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 ?
In the meanwhile, Pierrat Torterue allowed the thongs, red and gorged with blood, to drip upon the pavement.
Woodhouse had reached her with his request to be allowed to hand her into the diningparlour, was saying
Jennings, perhaps satisfied with the partial justification of her forebodings which had been found in their late alarm, allowed herself to trust in his judgment, and admitted, with unfeigned joy, and soon with unequivocal cheerfulness, the probability of an entire recovery.
"But I did not allow it," murmured the wretched prince.
We know also that he was not received at the Epanchins' so long as they remained at Pavlofsk, and that he was not allowed an interview with Aglaya;--but next day he would set off once more on the same errand, apparently quite oblivious of the fact of yesterday's visit having been a failure,--and, of course, meeting with another refusal.
and his wife, if affairs allowed of it; the general was to stay at home.
You will allow me, as a private individual, to decline pursuing a subject which has lashed me to the utmost verge of desperation in my professional capacity.'
Micawber to my aunt, 'if you will allow me, ma'am, to cull a figure of speech from the vocabulary of our coarser national sports - floors me.
'It is not for one, situated, through his original errors and a fortuitous combination of unpropitious events, as is the foundered Bark (if he may be allowed to assume so maritime a denomination), who now takes up the pen to address you - it is not, I repeat, for one so circumstanced, to adopt the language of compliment, or of congratulation.
'I beg to be allowed to convey, through you, my apologies to your excellent aunt for my late excitement.
It is true the second author of this work was unwilling to believe that a history so curious could have been allowed to fall under the sentence of oblivion, or that the wits of La Mancha could have been so undiscerning as not to preserve in their archives or registries some documents referring to this famous knight; and this being his persuasion, he did not despair of finding the conclusion of this pleasant history, which, heaven favouring him, he did find in a way that shall be related in the Second Part.
The king got the directions, and allowed he'd go and work that camp-meeting for all it was worth, and I might go, too.