Author:
Kaye Stephen B.,Surti Jamila,Wolffsohn James S.
Abstract
AbstractTo provide a solution for average paraxial lens power (ApP) of a lens. Orthogonal and oblique sections through a lens of power $$F$$
F
were reduced to a paraxial representation of lens power followed by integration. Visual acuity was measured using lenses of different powers (cylinders of − 1.0 and − 2.0D) and axes, mean spherical equivalent (MSE) of S + C/2, ApP and a toric correction, with the order of correction randomised. A digital screen at 6 m was used on which a Landolt C with crowding bars was displayed for 0.3 s before vanishing. The general equation for a symmetrical lens of refractive index (n), radius of curvature R, in medium of refractive index n1, through orthogonal ($$\theta$$
θ
) and oblique meridians ($$\gamma$$
γ
) as a function of the angle of incidence ($$\alpha$$
α
) reduces for paraxial rays ($$\alpha \sim 0$$
α
∼
0
) to $$F_{n,R} \left( {\alpha ,\theta ,\gamma } \right)\left. \right|_{\alpha \sim 0} = \frac{{n - n_{1} }}{R}\cos^{2} \theta \cos^{2} \gamma$$
F
n
,
R
α
,
θ
,
γ
α
∼
0
=
n
-
n
1
R
cos
2
θ
cos
2
γ
. The average of this function is $$F_{n,R} \left( {\alpha ,\theta ,\gamma } \right)\left. \right|_{\alpha \sim 0} = \frac{{n - n_{1} }}{4R} $$
F
n
,
R
α
,
θ
,
γ
α
∼
0
=
n
-
n
1
4
R
providing a solution of $$\frac{F}{4}$$
F
4
for ApP.For central (p = 0.04), but not peripheral (p = 0.17) viewing, correction with ApP was associated with better visual acuity than a MSE across all tested refractive errors (p = 0.04). These findings suggest that $$\frac{F}{4}$$
F
4
may be a more inclusive representation of the average paraxial power of a cylindrical lens than the MSE.
Publisher
Springer Science and Business Media LLC
Cited by
3 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献