Axis Of Astigmatism Research Articles

Comparison of Wavefront-Guided Femtosecond LASIK and Optimized SMILE for Correction of Moderate-to-High Astigmatism.

To compare refractive outcomes, higher order aberrations (HOAs), and the changes in contrast sensitivity after wavefront-guided femtosecond laser-assisted in situ keratomileusis (WFG LASIK) and optimized small incision lenticule extraction (SMILE) for moderate-to-high astigmatism correction. This prospective, randomized study included 87 eyes: 40 eyes in the WFG LASIK group and 47 eyes in the SMILE group. Manual cyclotorsion compensation by marking the horizontal axis before SMILE surgery was used for optimized SMILE. Refractive diopter, aberrations, and contrast sensitivity were assessed 3 months postoperatively. The Alpins vector analysis method was used to analyze the astigmatic changes after surgery. There were no significant differences in the corrected distance visual acuity and refraction between the two groups after surgery. The fitted curve of surgically induced astigmatism versus target induced astigmatism was described as y = 0.9905 x + 0.0009 in the WFG LASIK group and y = 0.9672 x + 0.0026 in the SMILE group. The percentage of corneal astigmatism axis change within 5 degrees was statistically significant (chi-square test: 10.632, P = .001). HOAs increased in both the WFG LASIK and SMILE groups after surgery (t = -3.655, P = .001, t = -3.784, P = .001, respectively). However, comparison of the changes of HOAs between both groups was not significant (t = -0.565, P = .575). The improvement in contrast sensitivity in the WFG LASIK group was significantly higher than that in the SMILE group. WFG LASIK and optimized SMILE can achieve similar outcomes for astigmatism correction. Optimized SMILE with marking could achieve good astigmatism correction, even without an eye tracking system. [J Refract Surg. 2021;37(3):166-173.].

Evaluation of Astigmatic Correction Using Vector Analysis after Combined Femtosecond Laser-Assisted Phacoemulsification and Intrastromal Arcuate Keratotomy.

The aim of this study was to evaluate astigmatic correction in patients with mild to moderate astigmatism after combined femtosecond laser-assisted cataract surgery (FLACS) and intrastromal arcuate keratotomy (ISAK), using vector analysis. This retrospective study included patients with corneal astigmatism of 0.5–3.0 diopters (D) who underwent FLACS and ISAK. Vector analyses of astigmatism were performed using the Alpins method, considering three vectors: target-induced astigmatism (TIA), surgically induced astigmatism (SIA), and difference vector (DV). Magnitude of error (ME), angle of error (AE), correction index (CI), and coefficient of adjustment (CA) were calculated. Subgroup analysis according to the axis of astigmatism, patient age, and white to white (WTW) diameter was conducted. In total, for the 79 eyes of 79 patients, the TIA was 1.21 ± 0.52 D, the SIA was 0.76 ± 0.53 D, and the DV was 0.86 ± 0.50 D. The ME (difference between SIA and TIA) was −0.46 ± 0.45 D, and the CI (ratio of SIA and TIA) was 0.62 ± 0.34; both these parameters demonstrated slight undercorrection. The CA (inverse of the CI) was 2.48 ± 2.61. The AE was 4.02° ± 28.7°, and the absolute AE was 21.7° ± 19.0°. In the univariate regression analyses to identify factors that affected the CI, there was a negative correlation between age and the CI (P=0.022). In conclusion, vector analysis after the combined FLACS and ISAK revealed slight undercorrection, regardless of the astigmatism meridian. The precision of the nomogram should be improved through long-term vector analysis for the results of arcuate keratotomy and through further research on the relationship between patient demographics and CI. Overall, this study has shown that FLACS and ISAK could reduce postoperative corneal astigmatism effectively and safely.

Gender and age distribution of refractive errors in an optometric clinical population

AimTo determine the patterns of distribution of refractive errors in a clinical sample of patients examined in an optometry practice. MethodIn this retrospective study, the clinic records of 6687 patients aged 6 to 85 years comprising 2168 (32.2%) males and 4519 (67.5%) females were reviewed. Refractive error were analysed according to gender, age, as well as types and categories including axis of astigmatism using the vector power analysis method where the traditional sphero-cylinder was transformed into J0 (primary) and J45 (oblique) astigmatic components. ResultsOnly the analysis for right eye was reported as right and left spherical equivalent were similar. The mean with standard deviations for refractive errors were: Myopia: −1.95 ± 2.6, hyperopia: 1.04 ± 0.9, astigmatism: −1.22 ± 0.71 and anisometropia: −0.01 ± 2.5 DS. The distributions with significant changes included males that were significantly more myopic and astigmatic, while females were more hyperopic across the age groups. Furthermore, myopia decreased, while hyperopia, astigmatism and anisometropia increased with increasing age. Unique findings from this study include: myopia peaked earlier, second hyperopic shift commenced after age 82 years and the distribution of severity of astigmatism contrasts with previous understanding. ConclusionAlthough the patterns of distribution of refractive errors in patients aged 6 to 85 years corroborates previous findings, myopia and hyperopia peak, as well as severity of astigmatism were unique to the present study. Results from non-clinic populations will be useful to confirm trends reported in this study.

Comparison of corneal refractive power and astigmatism measured by the new anterior segment optical coherence tomographic device and Scheimpflug imaging device in age-related cataract patients

Objective: To compare the difference and agreement of corneal refractive power and astigmatism measured by the new swept-source anterior segment optical coherence tomography (SS-AS-OCT) device (CASIA2) and Scheimpflug imaging device (Pentacam) in age-related cataract patients. Methods: In this cross-sectional study, 112 eyes of 112 patients with age-related cataract were examined before phacoemulsification in the Tianjin Medical University Eye Hospital from April to May 2020. The steep keratometry (Ks), flat keratometry (Kf), mean keratometry (Km), degree and axis of astigmatism of the corneal anterior and posterior surfaces and the total cornea were recorded. The difference in astigmatism was analyzed by the arithmetic method and the vector method. The difference of data was evaluated using Paired t test or Wilcoxon test. The agreement of data was evaluated using Bland-Altman plots. Results: The patients were 44 males and 68 females with an average age of (67±10) years. There were no statistically differences in the Ks and Km values of the corneal anterior surface between the Pentacam and the CASIA2 (both P>0.05). There was significant difference in the Kf values of the corneal anterior surface between the Pentacam and the CASIA2 [(44.24±1.73) D vs. (44.14±1.64) D; t=2.278; P<0.05]. The Ks, Kf, and Km values of the posterior surface of the cornea measured by the Pentacam and the CASIA2 were (-6.60±0.29) D vs. (-6.45±0.28) D, (-6.34±0.27) D vs. (-6.17±0.25) D, and (-6.47±0.26) D vs. (-6.31±0.25) D, respectively. The Ks, Kf, and Km values of the total cornea measured by the two instruments were (45.08±1.84) D vs. (43.94±1.64) D, (44.18±1.85) D vs. (43.02±1.64) D, and (44.63±1.82) D vs. (43.48±1.60) D, respectively. There were significant differences in the Ks, Kf, and Km values of the posterior surface of the cornea and the total cornea (t=-14.440, -13.522, -17.186, 21.016, 21.819, 22.981; all P<0.01). The degree and axis of astigmatism of the corneal anterior and posterior surfaces and the total cornea showed no statistically significant difference (all P>0.05). Vector operation results showed that the astigmatism difference vector (DV) of the Pentacam and the CASIA2 on the anterior surface of the cornea was 0.06 D@57°±0.64 D,>0.50 D in 47 eyes (41.96%). The astigmatism DV on the posterior surface of the cornea was 0.07 D@174°±0.21 D, >0.50 D in 2 eyes (1.79%). The astigmatism DV on the total cornea was 0.13 D@3°±0.69 D,>0.50 D in 59 eyes (52.68%). The results of the two devices were positively correlated (r values of the Ks, Kf, Km, and astigmatism degree on the anterior surface of the cornea were 0.970, 0.968, 0.976, and 0.697, respectively, on the posterior surface of the cornea were 0.918, 0.875, 0.925, and 0.517, respectively, and on the total cornea were 0.951, 0.955, 0.959, and 0.622, respectively; all P<0.01). Bland-Altman analysis showed that the Ks, Kf, Km, and astigmatism degree of the corneal anterior and posterior surfaces measured by the two devices were consistent, with 2.68% to 8.04% of the measured values outside 95% limits of agreement (95%LoA). The 95%LoA of the total corneal Ks, Kf, and Km between the two devices was 0.01 to 2.28 D, 0.06 to 2.27 D, and 0.10 to 2.20 D, respectively, with a wide 95%LoA range and poor consistency. Conclusions: The corneal refractive power and astigmatism measured by the CASIA2 and the Pentacam shows little difference on the anterior surface of the cornea, with good agreement. However, the refractive power results of the posterior surface of the cornea and the total cornea show great difference, suggesting that these two instruments cannot be used interchangeably in clinical practice. (Chin J Ophthalmol, 2021, 57: 48-55).

The Utility of Recycled Eyeglasses: A Pilot Study at the Los Angeles County Department of Health Services.

Background:The cost of eyeglasses is variably covered by medical insurance and thus is a significant barrier for patients in lower socioeconomic classes. We evaluated the efficacy of Recycle Vision (RV) at LAC+USC Medical Center, a monthly clinic run by volunteer medical students that provides free donated eyeglasses.Methods:A convenience sample of 30 patients was surveyed from August 1, 2019 to December 31, 2019. Patients’ prescriptions were matched with available eyeglasses based on spherical equivalent and axis of astigmatism using Winglasses software algorithm; patients selected glasses from these options based on subjective improvement of vision. All participants consented to a phone follow-up survey 1 month after initial visit to gauge satisfaction with glasses and rate difficulty in completing daily activities pre- and post-RV visit on a scale of 1 to 5 (5 being the greatest), with a 100% response rate.Results:Of the 30 study participants, 90% received eyeglasses from RV, with reported improvement in ease of daily activities of 3.96. 67% of respondents stated that if RV clinic did not exist, they would not have obtained glasses elsewhere; cost was the most commonly (70%) cited barrier. Upon follow-up, average likelihood of patients referring friends/family to RV was 4.07 (SD 1.14).Conclusion:The majority of RV patients received free eyeglasses and had subsequent improvement in their quality of life. This pilot study demonstrates that programs offering free eyeglasses can effectively correct refractive error and can offer a practical public health solution to improve functionality for underserved populations.

Grading Sphero-Cylinder Spectacle Similarity.

BackgroundPortable autorefractors can estimate refractive error in remote locations, but sphero-cylinder comparison and donated-spectacle dispensing are not yet simple.MethodsNormal astigmats determined best corrected acuity, then degraded 1 logMAR (Grade A), 3 logMAR (Grade B), and 6 logMAR (Grade C) to determine limits of astigmatism axis and power at these levels. The cylindrical refraction was vector transformed with J0 on the abscissa and J45 on the ordinate.ResultsTen subjects produced multiple refractions at the interfaces of Grades A, B, and C representing ovals on the J0 and J45 coordinates. When rotated, the vertical axis represented 45° or 135°, the horizontal long axis was 1.6× the short axis. The size of the ovals positively correlated with cylinder power. Given a target refraction, the comparability of a candidate lens was demonstrated on our interactive database yielding a simple A, B, C, or worse grade for cylinder, spherical equivalent, and pupillary diameter.Conclusion(s)/RelevanceInputting a remote autorefraction, pupillary diameter and age as target and a donated spectacle as the candidate with a “B” grade similarity would be expected to attain 20/40 acuity (3 logMAR degrade) if best corrected visual acuity was 20/20. This practical Excel database could facilitate widespread remote lay dispensing of the cylinder as well as spherical spectacles. The grade similarity can also compare refracting tools such as photoscreeners and hand-held autorefractors.Clinical Trials RegistryNCT04297969.

Динамика функционального состояния слезной пленки и параметров авторефрактометрии на фоне инстилляций препаратов гиалуроновой кислоты различной вязкости

Aim: to study the changes in the critical parameters of tear film stability and autorefractometry in patients with mild dry eye syndrome (DES) after instilling artificial tear products of different viscosity. Patients and Methods: thirty patients aged 23–70 with mild bilateral DES were examined using the Visionix VX120+Dry Eye multi-diagnostic unit equipped with the TF-Scan to fix and assess tear film stability and tear breakup time (TBUT). The critical refraction and tear film parameters were evaluated by keratometry, corneal topography, TBUT, and tear meniscus height measurements. Next, an artificial tear product was instilled, i.e., group 1 (14 patients, 28 eyes) received a 0.15% sodium hyaluronate-based preparation, and group 2 (16 patients, 32 eyes) received a 0.4% sodium hyaluronate-based preparation. The examination was repeated after 30 sec and 5 min. Controls were seven healthy individuals (14 eyes). Results: in DES, breaks in the tear film appeared earlier and affected greater corneal surface area. A "Destabilized tear film area" parameter of the Visionix VX120+Dry Eye contributed significantly to the knowledge of tear film functionality, thereby empowering the diagnostic armamentarium in DES. As early as 30 sec after instillation of both artificial tear preparations, breakup-free time tended to increase, while the area of tear film destabilization tended to reduce. After 5 min, this trend continued to increase, particularly after instilling 0.15% sodium hyaluronate-based preparation. At the same time, changes in keratometry readings (i.e., sphere and cylinder) and astigmatism axis orientation were reported. Corneal refractive power (more in the flattest axis) increased, in particular, after the instillations of 0.15% hyaluronic acid. The range of changes was 0.00–0.75 D for the sphere power, 0.00–0.50 D for the cylinder power, and 0–69 degrees for astigmatism axis orientation. Conclusions: our findings with the Visionix VX120+Dry Eye multi-diagnostic unit demonstrate a significant variation of autorefractometry readings in DES depending on the extent of ocular surface hydration. These phenomena raise questions about the accuracy of autorefractometry readings. Therefore, autorefractometry should be performed after normalizing tear film volume and stability. Keywords: dry eye syndrome, Visionix®, autorefractometry, tearscopy, the effect of artificial tears on results. For citation: Brzheskiy V.V., Efimova E.L., Kopylova M.A. et al. Changes in the functionality of tear film and autorefractometry reading after instillations of artificial tear products of different viscosity. Russian Journal of Clinical Ophthalmology. 2021;21(4):200–204 (in Russ.). DOI: 10.32364/2311-7729-2021-21-4-200-204.

Effect of repeated peribulbar triamcinolone injection on corneal topography in patients with thyroid eye disease

IntroductionStudies have shown that repeated peribulbar triamcinolone injections reduce the inflammatory signs of moderate to severe thyroid eye disease (TED). Other studies found that TED was associated with greater with-the-rule corneal astigmatism owing to fibrosis of the soft tissue in the superolateral orbital region. This study aimed to detect the effect of repeated peribulbar triamcinolone injections in patients with moderate to severe TED on corneal topography and astigmatism.Patients and methodsA prospective, controlled, and randomized study was conducted that included 30 eyes with moderate to severe TED who underwent repeated peribulbar triamcinolone injections in addition to pretreatment and posttreatment corneal topography using Occulus Pentacam. The patients received repeated peribulbar injections of 20-mg triamcinolone acetate (40 mg/ml) for four doses with a 1-week interval.ResultsOn a comparison between pretreatment and posttreatment corneal topographic measures, it revealed a highly statistically significant difference between pretreatment and posttreatment results according to K-max and Pentacam astigmatism. In contrast, the Pentacam astigmatism axis and central corneal thickness by Pentacam show a statistically insignificant difference between preinjection and postinjection periods. A comparison between the mean difference of pretreatment and posttreatment refraction showed a statistically significant difference between both according to mean differences of the cylinder.ConclusionA significant change in corneal curvature occurs after repeated peribulbar injection of triamcinolone acetate in patients with TED. The amount of this change in corneal curvature is sufficient to change the posttreatment refraction of the eye.

Topography-Guided Femto-LASIK in Virgin Eyes: Treating Manifest versus Measured Astigmatism.

PurposeTo assess the stability, safety, predictability, and efficacy of topography-guided myopic Femto-LASIK with two different treatment protocols.SettingEbsar Eye center, Benha, Qalyopia, Egypt.DesignSingle-center, retrospective, COHORT control study.MethodsA total of 330 eyes enrolled in the study in group A and 322 eyes enrolled in group B underwent uncomplicated primary bilateral topography-guided Femto-LASIK. Group A was treated with the subjective clinical refraction; however, group B was treated with the modified refraction according to ALCON protocol.ResultsThe mean preoperative refractive spherical equivalent (MRSE) was −4.85±1.90D and −5.0±1.93D in group A and B, respectively (P = 0.86), and a cylinder of −0.95±0.80 D and −0.92±0.81D, respectively. At the 12 months’ postoperatively, the residual manifest SE within ± 0.5D was achieved by 82.86% of eyes in group A compared to 83.93% in group B. Of eyes, 92.06% had ≤0.5 astigmatism dioptre, while 100% of eyes had ≤1.0 astigmatism dioptre in group A (315 eyes); however, 91.80% of eyes had ≤0.5 astigmatism dioptre, while 100% of eyes had ≤1.0 astigmatism dioptre in group B.ConclusionTopographic modification of the magnitude and axis of astigmatism treated using ALCON protocol when different from the clinical refraction may offer good refractive outcomes when we apply the Alcon precalculation considerations.

Repeatability and reproducibility of manifest refraction.

To evaluate the intraexaminer repeatability and the interobserver reproducibility of manifest refraction. Tertiary referral center. Retrospective study. Patients attending at least 2 preoperative refractions before undergoing subsequent refractive surgery were included. All manifest refractions were performed by 1 of 4 experienced optometrists using an automated phoropter according to a standard protocol. The first manifest refraction was performed after obtaining automated refraction and measuring the spectacles of the patient. The second refraction was typically refined from the first also considering wavefront refraction and tomography/topography. The latest 2 manifest refractions of 1000 eyes obtained at 2 separate visits showed a mean pairwise absolute difference of 0.16 ± 0.19 diopter (D) (range 0 to 1.38 D) in spherical equivalent (SE). This SD was better than 0.25 D (the minimum measurement increment of refraction itself). The 95% limit of agreement (LoA) was within 0.50 D for sphere, cylinder, and SE. The SD of the astigmatism axis was approximately 10 degrees, and the 95% LoA was within 22 degrees (the difference in axis decreasing significantly with the measured cylinder magnitude). The SD for corrected distance visual acuity (CDVA) was half a Snellen line and the 95% LoA was within 1.5 lines (with increasing deviation with worse vision). There were no clinically meaningful differences in reproducibility (2 optometrists) compared with repeatability (same optometrist) in sphere, axis, and CDVA. Reproducibility was 0.16 D irrespective whether refractions were performed by 1 or 2 different optometrists. Obtaining multiple refractions preoperatively might increase the predictability of surgery and decrease the enhancement rate.

Effect of Trabeculectomy on Corneal Astigmatism: A Hospital Based Study

Purpose: To find out the effect of trabeculectomy on corneal astigmatism among glaucoma patients.&#x0D; Study Design: Interventional case series.&#x0D; Place and Duration of Study: Al-Shifa Trust hospital, from August 2015 to February 2016.&#x0D; Methods: Thirty patients of glaucoma who were advised trabeculectomy were included in the study. Pre and post trabeculectomy data was collected by a structured clinical proforma. Snellen chart was used to measure visual acuity. Autorefracto-keratometer was used to find K-readings, corneal astigmatism and its axis. Data was entered in SPSS version 22. Descriptive analysis was done to report frequencies, percentages for qualitative variables and mean and SD for continuous variables. Paired sample t test was applied after the preliminary analysis to compare the corneal astigmatism pre and post trabeculectomy.&#x0D; Results: Out of 30 patients, majority (76%) were males. There was no statistically significant change found in visual acuity pre and post trabeculectomy (p-value &gt; 0.05). There was statistically significant difference of K1 (Horizontal) and K2 (Vertical) readings pre and post trabeculectomy (p &lt; 0.05). There was a statistically significant increase in overall corneal astigmatic power (p &lt; 0.05). Approximately 1.20D of astigmatism developed after trabeculectomy. There was no statistically significant difference between pre (94.0 ± 49.6) and post-operative corneal axis of astigmatism (87.6 ± 64.1).&#x0D; Conclusion: Trabeculectomy results in a significant change of corneal curvature in both meridians. This causes a change in post-operative visual acuity which in turn may adversely affect the compliance of patient towards surgical treatment. Patient should be informed and counselled about the possible visual outcomes after the trabeculectomy to preclude any distress that may occur following surgery.&#x0D; Key Words: Glaucoma, Trabeculectomy, Corneal Astigmatism, Visual acuity, Keratometry.

Evaluation of posterior and total corneal astigmatism with colour-LED topography.

To characterise the posterior and total corneal astigmatism using colour point-source light-emitting diodes (LED) topography. In a prospective case series 400 eyes from 400 patients were evaluated by colour-LED topography. Only eyes with normal topographies were considered. The following parameters were studied: magnitude and distribution of SimK and posterior corneal astigmatism, correlation between SimK and posterior corneal astigmatism, and differences in magnitude and axis between total and anterior corneal astigmatism. The mean SimK corneal astigmatism was 1.21 ± 0.94 D. The mean posterior corneal astigmatism was 0.37 ± 0.24 D. Posterior astigmatism was vertically oriented in 68% of eyes. Twenty-two percent of eyes showed a posterior corneal astigmatism ≥ 0.50 D. The correlation coefficients between SimK and posterior corneal astigmatism were: r2 = 0.066; p = 0.371 in WTR eyes, r2 = 0.112; p = 0.173 in ATR eyes and r2 = -0.019; p = 0.879 in oblique eyes. A difference between SimK and total corneal astigmatism ≥ 0.50 D was found in 7% of eyes. A difference in axis between SimK and total corneal astigmatism ≥ 10° was found in 24% of eyes. The percentage of eyes with posterior corneal astigmatism ≥ 0.50 D and the differences between anterior and total corneal astigmatism were higher than those previously reported in the literature. Therefore, this study supports the consideration of total corneal astigmatism magnitude and axis is mandatory for a precise surgical correction of astigmatism.

유발된 난시축 오차에 따른 시기능 변화 연구

유발된 난시축 오차에 따른 시기능 변화 연구

Prevalence and Age-Related Changes of Corneal Astigmatism in Patients Undergoing Cataract Surgery in Northern China.

Purpose To examine the magnitude, orientation, and age-related changes of corneal astigmatism of the eyes before cataract surgery. Setting. Hebei Eye Hospital, Hebei, China. Design A clinical-based retrospective study. Results The study consisted of 5662 eyes of 5662 consecutive cataract surgery patients with a mean age of 68.26 ± 10.39 (mean ± standard deviation (SD)) years (range 40 to 97 years), and 59.86% of the patients were women. Mean corneal astigmatism was 0.98 ± 0.76 diopter (D) (range 0.00–9.61 D). Corneal astigmatism of 0.50–0.99 D was the most common range of values (30.08%), followed by 1.00–1.49 D (22.15%), ≤0.50 D (21.21%), and 1.50–1.99 D (10.28%). There was a strong U-shaped relation between corneal astigmatism and age (p for nonlinearity <.01). With the increase of age, the astigmatism axis gradually changes from with-the-rule (WTR) to against-the-rule (ATR). Moreover, in young patients with age below 65 years, WTR astigmatism was negatively correlated with age, while ATR was positively correlated with age (r = −0.11, p=.001; r = 0.10, p=.010, respectively). However, in the old patients with age above and equal to 65 years, all types of astigmatism were positively correlated with age. Conclusion This study may provide valuable and practical information to surgeons when selecting the appropriate surgical method and toric intraocular lens (IOLs).

Method of the Cyclotorsion Error Compensation for Myopic Astigmatism during SMILE Surgery

Purpose: to develop an effective and safe method of cyclotorsion compensation, to improve the clinical and functional results of the of myopic astigmatism correction with SMILE surgery.Patients and methods: Two equivalent groups of 30 people (30 eyes) were formed with cyclotorsion from ±5 degrees («Standard» and «Verion»). The correction for cyclotorsion was carried out only in the «Verion» group. Before the laser-refraction surgery, all eyes were examined using «Verion» image guided system (Alcon, USA) to determine cyclotorsion. In the «Verion» group, the obtained cyclotorsion data was used to aligement the astigmatism axis by Introducing into the «Visumax» femtolaser system. Further, the operation was carried out according to the standard protocol. At 3 months after SMILE surgery, all patients were examined by a UDVA, CDVA, objective refraction. Furthermore, efficiency and safety, as well as vector analysis of corneal astigmatism according to Alpins were calculated indices at 3 months after surgery.Results: The mean and standard deviation of cyclotorsion of the «Standard» and «Verion» groups was 6.16 ± 1.31 D and 6.30 ± 1.36 degrees, respectively (p &gt; 0.05). The increasement of 1 or more UDVA lines was noted at 20 % and 7 %, respectively after 3 months in the «Standard» and «Verion» groups. The safety index (postoperative UDVA / preoperative UDVA) in both groups was not statistically significantly different (p &gt; 0.05). The predictability of the spherical equivalent within ±0.5 D relative to the target refraction (emmetropia) in the «Standard» and «Verion» groups was 70 % and 100 %, respectively. The predictability of the cylindrical component of refraction within ±0.5 D relative to the target refraction (emmetropia) was 40 % and 90 % for the «Standard» and «Verion» groups, respectively (p &lt; 0.05). Difference vector was 1.01 ± 0.59 D in the group «Standard» and 0.64 ± 0.33 D in the «Verion» group (p &lt; 0.05). Correction index was 0.80 ± 0.43 in the «Standard» group and 0.99 ± 0.04 in the «Verion» group (p &lt; 0.05).Conclusions: Сyclotorsion compensation using the «Verion» image guided system is a safe method. It improves the efficiency and predictability of correction myopic astigmatism in patient undergoing to SMILE surgery. This method recommended for patients with cyclotorsion from ±5 degrees and myopic astigmatism from –0.75 D.

Long-term Vector Outcomes of SMILE in Correcting Moderate to High With-the-Rule Astigmatism Under Astigmatism Axis Marked Condition.

To evaluate the vector outcomes of small incision lenticule extraction (SMILE) in correcting moderate to high myopic astigmatism under astigmatic axis marked condition. In a prospective, longitudinal, interventional study, 71 eyes (71 patients) that had with-the-rule preoperative cylinder refraction exceeding 1.50 diopters (D) were corrected with the VisuMax femtosecond laser (Carl Zeiss Meditec AG) at Zhongshan Ophthalmic Center. Refractive outcomes and astigmatic vector were evaluated preoperatively and at 1, 3, 6, and 30 months postoperatively. At 30 months postoperatively, the efficacy and safety indexes were 1.04 ± 0.18 and 1.15 ± 0.17, respectively. The magnitude of the surgically induced astigmatism (SIA) (2.13 ± 0.71 D at 1 month [P1m-pre = .018], 2.12 ± 0.72 D at 3 months [P3m-pre = .006], 2.13 ± 0.69 D at 6 months [P6m-pre = .010], and 2.19 ± 0.72 D at 30 months [P30m-pre < .001]) was slightly higher than that of the target induced astigmatism (TIA) (2.07 ± 0.69 D). Only the y-coordinate of the SIA vector had a significant overcorrection compared to that of the TIA vector (P1m-pre = .033, P3m-pre = .011, P6m-pre = .012, P30m-pre < .001). The corrected index (CI = |SIA|/|TIA|) varied from 1.03 ± 0.07 at 1 month to 1.06 ± 0.10 at 30 months, which was higher when correcting moderate astigmatism than when correcting high astigmatism (P = .041) at 30 months postoperatively. SMILE had long-term safety, efficacy, predictability, and stability when correcting moderate to high myopic astigmatism under astigmatism axis marked condition. Meanwhile, a cylinder overcorrection was observed due to the overcorrection of y-coordinate astigmatic power, which implied that the vector adjustment of the cylinder refraction nomogram should be considered. [J Refract Surg. 2020;36(9):585-591.].

Intrastromal corneal ring segment implantation in paracentral keratoconus with perpendicular topographic astigmatism and comatic axis.

To evaluate the outcomes of implanting intrastromal corneal ring segment (ICRS) using two different strategies in a specific paracentral keratoconus phenotype. Eighty-nine eyes with paracentral keratoconus with perpendicular topographic astigmatism and comatic axes were evaluated before and after implanting a 150° arc-length ICRS. Patients were divided into two groups according to the axis where the ICRS was implanted: Group I: comatic axis and Group II: flat topographic axis. Uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refractive errors, and root mean square (RMS) for coma-like aberration were recorded. The postoperative follow-up was 1 year. Mean UDVA (logMAR) changed from 0.49 ± 0.37 preoperatively to 0.30 ± 0.32 6 months afterwards (p < 0.001) in the group I and from 0.53 ± 0.34 to 0.37 ± 0.35 (p < 0.001), in the group II. Mean CDVA in group I changed from 0.11 ± 0.18 preoperatively to 0.06 ± 0.14 6 months after surgery (p < 0.001). In group II the improvement did not reach statistical significance (from 0.09 ± 0.10 to 0.07 ± 0.09; p = 0.06). No eyes lost lines of CDVA in group I. Eight eyes (15.7%) lost lines of CDVA in group II. The spherical equivalent decreased after surgery in both groups (p < 0.001). The RMS for corneal coma-like aberration only decreased in the group I (p < 0.001). Both strategies provided safe and effective visual and refractive outcomes in the specific keratoconus phenotype analyzed. The orthopedic strategy provided better visual outcomes than the refractive one.

Measurement of refractive, wavefront, topographic, and keratometric changes attributable to epithelial removal in keratoconus

ObjectiveThe corneal epithelium is able to mask topographic and keratometric abnormalities of the underlying Bowman layer in keratoconus, but its contribution to refractive and wavefront parameters has not yet been studied. This study compared the refractive and aberrometric features of the corneal epithelium and Bowman layer in eyes with keratoconus before and after epithelial debridement. MethodsCorneal refractive and wavefront variables were measured in patients with keratoconus undergoing corneal crosslinking—immediately before and after epithelial debridement using a third-generation combined corneal topographer, autorefractor, and aberrometer. ResultsAfter epithelial debridement, there were significant changes in spherical equivalent (−1.37 D; p < 0.01) and asphericity (−0.64; p = 0.03). The mean difference in the magnitude of epithelium-induced astigmatism in the 3rd and 5th central millimeter rings was 0.44 ± 3.20 D × 8 and 0.43 ± 2.75 D × 21 (positive cylinder), respectively. Corneal astigmatism axis shifted in the against-the-rule orientation after epithelial debridement. There were no significant changes in any corneal higher-order aberration parameter after epithelial debridement (p > 0.05). ConclusionsIn eyes with keratoconus, epithelial debridement increased the magnitude of anterior corneal prolateness and tended to increase astigmatism and shift its axis toward the against-the-rule orientation. This study supports the notion that the corneal epithelium smooths underlying Bowman layer irregularity in keratoconus.

Astigmatic Defocus Leads to Short-Term Changes in Human Choroidal Thickness.

PurposeTo examine the choroidal thickness (ChT) response to short-term with-the-rule (WTR) and against-the-rule (ATR) simple myopic astigmatic defocus, with the response to spherical myopic defocus and clear vision used as control conditions.MethodsThe left eye of 18 healthy adults aged 28 ± 6 years was exposed to clear vision, +3 D spherical myopic defocus, +3 D × 180 WTR, or +3 D × 90 ATR astigmatic defocus for 60 minutes, over four randomly ordered visits, while their right eye was optimally corrected. The macular ChT was measured with optical coherence tomography along the vertical and horizontal meridians before and after 20, 40, and 60 minutes of defocus.ResultsAfter 60 minutes of defocus, ChT increased by +8 ± 5 µm (P < 0.001) with spherical myopic defocus, but varied with simple myopic astigmatic defocus, depending on the axis of astigmatism (P < 0.001), increasing by +5 ± 6 µm (P = 0.037) with WTR and decreasing by −4 ± 5 µm (P = 0.011) with ATR astigmatic defocus. These changes were similar across the vertical and horizontal meridians (P = 0.22). The ChT changes were greater than the change during the clear vision control condition (−1 ± 4 µm) for WTR (+5 ± 5 µm, P = 0.002) but not ATR (−4 ± 6 µm, P = 0.09) astigmatic defocus.ConclusionsThese results provide insights into the human ChT response to short-term astigmatic defocus and highlight a potential difference in the myopiagenic signal associated with the orientation of astigmatic blur.

The Impact of Changes in Corneal Back Surface Astigmatism on the Residual Astigmatic Refractive Error following Routine Uncomplicated Phacoemulsification.

Purpose To determine the significance of any association between intersessional changes in ocular residual astigmatism (RA) and astigmatism at corneal front (FSA) and back (BSA) surfaces following uneventful routine phacoemulsification. Methods Astigmatism was evaluated by autorefractometry and subjective refraction and at both the corneal surfaces with Orbscan II™ (Bausch & Lomb) over central 3 mm and 5 mm optical zones at 1, 2, and 3 months after routine phacoemulsification in 103 patients implanted with monofocal nontoric intraocular lenses (IOLs, one eye/patient). Data were subjected to vector analysis to determine the actual change (Δ) in astigmatism (power and axis) for the refractive and Orbscan II findings. Results The number of cases that attended where ΔRA was ≥0.50 DC between 1 and 2 months was 52 by autorefractometry and 36 by subjective refraction and between 2 and 3 months was 24 by autorefractometry and 19 by subjective refraction. Vector analysis revealed significant correlations between ΔFSA and ΔRA for data obtained by autorefractometry but not by subjective refraction. At all times, ΔBSA was greater than ΔFSA (p < 0.01). Key findings for ΔBSA values over the central 3 mm zone were between (A) the sine of the axis of ΔRA (y) and sine of the axis of ΔBSA (x) for the data obtained by autorefractometry (between 1 and 2 months, y = 0.749 − 0.303x, r = 0.299, n = 52, p=0.031) and subjective refraction (between 2 and 3 months, y = 0.6614 − 0.4755x, r = 0.474, n = 19, p=0.040) and (B) ΔRA (y) and ΔBSA (x) powers between 2 and 3 months postoperatively for the data obtained by autorefractometry (ΔRA = 0.118 ΔBSA + 0.681 r = 0.467, n = 24, p=0.021) and subjective refraction (ΔRA = 0.072 ΔBSA + 0.545 r = 0.510, n = 19, p=0.026). Conclusion Changes in the ocular residual refractive astigmatic error after implanting a monofocal nontoric IOL are associated with changes in astigmatism at the back surface of the cornea within the central optical zone.