In my previous post, On Tonometry, I referred to a black and white disc only found in a cupboard with other obsolete equipment. I must now amend that description. My colleague Debbie, a reader of this blog has informed me that this disc, known as a Placido Disc (no, it's not a CD by one of the three tenors!) is very much still in use. It was required by one of our Ophthalmologists in the clinic the other day, so this fragile, rickety museum piece was carefully removed from its resting place and pressed into service. In appearance, it resembles one of those big cartoon lollipops, with concentric black and white rings (probably liquorice flavoured) It's purpose is to help visualise the curvature of the cornea, by examining the reflection of the white rings. Any astigmatism will show up as a distortion of the rings. The reason the Placido Disc is rarely used now is because we have a tomography machine which will give you a printed map of the cornea, showing you the distortions in a colour-coded diagram.
Still, it's nice to know the old equipment is being used as back-up.