BCLA CLEAR – Medical use of contact lenses

In the United States (US), mass produced contact lenses are regulated by the US Food and Drug Administration (FDA). The first (hydrogel) soft CL was approved by the US FDA in 1971 as a new drug [,]. Contact lenses were later reclassified by the US FDA as Class III medical devices (high risk) in 1976 when the Medical Device Amendment was passed. Later regulatory revisions have since reclassified daily wear soft lenses and rigid corneal lenses as Class II medical devices (moderate to high risk), while overnight and myopia management contact lenses, are considered Class III medical devices []. The European Medicines Agency of the European Union, the Australian Therapeutic Goods Administration in Australia, the Drug Controller General of India, and the National Medical Products Administration in China perform a similar function and have similar classification systems for regulating medical devices [].

National regulatory bodies take guidance from the International Organisation for Standardization when creating their policies. This body has specifically set international industry standards that are broadly recognised by regulatory agencies throughout the world for lens and care product labelling []. They have also set efficacy standards for the care systems needed to maintain contact lenses []. Professional organisations likewise provide best practice guidance to clinicians, and they provide feedback to the above regulatory bodies when new policies are being set [].

While any CL might be used medically or as a therapeutic or bandage CL, some contact lenses are labelled for use as a bandage lens or with a therapeutic indication for use.

Contact lenses are used for numerous medical purposes that include, but are not limited to, treating patients with corneal ectasia, ocular surface disease, after ocular surgery and in the setting of high refractive error []. The authors recommend the following set of definitions to be adopted by the community for medical use of contact lenses.

• •
  Therapeutic or Bandage Contact Lenses are lenses that are used for the treatment of ocular discomfort or to support the cornea during healing after surgery or when the cornea is being treated for an underlying disease state or to protect the cornea from the environment or mechanical interaction with the lids.
• •
  Rehabilitative Contact Lenses are lenses that are prescribed for conditions that prevent a patient from achieving adequate visual function with spectacles because of high, irregular, or asymmetric refractive error. Partially or completely occlusive lenses that improve function or cosmesis after trauma, surgery, or stroke also fall into this category.

The first US FDA approved soft contact lens was a conventional hydrogel lens (Soflens) developed by Bausch and Lomb []. Conventional hydrogel contact lenses fail to meet the criteria (87.0 Dk/t) set forth by Holden and Mertz to provide the cornea with enough oxygen to avoid excess corneal swelling during overnight wear [,], a limitation to their use (see CLEAR Complications Report []). Eventually, this challenge of hypoxia was circumvented by the release of the first silicone hydrogel contact lens (PureVision) by Bausch & Lomb with reports of improved performance compared to hydrogel lenses for both cosmetic [] and broad therapeutic use []. While silicone hydrogel contact lenses have a reduced likelihood of corneal hypoxia [, , , ], they have failed to address many of the other issues that are problematic for CL wearers [].

Furthermore, the literature currently lacks well-controlled studies related to these materials being used specifically for medical purposes. One of the first reports on therapeutic soft was published in 1971 []. That study described the use of the Soflens for treating 45 patients with corneal disease (corneal oedema, dry eyes, corneal ulcers, and advanced corneal conditions such as keratoconus). They found hydrogel contact lenses were an effective bandage lens for reducing external ocular discomfort. Early evidence in a study with 278 participants demonstrated that hydrogel contact lenses were effective therapeutic lenses for treating about half of participants with acute or chronic corneal diseases []. In a prospective study, 91 % of the adult participants (n = 70) found benefit from wearing silicone hydrogel contact lenses for therapeutic purposes for conditions such as bullous keratopathy and post-operative corneal epitheliopathy []. Similarly, silicone hydrogel contact lenses can be beneficial post-LASEK [], and a prospective study found that SiHy lenses (n = 29) are safe and effective for children for therapeutic purposes for conditions such as corneal burns or wounds []. Similarly, a multicentre study reported general success of a senofilcon A lens as bandage lens for a range of therapeutic indications []. These data fail to provide clear evidence with regards to selecting a hydrogel or silicone hydrogel contact lens for medical use. Similarly, disposable soft contact lens that are replaced on a daily, bi-weekly, or monthly basis are now readily available, though there is no clear evidence for selecting one wear schedule over another for medical purposes [].

Standard, commercially available soft contact lenses are typically between 13.8 mm and 14.5 mm in diameter. There are two special types of soft lenses that have medical use: large diameter hydrogel soft lenses and custom toric hydrogel or SiHy lenses.

Large diameter hydrogel soft contact lenses are available for off the shelf use in eyes with larger corneal diameters and can be used for medical purposes such as bleb leak or when there is poor retention of typical diameter lenses due to exposure, ocular surface disease or unusual corneal or scleral topography. The sub-committee on Medical Use Contact Lenses acknowledges that there are off the shelf large diameter contact lenses (e.g., Kontur, Hydrolens, Eye-58) and that these are in widespread use in the locales in which they are marketed. However, no primary references related to these contact lenses were identified during the preparation of this report, and because of this, more investigation on this topic is needed. A randomised, crossover study with 25 patients who wore a well-fitted optimum diameter soft contact lenses or a soft lens that was 1.2 mm larger in successive trials were examined to determine if excessively large lens would have a negative impact on the ocular surface []. While the larger lens did not fit as well, there was no difference in ocular comfort between the groups and there was minimal difference in ocular signs. This work will help to inform futures studies as to which parameters of custom soft contact lens fit are critical for success in diseased eyes.

Current literature suggests good long-term tolerance of custom soft contact lenses. A review of 11 charts from patients who began wearing their custom soft contact lenses between 1982 and 1984 found that 7 out of these 11 patients were still wearing their lenses in 1986 []. A study that enrolled 105 patients who had astigmatism and who were empirically fitted with the Igel Rx toric soft lens, found that 74 % of the enrolled subjects were able to wear the contact lens full-time and that 89 % of enrolled subjects were able to achieve vision that was within one line of their best-corrected visual acuity []. A more recent 12-month prospective study with the Kerasoft® iC (custom soft) contact lens in a group of 43 patients who had a variety of irregular corneal conditions found that, at 12 months, 84 % of the subjects were still wearing these lenses with the majority achieving good vision and comfort [].

While rigid corneal lenses make poor choices as therapeutic contact lenses for ocular surface disease because of their mobility, small diameter and associated tear film instability, rigid corneal lenses have been used for decades for visual rehabilitation [,, , ]. Rigid corneal lenses may be particularly useful in patients with high refractive error or aphakia because the lenses needed to correct these conditions would be thick to meet power requirements, limiting oxygen transmission through the lens []. Rigid corneal lenses allow for greater access to atmospheric oxygen than any soft lens which covers the cornea beyond the limbus. Additionally, rigid corneal lenses allow for much greater tear exchange compared to scleral lenses, especially a sealed one, so atmospheric oxygen should be more available to the cornea with this approach [,], just as a SiHy lens is likely to allow for better tear exchange than a sealed scleral lens []. Rigid corneal lenses are useful in the visual rehabilitation of corneal scars because their capacity to neutralise any corneal irregularity outweighs any worsening of straylight []. Nevertheless, the prescribing of rigid corneal lenses has lost some favour for cosmetic purposes and for corneal disease cases in recent years because of the challenges associated with fitting this modality and because many patients find scleral lenses more comfortable []. Some wearers of rigid corneal lenses however, report corneal lenses to be more comfortable than scleral lenses and chose to continue with them, suggesting that this modality remains an option for management of disease [].

A hybrid lens is a contact lens that has a central rigid corneal lens for providing clear vision which is fused to a soft contact lens skirt intended to help with lens stability and comfort. The utility of early hybrid lenses was limited due to low oxygen transmission contributing to corneal neovascularisation and breakage at the lens skirt junction []. Recently, a number of low quality evidence reports, which are fully described in sections 4.1.1 (keratoconus) and 4.2.1 (penetrating keratoplasty), suggest that hybrid lenses are useful in treating patients with irregular corneas (e.g. keratoconus) and with history of surgical interventions (e.g., keratoplasty) [, , , , ].

A piggyback lens system, which is a rigid lens worn on top of a soft lens can be used for medical purposes when surgery, trauma, or disease results in irregular astigmatism or high power requirements, such that a rigid corneal lens is not tolerated []. Because of the combined thickness of two lenses on the eye, the issue of adequate oxygen transmission is critical to consider in selection of each lens []. Many parameters can be manipulated along with adoption of innovations in lenses and materials, to improve comfort, vision, and physiological function [, , ].

Scleral lenses were not only the first contact lens, but they were also the first contact lenses used for therapeutic purposes [,,]. Scleral lenses are large diameter contact lenses, initially impression moulded [,] and then lathed, that completely vault the cornea and land on the sclera/episclera and overlying conjunctiva [,]. Scleral lenses enclose a fluid reservoir that is filled with preservative free sterile saline, creating a tear lens between the ocular surface and the contact lens. This feature neutralises the majority of anterior corneal aberrations, provides lubrication and support of the ocular surface, as well as protection from exposure and/or external mechanical irritation from the lids/lashes. Scleral lenses can play a therapeutic role in ocular surface disease and in the visual rehabilitation of corneal ectasia and irregular astigmatism [] (see CLEAR Sclerals report []).

Scleral lenses have important medical uses as bandage lenses for comfort, as therapeutic lenses for supporting the surface, and in improvement in vision in the setting of disease. There is a large body of evidence on the use of scleral lenses for visual rehabilitation in conditions characterised by irregular astigmatism, to be reviewed in section 4 below. Over 20 years ago, there emerged low quality evidence studies that supported prescribing scleral lenses as therapeutic contact lenses for patients who have severe dry eye. A study of 11 subjects found that 91 % had better visual acuity and symptomatic improvement while wearing modern scleral lenses []. A retrospective chart review including 49 patients who were fitted with scleral lenses for ocular surface diseases, such as Stevens-Johnson syndrome, with dry eye symptoms [], found that fitting these patients with scleral lenses resulted in 82 % having substantial improvements in ocular surface symptoms and 92 % having improvements in visual function and quality of life. Another retrospective chart review evaluated 48 patients who were fitted with scleral lenses after failure with other modalities []. The authors found that, while not all patients could wear scleral lenses (10.4 %) due to mostly handling issues, 81 % of their included subjects had improvements in ocular surface symptoms, similar to the findings of Romero-Rangel et al. Similarly, Jacobs and Rosenthal performed a chart review of 33 patients fitted with scleral lenses for ocular surface disease who were subsequently contacted to complete a survey related to ocular surface symptoms. They found that 97 %, 94 %, and 97 % of their subjects had improvements in pain, photophobia, and quality of life, respectively []. The same group reported significant improvement in visual function as measured by NEI VFQ-25 in a 2006 cohort of 100 patients with ectasia, irregular astigmatism, and ocular surface disease []. Consistent with these reports of broad utility, a survey of 292 practitioners revealed that scleral lens wear improves vision and reduces corneal staining in their patients []. In a study of corneal nerve structure and function in 20 patients fitted with a fluid filled scleral lens, patients with a distorted cornea had significantly reduced basal tear production and increased corneal sensation after long-term wear of the scleral lens, whereas patients with ocular surface disease did not show any changes in tear production or corneal sensation [].

Numerous prospective studies provide strong evidence to support the use of BSCLs immediately following PRK. PRK is a procedure in which the corneal epithelium is removed, followed by ablation of the anterior limiting membrane and the stroma using the excimer laser, to alter corneal shape and thus refractive power. In almost all studies, ocular discomfort is assessed using validated subjective questionnaires. To mitigate pain and promote re-epithelialisation, BSCLs are usually worn for three to five days [,]. Reports of the additive use of BSCLs along with topical anaesthetic agents, topical nonsteroidal anti-inflammatory (NSAID) eye drops, or both, after PRK [,]. Both studies found that patients treated with both topical agents and BSCLs experienced less pain than patients treated with both agents and no lens, supporting the practice of using BSCLs following PRK. More recently, an evaluation of the use of BSCLs soaked in 0.45 % ketorolac [] found that the use of the ketorolac-soaked lens significantly reduced postoperative pain.

Despite the theoretical benefits of increased oxygen transmissibility with silicone hydrogel lenses, medium quality evidence studies are equivocal as far as the superiority of silicone hydrogels to hydrogels. In a prospective study of 100 patients randomised to either a silicone hydrogel or hydrogel lens, the silicone hydrogel lens outperformed its hydrogel competitor []. However, a subsequent study’s retrospective analysis of epithelial healing after PRK in 206 patients did not find a difference in the rate of re-epithelialisation []. While patient-reported pain levels and the frequency of haze were higher with the hydrogel lens, more infiltrates were seen with wear of the silicone hydrogel lens [].

While more recent studies have primarily used silicone hydrogel lenses, there are very few comparative controlled studies that support the use of a specific silicone hydrogel lens after PRK. Available evidence suggests that second and third generation silicone hydrogel lenses may confer some advantages in terms of pain and discomfort; however, re-epithelialisation is unchanged. The data reporting and comparing various SiHy lenses after PRK are summarised in Table 1.

Two medium quality evidence studies have reported on the efficacy of investigational silicone shields following PRK. The first study concluded that the investigational device had a relatively good margin of safety, however no comparator BSCL was used []. A subsequent study included the use of a comparator lens and found an improvement in visual recovery with the silicone shield; however, ocular discomfort was greater compared to the BSCL and no statistical differences were noted in epithelial healing [].

The efficacy of sutureless cryopreserved amniotic membrane placed at the time of the procedure on epithelial healing compared to BSCL after PRK found that the amniotic membrane was not superior to a BSCL in the promotion of epithelial healing after PRK []. Similarly, a cohort study found that the use of sutureless amniotic membrane was not more effective than BSCLs in preventing haze after PRK []. In a similar study, the use of cultured human allogeneic epidermal keratinocyte onlays as a method to promote healing and reduce pain was compared to BSCL wear []. Patients were randomised into one of three treatment groups with the cultured human allogeneic epidermal keratinocyte onlays with BSCL, with amniotic membrane and a BSCL, or a group with BSCL alone. Study findings demonstrated that a shorter duration of lens wear was required for the group treated with the amniotic membrane, but no other differences were noted.

Lens fitting is also an important determinant for managing postoperative pain in PRK. In a prospective study, 140 patients were fitted with a silicone hydrogel lens available in two base curves: 8.4 mm and 8.8 mm []. The relationship between the lens base curve and anterior corneal curvature impacted comfort, with corneas with a postoperative keratometry (K) value of less than 38 dioptres (8.8 mm) having better pain outcomes when wearing the 8.8 mm base curve, whereas steeper corneas with a postop K value greater than 42 dioptres (8.04 mm) did better with the 8.4 mm lens []. Misalignment between the base curve of the contact lens and corneal curvature was a factor driving premature lens loss. This study highlights that lens fit, as opposed to lens material or Dk, warrants consideration and study in the selection of BSCL after PRK.

To further investigate the parameters associated with BSCL wear and pain control, a prospective study examined the timing of BSCL removal in 260 eyes of 130 patients, removing the lens either on day 4 or day 7 post-operatively []. They found no differences in pain between the two groups, although interestingly, the group in which the BSCL was removed on day 4 post-op had an increase in the frequency of complications, including filamentary keratitis, corneal erosion, and haze. This finding suggests that longer postoperative lens wear was associated with fewer complications. Visual recovery at one month was also improved in the seven-day BSCL group, although this change was not evident at three months.

A prospective study examined if the temperature of the irrigating solution and BSCL had an effect on post-PRK pain, with one group receiving chilled (2-5°C) balanced salt solution and a chilled BSCL, while the other group received the solution and BSCL at room temperature (21–23 °C) []. No difference in post-operative pain measures were noted between the two groups.

LASIK is a procedure in which a corneal flap is cut using a blade or femto-laser under which an excimer laser is used to ablate corneal stroma, reshaping the cornea and altering its optical power. There is insufficient evidence to support the routine use of BSCLs following LASIK. A controlled study of the use of hydrogel BSCLs after LASIK in 200 myopic eye found that the majority of patients did not experience better postoperative comfort from the application of a BSCL after LASIK, nor did the BSCL protect from the occurrence of microstriae []. Another study compared the use of BSCLs to no lens wear immediately following LASIK and reported that 29 % of patients were intolerant to BSCLs, necessitating removal at one hour []. The authors concluded that BSCL wear was effective for up to four hours after LASIK to decrease symptoms, while flap oedema and the presence of mucoid secretions were limitations of overnight wear. In terms of pain control, a prospective investigation of the efficacy of BSCLs after LASIK compared to topical medications on the first postoperative day [] concluded that the use of topical medications was superior to the BSCL in terms of pain control and visual acuity. Additionally, patients preferred not wearing a BSCL.

The use of BSCLs after LASIK can alter corneal topography and increase corneal oedema, reducing uncorrected distance visual acuity []. The mechanism for this was both an increase in corneal asphericity, likely due to the mechanical pressure of the CL, and corneal flap oedema. The authors speculated that the oedema in the flap was due to preservatives in the topical medications. The finding of oedema in the flap was consistent with that reported by another group [].

Some beneficial effects of BSCLs on wound healing after LASIK have been reported. A prospective, randomised study evaluated the effect of a BSCL on fibrosis at the flap margin with 41 patients (82 eyes) fitted with a BSCL in one eye but not in the contralateral, control eye []. Pain and photophobia were milder in the eyes fitted with a BSCL than those with no BSCL, however the BSCL was associated with a foreign body sensation. While the BSCL did appear to improve healing at the flap margin, there were no differences in any of the other outcome measures at six months.

Evidence supporting the use of BSCLs for the prevention of epithelial ingrowth is equivocal based on three retrospective reports in the literature. The largest of these evaluated 16,702 eyes in 12,485 patients over a ten-year period who underwent an enhancement []. No differences were found in visual acuity or the rate of epithelial ingrowth between eyes that did or did not receive BSCL. The second, much smaller study also looked at the rate of epithelial ingrowth following an enhancement []. While the authors reported a potential trend towards an increase in epithelial ingrowth in the BSCL group, the study groups were small and there were no statistical differences reported. A third earlier study retrospectively evaluated the rate of epithelial ingrowth after LASIK included 783 eyes over a three-year study period, including eyes undergoing primary procedure and 108 undergoing enhancement []. All eyes were given a BSCL for the first day after surgery. In this cohort, only three eyes developed epithelial ingrowth Due to the small number of cases reported, the authors concluded that extensive cleaning of the stromal interface during surgery combined with BSCLs may decrease the rate of epithelial ingrowth, although there was no control group with no lens for comparison.

Only one report was found on the use of BSCLs in epi-LASIK []. This prospective study evaluated the effects of two different base curves (8.4 mm and 8.8 mm) on the corneal epithelium and postoperative pain. Twenty-seven patients were fitted with both base curves in a contralateral fashion. There were no differences in any of the outcome measures, except for uncorrected distance visual acuity, with a statistically significant improvement with the 8.8 mm base curve on day four postop visit that was no longer evident by day seven. Similarly, a significantly significant improvement in uncorrected visual acuity was noted with the 8.8 mm base curve lens in patients with higher levels of myopia preoperatively and keratometry measurements of ≥ 43 dioptres at day four post op but was no longer significant at day seven.

There is medium quality evidence supporting the use of BSCLs in the management of post-LASIK complications. In a report of 5896 eyes that had LASIK using a microkeratome, 95 eyes had intra-operative epithelial damage []. BSCLs were used to treat epithelial defects that were larger than three mm in size. All of these eyes healed in 1–3 days; 3 eyes with 4−5 mm defect were left with visually symptomatic irregular or against-the-rule astigmatism that was successfully treated with transepithelial phototherapeutic keratectomy. Another report of 5566 eyes that underwent LASIK using a microkeratome evaluated over a one-year period eight eyes that had recurrent epithelial loosening []. Lubrication and BSCLs were used in 4 eyes with the remaining 4 requiring anterior stromal puncture plus wear of BSCL for 1 month for resolution of symptoms. Additionally, a case of blunt trauma leading to a corneal flap dehiscence in a 32-year-old man with a history of LASIK was successfully treated with a BSCL [].

No differences were found in the incidence of corneal epithelial ingrowth and in visual outcomes after enhancement by flap lift when comparing those that were fitted in a BSCL after the procedure to those who were not []. Additionally, bacterial contaminants on used bandage lenses after LASIK or PRK have been characterised, but have not necessarily been associated with complications as usually only ocular commensal microorganisms are isolated [, , , ]

LASEK is a procedure in which an “epithelium only” flap is created under which the stromal ablation is performed. Only four studies to date have evaluated the use of BSCLs following LASEK. One study demonstrated that SiHy BSCLs were well tolerated and effective in patients undergoing LASEK, however it is important to note that no comparator lens or control group were used []. Two other research groups later compared the use of hydrogel and SiHy lenses after LASEK. Both groups concluded that SiHy lenses were superior to hydrogels as BSCLs after LASEK []. In the final study, the efficacy of two different generations of SiHy lenses were evaluated []. Greater discomfort and an increase in deposits on the lens surface were found with wear of a first-generation silicone hydrogel compared to the second-generation lens material. Whether the advantage is based on oxygen transmission, modulus, tendency to deposits, or another material feature remains unknown.

PTK is a procedure in which epithelial debridement and excimer laser ablation are used to treat anterior corneal disease including corneal dystrophies and scarring. Most evidence supporting the use of BSCLs after PTK ablation comes from prior work evaluating their use after PRK. A small case series investigating the use of BSCLs after PTK on patients with recurrent corneal erosions reported that eight eyes presented with erosions secondary to bullous keratopathy and all patients responded well to PTK with BSCLs [] In a small case series on the use of PTK in children, five eyes from five children (six to eight years of age) with superficial anterior scarring were treated to prevent the development of amblyopia []. All eyes were fitted with BSCLs postoperatively along with topical antibiotics, steroids, and artificial tears. Four eyes showed an improvement in best corrected visual acuity. There was no mention of the specific BSCL that was used.