Astigmatism / Biometric Lenses / Dry eye — No comments
30
Aug 10

The teardrop lens

OK, I’ll say upfront that I’m getting a little loose and cutesy with the title of this post.  But I saw a patient this morning who has been wearing my scleral lenses for the past several years and who has been quite happy with them, until recently.  They are the fenestrated type, and the lenses had developed some central deposits where the tear layer pools and becomes stagnant.  So, I switched him to mini-sclerals without the fenestration, and he loves them.

This morning he told me that he uses decidedly less rewetting drops during the day than with his previous set.  But, he has also noticed this little burst of moisture at the end of the day when he removes his lenses, which he says is kind of a pleasant bonus.  This, of course, is the liquid that is held between the cornea and the scleral lens.  It immediately brought to mind those little cherry cordials with the liquid center.  Perhaps this will inspire a new marketing strategy. . .

Astigmatism / Biometric Lenses / Dry eye / Keratoconus — 5 comments
29
Aug 10

Crunch time

This is the last day for me to catch up on the work from the previous week.  Shortly I need to get busy designing scleral lenses for a couple of patients from the scans I took earlier in the week.  Being able to work from scans allows me to virtually fit the lenses in a more relaxed setting without having the patient sitting in front of me and several more in the wait area.

The first patient is a keratoconus patient who I am switching from a fenestrated scleral into a full scleral.  He’s not having any problems, but his prescription is changing and I sense that the lenses are settling back too much with those fenestrations.  Non-fenestrated sclerals will allow me to create more vault and more corneal clearance.  The second patient is new and has a very advanced case of keratoconus hydrops with central scarring.  her corneas are paper thin and I strongly recommended that we start looking at the transplantation process.  In the meantime I need to get her out of those incredibly tiny RGP lenses she has been wearing until we can get to the transplant stage.  If I have any time leftover, I would like to play with a new lens algorithm that Truform sent me.

Last night we had dinner with some friends.  He is in his late seventies with dry eye and more than 4.00 D of astigmatism, against-the-rule.  He has been wearing my scleral lenses now for more than 2 years.  The first thing he asked me last night was where my contact lenses were (in reality I was wearing my progressive reading glasses over my Oasys).  Of course, the whole intent was to remind me that he was not wearing any glasses.  He wears his scleral contacts from morning to night.  Besides the very high astigmatism, he suffers from post-cataract surgery dry eye, and his vision with the contacts is far superior to what he gets with spectacles.  He has wanted to wear contacts for many years, but the combination of dry eyes and astigmatism kept it from happening…until now.

Update:  It’s now 2:15 and time to head out for a bike ride.  It’s beautiful outside.  Not too hot.

Contact lenses other — No comments
28
Aug 10

Into the wayback machine

I found this article about Saturn II lenses and advanced keratoconus.  The Saturn II lens was the predecessor to the Softperm, which was the predecessor to the Synergeyes.  Hybrid lenses were developed more than 2 decades ago when the only choices were soft lenses and those little uncomfortable rigid lenses, and when scleral lenses were made from impression molds of the eye (lightbulb moment: soft + hard = hybrid).

CLAO J. 1991 Jan;17(1):41-3.

The use of Saturn II lenses in keratoconus.

Maguen E, Martinez M, Rosner IR, Caroline P, Macy J, Nesburn AB.

Ophthalmology Research Laboratories, Cedars-Sinai Medical Center, Los Angeles, CA 90048.

Abstract

We studied Saturn II contact lenses in keratoconus patients who were intolerant to other available contact lenses. A total of 24 patients, who were followed for up to 15 months, participated in the study. Visual acuities improved significantly following fitting with the Saturn II contact lens; whereas only one eye in the series was correctable to 20/20 before fitting, eight eyes were corrected to 20/20 following fitting. A great number of lenses had to be replaced during the study because of deposit formation and tearing at the interface (rate of replacement: 0.52 lenses per eye per month). A variety of complications occurred during lens wear, resulting in only six eyes wearing the Saturn II lens at the close of the study (out of 46 eyes that had started wearing the lens). Discomfort due to tightness of the peripheral segment was the most common cause of lens discontinuation. We conclude that the Saturn II lens was inadequate for fitting patients with advanced keratoconus.

Biometric Lenses — No comments
26
Aug 10

On getting it right

While I’m enjoying a “breather,” I thought it would be nice to recap what we have accomplished with our lenses during the past few years.  Scleral lenses have traditionally been rather crude optical devices of last resort, and they have suffered from a number of technical problems that affected both comfort and vision.  Most think of them as large hunks of plastic about the size of shot glasses that come in a box of different shapes.  Success was always a combination of the time available, the skill of the fitter, and the size of the box of trial lenses.  Now all of a sudden, scleral lenses have burst onto the scene in a virtual flood of offerings from the manufacturers.  Their use is promoted by stressing not only their problem solving capabilities, but also how relatively easy they are to fit.  The latter is a seriously mistaken notion in our view.

Dissatisfied with the status-quo, we have learned the behavior of these lenses and how to tame them.  Most of the items on this list were implemented to solve problems that were encountered with earlier versions and to satisfy the most discriminating patients.  We have re-invested a large percentage of our profits from scleral lenses back into research and development to achieve something that is more than just a bandaid on the eye.  The mediocre vision that has been the hallmark of scleral lenses for so long is now a thing of the past.  Through our efforts, more people are “getting it.”  It’s one thing for a patient who, because of severe pain or other reasons, is “compelled” to wear scleral lenses.  It’s quite another when the clarity and comfort of the scleral lenses is such that patients choose them over their softs and other lenses, and yet that’s how far we have come: not just plastic bandages but precise optical instruments.

  • Adapted OCT imaging to measure the anterior eye and design lenses from those measurements.  There is currently no other technology that can accurately measure the anterior eye out to the sclera (currently patent-pending).
  • Used wavefront aberrometry to assist in the design of improved optics, to reduce coma and other induced artifacts using intelligent design principles.
  • Adapted Truform’s ability to manufacture quad-specific lenses to create more precisely fitting and more comfortable scleral lenses based upon the actual shape of the eye.
  • Used quad-specific technology to control lens rotation, thereby permitting the use of complex toric and asymmetric optical designs.
  • Ability to offset the front surface toricity from that of the back surface for the correction of induced astigmatism.
  • Employed a scalable design, i.e. variable diameter, to optimize the fit for eyes of any size.
  • Ability to do all of the above in a shorter amount of time at a lower cost.
  • Continuing to investigate design improvements in cooperation with Truform Optics.

All of this matters, or else we wouldn’t be wasting our time doing it.

Uncategorized — No comments
25
Aug 10

Taking a breather

The last few weeks have been busy.  I moved my son to Washington D.C. where he has started his new job.  He is a recent grad of the College of William and Mary in Williamsburg, Virginia, not far from D.C.  A number of his friends from the business school are also starting their careers there, which makes the move for him a lot less daunting.  We enjoyed our last road trip together, stopping off in Nashville for some great music (Buddy Miller and friends at the Country Music Hall of Fame), and then on to Williamsburg for one more great meal at the Fat Canary on dad’s credit card.  He made the 3 hour trip to D.C. on his own after dropping me off at the Richmond airport.  That was my summer vacation: 2 days in a car absolutely stuffed with all of my son’s material possessions: he slept and I drove.  But, it was all good.

So, we are now officially empty nesters.

Astigmatism / Biometric Lenses / Dry eye / Wavefront — 2 comments
06
Aug 10

Update: Residual HOA and astigmatism

Update: I saw this patient this past week.  The fact is that we were able to achieve 20/15 vision in each eye, completely neutralizing the lenticular astigmatism.  The already low levels of higher order aberrations were further reduced by the 16.0 mm scleral lenses with a design to reduce coma.  I anticipate a first hand account after he returns home.  The original post from a few weeks ago follows.

Update: The patient talks about the experience in his own words here.

Having temporarily run out of topics, it’s time to turn to the e-mailbag.  This patient had LASIK and enhancements, wears hybrid lenses, and has residual astigmatism.  Current issues are dryness, persistent blur in one eye after removing lenses, and some night vision disturbances.  Can these issues be resolved with Biometric scleral lenses, including the higher order aberrations?

Based upon what we have recently discussed on this blog, we know that residual astigmatism can be corrected with the appropriate lens design.  Hybrid lenses just don’t have great stiffness and will flex in the presence of significant anterior toricity.  The dry eye symptoms should be improved in the absence of a hydrophilic material, and a comfortably thick layer of fluid will be retained against the cornea.  Since the lens doesn’t touch the cornea, there should be no induced corneal changes causing post-wear blur.  The HOA is another matter.

The RMS total HOA for this patient are reported as 0.22 microns in the OD and 0.37 microns in the OS for 5.5 mm and 6.0 mm scans respectively.  According to our copy of Salmon’s pooled data, the MEAN total HOA for the normal population is 0.33 +/- 0.13 microns.  This patient’s HOA is well within the norms.  Given that they are already so low, no contact lens will likely reduce these aberrations further.  Citing one of my own papers, the lower the HOA, the less reduction is possible with a contact lens.  The good news is that all the other items should be improved with Biometric sclerals.

The rule of thumb is that the greater the surface HOA, the greater the magnitude of the potential reduction, and the greater the likelihood that the patient will appreciate the improvement.  As noted previously, the average reduction is about 70% for total HOA and close to 90% for individual aberrations such as spherical and coma.

DrG: www.globalrefractivesolutions.com

Humor — 2 comments
04
Aug 10

What’s in a name?

“That which we call a rose, by any other name, would smell as sweet.”

I just figured out that I need to update my professional jargon.  I am speaking of scleral lenses.  Why do we call them scleral lenses when the purpose is to provide a dome over the cornea?  I use the term b-i-o-m-e-t-r-i-c to differentiate my product from the crowd in the sense that each lens is as unique as the measurement (metric) for each eye (bio-).  So, I’m going to try to drop the name “scleral,” and just call them Biometric Lenses.  That would be a good start.

If I wanted to get creative, I could call them ocular surface prostheses.  The trouble is that I don’t really like the term “prosthesis.”  It sounds like something artificial as in an artificial limb.  It conjures up and calls attention to disability.  But the ocular surface part is good.

I really like this one: prosthetic replacement of the ocular surface ecosystem.  There’s that word “prosthesis” again, but I love the term “ecosystem.”  I never gave a thought to having an entire ecosystem on my ocular surface, but it’s so true.  Unfortunately, that one is already taken.

So, I’m wondering: Is the term Biosphere available, as in Biometric Biospheres or Biometric Biospheric Lenses?  Biospheric Biometric Lenses?  How about hydroponics…..?

Biometric Lenses / Wavefront — No comments
30
Jul 10

Quad optics: the power of 4 (updated)

I just followed-up with a scleral patient today.  I made original lenses for him last year as a result of complicated hyperopic PRK, but he wanted to see if I could help his night vision a little more.  Given that the aberrometry numbers looked exceptionally good, I wasn’t sure I could.  But I decided to try anyway, this time using quad-specific, multi-zoned optics, and quad-specific peripheral curves.  In the right lens, the powers range from +0.75 to +10.00 as the base curves vary.  The result, he said, is exceptional vision in all conditions, day or night and noticeably better than the previous bitoric scleral lenses.  At night, the stars are once again point sources of light.  I’ve seen similar results with a few other patients using this technique.

 

DrG: www.globalrefractivesolutions.com

 

Biometric Lenses / Contact lens mechanics / Contact lenses other / Physiological optics — 5 comments
28
Jul 10

Dog days and more from the mailbag

Update:  Well, it didn’t take long for this blog to catch the attention of Vistakon corporate.  A question was asked whether Vistakon intended to release a toric version of the TruEye.  The answer is that they have received FDA approval for this, but will probably wait to see how well the TruEye does in the U.S. market.  The U.S. has the lowest use of daily disposable contact lenses.  From my experience, it’s the $$$.

We’re getting a little break from the heat this week with afternoon showers.  Since it’s Wednesday, I’ll be trying to get a bike ride in-between those showers.  Among other items on the agenda this morning, I am anticipating a visit from the Vistakon representative.  I’ve been using their new TruEye daily disposable lenses and I must say that I am impressed with the comfort and clarity.  Then, other than making a few scleral lens adjustments and taking care of some board business, I am a free agent the rest of the day.  Meanwhile, from the mailbag:

Q:  I am going back to my local doctor again tomorrow, but feel I have exhausted all he can do for me.  Are you making your process available to other doctors?

DrG:  Unfortunately, I haven’t trained anybody else.  The Visante OCT costs in excess of $50K, but cheaper versions may become available, or other imaging devices that can measure the sclera may come online at some point.  Besides, a number of practioners do an effective job using the traditional trial lens approach.  I did for years.  If the patient can find a practitioner with an OCT, they can have the scans taken there and sent to me for lens design.  The lenses would have to be dispensed through the local doctor.  That would be one option to consider.

Q:  Regarding gas permeability, my research stated that lenses with higher Dk are better as they allow higher concentration of oxygen to permeate.   How does the liquid layer of tears affect oxygen from reaching the cornea?  Does it limit oxygen exposure since tears & fluid may “suffocate” the cornea tissue.    I do understand that all lenses will limit oxygen exposure to the cornea to varying degrees. 

DrG:  This is a complex subject.  The oxygen transmissibility of a material is called Dk/l, and has a linear relationship to thickness.  However, the cornea response is determined by the EOP, or equivalent oxygen percentage.  One study suggests that the EOP peaks at 20% with a hyper-Dk/l material of about 136.  The literature suggests that EOP is highly variable between different lenses and subjects.  All we can do is to control the Dk/l by our selection of material, as well as the overall and local thicknesses of the lens design.  Materials with a Dk of 100 are typically used for scleral lenses: Boston XO and Optimum Extra are the two that we use.  I have not personally seen many issues related to oxygen permeability of scleral lenses, but I agree that more research would be desirable.  In summary, the lens design should be as thin as possible consistent with other performance variables such as avoiding excessive flexure, fragility, etc.  In my opinion, Truform has always produced lenses with that goal foremost.

Q:  I went back to the eye center, this time consulting with the optho who does their laser vision.  I questioned him about sclerals and he certainly supported that as an option.  He said best case they would act as a new cornea for me.  He ruled out further refractive procedures and said they would not be able to correct my vision beyond glasses or contacts.  As my pupils are very large he is having me try alphagan drops to wear with my glasses.  While there I saw the optom I’ve been working with on the RGPs; he said sclerals would be something we could try but mentioned they are difficult to fit & wear.  My concern is that since the RGPs didn’t provide me with vision, the sclerals may be the same.  Also I googled and could not find anything on quad optic lenses…..are they new?

DrG:  For once I think that the ophthalmologist is more enlightened than the optometrist with respect to the contact lens philosophy.  Quad-sym or quad-specific optics are generated by dividing the optical zone into 4 quadrants, each with a different power, base curve, etc.  Occasionally this leads to a better visual result in cases where the central cornea has a non-uniform topography.  We use this technique fairly often, but generally try to keep things as simple as possible, and as complex as necessary.  It’s something that can be easily designed using our Biometric process.

Correction:  I mistakenly typed Truscleral instead of TruEye, the daily soft disposable lens from Vistakon.  This typo has been corrected.  I must have a bad case of “scleralitis.”  However, there is indeed a lens called Truscleral, which is a tradename of Truform Optics.

DrG: www.globalrefractivesolutions.com

Biometric Lenses — 2 comments
25
Jul 10

It’s all in the numbers.

Most of our scleral patients are seeing marks on their lenses.  No, those aren’t the result of careless manufacturing.  Those are actually laser engraved letters and numbers created by Truform during the manufacturing.  Their purpose is to denote the position of the lens on the eye and to identify the right and left lenses.  Each lens has a small R or L near the edge of the lens.  Those typically go on the bottom.  The numbers most often seen are 0, 90, and 180.  Every optometrist will recognize the convention: 0 is always on patient’s left, 90 at the top, and 180 on the patient’s right.  When those numbers are present, it denotes a lens whose shape has been designed to have different elevations in each of 4 different quadrants in each of the fitting zones to better match the shape of the eye.  In order to assist the patient in inserting the lenses in the proper orientation, a single large black dot is placed at the top edge of the right lens, and 2 large dots in the same position denote the left lens.  In this way, the dots typically remain hidden beneath the upper eyelid.  While the black ink typically wears off in time, the laser marks remain as a permanent guide to the correct orientation of the lens.

I am resisting the urge to have my signature placed on the lenses, LOL!

DrG: www.globalrefractivesolutions.com

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