Off the Cuff: Unintended Consequences

I was recently reading about the worst air tragedy to involve a single aircraft in the history of U.S. aviation. It occurred in Chicago back in May 1979. After analyzing the evidence, investigators traced the cause of the accident to a mechanic’s dumb idea--using a forklift to remove an engine for servicing rather than following the manual. The result was a fractured engine mount and a horrific accident.

The report started me thinking about unintended consequences of things that we ODs do. Granted, most of us don’t encounter life-and-death consequences as a result of our miscues; still, our actions or lack thereof can result in serious problems for our patients. Some errors are obvious, like forgetting to tell a patient to discontinue a steroid drop when you dismiss them for six months. Others creep up on you, like choosing an unexpectedly ineffective antibiotic to treat a resistant ulcer.

When you really get down to it, the truly scary things are those that we can’t anticipate at all. Imagine a glaucoma drop sending your patients blood chemistry totally out of whack, a lubricant for dry eye blocking the eye’s natural defenses to infection or a lens care product that silently causes the bulk of your patients to discontinue lens wear due to corneal hypoesthesia and subsequent dry eye discomfort.

What protects us against these hidden nightmares is our natural curiosity and our innate desire to share what we’ve learned. We can’t always be perfect nor always be right, but paying attention to what others have discovered and sharing what we have figured out for ourselves helps keep us one step ahead of disaster.

Arthur B. Epstein, OD, FAAO Chief Medical Editor artepstein@optometricphysician.com

Case in Point: Chronic Bilateral Uveitis Leads to Complications

A 31-year-old African-American woman presented for a second opinion regarding treatment of her uveitis. Management at that time included cyclopentolate QD and prednisolone acetate QID for the last year. Her ocular and systemic history was unremarkable.

Upon examination, best-corrected acuities were 20/40 OD and 20/60 OS. External examination was unremarkable, with no afferent defect. Goldmann tonometry measured 32 mmHg OD and 34 mmHg OS. Gonioscopy demonstrated open angles, a flat iris approach and Grade II trabecular pigment OU. The anterior chamber displayed Grade II cell and flare OU, with copious inflammatory cells on the endothelium and anterior lens surface OD. No posterior synechiae were observed. Dilated examination revealed vertical elongation of both optic nerve cups, suggestive of glaucomatous damage.

At the time of presentation, the patient knew that she had uveitis. What she did not realize was that she also had uveitic glaucoma. Subsequent visual field testing revealed blind spot enlargement OD and a superior arcuate defect OS. In cases such as these, it is important to realize that the uveitis is the root cause of the glaucoma; as such, one MUST address the inflammatory aspect of the disease to successfully diminish intraocular pressure (IOP). Strong cycloplegics such as scopolamine or even atropine are indicated, as well as frequent dosing of 1% prednisolone acetate. Virtually any IOP-lowering agent may be used to treat uveitic glaucoma, provided there are no systemic or ocular contraindications. The only notable exceptions include pilocarpine and prostaglandin-type drugs such as Xalatan or Lumigan. Remember that treatment for endogenous uveitis is often a long-term prospect, with patients maintaining therapy for months or years.

It is also important to recognize the need for systemic evaluation in severe, and particularly bilateral, uveitis. Laboratory testing should be ordered or recommended to rule out infectious and/or connective tissue disorders such as tuberculosis, syphilis, sarcoidosis and lupus.

--Case study courtesy of Andrew S. Gurwood, OD, FAAO, Associate Professor, Pennsylvania College of Optometry, Elkins Park, PA.

One hundred thirty-five eyes of 135 patients who had undergone lamellar keratoplasty (LK) were retrospectively analyzed for the occurrence of infectious keratitis following LK. The parameters evaluated were predisposing factors, seasonal variation, indications and type of LK, time interval between LK and infection, site and depth of infection, etiologic organisms, type of treatment, outcome in terms of graft status, secondary surgery, visual acuity and the donor tissue profile.

The incidence of infectious keratitis following LK was 11.11 percent. The most significant predisposing factor was persistent epithelial defect and suture abscesses. Most cases occurred between May and August. Twelve cases developed infection within two weeks of surgery. Seven cases occurred with onlay grafts, six with inlay grafts, and two with large-diameter LK. Cultures of corneal scrapings were positive in 73.3 percent of patients, and the most common isolated organism was coagulase-negative Staphylococcus. Only two eyes responded to medical therapy, and graft sloughing occurred in nine cases. Six eyes underwent penetrating keratoplasty either to salvage the integrity of globe or for visual rehabilitation of cases where infection resulted in corneal opacity. These findings demonstrated that infections after LK may not be amenable to antimicrobial therapy and may necessitate the removal of the graft or a therapeutic penetrating keratoplasty.

SOURCE: Sharma N, Gupta V, Vanathi M, et al. Microbial keratitis following lamellar keratoplasty. Cornea 2004;23(5):472-8.

Corneal Aberrations After AK with LASIK

Twelve patients with high myopic astigmatism (from 3.50D to 6.00D) were evaluated for optical aberrations in the cornea before and after astigmatic keratotomy (AK) combined with laser in situ keratomileusis (LASIK). AK was performed as the first step to reduce astigmatism; after two months, the residual refractive error was corrected with LASIK. Videokeratography measurements were conducted before and after each procedure. Topography maps were used to calculate the wavefront corneal aberrations for a 6.0-mm pupil diameter.

Total, coma-like and spherical-like aberrations increased significantly from preoperatively to post LASIK. AK significantly increased coma-like and spherical-like aberrations. After LASIK, the coma-like aberration was significantly reduced and the spherical-like aberration was significantly increased. It was concluded that AK increased higher-order corneal aberrations, both coma-like and spherical-like, whereas LASIK performed after AK increased the spherical-like aberration and reduced the coma-like aberration.

SOURCE: Montes-Mico R, Munoz G, Albarran-Diego C, et al. Corneal aberrations after astigmatic keratotomy combined with laser in situ keratomileusis. J Cataract Refract Surg 2004;30(7):1418-24.

Corneal Ectasia After Myopic LASIK

This multicenter retrospective review evaluated corneal ectasia after LASIK for myopia without a consistent definition of this condition or a definitive etiology. A Medline search for "LASIK" and "ectasia" yielded 21 relevant articles published before May 2003. A comparison group was selected from a clinic-based sample of successful LASIK patients with 12 months of follow-up after treatment.

Mean time to diagnosis of ectasia after LASIK was 13 months. Residual myopia in the ectasia group was -3.69D and was significantly greater than the comparison group (-0.38D). After surgery, eyes with ectasia had increased corneal toricity (2.87D) with increased oblique astigmatism (1.3D) relative to eyes in the comparison group (0.00D), and a loss of two lines of best spectacle-corrected visual acuity. Thirty-five percent of reported cases resulted in subsequent corneal transplantation.

Preoperative characteristics of corneal ectasia include worse visual acuity, less corneal thickness, greater residual myopia and greater corneal toricity than nonectatic eyes. Treatment factors associated with corneal ectasia after LASIK are greater stromal ablation and less residual stromal bed thickness. Postoperative characteristics of corneal ectasia are myopic refractive error with increased astigmatism, worse spectacle-corrected visual acuity, increased corneal toricity with topographic abnormality and progressive corneal thinning.

SOURCE: Twa MD, Nichols JJ, Joslin CE, et al. Characteristics of corneal ectasia after LASIK for myopia. Cornea 2004;23(5):447-57.

NEWS & NOTES

	INTACS APPROVED FOR TREATMENT OF KERATOCONUS. Addition Technology, Inc., has received approval from the FDA for a Humanitarian Device Exemption (HDE) to market Intacs inserts for the treatment of keratoconus. The approval is based on the device's safety record, the relatively low number of U.S. patients affected by the disease and the fact that no other treatment options exist for these patients other than an invasive corneal transplant procedure. The approval allows Intacs inserts to be marketed for the reduction or elimination of myopia and astigmatism in patients with keratoconus, where functional vision is no longer achievable with their contact lenses or eyeglasses. In addition, Intacs inserts may defer the need for a corneal transplant for some keratoconus patients. The approval will also allow the company to educate keratoconus patients about the potential advantages of Intacs inserts and is expected to help facilitate expanded health insurance coverage for the procedure in the United States. For more information, go to www.getintacs.com or call (847) 297-8419.
	NATIONAL OPTOMETRY HALL OF FAME ANNOUNCES 2004 INDUCTEES. The National Optometry Hall of Fame will induct six new members during ceremonies on October 14, 2004, at the EastWest Eye Conference in Cleveland. This year's inductees are: Anthony J. Adams, OD, PhD, Dean Emeritus at the University of California, Berkeley, recognized for his research studies in human neurophysiology, myopia, color vision and diabetes; Jimmy Bartlett, OD, DOS, ScD, prominent educator and researcher in ophthalmic pharmacology; Joan Exford, OD, first woman president of the American Academy of Optometry; and Melvin Wolfberg, OD, who served as president of the American Optometric Association, the American Academy of Optometry and the Pennsylvania College of Optometry. Frank Brazelton, OD, will be inducted posthumously for his legacy of emphasizing goals and objectives, operations and activities, and logistics and support, a model of "strategic planning."
	ALLERGAN RECEIVES APPROVABLE LETTER FOR BIMATOPROST-TIMOLOL FORMULATION. The FDA has issued an approvable letter for Allergan's Lumigan timolol combination product for glaucoma (bimatoprost 0.03 percent/timolol 0.05 percent ophthalmic solution). An approvable letter sets out the conditions that a company must meet to obtain FDA final marketing approval. A spokesperson for Allergan says that the FDA's response necessitates additional clinical investigation, and that it has already begun an additional clinical study that it anticipates completing by the end of 2004.
	CYNACON/OCUSOFT INTRODUCES DIAGNOSTIC LENS SET FOR POST-SURGICAL EYES. Cynacon/OcuSoft has introduced TeKnique, a PMMA diagnostic lens set designed to aid in determining the estimated true corneal power of an eye that has undergone corneal refractive surgery. The TeKnique set includes six lenses in base curves ranging from 30 to 42 diopters, all visibly tinted; a hard contact lens cleaning solution; a lens inserter/remover and lint-free contact lens towelettes. For more information, go to www.eyelab.com or call (800) 233-5469.

 

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