Evolving Standards of Care
Is meeting the existing standard enough in glaucoma treatment?
By Jerome Sherman, O.D., F.A.A.O., Jake Yakubov, B.S. and Melissa Ghoo, O.D.

A 50-year-old black judge presented for a second opinion about her vision status and options following laser and surgical intervention for her previously diagnosed primary open angle glaucoma (POAG). She reported that her mother, one aunt and maternal grandmother had become legally blind from glaucoma. The patient had been followed carefully during her 30s and was first diagnosed with POAG and treated in both eyes at age 41.

Events that led to this visit

About 1 year before this visit, the judge underwent two successive argon laser trabeculoplasties (ALTs) in her left eye because of progressive field loss, intraocular pressures (IOPs) in the low 20s, and advanced and progressive nerve fiber layer loss as depicted on GDx serial analysis.

Her general health was compromised by asthma and seas-onal allergies. She'd developed an allergic response to brimonidine (Alphagan) and latanoprost (Xalatan) and was then taking only dorzolamide (Trusopt) b.i.d. OU. No one ever pre-scribed beta blockers or miotics.

Six months after the ALTs, which failed to reduce her IOPs to lower than 20 mm Hg, the judge had a standard filtering procedure in the left eye. Her surgeon had told her that the surgical trabeculectomy was essential because the maximum number of laser procedures had already been provided.

Her IOPs following the surgical trabeculectomies were in the 0mmHg to 2mmHg range. Her exam revealed a flat chamber, choroidal detachments and eventually, cystoid macular edema. At this point, she was also taking homatropine 5% b.i.d. and loteprednol (Alrex) t.i.d. in the left eye and no glaucoma medications because of the low IOPs.

Back to the present

The judge had surfed the Internet recently and now had questions about two relatively new procedures for glaucoma that she had uncovered: Selective laser trabeculoplasty (SLT) and Aqua Flow. The clinician to whom she presented for a second opinion had recently lectured on both procedures and hence was in a good position to comment.

Second opinion findings

The judge's best-corrected visual acuity at the second opinion was 20/20 OD and a distorted 20/60 OS. The external exam was unremarkable OD but showed a large bleb superiorly OS. Goldmann IOPs were 20 mm Hg OD and 02 OS mm Hg.

Amsler grid was normal in the right eye, but the judge couldn't see any straight lines in the center of the left field. Automated threshold fields, performed a month earlier, revealed large inferior arcuate scotomas with nasal steps in both eyes, and the mean sensitivity was reduced 10 decibels OD and 12 decibels OS.

The judge was particularly interested in the comparisons between ALT and SLT and between standard filtering procedures and the new Aqua Flow. The second doctor briefly discussed some of the differences between the procedures but had no time to go into detail. As the judge was leaving his office, she asked one last question: whether ALT and filtering procedures were considered the standard of care. The doctor replied "Yes" about both procedures.

It's unclear at this time whether the judge intends to file malpractice allegations against the surgeon. She hasn't yet returned for additional care, but she expressed interest in an SLT for her right eye.

Meeting the standard

Based on the information available to date, it appears that the doctors who treated the judge for about a decade met the standard of care. They diagnosed and treated her condition medically, but because of her asthma and allergies to several medications, they recommended and performed ALT.

When the combination of two ALTs in the left eye and the glaucoma medications failed to attain the target pressure, a filtering procedure was recommended and later performed. Flat chambers, low IOPs, choroidal detachments and eventual macular edema are known complications of a standard surgical trabeculectomy. The vast majority of eye clinicians would've followed the same path and no one could've predicted with any certainty the unfortunate outcome.

Malpractice cases are generally analyzed according to a simple analogy: Would a like practitioner under a like circumstance have done the same? If yes, then it's generally assumed that the doctors met the standard of care and are thus not culpable for malpractice.

Going beyond the standard

Although meeting the standard of care is generally considered adequate, courts have sometimes ruled that meeting the existing standard isn't enough. It's likely that the judge in this case was aware of this.

The following are two hallmark cases in which meeting the standard didn't protect the defendants from unfavorable court verdicts.

Case #1. About 3 decades ago in Helling vs. Carey, an M.D. was found culpable for malpractice because a woman who was under his care from the time she was 23 years old until she was 33 lost vision because of undetected glaucoma. Experts testified at the time that the standard of care was to perform eye pressure measurements on patients over the age of 35.

Because the doctor did diagnose the glaucoma when the patient was 33, he met the existing standard. Regardless, the judge instructed the jury to find for the defendant if a simple test, which could've prevented the blindness, was available to the doctor.

The plaintiff's attorney easily demonstrated that such a test was indeed available. This case became the precedent for performing IOPs on virtually all patients -- even those under the age of 35.

Case #2. In Keir vs. the United States, an O.D. in the military failed to dilate the eye and use a binocular indirect ophthalmoscope on 4-year-old Karen Keir, who was essentially asymptomatic and had equal and normal visual acuity.

Less than 1 year later, a large retinoblastoma was diagnosed in one eye. A Federal Appellate court ruled that the patient deserved a dilated fundus exam with the use of a binocular indirect ophthalmoscope. In effect, this court ruling changed the standard and became the often-quoted precedent for the requirement to dilate every patient, regardless of age and presenting symptoms.

In the case of the family court judge with glaucoma, could one argue successfully that the doctor failed to choose the best laser procedure initially and when that failed, he again failed to choose the best surgical procedure?

I believe the answer to both queries is yes and that a persuasive attorney could probably convince a jury that the judge deserved the best available procedures. Because you can repeat SLTs, you could hypothesize that more likely than not, a filtering procedure may have been unnecessary.

It's important to keep in mind that the burden of proof in civil proceedings such as malpractice cases is only "more probable than not" and that the much higher standard used in criminal cases of "beyond a reasonable doubt" need never apply.

ALTs vs. SLTs

Although doctors probably presently perform 100 ALTs in the United States for every SLT, a review of the recent literature clearly and definitively demonstrates myriad advantages of SLT over ALT. Similarly, use of the Aqua Flow device for filtering surgery represents well less than 1% of all surgical procedures, but it too appears superior.

* Argon laser trabeculectomies (ALT) date back to the early 1980s, when they became the standard method of treatment for medically uncontrolled open angle glaucoma. It's presently well known that ALT causes coagulation damage to the trabecular meshwork (TM), the tissue critical for long-term pressure reduction. The tissue damage caused by the Argon laser potentially limits the possibility of retreatment after 360 degrees of laser treatment.

During an ALT procedure, an Argon laser (_ = 488-514) 50 µm in diameter is applied directly between the pigmented and non-pigmented TM with approxi-mately 50 adjacent, but non- overlapping spots per 180 degrees of the TM.

Two widely accepted theories exist as to how the procedure works. The "Mechanical Theory" states that ALT coagulation damage leads to collagen shrinkage and scarring of the tissue. The resultant tightening of the meshwork in the area immediately surrounding the burn reopens the adjacent untreated intertrabecular spaces.

Based on the "Cellular Theory," coagulative necrosis induced by the laser causes a migration of macrophages to phagocytose debris and thereby clear the clogged meshwork.

* Selective laser trabeculo-plasty (SLT). In 1995, SLT was introduced into the market. This procedure uses a Q-switched, frequency-doubled 532 nm laser with a wider spot size compared to that of ALT (400 µm). Tissue culture experiments have demonstrated that the low power and short duration of this laser selectively target pigmented TM cells.

The laser's careful selection spares adjacent cells and tissues from collateral thermal damage and can thus preserve the architecture and integrity of the TM.

Study results

A recent study assessing the effects of the two laser procedures on autopsied eyes, half of which underwent ALT and the other half SLT, demonstrated that the morphological effects of ALT were far more severe than those of SLT. The TMs exposed to ALT revealed crater formation in the uveal mesh-work between the pigmented and the non-pigmented TM.

Additionally, coagulative damage appeared at the base and along the edge of craters with disruption of collagen beams, fibrinous exudates and lysis of endothelial cells, leaving nuclear as well as cytoplasmic debris. Schlemm's canal was also significantly damaged.

SLT, however, showed little or no damage of the TM. No evidence of coagulated or disrupted corneoscleral or uveal trabecular beam structure could be detected.

The minimal effect that SLT had on the lased tissue was cracked intracytoplasmic pigment granules and disrupted trabecular endothelial cells. In general, most of the studies comparing ALT with SLT have revealed that both reduce IOPs to similar values.

Your best protection

O.D.s who treat glaucoma patients owe it to their patients and to themselves to be current with all diagnostic and therapeutic approaches, including laser procedures and surgery. Referring for a procedure that's arguably not the best for the patient could lead to malpractice allegations.

Going beyond the standard and discussing the risks and benefits of each available procedure is your best bet.

Note: The above case is based on fact, but several aspects have been modified to shield the identities of those involved. Curiously, several other inquiries have been made with regard to similar circumstances in other alleged cases of malpractice, which address the same issues discussed above.

If additional studies confirm the findings presented in the references, it's quite possible that the standard of care might change in the not-too-distant future.

Dr. Sherman practices at the Eye Institute and Laser Center in Manhattan and is a distinguished teaching professor at the State University of New York College of Optometry.

MALPRACTICE CASES ARE GENERALLY ANALYZED ACCORDING TO A SIMPLE ANALOGY: WOULD A LIKE PRACTITIONER UNDER A LIKE CIRCUMSTANCE HAVE DONE THE SAME THING?