pupil

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pupil:

see eyeeye,
organ of vision and light perception. In humans the eye is of the camera type, with an iris diaphragm and variable focusing, or accommodation. Other types of eye are the simple eye, found in many invertebrates, and the compound eye, found in insects and many other
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.

Pupil

 

the opening in the iris through which light rays enter the eye.

The dimensions of the pupil change according to the amount of light present: the pupil dilates in darkness, under emotional excitement and painful sensations, or with the injection of atropine or adrenalin into the body; it contracts in bright light. Change in the dimensions of the pupil is regulated by fibers of the autonomic nervous system and is accomplished by means of two smooth muscles located in the iris—the sphincter, which contracts the pupil, and the dilator, which expands it. In higher vertebrates, changes in the dimensions of the pupil are produced reflexively by the effect of light on the retina of the eye; in lower vertebrates, these changes are produced by the direct action of light on contrac-tile formations in the pupil. The pupil is usually round or slitlike; in some fish (for example, in a number of sharks, rays, and flounder) and mammals (for example, in sperm whales and dolphins) a projection of the iris, suspended from the superior edge of the pupil, can cover the pupil completely in the presence of intense illumination. In man the pupil is round; its diameter may change from 1.1 mm to 8 mm. Changes in the shape, dimensions, and speed of reaction of the pupil (so-called pupillary reflexes) are of diagnostic significance in eye diseases.

O. G. STROEVA

pupil

[′pyü·pəl]
(anatomy)
The contractile opening in the iris of the vertebrate eye.

pupil

1
1. a student who is taught by a teacher, esp a young student
2. Civil and Scots law a boy under 14 or a girl under 12 who is in the care of a guardian

pupil

2
the dark circular aperture at the centre of the iris of the eye, through which light enters
References in periodicals archive ?
Presence of relative afferent pupillary defect carries a poor prognosis as it denotes injury to optic nerve & retina.
Relative afferent pupillary defect in patients with asymmetric cataracts.
In patients with CRAO, an eye exam show profoundly decreased visual acuity, and the swinging light test (see "Use this mnemonic to ensure a comprehensive eye exam" on page 348) will reveal a relative afferent pupillary defect (RAPD).
Initial visual acuity of NPL or PL+, the presence of relative afferent pupillary defect (RAPD), central corneal opacity, retinal detachment, endophthalmitis, macular scarring and optic atrophy were other factors associated with poor final visual outcome.
Her pupils were isochoric and a relative afferent pupillary defect was observed in her right eye.
The initial assessment should focus on the firmness of the swelling, extraocular movement, and visual acuity (including evaluation for an afferent pupillary defect).
The relative afferent pupillary defect was positive in the right eye.
This is diagnosed by a visual acuity of less than 6/60, the presence of a relative afferent pupillary defect (RAPD), and extensive deep retinal haemorrhages.
(1) Additional useful signs are chemosis of bulbar conjunctiva, reduced visual acuity, afferent pupillary defect and toxic systemic symptoms.
The patient, who had no color vision and had right relative afferent pupillary defect (RAPD), was treated with intravenous pulse steroid therapy (intravenous metil-prednisolone, 1000 mg/ day, for three days).
Examination also revealed an afferent pupillary defect of the right eye and right lateral rectus muscle palsy (figure 1).
Asymmetric glaucoma is also detected in a patient with relative afferent pupillary defect (RAPD) or asymmetric optic nerve cupping without an RAPD.