allowance

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allowance

 [ah-low´ans]
something permitted or allowed.
recommended daily allowance term popularly used as a synonym for recommended dietary allowance.
recommended dietary allowance (RDA) the amount of nutrient and calorie intake per day considered necessary for maintenance of good health, calculated for males and females of various ages and recommended by the Food and Nutrition Board of the National Research Council. See Appendices 4 and 5. Popularly called recommended daily allowance.

al·low·ance

(a'low-antz),
1. Permission.
2. An allotted portion.

allowance

The allocation of a thing on a routine basis.

al·low·ance

(a'low-ans)
1. Permission.
2. An allotted portion.

retinoscope 

An instrument for determining objectively the refractive state of the eye. It consists of a light source, a condensing lens and a mirror. The mirror is either semi-transparent or has a hole through which the retinoscopist can view the patient's eye along the retinoscope's beam of light. A patch of light is formed on the patient's retina and by moving that patch in a given direction and observing the direction in which it appears to move after refraction by the patient's eye, the retinoscopist can determine whether the patient's retina is focused in front of, at, or behind the retinoscope's sight hole. If the light reflected from the patient's fundus (called the retinoscopic reflex or light reflex) and observed in the patient's pupil through the retinoscope moves in the same direction as the movement of the mirror (this is referred to as a with movement), the eye is hyperopic. If the reflex moves in the opposite direction to that of the mirror (against movement), the eye is myopic. Sometimes it is impossible to see a clear movement one way or the other but only a bipartite reflex, showing opposite movements in the two sectors of the pupils (this is called a split reflex or a scissors movement). The refractive error is determined by placing lenses of various powers in front of the patient's eye until no movement is seen, i.e. the whole pupil is either illuminated or dark and the image of the patient's retina is then conjugate with the plane of the retinoscope's sight hole. When this phenomenon occurs the neutral point has been reached. The neutral point is measured for each principal meridian of the eye if it is astigmatic. To arrive at the patient's error of refraction the dioptric power corresponding to the distance between patient and retinoscope (called the working distance) is subtracted from the total lens power used to obtain neutralization. The amount of dioptric power subtracted is called the allowance. (Fig. R13) Syn. skiascope. See retinoscopic band; chromoretinoscopy; fundus reflex; velonoskiascopy.
spot retinoscope A retinoscope that projects a circular beam of light upon the patient's retina.
streak retinoscope A retinoscope that projects into the patient's eye an oblong streak, which can be adjusted in width and rotated in various meridians. It is more efficient than the spot retinoscope in determining astigmatism.
Fig. R13 Optical principle of a retinoscope (O, observers eye; P, patients eye; M, semi-silvered mirror)enlarge picture
Fig. R13 Optical principle of a retinoscope (O, observer's eye; P, patient's eye; M, semi-silvered mirror)
References in classic literature ?
We will not allow her to do such a thing again:" and nodding significantly"there must be some arrangement made, there must indeed.
Her former apprehensions, now with greater reason restored, left her no doubt of the event; and though trying to speak comfort to Elinor, her conviction of her sister's danger would not allow her to offer the comfort of hope.
Allow me to offer my inquiries with reference to the physical welfare of Mrs.
It is supposed that near two parts in five of the whole country is the property of women, owing to their being so often sole heirs, and having such large fortunes in marriage; though it would be better to allow them none, or a little, or a certain regulated proportion.
I do not agree, in fact I am angry, when I hear you called an idiot; you are far too intelligent to deserve such an epithet; but you are so far STRANGE as to be unlike others; that you must allow, yourself.
Of Dorothy's recent traveling companions only Toto and the shaggy man remained, and Ozma had decided to allow the latter to live in Oz for a time, at least.
The Hunter agreed, but said: "If you desire to conquer the Stag, you must permit me to place this piece of iron between your jaws, so that I may guide you with these reins, and allow this saddle to be placed upon your back so that I may keep steady upon you as we follow after the enemy.
But, of course, if I had one, my conscience would not allow me to eat it.
As to the moon, she was considerably larger; but the travelers' glasses, not very powerful, did not allow them as yet to make any useful observations upon her surface, or reconnoiter her topographically or geologically.
And let us equally refuse to believe, or allow to be repeated, the tale of Theseus son of Poseidon, or of Peirithous son of Zeus, going forth as they did to perpetrate a horrid rape; or of any other hero or son of a god daring to do such impious and dreadful things as they falsely ascribe to them in our day: and let us further compel the poets to declare either that these acts were not done by them, or that they were not the sons of gods;-- both in the same breath they shall not be permitted to affirm.
I therefore gave him quite as much as his father was accustomed to allow him; as much, indeed, as he desired to have - but into every glass I surreptitiously introduced a small quantity of tartar-emetic, just enough to produce inevitable nausea and depression without positive sickness.
This liberty I demand, and this I am as ready to allow again to my poor neighbours in their turn.