Optical characteristics of Alvarez variable‐power spectacles

Radhakrishnan, Hema; Charman, W. N.

doi:10.1111/opo.12361

Cited by 10 publications

(7 citation statements)

References 47 publications

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“…Monocular spherocyclindrical refractive errors were measured using a novel self‐refraction method (SfR) that used adjustable glasses (AdLens, AdLens Ltd) mounted in a ring holder (Figure ). In contrast to the original formulation by Alvarez, it was recently shown that these lenses have a moderate amount of astigmatism in the central optical area and it is therefore possible to separate different meridians of interest.…”

Section: Methodsmentioning

confidence: 92%

Self‐assessment of refractive errors using a simple optical approach

Leube

Kraft

Ohlendorf

et al. 2018

Clinical and Experimental Optometry

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BackgroundThis explorative study investigated procedures for the self‐assessment of spherocylindrical refractive errors.MethodsEighteen participants with a mean age of 34.0 ± 8.8 years were enrolled. Adjustable Alvarez lenses were mounted in a rotatable ring holder and two procedures were tested for the self‐adjustment: (1) rotation of the lens in three meridians: 0°, 60° and 120° and (2) rotation of the optotypes in the same meridians. Starting from maximum positive power, the participants were required to decrease the power of the Alvarez lens until the optotypes (0.0 logMAR) appeared to be clear the first time. Best‐corrected visual acuity (BVA) was measured using a psychophysical staircase procedure. Bland–Altmann analysis was carried out in order to calculate the limits of agreement between the self‐refraction method and the standard subjective refraction.ResultsUsing procedure 1, 77 per cent of the subjects achieved a VA ≥ 0.1 logMAR (6/7.5) and the same was true for 88 per cent of the subjects using procedure 2. Using procedure 1, a significantly worse BVA was found, when compared to subjective refraction (ΔVA = −0.15 logMAR, F3,140 = 7.11, p = 0.046, median test). Analysis of variance (ANOVA) analysis showed a significant influence of the refraction method on the oblique astigmatism component J45 but not for the spherical equivalent M and the straight astigmatism component J0 (M: F3,140 = 0.532, p = 0.661; J0: F3,140 = 0.056, p = 0.983; J45: F3,140 = 13.97, p < 0.001; ANOVA). The limits of agreement for the spherical equivalent error M were ± 1.10 D and ± 1.20 D and for the astigmatic components J0 ± 0.78 D and ± 0.59 D and for J45 ± 0.62 D and ± 0.54 D, for procedure 1 and procedure 2, respectively.ConclusionsFixed adjustable Alvarez lenses and rotatable stimuli can provide a fast and precise self‐assessment method to measure the spherocylindrical error of the eye.

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Section: Methodsmentioning

confidence: 92%

Self‐assessment of refractive errors using a simple optical approach

Leube

Kraft

Ohlendorf

et al. 2018

Clinical and Experimental Optometry

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“…In an interesting paper, Barbero & Portilla explore the way in which power and magnification are linked in progressive addition lenses (PALs) and consider their results in relation to the problems of distortion and blur experienced by some wearers of such lenses. Radhakrishnan & Charman present measurements of the optical performance of examples of some current commercial variable‐power spectacles and conclude that these might be useful to at least some presbyopes.…”

Section: Methods Of Correctionmentioning

confidence: 99%

Virtual Issue Editorial: Presbyopia – grappling with an age‐old problem

Charman

2017

Ophthalmic Physiologic Optic

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“…24 The oblique astigmatism of the eye also has a major impact upon the blur patterns on the peripheral retina when the visual axis is directed through the lens centre. The typical oblique astigmatism of the eye rises from about 1 D at a field angle of 20 degrees to around 2.5 D at 40 degrees, 25 thereby introducing corresponding additional spherical and cylindrical blur. Nevertheless, Figure 2b would be expected to give a reasonable prediction of the general features of the images.…”

Section: Key Pointsmentioning

confidence: 99%

Multiple segment spectacle lenses for myopia control. Part 1: Optics

Radhakrishnan

Lam

Charman

2023

Ophthalmic Physiologic Optic

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PurposeTo understand and compare the optics of two multiple segment (MS) spectacle lenses (Hoya MiyoSmart and Essilor Stellest) designed to inhibit myopia progression in children.MethodsThe optics of the two designs are presented, together with geometrical optics‐based calculations to understand the impact of the lenses on the optics of the eye. Lenses were evaluated with three techniques: surface images, Twyman–Green interferometry and focimetry. The carrier lens powers and the spatial distribution, powers and forms of the lenslets were measured.ResultsMS lenses as manufactured were found to match most of the design specifications provided by their manufacturers, although some apparent small discrepancies were found. The focimeter‐measured power of the lenslets was approximately +3.50 D for the MiyoSmart and +4.00 D for the highly aspheric lenslets of the Stellest design. For both lens designs, image contrast would be expected to become modestly reduced in the focal planes of the distance‐correcting carrier lenses. Images become much more degraded in the combined carrier‐lenslet focal plane, due to the generation of multiple laterally displaced images formed by adjacent lenslets within the effective pupil. The exact effects observed depended on the effective pupil size and its location with respect to the lenslets, as well as the power and arrangement of the lenslets.ConclusionWearing either of these lenses will produce broadly similar effects on retinal imagery.

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Optical characteristics of Alvarez variable‐power spectacles

Abstract: Within their designed power ranges, optical performance of currently-available Alvarez variable-power spectacles appears to be adequate to correct the distance and near vision of spherical ametropes.

Cited by 10 publications

References 47 publications

Self‐assessment of refractive errors using a simple optical approach

Self‐assessment of refractive errors using a simple optical approach

Virtual Issue Editorial: Presbyopia – grappling with an age‐old problem

Multiple segment spectacle lenses for myopia control. Part 1: Optics

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