Ophthalmoscope, also known as ophthalmoscope, is an instrument for examining the refractive media and retina of the eye, so it is an important examination instrument in ophthalmology. Optometrists can use ophthalmoscopy to analyze the causes of poor corrected vision caused by the fundus and refractive media of the examinee during the pre matching examination of contact lenses, so as to judge whether the examinee can wear contact lenses. Ophthalmoscope is divided into direct ophthalmoscope and indirect ophthalmoscope. Direct ophthalmoscope is particularly common in practical work.

Main structure of ophthalmoscope

The structure of the direct ophthalmoscope includes an illumination system and an observation system. The illumination system includes a light source, a first condensing lens, an adjustable diaphragm, a second condensing lens, a refractive lens, etc; The observation system includes peephole, compensation lens disk, compensation lens reading window and other components.

①Ophthalmoscope lighting system

The ophthalmoscope lighting system is mainly an adjustable diaphragm (Fig. 2-1-41). The adjustable diaphragm of the direct ophthalmoscope has the following settings:

1) Large projection field with aperture of 3.0mm

2) Medium projection field with aperture of 2.6mm

3) Small projection field with aperture of 1.5mm

4) A red free filter with an aperture of 2.6mm is used to observe the blood vessels in the fundus of the eye

5) The measuring aperture, with an aperture of 3.0mm, can project the target coordinate map, and can carry out the location analysis of the macular fovea

② Ophthalmoscope observation system

1) The peephole (Fig. 2-1-43) is a circular hole, usually with a design diameter of 3mm and an observation field of 10 ° ~ 12 °.

2) The compensation lens (Fig. 2-1-44) is a round hole disc, which is usually designed as 25 holes. Each hole has a compensation lens with different luminosity, which is used to compensate for the refractive errors of the tested and observed eyes. Compensation lens usually has: ± 1.00d, ± 2.00d, ± 3.00d, ± 4.00d, ± 5.00d, ± 6.00D, ± 8.00d, ± 10.00d, ± 12.00d, ± 16.00d, ± 20.00d and other photometry.

Direct Ophthalmoscope

Streak Retinoscope