Total Astigmatism Research Articles

Effect of Pterygium Removal Combined with Conjunctival Autograft on Corneal Parameters in Swept-Source Imaging.

Background: Both pterygium ingrowth and excision determine alterations in corneal topography. The aim of this study was to evaluate the influence of pterygium removal combined with conjunctival autografts in addition to the use of human fibrin tissue glue on changes in corneal parameters as measured by 3-D swept-source anterior segment optical coherence tomography (AS-OCT) imaging. Methods: Sixteen eyes (16 patients) with pterygium that qualified for surgical treatment were enrolled in this study. Eye examination, slit lamp, and 3-D AS-OCT (CASIA 2) assessment were performed before the surgery and 7 days, 1 month, and 6 months after pterygium excision. Topographic parameters of both anterior and posterior surfaces of the cornea were analysed at each follow-up visit. Results: The gradual decrease in total astigmatism power from preoperative median 2.75 (6.15) D to 1.2 (1.1) D at 6-month follow-up (p = 0.034) was noted from the day 7 visit. Values were strongly influenced by variations of anterior cornea astigmatism. In contrast, a gradual total HOA reduction at the 1-month (from median 0.79 (1.3) D to 0.44 (0.27) D; p = 0.038) and at 6-month visits (0.25 (0.09); p = 0.001) was observed. Similarly, values were strongly influenced by variations of the anterior. Additionally, total average keratometry values increased from preoperative 44.05 (2.25) D to 44.6 (1.9) (p = 0.043) 1 month after the surgery. Conclusions: Significant steepening of the anterior cornea and a reduction in both astigmatism and HOA were observed after pterygium excision. The anterior corneal surface was an essential component of the total postoperative corneal topography values. Three-dimensional swept-source AS-OCT imaging seems to be a valuable tool for monitoring both the progression of the disease and postoperative effects in pterygium eyes.

Comparison of astigmatism between glued and sutured scleral-fixated intraocular lens

Background Posterior chamber intraocular lens implantation in the bag is the preferred mode of correcting aphakia. But, in certain circumstances, this is not possible, thereby requiring modalities of secondary fixation of intraocular lens (IOL).Purpose The aim of this study was to compare the postoperative astigmatism till six months after surgery between the sutured scleral-fixated IOL and the glued scleral-fixated IOL.Patients and methods This is a single-center, prospective, observational, open-label study comparing the postoperative outcome (till 6 months), including astigmatism and best-corrected visual acuity (BCVA), of sutured scleral-fixated intraocular lens (SFIOL) (Group 1) and glued SFIOL (Group 2). There were 25 patients in each group. Patients were followed up on day 1, first week, first, second, third, and sixth month postoperatively. During each postoperative visit, slit-lamp biomicroscopy was performed to evaluate the status of the cornea, anterior chamber, IOL, and position of haptics. Uncorrected visual acuity, BCVA, refraction, and keratometry values (corneal astigmatism) were noted. Cylindrical refraction denoted total astigmatism. The IOL astigmatism was derived by subtracting the corneal astigmatism from the total astigmatism.Results The difference in corneal astigmatism between the two groups was statistically significant at 1, 3, and 6 months postoperatively (P=0.004, 0.002, and 0.012, respectively). The final values at 6 months were 3.00±1.68 diopters (D) in the sutured SFIOL group and 2.08±0.56 D in the glued SFIOL group. The glued SFIOL group required less cylindrical correction till 6 months of follow-up. The BCVA, 6 months postoperatively, was 0.36±0.19 in Group 1 compared with 0.32±0.17 in Group 2, with no statistically significant difference (P=0.404).Conclusion Both techniques proved to be good options for the implantation of SFIOL, but glued SFIOL was better as it led to less astigmatism and hence the need for less spectacle correction.

The short term visual, refractive and Topographic outcome of Corneal Collagen Crosslinking in Keratoconus

Background: Keratoconus is a condition characterized by biomechanical instability of cornea presenting in a progressive asymmetry and bilateral way. Corneal collagen cross-linking with riboflavin and UVA is a technique that has influenced the treatment of Keratoconus by arresting the progression. Aims and Objectives: The aim of the study was to assess the short-term efficacy and safety of collagen cross-linking in Keratoconus. Materials and Methods: This prospective, nonrandomized, interventional case study was conducted at Aravind Eye hospital and PGI, Puducherry from June 2012 to April 2013. Statistical analysis was done using repeated measures ANOVA and Bonferonn’s using IBM SPSS Inc. 20.Version. Results: A total of 30 patients were enrolled in this study and standard cross linking procedure was done. It was found that UCVA, BSCVA both improved about 40%. Spherical Equivalent reduced by 0.7 D, cylinder reduced by 0.8 D and total astigmatism decreased by about 0.4 D. Steepest K value reduced by 2 D, Irregularity and astigmatism at 3 and 5 mm also changed significantly (P<0.05). Conclusion: Collagen cross-linking arrests the progression of Keratoconus. It seems to improve the UCVA and BCVA and it is a safe and effective procedure.

Longitudinal change in components of astigmatism and its association with axial length-corneal radius ratio in Chinese young children: the Nanjing Eye Study.

To assess the longitudinal change in components of astigmatism from age 4 to 7years and its association with axial length-corneal radius ratio (AL/CR). Children born between September 2011 and August 2012 in Yuhuatai District of Nanjing were invited to participate in the Nanjing Eye Study for a comprehensive eye examination annually since 2015. The data presented in this paper were obtained in 2016, 2017, and 2019. At each study encounter, noncycloplegic autorefraction and ocular biometric parameters were measured. Changes of total astigmatism (TA), corneal astigmatism (CA), anterior corneal astigmatism (ACA), residual astigmatism (RA), and internal astigmatism (IA) were analyzed in clinical notation (Cyl) and vector notation (J0, J45). Nine hundred fifty-four children (mean ± standard deviation of baseline age: 4.63 ± 0.29years, 53.7% boys) had complete data and were included in this study. Mean slopes of longitudinal changes in Cyl notation were significantly negative for TA, CA, and ACA, but positive for IA. TA, CA, ACA, and RA of J0 notation had a shift toward increasing with-the-rule (WTR) astigmatism and/or decreasing against-the-rule (ATR) astigmatism. TA of J45 notation showed an increase in astigmatism at axis 135° and/or a decrease in astigmatism at axis 45°, while CA and ACA of J45 notation showed an opposite change. Longitudinal changes in ACA and IA were negatively correlated in J0 notation, but not in J45 notation. Based on compensation factor (CF, defined as the minus ratio of IA and ACA), the compensation proportions for J0 in varying degrees (CF: 0.1-2) in 2016, 2017, and 2019 were 91.3%, 93.5%, and 90.0%, respectively, while these for J45 were 74.9%, 76.5%, and 34.6%, respectively. Higher AL/CR increase was associated with less decrease or more increase in CA and ACA of Cyl notation, and a shift toward increasing WTR and/or decreasing ATR in these of J0 notation. The compensatory role of IA was persistent and prominent from 4 to 7years old for J0 notation in Chinese young children. The progression of AL/CR was correlated with astigmatism originated from the cornea.

Pterygium surgery by double-sliding flaps procedure

Purpose:This study aimed to evaluate the surgical outcomes of pterygial excision for primary and recurrent pterygia by a single method of pterygia excision combined with two conjunctival flaps.Methods:This retrospective study divided 193 cases of pterygium into the primary (140 cases) and recurrent (53 cases) pterygium groups. Following double-sliding conjunctival transposition flap operation and surgical excision of the pterygium, the success and recurrence rates of pterygial surgery were assessed based on visual acuity and corneal and total astigmatism during follow-up at least 6 months.Results:Both primary and recurrent pterygium groups showed significant improvements in visual acuity and astigmatism (corneal and total) between before and after this procedure. Total astigmatism and success rate of primary pterygium were significantly better than those for recurrent pterygium. Two cases (1.4%) of primary pterygium and four cases (7.5%) of recurrent pterygium developed recurrence, corresponding to a rate of 3.1% (6/193 cases). The success rates significantly make a difference between primary and recurrent groups but did not differ significantly between the first recurrent and over twice recurrent pterygium. However, visual acuity, cornea, and total astigmatism improved significantly after surgery in first recurrent group but not in over twice recurrent group.Conclusion:The double-sliding conjunctival flaps surgery appeared to be a useful method, with a better success rate and lower pterygial recurrence in pterygium surgery. Especially, when pterygium is larger or recurrent type, this technique can be easily covered the bare sclera, as compared to any transposition conjunctival flap operation.

Changes in Corneal Parameters after DMEK Surgery: A Swept-Source Imaging Analysis at 12-Month Follow-Up Time.

Purpose To assess the time course changes in corneal topographic parameters during the one-year follow-up after Descemet membrane endothelial keratoplasty (DMEK) surgery. Materials and Methods Twenty-one patients (24 eyes) who underwent DMEK surgery were evaluated. Best corrected visual acuity (BCVA), endothelial cell count (ECC), central corneal thickness (CCT), mean keratometry (MK), mean astigmatism (MA), astigmatism asymmetry (AA), and higher-order aberration (HOA) were assessed at baseline and 1, 3, 6 and 12 months after the surgery using CASIA2 anterior segment swept-source OCT (Tomey, Japan). Results In patients who underwent DMEK surgery, BCVA improved gradually at the subsequent visits during the 12-month follow-up. A significant reduction in ECC and CCT at the 1st month was noted, which remained stable until the 6th month postoperatively. Anterior and total MK values remained unchanged, whereas changes in posterior keratometry were noticeable until the 6th month after surgery. A significant reduction in the anterior, posterior, and total astigmatism magnitude as well as astigmatism asymmetry was observed during the first 6 months after surgery. A gradual anterior, posterior, and total HOA decrease was documented until the 12th month after surgery. Negative correlations between baseline values of CCT, MK, MA, AA, and HOA and postoperative variations in those parameters at consecutive follow-up time points were observed. Accordingly, negative correlations between baseline CCT and postoperative changes in corneal topographic parameters after surgery were found. Conclusion The stabilization of most corneal topographic parameters takes place within 6 months after the procedure, whereas HOA reduction and BCVA improvement gradually occur during the first year after surgery. Preoperative values of corneal topographic parameters strongly determine their changes detected after DMEK surgery, which may suggest that early therapeutic intervention results in better visual outcomes.

Comparison of Preoperative Measurements with Intraoperative Aberrometry in Predicting Need for Correction in Eyes with Low Astigmatism Undergoing Cataract Surgery.

PurposeTo determine whether intraoperative aberrometry during cataract surgery measures higher levels of absolute astigmatism than preoperative biometry readings and which method yields a lower, final level of astigmatism if the two do not agree.Patients and MethodsRetrospective record review of all patients who underwent uncomplicated cataract surgery from February 2015 to May 2019 with planned intraoperative aberrometry. Data analysis included preoperative keratometry, total astigmatism as measured by intraoperative aberrometry, intraocular lens model and power used, and postoperative manifest refraction ≥1 month after surgery. The primary outcome measure was the proportion of patients requiring astigmatism correction (≥0.5 D) when measured by preoperative keratometry vs intraoperative aberrometry. Secondary outcomes included postoperative residual astigmatism, where adjusted preoperative astigmatism fell below the 0.5 D threshold for treatment but the intraoperative measurement was ≥0.5 D or ≥1.0 D.ResultsA total of 451 patient records were evaluated. Intraoperative aberrometry measured statistically higher levels of mean astigmatism than keratometry (0.86 D vs 0.79 D, respectively; P < 0.0001) and significantly greater astigmatism among patients with 0.5–1.5 D of adjusted preoperative astigmatism (P < 0.0001). Significantly more patients qualified for with-the-rule astigmatism correction when measured by intraoperative aberrometry (n=339; 75%) than by preoperative keratometry alone (n=314; 70%); P < 0.03. This difference did not hold for against-the-rule or oblique astigmatism. For patients whose preoperative biometry astigmatism differed from intraoperative biometry, final postoperative astigmatism was lower when corrected if the adjusted preoperative and intraoperative measurements had a vector difference of <0.5 D, but there was no additional benefit in final astigmatism reduction when the vector difference was ≥0.5 D.ConclusionUsing intraoperative biometry readings can produce lower postoperative astigmatism than using preoperative biometry readings, but caution should be used when interpreting intraoperative readings that disagree with preoperative measurements with a vector magnitude of >0.5 D.

Refractive outcome of trocar-assisted sutureless scleral fixation with 3-piece intraocular lenses.

Intraocular lens (IOL) implantation with a trocar-assisted sutureless scleral fixation technique is a relatively new IOL implantation approach for aphakic eyes. During this surgery, the intrascleral position of the haptics can change the location of the IOL optic and may alter the refractive outcome. This study aimed to evaluate the refractive outcome of this surgery. The files of 22 patients who had undergone IOL implantation with the trocar-assisted sutureless scleral fixation technique were retrospectively reviewed, and the patients were invited for final examination. IOL power was calculated with optical biometry (Lenstar LS900). IOL power calculations were performed according to formulas designed for in-the-bag IOL implantation. The final refractive error was determined with an autorefractometer (Topcon KR-1/RM-1). This study included 14 patients (8 male, 6 female, mean age: 62.7 ± 18.7). There were no significant differences between the preoperative and postoperative corneal astigmatism values (p = 0.16). There were also no significant differences between the postoperative corneal and total astigmatism values (p = 0.44), confirming the absence of significant IOL tilt. The difference between the implanted IOLs and the calculated IOL power for emmetropia was 0.09 D ± 0.49 D (p = 0.52). Although emmetropia was targeted, the refractive outcome shifted to hyperopia (+ 0.85 D ± 1.15 D) and was significantly different from the refractive status calculated with optical biometry (p = 0.034). The intrascleral fixation of IOLs results in increased posterior positioning of the IOL optic and can induce approximately 0.85 D of hyperopia if proper adjustments are not performed during IOL power calculations.

Ocular surface topographic evaluation in patients of astigmatism in normal and pathologic eyes

Keratometry is the measurement of anterior surface of corneal curvature in its steepest and flattest axis by various methods. There are many advances in measurement of keratometric values. Corneal topography and Modern videokeratoscopes provide an accurate representation of the anterior corneal surface to allow assessment of corneal irregularities in keratoconus, pellucid marginal degeneration, preoperative cataract workup - IOL calculation/TORIC lens implantation, refractive surgery preoperative assessment and post-op evaluation, evaluating pathologies like coneal dystrophies, scars, pterigium, recurrent erosions and contact lens fitting and evaluating the corneal contribution to optical aberrations of the whole eye Astigmatism (more than 0.5 diopters) is a commonly encountered refractive error, accounting for about aprx. 13-40 per cent of the refractive errors of the human eye according to various studies. In our study, 200 eyes of patients were studied over period of 2 year, with autorefractometer which measures total astigmatism (corneal and lenticular) and Bausch and Lomb manual keratometer and oculus topographer which measures anterior corneal astigmatism and results were compared. In our study 92.5% of eyes had regular astigmatism while 7.5% of eyes had irregular astigmatism. Various causes of corneal astigmatism were pterygium, keratoconus, PMCD, corneal degeneration, corneal opacity in that order. No significant clinical cause was found in 74.5% of eyes. Maximum repeatability was found with oculus topographer followed by autorefractometer and Bausch and Lomb manual keratometer.

The biometric parameters of aniso-astigmatism and its risk factor in Chinese preschool children: the Nanjing eye study

BackgroundsAniso-astigmatism may hinder normal visual development in preschool children. Knowing its prevalence, biometric parameters and risk factors is fundamental to children eye care. The purpose of this study was to determine the biometric components of aniso-astigmatism and associated maternal risk factors in Chinese preschool children.MethodsIn the population-based, prospective cohort Nanjing Eye Study, children were measured for noncycloplegic refractive error using an autorefractor and for biometric parameters using an optical low-coherent reflectometry. The difference of total astigmatism (TA) between both eyes was calculated using cylinder power (non-vectorial aniso-TA was defined as ≥1.00 Dioptre Cylinder [DC] between both eyes) and by vector analysis (vectorial aniso-TA was defined as a difference of ≥0.5 in J0 or J45 between both eyes which is equivalent to 1.00 DC). The prevalence of aniso-TA was presented. Interocular biometric parameters were compared between with vs. without aniso-astigmatism group. In addition, risk factors were determined using multivariate logistic regression model.ResultsOf 1131 children (66.90 ± 3.38 months, 53.31% male), the prevalence of non-vectorial aniso-TA was 1.95% (95% Confidence Interval (CI) = 1.14–2.75%), while the prevalence of vectorial aniso-TA was twice as common as non-vectorial aniso-TA, neither varying with sex or age. With aniso-TA eyes were more asymmetric in axial length and corneal curvature radius than without aniso-TA eyes. In multivariate logistic regression model, 5-min Apgar score less than 7 was significantly associated with higher risk of aniso-TA (vectorial aniso-TA: Odds Ratio (OR) = 6.42, 95%CI = 2.63–15.69, P < 0.001; non-vectorial aniso-TA: OR = 4.99, 95%CI = 1.41–17.68, P = 0.01). Being twin or triple was significantly associated with higher risk of vectorial aniso-CA (OR = 2.43, 95%CI = 1.05–5.60, P = 0.04). Pre-term delivery (OR = 2.60, 95%CI = 1.09–6.15, P = 0.03) and post-term delivery (OR = 3.61, 95%CI = 1.31–9.96, P = 0.01) were significantly associated with higher risk of vectorial aniso-CA.ConclusionsBoth corneal curvature radius and axial length asymmetry were correlated with aniso-TA. Children with 5-min Apgar score < 7 were more likely to have aniso-TA, while twin or triple, pre-term or post-term delivery were more likely to have vectorial aniso-CA.

The influence of routine uncomplicated phacoemulsification on the orthogonality of the cornea.

Purpose:The aim of this study was to determine the effect of routine uncomplicated phacoemulsification on the orthogonal distribution of mass within the central optical zone of the cornea.Methods:Astigmatism at both corneal surfaces was evaluated using Orbscan II (Bausch &and Lomb) before and up to 3 months after routine phacoemulsification (one eye/patient). The data were subjected to vector analysis to estimate the pre-and postoperative total astigmatism of the cornea (TCA).Results:Reporting the chief findings in minus cylinder (diopters, DC) over the central 3 mm (A) and 5 mm (B) optical zones. Mean TCA powers (±sd) at pre- and 3-months postop were A) –4.45DC (±2.00) and –5.69DC (±2.69), B) –2.91DC (±2.22) and –2.71DC (±1.60). Change in mean power was significant over 3 mm (P < 0.01, n = 49) but not over 5 mm. Inter-zonal differences were significant (P < 0.01). There was a significant linear relationship between the change in TCA power (y = preoperative-postoperative) and TCA at preoperative stage (x) where, A) y = 0.45x + 3.12 (r = 0.336, n = 49, P = 0.018), B) y = x + 2.65 (r = 0.753, n = 49, P = <0.01). Over the central 3 mm zone only, change (preoperative-postoperative) in axis (°) of TCA (y1) was significantly associated with TCA axis at preoperative stage (x1) where y1 = 1.391x1-0.008x12-0.701 (r = 0.635, n = 49, P < 0.01).Conclusion:Changes in TCA power and axis at 3 months postop, determined using Orbscan II, are indicative of orthogonal alterations in the distribution of corneal tissue. Over the central 3 mm zone, the association between y1 and x1 shows that a change in TCA axis is more profound when preoperative axis is near 90° i.e., against-the-rule.

Corneal back surface power – interpreting keratometer readings and what predictions can tell us

The classical Javal's rule allows estimation of refractive cylinder from keratometric astigmatism using scaling for vergence transformation, with an additional half dioptre of cylinder against-the-rule. With increasing popularity of toric intraocular lenses it has been shown that keratometric astigmatism does not fully reflect the entire astigmatism of the phakic or pseudophakic eye.Researchers mostly argue that this mismatch is primarily due to astigmatism of the corneal back surface, and some papers propose correction strategies to consider this mismatch with the keratometric values. In this Technical Note we address this issue using a vector analysis and show the consequences of this correction on the front and back surface as well as total astigmatism of the cornea. As examples we focus on the correction strategies proposed by Abulafia and by Savini, frequently used in clinical practice.The main conclusion is that, since corneal tomographers do not systematically show zero total astigmatism in situations where keratometry measures astigmatism against-the-rule of around 3 dioptres, there may be reasons other than the corneal back surface for this mismatch between keratometry and total astigmatism. A number of possible sources of this mismatch are proposed.

Refractive and Visual Outcomes after Scleral Fixated Intraocular Lens Implantation in Children with Ectopia Lentis

This study was conducted to report the refractive and visual outcome after Scleral Fixated Intraocular Lens (SFIOL) implantation in children with nontraumatic ectopia lentis. Retrospective review of the medical records of 25 eyes of 15 patients who underwent SFIOL implantation in children with non-traumatic ectopia lentis. The mean best corrected visual acuity (BCVA) before SFIOL implantation was 1.07 ± 0.9 logMar units [median: 0.9, Interquartile range (ΙQR): 0.415 to 1.555] which improved to 0.41 ± 0.33 logMar units (median: 0.22, ΙQR: 0.180 to 1.555) at two months postoperative follow up. In phakic group, the mean spherical refraction preoperatively was -12.04 ± 7.82 DS (dioptre sphere) (IQR: +16 to -5.875) and postoperatively was +0.93 ± 2.67DS (IQR: -0.375 to +2). In aphakic group, the mean spherical refraction preoperatively was +12.22 ± 2.05 DS and postoperatively was +1.2 ± 1.9 DS. The mean total astigmatism preoperatively was -6.44 ± 4.95 DC (dioptre cylinder) (median: 6, IQR: -10.50 to +2) and postoperatively was -1.47 ± 0.98 DC (median: -1.5, IQR: -2 to - 0.625 ). The mean IOL induced astigmatism was -1.01 ± 0.95 DC (median -0.75, IQR: -1.33 to - 0.25). The spherical refractive equivalent was within 2 Diopter (D) of the target refraction calculated preoperatively in 20 eyes and in five eyes it was more than 2 D. SFIOL implantation is associated with good visual outcome with a significant improvement in the refractive error. However, a longer follow up is required to assess the change of refraction and the stability of the SFIOL.

Repeatability of whole-cornea measurements using a new swept-source optical coherence tomographer.

The aim of this study was to evaluate the repeatability of several corneal parameters provided by a high-resolution swept-source optical coherence tomographer (SS-OCT). One eye from each of 74 patients was measured five times consequently using the ANTERION SS-OCT. The following corneal parameters were analyzed: average, steep and flat keratometry (K), astigmatism for anterior, posterior and total at 3-mm, average K and astigmatism at 6-mm, anterior and posterior eccentricity, higher-order aberrations (HOA) and spherical aberration (), and anterior and posterior best-fit sphere at 8-mm. The intrasubject standard deviation (Sw), coefficient of variation (CoV), coefficient of repeatability (CoR) and intraclass correlation coefficient (ICC) were calculated for each parameter to assess the repeatability. We have not found statistically significant differences between repeated measurements (p > 0.05). Repeatability was good considering the different metrics used. Sw values were <0.09, varying from 0.035 (posterior average K at 6-mm) to 0.0878 (anterior flat K at 3-mm). CoV values were also low and similar among the different parameters (from 0.08% to 0.21%), except for anterior, posterior and total astigmatism (from 2.25% to 8.46%). Both anterior and posterior eccentricity, and corneal aberrations (HOA and ) CoV values were also high. The CoR values were low for all parameters showing those related to the posterior cornea the lowest values (about 0.01). ICC values were >0.98. The ANTERION SS-OCT showed good repeatability when reconstructed different parameters for the whole cornea. This device produces measurements with high repeatability that could be useful for clinical research.

Modified Intrascleral Fixation for Repositioning the Dislocated Single-Piece, Rigid PMMA Intraocular Lens.

To describe a modified intrascleral fixation technique for repositioning single-piece rigid polymethyl methacrylate intraocular lenses (IOLs). Four patients with dislocated IOLs were enrolled. Surgical modifications included using ≤1-mm scleral incision for haptic externalization, placing the IOL haptic placement in scleral tunnels, and using 8-0 absorbable sutures. Patients were followed up for 6 months with routine ophthalmic examinations, corneal endothelial cell counts, and ultrasound biomicroscopy (UBM). The mean follow-up time was 13.5 ± 5.45 months. The IOL was well centered and the spherical refraction improved (+10.25 ± 2.21 vs. -0.81 ± 1.59 D, P < 0.05), whereas the best-corrected visual acuity (pre 20/43 Snellen, 0.42 ± 0.33 logarithm of the minimum angle of resolution equivalent and post 20/36 Snellen, 0.31 ± 0.22 logarithm of the minimum angle of resolution equivalent; P = 0.235), intraocular pressure (pre 13.8 ± 3.21, post 13.55 ± 5.14 mmHg), corneal endothelium density (pre 2,423.8 ± 279.6/mm 2 , post 2,280.25 ± 350.7/mm 2 ), and total astigmatism (pre -1.94 ± 0.43, post -1.69 ± 0.59 D) remained unchanged. The average horizontal and vertical IOL tilt was 0.33 ± 0.22° and 0.81 ± 0.38°, respectively. Intraocular lens decentration was 0.10 ± 0.03 mm horizontally and 0.13 ± 0.06 mm vertically. The modified intrascleral fixation technique shows encouraging midterm results in patients with dislocated single-piece, rigid polymethyl methacrylate IOLs. Larger samples and longer follow-up are required to confirm the outcomes of this technique.

The effect of glaucoma treatment using high-intensity focused ultrasound on total and corneal astigmatism: a prospective multicentre study.

Ultrasound cycloplasty (UCP) acts through the selective coagulation of the ciliary body using high-intensity focused ultrasound (HIFU) technology. The aim of this study was to investigate whether the application of ultrasound beams targeting the ciliary body using an external probe influences astigmatism. Multicentre, prospective, single-arm, open-label study in adult patients with primary open-angle glaucoma and moderately uncontrolled intraocular pressure (IOP) under glaucoma medication. The primary outcome was induced corneal astigmatism, calculated from topography, and assessed statistically through vector analysis. Secondary outcomes included induced total astigmatism and mean changes from baseline in best-corrected visual acuity (logMAR) and IOP. Subgroup analysis was performed to assess the impact of device centring on corneal and total induced astigmatism. Fifty eyes were enrolled. Mean age was 69.6±11.3years. At 1, 3 and 6months postprocedure, HIFU-induced corneal astigmatism was 0.88D×93°, 0.87D×106° and 1.16D×97°, respectively, while induced total astigmatism was 0.62D×103°, 0.42×106° and 0.39×107°. By the last follow-up, the percentage of patients with <0.50, <1.00, <1.50 and <2.00D of induced corneal versus total astigmatism was 8.3% versus 46%, 29% versus 66%, 62.5% versus 88% and 79% versus 94%. Visual acuity was statistically significantly impaired at 1month, but no difference remained by 3 and 6months postprocedure. Ultrasound cycloplasty procedure is associated with increased corneal astigmatism. However, its impact on total refractive astigmatism is less pronounced.

Risk factors for astigmatic components and internal compensation: the Nanjing Eye Study

PurposeTo determine the risk factors for total astigmatism (TA), anterior corneal astigmatism (ACA), and internal compensation in Chinese preschool children.MethodsIn the population-based Nanjing Eye Study, children were measured for noncycloplegic refractive error and for biometric parameters. Data from questionnaires and measures from right eyes were analyzed for determining risk factors for TA, ACA, and internal compensation from multivariate logistic regression models.ResultsOf 1327 children (66.8 ± 3.4 months, 53.2% male), older age of the child (OR = 0.95 for per month increase; P = 0.03), older paternal age at child birth (OR = 1.04 for per year increase; P = 0.03), paternal astigmatism (OR = 1.89; P = 0.003), maternal astigmatism (OR = 1.73, P = 0.008), and second-hand smoke exposure during pregnancy (OR = 1.64; P = 0.03) were associated with higher risk of TA, while partial breastfeeding (OR = 0.49, P = 0.006) or formula feeding (OR = 0.46, P = 0.003) were associated with lower risk of TA. Larger ratio of axial length to corneal radius (OR = 16.16 for per unit increase; P = 0.001), maternal working during pregnancy (OR = 1.27; P = 0.04), and cesarean delivery (OR = 1.68, P = 0.04) were associated with higher risk of ACA, while formula feeding was associated with lower risk of ACA (OR = 0.57, P = 0.01). Paternal astigmatism (OR = 0.50, P = 0.01) and assisted reproduction (OR = 0.56, P = 0.03) were associated with lower risk of horizontal or vertical internal compensation. More outdoor activity time (OR = 1.15 for per hour increase, P = 0.01) was associated with higher risk of oblique internal compensation while more nighttime sleep on weekends (OR = 0.83 for per hour increase, P = 0.01) was associated with lower risk of oblique internal compensation.ConclusionsOur study confirmed some previously reported risk factors and identified some novel risk factors for astigmatism including formula feeding for lower risk of both ACA and TA, and older paternal age at child birth for higher risk of TA.

The influence of corneal astigmatism on retinal nerve fiber layer thickness and optic nerve head parameter measurements by optical coherence tomography

Abstract Background Astigmatism is a worldwide common ocular disorder. Total astigmatism is mainly driven by corneal astigmatism (CA), which occurs due to an irregular shape of the cornea. In eyes with astigmatism, retinal images can be distorted, and the image size could vary according to the axis of astigmatism assessed with computer-based methodology in astigmatic eyes. Objective to evaluate the influence of corneal astigmatism on the RNFL thickness and ONH parameters obtained by spectral-domain OCT. Patients and Methods 40 patient chosen from outpatient ophthalmology of Ain Shams University Hospitals and Om El¬_Massrein General Hospital and classified in two groups, the study group (high astigmatic patients ≥ 3 diopter) and control group (normal astigmatism&amp;lt; 3 diopter) with no significant change in the age and sex. All cases were free of any ocular diseases with no past history of medical importance (DM, HTN or any neurological diseases), all this cases never had any previous refractive surgery or any retinal lesion. Results In this study all cases had average IOP &amp;gt; 21 mmhg, and randomly selected from the outpatient clinic. The study group had thinner retinal nerve fiber layer in temporal quadrant and larger disc area than the control group. These study support the concept that corneal astigmatism has an effect on retinal nerve fiber layer thickness and optic nerve head parameters. Conclusion In our study, we compare between the OCT pattern of retinal nerve fiber layer thickness (total, superior, nasal and inferior quadrants) and the optic nerve head parameters (cup area, disc area, vertical and horizontal C/D ratio) in the high astigmatic patients (≥ 3 diopter) and normal astigmatism &amp;lt; 3 diopter.

Wavefront aberrations in children with different types of amblyopia

Purpose. To quantify and characterize higher-order aberrations in eyes of children with amblyopia caused by different etiology factors; to evaluate the relationship between the wavefront profile and the effectiveness of the amblyopia treatment. Material and methods. This study involved 26 children (52 eyes) from 3 to 9 years old (average age 6.2±3 years) with different types of amblyopia: unilateral amblyopia due to impaired binocular vision and anisometropia, as well as unilateral or bilateral amblyopia caused by hyperopia. Patients were divided into four groups depending on the effectiveness of pleoptic treatment: 14 children (24 eyes) – with positive treatment results, 8 children (12 eyes) – with refractory amblyopia, 4 pre-treatment newly diagnosed patients (6 eyes) without previous history of optical correction, and 10 non-amblyopic contralateral eyes (control group). All patients had central fixation and didn`t have any severe systemic diseases. Higher-order aberrations were measured with iTrace Visual Function Analyzer (Tracey Technologies, Houston, TX) after instillation of 1% cyclopentolate eyedrops. Results and discussion. Wavefront profiles were significantly different in the studied groups. Total spherical aberrations and astigmatism were significantly higher in group with refractory amblyopia (-0.53±1.19 and 2.25±1.07, p=0.02) compared with all the other groups: the group of patients before pleoptic treatment (-0.17±0.23 and 1.79±1.47), group treated with high efficiency (-0.31±0.81 and 1.04±0.13) and with control group (-0.13±0.17 and 1.38±0.11). Total coma-like aberrations didn`t show statistically significant differences in all studied groups (р=0.06). The level of corneal higher-order aberrations (total, coma, spherical) in all three amblyopic groups was higher than in the control group without amblyopia. Conclusion. We revealed statistically significant differences in the wavefront profiles in children with amblyopia of various etiologies in comparison with the control group, including higher-order aberrations. The data obtained indicate that an amblyopic eye with hyperopia has higher level of spherical aberrations and astigmatism due to higher level of internal HOAs, particularly spherical aberrations and astigmatism, which is typical for patients with unsuccessful treatment. Therefore, that type of aberrations is likely to be the main cause of refractory amblyopia.

Comparison of Standard and Total Keratometry Astigmatism Measured with three Different Technologies

Purpose: To compare the keratometric and total corneal astigmatism measures provided by three different technologies as well as to assess the level of interchangeability among them. Methods: A Prospective, comparative study enrolling 94 eyes from 53 patients (age, 29-77 years) was carried out. All participants were patients with the diagnosis of cataract or patients with a transparent crystalline lens but seeking surgical presbyopia correction. A complete eye examination was performed in all eyes, including corneal analysis with three different devices: IOL-Master 700 (Carl Zeiss Meditec), Cassini (i-Optics), and Pentacam (Oculus Optikgeräte GmbH). Interchangeability of standard and total keratometric readings (equivalent keratometric readings for Pentacam) and astigmatism measures with these three systems were evaluated with the Bland-Altman analysis. Results: Significantly higher standard and total keratometric readings were obtained with the IOL-Master compared to the other two systems (p&lt;0.001). Likewise, a significantly higher magnitude of standard and total keratometric astigmatism was obtained with the Cassini system (p&lt;0.001). Ranges of the agreement for corneal power measurements between devices varied from 0.58 D to 1.53 D, whereas they ranged from 0.46 D to 1.37 D for standard and total astigmatism measurements. Conclusion: Corneal power and astigmatism measures obtained with IOL-Master 700, Cassini, and Pentacam systems cannot be used interchangeably. The impact of these differences on the refractive predictability achieved with different types of intraocular lenses (IOL) should be evaluated in the future in order to define which is the best corneal evaluation approach for optimizing the IOL power calculations.