- •This study presents new data on refractive error components: corneal, refractive and internal astigmatism, in a group of young UK based adults.
- •A weak, but significant correlation is noted for both axial length and MSE, with both internal and refractive (total) astigmatic components of J45, i.e. oblique astigmatism.
There is a clear benefit in defining internal (IA) and corneal astigmatic error (CA) prior to surgical and other refractive interventions, such as orthokeratology, to minimise risk of unsatisfactory refractive outcomes. Such data would also be of relevance to broader areas of ophthalmic care such as spectacle dispensing and other types of rigid lens fitting. This study offers a detailed characterisation of astigmatic error in a group of university students and specifically investigates compensation of corneal astigmatism by the eye’s internal optics.
For 176 young-adult participants, objective measurements of refractive error were obtained using the open-view Grand Seiko WAM-5500 autorefractor; corneal curvature and axial length were measured using the Aladdin biometer. Clinical measurements of corneal and refractive astigmatism were converted into vector components J0 and J45; followed by an assessment of corneal astigmatism compensation.
Mean total refractive astigmatism (RA), CA, and IA were 0.24 ± 0.32D, 0.46 ± 0.27D and -0.21 ± 0.25D respectively for J0 and -0.05 ± 0.20D, 0.01 ± 0.16D, and -0.06 ± 0.18D for J45. Significant linear correlations were noted between RA, CA, and IA for both J0 and J45 (P < 0.01). A significant linear regression was also noted between axial length and J45 RA and IA, but not CA. Levels of full compensation were low, 7% and 9% for J0 and J45 respectively, however, a complete absence of compensation was also uncommon particularly for J45 (2%).
In general, partial compensation for corneal astigmatism by the eye’s internal optics is noted, but it is unclear whether this is an active compensatory mechanism. Further, larger scale, studies would be required to characterise differences in corneal astigmatic compensation with respect to ethnicity.
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- Predicting ocular residual astigmatism using corneal and refractive parameters: a myopic eye study.Curr Eye Res. 2013; 38: 851-861
- Ocular residual and corneal astigmatism in a clinical population of high school students.PLoS One. 2018; 13e0194513
- International survey of orthokeratology contact lens fitting.Contact Lens Anterior Eye. 2019; 42: 450-454
- Internal astigmatism in Myopes and non-myopes: compensation or constant?.Optom Vis Sci. 2016; 93: 1079-1092
- Power vectors: an application of Fourier analysis to the description and statistical analysis of refractive error.Optom Vis Sci. 1997; 74: 367-375
- Evaluation of internal refraction with the optical path difference scan.Ophthalmology. 2008; 115: 57-66
- Evaluating internal and ocular residual astigmatism in Chinese myopic children.Jpn J Ophthalmol. 2017; 61: 494-504
- Astigmatism in Bangladeshi and white school entrants in East London: a prospective comparative study.Eye. 1995; 9: 794-796
- Cross-sectional and longitudinal investigation of the power vector in astigmatism: the Yamagata study (Funagata).Cornea. 2018; 37: 53-58
- Correlation of major components of ocular astigmatism in myopic patients.Contact Lens Anterior Eye. 2016; 39 (Artal et al): 20-25
- Ethnicity-specific prevalences of refractive errors vary in Asian children in neighbouring Malaysia and Singapore.Br J Ophthalmol. 2006; 90: 1230-1235
- Ethnic differences in refraction and ocular biometry in a population-based sample of 11–15-year-old Australian children.Eye. 2008; 22: 649
- Parameters associated with the different astigmatism axis orientations.Invest Ophthalmol Vis Sci. 2010; 51: 723-730
- Corneal and refractive astigmatism in adults: a power vectors analysis.Optom Vis Sci. 2009; 86: 1182-1186
- Astigmatism and its components in 6-year-old children.Invest Ophthalmol Vis Sci. 2006; 47: 55-64
- Power vector analysis of refractive, corneal and lenticular astigmatism in an elderly chinese population: the shihpai eye study.Invest Ophthalmol Vis Sci. 2011; 52: 2514-
- Clinical applications of power vectors.Optom Vis Sci. 2009; 86: 599-602
- A study of the axis of orientation of residual astigmatism.Acta ophthalmologica. 1994; 72: 483-489
- A remote subjective refractor employing continuously variable sphere-cylinder corrections.Opt Eng. 1976; 154286
- A system matrix for astigmatic optical systems: II. Corrected systems including an astigmatic eye.Optom Vis Sci. 1981; 58: 919-929
- Squaring the sphero‐cylinder, the equivalent of squaring the refractive power matrix.Ophthalmic Physiol Opt. 1988; 8: 458-459
- Astigmatic decomposition: an alternative subjective refraction test employing conventional instrumentation.Ophthalmic Physiol Opt. 1984; 4: 359-364
- Internal astigmatism and its role in the growth of axial length in school-age children.J Ophthalmol. 2018; (2018)
- Astigmatism in 12-year-old Australian children: comparisons with a 6-year-old population.Invest Ophthalmol Vis Sci. 2007; 48: 73-82
- Clinical optics and refraction: a guide for optometrists, contact lens opticians and dispensing opticians.Elsevier health sciences. 2007
- Corneal and lenticular components of total astigmatism in a preschool sample.Optom Vis Sci. 2004; 81: 536-542
- Incidence and progression of astigmatism in Singaporean children.Invest Ophthalmol Vis Sci. 2004; 45: 3914-3918
- Prevalence of astigmatism in 6-to 72-month-old african american and hispanic children: the multi-ethnic pediatric eye disease study.Ophthalmology. 2011; 118: 284-293
- Corneal and refractive error astigmatism in Singaporean schoolchildren: a vector-based Javal’s rule.Optom Vis Sci. 2001; 78: 881-887
Published online: February 22, 2020
Accepted: February 12, 2020
Received in revised form: December 4, 2019
Received: May 22, 2019
© 2020 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.