A 41-year-old Saudi male had a radial keratotomy in the left eye on August 20, 1987, for a refractive error of -5.50 -2.25 × 60°. His best spectacle corrected visual acuity was 20/30. His past history included clinical evidence of inactive trachoma including superior pannus, Herberts pits, and palpebral conjunctival scarring without follicles. The central cornea was clear on slit-lamp microscopic examination. Central optical pachometry was 0.55 mm and the diamond blade was set at 0.54 mm, 0.55 mm, and 0.62 mm for optical zones of 3, 5, and 7 mm, respectively. Sixteen centrifugal incisions were made.
Retinoscopic refraction performed 5 weeks after surgery was piano - 2.00 × 65°, and a visual acuity of 20/25. Fourteen months after surgery, the cornea had a central diffuse reticulate subepithelial scarring involving the Bowman's layer. By 2.5 years following surgery, the subepithelial cicatrization had increased in density and measured approximately 6 mm in diameter (Fig 1). At that time, the retinoscopic refraction was -8.00 -0.50 × 60°, 20/70.
On March 14, 1990, a homoplastic myopic keratomileusis in situ was performed. A whole donor eye was obtained. Air was injected into the globe to increase the intraocular pressure, the epithelium was removed, and a 6. 7 -millimeter diameter, 0.36millimeter thick resection was performed with the Barraquer microkeratome. The pneumatic fixating ring was then centered on the host cornea. A 6.7millimeter diameter, 0.24-millimeter thick anterior lamellar resection was performed with the microkeratome and the dissected corneal tissue was sent for pathologic examination. A 4.5-millimeter diameter, 0.11 -millimeter thick keratectomy was then performed in the bed of the cornea. The donor lenticule was sewn to the host corneal bed with a double antitorque 10-0 monofilament nylon suture. A piano therapeutic soft contact lens was applied. The retinoscopic refraction 7 weeks after surgery was - 2.00, 20/40.
Histopathologic evaluation of the patient's corneal tissue revealed subepithelial hyperplastic fibrosis replacing Bowman's layer, but with normal appearing subjacent stroma (Fig 2). Von Kossa's stain for calcium showed no evidence of calcium deposits.
Radial keratotomy is considered to be a safe procedure for the treatment of low to moderate myopia.1 Deterioration of the best corrected visual acuity following this technique has been observed.2"3 This patient had evidence of inactive trachoma and a perfectly clear cornea before surgery. "Reticular cicatrization" in the subepithelial area and in Bowman's region was noted 1 year after the radial keratotomy.
Chlamydia trachomatis is an intraepithelial microorganism that may lead to subconjunctival cicatrization, entropion, and trichiasis. Additionally, subepithelial cicatrization may be observed in the corneas of patients with inactive trachoma.4 This patient had a clear cornea before surgical intervention, but had evidence of inactive trachoma involving the superior limbus and the palpebral conjunctiva. The cause of the subepithelial scarring is unknown, but one can speculate that the previous chronic inflammation of trachoma may have affected the corneal epithelium and/or stromal keratocytes so that the radial incisions and the central flattening triggered a fibroblastic response. Similar reticular cicatrization of the cornea following myopic keratomileusis has been previously reported.5-6 Regression of the surgical effect could be attributed to the subepithelial cicatrization steepening the center of the cornea.
FIGURE 1: Central diffuse reticular subepithelial cicatrization of the axial cornea 14 months following radial keratotomy.
FIGURE 2: Light microscopy section of the corneal disc showing subepithelial hyperplastic fibrosis (between arrows) replacing Bowman's layer. Normal appearing stroma is seen underneath the fibroblastic reaction (hematoxylin eosin, original magnification × 150).
The presence of clinical evidence of inactive trachoma in patients with clear corneas may represent a risk factor for radial keratotomy. The number of incisions may also affect the formation of subepithelial reticular cicatrization. This patient had 16 incisions and this may have aggravated and precipitated the formation of extensive subepithelial cicatrization.
1. Salz JJ. How safe is radial keratotomy? Journal of Refractive Surgery. 1987;3:188-189.
2. Barker BA, Swinger CA. Complications of corneal refractive surgery. In: Schwab IR, ed. Refractive Keratoplasty. New York, NY: Churchill Livingstone; 1987.
3. Waring GO, Lynn MJ, Gelender H. Results of the prospective evaluation of radial keratotomy (PERK) study one year after surgery. Ophthalmology. 1985;92:177.
4. Tabbara KF. Chlamydial conjunctivitis. In: Tabbara KF, Hyndiuk RA, eds. Infections of the Eye. Boston, Mass: Little, Brown and Co; 1986.
5. Polit F. Keratomileusis, for myopia: initial experience in Saudi Arabia. Archivos De La Sociedad Americana de Oßhalmologia y Optometria. 1986;20:195-212.
6. Barraquer JI. Complicaciones post-operatorias profilaxis y tratamiento. In: Barraquer JI, éd. Cirugía Refractiva de la Cornea. Bogota, Columbia: Instituto Barraquer de America; 1989.