Ocular residual astigmatism (ORA) does not seem to correlate with baseline refractive error among refractive surgery candidates.

PURPOSE: Ocular residual astigmatism (ORA) is defined as the difference between refractive astigmatism and anterior corneal astigmatism. A high ORA may be correlated with poorer results in patients undergoing corneal-based laser surgery. Is a high baseline refractive error related to a higher degree of ORA? METHODS: This was a retrospective analytical study including 181 right eyes of an equal number of refractive surgery candidates. Manifest subjective refraction was measured, along with a Pentacam AXL Wave corneal tomography. Via a vector analysis with this methodology, subjective cylinder was translated into the corneal plane and a vectorial subtraction was performed in order to measure ORA. Spearman's rank order test, one-way ANOVA and Chi-square were used to determine whether different levels of baseline refractive error correlate with different levels of ORA. RESULTS: Mean age was 28.33 ± 4.71 years with a female preponderance (65.7%). Mean ORA was 0.74 ± 0.39 D, with 33.1% of eyes having an ORA ≥ 0.90 D. There was not a correlation between ORA and level of myopia (rho = - 0.022; p = 0.764), nor between ORA and spherical equivalent (rho = 0.009; p = 0.903). Refractive astigmatism did not demonstrate to be correlated with ORA level either (rho = 0.078; p = 0.329). One-way ANOVA tests failed to demonstrate an association between different classifications of refractive error and level of ORA. CONCLUSIONS: In the studied population, ORA is not correlated with baseline refractive error. Every patient presenting for possible corneal-based laser refractive surgery should be evaluated for a possible high level of ORA, irrespective of their baseline ametropia level.

The Association Between Ocular Residual Astigmatism and the Efficacy of Astigmatism Correction Via Small Incision Lenticule Extraction (SMILE).

INTRODUCTION: Astigmatism correction after small-incision lenticule extraction (SMILE) surgery is affected by several factors, including ocular residual astigmatism (ORA), which accounts for the vector difference between refractive and corneal astigmatism. Previous studies revealed the relationship between ORA and astigmatism correction after laser-assisted in situ keratomileusis (LASIK). However, in SMILE surgery, no comprehensive study exploring the link between these two variables has been performed. We have therefore assessed the association between ORA and astigmatism correction after SMILE. METHODS: This was a retrospective, single-centered study. Patients with myopia or myopic astigmatism who underwent SMILE surgery using the 500-kHz Visumax laser platform and were followed up for at least 3 months were included. Patients' demographic and clinical characteristics, such as visual acuity, refractive status and corneal tomography, were recorded. ORA was calculated using Alpins Statistical System for Ophthalmic Refractive Surgery Techniques (ASSORT) Ocular Residual Astigmatism calculator. RESULTS: A total of 888 eyes (408 eyes from males and 480 eyes from females) from 444 patients (mean age [standard deviation] 32.4 ± 7.1 years) were included in our study. Mean (± SD) preoperative sphere and cylinder were - 5.45 ± 1.98 (range - 10.00-0.00) diopter (D) and - 0.89 ± 0.70 (range - 4.00-0.00) D, respectively. Calculated mean ORA was 0.68 ± 0.35 (range 0.07-3.53) D. Postoperative logMAR uncorrected visual acuity was 0.03 ± 0.31. Mean postoperative sphere and cylinder were - 0.10 ± 0.56 (range - 1.5 to 1.0) D and - 0.51 ± 0.37 (- 1.5 to 0.0) D, respectively. The Pearson correlation test revealed preoperative sphere, steep keratometry (steep-K) and ORA were statistically correlated with the amplitude of astigmatism correction (P < 0.001), and the generalized estimating equations analysis showed that ORA was negatively correlated with the amplitude of astigmatism correction (P < 0.001). CONCLUSION: The results of our study suggest that preoperative higher ORA may be associated with a lower magnitude of astigmatism correction after SMILE surgery in patients with all levels of astigmatism preoperative. TRIAL REGISTRATION: ClinicalTrials.gov: NCT05604872. Registered 3 November 2022-Retrospectively registered. https://clinicaltrials.gov/ct2/show/NCT05604872.

Differences in refractive astigmatism, anterior corneal surface astigmatism and ocular residual astigmatism between dominant and non-dominant eyes in myopia / 中华实验眼科杂志

Objective:To investigate the differences in refractive astigmatism, the anterior corneal surface astigmatism and ocular residual astigmatism between dominant and non-dominant eyes in myopia.Methods:A corss-sectional study was conducted.Two hundred and seventy-six eyes from 138 patients with myopia who were to receive corneal refractive surgery in the Refractive Surgery Center of Tianjin Eye Hospital from January to March 2018 were included.Ocular dominance was assessed with the hole-in-the-card test.The manifest refraction and corneal topography were performed in order to measure the sphericity, spherical equivalent, the astigmatism of anterior corneal surface and total cornea.Vector analysis was used to calculate the value of the ocular residual astigmatism and the components of astigmatism, including J0 and J45 of both the refractive astigmatism and the astigmatism of anterior corneal surface.This study adhered to the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of Tianjin Eye Hospital (No.201909).Results:It was found that 61.6%(85/138) of the subjects was right-eye dominant.There was no significant difference in sphericity and spherical equivalent, J0 and J45 of the refractive astigmatism and the astigmatism of anterior corneal surface between dominant and non-dominant eyes (all at P>0.05). The magnitude of the ocular residual astigmatism of the dominant eye was 0.607(0.451, 0.808)D, which was lower than 0.701(0.497, 0.901)D of the non-dominant eye, showing a statistically significant difference ( Z=-2.52, P=0.01). Conclusions:In the myopic population with no significant difference in the sphericity and spherical equivalent between the dominant and non-dominant eyes, the magnitude of the ocular residual astigmatism of the dominant eye is significantly lower than that of the non-dominant eye, which may play an important role in the ocular dominance formation.

Changes in Vector Astigmatism After Superotemporal Versus Temporal Clear Corneal Incision Cataract Surgery.

PURPOSE: To investigate vector and refractive astigmatism changes after superotemporal versus temporal clear corneal incision cataract surgery. METHODS: Patients were diagnosed with age-related cataract with corneal astigmatism < 1.5 diopters (D) and were divided into two groups: superotemporal incision (R group) and temporal incision (L group). Uncorrected visual acuity, manifest refraction, corneal topography, anterior segment optical coherence tomography was performed pre- and six months postoperatively. Total ocular astigmatism, corneal astigmatism, vector of surgically induced corneal astigmatism (SICA), non-corneal ocular residual astigmatism (N-CORA), postoperative intraocular lens decentration and tilt were analyzed.  Results: Thirty-eight subjects were included: 21, R group; 17, L group. After surgery, the N-CORA decreased significantly from 1.17±0.72 D to 0.73±0.47 D in all patients (P=0.001), 1.03±0.52 D to 0.70±0.40 D in the R group (P=0.005) and 1.35±0.90 D to 0.78±0.55 D in the L group (P=0.033). Significant differences between t:he R and L groups were found in the postoperative meridian of anterior corneal astigmatism (75.95±52.50 vs 116.79±47.29; P=0.017), total corneal astigmatism (51.65±42.75 vs 95.20±57.32; P=0.011), J45 change vector of SICA in the anterior cornea (-0.10±0.18 vs 0.00±0.11; P=0.048) and total cornea surface (-0.14±0.17 vs 0.03±0.12; P=0.001).  Conclusion: The N-CORA decreased significantly after cataract surgery. Superotemporal and temporal incisions caused differences in the meridian components of oblique astigmatism in some patients but did not have a significant effect on the magnitude of corneal astigmatism.

Correlation between ocular residual astigmatism and anterior corneal astigmatism in children with low and moderate myopia.

BACKGROUND: To assess the correlation between ocular residual astigmatism and anterior corneal astigmatism in children with low and moderate myopia. METHODS: Refractive astigmatism was determined by subjective manifest refraction. Anterior corneal astigmatism was determined by IOL Master. Thibos vector analysis was used to calculate ocular residual astigmatism. Correlation analysis was used to assess the relationship between the amounts of ocular residual astigmatism and anterior corneal astigmatism. The relationship between the vectors of ocular residual astigmatism and anterior corneal astigmatism was evaluated by a physical method. RESULTS: The study analysed 241 right eyes of 241 children aged 8 to 18 years old. In this study, the median magnitude of ocular residual astigmatism was 1.02 D, with an interquartile range was of 0.58 D. Against-the-rule ocular residual astigmatism was seen in 232 eyes (96.3%). There was a significant and moderate correlation between ocular residual astigmatism and anterior corneal astigmatism (r = 0.50, P < 0.001). Ocular residual astigmatism compensated for anterior corneal astigmatism in 240 eyes (99.6%). The mean compensation value was 1.00 ± 0.41 D (range 0.02 D to 2.34 D). Based on this effect, 37 eyes had a different axial classification of anterior corneal astigmatism and refractive astigmatism. In contrast, one eye (0.4%) had oblique ocular residual astigmatism and the ocular residual astigmatism superimposed with-the-rule anterior corneal astigmatism. CONCLUSIONS: The magnitude of ocular residual astigmatism was relatively large in myopic children and predominantly compensated for anterior corneal astigmatism. Ocular residual astigmatism should be assessed in patients before fitting them with orthokeratology lenses.

The Distribution Pattern of Ocular Residual Astigmatism in Chinese Myopic Patients.

Purpose: We aimed to investigate the distribution of ocular residual astigmatism (ORA) and its associations with age, gender, manifest refraction, and other ocular indicators in Chinese patients with myopia. Design: This is a multi-center retrospective cross-sectional study. Method: The study included 7,893 patients with myopia (7,893 eyes) aged 18-40 years from five ophthalmic centers. Anterior segment biometrics of the eyes were collected from the Pentacam. ORA and its summated vector mean were calculated using Alpins vector analysis. Compensation factor (CF) was used to evaluate the relation between ORA and corneal astigmatism. ORA in different age, gender, and refraction groups was compared. The Spearman correlation was adopted to reveal multiple ocular indicators associated with ORA, which were integrated into a multiple linear regression model to predict ORA. Results: Distribution of ORA was slightly positively skewed (Skewness= 2.111, Kurtosis = 19.660, KS P < 0.0001). Mean ORA was 0.74 ± 0.39 D (95% normal range: 0.14-1.54 D). Among all the subjects, 22.4% of the eyes had an ORA magnitude of 1.0 D or more. Undercompensation or full-compensation of anterior corneal astigmatism (ACA) by ORA prevailed in both J0 (76.99%) and J45 (58.48%). Women had higher ORA power than men (0.77 ± 0.36 D vs. 0.73 ± 0.41 D, P < 0.0001). Participants with less negative spherical equivalent (SE) or higher manifest astigmatism (MA) also had higher ORA (all P < 0.0001). ORA was significantly correlated with ACA (r = 0.405) and posterior corneal astigmatism (PCA, r = 0.356). The multivariate logistic regression analysis showed strong predictability of ORA magnitude >1.0 D using anterior segment parameters (area under the receiver operating characteristic curve: 0.739). Conclusion: ORA is present in Chinese adults with myopia and is affected by multiple ocular factors. Our findings may provide valuable information about ORA distribution in candidates for refractive surgery, helping optimize the outcome of astigmatism correction.

Influence of Ocular Residual Astigmatism on the Correction of Myopic Astigmatism by Toric Implantable Collamer Lens: A Comparative Study With Femtosecond Laser Small Incision Lenticule Extraction.

Purpose: To evaluate the influence of the origin of astigmatism on the correction of myopic astigmatism by toric implantable collamer lens (TICL) and compare it with femtosecond laser small incision lenticule extraction (SMILE). Methods: Ocular residual astigmatism (ORA) was determined by vector analysis using manifest refraction and Scheimpflug camera imaging of the anterior cornea. One-to-one matching between the TICL and SMILE groups was performed by preoperative manifest refractive astigmatism (RA) and ORA, tolerating a maximum difference of 0.50 diopter (D) for RA and 0.25 D for ORA. Patients of each group were further divided into groups according to ORA (high > 1.0 D; low ≤ 1.0 D). The baseline and 12-month postoperative data were analyzed. Data are expressed as mean ± standard deviation (SD). A value of p less than 0.05 was considered statistically significant. Results: For the TICL group, no significant differences in the postoperative RA, safety index, efficacy index, index of success (IOS), correction index (CI), and angle of error (AOE) were found between high (n = 36) and low ORA (n = 36) groups (Mann-Whitney U test, p > 0.05). For the SMILE group, the postoperative RA (high: -0.67 ± 0.43 D, low: -0.39 ± 0.29 D, Mann-Whitney U test, p = 0.003) and IOS (high: 0.50 ± 0.43, low: 0.25 ± 0.23, Mann-Whitney U test, p = 0.003) were greater in the high ORA group. When comparing TICL and SMILE groups, the mean postoperative RA (TICL: -0.48 ± 0.29 D, SMILE: -0.67 ± 0.43 D, Mann-Whitney U test, p = 0.03) and IOS (TICL: 0.32 ± 0.23, SMILE: 0.50 ± 0.43, Mann-Whitney U test, p = 0.03) were significantly higher in the SMILE group when the ORA was >1.0 D. Conclusion: Both TICL and SMILE are effective in correcting myopic astigmatism. ORA has a lesser effect on TICL than on SMILE.

Effect of Postoperative Ocular Residual Astigmatism (ORA) on Treatment Outcome After Myopic Laser in situ Keratomileusis (LASIK).

Purpose: To analyze the impact of postoperative ocular residual astigmatism (ORA) on refraction, visual acuity and subjective satisfaction after myopic laser-in-situ-keratomileusis (LASIK) by a comprehensive analysis, which includes clinically relevant data and patient-reported outcomes. Material and Methods: To evaluate the influence of ORA, comparison groups were built following Archer et al. Myopic patients were subdivided by the fraction ORA/MRC (matched and not matched for MRC) (MRC = manifest refractive cylinder), ORA magnitude and CA magnitude in high ORA eyes (CA = corneal astigmatism). Refractive and visual data were analyzed via retrospective cross-sectional analysis for multiple parameters. The subjective satisfaction was analyzed retrospectively 3-4 years after having LASIK via patient reported outcome analysis. Results: Refractive outcome: Only when grouped by ORA magnitude only, high ORA eyes resulted in approximately twice as cylinder magnitude compared to eyes with preoperative lower ORA. Furthermore, there appeared to be no statistically significant differences in any case. Visual outcome: There appeared to be no statistically significant differences for visual acuity parameters (safety index, efficacy index). Patient reported outcome: When grouped by the rate of ORA/MRC not matching for MRC, there were statistically significant differences in the subjective satisfaction (p = 0.006) and the postoperative side effects (p = 0.001, p = 0.01, p = 0.006), those differences appeared less strong when matched for MRC treated and result better for a higher ratio of ORA/MRC. Conclusion: Patients with postoperatively high ORA report on higher satisfaction with treatment results than patients with postoperatively low ORA. This did not correlate with differences in the refractive nor visual outcome. As a matter of fact, there is a discrepancy between the objective analysis results and the subjective satisfaction of patients.

Influence of Ocular Residual Astigmatism and Target-Induced Astigmatism on the Efficacy of the Implantation of a Toric Implantable Collamer Lens With Central Hole for Myopic Astigmatism Correction.

PURPOSE: To investigate the effects of ocular residual astigmatism (ORA) and target-induced astigmatism (TIA) on the efficacy of toric implantable collamer lens (TICL) with central hole for myopic astigmatism correction. METHODS: Retrospective case series. One hundred and eighteen eyes implanted with a TICL (V4c) from 118 patients were included. Subjective refraction and corneal topography were examined preoperatively, at 1 and 12 months postoperatively. The eyes were divided into the low-ORA ( ≤ 0.5 D) and high-ORA (>0.5 D) groups based on vector analysis, and into the low-TIA (≥0.75D and <2 D) and the high-TIA (≥2 D and ≤ 4 D) groups according to preoperative refractive astigmatism. Correction index (CI) and index of success (IOS) were compared between different groups. RESULTS: All surgeries were uneventful, and no complications occurred during follow-up. At 1 and 12 months postoperatively, no significant differences were found in CI or IOS values between the high and low ORA groups, while significantly higher CI and lower IOS were detected in the high-TIA group than in the low-TIA group (P < 0.05). No significant difference was found in CI between 1 and 12 months postoperatively in either group (P > 0.05). However, significantly lower IOS was found at 12 months compared with 1 month postoperatively for each group (P < 0.05). CONCLUSIONS: Toric implantable collamer lens (TICL) implantation is effective in correcting myopic astigmatism and is more effective in eyes with high TIA, while ORA has a minor effect.

Contributions of Anterior Corneal and Ocular Residual Astigmatism to Autorefraction Astigmatism in a Myopic Adult Sample.

AIM: To evaluate the contributions of anterior corneal and ocular residual astigmatism to autorefraction astigmatism in adult myopic and myopic astigmatic subjects and how these compensate each other. SUBJECTS AND METHODS: This retrospective study was completed in private eye centre, Ismailia, Egypt, between September 2017 and November 2019. The study included eyes with myopia (0.5 to 10.0D) or myopic astigmatism (0 to 8.5D). The refractive errors, including autorefraction astigmatism, were measured after using 1% cyclopentolate with autorefractometer (Topcon, Tokyo Optical Co., Ltd., Japan). Corneal topography (Sirius; CSO, Florence, Italy) was used to measure anterior corneal astigmatism. Ocular residual astigmatism was measured by vectorial subtraction of the anterior corneal astigmatism from autorefraction astigmatism determined to the corneal plane. RESULTS: This study included 1158 eyes (right 582 and left 576) with myopia or myopic astigmatism of 582 participants (206 males with 406 eyes and 376 females with 752 eyes). The mean±SD age of the total participants was 26±5.7 years, range (21 to 50 years). The mean±SD of spherical error was -3.2±1.9D, range (-0.5 to -10.0D). The mean±SD of autorefraction astigmatism was 1.13±1.1D; range (0.5 to 8.5D). The mean±SD of anterior corneal astigmatism was 1.22±0.8D; range (0.03 to 5.6D). The mean±SD of ocular residual astigmatism was 0.6±0.5D; range (0 to 4.8D). Of the total eyes, 75.4% had significant autorefraction astigmatism, 82.5% had significant anterior corneal astigmatism, and 16.8% had significant ocular residual astigmatism. CONCLUSION: The percentage of the significant autorefraction astigmatism (>0.5D) was 75.4% which is mainly anterior corneal. In 26.8% of participants, anterior corneal astigmatism is compensated by ocular residual astigmatism.

[Astigmatism]. / Astigmatismus.

Astigmatism is the most frequent refractive error worldwide followed by hyperopia and myopia. Internal astigmatism has to be differentiated from external astigmatism. Furthermore, external astigmatism can be divided into "with the rule", "against the rule" and "oblique". The summation of internal and external astigmatism results in the refractive cylinder. Astigmatism has for a long time been regarded as a two-dimensional phenomenon; however, only a three-dimensional consideration expanded the view on existing analytical methods (topography and tomography). Alpins' vector analysis is a commonly used method for treatment planning. Multiple options exist for treatment of astigmatism with conservative approaches, such as eyeglasses or toric contact lenses as well as various surgical procedures, such as photorefractive keratectomy, femtosecond laser-assisted keratotomy, laser in-situ keratomileusis, small incision lenticule extraction and toric intraocular lens implantation.

Evaluating internal and ocular residual astigmatism in Chinese myopic children.

PURPOSE: To investigate the nature of internal astigmatism (IA) and ocular residual astigmatism (ORA) in Chinese myopic children and to identify factors that may influence IA and ORA. METHODS: A total of 206 eyes of 206 myopic children (97 boys and 109 girls; 10.95 ± 2.2 years) were enrolled in this cross sectional study. Total ocular astigmatism (TOA), anterior corneal astigmatism (ACA), posterior corneal astigmatism (PCA) and total corneal astigmatism (TCA) were measured directly using either a Hartmann-Shack wavefront sensor or a Pentacam. IA and ORA were calculated by Fourier vector analyses (the definitions of IA and ORA are: IA = TOA - ACA - PCA, ORA = TOA - ACA). Spearman or Pearson correlation was adopted to detect multiple factors that may influence IA and ORA, which were then predicted by linear regressions. Modified compensation factors were applied to evaluate the inter-relationship between corneal astigmatism and ORA. RESULTS: While the mean values of IA and ORA were -0.52 DC × 94.8° and -0.63 DC × 93.0°, respectively, the percentage of ORA power over 1.00 D was as high as 28.64%. Full or under-compensation of ACA by ORA predominated in the enrolled subjects. The mean ORA J0 and J45 were -0.311 ± 0.236 and -0.032 ± 0.156 D, respectively, negatively correlated with the corresponding ACA components (J0: r = -0.276, J45: r = -0.616, p < 0.001). While age was not correlated with either IA or ORA (p > 0.1), the power of IA or ORA was correlated inversely with the axial length (IA: r = -0.193, p = 0.005; ORA: r = -0.169, p = 0.015) and positively with the spherical equivalent refraction (IA r = 0.195, p = 0.005; ORA r = 0.213, p = 0.002) and power of corneal astigmatism (IA-ACA: r = 0.302, IA-TCA: r = 0.368, ORA-ACA: r = 0.334, ORA-TCA: r = 0.293). Girls had larger IA powers than boys (0.741 ± 0.345 D vs 0.651 ± 0.340, p = 0.036). CONCLUSIONS: Full or under-compensation of ACA by ORA is common in Chinese myopic children, and the compensation efficiency may decrease with age. Among Chinese children with myopia, a larger ORA is more prevalent with less myopia and greater corneal astigmatism.

Pseudolentogenic astigmatic effect of multifocal intraocular lenses: non-corneal ocular residual astigmatism (N-CORA) as a new parameter in astigmatic change analysis.

PURPOSE: This study was initiated to introduce the term non-corneal ocular residual astigmatism (N-CORA) as a new parameter in astigmatic change analysis after implantation of two different types of non-toric, multifocal intraocular lenses (MIOL). METHODS: Seventy-two eyes from 72 consecutive patients after MIOL surgery were studied in terms of a retrospective, cross-sectional data analysis. Two types of spherical MIOL were used. Surgical technique in all patients was a 2.4-mm incision phacoemulsification, performed by one surgeon. To investigate the magnitude and axis of astigmatic changes, the true corneal astigmatism and Alpins vector method were applied. RESULTS: There were no statistically significant between-group differences related to the preoperative refraction or ocular residual astigmatism (ORA). After surgery, the mean refractive surgically induced astigmatism (RSIA) and the topographic SIA (TSIA) did not differ significantly between the lenses. The magnitude and orientation of ORA and N-CORA changed after surgery. CONCLUSIONS: There are no statistically significant differences in postoperative ORA in magnitude or axis when implanting different types of MIOL. The similarity of N-CORA between both MIOL types shows that both diffractive and refractive asymmetric MIOLs with plate haptics have the same pseudolentogenic astigmatic effect which could be presented in terms of the newly introduced parameter N-CORA.

Ocular residual astigmatism (ORA) in pre-cataract eyes prior to and after refractive lens exchange.

The purpose of this study was to analyze ocular residual astigmatism (ORA) before and after implantation of two different optical types of non-toric multifocal intraocular lenses (MIOL) in pre-cataract patients. This retrospective cohort study analyzed 72 eyes from 72 consecutive patients after MIOL surgery . To investigate magnitude and axis of astigmatic changes, the concepts of true corneal astigmatism and Alpins vector method were applied. There were no statistically significant between-group differences prior to surgery. The mean refractive surgically induced astigmatism (RSIA) (P = 0.063) and the topographic SIA (TSIA) (P = 0.828) did not differ significantly between the lenses, and the summated vector mean for ORA was reduced in terms of magnitude by approximately 0.30 Diopter. ORA in pseudophakic eyes mainly results from the posterior corneal surface and less from IOL tilting, postoperative posterior capsule shrinkage, or secondary cataract.

Evaluation of the diagnostic ability of vector parameters characterizing the corneal astigmatism and regularity in clinical and subclinical keratoconus.

PURPOSE: To evaluate the diagnostic ability of the vector parameters ocular residual astigmatism (ORA), topography disparity (TD) and topographic astigmatism CorT (anterior and total) for the detection of clinical and subclinical keratoconus, and to develop a detection model based on them. METHODS: This study comprised a total of 61 keratoconus eyes (KC group), 19 eyes with subclinical keratoconus (SKC group) and 100 healthy eyes (control group). In all cases, a complete eye exam was performed including an analysis of the corneal structure with the Sirius system (Costruzione Strumenti Oftalmici, CSO). Likewise, the iASSORT software (ASSORT Pty) was used to calculate in all cases the vector parameters ORA, TD and CorT. RESULTS: Significant differences among groups were found in ORA, TD and CorT (anterior and total) (p<0.001). The diagnostic ability of ORA (cutoff 1.255 D, sensitivity/specificity 82%/92%) and TD (cutoff 1.035 D, sensitivity/specificity 78.5%/86%) for the detection of keratoconus was good, whereas anterior and total CorT showed a poorer diagnostic ability. ORA (cutoff 0.925 D, sensitivity/specificity 63.2%/77%) and TD (cutoff 0.710 D, sensitivity/specificity 74%/68%) showed an acceptable diagnostic ability for the detection of subclinical keratoconus, but anterior and total CorT did not. A detection model for subclinical keratoconus was obtained by logistic regression analysis involving TD, anterior corneal spherical aberration and posterior high order aberrations. CONCLUSIONS: The vector parameters ORA and TD are useful for the diagnosis of clinical and subclinical keratoconus. In this last condition, the combination of TD with corneal aberrometric data provides a consistent detection model.

Applying vector analysis to evaluate influence of ocular residual astigmatism on astigmatism correction by FS-LASIK / 眼科新进展

Objective To investigate the influence of ocular residual astigmatism (ORA) on the correction of astigmatism by FS-LASIK with vector analysis.Methods The records of 182 patients who had accept FS-LASIK between January,2016 and April,2016 were retrosepectively reviewed.The patients whose ORA ≥ refractive cylinder were assigned to high ocular residual astigmatism group (HORA group),ORA ＜ refractive cylinder were assigned to low ocular residual astigmatism group (LORA group).All of the patients were followed 6 months or more.The visual acuity,error ratio and correction ratio were compared between HORA group and LORA group.Results The preoperative ORA of all patients was (0.61 ± 0.27) D,in which ＞ 0.75 D were 58 cases (31.9％),and the HORA group was more than the LORA group (P ＜ 0.05).At postoperative 6 months,there was no statistically significant difference in vision acuity between the HORA group (1.06 ± 0.15) and LORA group (1.08 ± 0.15) (t =0.97,P =0.35).There was statistically significant difference in the error ratio between the HORA group (58.11 ± 63.23) ％ and LORA group (26.12 ± 35.37) ％ (t =3.43,P ＜ 0.05).There was statistically significant difference in the correction ratio between the HORA group (146.45 ± 86.63) ％ and LORA group (122.56 ± 36.31) ％ (t =2.81,P ＜ 0.05).Conclusion The error ratio and correction ratio of astigmatic correction by FSLASIK is significantly higher in eyes with high ORA than in eyes with low ORA.Vector analysis should been carried out before the FS-LASIK.

Correlation of major components of ocular astigmatism in myopic patients.

PURPOSE: To investigate the correlation of major components of ocular astigmatism in myopic patients in an academic hospital. METHODS: This cross-sectional study was conducted on 376 eyes of 188 patients who were referred to Farabi Eye Hospital for refractive surgery. Preoperative examinations including refraction and corneal topography were performed for all candidates to measure refractive and corneal astigmatism. Ocular residual astigmatism was calculated using vector analysis. Pearson's correlation and ANOVA analysis were used to evaluate the strength of the association between different types of astigmatism. Both eyes were defined as cluster and the Generalized Estimating Equations (GEE) analysis were performed. RESULTS: Mean age of 119 women (63.3%) and 69 men (36.7%) was 27.8 ± 5.7 years. Mean refractive error based on spherical equivalent was -3.59 ± 1.95D (range, -0.54 to -10.22D). Mean refractive and corneal astigmatism was 1.97 ± 1.3D and 1.85 ± 1.01D, respectively. Mean amount of ORA was 0.65 ± 0.36D.There was a significant correlation between ORA and refractive astigmatism(r=0.23, p<0.001), corneal and refractive astigmatism (r=0.91, p<0.001) and a weak correlation between ORA and corneal astigmatism (r=0.13, p=0.014). There was a significant correlation between J0 and J45 values of ORA and corneal astigmatism (p<0.001). CONCLUSION: There is a significant correlation between ORA and refractive astigmatism, refractive and corneal astigmatism and a weak correlation between ORA and corneal astigmatism in refractive surgery candidates. Identifying the type of astigmatism and preoperative measurement of ocular residual astigmatism is highly recommended prior to any refractive surgery, especially in cases with significant astigmatism.

Clinical utility of ocular residual astigmatism and topographic disparity vector indexes in subclinical and clinical keratoconus.

PURPOSE: We aimed to characterize the distribution of the vector parameters ocular residual astigmatism (ORA) and topography disparity (TD) in a sample of clinical and subclinical keratoconus eyes, and to evaluate their diagnostic value to discriminate between these conditions and healthy corneas. METHODS: This study comprised a total of 43 keratoconic eyes (27 patients, 17-73 years) (keratoconus group), 11 subclinical keratoconus eyes (eight patients, 11-54 years) (subclinical keratoconus group) and 101 healthy eyes (101 patients, 15-64 years) (control group). In all cases, a complete corneal analysis was performed using a Scheimpflug photography-based topography system. Anterior corneal topographic data was imported from it to the iASSORT software (ASSORT Pty. Ltd), which allowed the calculation of ORA and TD. RESULTS: Mean magnitude of the ORA was 3.23 ± 2.38, 1.16 ± 0.50 and 0.79 ± 0.43 D in the keratoconus, subclinical keratoconus and control groups, respectively (p < 0.001). Mean magnitude of the TD was 9.04 ± 8.08, 2.69 ± 2.42 and 0.89 ± 0.50 D in the keratoconus, subclinical keratoconus and control groups, respectively (p < 0.001). Good diagnostic performance of ORA (cutoff point: 1.21 D, sensitivity 83.7 %, specificity 87.1 %) and TD (cutoff point: 1.64 D, sensitivity 93.3 %, specificity 92.1 %) was found for the detection of keratoconus. The diagnostic ability of these parameters for the detection of subclinical keratoconus was more limited (ORA: cutoff 1.17 D, sensitivity 60.0 %, specificity 84.2 %; TD: cutoff 1.29 D, sensitivity 80.0 %, specificity 80.2 %). CONCLUSION: The vector parameters ORA and TD are able to discriminate with good levels of precision between keratoconus and healthy corneas. For the detection of subclinical keratoconus, only TD seems to be valid.

Ocular residual astigmatism and topographic disparity vector indexes in normal healthy eyes.

PURPOSE: To define a range of normality for the vectorial parameters Ocular Residual Astigmatism (ORA) and topography disparity (TD) and to evaluate their relationship with visual, refractive, anterior and posterior corneal curvature, pachymetric and corneal volume data in normal healthy eyes. METHODS: This study comprised a total of 101 consecutive normal healthy eyes of 101 patients ranging in age from 15 to 64 years old. In all cases, a complete corneal analysis was performed using a Scheimpflug photography-based topography system (Pentacam system Oculus Optikgeräte GmbH). Anterior corneal topographic data were imported from the Pentacam system to the iASSORT software (ASSORT Pty. Ltd.), which allowed the calculation of the ocular residual astigmatism (ORA) and topography disparity (TD). Linear regression analysis was used for obtaining a linear expression relating ORA and posterior corneal astigmatism (PCA). RESULTS: Mean magnitude of ORA was 0.79 D (SD: 0.43), with a normality range from 0 to 1.63D. 90 eyes (89.1%) showed against-the-rule ORA. A weak although statistically significant correlation was found between the magnitudes of posterior corneal astigmatism and ORA (r=0.34, p<0.01). Regression analysis showed the presence of a linear relationship between these two variables, although with a very limited predictability (R(2): 0.08). Mean magnitude of TD was 0.89D (SD: 0.50), with a normality range from 0 to 1.87D. CONCLUSION: The magnitude of the vector parameters ORA and TD is lower than 1.9D in the healthy human eye.

Postoperative astigmatic outcomes based on the haptic axis of intraocular lenses inserted in cataract surgery.

PURPOSE: This study was conducted to compare post-operative astigmatic outcomes of two groups, with-the-rule (WTR) and against-the-rule (ATR) astigmatism patients, according to the haptic axis of intraocular lenses (IOLs) inserted in cataract surgery. METHODS: Seventy-two eyes with WTR astigmatism and 79 eyes with ATR astigmatism had cataract surgery through a clear corneal temporal incision. These two groups of eyes were then each divided into 2 groups based on whether the haptic axis of the inserted IOL was at 180° or 90°. For ATR patients, the outcomes were analyzed according to the three types of IOLs. RESULTS: There was no difference in corneal astigmatism, but WTR patients with a 180° haptic axis of the inserted IOL and ATR patients with a 90° hepatic axis of the inserted IOL had a significant decrease in postoperative refractive astigmatism (p < 0.05). The changes in ATR astigmatism according to the IOL type were more effective in single-piece acrylic IOLs than in the three-piece polymethylmethacrylate haptic IOL group. CONCLUSIONS: Insertion of the IOL at the 180° haptic axis in WTR patients and at 90° in ATR patients during cataract surgery may have an effect in reducing pre-existing astigmatism. This observed effect was not consistent among the different types of IOLs.