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Prentice's rule, named so after the optician Charles F. Prentice, is a formula used to determine the amount of induced prism in a lens: = where: P is the amount of prism correction (in prism dioptres) c is decentration (the distance between the pupil centre and the lens's optical centre, in millimetres)
The prism cover test ( PCT) is an objective measurement and the gold standard in measuring strabismus, i.e. ocular misalignment, or a deviation of the eye. [1] It is used by ophthalmologists and orthoptists in order to measure the vertical and horizontal deviation and includes both manifest and latent components. [1]
After simplifying the final equation is found: F F c = 1 − x F ⇒ F c = F 1 − x F = 1 1 F − x ⇒ F = 1 1 F c + x {\displaystyle {\begin{aligned}&&{\frac {F}{F_{\text{c}}}}&=1-xF\\&\Rightarrow &F_{\text{c}}&={\frac {F}{1-xF}}={\frac {1}{{\frac {1}{F}}-x}}\\&\Rightarrow &F&={\frac {1}{{\frac {1}{F_{\text{c}}}}+x}}\end{aligned}}}
Esophoria is an eye condition involving inward deviation of the eye, usually due to extra-ocular muscle imbalance. It is a type of heterophoria. Cause. Causes include: Refractive errors; Divergence insufficiency; Convergence excess; this can be due to nerve, muscle, congenital or mechanical anomalies.
In astronomy, the bolometric correction is the correction made to the absolute magnitude of an object in order to convert its visible magnitude to its bolometric magnitude. It is large for stars which radiate most of their energy outside of the visible range.
Hygrometer. Dry / Wet-bulb temperature. v. t. e. Psychrometrics (or psychrometry, from Greek ψυχρόν (psuchron) 'cold', and μέτρον (metron) 'means of measurement'; [1] [2] also called hygrometry) is the field of engineering concerned with the physical and thermodynamic properties of gas - vapor mixtures .
Aberration (astronomy) A diagram showing how the apparent position of a star viewed from the Earth can change depending on the Earth's velocity. The effect is typically much smaller than illustrated. In astronomy, aberration (also referred to as astronomical aberration, stellar aberration, or velocity aberration) is a phenomenon where celestial ...
The free air correction is calculated from Newton's Law, as a rate of change of gravity with distance: g = G M R 2 d g d R = − 2 G M R 3 = − 2 g R {\displaystyle {\begin{aligned}g&={\frac {GM}{R^{2}}}\\{\frac {dg}{dR}}&=-{\frac {2GM}{R^{3}}}=-{\frac {2g}{R}}\end{aligned}}}
One model for this relationship is the Colebrook equation (which is an implicit equation in ): 1 f D = − 2.0 log 10 ( ϵ / D 3.7 + 2.51 R e f D ) , for turbulent flow . {\displaystyle {1 \over {\sqrt {f_{D}}}}=-2.0\log _{10}\left({\frac {\epsilon /D}{3.7}}+{\frac {2.51}{\mathrm {Re} {\sqrt {f_{D}}}}}\right),{\text{for turbulent flow}}.}
Cyclotropia is a form of strabismus in which, compared to the correct positioning of the eyes, there is a torsion of one eye (or both) about the eye's visual axis. Consequently, the visual fields of the two eyes appear tilted relative to each other. The corresponding latent condition – a condition in which torsion occurs only in the absence ...