sweetie, I have found this on the internet. You just asked the same question as a guy did. So I think this might be useful to you. It is said that "The slit lamp and keratometer are both diagnostic instruments used by your Doctor of Optometry. Though they both are instruments that use light, and is looked through by the doctor of optometry, there are a lot of differences in optics as they have very different functions.
A silt lamp is an instrument with a pivoting light source that can be focused to a thin strip of light into the eye. It is paired with a biomicroscope (a combination of different powered magnifying lenses) and is used to examine the frontal structures and the internal structures of the eye. It has two oculars which gives a stereoscopic magnified view of these structures and aids in assessing the health of the eye and diagnosing various eye conditions.
A keratometer is an ophthalmic instrument that measures the curvature of the central cornea. It is particularly important for the measurement of astigmatism in the eye. There are manual and automatic keratometers which uses different methods of measuring this curvature. The basic instrument shines a light of known size onto the cornea and a dial is turned until the image being reflected by the cornea is in focus – the dial indicates the corneal curvature." Hope this helped! You don't need to thank me. You can thank the doctor who give this answer. LOL...
