertex back. The parameters used in the diagnosis and follow-up of keratoconus in the Sirius corneal tomography system may differ more than expected at stages 3 and 4 of the disease. Awareness of this situation may be helpful in planning follow-up and treatment.