Gas Permeable Problem-Solving
With Dr. Grohe, Dr. Kendall, and Dr. Maller
Links to Case Studies:
Case 1
Dr. Ken Maller
History
Patient Z.S., a 29 y.o. wf presented to me 11/05. She had Lasik in 1997 in each eye and an additional Lasik surgery on each eye in 2001. The surgical results were poor with significant corneal irregularity in each eye. Her best corrected VA in spectacles is OD -2.25 -3.00 X 090 20/40, OS PL - 2.75 x 075 20/50-.
She is an attorney and this level of acuity (not to mention the poor quality) has created a great deal of difficulty in doing her job. She is in good health and taking no medication.
Using the current lenses that I designed she best corrects to OD 20/20+ and OS 20/15. She is wearing the lenses comfortably 14 - 16 hours per day. In addition to the obvious improvement in acuity, the quality of her vision is significantly improved.
The patient's topography is figure 1a (OD) and figure 1b (OS), the lens design is figure 2a (OD) and figure 2b (OS), and the summarized lens specifications are in figure 3.
figure 1a
figure 1b
figure 2a
figure 2b
figure 3
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Case 2
Jon H. Kendall, OD
A 55 yof comes in for her annual evaluation. Her chief complaint is very similar to those who wear annual replacement contacts, "it's time for new lenses."
VA was 20/25= OD (distance), and 20/25= OS (near).
Her current pair of contacts were CSIs for daily wear. She has been utilizing monovision for over 12 years.
Old contacts:
- OD 8.6 13.8 -9.00
- OS 8.6 13.8 -7.50
Manifest:
- OD -9.75 -0.50 x 155
- OS -10.50 -0.25 x 180
The lenses moved and centered well, but SLE revealed almost 360 degrees of superficial neovascularization. In the past the patient and I had discussed refitting to gas perms, but she had poor experiences as a youth wearing PMMAs.
Ks:
- OD 42.12 x 41.37 @ 167
- OS 42.00 x 41.00 @ 006
I decided to start with a thin lens design due to the powers I was working with.
Thin lens design ES material:
- OD 8.23/41.00/9.3/-9.00
- OS 8.18/41.25/9.3/-7.50
Pt was thrilled with her vision upon dispensing, with a plano over-refraction, She got 20/25 for distance (OD) and 20/20 for her near eye (OS). I decided to stay with monovision, although the patient was given the option of pursuing a multifocal fit.
At week one she returned wearing her softies. Her complaint was that of distance blur, and, "always feeling the lenses."
My options are:
- Giving up and moving her to a silicone-hydrogel.
- Finding out why the distance blur, and see if improved vision will offer "motivated" comfort.
- And what about comfort?
- other ideas?
With the particular proprietary design of my lab's lens, there are features you just cannot control. I always had the option to design my own lens, which I was tempted to do. The OD rode a little high and slightly temporal. My feeling was the blur was caused by the decenter optical zone. Otherwise both lenses looked pretty good.
What I did is stay with the same lens design, and increase the diameter to 9.8, steepening the lenses by a quarter and compensating for power. The center thickness remained at .08, and the edge lift actually improved with the larger diameter (I'm still trying to figure that one out).
These changes improved comfort and vision, by offering a larger OZ, and not by creating a more superior riding lens, which was a concern with going to a larger diameter.
The patient is remaining the lenses, enjoying the improved clarity, and corneal health they provide.
Take home pearls is to always keep the patient motivated, especially if the first fit design doesn't work as planned. Pts are reminded that these are custom made devices, and we will solve the problem.
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Case 3
Jon H. Kendall, OD
A 53 yof comes in with a complaint of needing new gas perms due to their scratchy feeling. She is fit in monovision which provided 20/25 OD (near), and 20/25 OS (distance). The fluorescein pattern revealed a flat fit OU, and pretty severe 3:9 staining. The lenses are pretty scratched up. She also used OTC +1.25 readers.
Ks:
- OD 47.00 x 46.62 @ 170
- OS 47.00 x 46.62 @ 170
Manifest:
- OD -10.25 -1.75 x 170 20/25=
- OS -11.25 -0.50 x 165 20/25=
Prior CLRX:
- Aspheric Fluoroperm 30s
- OD 7.28/46.37/8.6/-7.75
- OS 7.28/46.37/8.6/-9.25
I increased the diameter from her current 8.6mms to 9.0mms, trying to combat the dreaded 3:9 staining, and I also steepened up the lenses. I stayed with a design of my own instead of an aspheric one.
- OD 7.22/46.75/9.0/-7.75
- OS 7.22/46.75/9.0/-9.25
Pt returned in one week with the comments that the reading eye (OD) lacked a range of vision, although it was clearer than her old lens. And the left lens' vision was poor, even though the lens felt great. SLE revealed the OS was adhered to the cornea in the inferior position. Over refraction indicated a -0.25 to the reading eye improved her range, as did decreasing by -0.25 for her distance eye. The 3:9 was improved but still present.
What to do to improve the adherence of the OS lens?
- change the size of the OZ?
- changing diameter of the lens?
- improving cleaning and relating, and blinking with the patient?
This is what I like about working with GPS, you have all sorts of options to choose from.
I decided to go back to an aspheric design. My labs proprietary design allows me to control edge lift as well, so I felt it was a good choice to try.
- OD 7.24/46.63/9.0/-7.50/lenticular steep edge profile/ES material
- OS 7.18/47.00/9.0/-10.62/lenticular steep edge profile/ES material
One week later there was no sign of adherence for the OS, and the 3:9 staining had been reduced to an "acceptable" level. Slight corneal staining, but no bulbar injection.
Take home pearls.
- You have to be knowledgeable about the different proprietary designs your lab has to offer you.
- You have to be aware of the options each design offers you for a refined fit.
- Many labs don't offer the control options up front for each design, so you'll have to ask your consultant what your options are.
- Plus, there is more than one way to skin a cat.........(don't ask me how that applies here, but it's the only saying that comes close), often times with gas perms you have several different options to solve certain fitting problems.
- You must examine all the options, and understand that for every action you take, there is another one which may pop up. This is what makes fitting gps so interesting.
- If you can handle these normal fitting problems that pop up, you can easily handling fitting a distorted or post surgical cornea because you will understand more about design.
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Case 4
Robert Grohe, OD
History
Here is a case of a 31 year old male who is a previous six year soft toric contact lens wearer. He has gone through numerous lens replacements prompted by a perceived need to replace lenses which provided inconsistent or fluctuating vision despite a "toric' correction. With his job requiring a 6-8 hour per day computer use and ongoing critical vision, this patient requested contact lens options beyond soft torics. An Orbscan topography map of the right eye reveals normal AF & PF values, normal corneal thickness with a Sim K for the OD: 43.00 x 45.00 @ 89 and a refraction of - 4.00 -2.50 x 175 = 20/20. The OS has an almost identical K, topography and Rx.
The patient was successfully refit with a spherical pair of Fluoroperm HDS 100 fit on-K or using a 43.00 D. base curve, 9.4 mm OAD, 8.0 mm OZ, a center thickness of 0.20 mm to suppress potential lens flexure and a low edge lift to minimize excessive lens movement. A visual acuity of 20/20 for the OD & OS and a 20/15 OU vision was achieved. Other lens options would include a possible bitoric or bi-aspheric design, toric peripheral curves or low specific gravity materials to encourage central to superior lens positioning.
With-the-rule astigmatism cases represent an ideal opportunity to use GP's for improving the quality and stability of vision. Consistent vision is much appreciated by moderate to heavy computer users. GP fitters can rapidly build success, confidence and new patient referrals through successful soft toric refits. WTR astigmatism cases also represent a major source of revenue for ECPs by correcting toric errors with either soft torics or gas perms.
figure 4 (Click here to open a PowerPoint View of this image.)
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