Slit-Lamp Examination

A complete slit-lamp examination of the eyelids and anterior segment should be performed. The conjunctiva should be examined specifically for scarring, conjunctivochalasis, or chemosis, which may cause problems with microkeratome suction. The cornea should be evaluated for surface abnormalities such as decreased tear breakup time (Fig 2-1) and punctate epithelial erosions (Fig 2-2). Significant blepharitis (Fig 2-3), meibomitis, and dry-eye syndrome should be addressed before refractive surgery, as they are associated with increased postoperative discomfort and decreased vision, and dry-eye symptoms frequently increase postoperatively. A careful examination for epithelial basement membrane dystrophy (Fig 2-4) is required, because its presence increases the risk of flap complications during LASIK. Patients with epithelial basement membrane dystrophy are not ideal candidates for LASIK and may be better candidates for surface ablation, because removal of the abnormal epithelium may be palliative. Signs of keratoconus, such as corneal thinning and steepening, may also be found. Keratoconus is typically a contraindication to incisional or ablative refractive surgery (see Chapter 10). The endothelium should be examined carefully for signs of cornea guttata and other dystrophies. Poor visual results have been reported in patients with cornea guttata and a family history of Fuchs dystrophy. Corneal edema is generally considered a contraindication to refractive surgery. The deposits of granular and Avellino corneal dystrophies may increase substantially in size and number in the flap interface after LASIK, resulting in poor vision.

Figure 2-1 Slit-lamp photograph showing decreased tear breakup time. After instillation of fluorescein dye, the patient keeps the eye open for 10 seconds, and the tear film is examined with cobalt blue light. Breaks, or dry spots, in the tear film (arrows) are visible in this image. Punctate epithelial erosions are also present.

(Courtesy of Christopher J. Rapuano, MD.)

Figure 2-2 Slit-lamp photograph, showing punctate epithelial erosions. Inferior punctate fluorescein staining is noted in this image from a patient with moderately dry eyes.

(Courtesy of Christopher J. Rapuano, MD.)

Figure 2-3 Example of blepharitis. Moderate crusting at the base of the lashes is shown in this image of a patient with seborrheic blepharitis.

(Courtesy of Christopher J. Rapuano, MD.)

Figure 2-4 Images of epithelial basement membrane dystrophy. Epithelial map changes can be obvious (A) or more subtle (B).Arrows show geographic map lines.

(Part A courtesy of Vincent P. deLuise, MD; part B courtesy of Christopher J. Rapuano, MD.)

The anterior chamber, iris, and crystalline lens should also be examined. A shallow anterior chamber depth may be a contraindication for insertion of certain phakic intraocular lenses (PIOLs) (see Chapter 8). Careful evaluation of the crystalline lens for clarity is essential in both the undilated and dilated state, especially in patients more than 50 years of age. Surgeons should be wary of progressive myopia due to nuclear sclerosis. Patients with mild lens changes that are visually insignificant should be informed of these findings and advised that the changes may become more significant in the future, independent of refractive surgery. They should also be told that IOL power calculations may be less accurate when performed after keratorefractive surgery. In patients with moderate lens opacities, cataract extraction may be the best form of refractive surgery.

• Kim TI, Kim T, Kim SW, Kim EK. Comparison of corneal deposits after LASIK and PRK in eyes with granular corneal dystrophy type II. J Refract Surg. 2008;24(4):392–395.

• Moshirfar M, Feiz V, Feilmeier MR, Kang PC. Laser in situ keratomileusis in patients with corneal guttata and family history of Fuchs’ endothelial dystrophy. J Cataract Refract Surg. 2005; 31(12):2281–2286.

Excerpted from BCSC 2020-2021 series: Section 13 - Refractive Surgery. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.