scholarly journals New Objective Refraction Metric Based on Sphere Fitting to the Wavefront

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Mateusz Jaskulski ◽  
Andreí Martínez-Finkelshtein ◽  
Norberto López-Gil
Keyword(s):  
Pupil Size ◽  
Spherical Equivalent ◽  
Independent Dataset ◽  
Accurate Predictor ◽  
Equivalent Sphere ◽  
Wavefront Error ◽  
Variable Distance ◽  
The Mean ◽  
Similar Accuracy ◽  
Sphere Fitting

Purpose. To develop an objective refraction formula based on the ocular wavefront error (WFE) expressed in terms of Zernike coefficients and pupil radius, which would be an accurate predictor of subjective spherical equivalent (SE) for different pupil sizes.Methods. A sphere is fitted to the ocular wavefront at the center and at a variable distance,t. The optimal fitting distance,topt, is obtained empirically from a dataset of 308 eyes as a function of objective refraction pupil radius,r0, and used to define the formula of a new wavefront refraction metric (MTR). The metric is tested in another, independent dataset of 200 eyes.Results. For pupil radiir0≤2 mm, the new metric predicts the equivalent sphere with similar accuracy (<0.1D), however, forr0>2 mm, the mean error of traditional metrics can increase beyond 0.25D, and the MTR remains accurate. The proposed metric allows clinicians to obtain an accurate clinical spherical equivalent value without rescaling/refitting of the wavefront coefficients. It has the potential to be developed into a metric which will be able to predict full spherocylindrical refraction for the desired illumination conditions and corresponding pupil size.

Corneal densitometry in patients with keratoconus undergoing intrastromal Ferrara ring implantation

2021 ◽  
pp. 112067212110206
Author(s):  
Pablo Felipe Rodrigues ◽  
Bernardo Kaplan Moscovici ◽  
Guilherme Ferrara ◽  
Luciano Lamazales ◽  
Marcela Mara Silva Freitas ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Medical Records ◽  
Spherical Equivalent ◽  
Interventional Study ◽  
Data Comparison ◽  
Corneal Densitometry ◽  
Corrected Visual Acuity ◽  
Ring Segment ◽  
The Mean

Objective: Evaluation of central corneal densitometry changes following Ferrara corneal ring segment implantation in patients with keratoconus, especially the correlation between corneal densitometry and keratometry. Methods: Retrospective, non-comparative, interventional study based on the review of medical records of patients diagnosed with keratoconus who underwent Ferrara corneal ring segment implantation. Pre and post-operative corneal densitometry measurements obtained with Pentacam HR (Oculus, Wetzlar, Germany) were analyzed. The follow-up time was 3 months, and data comparison was made, using specific statistical analysis, with the data of 3 months postoperatively. Results: The study sample consisted of 43 eyes of 36 patients. The mean corrected visual acuity improved from 0.82 LogMAR preoperatively (SD ± 0.33) to 0.19 LogMAR (SD ± 0.13) postoperatively. The mean spherical equivalent varied from −4.63 (SD ± 3.94) preoperatively to −2.16 (SD ± 2.63) postoperatively. Asphericity varied from −0.69 (SD ± 0.32) preoperatively to −0.27 (SD ± 0.31) postoperatively. The mean maximum K was 54.01D (SD ± 3.38) preoperatively and 51.50D (SD ± 2.90) postoperatively. The mean anterior densitometric value was 18.26 (SD ± 2.03) preoperatively and 17.66 (SD ± 1.84) postoperatively. Conclusion: Corneal densitometry is an interesting technology that should be studied in keratoconus patients. Our results suggest that the corneal densitometry in the cornea’s anterior layer reduces after ICRS implantation and correlates with corneal keratometry. Further studies should be performed to increase the knowledge in this field.

Outcomes of a 320-degree intrastromal corneal ring segment implantation for keratoconus: Results of a 6-month follow-up

2018 ◽  
Vol 30 (1) ◽  
pp. 139-146 ◽  
Author(s):  
Guilherme Andrade do Nascimento Rocha ◽  
Paulo Ferrara de Almeida Cunha ◽  
Leonardo Torquetti Costa ◽  
Luciene Barbosa de Sousa
Keyword(s):  
Visual Acuity ◽  
Spherical Equivalent ◽  
Distance Visual Acuity ◽  
Uncorrected Distance Visual Acuity ◽  
Intrastromal Corneal Ring ◽  
Corrected Distance Visual Acuity ◽  
Ring Segment ◽  
The Mean ◽  
Corneal Tomography

Importance: This study shows that a newer long-arc length intrastromal corneal ring segment is efficient and safe for keratoconus treatment. Background: To evaluate visual, tomographic results and complications of a 320-degree intrastromal corneal ring segment implantation with the femtosecond laser for keratoconus treatment. Design: A prospective, nonrandomized, and interventional study. Participants: A total of 34 eyes of 31 patients diagnosed with keratoconus were enrolled. Methods: Patients were divided into two groups based on the strategy used for 320-degree intrastromal corneal ring segment thickness selection. In one group, this selection was based on spherical equivalent (SE group) and in the other on the mean asphericity (Q group). The uncorrected and corrected distance visual acuities, spherical equivalent, K1, K2, Km, Kmax, and mean asphericity ( Q) on corneal tomography were evaluated preoperatively and at 3 and 6 months postoperatively. For astigmatism improvement, we analyzed the corneal tomographic vectorial astigmatism change preoperatively and at 6 months postoperatively. The mean follow-up period was 6.63 ± 0.96 months. Results: The mean uncorrected distance visual acuity and corrected distance visual acuity improved with a significant spherical equivalent improvement ( p < 0.05), with no differences between the 320-degree intrastromal corneal ring segment groups. All corneal tomographic parameters improved significantly ( p < 0.05) between the preoperative and postoperative intervals, with a significant better performance when we used spherical equivalent for the 320-degree intrastromal corneal ring segment thickness selection. Finally, the mean vectorial corneal tomographic astigmatism significantly improved after 6 months, again with no differences between groups. Conclusion: This study suggests that implanting a 320-degree intrastromal corneal ring segment is a safe and effective procedure for treating patients with keratoconus. It also suggests that for thickness selection spherical equivalent is the better strategy.

scholarly journals A calculator proposal for estimating refractive error after 3 years using the onset biometric values in primary school children: a cohort study

2021 ◽  
Author(s):  
Feride Tuncer Orhan ◽  
Haluk Huseyin Gürsoy
Keyword(s):  
Primary School ◽  
Anterior Chamber ◽  
Refractive Error ◽  
Axial Length ◽  
Anterior Chamber Depth ◽  
Primary School Children ◽  
Optical Parameters ◽  
Spherical Equivalent ◽  
Final Data ◽  
The Mean

Aim To evaluate consecutive measurements of the biometric parameters, age, and refraction error in a Turkish population at primary school age. Materials and Methods A total of 197 children aged between 7-12 years were included. The data of three consecutive measurements of children, who were examined at least once a year for three years using both cycloplegic auto-refractometry and optical biometry, were used in this retrospective study. Spherical equivalent <-0.50D was considered to be myopic; >+0.75D was considered to be hypermetropic. Age, gender, body mass index, spherical equivalent, axial length, anterior chamber depth, central corneal thickness, keratometry, and lens thickness were analyzed. The onset data obtained in 2013 whereas, the final data were from 2015. Logistic and Cox regression analyses were performed (p<0.05). Results The mean of the onset and the final spherical equivalents were 0.19D (0.56), and 0.08D (0.80), respectively. The myopia prevalence was increased among refractive errors in observation periods (univariable analysis p=0.029; multivariable analysis p=0.017). The onset axial length (HR:4.55, 95%CI:2.87-7.24, p<0.001), keratometry (HR:2.04, 95%CI:1.55-2.67, p<0.001) and age (HR:0.73, 95%CI: 0.57-0.92, p=0.009) correlated myopia progression. To calculate the estimated spherical equivalent, the onset data were included in the logistic regression model. The onset data of spherical equivalent (β=0.916, p<0.001), axial length (β=-0.451, p<0.001), anterior chamber depth (β=0.430, p=0.005) and keratometry (β=-0.172, p<0.001) were found to be significantly associated with the mean SE at the final data. Conclusions To calculate the estimated spherical equivalent following three years, an equation was proposed. The estimated refractive error of children can be calculated by using the proposed equation with the associated onset optical parameters.

scholarly journals Refractive Outcomes of  Table-Mounted and HandheldAuto-Refractometers in Children: An Observational Cross-Sectional Study

2021 ◽  
Author(s):  
müjdat karab ◽  
sinem karabulut ◽  
Aylin karalezli
Keyword(s):  
Cross Sectional Study ◽  
Spherical Equivalent ◽  
Sectional Study ◽  
Cross Sectional ◽  
Refractive Outcomes ◽  
Spearman's Rho ◽  
Spearman’S Rho ◽  
The Mean ◽  
Mean Differences ◽  
Cylinder Power

Abstract Background: To compare the refractive results of two autorefractors.Methods: We 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 reliability.Results: Nidek HandyRef-K autorefractor measured more astigmatism and myopia in terms of the mean cylindrical power (P<.001) and spherical equivalent (P=.024). Nidek HandyRef-K showed significantly more myopic results in subgroups with spherical power more than +1.50 Diopters (D) hyperopia and -3.00 D myopia (P=.031; P=.045; P=.026; respectively) and higher astigmatism in the subgroup with the cylindric power less than -1.00 D (P<.001). 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°. There was a strong correlation for spherical power (Spearman’s rho=0.99, P<.001), cylindrical power (Spearman’s rho=0.88, P<.001), spherical equivalent (Spearman’s rho=0.98, P<.001).Conclusion: Nidek HandyRef-K showed more myopic results regarding spherical equivalent and cylindrical power. Nidek HandyRef-K showed significantly more myopia in spherical power more than +1.50 D hyperopia, -3.00 D myopia, and more prominent astigmatism in cylindrical power less than -1.00 D subgroups.

scholarly journals Development of Refractive Parameters in 3- to 6-Year-Old Children and Its Application in Myopia Prediction and Intervention Guidance

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Ya Zhang ◽  
Ming Su ◽  
Hua Liu ◽  
Yanxia Song ◽  
Jing Liu ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Clinical Work ◽  
Hebei Province ◽  
Radius Of Curvature ◽  
Spherical Equivalent ◽  
Ocular Biometry ◽  
Refractive Development ◽  
Corneal Radius ◽  
The Mean ◽  
Vision Screener

Objective. To investigate refractive development and prevalence of myopia in children aged 3-6 years in Hebei Province, China, and to explore the developmental law of refraction, so as to clinically guide the prediction and intervention of myopia. Methods. In May 2019, a total of 6120 people were inspected in 68 kindergartens in 11 cities in Hebei Province. Child refractive refraction was checked under noncycloplegia using a handheld binocular vision screener (SW-800, SUOER, Tianjin, China). Axial length (AL) and corneal radius of curvature (CR) were measured using an ocular biometry (IOLMaster 500, Carl Zeiss, Germany). Myopia was defined as spherical equivalent SE ≤ − 0.75   D . Results. A total of 5506 children aged 3-6 years met the criteria and were included in the statistical analysis. The prevalence of myopia was 3.49% (1.93% at age 3, 2.90% at age 4, 3.78% at age 5, and 3.88% at age 6). Overall, the mean SE was + 0.67 ± 1.05   D ( + 0.81 ± 1.00   D at age 3, + 0.79 ± 1.05   D at age 4, + 0.67 ± 1.08   D at age 5, and + 0.13 ± 1.01   D at age 6); the mean CR was 7.76 ± 0.26   mm ( 7.78 ± 0.26   mm at age3, 7.75 ± 0.25   mm at age 4, 7.77 ± 0.26   mm at age 5, and 7.76 ± 0.25   mm at age 6); the mean AL was 22.31 ± 0.73   mm ( 21.98 ± 0.63   mm at age 3, 22.12 ± 0.69   mm at age 4, 22.34 ± 0.73   mm at age 5, and 22.49 ± 0.73   mm at age 6). Conclusions. Prevalence of myopia increases with age in children aged 3-6 years in Hebei, China. With the increase of age, CR is basically stable, and AL increases gradually. AL/CR, which is closely related to SE, can be used as an indicator to predict myopia and guide clinical work.

Effects of Orthokeratology Lens On Axial Length Elongation in Myopia With Anisometropia Children

2021 ◽  
Author(s):  
Ziyang Chen ◽  
Kai-Ming Chen ◽  
Ying Shi ◽  
Zhao-Da Ye ◽  
Sheng Chen ◽  
...  
Keyword(s):  
Retrospective Study ◽  
Axial Length ◽  
Statistical Significance ◽  
Spherical Equivalent ◽  
Significant Difference ◽  
The Mean ◽  
The Difference ◽  
Better Than ◽  
Group 1

Abstract AimTo investigate the effect of orthokeratology (OK) lens on axial length (AL) elongation in myopia with anisometropia children.MethodsThirty-seven unilateral myopia (group 1) and fifty-nine bilateral myopia with anisometropia children were involved in this 1-year retrospective study. And bilateral myopia with anisometropia children were divided into group 2A (diopter of the lower SER eye under − 2.00D) and group 2B(diopter of the lower SER eye is equal or greater than − 2.00D). The change in AL were observed.The datas were analysed using SPSS 21.0.Results(1) In group 1, the mean baseline AL of the H eyes and L eye were 24.70 ± 0.89 mm and 23.55 ± 0.69 mm, respectively. In group 2A, the mean baseline AL of the H eyes and L eyes were 24.61 ± 0.84 mm and 24.00 ± 0.70 mm respectively. In group 2B, the mean baseline AL of the H eyes and L eyes were 25.28 ± 0.72 mm and 24.70 ± 0.74 mm. After 1 year, the change in AL of the L eyes was faster than the H eyes in group 1 and group 2A (all P<0.001).While the AL of the H eyes and L eyes had the same increased rate in group 2B. (2) The effect of controlling AL elongation of H eyes is consistent in three groups (P = 0.559).The effect of controlling AL elongation of L eyes in group 2B was better than that in group 1 and group 2A (P < 0.001). And the difference between group 1 and group 2A has no statistical significance. (3) The AL difference in H eyes and L eyes decreased from baseline 1.16 ± 0.55mm to 0.88 ± 0.68mm after 1 year in group 1.And in group 2A, the AL difference in H eyes and L eyes decreased from baseline 0.61 ± 0.34mm to 0.48 ± 0.28mm. There was statistically significant difference (all P<0.001). In group 2B, the baseline AL difference in H eyes and L eyes has no significant difference from that after 1 year (P = 0.069).ConclusionsMonocular OK lens is effective on suppression AL growth of the myopic eyes and reduce anisometropia value in unilateral myopic children. Binocular OK lenses only reduce anisometropia with the diopter of the low eye under − 2.00D. Binocular OK lenses cannot reduce anisometropia with the diopter of the low eye equal or greater than − 2.00D. Whether OK lens can reduce refractive anisometropia value is related to the spherical equivalent refractive of low refractive eye in bilateral myopia with anisometropia children after 1-year follow-up.

Topical atropine in retarding myopia progression and axial length growth in children with myopia

2020 ◽  
Vol 13 (4) ◽  
pp. 111-114
Author(s):  
Abdur Rahman Mohammad Alam ◽  
Md. Sanwar Hossain ◽  
Md. Shafiqul Islam
Keyword(s):  
Axial Length ◽  
Control Group ◽  
Refractive Errors ◽  
Spherical Equivalent ◽  
Myopia Progression ◽  
Length Growth ◽  
Significant Difference ◽  
The Mean ◽  
And Control

This study was conducted to observe the effect of atropine in retarding myopia progression and axial length growth in 36 myopic children (atropine group, 24; control, 12). The initial spherical equivalent of the atropine group and control group was -3.0 ± 1.6 dioptre and -3.5 ± 1.6 dioptre respectively. At the 12th month in atropine group, it was -2.9 ± 2.6 dioptre and -4.6 ± 1.9 dioptre in the control group. The power of the atropine group reduced but rose in the control group after 12 months. There was a statistically significant difference in final refractive errors between the two groups (p<0.05). The initial axial length of the atropine group and control group was 24.3± 1.0 mm and 24.6 ± 1.1 mm respectively. In 12th month, the changes in axial length in the two groups was insignificant. However, the mean axial length progression at 12 months of the atropine group was -0.1 ± 0.1 mm and it was lower than the control group which was -0.2 ± 0.2 mm, and this was statistically significant (p<0.05). In conclusion, topical atropine (0.01%) retarded myopia progre-ssion and axial length growth in myopic children.    

scholarly journals The Role of Axial Length-Corneal Radius of Curvature Ratio in Refractive State Categorization in a Nigerian Population

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Eghosasere Iyamu ◽  
Joy Iyamu ◽  
Christian Izuchukwu Obiakor
Keyword(s):  
Axial Length ◽  
Inverse Correlation ◽  
Radius Of Curvature ◽  
Spherical Equivalent ◽  
Refractive State ◽  
Spherical Equivalent Refraction ◽  
Nigerian Population ◽  
Corneal Radius ◽  
The Mean

The aim of this study was to investigate the association of axial length (AL)/corneal radius of curvature (CRC) ratio (AL/CRC) with spherical equivalent refractive state (SER) in young adults. A total of seventy () subjects consisting of 31 males and 39 females participated in this study. Subjects were categorized into emmetropia, hyperopia and myopia using the spherical equivalent refraction. The axial length was measured with I-2100 A-Scan ultrasonography/Biometer (CIMA Technology, USA), the corneal radius of curvature with Bausch & Lomb H-135A (Bausch & Lomb Corp., USA), and the refractive state by static retinoscopy and subjective refraction. The mean AL, CRC and AL/CRC ratio of all subjects were 23.74 ± 0.70 mm, 7.84 ± 0.19 mm, and 3.03 ± 0.14, respectively. Myopes had significantly longer AL, steeper CRC and higher AL/CRC ratio than the emmetropes and hyperopes. There was statistically significant inverse correlation between AL and CRC (, ), SER (, ), and between SER and AL/CRC (, ). A significant positive correlation was found between CRC and SER (, ). The categorization of the refractive state of an individual is better done by using the AL/CRC ratio index.

scholarly journals Pupil Function in Pseudophakia: Proximal Miosis Behavior and Optical Influence

Photonics ◽  
2019 ◽  
Vol 6 (4) ◽  
pp. 114 ◽  
Author(s):  
Elsa Fonseca ◽  
Paulo Fiadeiro ◽  
Renato Gomes ◽  
Angel Sanchez Trancon ◽  
António Baptista ◽  
...  
Keyword(s):  
Pupil Size ◽  
Angular Size ◽  
Optical Quality ◽  
Individual Variability ◽  
Computer Simulation Model ◽  
Small Contribution ◽  
Distant Object ◽  
Object Distance ◽  
The Mean ◽  
The Impact

The pseudophakic eye lacks the ability to produce a refractive change in response to object proximity. Thus, individual anatomical features such as the pupil size play an important role in achieving functional vision levels. In this work, the range of pupil sizes at varying object distance was measured in pseudophakic participants. Furthermore, the impact of the measured values on eye optical quality was investigated using a computer simulation model. A binocular eye-tracker was used to measure the participants’ pupil sizes at six object distances, ranging from 0.33 m (i.e., vergence of 3.00 D) to 3.00 m (i.e., vergence of 0.33 D), while observing a Maltese cross with a constant angular size of 1 ∘ . In total, 58 pseudophakic participants were enrolled in this study (age mean ± standard deviation: 70.5 ± 11.3 years). The effects of object distance and age on pupil size variation were investigated using linear mixed effects regression models. Age was found to have a small contribution to individual variability. The mean infinite distance pupil size (intercept) was 4.45 ( 95 % CI: 2.74, 6.17) mm and the mean proximal miosis (slope) was − 0.23 ( 95 % CI: −0.53, 0.08) mm/D. The visual acuity (VA) estimation for a distant object ranged from − 0.1 logMAR (smallest pupil) to 0.04 logMAR (largest pupil) and the near VA ( 0.33 m) when mean proximal miosis was considered ranged from 0.28 logMAR (smallest pupil) to 0.42 logMAR (largest pupil). When mean distance pupil was considered, proximal miosis individual variability produced a variation of 0.04 logMAR for the near object and negligible variation for the distant object. These results support the importance of distance pupil size measurement for the prediction of visual performance in pseudophakia, while suggesting that proximal miosis has a negligible impact in VA variability.

Effect of migraine attack on pupil size, accommodation and ocular aberrations

2020 ◽  
pp. 112067212097533
Author(s):  
Merve Beyza Yildiz ◽  
Elvin Yildiz ◽  
Sevcan Balci ◽  
Buse Rahime Hasirci Bayir ◽  
Yılmaz Çetinkaya
Keyword(s):  
Migraine Attack ◽  
Pupil Size ◽  
Case Control Study ◽  
Case Control ◽  
Healthy Controls ◽  
Unilateral Headache ◽  
Significant Difference ◽  
The Mean ◽  
Control Study ◽  
Prospective Case Control Study

Purpose: To evaluate the pupil size, accommodation, and ocular higher-order aberrations (HOAs) in patients with migraine during migraine attacks and compare them with interictal period and healthy controls. Methods: This prospective, case–control study included 48 eyes of 24 patients with migraine and 48 eyes of 24 age and sex-matched healthy controls. Measurements were performed using a Hartmann Shack aberrometer. Accommodative responses to accommodative stimulus ranging from 0 to 5 diopters (D) in increments of 0.5 D were recorded. Spherical, coma, trefoil aberration, and root mean square (RMS) of total HOAs were assessed. Patients with migraine were measured twice during the interictal phase and during migraine attack. Results: The mean pupil size significantly decreased during migraine attack (5.85 ± 0.19 mm) compared with the interictal phase (6.05 ± 0.19 mm) in the patients with migraine ( p = 0.012). There was a significant increase in the accommodative response to accommodative stimulus of 1.5 to 5 D during migraine attack. No significant change was observed in HOAs during migraine attack. In addition, no ictal or interictal period measurements were statistically significantly different from the controls. Comparing symptomatic and non-symptomatic sides in 17 migraine patients with unilateral headache, no significant difference was found in any of the measurements in both ictal and interictal periods. Conclusion: Our results suggest the presence of a subtle oculosympathetic hypofunction in patients with migraine during the ictal period compared to the interictal period. The accommodation status of the eye seems to be affected by this autonomic dysfunction.

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