Objective evidence of a disease as distinguished from
symptom, which is a subjective complaint of a patient.
See diagnosis;
prognosis.
Argyll Robertson sign See Argyll Robertson pupil.
Bell's sign Bell's phenomenon occurring on the affected side in Bell's palsy.
Bjerrum's sign See Bjerrum's scotoma.
Cogan's lid twitch sign A twitch of the upper eyelid in an eye with ptosis when the patient is asked to look in the primary position following a downward look. The eyelid then returns to its ptosis position. This condition occurs in myasthenia gravis.
Collier's sign Unilateral, or more commonly bilateral, eyelid retraction that exposes an unusual amount of the sclera of the eye above and below the iris; it gives the person a frightened or startled expression. It is due to a midbrain lesion.
See Parinaud's syndrome.
sign convention A set of conventions regulating the direction of distances, lengths, and angles measured in geometrical optics. The most common is the
New Cartesian Sign Convention. It stipulates: (1) All distances are measured from the lens, refracting surface or mirror. Those in the same direction as the incident light, which is drawn travelling from left to right, are positive. Those in the opposite direction are negative. (2) All distances are measured from the axis. Those above are positive. Those below are negative. (3) Angles are measured from the incident ray to the axis, with anticlockwise angles positive and clockwise angles negative. (4) The power of a converging lens is positive and that of a diverging lens is negative (Fig. S7).
See focal length;
Lagrange's law;
law of refraction;
Newton's formula;
fundamental paraxial equation.
Dalrymple's sign Retraction of the eyelids causing an abnormally widened palpebral fissure, in primary gaze. This is a sign of Graves' disease. The patient appears to stare and to be frightened as some white sclera may be seen above the upper limbus.
doll's eye sign See doll's head phenomenon.
von Graefe's sign Immobility or lagging of the upper eyelid when looking downward. This is a sign of Graves' disease.
Gunn's crossing sign Tapering of veins on either side of the arteriovenous crossings seen in hypertensive retinopathy.
Hutchinson's sign A triad of signs present in congenital syphilis. They are interstitial keratitis, notched teeth and deafness.
local sign See oculocentric direction.
Moebius' sign Convergence weakness occurring in Graves' disease.
Mizuo's sign See Mizuo's phenomenon.
Munson's sign A sign observed in keratoconus in which the lower lid is bulging as a cone when the patient looks downward.
pseudo-von Graefe sign See aberrant regeneration.
Rizzuti's sign An arrowhead pattern near the nasal part of the corneoscleral limbus, sometimes seen in advanced keratoconus.
Salus' sign Retinal vein deflection from its normal course at arteriovenous crossings seen in hypertensive retinopathy.
Seidel's sign See Seidel's scotoma.
Shafer's sign The presence of pigment granules of various sizes floating in the anterior vitreous. They usually result from a retinal break/s, which may progress into rhegmatogenous retinal detachment. Then the pigment cells appear as small black dust-like particles ('
tobacco dust') seen on clinical examination.
Vogt's sign Loss of the normal shagreen of the front surface of the crystalline lens indicating anterior capsular cataract.
See crocodile shagreen.
Uhthoff's sign See Uhthoff's symptom.


Fig. S7 Sign convention at a spherical refracting surface S (O, object; A, vertex; C, centre of curvature; I, image; n, n′, refractive indices)