The analysis population consisted of subjects that had data at the 2-week follow-up, and subjects were grouped by the treatment that they received. Subjective responses for each preference item were analyzed jointly using a Bayesian multinomial model for nominal data. Results were reported as posterior mean proportions and preference ratios of preferring the Test lens over the Control lens and 95% credible intervals. Other individual questions were analyzed jointly using a Bayesian random-effects multinomial model for ordinal data. However, due to the low incidence rate within the fair and poor response categories, these were collapsed into one response. Results were reported as posterior mean proportion estimates and odds ratios and 95% credible intervals. All statistical analyses were performed using SAS software version 9.4 (SAS Institute, Cary, NC).15,16

To avoid confusion of outdoor light versus indoor light (both can be bright or dim luminance), the data are separated into those bright light conditions where the photochromic lens is likely to be activated and those normal or low light conditions where activation is less likely (Table 2). In each of the 14 subjective items, the proportion of subjects rating lenses ‘very good’ or ‘excellent’ was significantly higher with the test than the control lens, regardless of the lighting environment.

For overall quality of vision, the proportion of subjects rating lenses ‘very good’ or ‘excellent’ was 85% for the test lens compared with 73% for the control lens. One of the largest differences was for ‘reduction of squinting while using digital devices’: 71% and 51% rated this ‘very good’ or ‘excellent’ for the test and control lenses, respectively. There was also a large difference for ‘ability to see comfortably in bright indoor light’: 83% and 69% rated this ‘very good’ or ‘excellent’ for the test and control lenses, respectively. The item relating to driving at night showed a large difference: 66% and 37% for the test and control lenses, respectively.

The odds ratios of having a more positive experience/rating of the Test lens over the Control lens are summarized in Table 2. Since the lower limits of each 95% credible intervals were above one, all ratios are significant. The largest odds ratio estimate was for ‘ability to see comfortably in bright sunlight’ at 5.24, meaning that subjects were over five times more likely to experience a benefit with the Test lens than with the Control lens.

The preference data are summarized in Fig. 3 (‘strongly prefer’ and ‘prefer’ have been collapsed into ‘prefer’ for simplicity). A majority of subjects preferred the Test lens compared to the Control with respect to: overall lens preference (56.1%), overall preference outdoors (61.1%) and overall preference while driving during the day (58.6%). A large proportion of subjects (>40%) also preferred the test lens with respect to the other four items: overall vision, overall preference indoors, overall preference while driving at night, and overall preference while using computer screens and digital devices.

Fig. 3.

Preference Results of Test (AOwT) versus Control (AO).

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The preference ratios of the proportion of preference for Test over Control lenses (i.e., among those with a preference) are shown in Fig. 4. The Test lens demonstrated superiority relative to the Control with respect to all seven preference items since the lower limit of each 95% credible interval was above 1. The preference ratios ranged from 2.7 to 5.6. ‘Overall preference outdoors’ and ‘overall preference while driving during the day’ showed the strongest trends. Importantly, the preference ratios indicate significant benefits in normal and low light environments such as ‘overall preference indoors’ (4.2:1), ‘overall preference while driving at night’ (3.6:1), and ‘overall preference while using a computer’ (3.4:1). It is an interesting exercise whether to consider ‘overall preference while driving during the day’ an outdoor or indoor activity. Given that automobile windscreens block most of activating UV/HEV light entering the vehicle (although the side windows filter less),18 it is considered an indoor activity to the Test lens where it still provided a significant 5.6:1 preference ratio benefit for daytime driving.

Fig. 4.

Preference Ratios: Proportion of preference of the Test (AOwT) over Control (AO). Error bars indicate 95% Credible Interval.

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It is natural to assume that filtering light in bright environments will provide a visual benefit given the common use of sunglasses. These benefits were evaluated using both psychometric and subjective clinical studies.

Psychometric evaluations of AOwT under bright light conditions have been published elsewhere and are not the focus of this paper.5 To summarize, the activated AOwT lens resulted in a 43% faster photostress recovery time, 39% less squinting, ability to handle 27% brighter light, 32% improved chromatic contrast, 48% reduction in halo diameter, 42% reduction in starburst diameter, and 37% reduction in two-point light threshold over the ACUVUE OASYS Control lens.

Subjective responses relating to outdoor activities during the day, understandably, favored the photochromic lens. Indeed, the Test lens dynamically reduces the amount of visible light entering the eye in all conditions, while the Control lens constantly has high light transmission. AOwT was preferred and rated higher than the control with respect to its performance: outdoors, in bright sunlight, while driving during the day, and its overall visual performance. The measured psychometric items help explain the strong subjective performance.

Visual benefits were also evident in less obvious lighting situations, where the photochromic molecules in the AOwT lens would be in an inactivated or less active state but still providing a useful visual filter. Even in the inactivated state, AOwT filters a significant amount of HEV below 420 nm (Fig. 1). It is well known that light scatters more readily at the violet end of the visible spectrum than at the red end of the spectrum.19 This creates a natural skewness in deleterious visual effects towards the violet end of the spectrum, and filtering light in this region, therefore, has a disproportionate benefit over filtering at the red end of the spectrum. Beyond the reduction of light scattering, the benefits of HEV-filtering have been extended to a decrease in the effects of glare, an increase in retinal contrast, and an increase in visual comfort.3,9-15

As noted earlier, psychometric evaluations of AOwT under low light conditions have been presented elsewhere,7,8 and the results are summarized in Table 3. There are several key benefits: first, there are significant improvements in visual performance metrics, even when the lens is not in the presence of an activating light source. For example, the diameter of halos and starburst are reduced by about 20% on average in dim lighting, which is important to night driving. The favorable result with respect to night driving was unexpected but consistent with a previous study of driving performance with AOwT.20 When compared to a non-photochromic contact lens in controlled driving conditions, the AOwT was non-inferior to the control lens for a wide range of driving tasks in low as well as high illumination. Interestingly, the AOwT lens performance was superior for nighttime sign recognition, and the sign recognition distance was improved by 19%. Consistent with previous reports,21 the authors speculated that mild improvements in low illuminance visual acuity and contrast sensitivity may have contributed to this finding.

Another finding was the apparent improvement in aspects of visual comfort when using digital devices. Glare and discomfort associated with digital devices is an increasingly common problem and has a significant economic and productivity cost.22,23 While using computers and digital devices (typically in the inactivated state), the AOwT lens was rated statistically superior to the ACUVUE OASYS Control lens for the ability to see comfortably, clarity of vision, and reduction of squinting. This was corroborated with a 3:1 preference for the AOwT lens over the ACUVUE OASYS lens for use with digital devices. To emphasize, these bright/normal/low light findings are clinical and statistical advantages over ACUVUE OASYS, which is the leading reusable spherical lens fit for all-day everyday use.24

The main limitation of the current studies is that the questionnaire has not been tested for validity; however, the results of subjective performance are consistent with previous objective visual performance studies. An additional limitation was that investigators were not masked to the lens types, which introduces a risk of bias. Similarly, the studies masked subjects to the control lens but were unable to mask the Test lens since subjects quickly realize whether or not they are wearing a photochromic contact lens. Nonetheless, masking the control lens prevents bias among any subjects who use that lens as their habitual lens. As for future studies, investigators could examine the lens among subjects who are particularly sensitive to bright lights.