Deborah S. Jacobs, Lynette K. Johns and Hong-Gam Le

Introduction

Although contact lenses are typically thought of as a cosmetic option for the correction of refractive error, they can also play a therapeutic role after trauma, surgery, and in the treatment of ocular disease. The following is a brief review of the history of contact lens and the innovations that allowed for therapeutic use in ocular surface disease (OSD). The rationale behind and characteristics of various lenses that can be used for ocular surface disease will be reviewed, as will general approach to use, and a review of the prevention and treatment of complications. Finally, publications and experience with contact lens within various categories of ocular surface disease will be reviewed.

Because the market for therapeutic, as opposed to cosmetic, contact lenses is small, innovations, labeling, and marketing of contact lenses, for the most part, has been geared to cosmetic indications and correction of ammetropia rather than therapeutic applications. The few lenses developed specifically and only for therapeutic use (Plano T, Permalens, Protek) have generally been discontinued. Clinicians often will choose to use a lens ‘off-label’ based on familiarity, material, design, or immediate availability. The term ‘bandage lens’ is not typically part of United States Food & Drug Administration (FDA) labeling; labeling typically indicates if a lens is approved ‘for therapeutic use’ and ‘as a bandage.’

History of Contact Lenses and Innovations Allowing for Therapeutic Use

The first description of contact lenses in the medical literature was a report on contact lenses by Adolf Eugene Fick in 1888.¹ Pearson,² in his review of the history of contact lenses, reports Karl Otto Himmler as the first manufacturer of contact lenses. Pearson describes reports of contact lenses ranging in diameter from 15 to 22 mm in 1888, 1888, and 1889 by Fick, Kalt, and Muller, respectively, all made of glass. Examining these early glass and then polymethyl methacrylate (PMMA) large-diameter lens designs retrospectively exposes various reasons for failure, most prominently, hypoxia related to the impervious nature of glass or PMMA. This problem was circumvented in the middle of the last century through the use of small diameter PMMA corneal lenses that allowed the majority of the cornea access to atmospheric oxygen, with some transmission to the area under the mobile contact lens via the tear film. Overwear syndrome could arise, due to hypoxia under a tight or immobile lens. These lenses were used primarily for treatment of refractive error because there was invariably corneal touch and underlying hypoxia, both of which would be a challenge in the setting of ocular surface disease. Two innovations in material science allowed for contact lens to enter the therapeutic armamentarium: rigid gas-permeable polymers and soft hydrogels.

The introduction of rigid gas-permeable polymers into contact lens manufacturing allowed for better physiological tolerance of corneal lenses and the reintroduction of large-diameter scleral lens designs in the early 1980s.³ Wide use of lenses made of these materials has been limited by challenges of corneal RGP lens fitting and the perception that a ‘hard’ lens cannot serve as a ‘bandage.’ Rigid gas-permeable scleral lenses that vault the cornea entirely can play a role in the treatment of ocular surface disease, as presented throughout the remainder of the chapter.

The introduction of hydrophilic gels for biologic use, and in particular for contact lens, by Czech chemist Otto Wichterle in the 1960s led to the availability of ‘soft’ lenses within a decade. Soft lenses are easily fitted, with greater range of tolerance for a given lens profile. The potential for therapeutic use was recognized contemporaneously with the introduction of soft contact lenses. In the decades that followed, modifications to materials, including increased water content or silicone for the sake of increased oxygen permeability, or modifications to improve wetting, were introduced in the field of soft contact lenses. Oxygen transmission has been held as the paragon for therapeutic lens, but mechanical interaction with the surface is also key to tolerance and clinical effectiveness. A North American survey of ‘bandage’ soft lens use by optometrists and ophthalmologist in 2002 found that 72% of respondents had prescribed soft contact lenses for therapeutic purposes, most typically for corneal wound healing and management of postoperative complications.⁴

In the conventional practice of contact lens fitting for correction of refractive error, the presence of ocular surface disease is a relative contraindication to contact lens wear. Nevertheless, contact lenses may be specifically indicated despite surface breakdown, history of infection, local or systemic immunosuppression, or the presence of underlying systemic disease, when the lens material, parameters of fit, and wear regimen are given thoughtful consideration.

In the 2007 Report of the International Dry Eye Workshop,⁵ contact lens wear is among the treatment recommendations by severity level among level 3 interventions along with autologous serum tears and permanent punctal occlusion, with systemic treatment and surgery listed as level 4 interventions. Some are skeptical that a contact lens for ocular surface disease is therapeutic. One might ask how an object ‘hard’ or ‘soft’ can help an eye that is dry (and inflamed). Clinical observations are that an appropriately chosen, well-fitted therapeutic contact lens can:

Consideration of mechanisms underlying these observations, some of which remain part hypothetical, is beyond the scope of this chapter.

Characteristics of Soft Lenses Used for Treatment of Ocular Surface Disease

Important variables to consider in choosing a soft lens for OSD include material Dk and diameter. Labeled indications and wearing schedules are also variables to consider. Dk refers to the oxygen permeability of a given lens material. Dk is expressed in ISO/Fatt units × 10⁻¹¹(cm³O₂)(cm)/[(sec(cm²)(mmHg)]@35°C. Convention is that it is reported as Dk/L or Dk/T for thickness of a −3.00 power lens of particular material and design. Among hydrogel soft lenses, water content, which is expressed as a percentage, has paradoxical implication for patients with aqueous tear deficiency. One might think that increased water content is better for a therapeutic lens in a dry eye patient, but this is not necessarily the case, as a higher water content soft lens may act as a sponge and be prone to problematic adherence.

The prototype therapeutic contact lens was the Bausch & Lomb Plano T, a hydrophilic hydrogel introduced in the 1970s specifically as a therapeutic lens. It had low water content (38%), low oxygen permeability (Dk 8.4), and was thick. Clinically, it reduced pain, promoted epithelialization, sealed leaks, and induced corneal edema (which was good for leaks but bad for other indications). The Permalens (CooperVision Inc, Fairport, NY) represented a significant advance with higher Dk value of 42. It was developed as an extended-wear lens for aphakia to be changed monthly, but its properties in low powers were advantageous over a Plano T lens for therapeutic indications. When programmed replacement and disposable lenses for correction of refractive error entered the marketplace, clinicians chose these for OSD because of immediate availability among trial inventories and relative low cost,6,7 even though they were not labeled for therapeutic use. The Silsoft (Bausch & Lomb Inc, Rochester, NY) is the most gas-permeable soft lens (Dk 340); it is specifically approved for extended wear for the therapeutic indication of correction of pediatric aphakia. These lenses typically have required high lens plus power and larger diameter to support that power, all reducing availability of atmospheric oxygen to the cornea.⁸

In the last decade, very high Dk silicone hydrogel (SiHy) material and lenses have been developed and labeled specifically for therapeutic use in addition to cosmetic use. There have been reports of the utility of SiHy lenses as a therapeutic option across the spectrum of ocular surface disease.9,10 Epidemiologic studies have not found a lower rate of infection with these newer materials,^11,12 but there should be advantages conferred in OSD simply because of their higher oxygen transmission.

The authors recommend that clinicians choose a high Dk lens labeled for extended wear and/or therapeutic use as a first choice for therapeutic use in OSD (Fig. 35.1). Potential complications, including lens loss, lens deposits, discomfort, infectious keratitis and ulceration, and tight lens syndrome⁷ should be reviewed. The risks and benefits of overnight wear should be reviewed with the patient and weighed against the alternatives for the treatment of their particular disease process. It is probably not advisable to use a daily disposable lens on an extended wear or therapeutic basis as they were not developed or manufactured for those uses.

Table 35.1 presents some lenses of historical and current interest, with their Dk, percentage water content, and labeling. Some soft lenses are labeled for therapeutic use on an extended wear basis. Others are labeled for extended wear, but not specifically for therapeutic use. Lenses labeled for daily wear could be used ‘off- label’ on an extended wear basis. Lenses labeled for extended wear on a cosmetic basis could be used ‘off-label’ on a therapeutic basis.

Very Large Diameter Soft Lenses

There are very-large-diameter hydrogel lenses (16–24 mm diameter) that have special utility in instances of OSD in which there is history or likelihood of poor soft lens retention. Profound aqueous deficiency, incomplete blink, lid abnormalities, eye rubbing, and exposure can all be contributory to poor retention (Fig. 35.2). Large-diameter soft lenses sold in range of base curves for a given diameter and the lenses with larger diameters will have central and peripheral zones of different diameters. Ideally, an assortment of diameters and curvatures are kept on hand, and best fit, tolerance, and retention are assessed with empiric trials. Large-diameter soft lenses in SiHy materials have recently become available on a custom-order basis.

Characteristics of Scleral Lenses Used for Treatment of Ocular Surface Disease

In 1983, Ezekiel³ reported the use of gas-permeable material in a scleral or ‘haptic’ lens solving the problem of hypoxia in a large-diameter contact lens. This innovation was applied successfully in that decade in innovative large-diameter RGP lens designs at centers of excellence around the world.^13–15 The Dk of RGP materials has exceeded that of soft lens materials until the advent of SiHy materials for soft lenses in the past decade. Once hypoxia was conquered by these high-Dk RGP materials, lens suction was the next challenge. Suction was circumvented, literally, by fenestration, which allows for air ventilation, or by haptic design with channels or contours that allow for fluid ventilation with no intrusion of air bubbles. Air ventilation is often satisfactory for eyes with optical indications, such as keratoconus or post-keratoplasty astigmatism, but air bubble(s) are typically not well tolerated in ocular surface disease. Reports of utility of RGP scleral lenses for OSD in general have emerged over the past two decades.^{13,14,16–19} Success with this modality is dependent on the motivation and skill set of the clinician, as well as access to specialty lens manufacturing lab. A true scleral lens, well-fitted, with features, including a fluid reservoir, little movement, and no corneal touch, can provide support and protection for the corneal epithelium beyond that offered by any soft lens, and can be tolerated and retained in setting in which a soft lens is not.

There is a category of specialty contact lenses that is called ‘mini-scleral,’ ‘semi-scleral,’ and ‘corneoscleral’ lenses. The definitions and distinctions are evolving, and classifications may be based on the diameter, characteristics of fit or both. Generally, these lenses are 13–16 mm, made of high-Dk materials, may contact the cornea at the apex or peripherally, and the principles of fit are similar to those for an RGP corneal lens rather than a true scleral lens.²⁰ These larger RGP lenses are sometimes included among reports of scleral lenses. Although they may be more easily fitted and initially well tolerated, a reduced bearing zone and deliberate or unrecognized corneal touch centrally and at the limbus make these lenses less appropriate for patients with ocular surface disease as they may induce erosion, scarring and neovascularization in areas of contact, compression, or impingement.

Typically, scleral lenses are inserted and removed on a daily-wear basis with overnight disinfection. Newer materials developed in the past decade for overnight orthokeratology and FDA approved for that use, might be used in a large-diameter lens on a daily or overnight regimen on an off-label basis. The challenges of fitting the eye and training the patient or caretaker in daily insertion and removal limit the use of scleral lenses as a short-term ‘bandage lens.’ In certain circumstances, continuous wear coupled with daily removal, disinfection, and reinsertion may be appropriate for support of the ocular surface.21,22

PROSE Treatment

PROSE (Prosthetic Replacement of the Ocular Surface Ecosystem) treatment is an interdisciplinary paradigm that uses custom-fabricated prosthetic devices to replace and/or enhance the function of the ocular surface ecosystem, improving vision, comfort, and supporting the ocular surface. The device used in PROSE treatment was approved by the FDA in 1994 for daily wear in the treatment of irregular astigmatism and ocular surface disorders. Over the past 20 years, the PROSE device has been referred to as the Boston Scleral Contact Lens, the Boston Scleral Lens, the Boston Scleral Lens Device, the Boston Scleral Lens Prosthetic Device, and the Boston Ocular Surface Prosthesis (BOS-P).

The critical design and fitting features in PROSE treatment are that the device is fitted with no corneal contact, with fluid ventilation, and with minimal movement. One of the design features that distinguishes a PROSE device from a conventional scleral lens is that the contour of a PROSE device is defined mathematically by software that uses spline functions rather than by a superposition of base curves, yielding front and back surface profiles that are malleable and junctionless. At insertion, the device is filled with sterile saline or artificial tears, which remains oxygenated, due to the gas permeability of the material (Fig. 35.3). This fluid exchanges minimally with the precorneal tear film because of the precision of the fit. PROSE devices are distinguished from conventional scleral lenses in the degree to which they are customized per eye in order to eliminate movement, conjunctival impingement, and tissue compression that might ultimately reduce patient comfort and physiological tolerance.

A PROSE device creates a transparent and smooth optical surface over the irregular, damaged or diseased cornea. It reestablishes a healthy ocular surface environment by creating an expanded artificial tear reservoir that provides constant lubrication while maintaining necessary oxygen supply. A PROSE device then supports the fragile ocular surface by shielding the cornea and conjunctiva against insult from the environment and lids. PROSE treatment promotes healing, improves vision by masking surface corneal irregularities, and mitigates pain and photophobia by supporting and stabilizing the ocular surface (Fig. 35.4).

A 2000 report¹⁷ reviewed the experience with PROSE for treatment of OSD in 49 patients (76 eyes). Improvement in best-corrected visual acuity (defined as a gain of two or more Snellen lines) was observed in 40 (53%) of the eyes. Forty-five (92%) of 49 patients reported improvement in quality of life from reduction in photophobia and discomfort. In a report from 2010,¹⁹ 101 consecutive patients seen in consultation for PROSE treatment in 2006 were reviewed. The full spectrum of corneal disease, including corneal ectasia and postoperative astigmatism is represented, but nearly half of patients (38 of 80) who completed fitting were referred for treatment of OSD. Mean visual acuity (VA) in the OSD cohort improved by −0.22 (logMAR). The authors report an increase in mean NEI VFQ-25^23,24 scores for the entire cohort from 57.0 to 77.8. Findings were similar for the OSD group, with only two patients recording a decrease in VFQ score in this group. Greater benefits in the VFQ subcategories of eye pain, photophobia, and role difficulties were seen in the OSD group than in the ectasia and astigmatism subgroup. Cost effectiveness²⁵ of PROSE treatment in this cohort was also reported. As availability of PROSE treatment has increased, reports of clinical impact in cohorts with subgroups of OSD have arisen both in the United States¹⁵ and abroad.²⁶

Prevention and Treatment of Complications

Microbial keratitis, sterile melt, and corneal neovascularization are potential complications of contact lenses for ocular surface disease. In the absence of ocular surface disease, it is established that rates of infection is highest with extended wear, compared to daily wear regardless of soft lens type, and that RGP lens wear has the lowest infection rate.11,12 Lens wear in the presence of punctate keratopathy or frank geographical defect of the corneal epithelium can be presumed to put the cornea at higher risk of infection, as would concurrent steroid use. There are no good data on prophylaxis or infection rate for contact lens use in the setting of OSD.

Approaches vary from one setting or clinical perspective to the next. Most clinicians would use antibiotic prophylaxis for any contact lens wear in the setting of a frank corneal epithelial defect, with agent/vehicle selected based on breadth of coverage, toxicity, cost, and availability. Later-generation fluoroquinolones and polymyxin/trimethoprim are good choices; aminoglycosides are sometimes chosen, but use in OSD should be limited, due to potential toxicity with continued use. Some clinicians favor institution of a reduced-frequency prophylactic regimen to avoid toxicity, but argument can be made for use at labeled frequency to avoid emergence of resistance. Some clinicians prescribe prophylactic antibiotics for any overnight wear in OSD, while other clinicians might prescribe antibiotics only if there is concurrent steroid use. It is practice at the authors’ center, to use antibiotic prophylaxis only for overnight lens wear, in the setting of frank epithelial defect, regardless of lens type. The authors do not use antibiotic prophylaxis simply because of concurrent topical steroid use or for overnight wear in general, even in the presence of punctate keratopathy.

Infectious or sterile melt can accelerate under a lens, due to local hypoxia and/or stagnation of the precorneal tear film, which may contain lytic enzymes and toxic metabolites. Any patient fitted with a contact lens in the setting of an epithelial defect, or history of microbial or sterile ulceration, should be monitored closely, and warned to seek attention for any signs or symptoms of ulceration. Non-compliance may be a reason to seek an alternative other than therapeutic lens, such as tarsorrhaphy, in such cases.

Corneal neovascularization is a subacute complication of therapeutic contact lens wear, particularly in the setting of persistent epithelial defects, inflammatory processes, tight lens, or low Dk values. When neovascularization occurs, consideration must be given as to whether it is related to lens material, design and/or fit, or to the underlying disease, because treatment approaches vary, and lens discontinuation is not necessarily required. Vigilance and interdisciplinary collaboration between ophthalmology and optometry is required to avoid or treat this complication of contact lens wear when it arises in the setting of OSD. Maneuvers, such as switching to a higher-Dk lens, avoiding lens care products with epithelial toxicity, and introduction of topical steroid may allow for maintenance of the surface and regression of vessels without requiring the discontinuation of contact lens wear. At the authors’ center, VEG-F inhibitors have been used as adjunct to PROSE treatment in the treatment of corneal neovascularization associated with OSD.²⁷

An area of particular challenge is OSD in the setting of advanced glaucoma. Glaucoma patients may have surface breakdown resulting from either toxicity of topical agents, preservatives used in their formulation, and/or limbal stem cell deficiency (LSCD) from prior surgical interventions. Presence of a filtering bleb or tube shunt is a relative contraindication to contact lens wear in general and scleral lens fitting in particular because of risk of erosion and/or infection in an eye with direct communication between the anterior or posterior chambers and the subconjunctival space. The presence of the tube and plate(s) of a valve shunt may preclude a stable contact lens fit and may put the overlying conjunctiva at risk of erosion. Large-diameter hydrogel lenses are sometimes used for bleb leaks, and might be an appropriate choice for OSD in the presence of a filtering bleb or shunt. If a tube shunt is required for a patient with pre-existing cornea or OSD, it may be advisable to suggest to the surgeon pars plana entry for the tube and very posterior placement of the plates, using a long tube to facilitate subsequent-contact lens fitting and wear. PROSE devices can be fitted, with difficulty, in some patients with glaucoma tubes and trabeculectomies, which are usually relative contraindications to contact lens wear in general, particularly with scleral lens wear. Device modification after manufacture is the primary approach to dealing with limbal variants that are related to previous surgery.²⁸

Contact Lens for Specific Ocular Surface diseases

Conclusion

The successful treatment of ocular surface disease requires attention to four guiding principles. There must be treatment of underlying local processes, and there must be treatment of underlying systemic processes. The environment at the ocular surface must be optimized and this is the role of the contact lens. Finally, adequate progenitor and amplifying stem cells must be present. Clinicians will serve their patients well to be familiar with the full range of therapeutic contact lens options for the treatment of OSD.

References