Repeatability and agreement of two swept-source optical coherence tomographers and scheimpflug imaging for measurements of corneal curvature.

PURPOSE: To evaluate the repeatability and agreement of two swept-source optical coherence tomographers and Scheimpflug imaging for corneal curvature in healthy subjects to obtain data on the clinical application of a new device. METHODS: This prospective study was conducted in January and February 2021 with 100 healthy subjects at the Eye Hospital of Wenzhou Medical University. Simulated keratometry (Sim-K), posterior keratometry (Kp), total corneal power (TCP), and total corneal astigmatism (TCA) were measured with CASIA2, Anterion, and Pentacam. Within-subject standard deviation (Sw), repeatability coefficient (RC), coefficient of variation (CoV), and intraclass correlation coefficient (ICC) were used to assess inter-device repeatability. Bland-Altman analysis was performed to determine inter-device agreement. RESULTS: The three devices showed good repeatability for Sim-K, Kp, and TCP with all ICC > 0.980. Pentacam showed the highest repeatability (ICC ≥ 0.993; ICC ≥ 0.993) while the CASIA2 demonstrated the lowest repeatability (ICC: ≥ 0.986; ICC: ≥ 0.985) for Sim-K and TCP. Anterion and CASIA2 revealed better repeatability (ICC ≥ 0.998; ICC ≥ 0.981) for Kp than Pentacam (ICC ≥ 0.980). Pentacam and Anterion showed good repeatability for TCA (ICC: 0.935 and 0.916), whereas the CASIA2 showed moderate repeatability (ICC: 0.836). Three instruments demonstrated good agreement with the maximum absolute 95% Limits of agreement (LoA) of 1.00 D for Sim-K, Kp, and TCP. Wide LoA were found for TCA with the maximum absolute 95% LoA ≥ 0.66 D between the three devices. CONCLUSIONS: In healthy subjects, the three devices (Pentacam, Anterion and CASIA2) displayed comparable repeatability and accuracy for SimK, Kp, and TCP, and could be used interchangeably for these parameters. However, TCA measured by the three devices was not interchangeable. TRIAL REGISTRATION: Chinese Clinical Trial Registry Center (10/10/2020, ChiCTR2000038959).

Incision-related astigmatism on the anterior and total cornea after implantable collamer lens implantation.

PURPOSE: To evaluate incision-related astigmatism (IRA) on the anterior and total cornea after implantable collamer lens (ICL) implantation through superior and temporal corneal incisions. METHODS: The retrospective study included 141 eyes of 80 consecutive patients who underwent ICL implantation. An ocular examination was performed preoperatively and at 1 and 6 months postoperatively. The magnitude and axis of corneal astigmatism were assessed with keratometry (AstigK) and total corneal refractive power (TCRP, AstigTCRP) using a Scheimpflug camera, while the IRA obtained from keratometry (IRAK) and TCRP (IRATCRP) were evaluated using vector analysis. RESULTS: At 6 months, AstigK significantly decreased from 1.45 ± 0.72 D to 1.15 ± 0.75 D in the superior incision group, whereas it increased from 1.70 ± 0.74 D to 1.88 ± 0.79 D in the temporal incision group (both P < 0.001). AstigTCRP significantly decreased from 1.32 ± 0.74 D to 1.09 ± 0.80 D in the superior incision group, while it increased from 1.61 ± 0.78 D to 1.83 ± 0.86 D in the temporal incision group (both P < 0.001). IRAK was 0.55 ± 0.30 D and 0.35 ± 0.25 D in the superior and temporal incision groups, respectively, while IRATCRP was 0.50 ± 0.28 D and 0.40 ± 0.26 D in the superior and temporal incision groups, respectively. IRAK was larger in the superior incision group than in the temporal incision group for both low- (P = 0.009) and high-astigmatism (P = 0.017). CONCLUSIONS: Incisions in ICL surgery cause corneal flattening in the meridian of the incision. The superior incision had a greater IRAK compared to the temporal incision.

[On the issue of diagnostic accuracy of methods for analyzing the parameters of regular astigmatism]. / K voprosu o diagnosticheskoi tochnosti metodov indikatsii pokazatelei regulyarnogo astigmatizma.

Accurate measurement of astigmatism parameters is the basis for prescribing modern means of optical correction. In recent years, another direction for correcting astigmatism has emerged - implantation of toric intraocular lenses (TIOL). PURPOSE: This study evaluates the diagnostic accuracy of various methods for measuring the parameters of regular astigmatism. MATERIAL AND METHODS: The study included 83 patients (122 eyes) with regular astigmatism exceeding 1.0 D. Three groups were formed depending on the type of astigmatism. Spherical and cylindrical (power and axis) components of refraction were determined using automatic refractometry. The results were refined with subjective tests: power and axis tests with a cross-cylinder. The criterion for diagnostic accuracy was the level of corrected visual acuity. To assess the impact of cylinder position on visual acuity, discrete deviations of the axis of trial astigmatic lenses from the correct position (determined based on subjective tests) were modeled at 5, 10, and 15 degrees in both clockwise and counterclockwise directions. RESULTS: In the overall sample of observations, coincidence of results was found only in one-third of cases, with a tendency for discrepancies in data between the two methods in nearly 70% of cases. Statistical processing revealed significant differences only in the magnitude of the cylinder in the group with against-the-rule astigmatism (p<0.0005). An increase in maximum visual acuity corrected based on subjective test data was noted. With a deviation of the cylinder axis from the correct position by 10-15 degrees, regardless of the type of astigmatism, a significant tendency for a decrease in visual acuity was identified. At the same time, with a deviation of the cylinder axis within 5 degrees, a significant decrease in visual acuity was noted only in with-the-rule astigmatism and counterclockwise deviation. CONCLUSION: To achieve maximum visual acuity in the correction of regular astigmatism, objective method data must be refined with subjective tests. The results of modeling the deviation of the axis of the corrective lens from the proper position can be considered when evaluating the functional outcomes of TIOL implantation.

A short-term comparison of surgical results between an ab-externo microshunt and trabeculectomy with a main focus on postoperative corneal astigmatism.

PURPOSE: To compare surgical results between ab-externo microshunt surgery and trabeculectomy, focusing on postoperative corneal astigmatism. STUDY DESIGN: Retrospective study. METHODS: Subjects were patients with glaucoma who underwent either standalone ab-externo microshunt surgery or trabeculectomy. Data on ophthalmic examinations obtained preoperatively and 1, 3, and 5 months postoperatively were analyzed. To assess corneal astigmatism, two separate data sets measured by anterior segment optical coherence tomography and autorefractometer were evaluated. Multivariate linear mixed model analyses were conducted to identify factors associated with the astigmatism changes. RESULTS: Sixty eyes were examined: 13 eyes underwent microshunt surgery, and 47 eyes underwent trabeculectomy. The total corneal astigmatism measurements by anterior segment optical coherence tomography (AS-OCT) were: - 1.15 ± 0.85 D and - 1.17 ± 0.81 D for the microshunt and trabeculectomy groups, respectively, preoperatively. At five months postoperatively they were - 0.92 ± 0.47 D and - 1.61 ± 0.83 D, respectively (P = 0.807 for the microshunt group and P = 0.005 for the trabeculectomy group: Wilcoxon signed-rank test). AS-OCT also indicated similar results for posterior corneal astigmatism. Autorefractometry also found the total corneal astigmatism was significantly changed only in the trabeculectomy group. The linear mixed model analysis revealed that trabeculectomy (P = 0.001), older age (P = 0.004), and longer postoperative period (P = 0.015) were correlated with greater astigmatism changes. The intraocular pressures significantly decreased following both surgical treatments. CONCLUSIONS: Standalone ab-externo microshunt surgery has less effect on corneal astigmatism during a 5 month period than trabeculectomy. Both surgical procedures significantly reduced intraocular pressure.

Non-penetrating filtration surgery versus trabeculectomy in postoperative astigmatism: a meta-analysis.

OBJECTIVE: Trabeculectomy and non-penetrating trabecular surgery are common operations for glaucoma. This meta-analysis aims to compare the effect of trabeculectomy and non-penetrating trabecular surgery in postoperative astigmatism of patients with glaucoma. METHODS: A systematic literature search was performed for studies comparing trabeculectomy and non-penetrating trabecular surgery in patients with glaucoma. The time frame for the search was from the time of construction to April 2024. There were no restrictions regarding study type or type of glaucoma. The endpoint was the surgically induced astigmatism assessed 6 months after operation. We conducted this meta-analysis following the PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis). RESULTS: Five eligible studies were included in this meta-analysis and presented data for 359 eyes with various types of glaucoma at different stages. The results revealed an increase in astigmatism in patients with glaucoma after trabeculectomy and non-penetrating trabecular surgery. Trabeculectomy had a higher incidence of astigmatism than in the non-penetrating trabecular surgery group at or around 6 months postoperatively, and the difference was statistically significant. (SMD = 0.40, 95% CI = 0.19 to 0.61, P = 0.02). CONCLUSION: Our results demonstrated that both trabeculectomy and non-penetrating trabecular surgery could increase astigmatism until 6 months after operation. Moreover, non-penetrating trabecular surgery group seems to have less influence on astigmatism. TRIAL REGISTRATION NUMBER: CRD42024517708.

Comparative analysis of surgically induced astigmatism following cataract surgery: influence of previous myopic correction and corneal parameters.

PURPOSE: This retrospective study investigated the impact of corneal parameters on surgically induced astigmatism (SIA) in eyes with prior myopic correction undergoing cataract surgery. SETTING: Department of Ophthalmology, San Marino Hospital, San Marino, Republic of San Marino. DESIGN: This case-control study analyzed existing data retrospectively, without randomization or masking. METHODS: Eighty eyes divided in group 1 (40 eyes previous underwent refractive surgery for myopia) and group 2 ( 40 myopic eyes) that underwent cataract surgery with intraocular lens (IOL) implantation were included. SIA was calculated using values from the IOL Master Zeiss 700 and mean pupil power (MPP) derived from the CSO Sirius Topographer (based on 3 mm pupil size) with vectorial analysis from doctor Hill software. RESULTS: No significant difference in SIA was observed between eyes with prior myopic photorefractive keratectomy and the control group (p > 0.05). SIA calculations using the IOL Master and CSO Sirius Tomographer yielded similar results. There was no significant correlation between SIA and axial length, corneal curvature, peripheral corneal thickness, or anterior chamber depth (p > 0.05). However, an inverse correlation was found between SIA and horizontal corneal diameter (p < 0.05). CONCLUSIONS: Corneal parameters, such as axial length, corneal curvature, peripheral corneal thickness, and anterior chamber depth, showed no significant influence on SIA. The inverse correlation between SIA and horizontal corneal diameter in study group suggests potential influence of white-to-white distance on SIA. These findings highlight the importance of considering corneal parameters for optimizing surgical outcomes.

A new, adaptive, self-administered, and generalizable method used to measure visual acuity.

SIGNIFICANCE: Angular Indication Measurement (AIM) is an adaptive, self-administered, and generalizable orientation-judgment method designed to interrogate visual functions. We introduce AIM Visual Acuity (VA) and show its features and outcome measures. Angular Indication Measurement VA's ability to detect defocus was comparable with that of an Early Treatment of Diabetic Retinopathy Study (ETDRS) letter chart and showed greater sensitivity to astigmatic blur. PURPOSE: This proof-of-concept study introduces Angular Indication Measurement and applies it to VA. METHODS: First, we compared the ability of AIM-VA and ETDRS to detect defocus and astigmatic blur in 22 normally sighted adults. Spherical and cylindrical lenses in the dominant eye induced blur. Second, we compared repeatability over two tests of AIM-VA and ETDRS. RESULTS: A repeated-measure analysis of variance showed a main effect for defocus blur and test. For the astigmatism experiment, an interaction between blur and orientation was found. Pairwise comparisons showed that AIM was more sensitive to astigmatic-induced VA loss than ETDRS. Bland-Altman plots showed small bias and no systematic learning effect for either test type and improved repeatability with more than two adaptive steps for AIM-VA. CONCLUSIONS: Angular Indication Measurement VA's ability to detect defocus was comparable with that of an ETDRS letter chart and showed greater sensitivity to induced astigmatic blur, and AIM-VA's repeatability is comparable with ETDRS when using two or more adaptive steps. Angular Indication Measurement's self-administered orientation judgment approach is generalizable to interrogate other visual functions, e.g., contrast, color, motion, and stereovision.

Refractive errors in patients with Bardet Biedl syndrome.

PURPOSE: Bardet-Biedl Syndrome (BBS) is a rare autosomal recessive ciliopathy. Within corneal development, primary cilia serve a critical role. We sought to investigate the association of BBS with corneal astigmatism among a cohort of patients with BBS. METHODS: This was a cross-sectional, retrospective study performed at a pediatric ophthalmology department of a tertiary hospital. The study enrolled 45 patients with genetically confirmed Bardet-Biedl syndrome, encompassing a total of 90 eyes observed from February 2011 to August 2021. Spherical and cylindrical refractive errors and keratometry outcome measures, including diopter (D) values at the flattest and steepest axes, were recorded. Corneal astigmatism of greater than 3D is considered extreme corneal astigmatism based on previously published data. RESULTS: Among 45 patients (M:26; F:19), the mean age was 16.4 ± 8.2 years, and the mean best-corrected visual acuity was 20/60. The most common molecular diagnosis was BBS1, seen in 24 of 45 (53.3%). Among all the patients, the mean spherical refractive error was -2.9 ± 3.8D. The mean cylindrical refractive error was 2.6 ± 1.5D. The mean keratometry values at the flattest axis was 43.5 ± 5.3D (39.4-75.0) and at the steepest axis was 47.2 ± 7.3D(41.5-84.0). Among all the patients with BBS, the mean corneal astigmatism was 3.7 ± 1.0D(0.5-7.1), which is considered extreme. CONCLUSION: A cohort of individuals with BBS demonstrated high corneal astigmatism. These results suggest an association between corneal astigmatism and primary ciliary dysfunction and may assist in clinical management and future therapeutic targets among BBS and other corneal disorders.

Diagnosis of forme fruste keratoconus with scheimpflug photography in Ghanaian patients.

AIM: This 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. METHODS: We 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. RESULTS: Statistically 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%). CONCLUSION: The 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.

Comparative Accuracy of Barrett Integrated Keratometry Toric Calculator With Predicted Versus Measured Posterior Corneal Astigmatism.

PURPOSE: To compare the prediction accuracy of the Barrett toric calculator using standard or integrated keratometry (IK) mode in combination with predicted or measured posterior corneal astigmatism (PCA) in a group of patients with cataract implanted with non-toric IOLs. METHODS: In this retrospective clinical cohort study, the medical records of patients with age-related cataract who underwent phacoemulsification with the implantation of an aspheric monofocal IOL were reviewed. Four methods, including standard keratometry with predicted PCA (PPCA), IK combined with predicted PCA (IK-PPCA), and IK combined with measured PCA derived from IOLMaster 700 (Carl Zeiss Meditec AG) or CASIA2 (Tomey) (IK-MMPCA or IK-CMPCA), were applied to the Barrett toric calculator to calculate the predicted residual astigmatism. The mean absolute prediction error (MAPE), centroid of the prediction error, and proportion of eyes within the prediction error of ±0.50, ±0.75, and ±1.00 diopters (D) were all ciphered out from the four methods, respectively. RESULTS: Data from 129 eyes of 129 patients were included in this study. The MAPE of the IK-PPCA method (0.57 ± 0.36 D) was significantly smaller than that of the PPCA (0.62 ± 0.38 D) and IK-CMPCA (0.63 ± 0.46 D) methods (P = .048 and .014, respectively). There were no significant differences in the centroid vectors of prediction errors and predictability rates among the four methods (all P > .05). CONCLUSIONS: In the current version of the Barrett toric calculator, the predictive accuracy of the IK mode incorporating PPCA was slightly superior to using the standard keratometry mode or incorporating MPCA. [J Refract Surg. 2024;40(7):e453-e459.].

Effect of congenital ptosis on corneal topography and total aberrometry and comparison of these variables between ptotic and normal fellow eyes.

PURPOSE: To analyze the effect of congenital ptosis on corneal topography and total aberrometry and to compare these variables between ptotic and normal fellow eyes. METHODS: The study included 32 eyes of 16 patients with unilateral congenital blepharoptosis. A Shack-Hartmann wavefront sensor was employed to assess Zernike coefficients and root-mean-square. Computerized corneal topography, Orbscan and aberrometry were measured in the healthy and ptotic eyes. Data were analyzed using SPSS version 16. P<0.05 was considered significant. RESULTS: The mean patient age was 21.31±6.3 years. The mean margin to light reflex distance-1 (MRD-1) was 0.6±1.44mm in the ptotic eyes. Among topography variables, surface regularity index (SRI), cylinder power, irregular astigmatism index (IAI), and flat meridian keratometry were significantly different between ptotic and non-ptotic fellow eyes (P<0.05). Some Orbscan parameters, including simulated keratometry, maximum and minimum corneal power, and astigmatism power were significantly different between ptotic and normal fellow eyes (P<0.05). There was no statistically significant difference in total aberrometry variables between paired eyes. However, in a comparison between ptotic eyes with over 1 diopter astigmatism vs. less than 1 D, high-order Zernike modes without spherical aberration at 6mm (HOW/O Z400 6mm) were significantly different between the 2 groups (P=0.02). CONCLUSION: Unilateral congenital ptosis significantly affects corneal topography and aberrometry, especially in eyes with astigmatism≥1 D. Such differences need to be considered before keratorefractive surgery (KRS).

Accuracy of Toric Intraocular Lens Formulas With Measured Posterior Corneal Astigmatism of Different Orientations.

PURPOSE: To assess whether the use of measured posterior corneal astigmatism (PCA) values improves the prediction accuracy of toric intraocular lens power formulas, compared to predicted PCA values, when the orientation of the steep axis of PCA is non-vertical. DESIGN: Retrospective observational cohort study. METHODS: Four hundred eighteen eyes of 344 patients were included in the study. Prediction errors (PE) for postoperative refractive astigmatism at 4 weeks postoperatively were determined using vector analysis and compared for the following toric intraocular lens power formulas: Barrett Toric with predicted posterior corneal astigmatism (PPCA); Barrett Toric with measured posterior corneal astigmatism (MPCA); EVO Toric PPCA; EVO Toric MPCA; Holladay I with Abulafia-Koch regression. Subgroup analysis compared PEs for eyes with a vertically orientated steep axis of PCA (60-120°) to eyes with a non-vertically orientated steep axis of PCA. SETTING: Cathedral Eye Clinic, Belfast, United Kingdom and Tan Tock Seng Hospital, Singapore. RESULTS: Standard keratometry was with-the-rule in 48% of eyes, while the steep PCA axis was vertically orientated in 91% of eyes. For all eyes, EVO-PPCA had a smaller mean absolute error than Barrett-MPCA, Barrett-PPCA, and Abulafia-Koch (P < .01 for all). EVO-PPCA had the highest percentage of eyes within 0.50D of predicted postoperative astigmatism for eyes with vertical PCA (61%), while EVO-MPCA had the highest percentage for eyes with non-vertical PCA (54%). EVO-MPCA had the smallest centroid error for all eyes, and the subgroups (P < .01 for all). Eyes with non-vertical PCA had a lower percentage within 0.50D than eyes with vertical PCA when using PPCA (43% vs 61%, P = .034), but there was no significant difference between these groups when MPCA is used for eyes with non-vertical PCA (54% vs 61%, P = .40). CONCLUSIONS: When the steep axis of posterior corneal astigmatism is not vertically orientated, the use of measured posterior keratometry values improves prediction accuracy.

Evaluating keratometry and corneal astigmatism data from biometers and anterior segment tomographers and mapping to reconstructed corneal astigmatism.

BACKGROUND: To compare results from different corneal astigmatism measurement instruments; to reconstruct corneal astigmatism from the postimplantation spectacle refraction and toric intraocular lens (IOL) power; and to derive models for mapping measured corneal astigmatism to reconstructed corneal astigmatism. METHODS: Retrospective single centre study involving 150 eyes treated with a toric IOL (Alcon SN6AT, DFT or TFNT). Measurements included IOLMaster 700 keratometry (IOLMK) and total keratometry (IOLMTK), Pentacam keratometry (PK) and total corneal refractive power in 3 and 4 mm zones (PTCRP3 and PTCRP4), and Aladdin keratometry (AK). Regression-based models mapping the measured C0 and C45 components (Alpin's method) to reconstructed corneal astigmatism were derived. RESULTS: Mean C0 components were 0.50/0.59/0.51 dioptres (D) for IOLMK/PK/AK; 0.2/0.26/0.31 D for IOLMTK/PTCRP3/PTCRP4; and 0.26 D for reconstructed corneal astigmatism. All corresponding C45 components ranged around 0. The prediction models had main diagonal elements lower than 1 with some crosstalk between C0 and C45 (nonzero off-diagonal elements). Root-mean-squared residuals were 0.44/0.45/0.48/0.51/0.50/0.47 D for IOLMK/IOLMTK/PK/PTCRP3/PTCRP4/AK. CONCLUSIONS: Results from the different modalities are not consistent. On average IOLMTK/PTCRP3/PTCRP4 match reconstructed corneal astigmatism, whereas IOLMK/PK/AK show systematic C0 offsets of around 0.25 D. IOLMTK/PTCRP3/PTCRP4. Prediction models can reduce but not fully eliminate residual astigmatism after toric IOL implantation.

Repeatability and Agreement of 4 Biometers Measuring Corneal Astigmatism in Eyes With Irregular Corneal Astigmatism Component.

PURPOSE: To investigate the repeatability and agreement of corneal astigmatism measurements in eyes with irregular corneal astigmatism component (ICAC) using four devices: IOLMaster 700 biometer, Lenstar 900 biometer, iTrace, and Pentacam. DESIGN: Prospective cross-sectional reliability analysis. METHODS: Sixty-four eyes (52 patients) with ICAC were examined three times using the four devices. The eye with ICAC in this study is defined as the cornea has a certain degree of irregular astigmatism (asymmetric and/or skewed bowtie pattern of corneal topography according to corneal topography classification), accompanied with total corneal higher-order aberrations in the 4 mm zone of 0.3 µm or greater. Corneal astigmatism was evaluated using three categories: anterior corneal astigmatism (ACA), posterior corneal astigmatism, and total corneal astigmatism (TCA). The repeatability was determined using the ∆Ast (arithmetic mean of vector differences among three repeated corneal astigmatism measurements). Bland-Altman plots and astigmatism vector analyses were employed to assess agreement. RESULTS: The IOLMaster 700 (∆Ast = 0.27 ± 0.20 D) showcased higher repeatability in ACA measurements compared to iTrace (∆Ast = 0.37 ± 0.38 D, P = .040) and Pentacam (∆Ast = 0.50 ± 0.22 D, P < .001), and paralleled the performance of Lenstar 900 (∆Ast = 0.31 ± 0.26 D, P = .338). The Pentacam (∆Ast = 0.09 ± 0.07 D, P < .001) demonstrated superior repeatability in posterior corneal astigmatism, whereas the IOLMaster 700 (∆Ast = 0.33 ± 0.23 D, P < .001) excelled in TCA. The IOLMaster 700 exhibited good agreement with either Lenstar 900 or iTrace, characterized by narrow 95% limits of agreement and clinically acceptable vector differences. Conversely, vector differences between Pentacam and the other three devices in ACA and TCA measurements were clinically significant, exceeding 0.50 D (all P < .05). CONCLUSIONS: In terms of repeatability of corneal astigmatism measurements in eyes with ICAC, the IOLMaster 700 and Lenstar 900 outperformed iTrace and Pentacam. While the IOLMaster 700 can be used interchangeably with either Lenstar 900 or iTrace, the Pentacam is not interchangeable with the other three devices.

Timing optimization for primary pterygium excision with conjunctival-limbal autograft to restore the corneal optical properties.

PURPOSE: To propose the optimal value of baseline corneal astigmatism and pterygial morphological profiles for primary pterygium surgery to restore the corneal optical properties. METHODS: We analysed 93 eyes from 84 subjects with nasal-only primary pterygium who underwent pterygium excision with conjunctival-limbal autograft and were assessed perioperatively using anterior segment swept-source optical coherence tomography (AS SS-OCT). We collected data on anterior corneal astigmatism (ACA) and root mean square (RMS) values for anterior corneal lower- (LoA) and higher-order aberrations (HoA) as corneal optical properties using AS SS-OCT. Using preoperative ACA and four pterygial morphological profiles (horizontal invasion length [HIL], height, thickness and the ratio of residual corneal thickness [RCT] to central corneal thickness [CCT]) measured in AS SS-OCT, we plotted receiver operating characteristic (ROC) curves. These curves aimed to determine cut-off values predicting a perioperative decrease exceeding 50% in ACA, RMS LoA and RMS HoA, as well as postoperative residual ACA higher than 1.25D. RESULTS: Preoperative ACA > 1.42D (AUC = 0.934) and >3.60D (AUC = 0.946) proved most effective in identifying subjects with perioperative decrease exceeding in ACA and RMS LoA, respectively. HIL > 3.34 mm (AUC = 0.941) was most effective in distinguishing subjects with perioperative reduction exceeding 50% in RMS HoA. Preoperative ACA > 5.78D (AUC = 0.776) and HIL > 5.03 mm (AUC = 0.700) significantly distinguished subjects with postoperative residual ACA higher than 1.25D. CONCLUSION: Optimizing the restoration of corneal astigmatism and aberrations after pterygium surgery may be facilitated by determining the optimal surgical timing based on preoperative ACA and HIL values.