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 ?
Making all allowance for the follies that men committed every day in their relations with women, Montbarry's delusion was still the most monstrous delusion on record.
Ah, yes, I understand," said the King; "you have been promoted and given increased pay and allowances.
We must make allowances for a man who suffers under Dexter's infirmities, and lives Dexter's life.
With respect to the distinct species of the same genus, which on my theory must have spread from one parent-source; if we make the same allowances as before for our ignorance, and remember that some forms of life change most slowly, enormous periods of time being thus granted for their migration, I do not think that the difficulties are insuperable; though they often are in this case, and in that of the individuals of the same species, extremely grave.
He had made allowances for her, but the ideal girl would have had no need of allowances.
Sir," he said gravely, "there are great allowances to be made for a man who has not read ROBINSON CRUSOE since he was a child.
Here, too, the slaves of all the other farms received their monthly allowance of food, and their yearly clothing.
She was perfectly disposed to make every allowance for the colonel's advanced state of life which humanity required.
Or if the manager, in any month, delay for more than a fortnight the payment of the allowance which he shall make to the Opera ghost, an allowance of twenty thousand francs a month, say two hundred and forty thousand francs a year.
The chief officers and persons of note carry their own provisions with them, which I did too, though I afterwards found the precaution unnecessary, for I had often two or three cows more than I wanted, which I bestowed on those whose allowance fell short.
The salaries of judicial officers may from time to time be altered, as occasion shall require, yet so as never to lessen the allowance with which any particular judge comes into office, in respect to him.
If I had a proper allowance, like other fellows of my age, this would have been quite unnecessary.