Special offer: Get a FREE 13 lens trial set with a purchase of a warranted 4 lens bank. Call us today @ (800) 228-2691
Parameters:
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Range
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Base Curve (mm):
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5.50 to 8.50 (in .05 steps)
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Power (Diopters):
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+10.00 to -20.00 |
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Diameter (mm):
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13.5, 14.0, 14.5, 15.0, 15.5, 16.0
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Edge Lift Profile (in 1 Steps):
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- Increased and decreased as needed in steps
- Quad Sym™ edge treatment available
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Scleral Fitting, One, Two, Three
ONE: Select the base curve first.
TWO: Select a proper Base Optic Zone
THREE: Select a proper edge profile.
Base Curve Selection:
Unless the practitioner has an OCT machine, scleral fitting is a trial fitting proposition. Start with the average of the central K readings and progress flatter or steeper until a good base curve to cornea relationship is achieved. A proper scleral lens will completely vault the cornea with the landing zone on the sclera.
A tear layer of 300 microns is the goal at fitting time. These lenses generally “settle” by 100 microns during the break in period, resulting in about a 200 micron, consistent tear layer. It is hard to judge 300 microns with a straight on view of the fluorescein. It is good to do the straight on view, but only for a gross overview as to touch points or pooling. Once you think the base curve is about correct, do an Optical Section view with WHITE light. This will show you the corneal thickness and the tear layer thickness. An average cornea is about 600 microns thick so the tear layer should be about half as thick as the cornea.
Notice the tear layer is thinner superiorly and thicker inferiorly. Most fits will look this way and that is acceptable.
Here the tear layer is thicker than the cornea, select a flatter base curve.
Here the tear layer is way too thin compared to the corneal thickness and there is superior corneal touch which is unacceptable. Select a steeper base curve.
TWO: BASE OPTICAL ZONE SELECTION:
The Dyna Semi-Scleral design comes 13.5 to 15.0 with a 9.0 BOZ and 15.5 to 19.0 with a standard 9.4 BOZ. The large diameter lenses many times need larger BOZs from 9.8 to 11.0 mm. A larger BOZ is indicated if there is touch toward the limbal area and to increase the sagital depth.
Example One: A 7.00 BC with 15.5 diameter and 9.4 BOZ has a sagittal depth of 4.484. To achieve the same sagittal depth, if the BOZ is made larger at 9.8, the BC needs to be flattened to a 7.12 mm.
Example Two: A 5.30, -9.00, 15.0 / 9.0 lens is trial fitted. The center tear layer is showing 300 microns but there is touch at 3 and 9 o’clock with some lateral de-centration. A larger diameter will help with centration but a 5.30 BC is too steep for a 17.0 diameter lens. Since the 5.30 with a 15.0 diameter yields a 5.719 sagital depth, in a 17.0 diameter with 11.0 BOZ yields 5.722. This lens can be made, will yield the 300 microns like the steeper 15.0 and lift the lens at the 3 and 9 touch points.
THREE: EDGE LIFT SELECTION:
The edge(landing area) needs to align the sclera. No seal off or excess edge lift. A compression ring means a steep edge. Blanching or blood vessel break down indicates a tight edge lift.
Note how the blood vessel stops at the edge of the lens.
See the blood vessels run right under the edge of the lens. Good edge lift.
DESIGN OPTIONS:
1. Quad Sym Edge treatment. Flatter or steeper edges in any one of 4 quadrants.
2. Front Toric Option.
3. Multifocal front option.
Fitting Guide:
Starting Point:
Start with a trial lens that is the average of the K readings or Sym Ks.
Insertions:
It is important that no air bubbles get under the lens. To insure this does not happen, follow the outlined procedures:
1. Clean the lens before insertion with an approved GP solution, and final rinse with a non-preserved sterile saline.
2. Place the lens between your index finger and the forefinger, concave side up.
3. Completely fill the lens with sterile saline.
4. Dip a fluorescein strip into the saline in the lens bowl.
5. Position the patient so their face is parallel with the dispensing table or the floor.
6. Place the lens on the eye so that the saline is still in the bowl of the lens. A towel placed on the table to absorb the displaced saline.
7. The trial lens should equilibrate about 20 minutes before evaluation.
Evaluation:
1. The lens should position centrally.
2. The lens should have minimal movement, about 0.5 mm.
3. The lens should have no conjunctival drag.
4. Look for adequate edge lift. Increase or decrease the edge lift as required.
5. The lens should vault the cornea for maximum comfort. Through the fluorescein, you should be able to barely see the outline of the pupil. If the pupil is very distinct the fit is too flat. If you can not see the pupil, the fit is too steep.
Removal:
Re-hydrate the eye. Place a DMV remover on the lower, nasal side of the lens. Rock the lens to insure any seal is broken and remove the lens.
Other Design Options:
Multifocal Option: Front aspheric optics can be added for presbyopic correction. The base curve is not affected.
Toric Options: Front toric designs are available.
Fitting Tips:
1) Select a base curve close to the average of the central K readings. Scleral lenses should vault the entire cornea to maximize comfort and corneal health.
2) Always fit from the center first, and then assess the mid-peripheral area and finally the edge. Scleral lenses will have more pooling than corneal designs. A good guide for fluorescein assessment is looking for the outline of the pupil through the fluorescein. The fitter should be able to barely see the outline of the pupil. If the pupil is very prominent, the base curve is too flat. If the fitter cannot see the pupil, the base curve is too steep. Next, look at the BOZ/secondary curve area. The limbus should be vaulted and no touch should be observed on the cornea. The standard BOZ is 9.0 mm, but that can be adjusted larger or smaller as needed. Finally, check the PC area. There MUST be fluorescein under the edge to allow for tear exchange. Check for conjunctival drag. To correct any stand off, decrease the edge lift. To correct seal off, increase the edge lift.
3) Diameter selection should be determined by the limbus to limbus measurement plus enough lens to “land” on the sclera. Typically, the diameter should be about 1.5 mm larger than the cornea. Diameters of 13.5 to 16.0 mm should accomplish this, while avoiding the insertion and removal difficulties of larger diameter designs. Soft lens comfort comes from vaulting the cornea and putting the bearing on the sclera.
4) Correct insertion is important to successful fits. The bowl of the lens MUST be filled with sterile, non-preserved saline. Artificial bubbles will result if too little saline is in the bowl. Have the patient position their face parallel to the fitting table to insert the lens. The fitter should instill fluorescein into the saline prior to insertion during fitting sessions. There are two devices that make insertion easier. The softsert™ device and a DMV® that has a hole through the device to release pressure once the lens is on the eye.
5) Some patients can remove the scleral lenses with traditional GP removal techniques. Others will need a standard DMV device for removal. Instill saline or rewetting drops first and then place the DMV 4-5 mm below the center of the lens. Rock the lens slightly to insure the lens is not sealed off, then lift the lens off.
6) Schedule follow-up visits as late as possible in the day. This gives the fitter a “real world” assessment of the tear pattern.
7) Any questions or fitting concerns should be addressed to our consultants at 800-228-2691.
Fitting videos and exampls:
Videos:
Insertion video
Removal video
Fitting Examples:
1st trial video
2nd trial video
3rd trial video
4th trial video
5th trial video
6th trial video
7th trial video
8th trial video
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