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Mirrors and optics
Anatomy & Optics
Key Points
- •Law of reflection: angle of incidence = angle of reflection; mirrors produce no chromatic aberration (advantage over lenses)
- •Concave mirror: f = R/2; object between F and mirror produces a virtual, erect, magnified image (basis of retinoscope and direct ophthalmoscope)
- •Direct ophthalmoscope gives a virtual, erect, ~15× magnified image; indirect ophthalmoscope with +20D gives a real, inverted, 3× magnified image with wider field
- •Goldmann 3-mirror lens: 59° mirror (equator-ora), 67° mirror (peripheral retina), 73° mirror (iridocorneal angle/gonioscopy); central lens views posterior pole
- •In gonioscopy, the mirror shows the opposite angle - the 12 o'clock mirror views the 6 o'clock angle
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