PION after lumbar spine injury: author reply

Letters to the Editor construed as negligent in the context of what the authors clearly indicate as the current patterns of care. I am concerned that before the urgently needed randomized controlled clinical trials suggested by the authors, one of us could fall prey to a hungry lawyer representing a patient with a suboptimal outcome. I look to the American Academy of Ophthalmology for guidance on this issue, and I thank the authors and editors for presenting the important report. ERIC L. SINGMAN, MD, PHD Lancaster, Pennsylvania Reference 1. Stanford MR, See SE, Jones LV, Gilbert RE. Antibiotics for toxoplasmic retinochoroiditis: an evidence-based systematic review. Ophthalmology 2003;110:926 –31.

Author reply Dear Editor: The Quality of Care Secretariat of the American Academy of Ophthalmology has developed a mechanism to address new evidence-based knowledge and technology that impact patient care. Unfortunately, due to the scarcity of randomized clinical trial information, most of our clinical recommendations are based on consensus opinion and not on evidence. The Preferred Practice Pattern Benchmarks distill current evidence, where it exists, and consensus-based information into process of care recommendations that are clinically relevant. These recommendations undergo an intensive review process and, by their very nature, are often accepted as standard of care within the profession. New information in the literature that has not yet been incorporated into these documents may be reported by the Academy in their Rapid Clinical Responses, but has not yet been vetted through a consensus process. The law states that the standard of care in clinical situations may be based on what a significant minority of reasonable physicians would do in a similar situation. In this case, citing the Stanford et al article would be helpful in fending off a lawsuit or, if it were in fact filed, defending against it. Patients may file a lawsuit against a physician for legitimate reasons or misguided ones. That standard textbooks such as Duane’s, the Basic and Clinical Science Course, and the Wills manual weigh more on a scale than a single evidence-based article that has been recently published might persuade some jurors, but if an expert explains things clearly, an attentive jury should be able to understand the issues and not be swayed by showmanship. My advice to an ophthalmologist who sees patients where the choice of therapy may be controversial is to explain to the patient and document in the medical record the rationale for recommending a specific treatment if it has not yet become mainstream. Dr Singman is correct that we live in a difficult and challenging medical–legal environment. Physicians living in Pennsylvania are acutely aware of this environment. Doctors who are not familiar with the pros and cons of a recommended therapy and treat patients in a vacuum are more likely susceptible to incurring a lawsuit; those who

know more and document better will be sued less often and, when they are, are more likely to prevail. RICHARD L. ABBOTT, MD Secretary for Quality of Care, American Academy of Ophthalmology Chair, Underwriting Committee, and Member, Board of Directors, Ophthalmic Mutual Insurance Company

PION after Lumbar Spine Injury Dear Editor: We read with great interest the article by Murphy regarding the case of posterior ischemic optic neuropathy after lumbar surgery.1 There was some uncertainty regarding the diagnosis versus functional visual loss. We noticed that an electroretinogram was done, which was normal. We wish to point out that a visual evoked potential could have provided objective evidence of visual acuity. A recent reference2 concluded that the pattern visual evoked potential is a useful test offering a measure of objectivity when the diagnosis of functional visual loss is under consideration. ABDEL-RAHMAN EL-BASH, MD MARCUS EDELSTEIN, MD, PHD EDWARD SMITH, MD Brooklyn, New York References 1. Murphy M. Bilateral posterior ischemic optic neuropathy after lumbar spine surgery. Ophthalmology 2003;110:1454 –7. 2. Xu S, Meyer D, Yoser S, et al. Pattern visual evoked potential in the diagnosis of functional visual loss. Ophthalmology 2001; 108:76 – 80, discussion 80 –1.

Author reply Dear Editor: I thank Drs El-Bash et al for their comments. They write that there was uncertainty regarding the diagnosis of functional visual loss in this case. In fact, as pointed out in the article, the patient presented for a second opinion regarding a diagnosis of functional visual loss made by a previous examiner. Given what I felt was the possibility that the patient had indeed suffered a postoperative posterior ischemic optic neuropathy, and the fact that functional visual loss should be considered a diagnosis of exclusion, I obtained an electroretinogram to ensure that the retina was not the culprit and to rule out the possibility of a central retinal artery occlusion. I explained to the patient that if she had indeed suffered a postoperative posterior ischemic optic neuropathy, I expected her optic nerves to become pale over the next month or so, which is what was then observed on follow-up. A normal electroretinogram and the clinical examination in this case confirmed an optic neuropathy, obviating the need for further testing such as a pattern visual evoked potential. I agree that in cases in which functional visual loss is still suspected, a pattern visual evoked potential may be helpful in documenting a better visual potential than that claimed by the patient. A visual evoked potential in my patient would have been abnormal but was unnecessary given confirmation of the diagnosis of posterior ische-

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Ophthalmology Volume 111, Number 3, March 2004 mic optic neuropathy by the examination and electroretinogram findings.

to proceed to step 2 and the assumption that normal looking equals normal function.

MARJORIE A. MURPHY, MD Providence, Rhode Island

ANDREW LEE, MD Iowa City, Iowa

Dear Editor: Murphy reported a case of bilateral posterior ischemic optic neuropathy (ION) after lumbar spine surgery.1 Visual loss after nonocular surgical procedures is increasingly being recognized and reported. The usual cause for visual loss in these cases is ION, but some are due to central retinal artery or ophthalmic artery occlusion. In Murphy’s case, electroretinography was performed and the electroretinogram was normal; this essentially eliminates retinal artery occlusion from the differential diagnosis. This is important for medicolegal as well as medical reasons, because direct compression of the globe on the surgical headrest during proneposition spine procedures can produce a central retinal artery occlusion, a preventable injury. Although a number of surgical factors (e.g., intraoperative hypotension, anemia, duration of surgery, fluid balance, facial edema) and patient factors (e.g., hypertension, diabetes, smoking, atherosclerosis, obesity) have been associated with ION, it should be emphasized that none has been proven to be causal.2– 4 As Dr Murphy points out in her discussion, the incidence of postsurgical ION is very low (1 in 60 000), and this suggests that a synergistic confluence of different surgical and patient factors is required for ION in this setting. The prevention and treatment of postoperative visual loss remain elusive. For example, even if hypotension is the main culprit, then avoiding controlled intraoperative hypotension might lead to further blood loss and worsen an anemia or lead to a bloodier surgical field. Likewise, even if blood loss is the main cause, prophylactic measures such as blood transfusion would potentially expose thousands of patients to the unnecessary risk of transfusion error or bloodborne infectious diseases. These transfusion risks may occur in as many as 1 in 3000 to 1 in 6000 patients. As in the patient described by Murphy, there are often no preoperative factors that can identify the patient risk. Patients undergoing identical surgical procedures with identical parameters of surgical time, blood pressure, blood loss, fluid balance, and prone positioning usually do not develop ION. Finally, even if the problem of ION is recognized, potential treatments (e.g., blood transfusion, fluid balance, blood pressure control, hyperbaric oxygen) are unlikely to reverse the visual loss once the event has already occurred. Obviously, further study is needed to answer the critical questions regarding pathogenesis and causality. Dr Murphy’s case emphasizes that the problem of postoperative ION can be difficult to evaluate, and adding the incorrect diagnosis of nonorganic visual loss to the mix only adds fuel to the medicolegal fire. It also reinforces the clinical rule of thumb that the diagnosis of nonorganic visual loss requires 2 steps: (1) documentation of a normal structural eye examination and (2) proof that the patients sees better than his or her claimed level of vision. In my experience, the most common error in the misdiagnosis of nonorganic visual loss is failure

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References 1. Murphy MA. Bilateral posterior ischemic optic neuropathy after lumbar spine surgery. Ophthalmology 2003;110:1454 –7. 2. Lee LA. Postoperative visual loss data gathered and analyzed. ASA Newsl 2000;64(9):25–7. 3. Myers MA, Hamilton SR, Bogosian AJ, et al. Visual loss as a complication of spine surgery. A review of 37 cases. Spine 1997;22:1325–9. 4. Roth S, Roizen M. Optic nerve injury: role of the anesthesiologist? Anesth Analg 1996;82:426 –9.

Author reply Dear Editor: I appreciate Dr Lee’s interest in my article and completely agree with his comments, which echo those discussed in the article. The fact that true organic visual loss may present with an initially normal eye examination and normal neuroimaging was a key point of the discussion. As was emphasized, functional visual loss should be considered a diagnosis of exclusion—in other words, first consider why the patient cannot see before assuming that he can. I agree that the prevention and treatment of postoperative visual loss remain elusive and hope that, as more cases are documented, further study will help to clarify this fortunately uncommon entity. MARJORIE A. MURPHY, MD Providence, Rhode Island

Videokeratoscopic Indices for Keratitis Sicca Dear Editor: We read the article by Sade de Paiva et al1 with great interest. The authors correlate the regularity indices of videokeratoscopy with more conventional measures of dry eye syndrome in both control subjects and patients with reports of ocular irritation. The authors conclude that, due to a strong correlation between the surface regularity index (SRI) on videokeratoscopy and corneal fluorescein staining, corneal surface irregularity is a basic feature of keratoconjunctivitis sicca that could be used as a marker of disease severity due to its objectivity and ease of use. We commend the authors’ attempts to find a standardized objective method for assessing the severity of keratoconjunctivitis sicca, due to limitations of current conventional subjective techniques. However, the lack of an appropriately sized and matched control group in their study design is a major shortcoming that brings into question their conclusion that increased corneal surface irregularity is associated with dry eye, regardless of age. The effect of age as a confounding variable in the relationship between SRI and fluorescein staining has not been fully dealt with in this study. Corneal irregularity is known to increase with age.2 Sade de Paiva et al concede that one possibility for the signifi-