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Modelling eye lengths and refractions in the periphery.

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Title: Modelling eye lengths and refractions in the periphery.
Authors: Ramamirtham, Ramkumar (AUTHOR), Akula, James D. (AUTHOR), Curran, Amber‐Lee K. (AUTHOR), Szczygiel, Justyna (AUTHOR), Lancos, Annie M. (AUTHOR), Grytz, Rafael (AUTHOR), Ferguson, R. Daniel (AUTHOR), Fulton, Anne B. (AUTHOR)
Source: Ophthalmic & Physiological Optics. Jul2023, Vol. 43 Issue 4, p815-826. 12p. 1 Diagram, 2 Charts, 5 Graphs.
Subjects: Visual accommodation, Crystalline lens, Refractive errors, Ray tracing, Refractive index
Abstract: Purpose: To create a simplified model of the eye by which we can specify a key optical characteristic of the crystalline lens, namely its power. Methods: Cycloplegic refraction and axial length were obtained in 60 eyes of 30 healthy subjects at eccentricities spanning 40° nasal to 40° temporal and were fitted with a three‐dimensional parabolic model. Keratometric values and geometric distances to the cornea, lens and retina from 45 eyes supplied a numerical ray tracing model. Posterior lens curvature (PLC) was found by optimising the refractive data using a fixed lens equivalent refractive index (neq). Then, neq was found using a fixed PLC. Results: Eccentric refractive errors were relatively hyperopic in eyes with central refractions ≤−1.44 D but relatively myopic in emmetropes and hyperopes. Posterior lens power, which cannot be measured directly, was derived from the optimised model lens. There was a weak, negative association between derived PLC and central spherical equivalent refraction. Regardless of refractive error, the posterior retinal curvature remained fixed. Conclusions: By combining both on‐ and off‐axis refractions and eye length measurements, this simplified model enabled the specification of posterior lens power and captured off‐axis lenticular characteristics. The broad distribution in off‐axis lens power represents a notable contrast to the relative stability of retinal curvature. [ABSTRACT FROM AUTHOR]
Copyright of Ophthalmic & Physiological Optics is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Psychology and Behavioral Sciences Collection
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  Data: Modelling eye lengths and refractions in the periphery.
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  Data: <searchLink fieldCode="AR" term="%22Ramamirtham%2C+Ramkumar%22">Ramamirtham, Ramkumar</searchLink> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Akula%2C+James+D%2E%22">Akula, James D.</searchLink> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Curran%2C+Amber‐Lee+K%2E%22">Curran, Amber‐Lee K.</searchLink> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Szczygiel%2C+Justyna%22">Szczygiel, Justyna</searchLink> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Lancos%2C+Annie+M%2E%22">Lancos, Annie M.</searchLink> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Grytz%2C+Rafael%22">Grytz, Rafael</searchLink> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Ferguson%2C+R%2E+Daniel%22">Ferguson, R. Daniel</searchLink> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Fulton%2C+Anne+B%2E%22">Fulton, Anne B.</searchLink> (AUTHOR)
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  Data: <searchLink fieldCode="JN" term="%22Ophthalmic+%26+Physiological+Optics%22">Ophthalmic & Physiological Optics</searchLink>. Jul2023, Vol. 43 Issue 4, p815-826. 12p. 1 Diagram, 2 Charts, 5 Graphs.
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  Data: <searchLink fieldCode="DE" term="%22Visual+accommodation%22">Visual accommodation</searchLink><br /><searchLink fieldCode="DE" term="%22Crystalline+lens%22">Crystalline lens</searchLink><br /><searchLink fieldCode="DE" term="%22Refractive+errors%22">Refractive errors</searchLink><br /><searchLink fieldCode="DE" term="%22Ray+tracing%22">Ray tracing</searchLink><br /><searchLink fieldCode="DE" term="%22Refractive+index%22">Refractive index</searchLink>
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  Data: Purpose: To create a simplified model of the eye by which we can specify a key optical characteristic of the crystalline lens, namely its power. Methods: Cycloplegic refraction and axial length were obtained in 60 eyes of 30 healthy subjects at eccentricities spanning 40° nasal to 40° temporal and were fitted with a three‐dimensional parabolic model. Keratometric values and geometric distances to the cornea, lens and retina from 45 eyes supplied a numerical ray tracing model. Posterior lens curvature (PLC) was found by optimising the refractive data using a fixed lens equivalent refractive index (neq). Then, neq was found using a fixed PLC. Results: Eccentric refractive errors were relatively hyperopic in eyes with central refractions ≤−1.44 D but relatively myopic in emmetropes and hyperopes. Posterior lens power, which cannot be measured directly, was derived from the optimised model lens. There was a weak, negative association between derived PLC and central spherical equivalent refraction. Regardless of refractive error, the posterior retinal curvature remained fixed. Conclusions: By combining both on‐ and off‐axis refractions and eye length measurements, this simplified model enabled the specification of posterior lens power and captured off‐axis lenticular characteristics. The broad distribution in off‐axis lens power represents a notable contrast to the relative stability of retinal curvature. [ABSTRACT FROM AUTHOR]
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  Data: <i>Copyright of Ophthalmic & Physiological Optics is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.1111/opo.13133
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        Text: English
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      – SubjectFull: Visual accommodation
        Type: general
      – SubjectFull: Crystalline lens
        Type: general
      – SubjectFull: Refractive errors
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      – SubjectFull: Ray tracing
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      – SubjectFull: Refractive index
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      – TitleFull: Modelling eye lengths and refractions in the periphery.
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              M: 07
              Text: Jul2023
              Type: published
              Y: 2023
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