Craig Thomas, O.D.

Over eight years ago, my friend John Coble, O.D. talked to me about purchasing a specular microscope. He had just bought one a few months earlier, and his initial results were very positive. Because Dr. Coble is my friend, he was now calling to recommend that I buy one too. When I asked about specific benefits, he said that integrating specular microscopy into his practice was benefiting his patients clinically and growing his practice financially.

Historical Overview

When Dr. Coble first called, I knew very little about specular microscopy or specular microscopes. When we were in optometry school 25 years ago, the technology was just being developed for clinical use.

Specular microscopes are used to evaluate the structure and function of the corneal endothelium. Prior to their development, the slit-lamp biomicroscope was the only instrument that could be used to perform this function.

The first reported evaluation of the corneal endothelium was by Vogt in 1918. He visualized the endothelial mosaic with specular reflection while performing slit-lamp biomicroscopy. For 50 years, this technique was standard-of-care when evaluating the corneal endothelium.

In 1968, David Maurice developed a microscope to visualize the corneal endothelium and introduced the term specular microscope. By 1975, Ronald Laing had modified the original design to produce a more clinically useful instrument. That same year, Bourne and Kaufman modified the design with a flash attachment and the modern non-contact specular microscope was finally ready for clinical use.

KONAN XL™ Specular Microscope

Getting Started

Initially, I gave myself a refresher course in corneal anatomy and physiology. I found and read most of the current information on the corneal endothelium. Using this new knowledge, I began integrating specular microscopy into my practice.

Fortunately, we did not experience any patient flow problems in the beginning. After a few days, my staff could easily complete the test in 5-10 minutes. Clinically, I began to visualize and analyze the structure of the corneal endothelium as never before.

I quickly learned how to determine normal endothelial structure vs. abnormal endothelial structure. Eventually, as my confidence and experienced increased, I began to make clinical decisions based on the test results.

Practice Benefits

As the years went by, I became a strong proponent of incorporating specular microscopy into optometric practice. It has been good for me, good for my patients, and good for my practice.

First, acquiring and utilizing this technology has made me a better doctor. To obtain the maximum benefit of owning a specular microscope – I had to learn new information. Although I always stay up-to-date on technology and read several optometric journals each month, my clinical knowledge of corneal endothelial disease was fairly low compared to now. I wanted to understand what I was seeing, and I didn’t want to learn how to take care of my patients from a sales representative.

Second, acquiring and utilizing this technology has been better for my patients. Although there are only a few primary eye diseases that involve the corneal endothelium, moderate to advanced endothelial disease can result in blurred vision, fluctuating vision, or permanent visual impairment. Utilization of specular microscopy has allowed me to make an earlier diagnosis of these conditions. Since functional changes often follow structural changes in the human body, an earlier diagnosis involving structural change allows me to treat my patients before they report functional changes such as blurred or fluctuating vision.

The following case reports will give you some ideas as to how specular microscopy can be utilized in your practice.

Case One: Pre-Operative Risk Assessment for Ocular Surgery

History

A 70-year old white female presented to the office with complaints of reduced vision. Her distance visual acuity is 20/60 in the right eye and 20/60 in the left with her habitual spectacle prescription. The History of Present Illness describes a subjective decrease in vision over the past year. Ocular history is significant for cataract surgery in the right eye two years earlier. The patient wanted to know if new eyeglasses and/or cataract surgery on the left eye would help her to improve her vision.

Examination

A comprehensive eye examination revealed normal clinical findings in the following areas: (1) IOPs, (2) pupils, (3) gross visual fields, (4) basic sensorimotor examination, (5) external examination, (6) adnexal examination, and (7) ophthalmoscopic examination.

Diagnostic Tests

To continue the care process and determine a more substantiated physical diagnosis, I ordered the following diagnostic tests: (1) Refraction, (2) Threshold Visual Field, and (3) Specular Endothelial Microscopy.

1. Refraction: no improvement in acuity with a new optical prescription
2. Threshold Visual Field: no clinically significant defects
3. Specular Endothelial Microscopy: low cell count in the left eye

Discussion

Modern, full-scope optometric practice includes surgical co-management with ophthalmologists. My practice produces dozens of surgical referrals each year, and optometrists like me need to be aware of informed consent issues with patients that are referred to ophthalmologists for cataract surgery.

As part of my pre-operative evaluation, I review any potential risks that may be associated with the proposed surgery. This discussion, also known as the PARQ conference (procedure, alternatives, risks, questions), serves to document that the patient wishes to proceed with the surgery and is essential for obtaining the patient’s informed consent.

According to Medicare’s National Coverage Determination for Endothelial Cell Photography, one of the clinical indications for specular microscopy is that it can be used pre-operatively as a “predictor of success”for ocular surgery.

The information produced by specular microscopy allows the optometrist to assess the Endothelial Functional Reserve of the cornea prior to the referral for surgery. This functional assessment is accomplished by estimating the amount of corneal endothelial cell loss after cataract surgery and then predicting the ability of the endothelium to withstand the iatrogenic damage and continue to function normally.

We know that surgical trauma during a normal cataract extraction results in a 4-10% loss of endothelial cells. If a patient’s cell count is low prior to cataract surgery, the endothelium may not have enough cells post-operatively to maintain normal function. This determination of a Functional Reserve Ability is made by comparing a cornea’s endothelial cell count to an age-matched normal range. When the cell count is high, the cornea may be able to withstand more surgical trauma because it retains enough endothelial cells to replace the cells that will be damaged during the procedure. If the cell count is low, the cornea may be unable to sustain as much iatrogenic damage. In these cases with a low cell count and a reduced Functional Reserve Ability, the cornea may take longer to heal and may have a greater chance of decompensating.

This patient’s cell count was less than 1000 mm2 in the left eye. Pre-operative cell counts below 1000 mm2 indicate a low Endothelial Functional Reserve and a high risk of post-operative corneal edema. Since this patient had reduced acuity and corneal edema in the right eye after her initial cataract surgery, I predicted that the same thing would happen if the patient had cataract surgery in the left eye now. For this reason, I recommended that the patient NOT proceed with cataract surgery at this time since I thought the chance of a significant improvement in visual acuity post-operatively was low and the risk of post-operative complications was high.

In this patient, my medical decision-making was clearly affected by having a specular microscope in my practice.

Case Two: Diagnosis and Treatment of Fuch’s Endothelial Dystrophy

History

A 53-year old black female presented to the office with complaints of reduced vision. Her uncorrected distance visual acuity was 20/40 in the right eye and 20/50 in the left eye. The History of Present Illness describes a subjective decrease in vision over the past year. The only eyeglasses used were non-prescription reading glasses. The most recent eye examination was three years earlier. The patient wanted to know if new eyeglasses would help her to improve her vision.

Examination

A comprehensive eye examination revealed normal clinical findings in the following areas: (1) IOPs, (2) pupils, (3) gross visual fields, (4) basic sensorimotor examination, (5) external examination, (6) adnexal examination, and (7) ophthalmoscopic examination.

Diagnostic Tests

To continue the care process and determine a more substantiated physical diagnosis, I ordered the following diagnosic tests: (1) Refraction, (2) Specular Endothelial Microscopy.

1. Refraction: no improvement in acuity with a new optical prescription
2. Specular Endothelial Microscopy: low cell count, dense guttata, abnormal endothelial cell morphology, increased corneal thickness

Discussion

This patient has Fuch’s endothelial dystrophy. It is the most common of the primary corneal endotheliopathies and it affects 4% of all people over 40 years of age.

The disease is characterized by a loss of endothelial cell structure and function. Biomicroscopy reveals loss of corneal transparency, corneal guttata and pigment granules on the endothelium. Specular photomicrographs reveal a low endothelial cell count, dense guttata formation, and a change in the structural formation of the normal endothelial mosaic. In advanced disease, the normal endothelial mosaic is altered so that specular microscopy may not be possible.

This patient’s disease was classified as moderate in its presentation. Since refraction did not produce an improvement in visual acuity, this patient’s best treatment option is topical sodium chloride 5% ophthalmic solution. This hypertonic solution attempts to improve visual acuity by reducing corneal edema secondary to the endothelial dysfunction.

Pharmacological therapy is recommended until the corneal thickness approaches 650 microns or the visual acuity drops to 20/70 or worse. In these advanced presentations, a full thickness corneal transplant or an endothelial transplant may be the better option.

In this patient, the diagnosis and treatment of her Fuch’s dystrophy would have been more difficult without the advantage of having a specular microscope in my practice.

Case Three: Diagnosis and Treatment of Contact Lens Endotheliopathy

History

A 35-year old black female presented to the office with complaints of reduced comfort and vision while wearing her contact lenses. Her distance visual acuity with her habitual contact lens prescription was 20/25 in each eye. The History of Present Illness described a subjective decrease in vision over the past six months combined with a corresponding decrease in contact lens wearing time secondary to decreased comfort. Ocular history is significant for full-time soft contact lens wear for the past 20 years.

The patient was currently wearing a traditional soft lens (Soflens 66 Toric by Bausch & Lomb). Although she had successfully worn these lenses for several years, they no longer seemed to provide acceptable performance. The patient wanted to know if new contact lenses would improve her comfort and vision and increase her wearing time.

Examination

A comprehensive eye examination revealed normal clinical findings in the following areas: (1) IOPs, (2) pupils, (3) gross visual fields, (4) basic sensorimotor examination, (5) external examination, (6) adnexal examination, (7) external examination with biomicroscopy, and (7) ophthalmoscopic examination.

Diagnostic Tests

To continue the care process and determine a more substantiated physical diagnosis, I ordered the following diagnosic tests: (1) Refraction, (2) Corneal Topography, (3) Specular Endothelial Microscopy.

1. Refraction: no improvement in acuity with a new optical prescription
2. Corneal Topography: no corneal shape anomalies or irregular astigmatism
3. Specular Endothelial Microscopy: polymegathism, pleomorphism, and slightly increased corneal thickness

Discussion

Polymegathism is an early clinical sign of endothelial disease. It is characterized by an abnormal variation in the size of the endothelial cells and it reflects an abnormal rate of endothelial wound repair. The degree of polymegathism is represented by the Coefficient of Variation (CV) and values above 40 are abnormal.

Pleomorphism is another early clinical sign of endothelial disease. It is characterized by an abnormal variation in the shape of the endothelial cells and it is present when the percentage of hexagonal cells in the endothelium falls below 50%. The degree of pleomorphism is represented by the 6A measurement on the statistical analysis printout and its presence indicates a condition of structural instability in the corneal endothelium.

Endothelial cells that show morphological changes such as polymegathism and pleomorphism are considered to be under physiologic stress and are therefore abnormal. Long-term contact lens wear can produce these morphological changes (contact lens-related endotheliopathy) and result in corneal edema secondary to wearing contact lenses. Abnormal clinical symptoms suggesting corneal edema include blurred vision, fluctuating vision, halos around lights, photophobia, foreign body sensations, and contact lens intolerance.

In this patient, the cornea appeared to be normal after a biomicroscopic examination. In addition, specular microscopy revealed a normal endothelial cell count. Studies reveal that both of these indicators are usually normal in contact lens-related endotheliopathy. The quantitative analysis indicating abnormal endothelial cell morphology was the key clinical finding in this case. The findings of polymegathism and pleomorphism in a 20-year contact lens wearer combined with the patient’s history of recent contact lens-related problems helped to determine the final diagnosis of contact lens-related endotheliopathy in this patient.

Studies indicate that some degree of recovery towards normal endothelial morphology is possible if contact lens wear is discontinued and/or the patient changes to a contact lens with a significantly higher degree of oxygen transmission. In this patient, the initial treatment option was to prescribe a contact lens with a higher Dk value (Acuvue Oasys for Astigmatism by Vistakon). The goal of the treatment is to improve the patient’s ocular health, visual acuity, physical comfort, and contact lens wearing time.

This case demonstrates how incorporating specular microscopy into your contact lens practice can enhance your diagnostic abilities and affect your medical decision-making.

SUMMARY

I could give many examples about the clinical benefits of specular microscopy – but the benefits to patient care are easily seen in the cases presented. This technology allows you to do a better job of taking care of your patients. There is, however, one more significant benefit. Adding specular microscopy to your practice allows your practice to grow financially.

As we all know, most types of advanced technology are expensive. Many times, optometrists believe that they cannot afford to buy expensive instruments – especially those that they are not familiar with. Trust me – this instrument is different.

Our practice averages about two specular microscopy tests per day. With that type of utilization, I was able to pay for the instrument in less than one year. That means that in the past seven years, all fees generated by specular microscopy have been profit. From a financial growth position, there is nothing that has had a more significant effect on my practice’s bottom line than specular microscopy!

Since optometrists are my friends, I want to make the same recommendation to you that Dr. Coble made to me. After he convinced me to add this technology to my practice, I had one final question: “what did you buy?” He said that he bought a KONAN. When I asked why, he said it was the only one he knew about, so he went with the “name brand”.

I believe that eight years later, KONAN is still the “name brand” in specular microscopes. It’s the kind that I have, and it’s the kind I recommend. They are easy to use and very reliable. Indeed, I have not had a single service call or mechanical breakdown in eight years. I could not be happier with my decision. It has been good for me, good for my patients, and good for my practice.

Billing & Coding of Specular Microscopy

The approved diagnosis codes, documentation requirements, coding guidelines and utilization guidelines for specular microscopy vary between medical insurance companies.

For patients using Medicare insurance, there is a National Coverage Determination (NCD 80.8) on “Endothelial Cell Photography”that applies to all specular microscopy claims billed to Medicare. Remember, National Coverage Determinations list the clinical indications when the procedure is covered and define the parameters that make the test medically necessary.

This policy states that “Endothelial Cell Photography”is a covered procedure under Medicare when reasonable and necessary for patients who meet one or more of the following criteria:

1. Have slit lamp evidence of an endothelial dystrophy such as corneal guttata;
2. Have slit lamp evidence of other endothelial dystrophies such as posterior polymorphous dystrophy or iridocorneal endothelial syndrome;
3. Have slit lamp evidence of corneal edema;
4. Have had previous intraocular surgery and require cataract surgery;
5. Are about to undergo secondary lens implantation;
6. Are about to undergo a surgical procedure associated with a higher risk to the corneal endothelium; or,
7. Are about to be fitted with extended wear contact lenses after intraocular surgery.

Also, for patients using Medicare insurance, the Medicare Benefit Policy Manualhas specific documentation and coding guidelines for performing specular microscopy as a part of a “Presurgery Evaluation” for cataract surgery. These documentation and coding guidelines fall under the category of “Use of Visual Tests Prior to Cataract Surgery” and they state the following:

"Cataract surgery with an intraocular lens (IOL) implant is a high volume Medicare procedure. Along with the surgery, a substantial number of preoperative tests are available to the surgeon. In most cases, a comprehensive eye examination and a single scan to determine the appropriate pseudophakic power of the IOL are sufficient. In most cases involving simple cataract, a diagnostic ultrasound A-scan is used. For patients with a dense cataract, an ultrasound B-scan may be used.

Accordingly, where the only diagnosis is cataract(s), Medicare does not routinely cover testing other than one comprehensive eye examination and an A-scan or, if medically justified, a B-scan. Claims for additional tests are denied as not reasonable and necessary unless there is an additional diagnosis and the medical need for the test is fully documented."

What this means in clinical practice is that if the only diagnosis is cataracts, endothelial cell photography is covered as part of the presurgical eye examination and not in addition to it. In other words, to bill specular microscopy at the same time that you are performing a presurgical eye examination for cataract surgery, the medical record must document at least one of the coverage criteria listed above and the procedure must be reported with a diagnosis code other than a simple cataract.

About the Author:
In practice for the past twenty-five years, Craig Thomas, O.D. is in a partnership with Michael Burton, O.D. in Dallas, Texas. The two optometrists examine a combined total of 60 to 70 patients per day.