The visual experience is critical for many aspects of human life. It is essential to visual development (the process of emmetropization, which leads to myopia when the visual input is suboptimal)¹; to being able to perform tasks and navigate safely, particularly in the elderly²; and to quality of life.³ Spectacle correction can overcome visual impairment due to refractive error. However, the experience of the spectacle frame’s pressure on the skin, the limitation of the field of view, the image magnification (especially for higher refractive errors, reducing the visual acuity of myopes), the steaming up of lenses, the reflections from the lens surfaces, and the increased accommodative and convergence demands for myopes⁴—to name just a few—can adversely impact the visual experience.

THE VISUAL EXPERIENCE WITH CONTACT LENS WEAR

Contact lenses, in contrast, move with the eye, so the optical correction can be better customized for an individual in all directions of gaze. GP corneal or scleral lenses utilize the similar refractive index of the tear film to the cornea to correct irregularities of the corneal surface, allowing the best correction of refractive error in those who have distorted corneas. The field of view is unimpaired, and the spectacle lens-related problems of reflections from lens surfaces and the lenses steaming up when entering a different temperature environment are not an issue with contact lenses. Contact lenses do not cause the detrimental optical effects that can result from the placement of spectacle lens optics away from the corneal surface. Furthermore, contact lens correction of presbyopia does not require additional head turning to match the visual axis with the optics at the desired focal length; rather, the lens optics can extend the range of clear focus of light entering the eye.⁵

The traditional disadvantages of contact lens wear compared to spectacle vision correction included the contact lens’ effect on ocular physiology and comfort as well as on convenience. However, modern contact lenses are very comfortable due to enhancements in materials, embedded lubricants, and coatings.⁶ In a study by Lazon de la Jara and colleagues,⁷ some contact lens brands were actually more comfortable to wear compared to spectacles at the end of the day! With the development of silicone hydrogel contact lens materials and the subsequent improvements in chemistry, complications due to the lack of oxygen permeability and even due to mechanical effects of contact lens wear have largely been eradicated. Contact lens wear is not without risk, but the likelihood of developing a serious infection with daily disposable contact lens wear is only 2-to-5 per 10,000⁸; to put that into perspective, this is similar to the risk of dying in a car accident in the United States.⁹ Finally, daily disposable contact lenses present a more convenient form of refractive correction because they eliminate the need for cleaning and disinfection compliance.

ASSESSING THE VISUAL EXPERIENCE

The visual experience is normally assessed in a clinical setting using high-contrast letter visual acuity with a distant target (Figure 1A). While this can be used to differentiate visual loss due to disease or visual impairment related to refractive error, it is not a sensitive measure of visual quality.

Contrast sensitivity is critical to visual quality; its assessment results in a contrast sensitivity function (Figure 1B). It is well established that metrics such as reading speed (Figure 2A) better relate with the performance of everyday visual tasks when compared to visual acuity. Traditional methods of contrast sensitivity and reading speed measurement are cumbersome and not often performed in clinical practice; however, with the development of visual apps for tablet digital devices, such testing can now be performed quickly and efficiently to better understand the visual quality achieved with a visual correction.¹⁰ However, subjective ratings of patients’ visual experience is most critical. Visual experience is rarely rated in clinical studies; visual quality is more commonly examined, although Pointer¹¹ has shown that rating visual experience can be easily achieved on paper or on a slider visual analog scale. Quality is the standard of something as measured against other things of a similar kind or the degree of excellence. Experience could be argued to be broader, based on impression that includes quality of vision determined by aberrations and cortical processing as well as factors such as the speed of response (such as eye focusing), dysphotopsia, and application and removal of the correction.

The visual experience is not consistent with time. An intact and regular tear film is essential for high-quality retinal images; therefore, a deteriorated tear film can degrade the visual experience. Functional visual acuity can be assessed by measuring visual acuity (usually with a Landolt “C” that decreases in size if the gap direction is correctly identified or increases in size if incorrectly identified) rapidly and multiple times (12 to 30) per minute (Figure 2B) or by measuring reading speed.¹² Research shows that in natural situations, individual blinks are not always associated with an immediate increase in visual acuity in patients who have dry eye.¹³ A shorter period of tear stability compared to the inter-blink interval often occurs in visual display terminal users; interestingly, modern contact lenses can be a protective factor for an unstable tear film, demonstrating how far material developments have enhanced contact lens wear and, hence, the visual experience.¹³ However, there does not yet appear to be research evidence to link functional visual acuity to lens surface properties such as wettability and lubricity. An objective assessment of visual experience can be determined by measuring optical aberrations dynamically, or these changes can be implied by assessing tear film stability.¹⁴ However, again, there is little research utilizing this technology to date.

When evaluating a new visual correction with patients, encourage them to think about the visual experience related to the task of interest. New presbyopes are generally struggling with their near vision; so, rather than the traditional approach of demonstrating their distance vision through the lenses and then determining what they can see at near, they should view a near task (ideally something with which they have been struggling) first to see what they have gained to meet their need. This should then be followed by viewing a realistic distant scene that demonstrates how good their distance vision still is. It might be reasonable to expect the visual experience with stable toric contact lenses rather than spectacles to be better in a dynamic environment, such as during navigation, compared to with static acuity tasks, although this does not appear to have been investigated in the academic literature.

OPTIMIZING THE VISUAL EXPERIENCE

Toric Lenses So how can the visual experience be optimized? Sulley and colleagues have shown that poor vision is one of driving forces behind contact lens dropout¹⁵ and that fully correcting refractive error, especially the astigmatic component, can lead to successful contact lens wear by those who had previously given up.¹⁶ Chamberlain and colleagues¹⁷ developed a novel chart for near vision assessment of soft toric contact lenses (the VANT chart) consisting of a central, color-coded logMAR panel and eight peripheral letter targets set on a white background. The optimized testing involved rapid, diagonal versional eye movements, which showed differences between toric designs for baseline and post-version acuity on the new VANT chart alongside low-contrast (but not high-acuity) distance visual acuity measurement. This further demonstrates that conventional approaches to measuring visual acuity do not fully replicate the “real-world” visual experience. Visual acuity is reduced immediately after versional eye movements, so patients fit with toric lenses need counselling to adapt to this, and toric contact lenses should be fit to maximize their stability and rapid relocation on the ocular surface after any displacement. While the optical aberrations of the eye can be altered by fitting contact lenses that have aspheric optics, the benefits appear to be very minor.¹⁸ Aspheric optics in soft contact lenses may also be less effective compared to toric lenses for optimizing the visual experience of low astigmats.¹⁹

Contact Lenses for Presbyopia Optimizing success with contact lenses for presbyopia can be more challenging. In addition to the visual acuity at distance, the intermediate and near distances must be considered. Unlike natural youthful accommodation, in which crystalline lens changes driven by the ciliary muscle can maintain the level of acuity from distance to near for a fully corrected eye, multifocal lenses aim to optimize the focal length of the light entering the eyes at specific distances. Hence, push-up-style tests to examine the range of clear focus are redundant, and a defocus curve is typically determined in a research setting.⁵ This involves patients viewing a distance acuity chart wearing their multifocal refractive correction while plus lenses are introduced (usually in +0.50D steps) to simulate closer task demands. Hence, these curves allow clinicians to see what an average patient should achieve from an acuity standpoint at different near and intermediate distances and how a particular lens “performs” over this range. However, this is only part of the visual experience, as by splitting the light entering the pupil, multifocal optics can reduce contrast sensitivity and cause light scatter, usually reported as glare when driving at night. In addition, monovision causes monocular suppression, resulting in a marked reduction in stereopsis.⁵

In relation to choosing a multifocal correction for early presbyopes, Woods and colleagues²⁰ concluded that making a prediction of “success or not” based on consulting room acuity tests alone is probably unwise. More recently, a multi-practice survey of successful and unsuccessful presbyopic contact lens wearers (not which multifocal contact lens was best for individual patients) again showed the limitation of clinical, demographical, and lifestyle metrics while noting that the principal reason for contact lens discontinuation was poor vision (reported by 80% of participants); the absence of astigmatism as well as subjective reporting of higher satisfaction, better perceived vision at distance, and a lower loss of visual contrast were predictive of successful contact lens use for presbyopia.²¹

In our research,²² patients wore a series of more recent contact lens designs for presbyopia (including monovision) for one month each in random sequence; a wide range of clinical and lifestyle characteristics were assessed, and we found that lens preference (which included visual experience) was not dependent on personality, lifestyle (including the amount of time spent working at different distances), natural ocular aberrations, or pupil size—despite the fact that pupil size logically affects the optics through which the light reaching the retina is focused to different focal distances.

This was also demonstrated by Park and colleagues,²³ in which tinting multifocal lenses had a marked effect on pupil size but provided no advantage in terms of the visual function of early presbyopes. Likewise, in our research, there was no between- or within-participant association between their preferred lens choice and the clinical performance when wearing each of the multifocal lens designs or monovision in terms of reading speed, near activity subjective visual satisfaction (NAVQ rating), objective glare measurement, aberrations with the lens in situ, or ocular physiology.²² Hence, despite suggestions that the lifestyle and pupil size of patients and the optics of the multifocal lens design should allow practitioners to select the optimum contact lens for an individual presbyopic patient, the evidence strongly suggests otherwise. Rather, optimizing the refractive correction—including any clinically significant astigmatism—is critical along with regular communication over the first few months to see how a lens is working for a given patient in terms of the visual experience and comfort,¹⁵ such as through a contact lens buddy phone call. It is important to let patients know that there are other lens designs to trial if the current approach is not working for them.

Tinted Lenses Tinted contact lenses can also affect the visual experience. Therapeutic tinted contact lenses have been effectively used to reduce photosensitivity and nystagmus in ocular conditions such as achromatopsia, albinism, and aniridia and, hence, can enhance the visual experience.²⁴ In addition, photostress recovery, glare disability, glare discomfort, and chromatic contrast can be improved in patients wearing photochromic contact lenses compared to a traditional clear lenses worn in the other eye, with participants masked as to which lens was in which eye.²⁵

However, decorative colored lenses can affect ocular aberrations. So, consider that the desire of these wearers to improve the way that other people visually experience them may adversely affect their own visual experience.²⁶

ATTRACTING NEW CONTACT LENS WEARERS

The visual experience of wearing contact lenses can also entice patients to adopt contact lenses as a visual correction modality. Researchers of a multi-practice research project selected 91 patients who had no previous contact lens experience and were choosing new glasses. The researchers randomly allocated the patients to be dispensed in the normal way (n = 39) or to be fit with contact lenses (n = 52) to aid with their spectacle dispensing experience.²⁷ Of the latter test group, 88% (n = 46) agreed to try contact lenses, of which 45 could be successfully fit. They reported a superior subjective spectacle dispensing experience and spent on average £267 ± £143 on their spectacle frames and lenses, 32% more compared to the control group who were dispensed in the traditional way (who spent, on average, £202 ± £128). At three months post-dispensing, one-third (33%) of those who had worn contact lenses as part of their dispensing experience had purchased contact lenses (n = 17) compared with 15% (n = 5) of those who had been traditionally dispensed. Hence, the visual experience of contact lenses—and perhaps overcoming any unwarranted concerns about contact lens wear—prior to spectacle dispensing appears to be well received by those people renewing a spectacle refractive correction and can lead to an increase in refractive correction sales.

CONCLUSION

In conclusion, it is prudent for contact lens practitioners to emphasize the visual experience benefits of contact lenses. No one would dream of having one pair of shoes for all purposes, and likewise, a single form of refractive correction will not provide the best visual experience in all environments. Contact lenses offer an unrestricted field of natural vision, with generally stable optics even in dynamic visual settings. It is worth offering the visual experience of wearing contact lenses to all patients, especially those who have never worn them before or who have dropped out, as part of their spectacle dispensing. The comfort and convenience should also help to increase your immediate sales and ongoing income.

Follow up with newly fit contact lens wearers, especially those fit with toric lenses or with multifocals or monovision for presbyopia, over the first few months, as this is essential to minimize dropout. The visual experience—as well as comfort and handling—should be explored. Offer the possibility of a return appointment for optimization of the visual experience as part of your patient care.

Finally, do not compromise on the visual experience when fitting contact lenses; cost decisions are for patients rather than for practitioners to make. Patients will be more likely to drop out and to pass on a poor opinion of contact lens wear to their friends and relatives if their visual experience is not optimized with a full correction in a modern lens material and with as frequent a replacement schedule as possible. CLS

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