Preoperative Considerations: Patient Selection and Evaluation
Sandeep Jain
Margaret Chang
Preoperative evaluation for refractive surgery follows a structured sequence that includes patient interview followed by a complete ophthalmologic examination (Table 68-1). The aim of preoperative evaluation is to answer three broad questions in addition to generating specific refractive data for the actual treatment:
Is it possible safely to perform refractive surgery in the patient?
What is the risk of possible complications, given the patient specifics?
Is it possible to meet the expectations that the patient has from the surgery?
Patients are advised to discontinue wearing contact lenses at least two weeks before the preoperative evaluation and to schedule up to 2 hours for the preoperative evaluation examination. Because cycloplegic refraction is performed as part of the examination, patients are advised that they may be unable to read for 6 to 12 hours and are advised against driving by themselves during this time.
A detailed history forms an important part of the patient selection process. The purpose is to identify patients who either are not expected to have a good postoperative outcome or not expected to be satisfied with the procedure.
PATIENT CHARACTERISTICS
Patients younger than 18 years of age and women who are pregnant or breast-feeding cannot have refractive surgery. Patients engaged in sports in which blows to the face and eyes are a common occurrence (boxing, wrestling, or martial arts), or in occupations that have a greater likelihood of producing trauma or injuries (armed forces, police, or secret service), may have refractive surgery but are usually offered photorefractive keratectomy (PRK) or laser subepithelial keratomileusis (LASEK) as alternatives to laser in situ keratomileusis (LASIK). Because refractive surgery may cause loss of best corrected visual acuity, loss in contrast sensitivity, or higher-order aberrations (if the treatment is decentered), patients should check with their prospective employers about the qualifying refractive criteria. Some employers require contrast sensitivity testing and glare disability measurement in addition to determining uncorrected Snellen visual acuity.
Expectation from the Surgery
The goal of refractive surgery is to reduce the dependence on eyeglasses and contact lenses. Postoperative vision invariably can be improved further with additional optical correction. In presbyopic patients, additional near-vision correction is required after adequate distance-vision correction. Patients who expect perfect distance vision or presbyopic patients who expect equally good distance and reading vision are poor candidates for refractive surgery. If monovision is suggested as an option, then a 2-week trial of contact lens monovision is given to determine if the patient accepts the compromises inherent in the monovision strategy. One in four patients fails to adapt to monovision (1,2).
Refractive Stability
The refraction should be stable over at least 1 year. Patients in whom refraction has changed considerably over the past 1 year (more than 0.5 D), are poor candidates for surgery.
Ocular and Medical History
Refractive surgery is contraindicated in patients with history of herpes simplex or herpes zoster ophthalmicus. Reactivation of herpes virus infection has been reported in the postoperative period (3). Refractive surgery is not performed in patients who have keratoconus and in those who are on Accutane therapy. Relative contraindications to refractive surgery include patients who have glaucoma, patients who are glaucoma suspect or have ocular hypertension, or those who have a history of uveitis. If the patient has a history of prior refractive surgeries, particularly radial or astigmatic keratotomy, then additional refractive procedures (PRK or
LASIK) are associated with unpredictable refractive outcomes and greater potential complications.
LASIK) are associated with unpredictable refractive outcomes and greater potential complications.
TABLE 68-1 PREOPERATIVE TESTS FOR REFRACTIVE SURGERY | ||||||||||||||||||||||||||||||
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Certain medical conditions, such as autoimmune diseases (e.g., lupus, rheumatoid arthritis), immunodeficiency states (e.g., human immunodeficiency virus infection), and diabetes, may prevent proper healing after a refractive procedure and therefore also are considered relative contraindications. If the patient has a history of keloid formation, then PRK or LASEK is to be avoided. Although safety with PRK has been reported in keloid formers, LASIK seems to be safer in such patients given the minimal wound healing response (4).
EYE EXAMINATION
A complete ophthalmic examination is performed. This includes recording uncorrected Snellen visual acuity, visual acuity with current eyeglasses, dry manifest refraction, and wet manifest refraction (after cycloplegia with 1% cyclopentolate eye drops). Based on the currently approved indications, the extent of myopia and astigmatism determines the choice of excimer laser as well as whether wavefront-guided surgery is an option (Table 68-2).
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