Hybrid Contact Lenses Past, Present, and Future Victoria Butcko, O.D., FAAO Jesse Brown VAMC 820 S Damen Ave Chicago, IL 60612

History of Hybrid Lenses Hybrid lenses –Rigid gas permeable optic zone –Hydrogel peripheral zone –Have been available for 18 years –Their use in keratoconus was first described by Little in 1971.

SoftPerm (Wesley Jensen) Original design by Precision-Cosmet –Marketed as Saturn II lens Design fuses styrene-based RGP center with low water hydroxyethyl methacrylate (HEMA) soft-lens skirt –Ideal was to provide good comfort but have optic of RGP for best quality vision Performance limitations with Saturn lens –Redesigned and marketed as SoftPerm Lens Softperm offered larger OAD, larger central central optic zone and RGP pcs allowed wider range of applications

SoftPerm Lens Originally considered ideal s/p PKP, KCN, irregular corneas Larger OAD allowed better centration –Excellent stability and moderated astigmatism correction Negatives: –Limited oxygen transmission –Tendency to adhere –Lens breakage- major issue –Flexure of RGP

SoftPerm Resulted in: – corneal edema – neovascularization – epithelial erosion – acute red eye – infiltrative keratitis – graft rejection Limited wear time for patient

SoftPerm Table 1. The properties and parameters of the SofiPerm TM lens, as stated by the manufacturer. _________________________________________________________________________________________________ Properties Material Synergicon A (non-ionic) Oxygen permeability (at 35°C) 14.0 x 10 -n rigid optic zone* 5.5 × hydrogel peripheral zone* Water content 25% hydrogel peripheral zone ___________________________________________________________________________________ Parameters Back optic zone radii7.10 to 8.10 mm Back optic zone diameter7.00 mm Diameter of rigid optic zone8.00 mm Total diameter14.30 mm center thickness of the rigid center (3.00 D) 0.08 mm skirt thickness 0.20 mm. steepest BC6.5 mm *Units of oxygen permeability are (cm2/s) (mlO2/ml × mmHg).

Overcoming Limitations Quarter Lambda Technologies, Inc. of SanMarcos, CA – commenced a focused research and development program September 2001 to create an improved hybrid contact lens. October company received IRB approval to begin with four of the SynergEyes products.

Synergeyes Rigid Lens Component: Diameter: 8.4 mm OZD: 7.8 mm Oxygen permeability of 100 X 10 (-11) (cm2/sec) (mL O2/mL mm Hg). RGP center thickness is 0.15 mm for the 3.00 D back vertex power The soft skirt extends to 14.5 mm with a water content of 27% and a permeability of 9.3 X 10(-11) (cm2/sec) (mL O2/mL mm Hg). The mean thickness of the skirt is 0.16 mm.

Synergeyes Employs a continuous aspheric base curve from lens center to periphery Available with base curve radii as steep as 5.7 mm. Patent pending technology to produce a lens that is more than 10 times stronger at junction zone Multiple skirt radii are available for each base curve radius, 0.7 to 1.6 mm flatter than the central radius, in 0.3 mm steps.

TABLE 1. CL parameters for the Softperm and SynergEyes hybrid contact lenses: Lens SoftPerm SynergEyes Overall diameter (mm) Rigid overall diameter (mm) Rigid optic zone (mm) Soft skirt water (%) Soft skirt Dka Rigid Dka Power (D) Center thickness (-3.00 D) (mm) Mean skirt thickness (mm)

Synergeyes Rigid optics give optimal visual acuity Soft skirt material is dimensionally stable and expansion-free –Increased stability for consistent, predictable vision Hydrophilic, non-ionic soft skirt –Retains water content for all-day comfort; delivering a low-soiling lens

Synergeyes Rotationally symmetrical platform –Requires no orientational positioning in eyes having near equal refractive and corneal astigmatism High oxygen transmission –Excellent physiological response

Synergeyes Precise optics centered over visual axis –Ability to correct refractive errors ranging from D to D (with great reduction in glare, halo and starbursts) Exclusive HyperBond™ junction –Much stronger than other marketed hybrid lenses[1] Proprietary HydrolEyes™ surface science –Outstanding in vivo wetting provides excellent all-day comfort and optical clarity

Fitting Synergeyes Lenses Synergeyes A –20 lenses 10 BC, 2 SC each Synergeyes KC –24 lenses 8 BC, 3 Skirt Curves each

Fitting Synergeyes Lenses Synergeyes A and KC –Diagnostic fitting Initial selection should be 1.00D to 1.50D steeper than flat K Each 0.1mm of BC change requires 0.50D power adjustment –SAM and FAP Goal is to fit the steepest BC that is free of central bubble Focus on BC selection before fine tuning skirt curve

Synergeyes A and KC Can not use regular Sodium Fluorescein due to the soft lens skirt –Large Molecule Fluorescein used to evaluate fit –Fluorescein is placed in bowl of lens prior to inserted lens –Interpretation can be difficult not as effective as regular fluorescein

Synergeyes A and KC Goal is to achieve apical clearance –Pooling of fluorescein will be noted centrally in the lens Lens movement –Should be slight lag in up gaze –No scleral impingement –Free of “edge fluting” –Free to move with “push up” test –Lenses need to settle minutes to properly assess movement Lenses will tighten over time

Synergeyes A and KC Skirt Curve Radius –If “Heavy bearing or a heavy ring of touch” is noted at the junction of the skirt curve and the RGP: Plan: steepen the SCR Example: change SCR from 8.5mm to 8.2mm –If edge fluting is noted also steepen SCR –Steeper skirts will reduce the bearing at the corneal apex

Figure 1: Pt in down gaze with superior pooling. Figure 2: Central pooling noted with light touch midperipheral zone.

Two additional examples using high molecular weight fluorescein with Synergeyes A fit.

Synergeyes A/KC Fitting Fitting is Counter-intuitive –Tight fitting lenses- steepen BC or SCR –“Heavy Bearing” at junction- steepen SCR Never prescribe flatter than or “on” Flat K Lenses are 6 month replacement

Synergeyes Also available from Synergeyes –Synergeyes Multifocal –Synergeyes PS (post surgical) Syn A marketed for normal astigmats, myopes and hyperopes Syn KC marketed for KCN, PMD, more corneal irregularity

Care and Cleaning of Synergeyes Lenses Digital rubbing is extremely important! Multipurpose solutions: –Opti-free –Renu Multipurpose –Clear Care Solution 6 month replacement schedule

Over refraction After achieving proper fit, proceed to over refraction –Begin with spherical over refraction –If necessary incorporate cylindrical over refraction –If over refraction >2.00D cyl, pt may be experiencing lens flexure Perform over Ks to see if they correlate Can order enhanced profile design, increased central thickness to prevent flexure.

References Bennett, Edward S., Vinita, Henry; Clinical Manual of Contact Lenses Philidelphia: Lippincott Williams & Wilkins, 2000; Rubinstein, MP, Sud, S; "The use of hybrid lenses in the management of the irregular cornea." Contact Lens Anterior Eye; 1999; 22(3);