Internal Astigmatism in Myopes and Non-myopes: Compensation or Constant?

Manny, Ruth E.; Deng, Li; Gwiazda, Jane; Hyman, Leslie; Weissberg, Erik; Scheiman, Mitchell; Fern, Karen D.

doi:10.1097/opx.0000000000000946

Cited by 10 publications

(6 citation statements)

References 29 publications

(72 reference statements)

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“…It is convinced that AL can explain up to 96% of the variation of refraction in populations [18]. Subsquently, the IA was greater in population with shorter AL in Manny's study which is consistent with our finding [17]. Moreover, our results is also confirmed with another Chinese study that a larger IA is more prevalent with less myopia and greater corneal astigmatism [19].…”

Section: Discussionsupporting

confidence: 92%

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Age-dependent Distribution of Astigmatism and its Component in Chinese Preschool Children

Chen

Dai

Sun

2019

Preprint

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Background: There is an compensatory effect between corneal astigmatism (CA) and internal astigmatism (IA). And the refractive astigmatism (RA) decreased fast in the early 3 years. Nevertheless, little attention was paid to the change in astigmatism in preschool children. Thus, we aimed to investigate the age-dependent distribution of astigmatism and its component in Chinese preschool children from year 3 to year 6 and also, to study the relationship between ocular biometry and IA. Methods: Automated refraction, keratometry and axial length (AL) were performed in this cross-sectional study. The IA was determined as the vector difference between RA and CA. The magnitude and type (with-the-rule WTR, against-the-rule ATR, oblique) of RA, CA and IA were investigated according to the age. Spearman correlation was adopted to detect the factors that may influence IA. Results: A total of 2315 subjects (2315 right eyes) (47.38% female) with a mean age of 4.52±0.88 years (range 3-6 years) were included. The magnitude and the ratio of three kinds of CA components did not change with aging (p=0.1233 and p>0.1, respectively). Though the axial distribution of RA remained unchanged with aging, a significant reduction in RA was seen in year 6 compared to that of year 3 and year 4 (p=0.036 and 0.041, respectively). Conversely，the ATR component in IA was lower in year 6 (68.02%) than it in year 3 (81.92%) and year 4 (77.12%) (both p<0.001) accompanied by increased frequency of oblique astigmatism in year 6 than it in year 3 and year 4 (p<0.001 and p=0.012,respectively). Negative relationship was found between IA and AL. Conclusion: RA decreased from year 3 to year 6. The shift of the axis in IA from ATR to Oblique and WTR may account for the reduction in RA. Eyes with shorter AL had larger IA. Keywords: Internal astigmatism; corneal astigmatism; axial length; with-the-rule.

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Section: Discussionsupporting

confidence: 92%

“…In contrast to previous conclusions [16], IA was observed to be negatively associated with AL in our study. And another study showed J0 component of IA was greater in the non-myopes compared to the Myopes [17]. It is convinced that AL can explain up to 96% of the variation of refraction in populations [18].…”

Section: Discussionmentioning

confidence: 96%

Age-dependent Distribution of Astigmatism and its Component in Chinese Preschool Children

Chen

Dai

Sun

2019

Preprint

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“…To indicate whether ORA can reduce TA by counterbalancing CA, a compensation factor (CF) was adopted in the current study, defined as CF = 1 –TA / CA [ 24 , 25 ]. In this formula, TA and CA are absolute values.…”

Section: Methodsmentioning

confidence: 99%

Ocular residual and corneal astigmatism in a clinical population of high school students

et al. 2018

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PurposeTotal refractive astigmatism is usually the first consideration that guides the selection of contact lens type (e.g., spherical or toric), while the ocular source of the astigmatism is a second, but more important consideration, for the final clinical decision. This study was conducted to provide detailed data on this topic by evaluating astigmatic components in Chinese adolescents.MethodsParticipants were recruited from healthy high school students undergoing an annual ocular examination at a local hospital. Total astigmatism (TA), corneal astigmatism (CA), and ocular residual astigmatism (ORA) were determined by a Hartmann-Shack wavefront analyzer system (KR-1W, Topcon) with the natural pupil. The axis relationship between CA and ORA was placed into three categories: on-axis, defined as an axis with a difference of 0 ± 10°; opposite-axis, a difference of 90 ± 10°; and the rest defined as oblique-axis.ResultsThe study consisted of 1,466 students (57.84% girls, age: 16.49 ± 1.05 years). ORA was present in 83.97%, 66.64%, and 45.23% of participants, according to the various criteria for astigmatism (≥ 0.50 D, ≥ 0.75 D, and ≥ 1.00 D, respectively). While with-the-rule was the most common axis orientation for both TA (76.28%) and CA (89.94%), against-the-rule predominated in ORA (93.82%; χ2 = 1688.544, p < 0.001). Opposite-axis was the major type of axis difference (90.96%) of clinical significance (i.e., ≥ 1.00 D) between CA and ORA, which also prevailed in all levels of TA (range: 56.25–82.26%).ConclusionsORA is common in high school students and usually demonstrates a compensation relationship with CA, which should be taken into consideration when determining the design of contact lenses to correct refractive error.

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“…The ISCAN eye movement tracking system has a resolution of 0.1° with a linear range of 3% for horizontal movements from ±25°. Our prior studies have analyzed linearity and report a Pearson correlation coefficient of r > 0.9 for our calibrations 45 . Our prior studies also show a high interclass correlation coefficient of >0.7 when assessing eye movements within and between experimental trials 46 – 48 .…”

Section: Methodsmentioning

confidence: 98%

Adaptation to Progressive Additive Lenses: Potential Factors to Consider

Alvarez

Kim

Granger-Donetti

2017

Sci Rep

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People develop presbyopia as part of the normal aging process. Most presbyopes adapt to progressive additive lens (PALs), while others do not. This investigation sought to determine whether the ability to modify disparity vergence or phoria was correlated to PALs adaptation. In experiment 1, a double-step paradigm quantified the ability to modify convergence responses in sixteen presbyopes. In experiment 2, thirty-one incipient presbyopes participated in a 5-minute sustained fixation task to evoke phoria adaptation where the magnitude and rate of phoria adaptation were measured. Then, the experiment was repeated after wearing PALs for one month. Linear regression analyses were conducted between the following parameters: near point of convergence, positive fusional vergence at near, vergence facility, net change in the magnitude of phoria adaptation, and the rate of phoria adaptation. The ability to change convergence average peak velocity was significantly greater (p < 0.03) in presbyopic PALs adapters compared to presbyopic PALs non-adapters. The rate of phoria adaptation and vergence facility were significantly greater (p < 0.03) in incipient presbyopic PALs adapters compared to incipient presbyopic PALs non-adapters. Vergence facility and the rate of phoria adaptation may have potential clinical utility in differentiating which patients may adapt to PALs and which ones will have more difficulty.

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Internal Astigmatism in Myopes and Non-myopes: Compensation or Constant?

Cited by 10 publications

References 29 publications

Age-dependent Distribution of Astigmatism and its Component in Chinese Preschool Children

Age-dependent Distribution of Astigmatism and its Component in Chinese Preschool Children

Ocular residual and corneal astigmatism in a clinical population of high school students

Adaptation to Progressive Additive Lenses: Potential Factors to Consider

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