Index Of Surface Variance Research Articles

Diagnosis of forme fruste keratoconus with scheimpflug photography in Ghanaian patients

AimThis study aimed to differentiate moderate to high myopic astigmatism from forme fruste keratoconus using Pentacam parameters and develop a predictive model for early keratoconus detection.MethodsWe retrospectively analysed 196 eyes from 105 patients and compared Pentacam variables between myopic astigmatism (156 eyes) and forme fruste keratoconus (40 eyes) groups. Receiver operating characteristic curve analysis was used to determine the optimal cut-off values, and a logistic regression model was used to refine the diagnostic accuracy.ResultsStatistically significant differences were observed in most Pentacam variables between the groups (p < 0.05). Parameters such as the Index of Surface Variance (ISV), Keratoconus Index (KI), Belin/Ambrosio Deviation Display (BAD_D) and Back Elevation of the Thinnest Corneal Locale (B.Ele.Th) demonstrated promising discriminatory abilities, with BAD_D exhibiting the highest Area under the Curve. The logistic regression model achieved high sensitivity (92.5%), specificity (96.8%), accuracy (95.9%), and positive predictive value (88.1%).ConclusionThe simultaneous evaluation of BAD_D, ISV, B.Ele.Th, and KI aids in identifying forme fruste keratoconus cases. Optimal cut-off points demonstrate acceptable sensitivity and specificity, emphasizing their clinical utility pending further refinement and validation across diverse demographics.

Changes in Astigmatism after Surgery in Pediatric Patients with Limbal Dermoid

Purpose: To analyze changes in astigmatism and visual acuity in pediatric patients with limbal dermoid before and after surgery.Methods: Twenty-five pediatric patients (7 male, 18 female) diagnosed with limbal dermoid from March 2018 to February 2022 were included. We analyzed best corrected visual acuity and astigmatism using cycloplegic refraction, automated keratometry, and topography before and after surgery.Results: In cycloplegic refraction and automated keratometry, postoperative astigmatism did not decrease significantly (p = 0.53 and p = 0.38, respectively). Topography showed a significant decrease in corneal astigmatism from 3.6 ± 2.8 diopters (D) to 2.7 ± 1.8 D (p &lt; 0.05) and in irregular astigmatism from 3.7 ± 2.2 D to 2.5 ± 1.5 D (p &lt; 0.001). Significant decreases were observed in the corneal irregularity index from 0.14 ± 0.10 mm to 0.08 ± 0.47 mm (p &lt; 0.001) and in the index of surface variance from 60.56 ± 41.02 to 35.00 ± 16.00 (p &lt; 0.001). There was a statistically significant improvement in best corrected visual acuity from logarithm of minimal angle of resolution (logMAR) 0.18 to logMAR 0.07 (p &lt; 0.05).Conclusions: Surgery for limbal dermoid significantly reduced irregular astigmatism and improved best-corrected visual acuity. It is suggested that achieving visual development through active amblyopia treatment after surgery is important.

Factors predicting the visual outcome of intracorneal ring segment for keratoconus.

To identify predictive factors and to construct predictive models using epidemiological and clinical preoperative factors for the visual acuity change after intracorneal ring segment (ICRS) implantation in patients with keratoconus. The medical records of 287 keratoconic eyes of 230 patients implanted with ICRS at Chula Refractive Surgery Center of a tertiary university hospital (Bangkok, Thailand) between January 2012 and March 2022 were retrospectively reviewed for epidemiological and clinical preoperative variables, including those derived from Scheimpflug tomography. After randomly excluding one eye for each bilateral case, the remaining 230 eyes were randomized into two groups: a training group (184 eyes) and a validation group (46 eyes). In the training group, the correlation between the interesting variables and postoperative uncorrected and corrected distance visual acuity change (ΔUDVA and ΔCDVA; logMAR scale) at 6 months was explored, and then the multiple linear regression analysis was used to develop the predictive models. The obtained models were tested using the validation group. There were 5 and 14 preoperative variables that statistically correlated with ΔUDVA and ΔCDVA respectively. Only the preoperative corrected distance visual acuity (CDVAp) strongly correlated with ΔCDVA (Beta = -0.746). Using multiple regression, the preoperative uncorrected distance visual acuity (UDVAp) and front mean keratometry were selected in the proposed model for ΔUDVA (adjusted R2 = 38.8%), while the CDVAp and index of surface variance (ISV) were selected in the model [Formula: see text] (adjusted R2 = 48.9%). The ΔUDVA and ΔCDVA models were correct in 47.83% and 63.4% of the validation group within 0.20 logMAR, respectively. Potential predictive factors and models for ICRS-induced changes in visual acuity are proposed as adjunctive tools for clinicians. Such tools could be used for case selection and during counselling before ICRS implantation to maximize surgical outcomes.

Analysis of the effect of keratotopographic parameters on tonometric intraocular pressure

BACKGROUND: Applanation tonometers remain popular in most countries of the world; in Russia, the Maklakov tonometer is one of them. When using a Maklakov tonometer, intraocular pressure values are obtained indirectly through the cornea, which has individual characteristics, which certainly introduces its own errors into the accuracy of the measurement results.&#x0D; AIM: The aim of this study was to investigate the influence of keratotopographic parameters on tonometric intraocular pressure.&#x0D; MATERIALS AND METHODS: A study of 16 keratotopographic indices (using ALLEGRO Oculyzer Wavelight Oculyzer II) and of tonometric intraocular pressure values obtained using Maklakov tonometer (NGm2-“OFT-P”) was carried out in 500 patients (1000 eyes). Among the study population there were patients with both emmetropic refraction — 8 eyes (0.8%), and patients with refractive errors 992 eyes (99.2%), among them: 978 eyes (97.8%) had myopic refraction 14 (1.4%) eyes had isolated refraction with myopic astigmatism. 889 eyes (88.9%) combined myopic refraction with myopic astigmatism.&#x0D; RESULTS: Based on the analysis of 16 keratotopographic parameters and tonometric intraocular pressure values, 500 patients (1000 eyes), the greatest influence of 13 studied parameters of the cornea was determined, such as: K1 (keratometry of flatter meridian); K2 (keratometry of steeper meridian); Km (mean keratometry); Rf (radius of the flatter meridian); Rs (radius of the steeper meridian); Rm (mean radius of curvature); Rmin (minimal radius of curvature); Rper (average radius of curvature between the 6 mm and 9 mm zone center); IVA (index of vertical asymmetry); ISV (index of surface variance); CKI (central keratoconus index); Thickness (thickness); IHD (index of height decentration) — on intraocular pressure values.&#x0D; CONCLUSIONS: Based on the results obtained, we determined the effect of topographic parameters of the cornea on tonometric intraocular pressure, and created a formula for correcting intraocular pressure values based on the original formula we developed: Pt keratotopographic corrected = Pt + (±ISVp) + (±IVAp) + (±Rmp) + (±Kmp) + (±CKIp) + (±Thicknessp), where Pt keratotopographic corrected is the corrected tonometric intraocular pressure and Pt is the tonometric intraocular pressure.

Corneal topographic indices of Scheimpflug camera in type 2 diabetic and non‐diabetic elderly population

Aims/Purpose: To determine the corneal topographic indices of Scheimpflug camera in type 2 diabetic and non‐diabetic in elderly population of Tehran, Iran.Methods: A total of 1105 subjects were selected using random cluster sampling from Tehran, Iran and categorized into two groups including diabetics and non‐diabetics. The diabetic group had HbA1c levels ≥6.4% with no other systemic problems. The non‐diabetic participants had normal eye findings and no systemic diseases. The keratometry values, Q‐value, index of surface variance (ISV), index of vertical asymmetry (IVA), central keratoconus index (CKI), keratoconus index (KI), index of height asymmetry (IHA), index of height decentration (IHD), anterior average radius of curvature (ARC), posterior average radius of curvature (PRC), and pachymetric progression index (PPI) values were measured using the Pentacam AXL.Results: A total participants included 429 diabetic (38.46% male) and 676 non‐diabetic (38.76% male). Only PPIavg and PPImax were higher in the diabetics versus non‐diabetics (p = 0.019 and p = 0.010, respectively). The HbA1c level was 5.47 ± 0.34, 6.70 ± 0.17, and 8.72 ± 1.16 in the first, second, and third group, respectively. There was a significant difference in PPImax between the three groups (p = 0.036). There were significant differences only in IVA, CKI, PPIAvg, and PPImax between different stages of DR (p = 0.045, p = 0.005, p = 0.002, and p = 0.004, respectively). The diabetic subjects were divided into two groups based on the presence of DR. There was a significant difference in ISV, IVA, PPIavg, and PPImax between diabetic subjects with and without DR (p = 0.016, p = 0.022, p &lt; 0.001, and p &lt; 0.001, respectively).Conclusions: The results of this study showed that DM and DR change several topographic indices and the HbA1c level may affect PPImax. Therefore, special attention should be paid to these patients for different treatment strategies.

Corneal topographic indices of scheimpflug camera in type 2 diabetic and non-diabetic elderly populations

PurposeThe present study was conducted to determine the corneal topographic indices of Scheimpflug camera in type 2 diabetes patients without diabetic retinopathy (DR), DR and non-diabetic elderly populations.MethodsA total of 1105 participants were selected using random cluster sampling from Tehran, Iran and categorized into three groups including type 2 diabetes patients without diabetic retinopathy (DR), DR and non-diabetic. The diabetic group had HbA1c levels ≥ 6.4% with no other systemic problems. The non-diabetic participants had normal eye findings and no systemic diseases. The pachymetric progression index (PPI) values were measured using the Pentacam AXL.ResultsA total of 1105 participants including 429 diabetes patients (38.46% male) and 676 non-diabetic (38.76% male) subjects entered the study. Only PPIavg and PPImax were higher in the diabetics versus non-diabetics (P = 0.019 and 0.010, respectively). There was a significant difference in PPImax between the three groups (P = 0.036). There were significant differences only in index of vertical asymmetry (IVA), central keratoconus index (CKI), PPI average, and PPI max between different stages of diabetic retinopathy (DR) (P = 0.045, 0.005, 0.002, and 0.004, respectively). There was a significant difference in index of Surface Variance (ISV), index of vertical asymmetry (IVA), PPIavg, and PPImax between diabetes patients with and without DR (P = 0.016, 0.022, < 0.001, and < 0.001, respectively).ConclusionAccording to the results, diabetes and DR change several topographic indices. In addition, the HbA1c level may affect pachymetric progression index max. Therefore, special attention should be paid to these patients for different treatment strategies.

Keratometric Study of Cornea in Allergic Conjunctivitis Patients

Background: To explore corneal biomechanical changes, identify related factors and determine early indicators of keratoconus (KC) development risk in allergic conjunctivitis (AC) patients. Methods: A total of 50 patients, including 20 eyes without AC and 30 eyes with AC were enrolled in this study. All patients underwent a complete ocular examination, including evaluations of clinical manifestations of AC, corneal tomography and densitometry by Pentacam, corneal biomechanics by Corvis ST, and corneal and epithelial thickness mapping by RTvue optical coherence tomography (OCT). Results: The index of surface variance (ISV), index of vertical asymmetry (IVA), keratoconus index (KI), index of height decentration (IHD) and Belin/Ambrosio enhanced ectasia total deviation index (BAD-D) were significantly higher in the AC group than in the non-allergic conjunctivitis (NAC) group (P &lt; 0.05). The tomography and biomechanical index (TBI) was also significantly higher in the AC group (P =?0.04). The average epithelial thickness in the 2–7?mm annulus was significantly thinner in the AC group than in the NAC group (P &lt; 0.05). The average densitometry of the total cornea and the anterior layer were higher in the AC group than in the NAC group (P &lt; 0.001). The ISV, IVA, KI, IHD and BAD-D were significantly correlated with the TBI and changes in corneal epithelial thickness in AC patients (P &lt; 0.05). The changes in epithelial thickness were closely related to the eye rubbing frequency and allergic sign scores (P &lt; 0.05). CONCLUSIONS: AC patients should be advised to routinely undergo corneal tomographic and biochemical measurements and the TBI could be used an indicator of KC devolopment risk in AC patients.

Anterior segment indices in mentally retarded children

To compare the anterior segment indices between mentally retarded and normal children. The current study was conducted as a cohort. In this study, 73 mentally retarded and 76 normal children were selected from normal school and special schools for mentally retarded children using random cluster sampling method. Mental retardation in children was confirmed by a psychologist. Optometry examinations including visual acuity and refraction were performed for all participants, and ultimately, corneal imaging measurements were taken by Pentacam. The mean age of mentally retarded and normal children was of 13.30 ± 1.83 and 13.05 ± 1.82 years, respectively (P = 0.180). A multiple generalized estimating equations model demonstrated that there is a significant association between central corneal thickness (CCT) (coef = 1.011, P < 0.001), corneal diameter (CD) (coef = 0.444, P = 0.046), anterior chamber depth (ACD) (coef = 0.23), P < 0.001) and index of vertical asymmetry (IVA) (coef = 0.12, P < 0.001) and mental retardation. Cerebral palsy children had higher keratoconus index (KI), central keratoconus index (CKI), index of height asymmetry(IHA), and index of height decentration (IHD) compared to those without cerebral palsy (P < 0.05). Children with moderate mental retardation had higher index of surface variance (ISV), IVA, IHA, and IHD than those with mild mental retardation (P < 0.05). The mean and standard deviation of CCT, CD, ACD and IVA index in mentally retarded children were 535.3 ± 46.68 micron, 11.87 ± 0.42 mm, 3.29 ± 0.24 mm and 0.25 ± 0.18 mm, respectively. These indices in the normal group were 525.53 ± 47.52 micron, 11.84 ± 0.38 mm, 3.15 ± 0.28 mm and 0.17 ± 0.05 mm, respectively. The findings of this study showed that some anterior segment indices were different in mentally retarded compared to normal children. Moreover, some keratoconus indicators were worse in cerebral palsy children and children with higher grade mental retardation. So, it is important to consider keratoconus screening in these children.

Corneal topometric indices and proclivity toward corneal ectasia in vernal keratoconjunctivitis

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). 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. 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). 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.

Corneal characteristics in patients with retinitis pigmentosa

BackgroundTo evaluate corneal topography and specular microscopic findings in patients with retinitis pigmentosa. MethodsOne hundred and two eyes of 51 patients with retinitis pigmentosa and 60 eyes of 30 healty subjects were included in our study. A detailed ophthalmological examination involving best corrected visual acuity (BCVA) was performed. A rotating Scheimpflug imaging system, was used to evaluate all eyes for topographic and aberrometrics parameters. Specular microscopy measurements were also noted. ResultsThe retinitis pigmentosa group consisted of 51 patients (29 male and 22 female, mean age of 35.61±13.55 (18–65) years and the control group also consisted of 30 healty subjects (29 male and 22 female, mean age of 33.67±9.92 (20–58) years. There was no difference between the groups in terms of age (p = 0.624) and gender (p = 0.375). Spherical equivalents were higher in the RP group (p<0.001). Central keratoconus index (CKI) (p<0.001), Belin Ambrosio enhanced ectasia display total deviation value (BAD-D) (p = 0.003), index of surface variance (ISV) (p<0.001), index of vertical asymmetry (IVA) (p<0.001), Ambrosio related thickness (ART max) (p = 0.018), index of height asymmetry (IHA) (p = 0.009), index of height decentration (IHD) (p<0.001), maximum anterior elevation (p<0.001), front elevation in thin location (p = 0.05), progression index average (p = 0.015), root mean square (RMS) total (p = 0.010) and RMS-higher order aberration (RMS-HOA) (p<0.001) values were higher in RP group. There was a weak negative correlation between BCVA and ART max measurements (r=-0.256, p = 0.009) in RP group. We detected keratoconus-suspect in 6 eyes and clinically manifest keratoconus in one eye in the RP group. ConclusionsPatients with retinitis pigmentosa may have corneal morphological disorders that may affect vision. In our study, corneal topographic pathologies including keratoconus and possible keratoconus were detected in RP patients.

The Characteristics of Quick Contrast Sensitivity Function in Keratoconus and Its Correlation with Corneal Topography.

To characterize quick contrast sensitivity function (qCSF) in keratoconus and its correlation with corneal topographic parameters. Patients with keratoconus (n = 120) who visited the Fudan Eye and ENT Hospital between April and June 2021 were enrolled in our study. A total of 215 eyes were subdivided into three groups according to maximum keratometry (Kmax): Group1 (Kmax ≤ 48D, 74 eyes), Group2 (48D < Kmax ≤ 55D, 64 eyes), and Group3 (Kmax > 55D, 77 eyes). Manifest refraction, best corrected distance visual acuity (BCVA), corneal topography, and the qCSF test were examined. Intergroup comparisons and correlations among various corneal topographic parameters and qCSF were analyzed. Significant differences in the area under the logCSF (AULCSF) and CSF Acuity among the three groups were found, which decreased with an increase in Kmax. Contrast sensitivity (CS) between spatial frequencies of 3.0 to 18.0cpd was significantly different (all P < 0.05) between Groups1 and 2. The CS at all spatial frequencies was significantly different (all P < 0.05) between Group3 and other two groups. At 3.0-18.0cpd, CS decreased significantly (all P < 0.05) in Groups1-3. Manifest refraction and topographic indices correlated significantly with qCSF parameters (all P < 0.05). Multivariable linear regression analysis showed that cylindrical refraction, logMAR BCVA, and index of surface variance had good predictive values for AULCSF and CSF Acuity. The use of qCSF test can serve as a feasible tool to evaluate visual quality and severity of keratoconus, since changes in CS significantly correlated with keratoconus severity.

Efficacy and safety of accelerated corneal collagen cross-linking in patients with keratoconus

AIM: To study the efficacy and safety of accelerated collagen cross-linking in keratoconus. METHODS: Medical records of keratoconic corneas underwent accelerated collagen cross-linking at King Chulalongkorn Memorial Hospital, Thailand between April 2015 and August 2018 were reviewed. Preoperative and postoperative data at 1y of visual acuity, auto-refraction, corneal topography, higher-order aberrations (HOA), topometric indices and corneal densitometry were evaluated. Age of 24-30 (mean age 23.43±7.26)y, maximum keratometric value (Kmax) of 55 D, and baseline best corrected visual acuity (BCVA) of 20/40 (or 0.3 in LogMAR unit) were used as cut-off values to highlight the cross-linking effects. The effect of age, preoperative Kmax and BCVA were analyzed. The association between the change of corneal densitometry and other factors including preoperative Kmax, Kmean, manifest refraction spherical equivalent (MRSE), visual acuity, thinnest pachymetry, the change in Kmax, and the change of those parameters were also analyzed. P&lt;0.05 was considered statistically significant. RESULTS: One hundred and fifty-five patients (185 eyes) were included. Male to female ratio was 3:31. According to Amsler-Krumeich classification, stage 1 and 2 were dominant (37.84% and 35.14% respectively). At 1y, mean LogMAR uncorrected visual acuity (UCVA) improved by 0.1 (P&lt;0.05). The number of eyes of which postoperative BCVA improved more than 0.2 LogMAR was higher in the worse baseline BCVA group (preoperative BCVA ≥0.3) compared to the better baseline BCVA group (preoperative BCVA &lt;0.3) (78.26% vs 21.74%, P&lt;0.05). Mean Kmax decreased from baseline by 2.36 diopters (D) (P&lt;0.05). Seventy-three percent of the eyes of which Kmax reduced more than 2.0 D had preoperative Kmax ≥55 D. Q-value showed less prolate by 0.06 (P&lt;0.05). Corneal HOA at 6 mm from corneal apex decreased by 0.40 (P&lt;0.05). Corneal densitometry at 0-6 mm zone increased at 1mo and persisted 1y postoperatively (P&lt;0.05). The relationship of the increase in densitometric value and the decrease of thinnest pachymetry at 1y were in linear fashion. Index of surface variance, index of vertical asymmetry, keratoconus index, index of height decentration decreased at 1y (P&lt;0.05). Success rate at 1y was 90.24%. Postoperative corneal haze was found 11.35%, 30.27%, 15.67%, 10.27% and 2.16% at 1wk, 1, 3, 6mo and 1y respectively. No eyes developed corneal edema. There was one case of sterile keratitis. CONCLUSION: Accelerated collagen cross-linking in keratoconus was effective to flatten, reshape the cornea, improved visual acuity, HOA and topometric indices. Great Kmax reduction was found in advanced keratoconus. The magnitude of Kmax reduction is also greatest among previous reports.

The false positive rates for detecting keratoconus and potential ectatic corneal conditions when evaluating astigmatic eyes with Scheimpflug Technology.

To quantify the false positive rates for keratoconus (KC) and potential ectatic corneal conditions in highly astigmatism eyes when using published parameters/indices obtained from the Pentacam and Galilei units. Oftalmosalud Instituto de Ojos, Lima, Peru. Prospective cohort study. 67 consecutive eyes with corneal astigmatism > 1.5 D, with a minimum follow ups of 36 months after an uneventful LASIK procedure were included. Indices for KC and other potential ectatic corneal conditions (subclinical KC, forme fruste KC, suspect KC) were obtained using the Pentacam and Galilei Scheimpflug cameras. The false positive rates for KC and potential ectatic corneal conditions were measured. Cut off values provided by previous studies and company-based parameters were used to assess the rate of false positivity. The range of false positive rates for a KC diagnosis depending on the lowest and highest cutoff values were: index of height decentration (61% - 1%), index of surface variance (76% - 0%), Posterior elevation (55% - 0%), maximum Ambrosio Relational thickness (100% - 13%), Belin Ambrosio enhanced ectasia display total deviation value (100% - 4%), Average pachymetric progression index (69% - 3%), Pachymetry at the thinnest point (58% - 1%), CSI Center Surround Index (100%), Differential sector index (51%). The false positive rates for KC and ectatic corneal conditions vary dramatically depending on the cut-off values used. Some indexes used for diagnosis of potential ectatic corneal conditions are inaccurate in normal, highly astigmatic eyes.

Changes in corneal topography asymmetry indices after corneal collagen cross-linking in keratoconus

Purpose The aim of this study was to evaluate the changes in corneal topography asymmetry indices after corneal collagen cross-linking (CXL) in patients with keratoconus and to analyze their correlation with visual acuity changes and preoperative average keratometric (K) value.Setting and design This is a prospective interventional noncomparative nonrandomized study that was conducted at the Outpatient Clinic of the Ophthalmology Department of Tanta University Hospital.Patients and methods CXL was conducted in 30 eyes of 15 patients with keratoconus. Quantitative descriptors of corneal topography were measured with corneal tomography using a rotating Scheimpflug camera (Pentacam-Oculus). They included seven indices: index of surface variance (ISV), center of keratoconus index (CKI), index of height asymmetry (IHA), index of vertical asymmetry (IVA), keratoconus index (KI), index of height decentration (IHD), and minimum radius of curvature (Rmin). Follow-up of cases was done for 6 months.Results There was a statistically significant improvement in ISV (P<0.001), IVA (P<0.001), KI (P<0.001), CKI (P=0.007), IHD (P<0.001), and Rmin (P=0.001). However, there was no statistically significant difference in IHA (P=0.082). The improvement in postoperative indices was not correlated with the changes in corrected distance visual acuity. The preoperative average K value was statistically significantly positively correlated with the improvement in KI (r=0.589, P=0.001), ISV (r=0.495, P=0.005), preoperative IHD (r=0.422, P=0.020), and preoperative CKI (r=0.663, P=0.001), with a statistically significant negative correlation with the preoperative Rmin (r=−0,916, P>0.001). However, the preoperative average K value was not significantly correlated with the improvements in IHA (r=−0,078, P=0.681) and IVA (r=0.204, P=0.280).Conclusion There was a significant improvement in six of the seven topography indices 6 months after CXL. Improvement in these indices was not correlated with corrected distance visual acuity changes. The preoperative average K value was significantly correlated with the improvement in KI, ISV, preoperative IHD, preoperative CKI, and preoperative Rmin.

Corneal Asphericity and Higher-Order Aberrations after FS-LASIK and Trans-PRK for Myopia.

Objective To compare the corneal asphericity and higher-order aberrations (HOAs) of femtosecond laser-assisted in situ keratomileusis (FS-LASIK) with Smart Pulse Technology (SPT) assisted transepithelial photorefractive keratectomy (Trans-PRK) for myopia and myopic astigmatism correction. Methods This prospective study analyzed 88 eyes of 44 patients treated with FS-LASIK and 64 eyes of 32 patients treated with Trans-PRK. All eyes had low to moderate myopia with or without astigmatism (spherical equivalent (SE) <−6.00 diopters). The uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), SE, asphericity (Q value) of the anterior corneal surface, index of surface variance (ISV), corneal higher-order aberrations (HOAs), vertical coma (Z3−1), horizontal coma (Z31), and spherical aberration (Z40) over a 6 mm diameter central corneal zone diameter were evaluated preoperatively and 1, 3, and 6 months postoperatively. Results At 6 months, the UDVA and SE were −0.14 ± 0.06 and 0.33 ± 0.33D in FS-LASIK and −0.15 ± 0.06 and 0.35 ± 0.37D in Trans-PRK. There was no difference between the two groups in the postoperative UDVA and SE (P > 0.05). After FS-LASIK and Trans-PRK, the Q values in the 6, 7, 8, and 9 mm zones and ISV of the anterior corneal surface significantly increased (P < 0.001). At 1, 3, and 6 months after surgery, corneal HOA, Z3−1, Z31, and Z40 in both groups were significantly increased compared with those before surgery, with statistically significant differences (P < 0.001). At 1, 3, and 6 months after surgery, the Z3−1 of the Trans-PRK group was significantly lower than that of the FS-LASIK group (P < 0.001). ΔHOA and ΔZ40 were dramatically correlated with the ΔQ value for both FS-LASIK and Trans-PRK procedures. The ΔQ was significantly correlated with the preoperative SE, AD, and AD/CCT after both two procedures (all P < 0.001). Conclusions Both FS-LASIK and Trans-PRK caused the anterior corneal surface to become flatter, and the morphology of the corneal surface was irregular. Corneal HOAs were significantly increased after the two procedures. Trans-PRK using SPT introduced less corneal vertical coma than FS-LASIK. Corneal asphericity changes contributed to the corneal aberrations changes following FS-LASIK and Trans-PRK.

Best Indicators for Detecting Keratoconus Progression in Children: A Report From the Shahroud Schoolchildren Eye Cohort Study.

The purpose of this study was to investigate 3-year changes in keratoconus (KC) indices to determine the indicators of KC progression compared with age-related changes in children aged 6 to 12 years. In this report of the Shahroud Schoolchildren Eye Cohort Study, KC was diagnosed based on vision, refraction, tomography, and slitlamp examination findings. KC progression was defined as changes in refractive astigmatism or zonal maximum keratometry (Zonal Kmax-3 mm). Then, 3-year changes (Δ) in vision, refraction, and tomographic indices were compared between progressive KC and normal eyes. The best set of ∆parameters for distinguishing KC progression from age-related changes were determined using the area under curve (AUC). Eighteen KC eyes and 10,422 normal eyes were analyzed. All KC cases showed progression after 3 years. Δindices were statistically different between the 2 groups except corrected distance visual acuity, anterior radius of curvature, irregularity index, and KC percentage index. The best Δindices, in descending order of AUC value, were index of height decentration, Zonal Kmax-3 mm, refractive astigmatism, single point Kmax, and index of vertical asymmetry (all AUC > 0.9), followed by inferior-superior asymmetry, index of surface variance, minimum corneal thickness, index of height asymmetry, KC index, posterior radius of curvature, and Belin/Ambrósio total Deviation (AUC = 0.8-0.9). According to our findings, changes in index of height decentration, Zonal Kmax-3 mm, refractive astigmatism, single point Kmax, and index of vertical asymmetry are the best indices for detecting KC progression in children younger than 12 years.

Effect of upper eyelid blepharoplasty on corneal biomechanical, topographic and tomographic parameters 4\xa0weeks after surgery

PurposeTo investigate the effect of “skin-only” upper eyelid blepharoplasty on corneal biomechanics and central as well as peripheral topographic/tomographic parameters before and 4 weeks after surgery.MethodsIn a prospective study, the corneal hysteresis (CH) and corneal resistance factor (CRF) were evaluated before and after blepharoplasty. Corneal topographic (maximum simulated keratometry value, inferior-superior value, index of surface variance, index of vertical asymmetry, index of height asymmetry, index of height decentration) and tomographic parameters (corneal thickness, corneal astigmatism and mean 5-mm- and 7-mm-zone keratometry value) were measured by the Pentacam HR. Statistical analysis was performed using a linear mixed model considering correlated data of both eyes.ResultsThis study included 42 eyes of 35 patients (mean age: 64.5 years, range 52–82 years). Four weeks after surgery CH and CRF increased (9.4 ± 2.3 to 10.2 ± 2.2 mmHg and 9.7 ± 2.1 to 10.5 ± 2.2 mmHg) but did not reach statistical significance (P = 0.100 and P = 0.072). A significant increase in central maximum simulated keratometry value (Kmax) from 45.0 ± 2.3 to 45.4 ± 2.2 diopters (D) was observed (P = 0.004). Inferior-superior value (I-S) and index of surface variance (ISV) showed significant changes from 0.32 ± 0.98 to 0.10 ± 0.98 D (P = 0.02) and from 19.98 ± 9.84 to 22.93 ± 11.23 (P = 0.009), respectively. These alterations did not affect the subjective spherical equivalent (-0.09 ± 4.71 to -0.04 ± 4.51 D; P = 0.437) and the best-corrected distance visual acuity of patients (0.11 ± 0.14 to 0.15 ± 0.15 logMAR; P = 0.142). Age, gender and corneal thickness were not correlated with pre and postoperative differences of CH, CRF, corneal compensated IOP, Kmax, corneal astigmatism or I-S.ConclusionThe trend of increasing CH and CRF values might indicate a rise of corneal damping capacity. Despite statistically significant differences of Kmax, I-S and ISV, all other tomographical and topographical parameters did not change 4 weeks after surgery. The corneal steepening with a mean change of 0.4 diopters and the decrease of I-S with a mean of 0.22 diopters do not seem to have a clinically relevant effect for blepharoplasty patients in daily practice.

Benefits of using corneal topography to choose subjective refraction technique in keratoconus (RE-CON): a prospective comparative crossover clinical study.

In prospective no-masking, comparative, crossover monocenter clinical trial, we aimed to evaluate whether the optimal subjective refraction technique varies with the keratoconus topography and to identify relevant topographic criteria. This study included 72 keratoconus eyes with impaired visual acuity. Each eye tested three methods of refraction (Jackson cylinder, astigmatism dial, stenopeic slit), resulting in three eyeglass lenses. Patients were assigned to the group corresponding to the eyeglass lens offering the best visual acuity. Five topographical characteristics were collected via the Pentacam: mean keratometry (Km), maximum keratometry (Kmax), distance from corneal center to Kmax (dKmax), Belin/Ambrosio Display (BAD_D), and index of surface variance (ISV). Forty-six eyes were included in the dial group (64.8%), 23 eyes in the cylinder group (32.4%), and only 2 eyes in the slit group (2.8%); thus, we only compared dial and cylinder groups. The main analysis retrieved a significant probability to choose dial technic for BAD_D (p = 0.024); when BAD_D is > 9.71 (ROC threshold), the positive predictive value (PPV) = 89.5%, and for ISV, p = 0.012; when ISV is > 77, PPV = 89.1%. The sub-analysis of patients with different visual acuities between cylinder and dial confirmed these results with slightly different thresholds: the probability to choose dial technic was for BAD_D, p = 0.03; when BAD_D is > 7.55, PPV = 90%, and for ISV, p = 0.0084; when ISV is > 71, PPV = 88.5%. Refraction method is linked to topographic indices ISV and BAD_D. A BAD_D > 7.55 indicates the dial method. In addition to keratoconus screening and diagnosis, this study suggests a new application of the topographer to select a suitable refraction method for eyeglass prescription. Study registered on the ClinicalTrials.gov database under n°: NCT04174209.

Changes of corneal topography indices after corneal collagen crosslinking for treatment of keratoconus assessed by scheimpflug camera

Introduction Keratoconus is a bilateral, progressive ectasia of the cornea resulting in irregular astigmatism and myopia. We can use spectacles or contact lenses to correct the symptoms of keratoconus, whereas in advanced cases, corneal grafting is the only treatment. Corneal collagen cross-linking (CXL) is a promising treatment to strengthen and stabilize the cornea in cases of keratoconus. Aim To evaluate changes in corneal topography indices after corneal CXL in patients with keratoconus and analyze these changes. Patient and methods CXL was performed in eyes with keratoconus. Quantitative descriptors of corneal topography were measured with the Pentacam topographer and included seven indices: index of surface variance, index of vertical asymmetry, keratoconus index, central keratoconus index, minimum radius of curvature, index of height asymmetry, and index of height decentration. Follow-up was 6 months. Results The study comprised 50 eyes of 35 patients with keratoconus. In the entire patient cohort, there were significant improvements in the index of surface variance, index of vertical asymmetry, keratoconus index, and minimum radius of curvature at 6 months compared with baseline (all P Conclusion There were improvements in four of seven topography indices 6 months after CXL, suggesting an overall improvement in corneal shape.

Development of a classification system based on corneal biomechanical properties using artificial intelligence predicting keratoconus severity

BackgroundTo investigate machine-learning (ML) algorithms to differentiate corneal biomechanical properties between different topographical stages of keratoconus (KC) by dynamic Scheimpflug tonometry (CST, Corvis ST, Oculus, Wetzlar, Germany). In the following, ML models were used to predict the severity in a training and validation dataset.MethodsThree hundred and eighteen keratoconic and one hundred sixteen healthy eyes were included in this monocentric and cross-sectional pilot study. Dynamic corneal response (DCR) and corneal thickness related (pachymetric) parameters from CST were chosen by appropriated selection techniques to develop a ML algorithm. The stage of KC was determined by the topographical keratoconus classification system (TKC, Pentacam, Oculus). Patients who were classified as TKC 1, TKC 2 and TKC 3 were assigned to subgroup mild, moderate, and advanced KC. If patients were classified as TKC 1–2, TKC 2–3 or TKC 3–4, they were assigned to subgroups according to the normative range of further corneal indices (index of surface variance, keratoconus index and minimum radius). Patients classified as TKC 4 were not included in this study due to the limited amount of cases. Linear discriminant analysis (LDA) and random forest (RF) algorithms were used to develop the classification models. Data were divided into training (70% of cases) and validation (30% of cases) datasets.ResultsLDA model predicted healthy, mild, moderate, and advanced KC eyes with a sensitivity (Sn)/specificity (Sp) of 82%/97%, 73%/81%, 62%/83% and 68%/95% from a validation dataset, respectively. For the RF model, a Sn/Sp of 91%/94%, 80%/90%, 63%/87%, 72%/95% could be reached for predicting healthy, mild, moderate, and advanced KC eyes, respectively. The overall accuracy of LDA and RF was 71% and 78%, respectively. The accuracy for KC detection including all subgroups of KC severity was 93% in both models.ConclusionThe RF model showed good accuracy in predicting healthy eyes and various stages of KC. The accuracy was superior with respect to the LDA model. The clinical importance of the models is that the standalone dynamic Scheimpflug tonometry is able to predict the severity of KC without having the keratometric data.Trial registrationNCT04251143 at Clinicaltrials.gov, registered at 12 March 2018 (Retrospectively registered).