Scleral Lens Practice: A Review from BCLA CLEARIn the second instalment from a series of 10 articles, Dr Melissa Barnett and Dr Karen G. Carrasquillo present an overview on scleral contact lenses, drawn from the British Contact Lens Association – Contact Lens Evidence-base Academic Report (BCLA CLEAR). WRITERS Dr Melissa Barnett and Dr Karen G. CarrasquilloThe BCLA CLEAR scleral publication provides a brief historical review of scleral lenses and a detailed account of contemporary scleral lens practise, including common indications and recommended terminology. This report summarises the latest research and clinical understanding on assessing lens fit, including optimal sagittal lens depth, back surface profile, fluid reservoir thickness, oxygen permeability, lens centration, movement, and wettability. A variety of optical and physiological challenges associated with scleral lenses are described, including options for the clinical management of a range of ocular conditions. The BCLA CLEAR scleral report reviews instrumentation that can assist with ocular health assessment and documentation, initial lens selection, haptic customisation, and troubleshooting. What is a Scleral Lens? • It is a lens fitted to vault over the entire cornea, including the limbus, and lands on the conjunctiva overlying the sclera. • It is filled with sterile preservative-free saline, creating a fluid-reservoir that provides ocular surface support, protection from the environment and visual rehabilitation. • Because it rests on the sclera and vaults the cornea, it provides great comfort. • It has broad indications across the entire corneal disease spectrum, i.e., irregular corneas and ocular surface diseases. • There is a broad range of diameters to choose from: 14–23mm. • Lenses are manufactured from high Dk fluorosilicone acrylate materials, some of which include: Roflufocon D, Roflufocon E, Hexafocon A, Hexafocon B, Tisilfocon A, and Fluoroxyfocon A. LEARNING OBJECTIVES On completion of this CPD activity, participants should be able to: 1. Understand a scleral lens and its indications, 2. Understand various fitting approaches and diagnostic fitting considerations of scleral lenses, and 3. Understand key fitting challenges and troubleshooting. Future applications of scleral lenses, which take advantage of their stability, are discussed; scleral lenses are currently being used as a stable platform for a range of optical applications, including wavefront guided corrections, low vision aids, and smart scleral lenses. The report also reviews the importance of practitioner intercommunication and collaboration in a scleral lens practice to reduce complications and increase fitting success. The BCLA CLEAR scleral report boons evidencebased recommendations to optimise patient outcomes in modern scleral lens practice. SCLERAL LENS INDICATIONS Historical Scleral Lens Indications (1980s) • High ametropia (aphakia and myopia, 44%), • Primary corneal ectasia (keratoconus, pellucid marginal degeneration, keratoglobus, 32%), • Post-penetrating keratoplasty (12%), • Ocular surface disease (7%). Modern Scleral Lens Indications • Primary corneal ectasia (53%), • Ocular surface disease (18%) , • Post-penetrating keratoplasty (17%). Additional Scleral Lens Indications • Simple refractive errors (including presbyopia). Scleral Lens Terminology • The optic zone – houses the refractive correction of a scleral lens and can be customised, similar to rigid corneal lenses. • The transition zone – connects the optic and landing zones and is often referred to as the limbal, peripheral, or intermediate zone. • The landing zone – contacts the conjunctival tissue overlying the sclera and may be spherical, toric, quadrant, multi-meridian specific, or completely customised, based on an ocular impression. OCULAR SURFACE SHAPEUnderstanding of ocular surface shape and elevation has contributed to knowledge about scleral lens designs and fittings. In particular, we now understand that back surface landing customisation improves fitting outcomes, while also improving patient comfort and vision, increasing wear time and patient satisfaction. When it comes to ocular surface shape, three main areas to discuss are scleral elevation, scleral curvature, and corneoscleral junction. Below is a summary of key points related to each topic. INSTRUMENTATION There are various tools and instruments that can help with ocular health assessment and monitoring, scleral lens fitting and troubleshooting: • Corneoscleral Profilometers, • Optical Coherence Tomography (OCT), • Anterior Segment Photography, and • Specular Microscopy. Figure 1. Slit-lamp photography of a scleral lens with adequate haptic landing in each quadrant on the left eye of a patient with dry eye disease. Each slit-lamp image is accompanied by its corresponding OCT image, showing a different way to assess the haptic to conjunctiva/sclera relationship. Image courtesy of Dr Karen G. Carrasquillo. PRESCRIBING SCLERAL LENSESThere are various approaches to scleral lens fitting and lens prescribing. The main approaches and techniques are: • Empirical, • Impression-based, and • Diagnostic. Empirical and impression-based fittings today rely on ocular surface elevation data to design the first pair of lenses, without necessarily applying a trial lens at the first visit. These techniques aim to reduce chair time with higher first fit success rates. Some practitioners may still need to apply trial lenses to obtain refractive data, but this usually can be obtained from previous rigid corneal lens data. If the conjunctival surface is negatively impacted from previous scleral lens wear, usually these techniques require cessation of lens wear for a few days, prior to scan/impression acquisition. Despite the advent of these technologies, diagnostic lens fitting continues to be highly utilised. When using diagnostic lenses, the recommendation is to first focus on the lens diameter, sagittal height, and back surface profile. FITTING PARAMETERS Beyond the parameters that are key for diagnostic lens fitting, there are other important fitting parameters that are important to take into consideration: Fluid Reservoir Thickness • Central/Apical Vault: o Reservoir thickness at the location of greatest corneal elevation, o Location can vary depending on corneal shape/condition, o Recommended target is 300–500μm immediately after application to 100– 300μm after settling, and o When using high Dk lenses, there are small differences in oxygen uptake and corneal oedema, despite varying apical vaults. ◆ Special consideration should be given to compromised endothelium: o Total thickness decreases ~100-200μm over an eight-hour period, and o Magnitude of settling varies to some extent by lens diameter. ◆ Not influenced by fluid use to fill reservoir. o Long-term settling is difficult to predict 2’ lens design, diameter, conjunctiva, and scleral lens tissue properties. Limbal Vault • Must vault anterior corneal surface at limbus. • Proper vaulting avoids oedema, neovascularisation, and compromise to limbal stem cells. • Manufacturer recommendation after lens settling range between 50μm and 100μm. Oxygen Permeability • Highly oxygen permeable rigid materials (~≥100 Dk) allow higher oxygen transmission: o Results in less bacterial adhesion to the corneal epithelium following overnight lens wear, o May reduce the possibility of adverse hypoxic complications, and o Material is less scratch resistant. Wettability • Has an impact on vision and comfort. • Influenced by quality and quantity of tear film, blink rate, conditioning solutions, and lens material. • Aided by ionisation of the lens surface with oxygen plasma. • Improved by the application of a polyethylene glycol polymer coating following plasma treatment. • Lens removal, cleaning, and reapplication may be warranted to improve wettability. SCLERAL LENS EVALUATION After lens application, it is recommended to confirm adequate placement, check for bubbles (Figure 1), and assess the central vault. After these have been determined to be appropriate, it is advised for the lens to settle for about 30 minutes. After minimum settling, biomicroscopy assessment can be done in an ‘in-out’ approach to evaluate the fit from the lens centre to the edge. SCLERAL LENS CHALLENGES The Fluid Reservoir (Midday Fogging and Epithelial Bogging) Fluid reservoir debris, otherwise known as midday fogging, is commonly encountered in 26–46% of patients. Midday fogging is currently managed by lens removal and reapplication, fitting modifications (improving landing zone alignment or reducing reservoir thickness), using a more viscous application fluid, and treating underlying ocular surface disease including eyelids, allergies, and dry eye disease. Corneal epithelial ‘bogging’ are anterior corneal irregularities following scleral lens removal with an uneven distribution of Figure 2. Illustration of undesirable application bubble trapped in the fluid-reservoir compartment between the back surface of the scleral lens and the cornea. Picture courtesy of BostonSight. Table 3. Evaluating the fit of a scleral lens. sodium fluorescein. Bogging is managed by daily mid-day lens removal, rinsing, and reapplication, and can otherwise be monitored. Lens Fitting-to-Optics RelationshipScleral lenses have been reported to have great visual rehabilitation benefits and potential, in both irregular cornea and ocular surface disease. 1,2Despite this, there are some fitting relationships that may have an impact on the lens optics. The bullets below describe them and how to minimise them: • Scleral lenses typically decentre inferotemporally. • Inferior decentration can induce a small base down prismatic effect and create residual higher order aberrations. • Residual astigmatism may arise due to lens flexure. • Optical effects can be minimised by reducing the extent of decentration by fitting a toric or customised landing zone and reducing apical clearance. • Front surface lens wettability influences visual performance during scleral lens wear. Corneal Oedema Gas permeable materials have evolved from rigid lens materials, from glass to PMMA to low Dk and then hyper-oxygen permeable rigid lens materials (Dk ≥ 100). Conjunctival Prolapse Both compression and suction forces may contribute to conjunctival prolapse, defined as an elevation of the perilimbal conjunctival tissue that may encroach the limbus. This phenomenon is often benign and can be monitored – although long-term effects are unknown. Because this is usually a result of excessive clearance at the limbus, reducing limbal clearance often helps resolve it. SCLERAL LENS APPLICATION AND REMOVAL • Patient education materials are available from various resources. • Since scleral lens application solution has extended residence time with the cornea, it is important to use preservative-free solutions to fill the lens bowl. • Nightly disinfection with a hydrogen peroxide or multipurpose solution is recommended to prevent infection. • Scleral lens application and removal can be done with a rubber plunger or without any tools or aids, using only fingers (Figures 2 and 3). • Approximately 25% of patients cease lens wear, typically due to a lack of motivation, discomfort, or limited improvement in visual acuity. COLLABORATIVE CAREAs the scope of practice continues to expand, sub-specialisation is becoming increasingly practical. Scleral lens practice requires a specific skillset beyond the scope of general primary eye care. Intra-profession referrals are becoming more common based on increasing sub-specialties. In addition to the skillsets needed to analyse and modify scleral lenses, customised technology, such as corneoscleral topography and anterior segment OCT, may be required to provide the highest quality care. In some cases, the practitioner should be knowledgeable about disease management strategies to optimise the outcome for scleral wearers. A wide range of systemic diseases can present with ocular manifestations which are managed by scleral lens wear. The most common are: • Ocular graft-versus-host disease, • Stevens-Johnson syndrome, and • Sjögren’s Syndrome. Collaboration with medical specialties is Figure 3. A: Tripod and B: Two-finger method to hold a scleral lens for application without assistive devices. From Scleral Lens Education Society Figure 4. Scleral lens application assisted by holding scleral lens in a large suction cup/plunger. Picture courtesy of BostonSight. Figure 5. A: Cornea showing signs of superficial keratitis and filamentary keratitis in Graft versus Host Disease and B: cornea with conjunctivaliation and limbal stem cell deficiency on Stevens-Johnson Syndrome. Both scenarios can be treated and managed with scleral lenses. Pictures courtesy of BostonSight. sometimes required in scleral lens wearers. The most common are: Scleral Lens PlatformsScleral lenses are currently being used as a stable platform for a range of optical applications including wavefront guided corrections, low vision aids, and smart scleral lenses. CONCLUSIONS The CLEAR scleral lens review concludes in identifying several avenues where collaboration in patient care can improve outcomes, particularly in penetrating keratoplasty. Also covered is the use of scleral lenses as a platform for wavefront guided vision correction, largely due to the stability that scleral lenses provide, and for smart devices including biometric readers, providing a simulated iris and augmented reality. Scleral lenses are an important method for visual rehabilitation in irregular corneas, therapeutic treatment of ocular surface disease, and the correction of refractive error in healthy eyes, especially when other modalities fail. A detailed understanding of ocular anatomy and ocular surface shape is necessary to optimise scleral lens design, vision and comfort, and ocular physiology for each eye. Either empirical or diagnostic lens fitting can be performed; instrumentation can assist with scleral lens fitting and troubleshooting. Various unique physiological responses may occur with scleral lenses. In general, they are safe, with a low incidence of microbial keratitis when worn on a daily wear basis. Practitioner collaboration and intercommunication are essential in a scleral lens practice to increase fitting success. Scleral lenses are a stable platform for a range of optical applications such as wavefront guided corrections. Due to their stability, scleral lenses may be used for smart devices including biometric readers, providing a simulated iris and augmented reality. To earn your CPD hours from this article visit: reviewfrom-bcla-clear. The full report and supplementary information can be accessed at article/S1367-0484(21)00015-1/fulltext. The BCLA CLEAR Summary report is a short bitesize evidenced based practical guide for clinicians, bringing together the key findings from the report. Accessed via CLEAR ( Listen to the BCLA CLEAR Scleral lens podcast - podcast/bcla-clear-episode-5-scleral-lenses/ id1524673927?i=1000545160522. This article is based on an original article published in the United Kingdom in Optician. Acknowledgement and recognition to Melissa Barnett, Claudine Courey, Daddi Fadel, Karen Lee, Langis Michaud, Giancarlo Montani, Eef van der Worp, Stephen Vincent, Maria Walker, Paramdeep Bilkhu and Philip Morgan who were the paper’s authors, and the educational grants from Alcon and CooperVision. The original paper was published in Contact Lens and Anterior Eye journal. Original paper: Barnett M, Courey C, Fadel D, Lee K, Michaud L, Montani G, van der Worp E, Vincent SJ, Walker M, Bilkhu P, Morgan PB. CLEAR -Scleral lenses. Cont Lens Anterior Eye 44 2021 270-288. Dr Melissa Barnett is a principal optometrist at the University of California, Davis Eye Center. She is Chair of the American Optometric Association Contact Lens and Cornea Section, a Fellow and Global Ambassador of the British Contact Lens Association, and is Past President of The Scleral Lens Education Society. Dr Karen G. Carrasquillo is Vice President of Clinical and Professional Affairs at BostonSight. In addition, she is an adjunct clinical professor at the New England College of Optometry, an adjunct clinical professor at the school of optometry, MCPHS University, Advisory Board member for the Gas Permeable Lens Institute (GPLI), Fellow of the American Academy of Optometry (FAAO), Fellow of the Educational Society of Scleral Lenses (FSLS), Fellow of the British Contact Lens Association (FBCLA), and Global Ambassador of the BCLA. The editors for this series are Dr Debarun Dutta and Neil Retallic. Five Clinical Pearls to Start Scleral Lenses in Your Practice 1. Develop a true clinical interest – enough to dedicate to learning and mastering the subject. 2. Educate on the subject matter – there are many online webinars and resources on the fitting and troubleshooting of scleral lenses. 3. Start with one or two designs and become proficient with these, before exploring more designs. 4. Start with mild and moderate cases and build up from there. 5. Promote services on your clinic’s website and send letters to introduce you and your services to potential referral sources in the area. References 1. Barnett M, Carrasquillo KG, Schornack MM. Clinical Outcomes of Scleral Lens Fitting with a Data-driven, Quadrant-specific Design: Multicenter Review. Optometry and vision science : official publication of the American Academy of Optometry 2020;97(9):761-5. https://doi. org/10.1097/opx.0000000000001576. 2. Rosenthal P, Croteau A. Fluid-ventilated, gas-permeable scleral contact lens is an effective option for managing severe ocular surface disease and many corneal disorders that would otherwise require penetrating keratoplasty. Eye Contact Lens 2005;31(3):130-4. https://doi. org/10.1097/01.icl.0000152492.98553.8d.

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