Finding Flap Striae After LASIK
BY WILLIAM L. MILLER, OD, PHD, FAAO
As with diffuse lamellar keratitis, flap striae after LASIK are uncommon yet bothersome complications that can go undetected, frustrating patient and practitioner. Striae are sometimes called flap wrinkles or folds and are confined to the thickness of the flap. They manifest as irregularities and can be visible with biomicroscopy (macro) or manifest as subtle cases (micro) that are difficult to ascertain.
Microstriae often affect only the anterior limiting lamina and overlying epithelium. Macrostriae may affect the entire flap thickness and are less of a diagnostic challenge. Because most of the difficulties lie with microstriae detection, we'll focus on their detection and management.
Causes and Signs
Observing negative staining lines in the flap with sodium fluorescein or carefully observing the cornea using retroillumination are the easiest ways to find microstriae. These lines may be oriented radially, horizontally or vertically within the body of the flap. You can aid the retroillumination view by dilating the pupil and using the red reflex as a backdrop for microstriae detection.
Cases immediately after surgery are often detected by the surgeon. Others arise postoperatively. Causes include lid blinking forces, eye rubbing or other mechanical flap dislodgements. The greater the myopic correction, the deeper the resulting flap bed will be, which increases the risk for microstriae. A myopic photoablation forms a highly concave surface which tends to create a tenting effect that provides a biomechanical platform for possible striae formation.
If the microstriae are over the visual axis, the patient may have vague subjective visual complaints. In some cases he may have a reduced best corrected visual acuity or reduced contrast sensitivity function (Quesnel et al, 2004). This visual disturbance results from the irregular flap surface, which produces irregular astigmatism and/or optical aberrations. You also can use corneal topography to look for areas of regional variations in the map.
Managing microstriae may begin with a referral back to the surgeon. He may re-lift the flap and then float it back into position. Other remedies may include using a flap iron/manipulator or in severe cases stretching and suturing the peripheral flap region.
There have been discussions regarding the positive role contact lenses may play in managing microstriae. A case report by Araki-Sasaki et al, 2002, showed microstriae reduction in two patients wearing GP lenses. Another report demonstrated that bandage contact lenses did not prevent the formation of microstriae (Sekundo et al, 2005).
Additional methods to relieve the microstriae may include superficial debridement over the area to relieve any possible hyperplasia tension or hypotonic topical solutions to rehydrate the flap.
In cases of reduced best corrected visual acuity or unsatisfactory subjective vision, it's important to identify possible reasons for the reduction. One reason may include flap microstriae. Careful observation with biomicroscopy with and without fluorescein will help you determine if microstriae are the cause.
You can perform these treatments weeks to months after surgery. However, the longer the time between their occurrence and treatment, the lower the prognosis for successful recovery.
You must also advise patients on ways to prevent microstriae. One suggestion is to advise your post-LASIK patients to wear protective eyewear when the potential for mechanical displacement increases such as during certain sporting activities, occupations or extracurricular events. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #147.
Dr. Miller is the Director, Cornea and Contact Lens Service at the University of Houston College of Optometry. He is a member of the American Optometric Association and serves on its Journal Review Board. You can reach him at firstname.lastname@example.org.