By Melissa Barnett, OD, FAAO, FSLS, FBCLA
The SynergEyes VS scleral lens features scleral toricity and linear landing zones. The popularity of the scleral lens modality is colossal amongst specialty contact lens practices and continues to grow in general optometric practices. There are three major categories for scleral lenses: restoration and support of the ocular surface, visual rehabilitation and correction of corneal irregularity and pain attenuation.
Scleral lenses for ocular surface disease are especially beneficial due to the preservative-free saline used in the bowl of the lens to continuously bathe, protect and restore the ocular surface via the post-lens tear reservoir. Dry eye disease is a highly prevalent condition with symptoms including dryness, grittiness, foreign body sensation, debilitating ocular pain, photophobia, visual fluctuation and distortion. Multiple studies have demonstrated that dry eye disease can negatively affect the quality of life. Although dry eye is increasingly prevalent, many patients are not diagnosed nor treated. There is a massive potential opportunity to address this highly prevalent condition.
Where should scleral lenses fit into the dry eye treatment protocol?
For mild to moderate dry eye without systemic co-morbidities, scleral lenses should not be used as the primary therapy. Conventional treatment options should be tried first including environment modifications, preservative free eyedrops, prescription dry eye medications, eyelid hygiene, nighttime lubrication or goggles and punctal occlusion. When conventional treatments are insufficient, scleral lenses are a viable management option for dry eye patients. Additionally, scleral lenses have been indicated for the treatment of conditions associated with neuropathic ocular pain.
According to DEWS II, there is “increasing appreciation that daily wear of a rigid gas permeable scleral lens may play an important role in the management of moderate to severe dry eye disease.” The DEWS II report positions scleral lenses are tertiary therapy, after prescription medications and overnight treatments such as ointment or moisture goggles, and before long term use of steroids, amniotic membrane grafts, surgical punctal occlusion or other surgical procedures such as tarsorrhaphy or salivary gland transplantation. Additional step-three therapies include oral secretagogues, autologous/allogenic serum eye drops and soft bandage contact lenses.
Therapeutic scleral lens indications for ocular surface disease include dry eye syndrome, exposure keratitis, neurotrophic keratitis, graft vs host disease, Stevens-Johnson syndrome, ocular cicatricial pemphigoid, chemical burns, limbal stem cell deficiency, Sjögren’s syndrome and other systemic autoimmune diseases and persistent epithelial defects.
Tangible Hydra-PEG is a novel surface treatment comprised of a 90% water PEG-based polymer mixture that is permanently bonded to the surface of the contact lens made from the lubricant polyethylene glycol (PEG). Tangible Hydra-PEG shields the lens from the ocular surface and tear film, minimizes friction and deposition, improves lens wettability, tear film breakup time and deposit resistance, ultimately enhancing contact lens comfort.
A recent poster presented at the Global Specialty Lens Symposium (GSLS) compared lens comfort and dry eye symptoms of dry eye scleral lens wearers fit with Tangible Hydra-PEG treated and untreated scleral lenses. Dry eye signs, comfortable lens wearing time, quality of vision, and lens related ocular surfaces changes were assessed. Treated scleral lenses demonstrated superior comfort and improved dry eye symptoms compared to the untreated lenses. Ocular surface changes and frequency of foggy vision were reduced with treated lens wear. The authors concluded that Tangible Hydra-PEG is an effective technology which may improve outcomes for scleral lens wearers with dry eye.
Special lens considerations
Incorporating back surface toricity can help reduce lens decentration, lens distortion, excessive debris, the formation of air bubbles, conjunctival prolapse, localized conjunctival vessel blanching[7,8] and lens impingement[9,10]. Consequently, patients experience improved comfort, increased wearing time, overall satisfaction, better visual quality and enhanced optical correction[11-13]. Studies have demonstrated that scleral asymmetry increases towards the extraocular muscles and that the nasal meridian is flatter than the rest of the scleral meridians. Additionally, anterior segment OCT and scleral profilometry studies have shown that the transition between the cornea and sclera is tangential.
An observational study evaluated 133 patients fit with a scleral lens with a bitangential periphery and linear landing zone. In this design, the linear landing zone is determined by an angle relative to a line perpendicular to the optical axis. This angle corresponds to the tangential angle where the lens aligns with the sclera. In a nonrotationally symmetrical design, the linear alignment zone is manufactured with two different angles in two perpendicular meridians, creating a bitangential periphery. This nonrotationally symmetrical back-surface toric periphery scleral lens is designed to fit an eye with scleral toricity. Since the lens is rotationally stable, residual astigmatism can be corrected with front surface toricity. Seventy nine percent of patients scored comfort as either a 4 or 5 (out of 5), and 82% wore lenses 12 hours or longer a day. The majority of lenses (81%) were 16.00mm in diameter (median, 16 mm; range, 15.5 to 17 mm). The median corrected distance visual acuity was approximately 20/21. Fitting characteristics revealed ideal scores for centration (91%) and movement (83%). This study demonstrated that scleral lenses with a bitangential peripheral geometry may perform well both objectively and subjectively in eyes to correct irregular astigmatism, ocular surface disease or other corneal pathologies.
The SynergEyes VS scleral lens is designed with a bitangential periphery and linear landing zone, aiding the ease and improving the outcomes of scleral lens fitting.
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