Comparison of physiognomy and frame angle parameters using different devices to prescribe progressive addition lenses.

CLINICAL RELEVANCE

Accurate measurement of several physiognomy parameters (interpupillary, nasopupillary and fitting height distances) and frame angles (pantoscopic and frame wrap angles) is essential for prescribing progressive addition lenses for presbyopic patients.

BACKGROUND

Few reports have described the repeatability of different devices commonly used to conduct essential measurements for prescribing progressive addition lenses.

METHODS

Interpupillary, nasopupillary (at far and near distances) and fitting point heights were measured three consecutive times in 21 healthy volunteers with four devices (traditional frame ruler, PD-5 interpupilometer, OptiCenter, and VisiOffice). Pantoscopic and wrap frame angles were also measured three times with Essilor standard pantoscopic ruler, Opticenter and VisiOffice.

RESULTS

The frame ruler, PD-5 and Opticenter showed better repeatability for interpupillary and nasopupillary distance (co-efficient of variation close to 1%, within-subject standard deviation or Sw < 0.50 mm) measurements at far and near distances than Visioffice (co-efficient of variation > 2%, Sw > 0.50 mm). Fitting point heights measurements showed worse repeatability with all devices (frame ruler: co-efficient of variation close to 5%, Sw = 0.46 mm; Opticenter co-efficient of variation > 5%, Sw > 0.80 mm; Visioffice co-efficient of variation > 10%, Sw > 1.50 mm). Pantoscopic angle measurements showed very low repeatability with the ruler and Opticenter (co-efficient of variation > 25%, Sw > 1.90 mm). The frame wrap angle showed unacceptable repeatability values with the ruler (co-efficient of variation > 10%, Sw = 0.49º) and Visioffice (co-efficient of variation > 60%, Sw > 2.50º), but acceptable repeatability with Opticenter (co-efficient of variation < 1%, Sw = 0.05º).

CONCLUSIONS

Interpupillary and nasopupillary distance measurement showed acceptable repeatability with all the assessed methods; however, these measurements alone are no longer sufficient for free-form progressive addition lens prescription, which requires fitting point heights and pantoscopic and frame wrap angle measurement. Such measures display a lack of repeatability that could induce centration errors and could affect vision and/or adaptation of the user.