With pinhole pupilloplasty, the princi ple is applied to the pupil and iris (Figure 13-5). When pinhole pupilloplasty is performed, the coaxially sighted corneal light reflex axis and the line of sight converge at the fixation point. Therefore, chord mu decreases as the frame of reference moves anteriorly toward the observer and fixation point. In clinical practice, the change in chord mu between the lens–IOL plane (ac tual chord mu) and the corneal plane (apparent chord mu) is typically not significant. Apparent chord mu as seen through the cornea and actual chord mu as mea sured by Scheimpflug are diffe r ent, just as the apparent and actual pupil size vary. The nor­mal apparent chord mu as mea sured on the LenStar and IOL Master is 0.30 mm ± 0.15 mm. The actual chord mu as mea sured on the Pentacam or Galilei (Ziemer) is 0.20 mm ± 0.11 mm. When screening patients to avoid glare and halos with diffractive multifocal IOLs, the upper limit for apparent chord mu is 0.60 mm (mean +2 SD) and for actual chord mu is 0.42 mm (mean +2 SD). When pinhole pupilloplasty is performed, the distance between the pupillary axis and visual axis decreases (ie, the chord length decreases) and this indirectly translates into improved image and visual quality.