Which device uses concentric circles to assess the corneal surface quality?

The device that uses concentric circles to assess the corneal surface quality is the Placido ring. This instrument utilizes a series of rings that project onto the cornea, allowing for the visualization of the corneal contour. The reflection of these rings enables practitioners to evaluate the corneal shape and surface, which is essential in diagnosing conditions like keratoconus or irregular astigmatism. The analysis of the concentric circles helps in identifying the variations in elevation and curvature across the cornea, providing valuable information for fitting contact lenses or planning surgical interventions.

Other devices mentioned play different roles in corneal examination. The ocular gauge is often used for measuring the refractive error of the lens rather than assessing corneal surface quality. Corneal topographers, while they can assess the corneal surface, they do so by utilizing more advanced technology that may involve multiple systems, not just the concentric circle method of the Placido rings. Similarly, keratometers primarily measure the curvature of the central part of the cornea but do not employ concentric circles in their operation like the Placido rings do.