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Up Front | May 2002

Refractive Challenge

Is This a Refractive Surgery Candidate?

A 43-year-old white female presented for refractive surgery evaluation. She was healthy, not taking any medications, and had a 30-year history of wearing contact lenses. The patient had initially been fitted with rigid contact lenses at age 13, and had worn these for approximately 10 years. Since that time, she has worn soft contact lenses. This patient was seeking refractive surgery to rid herself of contact lenses and to minimize her need for glasses. Her refraction was -6 +1 X 90 for 20/20- BSCVA in her left eye, and her right eye had essentially the same refraction, yielding 20/20 BSCVA. One notable finding that was present on the topography in each eye (Figure 1) was inferior corneal steepening on the order of 4.0 D. The central corneal power was 41.5 D and central pachymetry was 525 µm.

Two additional findings worth noting: (1) the photokeratoscopy view showed irregular mires in the superior peripheral cornea, and (2) upon slit lamp examination, there was subepithelial fibrosis with thickening present superiorly. I also noticed distinct mild opacification that obscured iris detail. This irregular, kidney bean-shaped area covered approximately 4 X 2 mm and corresponded with the photokeratoscopy mire irregularity.

1. Should this patient be counseled against corneal weakening refractive surgery?
2. Is this a situation in which additive technology such as ring segments could be utilized?
3. Would you test for form fruste keratoconus?
4. Should the surgeon deny surgery and recommend rigid gas permeable contact lenses?

My diagnosis revealed that the patient had bilateral Salzmann's nodular degeneration with induced trace-to-mild irregular astigmatism. First, I counseled her regarding my finding, as well as my rationale for treatment. I administered topical anesthesia to the patient, and completed superficial keratectomy at the slit lamp using a PRK spatula. As is typical with this condition, I was able to identify the edge of the subepithelial fibrosis after debriding the epithelial layer; I then elevated that edge. Next, I easily peeled away the fibrous tissue mound from a pristine underlying Bowman's layer. Finally, I placed a bandage contact lens over the cornea, administered a topical antibiotic as well as NSAIDs, and prescribed an oral analgesic as needed. I recommended blepharitis lid hygiene by instituting hot moist packs and lid scrubs. Chronic staphylococcal blepharitis was the most likely cause of Salzmann's nodular degeneration.

Three weeks after completing the superficial keratectomy, I obtained corneal topography of the patient's eyes (Figure 2). Note the presence of regular, with-the-rule astigmatism, the lack of inferior-superior discrepancy, and the regular mires throughout upon photokeratoscopy. Preoperatively, the patient had had mild retinoscopic scissor reflex. Following the superficial keratectomy procedure, the patient's retinoscopic reflex was normal. Her manifest refraction revealed an essentially identical refraction, but the quality of her vision was subjectively better. She was able to read the optotypes very quickly during her examination, unlike before the superficial keratectomy, in which the optotype reading was moderately slow on the 20/20 line. The patient underwent uncomplicated bilateral LASIK without incident, and had excellent UCVA 5 months postoperatively.

Salzmann's nodular degeneration is a fairly common corneal finding. In this case, I performed a superficial keratectomy to restore the congenital corneal contour. Afterward, the patient's corneal topography was normal and I considered her to be an otherwise ideal LASIK candidate. I could have chosen other options; I could have performed the procedure as mentioned, but instead substituted either PRK or LASEK as the second-stage refractive treatment. Alternately, I could have contemplated one-stage superficial keratectomy followed by excimer laser PRK in the same setting. However, I did not choose this approach because the diagnosis of inferior corneal steepening could not be ruled out prior to ablation. Additionally, a staged approach allowed me to obtain the most accurate refraction prior to performing refractive ablation. Another option could have been a one-stage custom laser ablation. In my opinion, however, old-fashioned corneal surgery in the form of a superficial keratectomy can create a perfect corneal surface for routine excimer laser vision correction. In essence, low-tech surgery obviates an unavailable high-tech approach.

In my clinical opinion, any degree of form fruste keratoconus is an absolute contraindication for weakening corneal refractive surgery. There are many findings that must be ruled out to deny the presence of this condition: (1) inferior corneal steepening, (2) inferior-superior discrepancy greater than 2.0 D, and (3) scissoring or fish-mouth retinoscopic reflex. I have discovered one other early and consistent indicator for form fruste keratoconus, and have coined the term “against-the-rule astigmatism with kissing at the 270º meridian.” One can clearly see this finding on an axial map, which should immediately raise suspicion of form fruste keratoconus (Figure 3). If present, the surgeon should search for other identifying features.

In summary, clinical diagnosis of form fruste keratoconus is an essential aspect of clinical practice. Likewise, surgeons should also identify false-positive keratoconus, and make a specific diagnosis for proper treatment.
John F. Doane, MD, FACS, is in private practice with Discover Vision Centers in Kansas City, Missouri, and is Clinical Assistant Professor of the Department of Ophthalmology, Kansas University Medical Center. Dr. Doane my be reached at (816) 350-4539; jdoane@discovervision.com
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