This was a prospective, cross-over, randomized, single-masked (participant), short-term clinical trial conducted at the Clinical Research Trials Centre (CRTC) of the Brien Holden Vision Institute in Sydney, Australia. The trial was approved by a local Human Research Ethics Committee, was conducted in accordance with the principles of the Declaration of Helsinki and registered on the Australian New Zealand Clinical Trials Registry (ACTRN#12613001380785).

Signed informed consent was obtained from participants prior to commencing any study procedures. Participants were required to be healthy with less than 1.00D of astigmatism and correctable to a minimum 6/12 distance high-contrast visual acuity (HCVA) while wearing spherical hydrogel CLs (power range −6.00 to +3.00D). In addition, participants were required to be presbyopic, requiring a minimum +0.75D addition over distance subjective refraction to read 0.1logMAR print on a high contrast black text on white background MNREAD Acuity Chart Card (Precision Vision, IL, USA) at 40cm under photopic conditions (300–350lx).

All baseline procedures were performed under photopic conditions and comprised distance subjective refraction, near addition power measurement, eye dominance identification and acclimatization to the ghosting rating scale used during the trial.

Subjective distance refraction was performed using standard optometric techniques. For the purpose of this trial, participants requiring a negative spherical-equivalent subjective distance refraction were classified as myopes while all other participants were classified as hyperopes. The near add was the minimum plus power required over subjective distance refraction to comfortably read the 0.1logMAR paragraph on a high contrast black text on white background MNREAD acuity card at 40cm. The measured add power was used to stratify participants as low, medium and high presbyopes as shown in Table 1

Sensory dominance was the preferred determinant for eye dominance in this study as the eye with least blur tolerance is identified.23 Sensory dominance was assessed on all participants using the alternate blur method24 (single +1.50D trial lens alternated in front of the participant's eyes with the eye reporting greatest subjective blur deemed the dominant eye), and if the dominant eye was identified, no more eye dominance testing was performed. If sensory eye dominance could not be identified, sighting eye dominance was determined using the sighting method24 (“hole-in-the-hand technique”).

The ghosting scale used in this trial has been previously described.22 Briefly, the scale consisted of 10 progressively ghosted letter ‘R's15 (1=no ghosting, 10=severe ghosting) with a letter size of 6/19. Participants were acclimatized to the scale by viewing it at 6m while wearing their subjective distance refraction in a trial frame.

Test CLs in this trial were EDOF and control CLs were AIR OPTIX® Aqua Multifocal (AOMF: lotrafilcon B, Alcon, TX, USA). The parameters, power range used in this trial and physical properties of both CLs are given in Table 2.

The power profiles of plano distance power for EDOF (low and high power) and AOMF (low and high add) are shown in Fig. 1. These power profiles were measured using the NIMO TR1504 (Lambda-X, Belgium) The profiles show EDOF has a non-monotonic power profile with smooth transition between multiple zones and AOMF has a monotonic power profile with smooth transition from center of the lens to edge of the optic zone.

Figure 1.

The power profiles of the AOMF (low and high add) and EDOF (low and high power) with distance power plano for all lenses. Power profiles were measured using the NIMO TR1504 (Lambda-X, Belgium).

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The initial CL assessed was randomly allocated and participants were restricted to one CL assessment per day. The distance power used for both EDOF and AOMF was based on the spherical equivalent distance refraction. EDOF was only available in 0.50D steps, and so the closest least minus power was used when the spherical equivalent power was unavailable. AOMF was available in 0.25 steps, and so the spherical equivalent power was used for all participants.

The near power chosen for both CLs was based on the participant's near addition measured at baseline. The method used for determining the required near power for EDOF has been previously described22 while manufacturer's recommendations were followed for AOMF lenses.25 The near power chosen for participants are given in Table 1

CLs were inserted by one of several unmasked investigators and participants were masked to CL identity. During a 10min settling time, participants were encouraged to observe distant objects, read printed material or view their phones.

A spherical over-refraction at 6m was performed under photopic conditions. For both test and control CLs, a trial frame and lenses were used to monocularly calculate the maximum plus to best distance HCVA. An additional +0.75D was added binocularly to this result then reduced binocularly in 0.25 steps until the participant could just read the 6/6 line binocularly. Extra plus was given if subjective improvement was demonstrated at near provided binocular distance HCVA was no worse than 6/7.5 and the participant preferred subjective improvement at near compared to slight distance blur. The difference in HCVA between eyes was kept to within one line.

Due to the inequality in power availability between lens types, the over-refraction in a trial frame was worn by participants for all subsequent objective and subjective measurements to optically equalize lens types. A trial frame was not worn if the over-refraction was plano for both eyes.

Objective measurements were performed binocularly at distance (6m), intermediate (70cm) and near (50cm and 40cm) under photopic conditions. Results were entered directly into a database by the investigator.

Distance measurements at 6m comprised HCVA, low contrast visual acuity (LCVA) and contrast sensitivity (CS). A Test Chart 2000 Pro (Thompson Software Solutions, Hertfordshire, UK) was used for all distance measurements, with contrast set to 100% and 10% for HCVA and LCVA, respectively and CS measured with a Pelli–Robson like chart at 18cycles/degree.

A reading-based assessment was used to measure HCVA at intermediate and near. A high contrast black on white MNREAD Card was held at 70cm, 50cm and 40cm and participants were asked the smallest paragraph they could comfortably read rather than the smallest paragraph they could read. These HCVA results yielded are therefore measurements of “comfortable visual acuity” rather than conventional resolution acuity.22 Measurements taken at 50cm and 70cm were adjusted to equivalent logMAR values prior to analysis.

Near stereopsis was measured at 40cm with the Stereo Fly Test Circles (Stereo Optical, IL, USA).

Subjective measurements were assessed binocularly for distance (6m), intermediate (around 70cm) and near (40–50cm) under photopic conditions and results were entered directly into a database by the participant. The investigator only intervened to indicate targets for ratings or clarify rating descriptors.

Subjective ratings were assessed on a 1–10 numeric rating scale (NRS) in 1-point steps as previously described.22 Briefly, the NRS assessed clarity-of-vision (1=blurred, 10=clear) and ghosting (1=none, 10=severe) at distance, intermediate and near.

For clarity-of-vision and ghosting ratings at distance, participants viewed the 6/6 line and 6/19, respectively, of a Test Chart 2000 Pro set to 100% contrast. For clarity-of-vision ratings at intermediate and near, participants viewed the 0.6logMAR paragraph and 0.3logMAR paragraph, respectively, of a high contrast black on white MNREAD Card. For ghosting ratings at intermediate and near, participants viewed the 1.0logMAR paragraph and 0.9logMAR paragraph, respectively, of a high contrast black on white MNREAD Card.

Overall vision satisfaction (1=not satisfied and 10=satisfied) was based on the overall vision experience for all distances. Ocular comfort (1=uncomfortable and 10=comfortable) was measured after all vision assessments were complete.

Participants were asked if they would purchase the CL they were wearing based on their vision experience only (lens purchase). Answers were given as a forced choice yes/no response.

Once all objective and subjective measurements were complete, lenses were observed on eye with slit-lamp biomicroscopy and assessed for centration (mm, horizontal and vertical), primary lens movement (mm), primary lens lag (mm) and tightness (%).

A minimum of 20 participants per stratum was required to demonstrate a statistically significant paired difference between lens types in subjective ratings±standard deviation (SD) of 1±1.5 units with 80% power at the 5% level of significance. This sample also had 80% power to detect a paired difference in visual acuity of 0.1±0.15logMAR between lens types. The resultant sample sizes of 19 in the medium and 10 in the high add strata were inadequate for statistical analysis, and were therefore combined into one stratum (medium-high).

Data were summarized as means±SD for variables measured on an interval scale and as percentages for categorical variables. The ghosting rating scale has been reversed in the analyses (referred to as ‘lack-of-ghosting’ in results) to maintain consistency with other scales. Prior to statistical analysis, stereopsis measurements were log transformed because of the positively-skewed distribution and visual acuity measurements were converted to logMAR.

Repeated measures analysis of variance (ANOVA) was used to determine the overall effect of lens type and its interaction with strata and testing distances for HCVA, clarity-of-vision, and lack-of-ghosting. The model included strata as between-participant factor while lens type and various testing distances were factored as within-participant factor. If the interactions of lens type with strata and/or various distances was significant at the 10% level, paired t-tests were used to compare between lens types at each sub level of the interacting factor.

McNemar's chi-square test for paired categorical data was used to analyze lens purchase and the proportion of participants who rated clarity-of-vision≥8 units for all three testing distances and overall vision satisfaction≥8 units with each lens type.

Chi square test was used to analyze the proportion of participants requiring a trial frame and linear mixed model was used to analyze over-refraction power and lens fitting.

The analysis was performed using SPSS 21 (IBM, USA), and the level of significance was set at 5%.

The total dataset comprised 52 participants: 48% were female, mean age±SD was 53±6 years, age range was 45–70 years and 71% were experienced contact lens wearers. Demographic details for each strata are given in Table 3. There was a significant difference between strata for age (p<0.001) but not for gender, ethnicity, lens wear experience, keratometry or spherical-equivalent refraction (p≥0.204).

Significantly more participants wore a trial frame when EDOF lenses were assessed (71% vs. 42%, p=0.003). There was a significant difference in over-refraction between EDOF and AOMF lenses (−0.09±0.29D vs. +0.02±0.22D, p<0.001).

Repeated measures ANOVA for HCVA showed non-significant interaction between lens type and strata (p=0.676) while interaction between lens type and testing distances was significant at the 10% level (p=0.053). Due to this interaction, paired t-tests at each testing distance using the entire sample (i.e. presbyopes combined) only were performed.

Objective results for presbyopes combined, low presbyopes and medium-high presbyopes are given in Table 4. HCVA and stereopsis at 40cm were significantly better with EDOF (p=0.024 and p<0.001 respectively). There were no significant differences between CL for HCVA at 6m, 70cm and 50cm, LCVA at 6m or CS at 6m (p≥0.169).

Repeated measure ANOVA for clarity-of-vision ratings showed non-significant interaction between lens type and strata (p=0.119) and significant interaction between lens types and testing distances (p=0.004). Due to this interaction, paired t-tests at each testing distance using the entire sample only were performed.

Clarity-of-vision at intermediate and near were rated significantly higher with EDOF (Fig. 2, p=0.006, p=0.005 respectively). There were no significant difference between lens types for clarity-of-vision at distance (Fig. 2, p=0.471).

Figure 2.

Clarity-of-vision (distance, intermediate, and near), overall vision satisfaction and comfort overall ratings while wearing EDOF and AOMF lenses for presbyopes combined. Error bars=1 SD. *p=0.471, †p=0.006, ‡p=0.005, §p<0.001, ¥p=0.002

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Repeated measures ANOVA for lack-of-ghosting ratings showed EDOF was rated significantly better (i.e. less ghosting, p=0.012), but there was no significant interaction between lens type and strata (p=0.276) or testing distance (p=0.126). Results are given in Fig. 3.

Figure 3.

Lack-of-ghosting ratings while wearing EDOF and AOMF lenses for presbyopes combined at distance, intermediate and near. There was a significant difference between lens types for lack-of-ghosting (p=0.012) but no significant interaction between lens type and testing distance (p=0.126). Error bars=1 SD.

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The proportion of participants who rated clarity of vision≥8 units for all three testing distances and overall vision satisfaction≥8 units was significantly higher when EDOF was worn (Fig. 4, p=0.022 and p=0.002 respectively).

Figure 4.

Proportion of presbyopes combined who rated clarity-of-vision≥8 units for all three testing distance (distance, intermediate and near) and overall vision satisfaction≥8 units while wearing EDOF and AOMF lenses. *p=0.022, †p=0.002.

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Overall vision satisfaction and ocular comfort were rated significantly higher with EDOF (Fig. 2, p<0.001 and p=0.002 respectively).

Subjective ratings (descriptive data only) for low presbyopes and medium-high presbyopes are given in Table 5.

Lens purchase results for presbyopes combined are given in Fig. 5. Significantly more participants indicated they would only purchase EDOF compared to only purchase AOMF (p=0.003). A higher proportion of participants indicated they would purchase EDOF compared to AOMF (60% vs. 33%), 27% would purchase both lens types and 35% would purchase neither lens type.

Figure 5.

Lens purchase results while wearing EDOF and AOMF lenses for presbyopes combined. The p-value refers to participants willing to purchases EDOF only (33%) vs. AOMF only (6%).

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Lens fitting results are given in Table 6. There were no significant difference between lens types for centration, primary gaze movement, primary gaze lag or tightness (p≥0.210).