Visual satisfaction with progressive addition lenses prescribed with novel foveal fixation axis measurements

Abstract

Progressive addition lens (PAL) prescription is usually conducted using the pupillary centre as a reference, which in general does not coincide with the visual axis (kappa distance), and this difference could induce undesired prismatic effects in far and near vision distances and adaptation problems. This study aimed to assess the impact on subjects' visual satisfaction with PALs prescribed based on foveal fixation axis (FFA) measurements. Two different PALs (LifeStyle 3i, Hoya Lens Iberia) were randomly prescribed [one with a customized inset (the difference between the FFA measurements (Ergofocus®, Lentitech, Spain) at far and near distances and the second with a standard inset (2.5 mm)] to be used by 71 healthy presbyopic volunteers in a prospective double-masked crossover clinical study involving one month of use of each PAL. Patients were self-classified into four groups according to their previous experience with PALs: neophyte, PAL users, PAL drop-out, and uncomfortable PAL users. Visual function and overall satisfaction with each PAL were collected and compared. Ninety-seven percent (95% CI 93-100%) of participants successfully adapted to PALs prescribed with FFA without significant differences (P = 0.26) among the study groups (100% neophyte and uncomfortable PAL users (95% CI 100% in both groups), 89% (95% CI 67-100%) PAL users and 94% (95% CI 82-100%) PAL drop-out group). There were no statistically significant differences in visual function (P > 0.05) between customized and standard inset PALs. Customized and standard inset lenses showed similar satisfaction (P > 0.42) that increased significantly (P < 0.01 without any carry-over effect) after 30 days of wear. PALs prescribed with FFA measurements showed high visual satisfaction, suggesting that these measurements are suitable for prescribing PAL adaptation processes. Additional research is necessary to assess differences in PAL users' performance with different prescription methods and lens designs.

Figure 1

Front (upper) and back (inner) image of the Ergofocus® device designed for FFA distance measurement. (A) Distance sensor. (B) On/Off button. (C) Vertical slits displacement control. (D) Horizontal slits displacement control. (E) Rubber band. (F) Horizontal slit. (G) Vertical slit.

Figure 2

Summary of lens preference by group. Customized inset lens was preferred by 42% (95% CI from 23 to 61%) of neophyte users, 60% (95% CI from 30 to 90%) of PALs users, 59% (95% CI from 35 to 82%) of PALs drop-out users, and 47% (95% CI from 23 to 71%) of uncomfortable PALs users. PAL: progressive addition lens; CI: confidence interval.

Figure 3

Details of the first prescribed lens preference. The first prescribed lens was chosen by 37% (95% CI from 18 to 55%) of neophyte users, 60% (95% CI from 30 to 90%) of PALs users, 41% (95% CI from 18 to 65%) of PALs drop-out subjects and 35% (95% CI from 12 to 59%) of uncomfortable PALs users at the end of the trial. PAL: progressive addition lens.

Figure 4

Comparison of the general satisfaction scale between the standard and customized inset lens and between the 10 and 30 days questionnaires. D10: day 10; D30: day 30.

Figure 5

Summary of visual acuity (distance and near visual acuity and lateral visual acuity) and stereopsis measurements between standard and customized inset PALs. The Wilcoxon P value is presented. LE: left eye; RE: right eye; BE: both eyes; N: nasal; T: temporal.

Figure 6

Summary of contrast sensitivity measurements between standard and customized inset PALs. The Wilcoxon P value is presented. c/deg = cycles/degree.