Contact Lens Spectrum: Prescribing for Presbyopia

A New Measurement Tool to Improve Presbyopic Lens Fitting

1 September 2015

BY CRAIG W. NORMAN, FCLSA

When fitting contact lenses, multiple measurements should be taken to ensure that the proper lens design and parameters are chosen for each patient. While Ks and spectacle Rx continue to be the parameters that manufacturers most commonly build their fitting guides around, there appears to be a resurgence in incorporating additional information such as horizontal/diagonal visible iris diameter (HVID/DVID), pupil size, distance from the lower eyelid margin to the pupil margin, and palpebral aperture size. This is especially critical in fitting lenses for presbyopes.

Additionally, sagittal depth/height has become the new buzzword (again), initially in the scleral lens area, but now in many soft lenses as well. Ever since Graeme Young’s (1992) study, it has been demonstrated that corneal diameter has the most influence on sagittal height, so the ability to accurately measure this ocular parameter is paramount.

Recently, the new Volk Eye Check Contact Lens (VEC CL) device claims to eliminate the potential error that subjective measurements can cause by taking objective measurements (Figure 1) of the eye and eyelid.

Figure 1. HVID, pupil size, and palpebral fissure width

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