Optical supplies, Danker Lenses

SynergEyes contact lenses are a hybrid lens design. The centre of the lens is made from a highly permeable RGP material, while a soft lens 'skirt' is bonded to the edge of the RGP portion. So while the RGP portion delivers crisp, clear and stable vision, the soft 'skirt' aids comfort, centration and overall wearability.

ClearKone is optimised to vault irregularities of the keratoconic cornea. Its vault design utilises a reverse geometry landing system, which enables the majority of power to come from the tear lens, thus substantially lowering lens power and further improving optical performance. The linear vault system makes fitting your keratoconic patients easier as you no longer need to decide whether the amount of corneal contact is acceptable.

ClearKone For Keratoconus

Aim and Ideal Fit

• The fitting philosophy of the ClearKone lens is based on the concept of fitting overall sagittal depth instead of varying the base curve.
• The fit of the lens depends upon clearing the elevation of the cone, rather than matching it in curvature.
• The lens has a linear vaulting system ranging from 100 to 600µ of vault in 50µ steps.
• The lens lands on the cornea at both the soft portion, defined as Outer Landing Zone (OLZ), and rigid portion, defined as Inner Landing Zone (ILZ). The landing area is divided by the junction of the hybrid lens.
• The ideal fit (Fig. 1) will have:
  • Complete apical clearance and no touch on the cone
  • Slight thinning of the fluorescein pattern over the cone
  • Thinning of the fluorescein pattern at the ILZ
  • Bearing at the OLZ
  • Movement on Push Up Test

Terminology

• Vault - The overall relative depth of the lens.
• Outer Landing Zone (OLZ) - Portion of the Soft lens material that lands on cornea (Fig. 2).
• Inner Landing Zone (ILZ) - Portion of the RGP lens material that lands on the cornea (Fig. 2).
• NaFL Thinning -A decrease of thickness of the tear layer will cause a decrease in fluorescence, resulting in an area of NaFL having a darker appearance than the area around it (not black as with bearing). There is still complete clearance.
• Bearing - a black appearance as a result of contact with the cornea with the posterior of the lens, eliminating the presence of NaFL and the possibility of any fluorescence.
• Pooling - complete uniform appearance of the NaFL (no variation in brightness).

Trial Lens Selection and Fitting

• Vault selection:
  • Begin with 250µ Vault value in Medium skirt curve
  • Insert the lens filled to the top with saline and a drop of high molecular weight fluorescein such as Fluoresoft
  • Use the No7 blue torch to immediately check for central bearing (Fig.3),central pooling (Fig. 4), or for bubbles. Bubbles affect the appearance of NaFL pattern and are ALWAYS representative of an insertion error, not a fitting error hence the lens must be reinserted
  • If central bearing is seen then the lens has too low a vault and can be removed immediately, increase the vault in 100µ increments, until apical clearance is achieved
  • If central pooling is seen then allow the lens to settle for 3 to 5 minutes and assess the fit using a slit lamp with the blue beam and Wrattan filter
  • If pooling is seen, decrease the vault in 100µ increments until the first bearing lens is found
  • The Ideal fit is approximately 100µ over first bearing. This may show slight thinning of the NaFL over the cone but no touch. Even the lightest or 'feather touch' will cause patient discomfort after a few minutes of wear
  • When first bearing is observed increase the vault by 100µ and re-evaluate the corneal clearance for apical clearance with slight thinning over the cone

Figure 3: Central Bearing

Figure 4: Central Pooling
• Skirt Selection:
  • Evaluate skirt only after proper vault has been determined and the lens is on the eye
  • Always start with the medium skirt curve
  • The lens will exhibit movement very similar to a soft lens
  • The ideal fit will show NaFl thinning at the ILZ and bearing in the OLZ (Fig. 5)
  • Evaluate landing area at 3 and 9 o'clock positions with the slit beam perpendicular to the area being observed. This is very important as an incorrectly positioned beam may give a false impression of bearing

Figure 5: OLZ and ILZ
• Skirt curve too flat:
  • If bearing is observed under the ILZ and thinning observed under the OLZ (Fig. 6) the skirt curve is too flat. Change to the Steep skirt curve
  • If equal bearing is observed under both the ILZ and OLZ (Fig. 7) the skirt curve is too flat. Change to the steep skirt curve
  • If pooling is observed under the OLZ, and bearing is observed under the ILZ the skirt curve is too flat. Change to the steep skirt
  
  Figure 6: Bearing and Thinning
  
  Figure 7: Equal Bearing
• Skirt curve too steep:
  • If pooling is observed under the ILZ (Fig. 8) the skirt curve is too steep. Change to the medium skirt
  • The patient will notice improved comfort when the correct skirt is chosen.
  • If pooling is observed under the OLZ, and bearing is observed under the ILZ the skirt curve is too flat. Change to the steep skirt
  
  Figure 8: ILZ Pooling
• Determine Final Lens Power:
  • Once the ideal fit lens is in place over-refract to determine the final lens power
  • If the over-refraction is greater than 4.00D adjust for vertex distance
  • Lenses in the fitting set vary in power from -1.00D to -14.50D sphere power depending on the vault depth (table 1). As the lens has a linear vault system and the power of the lens is adjusted accordingly the over-refraction found for any vault should be the same

Trial set lens parameters

Vault (µ)	RX (D)
100	-1.00
150	-2.00
200	-3.00
250	-4.50
300	-5.50
350	-7.00
400	-8.00
450	-10.00
500	-11.00
550	-13.00
600	-14.50

Fitting Tips

• NaFL evaluation must be performed within 3-5 minutes after insertion as tear flow will thin the NaFL and give a false appearance.
• For patients being refitted from RGPs or another Synergeyes lens you should expect some topographical changes with the cone becoming its 'natural shape':
  • Therefore order a lens 50µ deeper than the best fit trial lens
  • If the patient reports discomfort or reduced wearing time after wearing the lenses for a week or two then recheck for central bearing
  • If a vault change is needed at follow up the lens power will need to be adjusted

Fitting Challenges

• You will find it difficult to achieve a good fit:
  • If ectasia extends beyond the landing zone
  • If there is an irregular landing pattern. You will be unable to achieve an even distribution at the landing zone. This is often seen in advanced PMD patients
  • On post graft patients - fitting success can be possible but the landing zone may fall on graft-host interface. This is not an acceptable fit

Handling SynergEyes Lenses

Insertion

• Place the lens onto the end of your index finger or balanced between your index and middle finger and place a drop of FluoreSoft® high molecular weight fluorescein into the bowl of the lens. Fill the lens to the brim with saline (Fig. 9). You may prefer to use a large suction holder for this.
• Ask the patient to lean forward and tilt their head down so their nose is pointing to the floor.
• Ask the patient to pull their lower lid down while you retract their top lid then pop the lens directly onto the cornea, coming up from underneath.
• Try to preserve as much saline as possible under the lens so you don't trap an air bubble under the lens.
• Allow the lens to settle for ~30 seconds before assessing the fluorescein fit.
• If there is a bubble under the lens that is larger than 2mm, you will need to remove it and start again.

Figure 9: Prior To Insertion

Figure 10: Removal

Removal

• Wash your hands with moisturiser-free soap and dry hands well.
• Ask the patient to look up. Give your fingertips a final wipe on a tissue so they are 100% dry, and place your thumb and index finger together, so the only movement they can make is a small pinching movement.
• Pinch the lens at the soft skirt at 6 o'clock- only a very small pinching motion is needed to pucker the bottom of the lens - release the tension and allow the lens to come off (Fig 10).
• If the lens doesn't come with the 1st pinch, dry your fingers and try again.

Sterilisation and Re-Use of SynergEyes Diagnostic Lenses

There are currently no official guidelines regarding the sterilisation and re-use of specialist soft diagnostic contact lenses. These are due to be drawn up by The College of Optometrists in Spring 2010. However, in the meantime, they have advised the following protocol:

• After use, rub the lens with Crystal Cleaner lens cleaner (Miraflow equivalent), then rinse well with saline
• Sterilise the lens with a peroxide-based cleaning system, such as Eyeye Monosept (available from No7)
• Store the lens in its glass vial in soft lens multipurpose storage solution, until next use
• Rinse the lens with saline or soft lens solution before applying it to the next patient's eye

After 12 months the lens should be discarded and replaced. It is not advised to autoclave soft lenses as this would bind any prion protein to the lens and potentially make it more infective.

Patient Guidelines for SynergEyes Cleaning and Maintenance

• If a patient finds their lenses tend to become greasy after wear, digital rubbing with an alcohol-based cleaner such as Crystal Cleaner will help.
• The patient will need to fill the lens with saline prior to insertion, and it is important that non-preserved saline is used for this purpose. This prevents the chance of a toxic reaction to preserved solutions, which can develop after continued use.
• Standard contact lens rewetting drops can be used in cases where symptoms of dryness occur (at the discretion of the practitioner).

Fitting Sets

Design	No. Lenses	Parameters	Cleaning/ Sterilisation Protocol
CK	22	100 - 600 in 50 Steps / TD 14.50	Disinfect using a peroxide system and store in multipurpose solution

Parameters

Design	ClearKone
Material	Paflufocon D centre (hemiberfilcon A skirt)
Water Content	27% soft skirt
Base Curve / Vault	100µ to 600µ in 50µ steps
Diameter	14.5mm
Skirt Curvature	Steep, Medium, Flat
Sphere Power	+2.00 to -8.00 in 0.25D steps, -8.50 to -15.00 in 0.50D steps, +2.50 to +5.00 in 0.50D steps
DK	100
Wear	Daily wear
Replacement	6 Months