Evaluation of two new soft contact lenses for correction of presbyopia: the Focus Progressives multifocal and the Acuvue Bifocal

Abstract

The clinical performance of Focus Progressives multifocal contact lenses and Acuvue Bifocal contact lenses was evaluated in a group of 42 presbyopes, with equal numbers of individuals having low, medium, and high spectacle add requirements. Following visual performance assessment with an optimal sphero-cylinder spectacle refractive correction, each individual wore each of the two types of contact lenses in successive random order. Each type of lens was used in a daily-wear mode for a period of 7 to 12 days, with follow-up and/or refitting visits occurring after 2 to 5 days, and again after 4 to 7 days of attempted wear. Testing for all three forms of refractive correction encompassed Snellen acuities at distance and near, Bailey-Lovie acuities under high and/or low ambient illumination conditions at near, intermediate, and far viewing distances, stereoacuity, a timed visuomotor task (needle threading), apparent glare/flare, and the nearwork range of subjectively clear binocular vision. The contact lenses also were evaluated for handling, comfort, distance and near ghosting, subjective visual quality, acceptability for common tasks (e.g., using a phone directory), and personal preferences.

As might be expected, distance and near acuity, stereoacuity, and visuomotor task performance were somewhat better with sphero-cylinder spectacle correction than with either of the two types of contact lenses. However, several performance differences between the multifocal and bifocal lenses were noted. The Focus Progressives lenses provided significantly better distance acuity under both high and low illumination conditions, and received significantly higher ratings for visual quality (overall and at distance), comfort, and handling. The Focus Progressives lenses were preferred 5:1 over the Acuvue Bifocal lenses. No differences existed between the lenses with respect to near visual acuities, the perceived quality of the near vision, the nearpoint binocular range, stereoacuity, or the acceptability of vision for common nearwork tasks. The results suggest that although both types of lenses afford presbyopes a viable alternative to spectacles, the Focus Progressives lens is superior in many ways to the Acuvue Bifocal lens.

Introduction

Contact lenses offer presbyopes a viable alternative to bifocal or multifocal spectacles as a full or part-time form of refractive correction. Some individuals find that the positional head and gaze requirements associated with such spectacles are uncomfortable or unacceptable for many tasks such as computer work1, 2 and for tasks requiring near vision above the primary gaze horizontal plane. Dynamic tasks also may be difficult, because the volume of three-dimensional space within which objects can be seen clearly without moving the head frequently is much smaller for the spectacle-corrected presbyope than for a younger spectacle wearer having ample accommodation.3, 4 With traditional segmented bifocal spectacles, objects at intermediate distances are not seen with optimum clarity, and there may be visual awareness of the “line” or bifield junction,5 as well as apparent dynamic displacement or “jump” of images produced by the opposing portion of the correction.6 Multifocal or “progressive” spectacles have different potential drawbacks, including distortions of apparent shape and size of objects whose images extend partially beyond the intermediate to near corridor of the lens,7, 8 altered stereoscopic localization secondary to changes in horopter shape and location,7 and alteration in the image/head movement velocity relationship that necessitates gaze-contingent recalibration of the vestibulo-ocular reflex (VOR).9, 10 Contact lenses, on the other hand, move with the eyes and maintain vision through the approximate optical center of the prescription, thereby avoiding the problems inherent in spectacle presbyopic corrections.

Contact lenses intended specifically for presbyopia may incorporate a wide variety of optical designs. Translating, or alternating, designs contain the distance and near correction in spatially distinct portions of the lens, and rely on changes in vertical on-eye positioning to ensure that the gaze is directed through the section appropriate for a given task.11 Such designs, which are more common for rigid than for soft lenses,12 depend on a variety of factors for precise and reliable translation,13, 14, 15 and tend to require greater exactitude in fitting.16 Regardless of form, all other lens designs involve “simultaneous vision”11 wherein only a portion of the light rays received at each foveal retinal locus will have vergence appropriate for the dioptric distance of the current point of regard, while the remaining rays have greater or lesser vergence.12, 17 Simultaneous vision lenses include designs that use a series of grooves forming a diffractive phase grating to create the reading addition,18, 19 concentric designs that have a center-surround arrangement for the two lens powers necessary for the bifocal,20 and aspheric designs that involve continuous change in power from the lens axis to the peripheral portion of the central optical zone, thereby creating a multifocal effect.21 Recent variations on these basic categories include center-surround designs where the distance and near portions are repeated in successive zones,22, 23 multifocal designs where there are multiple transition zones with differing degrees of aspheric change intervening between the distance and near portions of the lens,24 or where the asphericity is confined to a very small portion of the lens.23, 25

Many studies have compared visual performance and/or patient acceptance across two or more different bifocal or multifocal lens designs. Diffractive bifocal lenses have been evaluated against concentric bifocals26, 27 and/or aspheric multifocals.28, 29, 30 Despite similar comparisons among aspheric and concentric31 and translating designs,16, 32 very few lenses have been tested against the visual performance criterion established by optimal spectacle correction.26, 33, 34 The goal of the present study was not additional cross-category analyses, but assessment of the clinical performance of two different lenses that recently entered the global market and thus may be unfamiliar to many eye care professionals. These are CIBA Vision’s Focus Progressives multifocal lens and Johnson and Johnson’s Acuvue Bifocal lens. To understand more fully the vision provided by these lenses, their performance was evaluated relative to sphero-cylinder spectacles at both distance and near.