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Presentation on theme: "What Solution is to"— Presentation transcript:
Slide1
What Solution is to Be Used for Scleral Lenses?
Ralph P Stone and William J Benjamin
Slide2
Disclosure
Consultant to Alcon Laboratories,
NovaBay
Pharmaceuticals
Stock in Merck
Proprietary interest in SMM Ventures, LLC
Have proprietary interest in Scleral solution discussed in this talk
Slide3
Scleral Lenses—A Different World
Often used on the “difficult” that can be diseased or compromised corneas
Uses lens materials originally used for small rigid lenses with lots of movement on the eye to allow tear exchange
Lens designed to trap a lot of “stuff” under the lens
Exchanges tears at best less than a soft lens and often after hours of wear
And we use solutions designed for inhalation therapy to fill the void under the lens.
Slide4
Improving wear of Scleral lenses
We have improved the materials with high
Dk
rigid materials.
We have improved the lens designed with options to diameter, options in designs of the scleral landing zones.
But we have done little to improve the solution used with the lenses.
Slide5
Improving wear of Scleral lenses
We have improved the materials with high
Dk
rigid materials.
We have improved the lens designed with options to diameter, options in designs of the scleral landing zones.
But we have done
little
nothing to improve the solution used with the lenses.
Slide6
What are the solution issues?
The post lens tear film!
A rigid lens has a POLTF thickness of approximately 30um
1
A soft
c
ontact lens has POLTF of an average of 2.34 um.
1
The scleral
lens has
a
POLTF thickness
often exceeding 250um
The liquid under the lens can have a significant effect the corneal environment.
JJ Nichols, PE
Kingsmith
. Thickness of the pre- and post—contact lens tear film measured in vivo by interferometry. IOVS 2003; 44(1):68-77
Slide7
What do we see?
Evidence of hypoxia even with high Dk materials1The Scleral lens should “semiseal” to the eye without movement to hold a fluid reservoir2The fogging/clouding3, reservoir debris2, tear debris under the lensVisser 4 found the that 48.7% of patients with scleral lenses (>18mm) needed to remove and refill the reservoir at least once during wear. Caroline and Andre2 estmated that 1 in 5 patients some evidence of clouding (or haze).
1. Michaud et al. CLAE 2012; 35(6):266-71 2. W
DeNaeyer
, CL Spectrum June 2010 3. P Caroline, M Andre CL Spectrum June 2012; 27: 56. 4.E-S
Visser
et al Modern Contact Lenses parts I and II, ECL 2007; 33(1): 13-20 and 21-25.
Slide8
Building a hypothesis for improvement
Laboratory analysis of the reservoir clouding by Walker and co-workers found evidence of mucin, lipids (meibom) and proteins1.Work by Bachman and Wilson indicate that the composition of the bathing solution has a significant effect on the sloughing of corneal epithelial cells as measured by specular microscopy.2The balance of Na, K, Ca Mg have effects on corneal sloughing.
1. M Walker et al, Laboratory analysis of Scleral lens Tear Reservoir Clouding, GSCLS Poster 2014. 2. WG Bachman and G Wilson, Essential ions for management of the Corneal epithelial Surface, IOVS 1985; 26:1484-88
Slide9
Hypothesis
Using saline based on NaCl alone may increase the loss of corneal cells.Therefore the use of inhalation saline may not provide a desirable environment under a scleral lensNot much is known about the effect of pH and maintaining pH at known tear levels with buffers is desirableOsmolarity may also be important. Although there are few reports of corneal edema, but these have been primarily attributed to the thickness of the lens and tear reservoir.1 But we also see lens settling reducing the tear vault by as much as 70um. Is It all settling? Could it contain a component of edema from fluid absorption of the insertion solution.
1. L. Michaud et al. CLAE 2012; 35(6): 266-71
Slide10
The Test
Four formulations
All balanced to tear concentrations of sodium, potassium, calcium and magnesium
All phosphate buffered at 7.4
Two with added wetting agent
Varying in
osmolarity
301
mosm
320
mosm
330
mosm
346
mosm
Slide11
The Human Experience
A single patient with
keratoconus
who reported to have significant hazing requiring as many a
3-4
removals per day
and reinsertions using inhalation saline
. Increased in frequency as the day progressed.
Used each solution for 3 days.
Reported hazing, overall comfort over the course of the day
Slide12
Results
Patient reported no more than one reinsertion per day for hazing only after 7-9 hours of wear.
Lenses were reported comfortable throughout the day.
Lens wearing time was within or better than the usual schedule for the individual
No significant difference in any parameter related to
osmolarity
Slide13
What’s Next
Larger 1 month clinical with variety of patients using 2 formulations
Both balance with essential ions and phosphate buffered
pH= 7.4
Osmolality at 315-320
mosm
Different in the addition of a wetting agent
Slide14
Conclusion
The literature and anecdotal results indicate we are using the wrong solution for inserting scleral lenses.
The right solution may make scleral lenses a choice for a variety of patients including
