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This instrument is used for the orthoptic treatment of squint. Two transparent pictures are placed at the ends of two tubes, each provided with a mirror and joined together by a hinge. By means of this construction the tubes may be brought together to suit a convergence of 60° or separated to suit a divergence of 30°. The eye-pieces have a focal length so that the reflected images appear at infinity. Dr. Black has added to the instrument an additional movement in the vertical direction, in order to obtain fusion when the lateral deviation is complicated by a vertical deviation. This vertical adjustment is effected by turning the milled head mounted on the shaft extending down from the hinge.

Model Eye.

C. Chambers Insheep Improved.

In this improved form the inner tube slides in a cloth sleeve to insure smooth and easy adjustment. The posterior end, which carries a normal retina, is concave and of such a curvature that its centre is on the lens when the eye is adjusted to emmetropia.

Cornea and Skin Magnifier.

This achromatic magnifier will be found to give a flat field, the magnification being about 11 diameters; the optical system is a triplet, consisting of one crown and two flints, fitted in a nickel-plated folding mount.

Maenab Retinoscope.

In this instrument the mirror is made astigmatic, so that the illuminated area on the fundus is a band of light rather than an image of the lamp. The illumination, or the shadow, observed in the pupil is therefore more or less band shaped, and much more easily observed. By the rotation of the mirror the band of light on the fundus can be made to lie in the axis of the astigmatism when such is present; the appearance is then produced of a band of light on the face, and a narrow band of light and shadow (“ the shadow ”) at right angles to it in the pupil. The movement is made along the line of the band on the face, which represents the meridian being tested ; the action is that of a plane mirror. If the light on the face

Le texte affiché peut comporter un certain nombre d'erreurs. En effet, le mode texte de ce document a été généré de façon automatique par un programme de reconnaissance optique de caractères (OCR). Le taux de reconnaissance estimé pour cette page est de 99,95 %.

La langue de reconnaissance de l'OCR est l'Anglais.