Download Hyper-Oxygen Permeable Rigid Contact Lenses As An Alternative

Hyper-Oxygen Permeable Rigid Contact Lenses As An Alternative For The
Treatment Of Pediatric Aphakia
BACKGROUND:
1) Why choose hard over soft contact lenses to treat babies?
Rigid gas permeable (RGP) contact lenses offer the following
advantages over soft….
•High oxygen transmissibility
•Optically superior to hydrogel
and/or silicone lenses
-especially higher powers/thicknesses
-ability to correct unwanted cylinder
•Flexibilty in design (customize curve, power, diameter)
•Cost – significantly less expensive
•Ease of handling (insertion and removal)
•Safety profile- low bacterial and protein adherence
2) Why not use the SILSOFT lens, the industry standard for treatment of pediatric
aphakia?
•Silsoft
(Bausch & Lomb): Estafilcon A (100% silicone polymer)
•Dk: (O2 permeability) 340 (cm2 / sec) x (ml O2 / ml x mmHg) x 10-11
•It is the current market leader, specifically FDA approved for use in aphakia and
pediatric aphakia
Disadvantages…
•Very limited parameters
23-32 in 3 D steps and nothing beyond 32
Base curves: 7.5, 7.7, 7.9 ONLY
Diameter: 11.3 ONLY
•Cost: $$$
•Fit: stability on the eye
•Optical quality at higher powers is questionable
•Risk of complications (no greater of less than an RGP)
•Oxygen delivery (likely high based on Dk, but transmissibility data at high/ aphakic
powers not currently available)
3) Our preference is the MENICON Z gas permeable lens from Menicon, Japan.
Why?
•Material:
Tisilfocon A- a copolymer of siloxanylstyrene and
fluoromethacrylate
•Dk: 163x10-11 (ISO) or 189x10-11 (Fatt) or 250x10-11(Hamano)
•Refractive index: 1.44
•Light Transmittance: >90% @ 380-780 nm for 0.10mm t
•H2O Absorption: <0.50% by weight (25o C)
•Manufacturer: Menicon Co. Ltd., Nagoya, Japan
•FDA approval: for 30 days of continuous wear in adults
(July 2002)
compare to current silicone hydrogels:
Focus N & D
Acuvue Oasys
Purevision
O2 Optix
140
147
110
110
Preferred lens design for fitting aphakic babies:
•Dyna Z Intralimbal design (Lens Dynamics, Golden CO)
•Spherical single cut central optic zone
•Multicurve periphery (4-5 blended spherical curves)
•Large diameter lens (11.2mm standard) with any variation
of
base curve, power, diameter, edge and optic zone
4) Fitting Procedure
Tools you will need:
• Pediatric Fitting Set (can be obtained from Lens Dynamics, CO)
• Blue LED
• High molecular weight Fluorescein (ex: Fluosoft vials)
• Loose trial lenses (for over-refraction)
TECHNIQUE
Methods of wrapping/holding a baby prior to insertion/removal of lens will be reviewed
1) Initial diagnostic lens:
•
on a new born (first several days/weeks of life), have found that 7.00/+19.50/10.4/8.6 is
a good starting point, then work from there.
• can go the the operating room during/after surgery, but really not necessary. Get more
valuable information from a wake baby (ex: level of resistance to insertion, lid strength,
movement of lens with blink and rub, etc.)
• Apply fluorescein prior to lens insertion
• View fit with blue LED
GOAL: Want to achieve a fit that is a little on the steep side with an adequate edge
profile and movement for good tear exchange –(will show images of what this looks like)
Over-refraction
Birth to 2 years of age:
not walking? overcorrect by 2-3 D
walking? overcorrect by 1-1.50 D
2 years of age and beyond:
full distance Rx with pl/+3.00 bifocal OU
Cases: Sample calculation for different cases will be provided at this point (i.e. how to
get from diagnostic lens to final lens power)
2) Insertion and Removal Training:
-specific technique: will be demonstrated by diagrams and/or video clip
3) Wear schedule:
-first 1-2 weeks: daily wear only
-after that, can be used safely on a 1 week extended wear basis
-cleaning products/procedures to be reviewed briefly
Follow Up Visits
•1 week, 1 month, 3 months ( and then every 3-4 months)
• Over-refraction, on-eye evaluation of fit, examination of cornea/limbus, examination of
lens integrity
CONCLUSIONS:
Based on our experience, this lens is easy to fit, easy for families to handle/care, and is
not damaging to the cornea/eye when used on a 1 week extended wear basis. Children
appear to be very comfortable in the lens
It is now our #1 choice for pediatric aphakia
Reading Material:
•Shaughnessy MP, Ellis FJ, Jeffery AR, et al. Rigid gas-permeable contact lenses are a safe and effective
means of treating refractive abnormalities in the pediatric population. The CLAO Journal. 2001;27:195201.
•Gleason W, Tanaka H, Albright RA, et al. A 1-year prospective clinical trial of Menicon Z (tisilfocon A)
rigid gas-permeable contact lenses worn on a 30-day continuous wear schedule. Eye & Contact Lens. 2003;
29:2-9.
•Amos CF, Lambert SR, Ward MA. Rigid gas permeable contact lens correction of aphakia following
congenital cataract removal during infancy. Journal of Pediatric Ophthalmology & Strabismus. 1992;
29:243-245.
•Saltarelli DP. Hyper Oxygen-Permeable Rigid Contact Lenses as an Alternative for the Treatment of
Pediatric Aphakia. 2008; 34(2):84-93.