Spherical Power Research Articles

Comparison of negative blended lenticular lens design methods for high myopic spectacles

The power distribution, high-order polynomial, bicubic spline interpolation, and geometric construction methods were used to reduce the edge thickness and weight of negative blended lenticular lenses. Four lenses with the same optical parameters were designed, simulated, machined, and evaluated using the four methods. Spherical and cylindrical power maps were generated and compared. The methods reduced the edge thickness by 78.73% for power distribution method, 77.40% for high-order polynomial method, 78.12% for bicubic spline interpolation method and 79.86% for geometric construction method for a 35 mm radius compared to that with the spherical surface. Geometric construction, power distribution, high-order polynomial, and bicubic spline interpolation reduced the lens weight by 43.86%, 35.98%, 33.06%, and 29.76%, respectively. The center optical area for the power distribution and geometric construction methods were larger than those with the other methods.

Refractive outcomes of table-mounted and hand-held auto-refractometers in children: an observational cross-sectional study

BackgroundTo compare the refractive results of hand-held and table-mounted autorefractors.MethodsWe designed this study as an observational, cross-sectional study. We compared the mean spheric and cylinder power, spherical equivalent, Jackson cross-cylinder values, determined the limits of agreement (LoA), and evaluated the reliability of two autorefractors.ResultsWe evaluated 256 eyes of 256 pediatric patients (mean age, 9.12 ± 2.26 years; range, 5–16 years). 49% of the patients were female, and 51% were male. The Nidek HandyRef-K autorefractor measured relatively more astigmatism (P < 0.001) and less hyperopia (P = 0.024). The mean differences and 95% LoA were 0.06 D ± 0.47 D (− 0.82 D to 0.98 D) in spherical power, 0.08 D ± 0.28 D (− 0.47 D to 0.64 D) in cylindrical power, 0.11 D ± 0.47 D (− 0.81 D to 1.01 D) in spherical equivalent, 0.02 D ± 0.36 D (− 0.73 D to 0.69 D) in Jackson cross-cylinder power at 0°, 0.005 D ± 0.54 D (− 1.07 D to 1.06 D) in Jackson cross-cylinder power at 45°. We found the difference within 0.50 D in 244 (95%) eyes for spherical power, in 245 (96%) eyes for cylindrical power, 228 (89%) eyes for spherical equivalent, 224 (87%) eyes for Jackson cross-cylinder power at 0°, 213 (83%) eyes for Jackson cross-cylinder power at 45°. When comparing devices, there were strong correlations for spherical power (Spearman’s rho = 0.99, P < 0.001), cylindrical power (Spearman’s rho = 0.88, P < 0.001), and spherical equivalent (Spearman’s rho = 0.98, P < 0.001).ConclusionTwo autorefractors showed clinically applicable agreement limits; excellent reliability for spherical power and spherical equivalent and good reliability for cylindrical power; high positive percent agreement for spherical and cylindrical power, spherical equivalent, Jackson cross-cylinder power at 0°and 45°. These results showed that both devices might be used interchangeably for screening of refractive error in children.

Full-aperture diopter distribution measurement method for single vision and progressive addition lenses

Hartmann testing method is still widely used for measuring the diopter of spectacle lens. However, its aperture measurement and resolution are limited by diffraction. This paper proposes a method to obtain full-aperture diopter distribution of spectacle lenses, including progressive addition lenses (PAL). The method uses a specially designed Hartmann testing plate for generating testing rays. The plate is rotated during measurement to overcome the diffraction limitation. Both simulation and experiment are carried out for verifying this method. The diopter measurement error of spherical power lens, cylindrical power lens, and PAL are less than 1% compared to the theoretical value in simulation. In the experiment, the deviation error is less than 2% for signal vision lens, when compared with the results obtained by an automated focimeter. The result shows that the proposed method can measure the full-aperture of diopter distribution for PAL.

A Study on the Relationship between Corneal-Related Value and Ocular Sagittal Height

Purpose : To investigate the effect of corneal related values on the ocular sagittal height and which factors have the greatest influence on the ocular sagittal height. Methods : For 240 healthy eyes in their 20, 30, 40, and 50s, the anterior chamber depth and axial length were measured with IOLMaster 700. The corneal curvature radius and corneal eccentricity were measured with Keratograph 4, and spherical equivalent power was measured using KR-800. The corneal sagittal height was calculated using the formula. Results : The most influential factor in the corneal sagittal height was the corneal diameter, followed by the corneal eccentricity. And the corneal curvature radius had the least effect. A change in corneal saggital height of about 0.10mm corresponds to a change in corneal diameter of 0.20mm, and corneal eccentricity of 0.05 to 0.10 Conclusion : If soft contact lens fitting is greatly affected by the relationship between the sagittal depth of the contact lens and the sagittal height of the cornea, measurements of corneal diameter and corneal eccentricity are considered appropriate methods for selecting parameters of contact lenses. In addition, the numerical relationship between corneal sagittal height, corneal diameter and corneal eccentricity could be used as additional information for soft contact lens fitting.

Long-term outcome of refractive errors in patients with congenital blepharoptosis who have undergone ptosis surgery

ABSTRACT Clinical Relevance Ptosis surgery induces some changes in pre-existing refractive errors and astigmatism. Monitoring refractive outcomes, planning of vision rehabilitation, and amblyopia treatment may be required following ptosis surgery. Background The few studies published on the outcomes of refractive error after ptosis surgery have been controversial. The aim of this study was to evaluate long-term outcomes of refractive error in patients with congenital blepharoptosis who had undergone ptosis surgery. Methods Patients with congenital blepharoptosis who had undergone ptosis surgery were enrolled in the study. Data on pre- and post-operative refractive errors, marginal reflex distance 1 (MRD1), and levator function were obtained. The data from fellow eyes were used as the control. Results The mean patient age of patients undergoing ptosis surgery was 19.8 ± 8 years. The mean follow-up time (time between the operation and post-up measurements) was 4.7 ± 2.1 years with a range of 2–10 years. There were no significant differences in mean refractive changes, being 0.53 ± 0.40D vs. 0.36 ± 0.45D in sphere (p = 0.19) and 0.48 ± 0.56 vs. 0.30 ± 0.23 in cylinder (p = 0.17) in operated and control eyes, respectively. Astigmatism change was, however, significantly higher in the operated eyes with an MRD1 change of ≥2.5 mm (0.84 ± 0.66 vs. 0.27 ± 0.39, p = 0.024). The changes in astigmatism in the operated eyes had a significantly positive correlation with the changes of MRD1 (r = 0.497, p = 0.019). Vectorial analysis showed no significant difference between the changes in astigmatism of the operated and control eyes (0.58 *48º vs. 0.45*53º, respectively). Conclusion Spherical power of the eyes of patients with congenital ptosis who undergo ptosis surgery does not change. A significant change in astigmatism can be anticipated in eyes with more than 2.5 mm change in MRD1. There is an association between change in astigmatism and MRD1 following ptosis surgery.

Does offering only the spherical contact lens trial to the low astigmats mislead the practitioners?

To compare the visual acuity (VA), comfort, and patient preference in a soft toric contact lens (TCL) versus soft spherical contact lens (SCL) in low astigmatic subjects during the contact lens (CL) trial. This subject-masked, block randomized, 2×2 crossover study recruited 40 neophyte subjects (80 eyes) aged 18 to 33y with astigmatism in the range of 0.75-1.25 D with or without spherical power from -6.00 D to +6.00 D. The participants were scheduled for two days CL trial and were fitted with the best-fit SCL and TCL. After 4h of wear, they were assessed objectively for high contrast VA and subjective vision, comfort, and preference. The responses of 36 subjects (response rate 90%) with a mean age of 23.02±2.97y (range 18 to 33y) were analyzed. One-line improvement of monocular VA in the logMAR chart was reported to TCL as compared to SCL (-0.044±0.06 vs 0.04±0.03 logMAR, P=0.01) but the binocular vision remained similar (-0.12±0.07 vs -0.14±0.04 logMAR, P=0.38). Subjects felt a noticeable difference in clarity when shifted to TCL as compared to the SCL. The satisfaction with vision (vision quality) was significantly better with TCL (P=0.03). The fatigue with TCL was graded less at 2.5±0.6, compared to SCL at 4.6±1.3 (P=0.04). Thirty-three participants (91.6%) preferred to use contact lens of which 26 participants (79%) preferred TCL. The findings suggest that VA and comfort are better with TCL as compared to SCL which is only observed if the patient was offered both offering SCL with spherical equivalent power alone as the first option can mislead the practitioner; TCL trial should be the first choice of the lens in low-to-moderate astigmatism.

Accuracy of Noncycloplegic Refraction for Detecting Refractive Errors in School-aged African Children.

Cycloplegia is often restricted in screening settings. Previous studies have evaluated noncycloplegic refraction for screening, but their data are not fully applicable to school-aged African children. This article adds to the literature by investigating this in school-aged African children. The purpose of this study was to evaluate the ability of noncycloplegic autorefraction (NCA) and noncycloplegic retinoscopy (NCR) to detect refractive errors in school-aged African children and quantify differences between noncycloplegic and cycloplegic refraction measures. Autorefraction and retinoscopy were performed on 150 children aged 6 to 15 years before and after cyclopentolate cycloplegia. Subjective refraction was performed by the same examiner after cycloplegia. Noncycloplegic and cycloplegic measurements were compared, and the data were assessed with receiver operating characteristic curves and Bland-Altman plots. With the exception of cylindrical vector J0 (P = .17) and J45 (P = .08) obtained with NCR, all mean measures of NCA and NCR significantly differed from mean cycloplegic subjective refraction measurements by -0.71 ± 0.67 (P ≤ .001; 95% confidence interval, -2.02 to +0.60) and -0.75 ± 0.68 (P ≤ .001; 95% confidence interval, -2.08 to +0.58), respectively. Mean spherical power between the two tests did not differ (NCA -NCR, mean bias of -0.037 ± 0.675 and 95% limits of agreement of -1.36 to 1.286; P = .51). The sensitivities for detecting any refractive error for NCR and NCA were 86.8 and 82.9%, respectively, and the specificities were 82.0% for NCR and 82.4% for NCA. Performance of both tests was excellent for myopia (area under the curve, >0.90; sensitivity, ≥90%) and similar (P = .13), but the specificities for detecting hyperopia were 78.0% for NCR and 80.0% for NCA. Noncycloplegic refraction may accurately detect astigmatism and myopia in this population but may elicit higher myopic values and lower hyperopic values than using cycloplegic refraction.

Tungsten boride shields in a spherical tokamak fusion power plant

The favourable properties of tungsten borides for shielding the central high temperature superconductor (HTS) core of a spherical tokamak fusion power plant are modelled using the MCNP code. The objectives are to minimize the power deposition into the cooled HTS core, and to keep HTS radiation damage to acceptable levels by limiting the neutron and gamma fluxes. The shield materials compared are W2B, WB, W2B5 and WB4 along with a reactively sintered boride B0.329C0.074Cr0.024Fe0.274W0.299, monolithic W and WC. Five shield thicknesses between 253 and 670 mm were considered, corresponding to plasma major radii between 1400 and 2200 mm. W2B5 gave the most favourable results with a factor of ∼10 or greater reduction in neutron flux and gamma energy deposition as compared to monolithic W. These results are compared with layered water-cooled shields, giving the result that the monolithic shields, with moderating boron, gave comparable neutron flux and power deposition, and (in the case of W2B5) even better performance. Good performance without water-coolant has advantages from a reactor safety perspective due to the risks associated with radio-activation of oxygen. 10B isotope concentrations between 0% and 100% are considered for the boride shields. The naturally occurring 20% fraction gave much lower energy depositions than the 0% fraction, but the improvement largely saturated beyond 40%. Thermophysical properties of the candidate materials are discussed, in particular the thermal strain. To our knowledge, the performance of W2B5 is unrivalled by other monolithic shielding materials. This is partly as its trigonal crystal structure gives it higher atomic density compared with other borides. It is also suggested that its high performance depends on it having just high enough 10B content to maintain a constant neutron energy spectrum across the shield.

Postoperative stability of refractive error after cataract surgery

Aim. The goal of the present study is to determine how much time must pass after a cataract surgery with no complications to achieve a sufficiently stable refraction. Subjects and methods. We measured the postoperative refraction of 61 pseudophakic subjects (mean age: 74.32 ± 7.11 years) five times with an autorefractor. The subjects had undergone unilateral cataract surgery and the time intervals for the measurement went from one day to eight weeks after the operation. In order to obtain the spherical equiva- lent (SE) and the cylinder power, the difference from each measurement and the last measurement in the seventh or eighth week post-surgery was taken. The Friedman test for paired samples was used to see if there were any significant differences in spherical equivalent and cylinder power in the 5 measurements taken. In addition, two repeated measure- ments were taken on one eye of 16 phakic subjects with good ocular health pertaining to a similar age group to determine the measurement uncertainty of the autorefractor (± 1.96 SD for the measured value differences). Results. In the case of the spherical equivalent, we found no statistically significant difference between the individual re- peated test series. The cylinder power was significantly higher on the first day after the operation than during all subsequent appointments, but then showed no significant difference between all measurements taken during the examinations after the first day. The differences in the spherical equivalent between one measurement and the reference measurement (7 - 8 weeks after the surgery) resulted in 95 % confidence intervals (± 1.96 SD) of approximately ± 2.00 dioptres (D) on the first day post-surgery and lay between ± 1.20 D and ± 0.80 D in post-surgery weeks 1, 3 and 5. The corresponding con- fidence intervals for the cylinder power were ± 2.00 D on the first day post-surgery and lay between ± 1.27 D and ± 0.88 D in post-surgery weeks 1, 3 and 5. The statistical dispersion of the spherical equivalent and the cylinder power decreased slightly as the time from the surgery increased. We estimated a measurement uncertainty for automated refractometry performed on older phakic eyes of ± 0.80 D for the spherical equivalent and ± 1.16 D for the cylinder power. Conclusion. The refractive power of a pseudophakic eye can be determined with sufficient certainty after one to three weeks after undergoing cataract surgery without compli- cations. This means that optical aids to correct any residual refractive error or presbyopia can be prescribed earlier than before and, hence, the number of follow-up appointments required to measure a stable refraction can be reduced. Keywords Cataract, postoperative refraction, refraction measurement, repeated automated refractometry, Intraocular lenses (IOL)

Clinical Spectrum of Ocular and Visual Dysfunction in Children with Periventricular Leukomalacia: A Need for an Interdisciplinary Approach

AbstractThe study aimed to evaluate the ocular motility and visual and optic disc abnormalities in children diagnosed with periventricular leukomalacia (PVL). A retrospective analysis was performed on 51 consecutive children who had ophthalmic symptoms and were diagnosed with PVL by using magnetic resonance imaging. The patients were assessed for visual function, strabismus, cycloplegic refraction, fundus examination, and if appropriate, spectral-domain optical coherence tomography and visual field testing were applied. The primary outcome measures were the prevalence and visual and ocular motility dysfunctions. Mean age was 5.72 ± 2.6 years (range = 1–12), median birth weight was 2,740 g (range = 1,240–3,460), and median gestational age was 34 weeks (range = 28–38). In total, 21 patients (39.6%) had neurological deficit, 11 (21.5%) had intellectual disability, and 19 (37.2%) had no neurological symptom. In the spherical equivalent refractive error and cylinder power analysis, 10 patients had ≥3.0 D myopia, 15 had ≥3.0 D hyperopia, and eight had ≥2.50 D astigmatism. Thirteen (25.4%) children had a best-corrected visual acuity between 20/40 and 20/20 for Snellen card, while 9 (17.6%) had strabismic amblyopia and 6 (11.7%) had anisometropic amblyopia. Manifest strabismus was present in 35 patients (68.6%); of whom 12 had esotropia (23.5%), 16 had exotropia (31.3%) and 6 had vertical deviation (11.7%). Manifest or latent nystagmus was detected in 14 patients (27.4%). In 28 patients (54.9%), there was optic nerve abnormality. Two patients had hypoplastic disc, 14 had optic disc pallor, 7 had large cupping, and 5 had total optic atrophy. Six subjects underwent reliable visual field (VF) examinations, and all six had abnormal VFs, with inferior fields being most affected. Ocular motility disorders, optic nerve abnormalities, VF defects, and low visual acuity are common findings in this cohort of PVL patients and maybe the only presenting signs of the disease. The recognition of the visual disabilities and implementation of early rehabilitation may have a significant benefit in these children.

Structural Optimization of Compact Spherical Wind-Solar Hybrid Power System

Structural Optimization of Compact Spherical Wind-Solar Hybrid Power System

Agreement Between Retinoscopy, Autorefractometry and Subjective Refraction for Determining Refractive Errors in Congolese Children.

ObjectiveTo assess the agreement between retinoscopy and autorefractometry and between subjective refraction and both retinoscopy and autorefractometry in Congolese children.Patients and MethodsFifty-four children (6–17 years old) were enrolled consecutively in this cross-sectional study. Refraction was evaluated before and after cycloplegia (1% cyclopentolate) with retinoscopy and autorefractometry. Readings were compared (paired t-test) and agreement assessed with Bland–Altman plots. Subjective refraction was compared with the two methods to determine which one provides better reference estimates for subjective refraction.ResultsUnder cycloplegia, the spherical power was comparable between retinoscopy and autorefractometry (1.12 ± 1.37 D vs 1.22 ± 1.06D, P = 0.70), cylinder power was significantly more myopic on retinoscopy than autorefractometry (0.80 ± 1.10D vs −0.62 ± 0.66, P = 0.019), and SE was greater on autorefractometry than retinoscopy (0.91 ± 1.10D vs 0.72 ± 1.00D, P = 0.014). Retinoscopy and autorefractometry overestimated the power of spherical (P = 0.022 and 0.002, respectively) and cylindrical components (all P < 0.001). There was an agreement between retinoscopy and autorefractometry in measuring spherical (bias: 0.09 ± 0.16D; limit of agreement, LoA: −0.40 to 0.22D) and cylindrical power (bias: −0.18 ± 0.20D; LoA: −0.57 to 0.21D). Subjective refraction agreed with cycloplegic retinoscopy for determining SE power (bias: 0.11D; LoA: −0.51 to 0.73D).ConclusionRetinoscopy and autorefractometry can be used interchangeably in children for determining the power of spherical and cylindrical components. Cycloplegic retinoscopy is better than autorefractometry to obtain SE reference values for subjective refraction in children.

The Association between Serum 25-hydroxyvitamin D Level and Myopia in Korean

Purpose : The purpose of this study was to investigate the relationship between serum 25 (OH) vitamin D level and myopia in Korean. Methods : Using data from the National Health and Nutrition Survey 2010, a total of 5,488 people aged 10 to 69 were targeted. Myopia was divided into subcategories as follows: mild myopia (-3.00<SE≤-0.50 D), moderate myopia (-6.00<SE≤-3.00 D), and high myopia (SE≤-6.00 D). Serum 25 (OH) vitamin D concentration was classified into two types as follows: deficiency (<20 ng/mL) and normal (≥20 ng/mL). Pearson's correlation analysis and covariate-corrected complex logistic regression were performed to evaluate the association between serum 25 (OH) vitamin D level and myopia. Results : Serum 25 (OH) vitamin D level and equivalent spherical refractive power showed a positive correlation (r=0.132, p<0.001). The risk factors for myopia were age, household income, education level, sun exposure, obesity, diabetes, hypertension, cataract, and family history of eye disease. When the serum 25 (OH) vitamin D level was less than 20 ng/mL, the risk of severe myopia increased by 2.55 times (95% confidence interval: 1.27~5.16) even after the risk factors were corrected. Conclusion : High myopia was associated with serum 25 (OH) vitamin D level in Korean.

Dynamic Measurement of Refraction and Pupil Center Shift according to Illumination

Purpose : The aim of this study was to evaluate the change of refraction and pupil center shift including direction and amounts according to the illumination. Methods : From July 2020 to September 2020, 58 eyes of 29 adults (14 males and 15 females) who had no experience with ophthalmic disease and corneal refractive surgery. The average age is 35.62±14.48 years. Using an aberration analyzer, the result of measuring the refraction according to the illumination, the change of the pupil center shift were used and the average value was measured three times each. The statistical program SPSS was used to analyze whether there was a difference between the change in myopia and the pupil center according to the illumination. Results : The spherical diopter according to the illumination changed from –2.80 D to –2.94 D increasing by –0.14 D (p<0.001). The cylindrical diopter increased from –0.93 D to –0.98 D, increasing by –0.05 D (p<0.001). The change of the pupil center shifted by an average of 0.14 mm (p<0.001) in the horizontal direction and 0.13 mm in the vertical direction (p<0.001). The shift of the pupil center by direction was 35 eyes (60.3%) on the superior, 20 eyes (34.5%) on the inferior, 25 eyes (43.1%) on the nasal, and 33 eyes (56.9%) on the temporal. The horizontal shift in both eyes had a high correlation (r=0.700) and there was a low correlation in the vertical direction (r=0.244). Conclusion : In the scotopic vision, the greater the spherical power in the (-) direction, and the pupil center shifted in both horizontal and vertical directions. Therefore, when preparing spectacle lenses for night activities, it is considered that the quality of visual acuity due to the shift of the pupil center should be considered.

The effect of intraocular pressure elevation and related ocular biometry changes on corneal OCT speckle distribution in porcine eyes.

The aim of this study was to evaluate the influence of increase in intraocular pressure (IOP) and cooccurring changes in ocular biometry parameters on the corneal optical coherence tomography (OCT) speckle distribution in ex-vivo experiments on porcine intact eyes. Twenty-three eyeballs were used in the inflation test where IOP in the anterior chamber was precisely set from 10 mmHg to 40 mmHg in steps of 5 mmHg and where eye biometry was utilized (IOL Master 700). To assess the influence of the duration of the experiment on the OCT speckle statistics, the second experiment was performed with 10 eyeballs at the constant IOP of 15 mmHg. Based on the OCT scans of central cornea (Copernicus REVO), spatial maps of the scale parameter (a) and the shape parameter (v) of the gamma distribution speckle model were estimated. The means of both parameters for each spatial map were computed within the 2 mm of the central stroma. Both distributional parameters statistically significantly varied with IOP and time (one way repeated measures ANOVA, all p-values < 0.001). The a parameter revealed a faster statistically significant increase in IOP up to 25 mmHg, regardless of time. Central corneal thickness (CCT), the anterior chamber depth, and the mean equivalent spherical power varied significantly with IOP, whereas CCT and axial length changed statistically significantly with time. Statistically significant correlation was found between CCT and the a parameter, after removing IOP as a confounding factor (r = −0.576, p < 0.001). The parameters of the gamma distribution can be used not only for identifying IOP induced changes in the optical scattering within the corneal stroma, but also in corneal geometry. The approach of corneal speckle analysis could be potentially utilized for an indirect and noninvasive assessment of some properties of corneal stroma.

Subtle changes of the crystalline lens after cycloplegia: a retrospective study

BackgroundThe purpose of this study was to evaluate the shape of the crystalline lens in terms of biometry and diopters before and after cycloplegia using the CASIA2 swept-source (SS) optical coherence tomography (OCT) system on the anterior segment.MethodsThis was a retrospective study. Children and adolescents (26 males and 29 females, aged 4–21 years) with simple ametropia were selected for optometry and CASIA2 imaging at 2 separate visits before and after cycloplegia. Diopter values were derived from the spherical power (S) obtained by optometry. Biometric parameters of the crystalline lens, including the anterior chamber depth (ACD), anterior and posterior curvature of the lens (ACL and PCL), lens thickness (LTH), lens decentration (LD), lens tilt (LT), and equivalent diameter of the lens (LED), were measured by the CASIA2 system. The differences in these parameters after compared with before cycloplegia were determined, and their relationships were analyzed.ResultsFifty-five participants (106 eyes) were initially enrolled. There was a significant difference (P < 0.05) in the S (t=-7.026, P < 0.001), ACD (t=-8.796, P < 0.001), ACL (t=-13.263, P < 0.001) and LTH (t = 7.363, P < 0.001) after compared with before cycloplegia. The change in the PCL (t = 1.557, P = 0.122), LD (t = 0.876, P = 0.383), LT (t = 0.440, P = 0.661) and LED (t=-0.351, P = 0.726) was not statistically significant (P > 0.05). There was a significant (P < 0.05) correlation of the change in the S with that in the ACL (r = 0.466, P < 0.001), LTH (r=-0.592, P < 0.001), and LED (r = 0.223, P = 0.021) but not the PCL (r = 0.19, P = 0.051), LD (r=-0.048, P = 0.0628) or LT (r=-0.022, P = 0.822). Furthermore, the change in the ACD was closely related to the change in crystalline morphology. However, in children and adolescents, we found that the change in crystalline morphology was unrelated to age.ConclusionsChanges in lens morphology after compared with before cycloplegia are mainly related to the ACL and LTH, but there is no difference in the PCL, LD, LT, or LED. In the adolescent population, change in the S is related to change in the ACL, LED and LTH. However, age is unrelated to the shape and tendency of the crystalline lens. Further research is required to determine whether the same conclusion applies to different age groups and different refractive states (myopia, hyperopia, emmetropia) .

Distribution of intraocular pressure and related risk factors in a highly myopic Chinese population: an observational, cross-sectional study

ABSTRACT Clinical relevance: Those with high myopia are more likely to have glaucoma compared to those without myopia and intraocular pressure was a key factor for developing glaucoma. Thus, investigating the distribution of intraocular pressure and associated factors among those with high myopia is of high importance. Background: The aim of this work is to investigate the distribution of intraocular pressure and the correlated risk factors in a highly myopic Chinese population. Methods: A total of 884 Chinese participants with bilateral high myopia (≤ −6.00 D spherical power) were included from the Zhongshan Ophthalmic Center-Brien Holden Vision Institute High Myopia Cohort Study. All participants underwent a comprehensive ocular examination, including ocular biometry, cycloplegic refractometry, and intraocular pressure measurement with Goldmann applanation tonometry. Information on smoking and drinking status was also collected. Results: The mean spherical equivalence of left eyes was −10.02 ± 3.58 D with a mean axial length of 27.48 ± 1.55 mm. The overall mean intraocular pressure was 15.1 ± 2.4 mmHg (95% confidence interval, 15.0 to 15.3 mmHg). The intraocular pressure in the −6.00D to −7.99D spherical equivalence group, −8.00D to −9.99D spherical equivalence group, and ≤ −10.00 D group were 15.3 ± 2.4 mmHg, 15.1 ± 2.5 mmHg, and 15.0 ± 2.4 mmHg, respectively (p = 0.979). In multiple regression models, intraocular pressure in high myopes was not associated with spherical equivalence (p = 0.354) or axial length (p = 0.601), but significantly higher in those who were younger (non-standardised beta, −0.018; p = 0.007), smoked tobacco (non-standardised beta, 1.085; p = 0.001) and had greater central corneal thickness (non-standardised beta, 0.021; p < 0.001). Conclusion: Intraocular pressure was 15.1 ± 2.4 mmHg among subjects with a mean age of 22.8 years in this highly myopia Chinese population. These findings suggested that highly myopic Chinese persons of a younger age and greater central corneal thickness were more likely to have higher intraocular pressure.

Analysis of suspected visual impairment risks based on objective refraction in 3-year-old children

To evaluate the relationship between uncorrected visual acuity and non-cycloplegic refractive value among 3-year-old children in a vision screening program in Japan. Retrospective, cross-sectional study. The participants were 1746 Japanese children screened from April 2009 to July 2018, and ranged in age from 36 to 47months. Visual acuity and handheld refractive values were collected from the clinical records of 3-year-old children in a vision screening program. Multiple logistic regression analysis was used to evaluate the association between 0.3 logarithm of the minimum angle of resolution (logMAR) and > 0.3 logMAR. Correlation analysis was also performed for the presence of myopic shift. Among the 1746 children (aged [mean ± standard deviation], 37.6 ± 1.6months; percentage of boys, 50.4%), representing 3492 eyes, 116 eyes (3.3%) had > 0.3 logMAR. Multiple logistic regression analysis revealed that the risk factors for 1.75-2.00 diopter (D) spherical power (odds ratio [OR], 2.51; 95% confidence interval [CI] 1.12-5.64; P = 0.026) and 1.25-1.50 D cylindrical power (OR, 5.66; 95% CI 1.58-20.40; P < 0.01) were increased in eyes with > 0.3 logMAR. There was no myopic shift for 10years (Spearman's rank correlation coefficient; P = 0.65). It is important to set a threshold that comprises the characteristics of the autorefractor used in screening, and to ensure that, to help prevent amblyopia a thorough eye examination in ophthalmic institutions will be conducted taking into account population-based refractive values.

Quality of view through extended depth of focus intraocular lens in a model eye.

To compare the quality of images viewed through an extended depth of focus (EDF) intraocular lens (IOL) to that through multifocal or monofocal IOL. Experimental study METHODS: EDF IOL (Symfony®, ZXR00V, Johnson & Johnson Vision), diffractive multifocal (ZLB00, + 3.25D or ZMB00, + 4.0D), or monofocal (ZCB00V) IOL with a spherical power of + 20.0 diopter (D) was placed in a fluid-filled model eye with corneal aberrations similar to those of human eyes. A United States Air Force Resolution Grating Target was glued to the posterior surface of the model eye and viewed through a flat contact lens, a 60D or 128D wide-angle non-contact lens (Resight®) or wide-angle contact lens (MiniQuad®). The contrast of the grating images recorded with the EDF and multifocal IOLs were compared to those through the monofocal IOL. The grating images viewed through the flat contact lens were slightly blurred when viewed through the EDF IOL but clearer than those through the multifocal IOLs with very blurred images in the periphery. The contrast of the images viewed through the EDF and multifocal IOLs through the flat contact lens was significantly lower than through the monofocal IOL (P < 0.02). The contrast of the images viewed through the EDF IOL with 60D or 128D wide-angle non-contact lens was significantly lower than through the monofocal IOL (P < 0.05) but not with wide-angle contact lens. Our results suggest that vitreous surgeons can accomplish a clearer view during vitrectomy in EDF IOL-implanted eyes with a wide-angle viewing contact lens and a flat contact lens than in multifocal IOL-implanted eyes.

Comparison of Binocular Vision Parameters Pre- and Post-EPILASIK Laser Vision Correction Surgery for Myopia in a Pilot Study - Can Vision Therapy Augment Refractive Results?

Purpose:To analyze the changes in the binocular vision parameters after bilateral Epilasik laser vision correction surgery (LVCS).Setting:Medical Research Foundation, Tamil Nadu, India.Study design:Prospective cohort study.Methods:Subjects with a best corrected visual acuity of ≤ 0.0 Log MAR scale and refractive error: < 6.00DS of myopia, < 0.75D of astigmatism, and < 1D of anisometropia were included in the study. All subjects underwent a comprehensive eye examination, LVCS workup which included corneal topography, tomography, aberrometry, and dry eye assessment prior to binocular vision assessment. Complete Binocular vision assessment which included stereopsis, fusion for distance and near, near point of convergence, phoria measurement, vergence amplitudes and facility, accommodative amplitudes, response, and facility was performed with the best corrected vision prior to LVCS, one month and six months after the surgery.Results:Twenty-five subjects of age 23.8 ± 2.9 years were included. Age ranged from 20 to 32 years. Ten were female and 15 were male. The median spherical power was –2.00DS with an inter quartile range (IQR) of –1.50DS to –3.00DS for both eyes. The median cylindrical power was plano with IQR –0.50DC to –1.00DC for both eyes. There was a statistically significant decrease in monocular and binocular accommodative amplitudes (accounting for age-related changes) as well as positive fusional vergence recovery for near between baseline and one month after surgery (p < 0.05).Conclusion:Though subjects were asymptomatic post LVCS, still there is an indication that myopic LVCS could precipitate or aggravate an existing non-strabismic binocular vision anomaly. Comprehensive binocular vision assessment and appropriate management is recommended before and after LVCS.