Oblique Astigmatism Research Articles

The profile of astigmatism in 6–12-year-old children in Iran

PurposeTo determine the prevalence of astigmatism and its determinants in schoolchildren aged 6–12 years. MethodsThe students selected by stratified cluster random sampling in Shahroud, north of Iran. Optometric examination included uncorrected visual acuity, refraction with autorefractometer, manifest refraction with retinoscopy followed by subjective and cycloplegic refraction (after two drops of cyclopentolate 1% with 5min interval were instilled in each eye).A cylinder power ≥0.75diopter (D) in at least one eye was considered as astigmatism. The prevalence of astigmatism was reported based on a cylinder power higher than 0.50, 1.00, and 2.00D in cycloplegic refraction, followed by power vector analysis. ResultsAfter applying the inclusion criteria, the data of 5528 children were analyzed. The prevalence of astigmatism was 16.7% (95% CI: 15.6–17.7) in total, 16.6% (95% CI: 15.2–18.0) in boys and 16.8% (95% CI: 15.2–18.3) in girls (p=0.920) and decreased from 21.5% in 6-year-old children to 13.7% in 10-year-olds, and then again increased to 18.3% in children aged 12 years. Moreover, 17.2% (95% CI: 16.0–18.3) of urban and 12.1% (95% CI: 10.0–14.1) of rural children had astigmatism (p<0.001). The prevalence of with-the-rule, against-the-rule, and oblique astigmatism was 14.2%, 2.1%, and 0.33%, respectively. The mean cylinder power was −1.31, −0.46, and −0.44D in children with spherical myopia, emmetropia, and hyperopia, respectively (p<0.001). Urban students had a higher J0 and boys had a higher J45. ConclusionThe prevalence of astigmatism in this study was lower than previous studies. Astigmatism prevalence was markedly higher in urban children.

Frequency of Corneal Astigmatism in Patients Presenting for Senile Cataract Surgery at a Teaching Hospital in Indian Rural Population.

The aim of this study was to assess prevalence of corneal astigmatism before cataract surgery in old age in Indian rural population. Prospective, cross-sectional, and observational study. Keratometric values were measured with an auto refractokeratometer in patients presenting for cataract surgery between January 2017 and May 2018. The demographic profiles of patients were recorded. Axial length and intraocular lens power were measured. Data were analyzed in SPSS software. This study included 1000 eyes of 880 patients with a mean age of 65.1 ± 10.12 years. The mean astigmatism was 0.89 ± 0.63 D. A total of 179 eyes (17.9%) had astigmatism between 1.00 and 1.49 D; 34 eyes (3.4%) had astigmatism between 2.00 and 2.5 D; and 20 eyes (2%) had astigmatism >3 D. Overall, 325 eyes (32.5%) had astigmatism >1.00 D. Against the rule astigmatism was seen in 44.6% cases, oblique astigmatism was seen in 32% cases, and with the rule astigmatism was seen in 20.7% cases. Against the rule astigmatism increased with age and reached a maximum between 60 and 69 years. Male eyes had flatter corneal curvature than female eyes. The mean axial length was 25.59 mm, and the mean intraocular lens power was 21.05 ± 1.0D. We found that 32.5% patients had corneal astigmatism >1 D and may benefit from toric intraocular lenses implantation. The results of this analysis provide normative data for the hospital to plan for correction of corneal astigmatism in patients undergoing cataract surgery.

Pattern of corneal astigmatism induced by primary pterygium in patients with cataract in a secondary hospital in Southern China: a cross-sectional study

ObjectivesTo review the pattern of primary pterygium-induced corneal astigmatism in patients with cataract in a southern Chinese population.DesignClinic-based cross-sectional retrospective study.SettingA secondary hospital at southern China.ParticipantsA group of 1689 eyes...

Management of vernal keratoconjunctivitis in children in Saudi Arabia.

Vernal keratoconjunctivitis is a chronic inflammatory disease of the ocular surface and one of the worst types of allergic conjunctival diseases. Because of its chronic nature, it can damage the cornea, resulting in sight-threatening complications if left untreated. The disease affects mainly young children starting around the age of 7 years. We used keywords to search for published English articles in PUBMED, Google Scholar, EMBASE, and Cochrane Database of Systematic Reviews. Most of the published literature is focusing on general management of the disease and few publications focusing on treatment in the pediatric age group. We highlight the importance of how is the topical management differs between age groups. We focused on the importance of doing cycloplegic refraction for each child as the risk of keratoconus and oblique astigmatism is high in these cases. Furthermore, we highlight the importance of using eye lubricants as a therapeutic and preventive tool for the attacks of the disease. We highlight that most of the recent effective medications (especially the off-label ones) are not available in Saudi Arabia, such as tacrolimus, and some are only available to be prepared in tertiary center pharmacies as Cyclosporine A with higher concentrations.

Evaluation of the effects of pterygium surgery on visual acuity and anterior segment measurements using corneal topography

Purpose: This study was carried out to evaluate the effects of pterygium surgery on visual acuity, corneal astigmatism, corneal refraction, and corneal topography and the changes of these parameters in the postoperative period. Material and Methods: Forty eyes of 34 patients presented with only primary pterygium were included in the present study. Patients with features that could affect corneal topography, such as previous ocular trauma or surgery, corneal scarring, keratoconus, dry eye, and contact lens use, were excluded from the study. After excisional pterygium surgery, primary conjunctival closure was performed. Results: The mean baseline visual acuity measured by the Snellen chart in decimal improved from 0.78±0.19 to 0.97±0.54 in the 3rd month of the postoperative period. The mean values of SimK were 43.33±1.54 diopters (D) and 44.27 ± 1.43 D preoperatively and postoperatively (at 3rd month), respectively. The baseline topographic astigmatism was significantly decreased from 1.85 ± 1.77 (0.50-7.00) D to 0.65 ± 0.40 (0.20-1.75) D at 3rd month of postoperative period (P = 0.000). While 77.5 % of the patients had regular astigmatism at baseline, oblique and irregular astigmatism was observed in the early postoperative period, but 65 % of these patients turned back to regular astigmatism in the late postoperative period. Conclusion: Corneal topographic values were stabilized in the first month of the postoperative period. So, the plan of refractive or cataract surgeries may be appropriate after the stabilization of the corneal refractive components following the first month of pterygium surgery.

Validation of Mahajan's formula for scaling ocular higher-order aberrations by pupil size.

Purpose:Zernike polynomials for describing ocular higher order aberrations are affected by pupil aperture. The current study aimed to validate Mahajan’s formula for scaling Zernike polynomials by pupil size.Methods:Higher order aberrations for 3 intraocular lens models (AcrySof IQ IOL SN60WF, Technis ZA9003, Adapt Advanced Optics) were measured using the Zywave aberrometer and a purpose-built physical model eye. Zernike coefficients were mathematically scaled from a 5 mm to a 3 mm pupil diameter (5:3 mm), from a 5 mm to a 2 mm pupil diameter (5:2 mm), and from a 3 mm to a 2 mm pupil diameter (3:2 mm). Agreement between the scaled coefficients and the measured coefficients at the same pupil aperture was assessed using the Bland–Altman method in R statistical software.Results:No statistically significant mean difference (MD) occurred between the scaled and measured Zernike coefficients for 21 of 23 analyses after Holm-Bonferroni correction (P > 0.05). Mean differences between the scaled and measured Zernike coefficients were clinically insignificant for all aberrations up to the fourth order, and within 0.10 μm. Oblique secondary astigmatism (Z−24) was significantly different in the 5:3 mm comparison (MD = - 0.04 μm, P < 0.01). Horizontal coma (Z13) was significantly different in the 3:2 mm comparison (MD = - 0.07 μm, P = 0.03). There were borderline statistical differences in both vertical (Z−13) and horizontal coma (Z13) in the 5:3 mm comparison (MD = 0.02 μm, - 0.09 μm, P = 0.05, 0.05, respectively).Conclusion:A formula for the scaling of higher order aberrations by pupil size is validated as accurate. Pupil scaling enables accurate comparison of individual higher order aberrations in clinical research for situations involving different pupil sizes.

Idiopathic spontaneous filtering bleb: Is there an autoimmune etiology?

A 45-year-old male presented with complaints of defective vision for near. There was no prior history of trauma, recurrent redness, or surgery. He is a known patient of hypothyroidism and vitiligo. His best-corrected visual acuity was 6/6, N6 in both the eyes (BE). Slit-lamp examination revealed a diffuse, elevated, avascular thin bleb near the limbus in the superonasal quadrant with underlying scleral thinning in BE. Right eye (RE) showed clear cornea, quiet and deep anterior chamber, normal iris pattern, and clear lens. Left eye (LE) showed peripheral corneal vascularisation with lipid deposits at 10'o clock anterior to the area of scleral thinning and bleb formation, the rest of the anterior segment was normal [Fig. 1a and b]. Schirmer's test was normal and Seidel's test did not reveal any leak in BE. His intraocular pressure was 9 and 10 mm Hg in the RE and LE, respectively. Gonioscopy revealed open angles in BE with an area of hyperpigmentation around fistula at 2 o'clock in the RE and increased pigmentation with prominent iris processes in the nasal quadrant in LE [Fig. 1c and d]. The fundus examination revealed an average size disc with a cup to disc ratio of 0.4:1, healthy neuroretinal rim and attached retina in BE.Figure 1: Right eye showing superonasal diffuse avascular thin bleb (a). Left eye showing superonasal diffuse avascular thin bleb with scleral thinning, corneal vascularisation, and lipid deposits (b). Gonioscopy showing fistula with hyperpigmentation anterior to schwalbe's line at 2'0 clock (arrowhead) in the right eye (c) and increased pigmentation with prominent iris processes in the nasal quadrant in left eye (d). Ultrasound biomicroscopy image of the right (e) and left (f) eye showing communicating fistula between the anterior chamber and subconjunctival space, indicated by the arrowheadsCorneal topography was suggestive of oblique astigmatism with flattening along the meridian of the bleb without evidence of corneal ectasia in BE. Ultrasound biomicroscopy revealed a communicating fistula between the anterior chamber and subconjunctival space in BE [Fig. 1e and f]. Physical examination was unremarkable, except for depigmented patches in the skin. Blood investigations revealed high thyroid peroxidase antibody titer (157 IU/mL), whereas C-reactive protein, rheumatoid factor, and antinuclear antibody were within normal limits. Discussion Spontaneous filtering bleb is a rare condition, which can develop if a communicating fistula between the anterior chamber and subconjunctival space is established. Spontaneous filtering bleb has been reported in patients with Axenfeld syndrome,[1] Terrien marginal degeneration,[2] Traboulsi syndrome,[34] connective tissue diseases,[56] and without any ocular or systemic association.[27] Our patient with hypothyroidism and vitiligo, has scleral thinning and subconjunctival bleb in both the eyes. There were no signs of anterior segment abnormalities or facial dysmorphism. Considering the fact that our patient has 2 autoimmune systemic conditions, we postulate that the scleral thinning and spontaneous bleb formation could be due to autoimmune etiology. 2.1 Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. 2.2 Financial support and sponsorship Nil. 2.3 Conflicts of interest There are no conflicts of interest.

Total corneal refractive power and shape in Down syndrome.

To determine the total corneal refractive power in 1-8 mm corneal zones and the 8 mm Q-value in non-keratoconic patients with Down syndrome and normal subjects aged 10-30 years. Right eye data from 203 Down syndrome patients (mean ± standard deviation age: 17.0 ± 4.7 years) and 189 age- and gender-matched normal subjects (17.1 ± 4.5 years) were compared. Main extracted Pentacam indices were total corneal refractive power in steep and flat axes, and mean and difference (corneal astigmatism) total corneal refractive power in 1-8 mm zones. Mean total corneal refractive power in 1-8 mm zones was 45.17-45.74 D and 42.91-43.52 D in Down and normal group, respectively (all p < 0.001). The coefficients of variation of total corneal refractive power from the center to the periphery were similar in the two groups (p = 0.855). None of the mean total corneal refractive powers significantly correlated with age, and all of them were significantly higher in females (p < 0.001). Mean total corneal refractive power-based corneal astigmatism in these zones changed from 1.46 to 1.66 D in Down syndrome patients and 1.64 to 1.99 D in normal group. All corneal astigmatism indices were similar between two groups (all p > 0.05). The prevalence of against the rule and oblique astigmatism in all zones were higher in the Down syndrome group (all p < 0.05). Adolescent and young non-keratoconic patients with Down syndrome have a more prolate cornea and a homogeneous keratometry distribution. In this population, females have a steeper cornea.

Unconscious meridional rivalry in oblique astigmatism

Unconscious meridional rivalry in oblique astigmatism

Distribution of posterior corneal astigmatism and its effect on the calculation of Toric intraocular lens

Objective To analysis the distribution of posterior corneal astigmatism (PA) and evaluate the influence of keratometric astigmatism (KA) and total corneal astigmatism (TCA) on the calculation of Toric intraocular lens (Toric IOL) in patients with age-related cataract (ARC) and high corneal astigmatism. Methods An observational study design was adopted.Pentacam was used to measure 200 eyes of 181 patients with ARC and KA>0.75 D in Affiliated Hospital of Nantong University from August 2016 to April 2017.KA, PA, TCA and anterior corneal astigmatism (AA) were recorded.The astigmatism magnitude and axis of PA was studied.The subjects were divided into astigmatism with the rule group, astigmatism against the rule group and oblique astigmatism group according to the axis of AA.The correlations of decomposition values between PA and AA or KA and TCA in each group were analyzed by Pearson linear correlation analysis.The difference of decomposition values between KA and TCA in each group was compared by paired sample t test.The type and axis of Toric IOL were calculated by online formula according to KA and TCA.This study followed the Declaration of Helsinki and written informed consent was obtained from each patient prior to any medical examination. Results The mean astigmatic magnitudes of PA was -0.32 D×93.1°.PA exceeded 0.5 D in 22 eyes (11%). The steepest posterior corneal meridian was vertically aligned in 163 eyes (81.5%). The decomposition value KP(0) and KP(45) of PA were positively correlated with those of AA (r=0.480, P<0.001; r=0.251, P<0.001). The mean astigmatic magnitudes of KA and TCA were 1.44 D×89.6° and 1.32 D×89.5° in astigmatism with the rule group, 1.39 D×153.4° and 1.71 D×154.4° in astigmatism against the rule group and 1.13 D×122.0° and 1.24 D×124.2° in oblique astigmatism group.53 eyes (69.7%) had KA higher than TCA in astigmatism with the rule group.82 eyes (87.3%) had KA lower than TCA in astigmatism against the rule group; 20 eyes (66.7%) had KA lower than TCA in oblique astigmatism group.There were significant differences in KP (0) between KA and TCA in different astigmatism groups (all at P<0.001). The calculated Toric IOL type were inconsistent in 85 eyes(42.5%) and the calculated axis were inconsistent in 176 eyes (88.2%). Conclusions In patients with high corneal astigmatism, the astigmatism type of PA is mostly astigmatism against the rule.Ignoring the PA can lead to deviation of Toric IOL type selection and axis placement in some patients.For patients who cannot measure PA or TCA, the type of Toric IOL should be adjusted appropriately. Key words: Cataract; Posterior corneal astigmatism; Total corneal astigmatism; Keratometric astigmatism; Toric intraocular lens

Evaluation of biometry and corneal astigmatism in cataract surgery patients in Northern United Arab Emirates.

To analyze biometric parameters and patterns of corneal astigmatism in cataract surgery patients using optical low-coherence interferometry in Northern United Arab Emirates (UAE). Axial length (AL), anterior chamber depth (ACD), horizontal corneal diameter (white to white, WTW) and flat and steep keratometry (K1 and K2, respectively) were optically measured using optical low-coherence interferometry (Aladdin). Ocular datasets acquired between 2015 and 2018 were collected and analyzed. This study evaluated 238 eyes of 123 cataract patients with a mean age of 67.1 ± 9.4years. Mean AL, ACD, WTW, K1, and K2 were 23.22 ± 0.99mm, 3.05 ± 0.36mm, 11.19 ± 0.46mm, 43.72 ± 1.80 diopter (D), and 45.04 ± 1.71D, respectively. Mean corneal astigmatism was 1.32 ± 0.97D. Corneal astigmatism of 1.5D or greater was found in 32.4%. With the rule, against the rule, and oblique astigmatism were found in 29.8%, 57.1%, and 13.0% of eyes, respectively. Results of this study provide normative data for cataract surgery as an informative reference in Northern UAE, the Middle East. This study showed higher corneal astigmatism in Northern UAE than those in other countries.

Anterior Corneal Curvature and Aberration Changes After Scleral Lens Wear in Keratoconus Patients With and Without Ring Segments.

To evaluate changes in the anterior corneal curvature and aberrometry after scleral contact lens wear in keratoconus (KC) subjects with and without intracorneal ring segments (ICRS). Twenty-six subjects diagnosed with keratoconus were selected to participate in the study. Subjects were divided into 2 groups, those with ICRS (KC-ICRS group) and those without ICRS (KC group). Subjects were instructed to wear 16.5-mm scleral lenses for 8 hours. Topographic and aberrometric parameters were evaluated before lens wear and immediately after lens removal. Anterior corneal curvature was evaluated at corneal diameters of 2, 4, 6, and 8 mm, and corneal aberrations were measured at 4-, 6-, and 8-mm pupil diameters. The mean age of subjects was 36.95±8.95 years. In KC group, there was a statistically significant flattening of the central corneal curvature, from 6.98 to 7.09 mm (P<0.05). No changes were found in the central corneal curvature in the KC-ICRS group. The KC group showed anterior corneal curvature flattening, mainly in the nasal quadrant. The KC-ICRS group showed flattening primarily in the inferior hemisphere. In the KC group, spherical aberration for 6-mm pupil increased significantly. In the KC-ICRS group, changes in aberrations were significant for high-order root mean square at 4- and 6-mm pupil diameters (P<0.05), for oblique astigmatism for 4 mm and 6 mm, and for vertical coma for 4-mm pupil (P<0.05). Short-term scleral lens wear showed flattening of the anterior corneal surface in all subjects. In the KC group, the flattening was more pronounced in the nasal quadrant while changes were more pronounced inferiorly in KC-ICRS group.

Treatment of High Astigmatism with WaveLight Allegretto Eye-Q Excimer Laser Platform

Introduction:The WaveLight Allegretto Eye-Q is a flying-spot excimer laser, with a pulse repetition rate of 400Hz, with two galvanometric scanners for positioning laser pulses. The system has an infrared high speed camera operating at 400Hz to track the patient’s eye movements that either compensates for changes in eye position or interrupts the treatment if the eye moves outside a preset predetermined range.Aim:The purpose of this study was to investigate WaveLight Allegretto Eye-Q 400Hz laser delivery platform aimed to correct astigmatism by subjecting the pre and postoperative astigmatic values to vector analysis.Methods:Patients were divided into two groups, depending on the type of astigmatism. Astigmatism was between 2 and 7 diopters (D). A total of 188 eyes (110 patients), 127 eyes (71 patients) with myopic astigmatism and 61 eyes (39 patients) with mixed astigmatism underwent unremarkable LASIK correction on WaveLight Allegretto Eye-Q 400Hz. The preoperative and postoperative sphere, negative cylinder [C] and axis (ø) of manifest refractions were subjected to vector analysis by calculations of the standard J0 (cos [4π(ø-90)/360]xC/2) and J45 (sin[4π(ø-90)/ 360]xC/2).Results:Reporting the key results, we found that J0 significantly reduced after LASIK (p<0.001) but not J45. There was no significant association between individual pairs of pre and postoperative J0 &J45 values.Conclusion:WaveLight Allegretto 400Hz showed excellent results for treating patients with high astigmatism, regardless whether it is mixed or myopic astigmatism. The J45 did not reduce significantly possibly because of the low number of eyes with oblique astigmatism. There was no genuine difference postoperatively between groups treated on WaveLight Allegretto platform according to the vector analyses.

Influence of Preoperative Astigmatism Type and Magnitude on the Effectiveness of SMILE Correction.

To assess the effectiveness of small incision lenticule extraction (SMILE) as a function of the astigmatism level and type. A total of 102 right eyes were included in this study. Refractive astigmatism and corneal astigmatism measured with Scheimpflug technology were retrieved from the preoperative visit and the 3-month follow-up visit. Patients were split into three groups according to the preoperative refractive astigmatism (0.50, 0.75 to 1.25, and 1.50 diopters [D] or greater) and the effectiveness among each group was evaluated according to the with-the-rule (WTR), against-the-rule (ATR), and oblique classifications. The standard Alpins method was used for the analysis. Resultant astigmatism was not associated with its preoperative classification when the total sample was considered, but a significant association emerged between the presence of resultant astigmatism and its preoperative classification in the 1.50 D or greater group. The magnitude of error was significantly lower in the WTR (median: -0.30 D) than in the oblique and ATR astigmatism groups, resulting in a coefficient of adjustment of 1.13 for WTR astigmatism of 1.50 D or greater but not for the other types. Astigmatism correction with SMILE is predictable for astigmatism lower than 1.50 D without the need to apply a correction. However, higher undercorrection is present in WTR astigmatism of 1.50 D or greater. [J Refract Surg. 2019;35(1):40-47.].

The effects of experimentally induced graded monocular and binocular astigmatism on near stereoacuity

PurposeTo determine the effects of experimentally induced graded monocular and binocular astigmatism on near Stereoacuity in healthy adults. MethodThis prospective cross-sectional study was performed on 60 healthy adults ranging between 19 and 33 years of age recruited from College of Applied Medical Sciences. All subjects were emmetropic with normal binocular single vision, and stereoacuity of 40 sec of arc. Enrolled subjects were divided into four groups, each with 15 participants. Myopic astigmatism was induced in two groups, either monocularly or binocularly using +1.00 DC and +2.00 DC at different axes 45, 90 and 180. The remaining two groups were subjected to induced hypermetropic astigmatism using −1.00 DC and −2.00 DC at different axes 45, 90 and 180. The Titmus Fly Stereo Test was used to measure near stereoacuity both before and after induction of astigmatism. ResultsThere was a reduction in stereoacuity with an increase in dioptric power of astigmatism (p < 0.05). In all groups, oblique astigmatism had the most significant effect followed by against the rule astigmatism and then with the rule astigmatism. Binocular induced hypermetropic astigmatism caused more reduction in stereoacuity than binocular induced myopic astigmatism, but statistically not significant. A similar impact was noted between monocular myopic astigmatism and monocular hyperopic astigmatism (p = 0.037), (p = 0.049) and (p = 0.044) with 2.00 D cylinder at 180, 90 and 45 axes, respectively. ConclusionThe results indicate that the small amount of monocular or binocular astigmatism will affect on Stereoacuity, and the amount of reduction varies according to the axis of orientation.

Influence of severity and types of astigmatism on visual acuity in school-aged children in southern China.

To investigate the influence of astigmatism on visual acuity in school-aged children, and to define a cutoff for clinically significant astigmatism. This is a population-based, cross-sectional study. Among 5053 enumerated children aged 5-15y in Guangzhou, 3729 (73.8%) children aged 7-15 with successful cycloplegic auto-refraction (1% cyclopentolate) and a reliable visual acuity measurement were included. Ocular measurement included external eye, anterior segment, media and fundus and cycloplegic auto-refraction. Primary outcome measures included the relationship between severity and subtypes of astigmatism and the prevalence of visual impairment. Three criteria for visual impairment were adopted: best-corrected visual acuity (BCVA) ≤0.7, uncorrected visual acuity (UCVA) ≤0.5 or <0.7 in the right eye. Increases of cylinder power was significantly associated with worse visual acuity (UCVA: β=0.051, P<0.01; BCVA: β=0.025, P<0.001). A substantial increase in UCVI and BCVI was seen with astigmatism of 1.00 diopter (D) or more. Astigmatism ≥1.00 D had a greater BCVI prevalence than cylinder power less than 1.00 D (OR=4.20, 95%CI: 3.08-5.74), and this was also true for hyperopic, emmetropic and myopic refraction categories. Oblique astigmatism was associated with a higher risk of BCVI relative to with the rule astigmatism in myopic refractive category (OR=12.87, 95%CI: 2.20-75.38). Both magnitude and subtypes of astigmatism influence the prevalence of visual impairment in school children. Cylinder ≥1.00 D may be useful as a cutoff for clinically significant astigmatism.

Distribution of posterior corneal astigmatism and aberration before cataract surgery in Chinese patients

To study the prevalence of posterior corneal astigmatism (PCA) and aberration in Chinese eyes before cataract surgery. A cross-sectional study was conducted in Eye and ENT Hospital of Fudan University, Shanghai. In all, we enrolled 1976 eligible eyes of 1976 cataract patients. The astigmatism and aberrations of anterior and posterior cornea were measured by the rotating Scheimpflug System (Pentacam HR, Oculus). Cataract was diagnosed using slit-lamp examination. The mean age of patients was 61.82 ± 13.67 years old. Mean PCA was 0.28 ± 0.16 (range 0-1.0) D and 87.04% eyes had PCA values <0.5 D. WTR astigmatism predominated the anterior cornea astigmatism (43.1%), while ATR astigmatism predominated posterior (85.4%) and total corneal astigmatism (47.2%). We found a shift tendency of WTR to ATR with aging in anterior corneal astigmatism, while PCA remains ATR. A positive correlation between the magnitude of anterior and posterior corneal astigmatism (r2 = 0.089, P < 0.001) was found, especially in WTR anterior cornea astigmatism eyes (r2 = 0.298, P < 0.001). Compared with total corneal astigmatism, anterior corneal measurements overestimated WTR astigmatism by a mean of 0.24 ± 0.13 (D), and underestimated ATR astigmatism and oblique astigmatism in most eyes. Furthermore, anterior corneal aberrations measurements overestimated the total corneal aberration in most eyes. About 12.96% of eyes had PCA ≥0.5 D. The posterior surface remained ATR astigmatism in most cases with aging. Neglecting the posterior cornea would result in overestimation in WTR anterior corneal eyes and underestimation in ATR and oblique anterior corneal eyes. Also, the posterior corneal aberration was also essential in clinics.

Sex-related differences in corneal astigmatism and shape with age

To compare corneal astigmatism and shape between male and female eyes in relationship to age. Hayashi Eye Hospital, Fukuoka, Japan. Prospective case series. Eyes of men and women in 5 age groups (40 to 49years, 50 to 59years, 60 to 69years, 70 to 79years, and ≥80years) had videokeratographic evaluations using a Placido-Scheimpflug system. Corneal astigmatism decomposed to vertical-horizontal (J0) and oblique (J45) astigmatism components was compared between male and female eyes, and corneal shape changes were compared using videokeratography maps. The study comprised 1000 eyes (100 eyes of male patients and 100 eyes of female patients in each of the 5 age groups). The mean J0 of the total and anterior cornea were significantly smaller in male eyes than in female eyes in all age groups (P≤.0269) with no significant difference in the J45 between sexes, indicating greater against-the-rule (ATR) astigmatism in male eyes. The mean J0 of the posterior cornea did not differ significantly between sexes except in the 50 to 59years group (P=.0105). The ATR astigmatic change per decade did not differ significantly between men and women. Videokeratography maps revealed that the total and anterior corneal shape changed to ATR astigmatism with age in both sexes, and that this ATR change began at a younger age in male eyes than in female eyes. The posterior corneal shape did not differ between sexes at any age. Against-the-rule corneal astigmatism was greater and the ATR astigmatic change with age began earlier in the male eyes than in the female eyes, suggesting that target astigmatism should be determined separately for men and women when performing astigmatism correction.

Characteristics of posterior corneal astigmatism and aberration in cataract patients with high myopia

Objective This study was to investigate the characteristics of posterior corneal astigmatism (PCA) and aberration in cataract patients with high myopia. Methods A retrospective study was designed.Two hundred and eighty-two eligible eyes of 190 cataract patients were enrolled in Eye and ENT Hospital of Fudan University from September to December, 2014.The eyes were classified into two groups according to axial length (AL): high myopia group with 139 eyes (AL≥26 mm) and control group with 143 eyes (AL was 20 to 25 mm). The mean keratometric mid-radius of curvature (Km), corneal central thickness (CCT), astigmatism and aberrations were measured by the rotating Scheimpflug System (Pentacam), and the AL were measured by the partial coherence interferometry (IOL Master). This study followed the Helsinki declaration, and was approved by the Ethic Committee of Eye and ENT Hospital, Fudan University.Informed consent was signed from each patient. Results In high myopia group, the mean PCA was 0.3 D (range 0~0.9 D) and 92.8% eyes had PCA values <0.5 D. The steep corneal meridian was aligned vertically (60°~120°) in 87.1% eyes for the posterior corneal surface.There was no significant difference in PCA between the high myopia group and the control group (P=0.797). Significant positive linear correlations was found between PCA and anterior corneal astigmatism (ACA), PCA and anterior corneal root mean square (RMS), PCA and anterior lower-order RMS, PCA and posterior corneal RMS, PCA and posterior high-order RMS, PCA and posterior lower-order RMS (r=0.235, P=0.005; r=0.217, P=0.010; r=0.229, P=0.007; r=0.395, P=0.000; r=0.243, P=0.004; r=0.384, P=0.000). Compared with total corneal astigmatism (TCA), anterior corneal measurements overestimated with-the-rule astigmatism (WTR) by a mean of (0.27±0.18)D in 65.67% eyes, underestimated against-the-rule astigmatism (ATR) by (0.27±0.18)D in 88.10% eyes and underestimated oblique astigmatism (Obl) by (0.22±0.10)D in 63.33% eyes.Compared with total corneal aberrations, anterior corneal aberrations measurements overestimated by (0.275±0.176)μm in 87.05% eyes, and the anterior corneal astigmatism types had no effect on the result. Conclusions In high myopia group, 92.8% eyes had PCA values <0.5 D and the main astigmatism type in posterior corneal surface was ATR.The posterior corneal astigmatism and aberration were needed to consider in choosing intraocular lens (IOL) before cataract surgery. Key words: High myopia; Secondary cataract; Posterior corneal surface; Astigmatism; Aberration

Self‐assessment of refractive errors using a simple optical approach

BackgroundThis explorative study investigated procedures for the self‐assessment of spherocylindrical refractive errors.MethodsEighteen participants with a mean age of 34.0 ± 8.8-years were enrolled. Adjustable Alvarez lenses were mounted in a rotatable ring holder and two procedures were tested for the self‐adjustment: (1) rotation of the lens in three meridians: 0°, 60° and 120° and (2) rotation of the optotypes in the same meridians. Starting from maximum positive power, the participants were required to decrease the power of the Alvarez lens until the optotypes (0.0 logMAR) appeared to be clear the first time. Best‐corrected visual acuity (BVA) was measured using a psychophysical staircase procedure. Bland–Altmann analysis was carried out in order to calculate the limits of agreement between the self‐refraction method and the standard subjective refraction.ResultsUsing procedure 1, 77-per cent of the subjects achieved a VA ≥ 0.1 logMAR (6/7.5) and the same was true for 88-per cent of the subjects using procedure 2. Using procedure 1, a significantly worse BVA was found, when compared to subjective refraction (ΔVA = −0.15 logMAR, F3,140 = 7.11, p = 0.046, median test). Analysis of variance (ANOVA) analysis showed a significant influence of the refraction method on the oblique astigmatism component J45 but not for the spherical equivalent M and the straight astigmatism component J0 (M: F3,140 = 0.532, p = 0.661; J0: F3,140 = 0.056, p = 0.983; J45: F3,140 = 13.97, p < 0.001; ANOVA). The limits of agreement for the spherical equivalent error M were ± 1.10-D and ± 1.20-D and for the astigmatic components J0 ± 0.78-D and ± 0.59-D and for J45 ± 0.62-D and ± 0.54-D, for procedure 1 and procedure 2, respectively.ConclusionsFixed adjustable Alvarez lenses and rotatable stimuli can provide a fast and precise self‐assessment method to measure the spherocylindrical error of the eye.