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Introduction to Glaucoma and the Retina Nerve Fiber Layer (RNFL) – Dr. Oli

Introduction to Glaucoma

We have spoken about the importance of the way the front of the optic nerve looks like a disc (Optic Nerve Head).  I would like to get into a little bit more detail about the relationship of the retina to the optic nerve. What we are addressing is the Nerve Fiber Layer that originates in the retina and becomes the optic nerve as the fibers go to the brain.

How the Eye Processes Reflected Light

The reason we can see, is that light reflected from objects is focused onto the retina. The retina changes light to electrical signals. The signals travel from the bottom of the retina (cones and rods) up through various layers of the retina, ending up stimulating cells called ganglion cells. These cells then transmit the signal through long fibers (Retina Nerve Fibers) that travel on the surface of the retina then turn sharply as they converge and make up the optic nerve.

The way the nerve fibers make their way to the optic nerve is very important to understanding what happens in glaucoma.

The Path of the Nerve Fibers from Retina to Optic Nerve

Understanding Glaucoma Retina Nerve Fiber Layer

Nerve fibers from the retina travel in an arc to reach the optic nerve, both in the upper and lower retina. A line can be drawn through the middle of the optic nerve and the middle of the macula to the outer retina, which is like a “property line.” Fibers above this line come together in the upper optic nerve.  Fibers from below this line come together in the lower optic nerve.

Damage to the nerve fibers is seen most in the upper and lower optic nerve, hence vision damage shows most in the upper and lower field of vision on the nose side. This damage is known as nasal steps.

How the Optic Nerve Changes in Appearance from Glaucoma Damage

Damage to the upper and lower nerve fibers results in the cup getting progressively bigger in the upper and lower direction, hence it elongates vertically. A cup that is longer in the horizontal (side to side) direction argues against glaucoma.

The Strength of Evidence in Cupping

Changes in the cup are not always clear-cut, and often we are not sure what the cup looked like years prior to the present evaluation. When changes are not definite enough for us to say whether glaucoma is present or not we have to get evidence from other sources such as imaging of the Nerve Fiber Layer (RNFL) and from visual field testing.

Documenting the appearance of the optic nerve in stereo (three dimensional) with digital photography is, to me, a very important part of glaucoma care. Orion Eye Center has the very latest digital fundus camera.

The Importance of Eye Pressures

Eye pressure is a very important part of glaucoma, not so much in diagnosis as in monitoring the effectiveness of treatments. However, eye pressure is only one part of the treatment of glaucoma, the other components being changes in the Retina Nerve Fiber Layer, the Visual Fields, and the appearance of the optic nerve.

Lowering eye pressure, hopefully throughout the day and night, is the only treatment option open to us at present, hence the somewhat misplaced importance of focusing on eye pressure.

Treatment of Glaucoma

Treatment is focused on lowering the eye pressure. Several ways are available to lower eye pressure, which in main are:

1.            Various medications

2.            Lasers

3.            Surgery

We will discuss these various treatments in a future article.

We will also discuss how glaucoma damage manifests in the appearance of the optic nerve, the Visual Field, and Retinal Nerve Fiber Layer.

New Technology Impacts Cataract Surgery – Dr. Oli

It’s easy for us to take the technology we use for granted.  However, as I look back at the advances that have been made in cataract surgery since the days of Sir Ridley I am awe-struck.

The first intraocular implant to “cure aphakia” was performed in 1949 using 4x loupes. Just imagine doing cataract surgery using only four times magnification with poor lighting!  This is nothing short of awesome in my book.

I performed my first cataract surgery in 1979 using a 20x microscope, performing ICCE (Intra-Capsular Cataract Extraction) using a cryoprobe. I was so nervous that it was hard for me to control my legs, but I got through it in one piece. One must marvel at Sir Ridley using 4x loupes to remove the cataract via ECCE (Extra-Capsular Cataract Extraction) using can-opener capsulotomy and expression.

The operating microscope was invented by Zeiss in the 1960’s. Not much changed in microscope technology over the next twenty or thirty years. We bought a Leica microscope in 1996 to use in our ASC. I really liked the Leica scope, especially when compared to the older Zeiss model, due to its wider field and improved illumination.

Earlier this year Dr. Kristine and I saw a demonstration of the Lumera 700 Zeiss microscope at the Hawaiian Eye meeting.  We researched the scope via videos put on the Web and were very impressed by the improved visibility.  We liked what we saw and decided to pursue test driving this scope.

A couple of months ago we had the scope brought to our ASC. We were completely blown away!   The improved visibility was so incredible that we both agreed we had to buy the scope right then and there. We realized we could not continue using our Leica scope since patient safety is paramount in our practice.

Visibility is improved tremendously in both retina surgery and cataract surgery (see photos). With the Leica scope we could not videotape retina surgery.  With the Zeiss Lumera 700 scope we have videotaped several surgeries and have now produced two videotapes for educational purposes.  We have also produced two videos on cataract surgery. We are looking forward to putting out more videos as time goes on.

We are the third practice in Oregon to acquire the Lumera 700 and are the first private practice in Oregon to get this scope.  Both of the other practices are institutional in nature.

We encourage any of our local Optometrists who are interested to call and schedule time to observe surgery with me or Dr. Kristine.  We’re sure you’ll find it a very interesting experience.

What exactly is an ASC, anyway? – Dr. Kristine

 ASC – What do these letters stand for?  Is that some cheapie way to have surgery?  Is it more expensive to have such personalized treatment?  Does the patient have to stay overnight?  Are all ASC’s created equal?

To many, the letters ASC don’t mean much.  They stand for AmbulatorySurgeryCenter.   Eye Surgery Institute has its own ASC, right down the hall from the clinic.  The ESI ASC is dedicated to doing only eye surgery.  So, what are the advantages?  Are there disadvantages?

Surgery can be performed in two basic settings:  at the hospital, or at an ASC.  Here are some basic comparisons:

1.  Cost:  on average, it costs four times more money to have eye surgery done at the local hospital.  Unfortunately, some of that cost is transferred to the patient, in the form of co-insurance and deductibles.  Hospitals are reimbursed differently than ASC’s.  This reimbursement is determined by CMS (Medicare).  It had been decided that (among other factors) the overhead is higher at hospitals.  In addition, hospitals charge per item; in an ASC contract, an ASC receives a ‘bundled’ fee for any given surgery, so there are no extra charges for individual items.

2.  Ease:  At the hospital, and some other ASC’s, the patient has to check-in, change out of their clothes, put on a gown, have an IV placed, be sedated and undergo observation in recovery after surgery.  This process can take several hours.  In contrast, at ESI’s ASC, the patients are very lightly sedated, so that they may eat and drink prior to surgery.  In addition, they are able to stand and walk immediately following surgery.  There is no change of clothing, and no IV (unless specifically requested by the patient).  The process from check-in to leaving after surgery is very streamlined – it takes less than two hours, on average.  It is designed to minimize the inconvenience for the patient and the people who come with them.

3.  Viewing Room:  At the ESI ASC, the patient’s family or friends have the option of being in the viewing room.  In the viewing room, the surgery coordinator explains the cataract surgery, which is visible on a large screen television, as well as through the large window.  The surgery is optionally recorded, and given on a DVD as a memento.

4.  Staff Training:  At ESI ASC, only eye surgery is performed.  As the adage goes, “Practice makes perfect.”   The flow of equipment and the experience with the technical aspects are surgery are second nature to the technicians and staff, who participate in 20-35 cases each surgery day.  Since the staff is focused only on eye surgery, they become very proficient.   Practice making perfect allows for:  swift turnover, predictable results, lower infection rates and an overall efficient, lower-risk process.

5.  Personalized Care:  The patients that arrive for surgery are greeted by the same staff that assisted them during their surgical work-up.  They are greeted by name.  Fresh coffee, snacks and juice are available while they wait for surgery, and for family or friends.  After surgery, a specially trained staff member reviews the post-operative instructions with the patient and their attendants.  And, finally, the doctors call their patients on the evening of surgery to ensure that all is well following surgery.

So, are there disadvantages to having surgery at an ASC?  No, there is no downside, only upside.  Of note, the ESI ASC does not provide for surgeries that require general anesthesia. 

In conclusion, the eye surgery process at our ASC is:  easier for the patient, less expensive, more personalized and the staff are specialized.  It saves money (for the patients and healthcare); it reduces hassle and complications.  In addition, having a small, specialized ASC allows the owners to have more control over the personalized aspects of the surgical experience, which is a win-win for everyone!

Spherical Refractive Outcomes in Our Cataract Surgeries – Dr. Oli

Introduction

Cataract surgery has evolved to a point where refractive outcomes are now a major part of the results of surgery.  Spherical outcomes are determined largely by the power of the IOL which is determined by several formulas that have evolved over the years.  Astigmatic outcomes are dependent on the use of toric IOLs, limbal relaxing incision (LRIdone either with a blade or now the Femtosecond laser), and positioning of the cataract incision. There is also the option of using the Excimer Laser to correct refractive error.

The results below summarize our internal ESI study dealing with our spherical refractive outcomes after cataract surgery.

Our Study

The study is retrospective without any peer review. We wanted to know about our spherical outcomes in “short” eyes, “normal length” eyes, and “long” eyes.   The reason we decided to divide the outcomes into the above three categories has to do with the known fact that present methods of calculating implant powers works best for normal length eyes and less well with the longer or shorter eyes.

Modern formulas, in particular theHolladaysoftware program, have added factors other than axial length and keratometry to achieve better outcomes.Holladaywas most responsible for realizing the importance of postoperative estimated lens position (ELP).

ELP is known to vary with axial length, butHolladayfound that there are other factors such as White-to-White (corneal diameter) that influence ELP as well. Despite the knowledge that these factors are important we have no perfect way of predicting ELP at the present time.  

Our study excluded patients with prior refractive procedures, corneal pathology and those who were implanted with toric IOLs.

The Challenge of Benchmarking

There are no absolute comparisons we can use to judge our outcomes. There is always the theoretical “perfect” outcome we would wish for, namely emmetropia with no astigmatism.   This of course assumes the patient did not wish to remain slightly myopic.

There are some studies in the literature that have reported retrospective outcomes. Two such recent articles utilized the following benchmarks:

  1. 85% achieved final spherical outcome of +/- 1.0 D. 55% were within +/- 0.5 D of emmetropia.
  2. 80% of eyes achieved spherical equivalent within +/- 1.0 D of emmetropia.

Our study utilized these benchmarks as the standard against which we compared our outcomes.

Our Outcomes

            1.  The Group with Axial Length of 23-25 mm (“Normal” Eyes)

                        A.  We achieved an average spherical outcome of 0.2D.   The range                          of spherical refractive error was -1.25D to +0.50D.  Two out of                           thirty-four had greater than +/-0.5D error.

Due to these results, when we see a patient with spherical outcome that deviates by more than a 0.5D we restudy our preoperative data on which we based the IOL power calculation

            2.  The Group with Axial Length of 25-31 mm (“Long Eyes”)

                        A.  Average spherical outcome was again 0.2D.  Range was -1.50 to                         +0.25D.  The majority had minimal myopia.

            3.  The Group with Axial Length of 20-23 mm (“Short Eyes”)

                        A.  Average postoperative sphere was +0.25D.   Due to the small                             number of patients in this group the outcomes were not statistically                                 significant.

Conclusion

While our study was very encouraging, we are using the information gained to continually improve our results.  Our goal is to achieve outcomes within 0.25D of the desired spherical outcome. To pursue this outcome we have invested in technologies such as the iTrace (ray tracing) and OPD to determine the necessary information in the most accurate manner. Additionally we endeavor to keep up with upgrades and developments in the IOLMaster technology and spend considerable resources and time training and educating the clinical staff in the most accurate acquisition of data. Clinically we work hard to detect corneal surface and tear abnormalities and treat what is treatable prior to final IOL power determination.

We appreciate the efforts of our co-managing doctors to accurately determine the refractive outcomes and return them to use in a timely manner.  You are all helping us to continue on the path to a more perfect surgery.

Retinal Detachments – A 5-year review -Dr. Kristine

Now that I have been in Central Oregon for five years I thought it would be an appropriate time to review my surgical results for retinal detachments.

Reviewing a surgeon’s results helps educate the surgeon, the referring doctors, and most importantly the patients.  Naturally, surgical results vary.  These variations depend on the surgeon as well as the patients.

Retinal detachment treatment has evolved over the last 15 years.  There has been a transition away from scleral buckling as well as the advent of small-gauge vitrectomy.  International conferences regularly discuss the pros and cons of all retinal detachment techniques and tamponade agents as well as surgical approaches.  There still is little consensus.  And, the bottom line is:  what is each surgeon’s success with whichever modality they chose?

Personally I prefer primary small-gauge vitrectomy with either SF6 or C3F8.  I use silicone oil and scleral buckle in select cases if I feel the patient is likely to have a higher rate of success with that approach or if there are extenuating circumstances (for example, a patient with a macula-sparing retinal detachment, who lives in Florida…).

I had a few questions that I personally wanted to answer…  First, I take ‘fresh’ macula-off retinal detachments to surgery as quickly as possible (i.e., within 24-48 hours of diagnosis).  I wanted to know; do visual outcomes vary among detachments that have been present for 2 days compared to 4 days?  Second, I was interested to know what the visual prognosis was for retinal detachments that had been present for longer than a month; how should I consent the patients?  What hope is there?

In 5 years, I have done 134 retinal detachment repairs.  Of those detachments, 52 were macula-sparing.  Each year, I have done more retinal detachments (Chart 1)…

Published statistics vary regarding primary success in retinal detachment repairs.  The averages are 80-90%.  In the five year review, ESI has a 91% primary success rate at primary repair.  In addition, the success rates vary if multiple surgeries are required to achieve anatomic success.  Some reports are 90-95% anatomic success with multiple surgeries.  ESI has a 96% anatomic success after multiple surgeries.  Some patients who did not reach anatomic success voluntarily chose not to pursue more surgery; two patients were diagnosed with cancer, another decided that the vision had always been so poor in the eye that he didn’t want more surgery and another patient was admitted to hospice.

Of the 13 patients who failed primary repair, 5 had proliferative vitreoretinopathy prior to initial repair.  Two patients had a history of failed pneumatic retinopexy performed by other practitioners and two had a concomitant diagnosis of retinoschisis.

One of the most common reasons for a failed retinal detachment repair is the development of proliferative vitreoretinopathy.  In published reports, the incidence of PVR ranges from 8-10%.  ESI has a 6% occurrence of PVR.

Finally, the visual acuity results of patients with a retinal detachment….

If the retina is repaired while the macula is still ‘on’, the likelihood of achieving vision better than 20/40 is 93%.  If the macula was detached but was repaired within 2 days, 100% of those patients had 20/40 vision or better.  If the macula was detached less than a week, 73% of those patients were better than 20/40.  If the macula was detached longer than 1 month, 27% of those patients were 20/40, or better.

So, my take home message was this; time is gold.  Repairing the retinal detachment sooner is helpful.  Ideally, the retina is repaired while the macula is still on.  However, even days matter once the macula is detached.  And even if the retina has been detached longer than a month it is still worth trying to improve the vision, since a good portion of these patients end up with functional vision.

Lastly, complete examination of the contralateral eye including a thorough scleral depressed exam is critical.  A total of 48% of patients had pathology in the contralateral eye.  Retinal detachments occurred in 15% of these patients and 32% had either a retinal tear or lattice in the unaffected eye.

In conclusion, patient education is critical.  The patient needs to be educated about the likelihood of anatomic and visual outcomes with surgical repair of their retinal detachment as well as the risk to their contralateral eye.