Slit lamp microscope is an indispensable instrument in ophthalmology. It is mainly used to check the health status of the anterior segment, such as eyelid, conjunctiva, tear film, cornea, anterior chamber, iris, lens, etc; In addition, slit lamp microscope also has very important application value in contact lens adaptation evaluation, observation and analysis of contact lens sediment.

The working principle of slit lamp microscope is that the light from the light source passes through the condenser lens to select the beam shape from the slit, and the slit light is illuminated on the inspected eye through the projection and reflector. The reflected light of the inspected eye can be observed through the binocular stereo microscope. In practice, slit lamp microscopes can be divided into two types: upper light source and lower light source according to the position relationship of the light source.

⑴ Structure of slit lamp microscope

Slit lamp microscope consists of two structures: illumination system (slit lamp) and observation system (microscope).

① Lighting system: the slit lamp microscope lighting system is required to produce a lighting effect with high brightness, uniform lighting, clear cracks and adjustable width. The lighting system consists of xenon lamp, condensing lens group, light source width and height control valve.

1) Light property: the light property of slit lamp microscope illumination system is adjustable, and the filter lever can be called out from left to right

Full open light: the light source passes through completely, and the brightness and heat are the largest.

Desuperheating light: a heat insulation sheet is added in front of the light source to filter out part of the heat of the light.

Polarized light: dimming effect.

No red light filter: it can increase the visual acuity and improve the contrast of blood vessels.

Cobalt blue filter: check the staining of cornea and conjunctiva with sodium fluorescein tear staining, and evaluate the adaptation of RGP lens.

2) Crack light height: the crack light height is adjustable (0 ~ 14mm)

3) Crack light width: the crack light width is adjustable (0 ~ 10mm)

4) Crack light angle: the crack light angle can be rotated by 0 ~ 180 °

② Observation system

The observation system is mainly composed of binocular stereo microscope and magnification converter. Different magnification can be obtained by changing the eyepiece or objective lens. Generally, the low magnification is 6 ~ 10 times, the medium magnification is 20 ~ 25 times, and the high magnification is 30 ~ 40 times.

1) Binocular microscope: the eyepiece can be focused. Before inspection, focus the eyepiece with the help of the focusing rod.

2) Magnification adjustment knob: the magnification adjustment knob can be used to adjust the magnification from 6 to 40 times.