GP Multifocal Correction
With Dr. Rob Davis and Dr. Doug Benoit
Links to Case Studies:
Case 1
By: Dr. Rob Davis
DP is a 46 year old male who is vice president of land development for a local bank. His visual requirements include computer/blackberry, reading legal documents and distance. In his free time DP manages a traveling baseball team that his son is a member. He has no allergies and is taking lexapro for anxiety. Family history is remarkable for diabetes. Past contact lens history includes soft toric lenses and RGP bifocals. The soft lenses seemed to come in and out of focus with the blink. The Menicon bifocal was not comfortable and a couple of times during the day grit would find its way underneath the contact lens. DP explained the experience as if a knife was poking him in the eye. DP has been wearing a variety of contact lenses for approximately 35 years.
The SynergEyes lens is one option that offers the comfort similar to soft lenses and the vision similar to the gas permeable lenses. In order to properly fit the SynergEyes bifocal lens design keratometric values, manifest refraction, pupil size and horizontal visible iris diameter are parameters that are necessary to obtain. The keratometic value gives the initial base curve starting point. The manifest refraction verifies if the lens prescription is appropriate. The pupil size provides information as to starting point for the bifocal size. The SynergEyes bifocal is a near centered annular lens design manufactured in a stock 1.9 and 2.2 near zone size. Horizontal visible diameter informs the practitioner as to the sagittal height of the eye. Knowing this information can modify the base curve selection to improve the fit of the lens. Smaller eyes are fit flatter than an average 11.8mm horizontal visible iris diameter. Larger eyes are fit steeper than average 11.8 mm corneal diameter. The SynergEyes material requires ten minutes to settle on the eye because of the tightening characteristics intrinsic to the lens material. The adverse events accompany tight lens syndrome include infiltrate, hyperemia and corneal abrasion.
Previous soft contact lens specifications:
Base Curve 8.7
Diameter 14.5
Power OD -3.00 -1.75 X 30 OS -2.00 -1.75 X150
Lens Design OSI Toric Disposable
Previous Menicon Distance centered Bifocal lens specifications:
Base Curve 760
Diameter 9.6
Power OD -4.75 OS -4.50 Add OU +150
Menifocal is a distance centered bifocal lens with an aspheric transition zone followed by a near centered annular.
Manifest Refraction
OD -300 -1.75 X 30 20/20 Add +1.50
OS -3.25 -1.75 X 150 20/20 Add +1.50
Keratometry
OD 42.12 X 44.25 @ 110
OS 42.50 X 44.50 @ 70
Slit Lamp Biomicroscopy: Lid eversion exhibited a smooth satin appearance without papillae. The inferior tear meniscus appeared clear and adequate in height to support contact lens wear. Tear breakup time was greater than 15 seconds in each eye. The meibomian glands excreted clear fluid upon gentle expression and no capped glands were present. No corneal staining was evident with sodium fluorescein application. Lower lid was at limbus.
Intra Ocular Pressure 8mmHg OU
Pupil response was equal, round and reactive to light and accommodation with no afferent papillary defect in each eye. Normal room illumination pupil size OD 4.2mm OS 4.3 mm. Horizontal Visible diameter in each eye was 11.5 mm.
Macular Pigment Optical Density .41
Fitting Concepts
SynergEyes lens designs need to vault over the cornea apex and land smoothly upon the peripheral cornea. In a spherical eye the lens design can easily vault over the corneal apex with a clearance of 0.50 diopter. In an astigmatic eye the rocking motion of the lens will adequately pump tears under the entire lens. The best fit is accomplished by taking the average of the flat and steep meridian and select a base curve that is .50 steeper.
When the resultant calculated base curve selection falls between the base curve option, select the closest steep base curve. An example of a spherical keratometric value of 42.50 X 42.50 would result in a base curve calculation of 43.00(7.85) and the closest steep base curve lens option selection is 7.80.
In an astigmatic eye the keratometric value of 42.50 X 45.50 would result in a base curve calculation of 44.50 (7.58) and the closest base curve lens option selection is 7.60. The skirt curve is available in 1.0 and 1.3 flatter than the rigid base curve. Always select the flattest curve in order to reduce the likelihood of seal off and allow for adequate tears to be pumped underneath the lens design. These lenses might seem to appear significantly loose upon application onto the eye. Although after ten minutes on the eye they become considerably tighter. I have witnessed soft skirt gapping and patient discomfort initially and after
ten minutes the soft lens portion of the lens constricts and lays flat and patient’s subjective response is very positive. I usually will have my assistant place the lens on the eye and evaluate after at least ten minutes. This is a very critical step in finding the appropriate lens fitting parameters. If the lens continues to gap then the steeper, 1.0mm flatter than the base curve parameter is selected.
DP sim K reading was OD 42.37 X 44.12 @ 110 average K calculated as 43.25 and adding 0.50 resulted in 43.75 (7.70) selecting a base curve of 7.70 OS 42.50 X 44.50 @ 70 average k calculated as 43.50 (7.76) selecting a base curve of 7.70. Soft skirt selection was 1.3 and resultant curve was 9.0. Over refraction of trial lens resulted in a -4.00 OD and -4.00 OS with a +1.25 add OU.
Near center size selection is based on trial lens performance. The SynergEyes lens is a simultaneous lens design so distance and near optics are within the pupil zone. Distant and near vision is accomplished by selectively suppressing the out of focus image. This lens design cannot be forced upon a visual system that cannot interpret the information that the lens design provides. It is an inherit ability that most of the time a patient will not adapt to over time. Some patients will immediately feel comfortable this bifocal option and other patients will respond as if they are viewing a foreign language. These patients generally will result in failure. The only option will be to incorporate an aspheric or alternating bifocal arrangement. A 1.9 near center lens was placed on one eye and a 2.2 near center trial lens placed on the other eye. Loose trial lenses were hand placed over each eye separately to experience both the effects on distance and near vision. Always select the smallest near center zone size that will accomplish both adequate near and distant vision. The 2.2 near zone bifocal will usually diminish the quality of distant vision and will increase the likelihood of halos and 3D vision. At times selecting a 1.9 near zone size for the dominate eye and a 2.2 near zone size for the non-dominate eye will accomplish adequate distance and near vision. Another option is to use two 1.9 near centered lenses and add plus to the non-dominate eye. DP responded very positively to a 1.9 near zone with adequate distant and near vision. The trial lenses had incorporated a +1.75 diopter reading zone that elicited a reading zone of ten inches so a +1.25 reading zone was ordered.
SynergEyes Lens Specifications
Base Curve Rigid/Skirt 7.70/ 9.00 mm OU
Diameter 14.5mm
Power -4.00 OU Add +1.25 OU
Near zone size 1.9
Dispensing Visit
Lenses were placed on the eye without anesthetic with the concave side filled with Optive and high molecular fluorescein without rinsing. It is important to place the lens on the eye without air bubbles underneath the rigid portion. A thin layer of fluorescein was exhibited under the rigid portion of the lens without any seal off underneath the skirt portion. The lens moved with the blink approximately .5 mm upon upward gaze, although the lens maintained its central position.
Visual acuity with the SynergEyes lens:
OD 20/20 distant overrefraction Plano
Near acuity 20/20
OS 20/20 distant overrefraction Plano
Near acuity 20/20
DP was instructed on proper lens application, removal and lens cleaning. A SynergEyes instruction video was first shown to DP before his teaching. DP demonstrated proper lens application and removal. Miraflow was given as a lens cleaner and Clear care was given as a disinfection method. Optive was also given as an insertion lubricating/wetting drop. DP was instructed to start wearing the lenses all his waking hours. A follow up appointment was scheduled for one week.
One week follow-up visit
DP returned to the office at one week after the dispensing visit. DP was comfortable wearing the SynergEyes bifocal lenses all waking hours. He did not experience any material getting underneath the lens the entire week especially at the baseball field. The lens design allowed him to perform all his visual demands at work and on the baseball field.
The lenses were removed and topography was performed to check any molding characteristics imparted on the cornea. If the cornea had flattened then the lens would be fitted to flat. If the corneal curvature became steeper or took on a more spherical shape then the lens design was fit to steep. This technique can uncover a poorly fitted lens before creating an adverse event.
DP was very satisfied with the lens design and matched his expectations of improved comfort and stable and pristine visual acuity for multiple working distances.
Discussion and Alternate Treatments
The SynergEyes bifocal lens is a near centered simultaneous lens design. Proper patient screening for this lens design will improve the success rate significantly. Patient comfort, visual acuity and lens handling are important patient parameters that can create lens failure. Each area needs to be discussed with every patient to guarantee a successful outcome. The near center simultaneous bifocal lens design can generate ghosting, haloes and a 3 D effect creating a discomfort visual experience. Discussions with the patient describing this visual occurrence will help explain a normal consequence of this lens design.
Appropriately fitting the SynergEyes lens will reduce the occurrence of the tight lens syndrome. Using high molecular fluorescein, allowing the lens to settle on the eye at least for ten minutes, checking topography at the one week visit and fitting the lens accurately will assure a successful outcome. The lens design must vault the corneal apex centrally although cannot be so steep that the skirt seals off the flow of tears underneath the lens.
DP could have been fit with a disposable Proclear toric bifocal as an alternate lens design or an aspheric reusable bifocal lens design. DP could have also been fit with a gas permeable aspheric lens design in a piggyback configuration. The SynergEyes simultaneous near centered bifocal lens design satisfied DP’s visual goals for comfort, vision and convenience.
Case 2
By: Dr. Rob Davis
Vision can be a life changing event
LC is a 62 year old male patient I have followed for twenty years trying the newest contact lens designs to achieve the best visual acuity possible and improve comfort. LC has congenital nystagmus as well as narrow deep set eyes and tight lids. Due to his steep corneas and narrow palpebral apertures his GP lenses fall off the cornea with rapid eye movements. LC has a plus manifest refraction resulting in the center of gravity in front of the lens creating the lens to fall like a rock on the cornea with each blink. Centration is maintained by his lids although when given the opportunity the lens will slide off the cornea.
LC is taking Travatan and Alphagan for glaucoma and Patanol for itching. LC is also on a computer eight hours a day at work in an office environment with very little humidity. His work cubical is dusty and arid creating a perfect dry eye scenario.
LC lost his job because of the Ocular Surface disease preventing continuous work developed from his dry eye and environment. Dry eye is a multi-factorial anomaly resulting in symptoms of discomfort, visual disturbance and tear film instability with potentially damage to the ocular surface. As his keratitis developed LC’s ability to perform at near was compromised from the friction of the nystagmus, the toxicity from the preservatives in the medications, long hours at work that dehydrate the cornea and the poor environmental conditions at work.
His whole life was now centered on his vision discussing with anyone who would listen about what he could do and what he could not do because of this eyes. His wife left him because of his thoughts only was fixated on his eyes and his lack of assurance to go out in public anymore. His total life was disrupted and felt depressed.
Refraction:
OD +3.00 – 2.50 X 165 Add +2.50
OS +2.75 – 3.25 X 30 Add +2.50
OD: Distance 20/70 Near 20/60
OS: Distance 20/80 Near 20/60
Corneal curvature:
OD 44.87 @ 160 and 47.37 @ 70
OS 44.50 @ 16 and 47.12 @ 106
Pachymetry: OD 527 OS 550
Intra Ocular Pressure: OD 13 OS 14
Cup/Disk ratio Horizontal/Vertical: OD 7.5/8.0 OS 8.0/8.5
| Previous Contact Lens: Decarle Back Surface Annular |
| | OD | OS |
| Base Curve: | 760 | 760 |
| Diameter/Optic zone | 9.0/7.8 | 9.0/7.8 |
| Power/Add | +2.75/+300 | +2.00/+3.00 |
| VA Distance/Near | 20/70 20/60 | 20/80 20/60 |
Slit Lamp Evaluation: Tears demonstrate reduce meniscus with strands of mucous within the tear film. TBUT measured for the OD 6 seconds OS 8 seconds. Cornea exhibited slight cloudy and grade 1 SPK OU inferior central. Bulbar and palpebral conjunctiva exhibited grade 1 hyperemia. Flip lids demonstrated a grade 2 papillae resulting in the diagnosis of giant papillary conjunctivitis. Chambers are deep and free of cells and flare. Iris appears healthy, normal anatomy and convexity.
Visual fields: OD
OS
Internal: Vitreous body clear for age and fully attached. No drusen, exudate, hemorrhages or evidence of retinopathy. Intraocular pressures are controlled and stable using the current therapeutic regimen. No increase in cupping by ophthalmoscopy and slit-lamp. Today's visual field testing does not reveal a progression of this condition.
Contact Lens fitting:
LC was fit with a new piggyback lens design with a cut out in the center of the soft lens and the Gas permeable lens fitted inside. The combination lens moves as one unit. The diameter of the hydrophilic cut out is designed a few tenths larger than the gas permeable bifocal lens design. The soft lens base curve controls the fit of the lens and the rigid lens controls the optics of the system. Lens movement can be incrementally controlled by the base curve of the soft lens. More movement is generated by a flatter soft lens. A soft hydrophilic cutout with a base curve of 8.20 was selected to generate enough movement for a bifocal gas permeable lens to translate to the reading area.
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The diameter of the soft lens was 14.5 for good centration and a 9.6 cut out was selected to receive a 9.5 diameter gas permeable bifocal. The power of the soft lens was -2.00 although the power does not affect the power of the system. The rigid lens base curve was OD 7.50 and OS 7.40. The power of the rigid lens was +2.75 OD and +2.00 OS with an bifocal add of +2.00. The bifocal design of the rigid lens was a front surface annular to optimize the optics of the bifocal power. An aspheric lens could have been used although the eye movement generated by the nystagmus, would make it difficult to have stable vision through the bifocal portion of the lens. The constant horizontal movement from the nystagmus along with the vertical movement with the blink would make it difficult for the visual system to look through a constant near power generated by the aspheric bifocal design. Whereas in an annular lens design the distance power and one reading power through the bifocal portion of the lens, movement would not interfere with the stability of vision.
A trial aspheric bifocal lens design was applied and LC responded as if the vision was smeared at distance and near. He described the vision as not sharp and he could not resolve the acuity chart. When an annular design was applied LC’s response was very different. Vision was crisp and pristine. Even though the powers were the same he now could resolve the acuity chart. The annular lens design provided improvement in stability of vision.
Contact Lens Design
OD Soft Base Curve 8.20 Diameter 14.5 power -2.00 cutout 9.4 Ocufilcon
Rigid Gas Permeable Base curve 7.50 Diameter 9.0 power +2.75 Add +200
Annular Design Optic Zone 8.0 Near Zone 3.0 Boston XO
OS Soft Base Curve 8.20 Diameter 14.5 power -2.00 cutout 9.4 Ocufilcon
Rigid Gas Permeable Base curve 7.40 Diameter 9.0 power +2.00 Add +2.00
Annular Design Optic Zone 8.0 Near Zone 3.0 Boston XO
The soft lens was first applied on the eye and the rigid lens then was placed within the cutout portion of the soft lens. When the rigid lens was placed onto the soft lens portion, the rigid lens floated into the soft lens cutout as if it was a drain, floating into position.
Visual Acuity Distance/Near
OD Distance 20/60 Near 20/30
OS Distance 20/70 Near 20/40
LC described the comfort better than he has ever felt a lens on his eye. Centration of the rigid portion was maintained by the soft lens. Vertical lens movement was sufficient to change gaze into the reading portion of the lens with a focal point of 18mm for the computer. Reading glasses were prescribed to move the focal point to 13 inches with a +1.50 flat top bifocal. LC was instructed on proper lens application, removal and lens cleaning. LC demonstrated proper lens application and removal. Miraflow was given as a lens cleaner and Clear care was given as a disinfection method. Optive was also given as an insertion lubricating/wetting drop. LC was instructed to start wearing the lenses all his waking hours. A follow up appointment was scheduled for one week.
One Week follow-up
LC returned to the office at one week after the dispensing visit. LC was comfortable wearing the Combination Hybrid cutout bifocal lens. The lens design allowed him to perform all his visual demands at work initially. After approximately three hours the lenses started to bother him and felt dry. LC removed the lenses and re-applied them and they felt better immediately although it only lasted a few more hours. He started to get photophobic and the eyes felt scratchy. We discussed the use of comfort drops and he replied that they work for about five minutes and his symptoms return. We discussed punctual occlusion and a decision was made to insert plugs into the lower punctum of each eye. The smart plug by Medennium was used to fit into the lower canaliculi. The procedure went without complication and a follow-up appointment was scheduled for ten days. All other findings remained the same as the dispensing visit.
Three Week follow-up
LC returned to the office for his three week follow-up appointment. His vision had significantly improved both at distance and near with the new lens design. The vision seemed to be more stable than before and the aid of flat top design reading glasses made near point easier to perform his work although he had to hold the near point task closer than before when he looked through the bifocal and glasses simultaneously. The contact lenses allowed LC to perform at the computer. The only problem was that he could not sustain his work for a complete eight hour day. After the punctual occlusion the dryness and scratchy feeling returned after approximately six hours of wear.
What would be your next therapy?
Case 3: Essential GP Patient Refit
into Reclaim HD
By: Dr. Doug Benoit
Patient MG, a 59 yo female, executive assistant, presented for her annual examination. At that time her only complaint was of decreased near vision with her GP multifocals. Her current lenses were about two years old. Her distance vision and comfort were fine. She reported now problem with spectacle blur after the lenses were removed.
External eye health was normal, with minimal dry eye signs. Tear break up time: 12 seconds OD and OS. Pupils: 4 mm in normal light.
Current glasses RX:
OD –3.00-0.75x 180 +2.25 Add
OS –2.75-0.75x 175 +2.25 Add
Her current parameters were:
Essential GP
OD 7.70 mm base curve, -3.50 D, 9.5 mm LD, Series 2
OS 7.70 mm base curve, -3.25 D, 9.5 mm LD, Series 2
Both lenses had an optimal fit/fluorescein pattern.
Movement was good in all positions of gaze.
Vision:
OU 20/20 at distance, 20/30 at near.
+0.50 OR gave 20/20 at near
New lenses ordered: Essential CSA, same parameters as previous lenses but with +0.50 anterior surface Add in a 4.30mm zone.
Comfort was good, the fit was the same, and near vision was 20/20 OU, but distance vision was 20/25 and the patient was bothered by it. The patient was advised to try the new lenses for a week or so to see if it was an adaptation issue. Upon return, there was no change in the distance vision.
The next lenses ordered were the same original Essential parameters except that a Series 3 Add was ordered. These lenses gave 20/20 vision at distance and near. The fit was slightly flatter based on fluorescein evaluation, but comfort was good and the patient was happy.
The patient called about two weeks later to report that vision with the new lenses was great, but she now could not see with her glasses when the lenses were removed. This spectacle blur lasted for 2 -3 hours.
About this time the Reclaim HD lens was being introduced. I ordered a pair with the following parameters, based on the empirical fitting guide:
OD 7.75 mm base curve, -3.50 D, 9.5mm LD, +2.50 Add/3.0 zone
OS 7.75 mm base curve, -3.25 D, 9.5mm LD, +2.50 Add/3.0 zone
Theses lenses were dispensed and gave 20/20 vision at distance and near.
The fit was optimum based on the fluorescein pattern, and the patient was comfortable.
At the follow-up visit, vision and comfort were unchanged. The patient noted no problem with spectacle blur after the lenses were removed.
This case illustrates how sensitive some patients/corneas are to changes in the cornea/base curve fitting arrangement. For this reason, I prefer aspheric multifocals with a low E value. There is generally much less corneal molding with these designs, compared with previous lenses that incorporated higher E values to generate their Add power. The downside to the low eccentricity designs is the limited Add power that can be generated. Newer lenses like the Essential, and now the Reclaim HD, utilize proprietary technology to generate their surfaces and higher index of refraction materials to help create the desired Add powers. According to the laboratory, Blanchard’s new Reclaim HD has a lower e value posterior surface, which gives some Add and does not tend to cause corneal molding. The rest of the Add power is generated by aspheric anterior surfaces of varying zone sizes. These changes combined, with high index materials, give great near vision, minimal compromise to distance vision and no spectacle blur.
Links to Case Studies:
