A Hybrid For The Hard-to-Please
contact lens management
A Hybrid For The Hard-to-Please
Hybrid multifocal daily-wear offers comfort and simultaneous vision.
JUSTIN C. HOLT, O.D. & DANE F. DANSIE, O.D., OGDEN, UTAH
When presbyopic patients present with an interest in contact lens wear or when current contact lens wearers reach presbyopic age, they can be some of the most challenging patients to satisfy. With the introduction of the SynergEyes Multifocal, from SynergEyes, Inc., we have found these patients are happy with the vision and comfort their lenses provide. This is because this daily-wear lens combines the oxygen-permeable hard center of a gas permeable (GP) lens with a soft-hydrogel skirt and doesn't decenter or move upon blink. It also contains no aspheric surface optics to diffuse the transition from the distance correction to the magnification at near — something some patients have reported causes images to appear "a little hazy" or with a shadow.
Here, we discuss the features of the SynergEyes Multifocal and provide pearls for fitting this lens.
The SynergEyes Multifocal is a hybrid contact lens that provides simultaneous vision, as opposed to progressive or mini-monovision, for patients who have up to 2.00D of corneal cylinder. We've, however, been able to fit patients with over 4.00D of corneal cylinder with the SynergEyes A lens, the platform around which the SynergEyes Multifocal was built. The SynergEyes Multifocal contains two distinct focal ranges, meaning there is no blending, diffusing or graduating of the transition between the distance- and near segments. Also, the lens is fabricated with lathing and laser interferometry to ensure the quality of both optic zones as well as the transition between the two.
|During the fitting process, it's crucial to educate the patient on the difference between simultaneous vision and true accommodation.|
► a Dk value of 100 in the GP center portion of the lens
► a GP center, precluding corneal cylinder in most patients
► the incorporation of a center near segment in either 1.9mm- or 2.2mm diameters
► an overall diameter of 14.5mm
► base curves of 7.1mm to 8.0mm in 0.10mm steps
► add powers of 1.25D, 1.75D and 2.25D
► sphere power ranges from 2.00D to -6.00D in 0.25D steps.
The base curve of the initial diagnostic lens is typically 1.50D (0.3mm) steeper than the flattest keratometry (K) reading. Current SynergEyes outcomes data indicates you should use the steeper of the two skirts to ensure a soft landing at the junction area and the cornea.
SynergEyes provides a lens calculator to determine the initial lens(es), based on the patient's manifest refraction, keratometry readings (or SIM Ks), the patient's age and preferred distance (or dominant) eye.
If you prefer the diagnostic fitting process, the SynergEyes Multifocal is based on the same design platform as the SynergEyes A lens. You can then use the SynergEyes A diagnostic set in the following manner:
Once you've established the initial fit, determine the correct power. Perform a spherical over-refraction to maximize the magnification of the bifocal segment. This is important, as even a small amount of excess minus power could affect the patient's near vision.
To show a true representation of how the patient will see and feel in these lenses, we've found success in using a soft, disposable contact lens placed directly over the SynergEyes diagnostic lens itself, as the soft lens corrects for the over-refraction. SynergEyes suggests you use a trial lens frame with the over-refraction for the same purpose.
Now, hold a pair of 1.25D loose-trial lenses over the patient's eyes, with the soft lens or trial lens frame still in place, and ask him to hold a magazine at his normal reading distance. Increase the power of the loose lens to 1.75D if necessary. If the patient says he's still unable to read, try increasing the power of the loose lens to 2.25D, although this will likely be more magnification than most patients will require. Typically, patients retain the best distance vision when the lens for the dominant eye uses the smaller 1.9mm reading segment. The larger 2.2mm segment in the non-dominant eye tends to provide the greatest near acuity.
When trouble-shooting patients who report acceptable vision at either distance or near, dissimilar add powers are often all you need to provide adequate vision at both distance and near. For instance, to eliminate blur from a distance eye; first ensure the accuracy of the distance refraction. If that is accurate, it's possible the 2.2mm segment is excessively encroaching on the distance field, so you may need to decrease the segment diameter to 1.9mm in the non-dominant eye. This may be particularly true in patients who have rather small pupils. These patients may find it hard to suppress the larger 2.2mm center if it covers most of the pupil. If you decrease the segment diameter, the non-dominant eye is then able to more easily suppress the near segment and provide improved distance vision.
Conversely, if a patient reports not seeing well at near at his "preferred reading distance," make sure he hasn't been over-corrected, and adjust the add power accordingly. If the patient can see at near but has persistent complaints of "ghosting" or a "3-D effect," then increase the segment diameter to 2.2mm in the dominant eye in order to capture a larger reading field. This may be particularly true in patients with larger pupils who may find it hard to utilize the near segment if it is very small relative to the pupil diameter. If the segment diameter is increased, the dominant eye is then able to more easily utilize the near segment and provide improved near vision.
|CENTER MATERIAL: Paflufocon D|
SKIRT MATERIAL: Hemiberfilcon A
WEARING SCHEDULE: Daily-wear
WATER CONTENT: 27 % (soft skirt)
Dk VALUE: 100
BASE CURVES: 7.1mm to 8.0mm in 0.10mm steps
OVERALL DIAMETER: 14.5mm
ADD SEGMENT DIAMETER: 1.9mm and 2.2mm
SPHERE POWER: 2.00D to -6.00D in 0.25D steps
ADD POWER: 1.25D, 1.75D and 2.25D
MODALITY: Six-month replacement scheduley
COST: $150 for the only supplied two-pack ($75/lens).
During the fitting process, it's crucial to educate the patient on the difference between simultaneous vision and true accommodation. This is so he can understand why he will experience a neuroadaptive period with the SynergEyes Multifocal. It should also help him understand why he shouldn't use his reading glasses with the SynergEyes lens, despite the fact that he may not initially see as well at near as he'd like. Keep in mind that the eye is now focusing very differently than it has in the past. At all times both distance- and near vision are being focused on to the retina. The brain now has to determine which areas of the retina it will suppress and which areas it won't, depending on the task at hand, whether at near or far. If the patient relies on readers, he can delay this neuroadaptation. Some patients will make this transition very quickly — in a matter of hours or days — while others can take up to three months.
With the introduction of the SynergEyes Multifocal, I've found that patients now have the option of a multifocal lens without having to compromise clarity. OM
DR. HOLT PRACTICES FULL SCOPE OPTOMETRY IN NORTHERN UTAH. HE IS IN GROUP PRACTICE AT THE MOUNT OGDEN EYE CENTER AND BOUNTIFUL HILLS EYE CENTER. E-MAIL HIM AT JCHOD5150@YAHOO.COM.
DR. DANSIE PRACTICES AT THE MOUNT OGDEN EYE CENTER. HE IS ALSO ON STAFF AT THE SALT LAKE VETERANS HOSPITAL AND IS CLINICAL-ADJUNCT FACULTY FOR SEVERAL OPTOMETRY SCHOOLS. E-MAIL HIM ATDANSIE@MOUNTOGDENEYE.COM.
Optometric Management, Issue: October 2007