It is well known that 15% to 20% of contact lens wearers will drop out from this modality during their first year of wear.1 What is less well known is that one-third of these patients will stop wearing their lenses during the first months after lens fitting.2 Unmet expectations for vision and comfort are still the most important factors leading to discontinuation of lens wear, but handling and the burden of taking care of the lenses also play a significant role.3 These elements suggest that, as practitioners, we do not listen to patients and that we do not take enough time to train and follow up with new wearers appropriately. Most potential dropouts will not look for other options because they believe the lenses we suggested were the best ones for them and that nothing else can be done. They simply quit the modality without contacting their eyecare professional.
At the other end of this spectrum, mature, experienced contact lens wearers are also dropping out at a high rate, simply because they cannot see close up anymore with their contact lenses, and they feel their only option is eyeglasses.4 Mea culpa again. We are not listening enough and not proactively discussing multifocal options with our current contact lens patients. This represents a true missed opportunity.
We can work on transforming this failure into a unique opportunity, particularly if we bring scleral lenses into the equation and to the normal cornea world.
The Multifocal Scleral Lens Difference
Scleral contact lenses can address the two major reasons why new and current contact lens wearers are dropping out: vision at all distances and comfort.5 They can also contribute to improving the wettability of the ocular surface, which is a major factor leading to lens dropout.6
In terms of vision, scleral lenses meet patients’ needs in many ways. First, they are made from gas permeable (GP) material, unbeaten by soft lenses for its optical quality.7 Second, GP material does not dehydrate, and consequently, the lenses maintain their parameters. Third, scleral lenses are designed with a large optical zone (8 mm to 9 mm, on average). As a reference, the average optical zone of spherical soft lenses is 6 mm, and if a toric component is added to the design, the optical zone becomes smaller. Halos and glare are generated if a patient’s pupil dilates over this smaller diameter. Scleral lenses can help reduce this issue significantly. Fourth, corneal irregularities (warpage, ectasia) increase the level of higher-order aberrations (HOAs), which are also linked to visual symptoms. The tear fluid layer of the scleral lens system easily compensates for any corneal surface irregularity and helps improve vision by reducing HOAs. The tear fluid layer also compensates for corneal astigmatism up to 3.50D with a spherical lens.7 This is a crucial element to consider when caring for patients with presbyopia. Masking astigmatism is not an option,8 particularly in multifocal contact lenses, and few reliable products in the soft lens market allow for this. This potential for addressing astigmatism may be the primary reason to select scleral lenses as a valid option for patients with presbyopia.
Another good reason to choose scleral lenses for prebyopia is that, once properly fitted, they are centered and do not move with blinking. Soft multifocal lenses often decenter temporally and inferiorly, which affects the quality of vision, particularly for higher add powers.9 By combining a larger optical zone, better centration, and less movement upon blinking, scleral lenses are an interesting alternative for improving the vision of patients with presbyopia.
For comfort, a scleral lens does not generate lens-to-lid interactions. This is why scleral lenses feel more comfortable than smaller GP lenses and at least equally as comfortable as new soft lenses upon application. Another major benefit comes from the fact that the cornea and part of the ocular surface remain bathed in fluid during all wearing hours. This helps to fix or alleviate end-of-day dryness symptoms. Until proven otherwise, patients with presbyopia can be considered marginal dry eye suspects, and practitioners may be reluctant to suggest contact lens options to them.10 For patients who have been wearing soft lenses for many years, exposure to chemicals and buffering or preservative agents contributed to an increase in the dryness symptoms because of their toxic impact on conjunctival and corneal epithelii.11 Scleral lenses are filled with nonpreserved saline or artificial tears, hopefully not containing any buffering agents. This is a healthier alternative for the ocular surface.
Because of the nature of the GP material, scleral lenses do not absorb preservatives or buffering agents from care solutions that cannot be released during lens wear, with the exception of BAK GP conditioning solution, which is difficult to rinse from the inner surface before lens application and may contaminate the tear reservoir supporting the scleral lens.
Taking into account all of these factors, multifocal scleral lenses should be considered a valid option for the following patients who have presbyopia:
- Any patient with corneal and refractive astigmatism more than 0.75D
- Current contact lens wearers with symptoms of:
- eye dryness at the end of the day
- visual issues (glare, halos, HOAs, fluctuating vision, etc.)
- lens decentration
- Potential contact lens wearers suspected of having marginal eye dryness or confirmed to have dry eye disease
- Patients needing prismatic correction (scleral lenses from molding can help—any prism, any orientation).
Your Go-to First Trial Lens for Presbyopia
Disposable silicone hydrogel lenses remain the preferred option for patients with emerging presbyopia.12 With several good designs available in the daily disposable modality, it would not make sense to immediately prescribe scleral lenses for every patient with presbyopia. However, as soon as a silicone hydrogel or soft multifocal lens leads to a partial or complete failure, either vision or comfort-wise, then the natural next step is to switch to the scleral lens modality.
The benefits may be high for improving vision and comfort for patients with presbyopia, but unanswered questions remain about the long-term clinical outcome of scleral lens wear on the ocular surface. While scleral lenses are the obvious choice for irregular corneas with the goal of restoring visual acuity or for treating eye disease, prescribing these larger lenses to compensate for current refractive errors, including presbyopia, is an emerging trend.
To remain on the safe side, it is important not to negatively impact the corneal physiology. The consensus now is that scleral lenses may trigger chronic hypoxic stress to the ocular tissue.13 Consequently, they are contraindicated on compromised corneas where the endothelial cell count is fewer than 800 cells/mm2. If edematous signs become visible on these patients, this means that the same lens fitted with the same parameters will generate an equivalent hypoxic stress on normal corneas as well. This is why the accepted approach for this population is to fit lenses with minimal clearance (200 µm) and minimal thickness (250 µm) to avoid any long-term potential negative outcomes.14 While this type of fitting may be done with any scleral lens, it is more easily achieved with smaller diameter ones (14.5 mm to 16 mm).
Lens centration is another important factor to consider, otherwise the visual benefits associated with scleral lenses may be lost. Conjunctiva is toric in nature and not symmetrical. The larger the scleral lens, the more difficult it is to align it perfectly to match this uneven shape. To avoid the design of toric peripheries or complicated landing zones, smaller lenses may be a preferable option. The same rationale applies for handling issues. It is intuitively easier to handle a scleral lens of no more than 15 mm to 15.5 mm in diameter, particularly for patients currently wearing soft lenses.
It was recently reported that scleral lenses may also be associated with increased intraocular pressure.15 At least, it was suggested that compression of the conjunctival tissue may affect the net aqueous humor outflow. Despite contradictory results published about this issue, it may represent a significant risk factor, if proven, for patients at risk for or already diagnosed with glaucoma.
Prescribing scleral lenses for patients with presbyopia should be done only if the benefits are high, and their fitting should be made to lower the risk of affecting ocular health over time.
Switching from Soft to Scleral Lenses
A successful switch from soft to scleral lenses is all about the improvement perceived by patients in terms of their symptoms. This is what we realized when my colleagues and I conducted a clinical study a few years ago, comparing a comfilcon A multifocal lens to a mini-scleral multifocal lens. All of our subjects had been wearing soft multifocal lenses successfully for many years and were asymptomatic. During a crossover 1-month trial, we switched them to mini-scleral lenses. After 2 months, 3 out of 4 patients (75%) reported improved visual acuity, particularly when driving at night and for computer distance. The same positive subjective findings were found for comfort, for which most of the subjects reported a significant improvement. At the end of the study, based on a forced choice questionnaire, 55% of the patients chose to continue wearing the mini-scleral lenses. The loss of 20% (75% vs. 55%) was explained by the fact that the benefits provided by the scleral lenses did not outweigh the burden of handling and caring for the scleral lenses compared to their current equipment. This tells us that patients wearing soft lenses should perceive a net benefit from the scleral lenses to be switched over this modality. On the contrary, if a patient’s symptoms are severe in terms of vision and comfort, this will be an easy task.
Choosing a Design
Scleral lens designs are not so different from those of soft multifocal lenses. Most are near-centered aspheric lenses, while a few are available as distance-centered. Some others offer a zone or ring approach, similar to known successful soft multifocal lenses. To achieve good results with each of these designs, it is essential to become familiar with the manufacturer’s fitting guide and, as needed, to contact the lab consultation team.
Based on my clinical experience, near-centered aspheric lenses offer better clinical performance overall than distance-centered lenses, except for a few candidates for whom distance vision is a high priority.
As is true for soft multifocal lens fitting, it is preferable to focus on a few go-to lenses and become familiar with their specific designs and potential benefits and limits. It is also important to select at least two different designs to address patients’ various vision needs.
What to Expect When Fitting
In general, distance vision is rarely compromised in scleral lenses. The main difference compared to soft lenses is the size of the add zone (AZ) in relation to the entire optical zone. It varies from 1.5 mm to 3 mm on average but may be customized in some designs, if requested. Relative to the optical zone diameter, this AZ is limited, and this is why, distance vision with scleral lenses is less affected compared to soft lenses with the same design. As for customization, patients with large pupils will benefit from a larger AZ to improve their near vision, and those with average pupils will prefer a smaller AZ if they have to establish a priority for distance vision.
As for soft multifocal lens fitting, near vision may be challenging. In any case, it is essential to let neuroadaptation occur. Patients must be evaluated binocularly, and modifications are made monocularly, as a step-by-step approach. Again, fitting guides and consultation are key elements to troubleshooting any vision issues. At delivery, a minimum of 20/25 binocular vision is expected, and 0.50M at near distance, tested by asking patients to look at their smartphones. If these levels of visual acuity are met, we can let patients go for at least a week to 10 days before modifying anything in the fitting, given that the lens fit is acceptable.
Troubleshooting Visual Issues
If there is an issue after the patient has worn the lenses for a week to 10 days, most of the time it is because of uncorrected residual astigmatism. Even the smallest amount of astigmatism may disturb visual acuity, particularly near vision. Patients may also report shadowing around letters and sometimes double vision. A few manufacturers offer the option of adding front toricity to their multifocal lenses, which is the way to go if residual astigmatism is found.
With simultaneous vision lens designs, lighting is an important factor to consider. For that reason, it is important to educate patients about setting proper illumination during near and computer work, as well as proper background lighting in the workplace.
Centration is a key factor to evaluate during fitting and follow-up. Smaller lenses not dealing with toric conjunctiva are easier to keep centered. Larger lenses will benefit from toric peripheral curves to help centration. In some cases, despite an optimal fitting, a significant angle kappa remains between the visual axis of the eye (estimated) and the optical axis of the lens. A decentered optic is the only option to fix this issue. That type of customized design is not widely available, and it may necessitate the use of lenses made from imprints or molding of the eye.
Fitting commercial scleral lenses for Asian populations is a challenge because these lenses were developed mostly for Caucasian eyes. Asian corneas and ocular surfaces are quite different from those of Caucasians, and Asian eyes also have reduced lid apertures and higher upper lid tension. It is obvious that smaller Asian corneas will be better fitted with smaller scleral lenses, but other physiological differences can contribute to decentration of conventional scleral lenses on the temporal side, leading to a touch over the nasal limbal area. In such cases, an Asian-design lens is available, which may represent a better alternative. This design is available as a multifocal as well.
Everything I have discussed thus far can also apply to the patients with irregular corneas. Post-LASIK and post-graft eyes will be better fitted with an oblate design scleral lens. Some manufacturers offer oblate multifocal lenses, as well. Even for patients with regular corneas, an oblate profile may be useful, particularly for patients with high minus powers. Oblate lens design is characterized by a flatter central base curve, and, consequently, it generates more minus power. In some cases, it is possible to lower the prescription of the lens by up to 5.00D while increasing the image size up to 1.75%. This makes a huge difference and immediately improves near and intermediate vision without penalizing distance vision. For a mature patient who is presbyopic and requires a –10.00D correction, an oblate –5.00D lens with a +2.25 add will lead to a better outcome compared to the standard prolate design.
Patients with keratoconus also develop presbyopia, and they may benefit from the use of multifocal lenses. In general, their fitting is similar to that of a patient with a normal cornea, unless the baseline visual acuity with monofocal lenses is already reduced.
Scleral multifocal contact lenses can be a valid option for patients with presbyopia, particularly those with refractive and corneal astigmatism, those experiencing issues with their current soft lenses, or those with irregular corneas needing add power. To improve positive outcomes, practitioners should become familiar with 2 or 3 different designs, one of them being a smaller-diameter scleral lens, which is preferable in most cases.
With these tools in hand, practitioners can address the needs of patients who are presbyopic and at the same time help reduce the dropout rate among older patients.
- Dumbleton K, Caffery B, Dogru M, et al; members of the TFOS International Workshop on Contact Lens Discomfort. The TFOS International Workshop on Contact Lens Discomfort: report of the subcommittee on epidemiology. Invest Ophthalmol Vis Sci. 2013;54(11):TFOS20-36.
- Sulley A, Young G, Hunt C. Factors in the success of new contact lens wearers. Cont Lens Anterior Eye. 2017;40(1):15-24.
- Sulley A, Young G, Hunt C, McCready S, Targett MT, Craven R. Retention rates in new contact lens wearers. Eye Contact Lens. E-pub: June 14, 2017.
- Rumpakis J. New Data on Contact Lens Dropouts: An International Perspective. Review of Optometry; January 2010.
- Nichols JJ. Willcox MDP, Bron AJ, et al. The TFOS International Workshop on Contact Lens Discomfort: Executive Summary. Invest Ophthalmol Vis Sci. 2013;54(11):TFOS7-TFOS13.
- Best N, Drury L, Wolffsohn JS. Predicting success with silicone-hydrogel contact lenses in new wearers. Cont Lens Anterior Eye. 2013;36(5):232-237.
- van der Worp E, Bornman D, Ferreira DL, Faria-Ribeiro M, Garcia-Porta N, González-Meijome JM. Modern scleral contact lenses: A review. Cont Lens Anterior Eye. 2014;37(4):240-250.
- Richdale K, Berntsen DA, Mack CJ, Merchea MM, Barr JT. Visual acuity with spherical and toric soft contact lenses in low- to moderate-astigmatic eyes. Optom Vis Sci. 2007;84(10):969-75.
- Belda-Salmerón L, Drew T, Hall L, Wolffsohn JS. Objective analysis of contact lens fit. Cont Lens Anterior Eye. 2015;38(3):163-167.
- Hickson-Curran SB, Chalmers RL, Keay L, Gleason W. Patient-reported wearing experience from hydrogel daily disposable wearers older than 40 years from the TEMPO Registry. Eye Contact Lens. 2017;43(5):313-317.
- Zhang X, Marchetti C, Lee J, et al. The impact of lens care solutions on corneal epithelial changes during daily silicone hydrogel contact lens wear as measured by in vivo confocal microscopy. Cont Lens Anterior Eye. 2017;40(1):33-41.
- Charman WN. Developments in the correction of presbyopia I: spectacle and contact lenses. Ophthalmic Physiol Opt. 2014;34(1):8-29.
- Compañ V, Aguilella-Arzo M, Edrington TB, Weissman BA. Modeling corneal oxygen with scleral gas permeable lens wear. Optom Vis Sci. 2016;93(11):1339-1348.
- Giasson CJ, Morency J, Melillo M, Michaud L. Oxygen tension beneath scleral lenses of different clearances. Optom Vis Sci. 2017;94(4):466-475.
- Nau CB, Schornack MM, McLaren JW, Sit AJ. Intraocular pressure after 2 hours of small-diameter scleral lens wear. Eye Contact Lens. 2016;42(6):350-353.