An advanced slit-image camera.

Precision slit-image photographs of the anterior segment of the eye are capable of giving information about the dimensions and densities (light-scattering properties) of the refractive structures of the eye, which is not obtainable by direct inspection, and of providing a record of progress. Slit-image pictures were first used for this purpose by Goldmann (I940). For a slit-image photograph to be suitable for measurement it should be in perfectly sharp focus in all parts, the slit beam should cut exactly the same section of the eye on each occasion, and this section should be as nearly as possible along the optic axis of the eye. Valid comparisons can then be made between the same eye on different occasions and between different eyes. For density measurements a standard density reference needs to be incorporated in each slit-image picture (Fig. i).