Lens Type General features Advantage Disadvantage Zeiss 4-Mirror Indirect DIMENSIONS 9 mm diameter inner radius 7.85 mm MIRRORS 4 mirrors 12 mm high Angle 64 degrees Rapid evaluation without goniogel, further same-day diagnostic tests not compromised, patient friendly, slit lamp friendly with minimal movement to see 360°,option for compression to perform indentation gonioscopy. Must first master Goldmann gonioprism, more hand-eye co-ordination necessary than for Goldmann gonioprism, easy to apply excessive force causing corneal folds with poor view of angle. Posner Indirect DIMENSION 9 mm diameter inner radius 8.13 MIRRORS Angle 64 degrees Same as Zeiss Same as Zeiss Sussman Indirect DIMENSION Same as Posner, withouth handle MIRRORS Angle 64 degrees Same as Zeiss Same as Zeiss

Table 2: Indirect corneal type lenses.