Magic and myopia in Las Vegas

The topics included What is the ideal fitting characteristics of a scleral lens to minimise physiological disturbance to the scleral and conjunctiva? What effect does scleral lens wear have on IOP and optic nerve health? And, Are we suffocating the corneae with scleral lens wear? Key take home messages included:

• Due to the tears having a Dk of ~80, this reservoir behind the scleral lens is the rate limiting step for oxygen getting to the cornea. Even with hyper Dk materials, if you need maximal oxygen for fragile eyes such as corneal grafts, ensure low tear reservoir thickness if possible.
• Freeform lenses created with corneal-scleral topography may show more movement on the eye compared to conventional scleral lenses, meaning potentially more lens awareness initially for patients.
• Be aware that conjunctival compression from a scleral lens can take over three hours to resolve, relevant if taking corneo-scleral topography for a freeform scleral refit.
• Scleral lenses can have uses when fitted to eyes with hypotony following trabeculectomy surgery, to compress the bleb and increase IOP!
• Matrix metalloproteinases (MMPs) in the tears increase with scleral contact lenses but are not relatively higher in patients with ‘midday fogging’ compared to those without, suggesting inflammation is not the cause of build-up of proteins and lipids behind a scleral lens, rather suboptimal lens fitting is responsible.

Myopia control and scleral lenses dominated proceedings during the main conference among an array of topics. Interesting titbits included:

• In children prescribed higher low dose atropine for myopia control ~20% of those on 0.025% and ~30% on 0.05% had photophobia after two weeks, however these levels dropped below 10% after a year with adaptation (Yam et al ahead of print).
• On average, an emmetropic 4-8 year-old eye will grow 0.3mm ± 0.17mm per year and a 8-12 year old eye 0.12mm ± 0.12mm. Useful numbers when deciding if your young myopes are progressing more than normal. Also, children that end up myopic at age 10 have a higher rate of axial length change per year at age eight than those without myopia at age 10, 0.35mm vs 0.12mm. Perhaps we should be measuring axial length on all children, like we measure IOP to check for progression to glaucoma?
• Pauline Cho’s research group from Hong Kong released their one-year data from their three-year study looking at whether orthokeratology + 0.01% atropine is better than orthokeratology alone: After one year, the OK + atropine group showed 0.07mm growth vs 0.16mm with OK alone. However, the second six-month period showed identical growth, suggesting there may be some atropine adaptation. Full three-year results are eagerly anticipated!
• After analysing scleral shape in a range of eyes, ~60% were theoretically best fitted with a quadrant specific lens design, ~30% with a toric, and only 6% of eyes were best fitted with a spherical design, suggesting spherical scleral lenses should be the best design for only a handful of patients. To help with fitting quadrant specific lenses, it was noted that in eyes with peripheral ectasia, the steepest scleral area is generally adjacent to the apex.
• A lot of discussion centred around what to fill a scleral lens with to optimise physiology: a buffered preservative-free saline solution showed better comfort for patients due to the pH being closer to that of normal tears. Also new solutions now available with five key electrolytes (Neutrafill) may also decrease epithelial cell sloughing and midday fogging.

In summary, the GSLS congress was a feast of specialty lens knowledge and really highlighted how much interest there is in the field among researchers and clinicians. As a result, the new Global Myopia Symposium (GMS) was announced and will be kicking off in 2021 to complement and extend the education on offer at GSLS. No doubt I will be back and I encourage Kiwi optometrists with an interest in contact lens and myopia to put a trip to Vegas for GSLS on the bucket list: Just don’t expect to have a dull time!

As an aside, some the doyens present at GSLS including Prof James Wolffsohn, Dr Langis Michaud and Dr Maria Liu, are heading our way shortly as keynotes at the Orthokeratology Society of Oceania conference in the Gold Coast on 6 June 2020. These three were involved with the 2019 IMI Myopia White Papers: Don’t miss a chance to learn from these experts later this year!

Alex Petty is a New Zealand optometrist based at Bay Eye Care in Tauranga, with a particular interest and knowledge in specialty contact lenses, ortho-k and myopia control. He is a founding member of NZ Myopia Action Group.