Introduction
Clinician-patient communication is important to ensure a satisfactory outcome for refractive surgery. Clinicians can educate and counsel patients regarding alternatives to refractive surgery, as well as the risks and benefits involved with refractive surgery, so that the patient can make an informed decision. During the consultation period, clinicians will also evaluate and ensure that patients' expectations of surgical outcomes are realistic.
Preoperative Evaluation
All preoperative evaluations should include a complete medical history. Patients considering refractive surgery are initially required to undergo an eye examination to ensure that no abnormalities exist that may adversely affect their long-term visual health. It is important that patients do not wear soft contact lenses for at least 2 to 3 days before the preoperative assessment. Also, patients who wear hard contact lenses should leave their contacts out for at least 2 weeks before preoperative assessment.
Patient History
During the consultation period, clinicians will obtain thorough patient ocular and medical histories. A patient's family ocular and medical history is valuable because the clinician can determine if the patient may be a target for any inherited ocular or systemic disorders. It is important to document any history of diabetes, collagen vascular disease, systemic inflammatory disease, keratoconus, corneal degenerations or dystrophies, cataracts, retinal detachment, retinal or macular disease, and any optic nerve disorder.
The clinician should document all systemic and ocular medications used by the patient. By examining a patient's medication records, ophthalmologists may uncover important information not found in the patient's medical history. Clinicians should document any allergies or adverse reactions a patient may have to medications, especially antibiotics or pain medications, which are commonly used to treat complications of refractive surgery.
Certain existing systemic conditions may represent contraindications to refractive surgery. It is important to inquire about signs and symptoms of collagen vascular disease such as systemic lupus erythematosus, rheumatoid arthritis, or Sjögren's syndrome, as well as other autoimmune diseases. Certain collagen vascular diseases can cause unpredictable and possibly catastrophic corneal healing complications after laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK). Diabetes can be a relative contraindication to refractive surgery. Patients with uncontrolled diabetes often have unstable refractions secondary to changes in the lens and may have a poor-healing corneal epithelium. Also, any evidence of retinopathy should be carefully evaluated and treated. In a patient with any diabetic retinopathy, consultation with the patient's retinal surgeon is important prior to making any decision as to the advisability of refractive surgery. Due to the time required for corneal wound healing, it most likely will not be advisable to proceed with placement of a contact lens on the cornea for panretinal, grid, or focal photocoagulation for several weeks to a few months after surgery.
Refractive surgery is not recommended during pregnancy because changes in vision and refraction can occur during pregnancy. Patients should wait at least 3 months postpartum and should have stable refractive errors prior to any refractive surgery.
A comprehensive ocular history should also be performed. The important aspects to document in any ocular history include ocular disease, refractive stability, contact lens history, previous cornea surgery, or ocular trauma.
A previous history of herpes simplex keratitis is considered a contraindication to laser corneal surgery, as the ultraviolet wavelength laser clearly has the ability to reactivate latent virus. Recurrence of herpes keratitis is a common complication after refractive surgery. Patients with cataracts should not proceed with refractive corneal surgery because eventual refractive cataract surgery can accomplish the same refractive goals. The issue becomes somewhat uncertain when the lens opacity is minimal, without symptoms or a decrease in best-corrected visual acuity, and it is unclear whether the patient will develop a symptomatic lens opacity anytime within the next decade or two. Patients with residual refractive error following cataract surgery can consider refractive corneal surgery as an option to reduce their residual refractive error.
Any history of previous ocular trauma or ocular inflammation and subsequent therapy should be noted. The clinician should note any corneal scarring, lid abnormalities, or damage to any of the internal structures of the eye.
As a general rule, candidates for refractive surgery should be 18 years of age or older, and the refraction should be stable to within ±0.50 D per year. The stability of the refraction is crucial to the outcome of LASIK or PRK, because it is used to calculate the amount of excimer energy laser used. If the refraction is inaccurate, then the final visual outcome will not be accurate.
Clinicians will record a detailed contact lens history that will cover factors such as the type of lenses worn, length of time worn, contact lens failures, and the reasons for discontinuing contact lens wear. Irregular corneal curvature and corneal molding are common with both rigid gas permeable or hard contact lenses and can even occur with soft contact lenses. Patients who wear gas permeable or hard contact lenses should discontinue use for a minimum of 2 to 3 weeks before the preoperative evaluation. If stability of the refraction and computed corneal topography is not established, then corneal warpage is usually still present, and the surgery should be delayed until stability is documented. If stability has not been documented by 2 to 3 weeks after removing rigid contact lenses, most surgeons prefer to wait until two refractions measured at least 1 week apart show no change. Soft contact lens wear is typically discontinued for a minimum of 3 days. Occasionally, soft contact lens wearers can experience changes in refraction and topography depending on the thickness and oxygen permeability of the lens and wear time.
Quality-of-life issues also motivate patients to consider surgical correction and this is also considered during consultation. Ophthalmologists will document the patient's motivation for wanting refractive surgery, which may be related to occupation, recreation, or lifestyle. Documenting this information can assist the clinician to determine how the patient's vision is used. For example, certain occupations have strict requirements for corrected and uncorrected visual acuity. Some branches of the U.S. armed forces do not admit patients with surgical correction of refractive error. The patient should investigate any job regulations before considering refractive surgery. The surgeon should stress to patients that it is their responsibility to clarify preoperatively the policies of potential employers regarding the hiring of persons who have undergone surgical correction of refractive error.
Ocular Examination
Eye Dominance Testing
Testing for eye dominance can be accomplished in a variety of ways. The most common method
requires a patient to view a distant target through a small hole created by the patient's
thumb and forefinger. The patient must focus using both eyes. Keeping the object in view,
the patient moves the hole closer to his or her face until it is in front of one eye. Once
the image falls in front of one eye, this eye is identified as the dominant eye.
Some surgeons will treat the nondominant eye first. These surgeons reason that if a patient's eye reacts negatively to refractive surgery, or if the patient has a visually threatening risk, it is best to encounter this in the nondominant eye. Also, possible complications, refractive outcomes, and corneal healing of the first surgical eye can then be applied to the surgical planning of the second eye.
Cycloplegic refractions are important parts of every initial refractive evaluation. Cycloplegics will paralyze accommodation to rule out pseudomyopia. They are used to uncover "latent hyperopes" in younger, pre-presbyopic patients. Generally, most surgeons base their nomograms for correction of myopia on the manifest refraction using the plus fogging technique unless the cycloplegic refraction differs by more than 0.50 D. In this case, the nomogram will lean more towards the cycloplegic refraction. In hyperopes, many nomograms will require the use of the cycloplegic refraction, necessary to completely correct the hyperopia.
Patients approaching the presbyopic age must be informed of the option of monovision. Patients may not be aware that if both eyes are corrected for distance there may be a need for reading glasses after refractive surgery. Patients in their late 30s and early 40s, who were able to read with spectacles preoperatively, may immediately require reading glasses postoperatively. The need for reading glasses postoperatively occurs because of the higher accommodative demand that results from a corneal plane correction. Generally, the nondominant eye is used as the "near eye" for monovision, although so-called crossed monovision, in which the dominant eye is corrected for near, has been often documented to be successful both with contact lenses and surgery.
Pupil Size
Pupil size in light and dark settings, pupil shape, and a pupil's reactivity to light, both
direct and consensual, should be documented. Pupil size becomes more relevant when considering
refractive procedures for patients with very large pupils in low light conditions. All
patients must understand that there is a possibility of glare or halos postoperatively.
Repeated studies have concluded that it is difficult, if not impossible, to predict preoperatively which patients
will experience glare or halos after surgery. Studies also indicate that there appears to be
no pupil size cut-off that is a useful predictor of the glare or halo side effect. However,
some surgeons will use laser systems that may provide a larger treatment zone for patients
with large pupil diameters.
Extraocular Muscle Examination
A basic extraocular muscle examination is performed to determine the presence of any
abnormalities in gaze function. Conditions such as phorias or tropias can become
complicated by refractive surgery. If a patient has a significant phoria and is left
hyperopic after refractive surgery, that patient can potentially manifest a tropia,
which could cause irritation. Testing for significant phorias or tropias can determine
if a patient actually has prism in his or her glasses and may not be capable of single
binocular vision without glasses. Prior to refractive surgery, some patients are motivated
enough to undergo surgical treatment of their tropia, which has been controlled with prism
in their glasses. It is much easier to treat tropia before refractive surgery, and clinicians
should make patients aware of their condition.
External Examination
A thorough external examination of the ocular adnexa, including the eyelids, eyelashes,
and lacrimal system, should be performed. It is important to document any lid or lash
abnormalities, including ptosis, blepharitis, meibomitis, chalazia, ectropion, entropion,
trichiasis, or any evidence of past lid trauma. Ptosis should be documented because lid
speculum trauma and postoperative steroid regimens can cause transient or permanent ptosis.
Ectropion, entropion, lagophthalmos, and trichiasis can cause significant problems with
wound healing because of inadequate lid closure, lid apposition, and tear spreading.
Any lid malposition that can affect corneal healing should be treated prior to undergoing
refractive surgery.
Slit Lamp Examination
A thorough slit lamp examination is required before refractive surgery is performed. The
eyelids and eyelashes should be evaluated carefully. Blepharitis and meibomitis can cause
significant problems with corneal healing, such as infectious keratitis and corneal ulceration,
and should be treated aggressively and under good control before proceeding with any refractive
surgery procedure. The conjunctiva should be examined to note any irregularities, scars, or
cellular reactions that can indicate previous infection, inflammation, or trauma. The
precorneal tear film should be evaluated and tear-function testing should be performed when
appropriate.
Schirmer tests should be performed if dry eye syndrome is suspected. Inadequate tear function, whether quality or quantity related, can slow or delay corneal wound healing and represent the increased possibility of infection or other serious complications (including corneal opacification or melt). The possibility of a systemic etiology for dry eye syndrome, such as collagen vascular disease, should be considered. The use of adjunctive tear therapy or punctal occlusion may be necessary prior to a planned refractive procedure to help ensure adequate surface lubrication for healing. If the punctate keratitis resolves with a conservative lubrication regimen, most surgeons should feel comfortable performing LASIK. Postoperatively, the cornea is more likely to experience the signs and symptoms of dryness related to the corneal denervation that occurs for the first few weeks to months. The toxicity of postoperative medications and the inflammatory reaction following surgical trauma also contribute to altered corneal topography that indicates a change in the tear film distribution across the corneal surface.
The corneal epithelium and basement membrane should be examined carefully, and any irregularities that may further indicate recurrent corneal erosion tendencies should be documented. Epithelial basement membrane dystrophies that are causing recurrent erosion should be noted and treated prior to performing refractive surgery. Treatment with excimer laser phototherapeutic keratectomy may also be an option for treatment, especially in the presence of recurrent corneal erosion unresponsive to more conservative modes of treatment. The corneal stroma should be evaluated for clarity and for the presence of any scarring or thinning that can indicate previous infection, trauma, or inflammation. The corneal endothelium should be evaluated for the presence of guttata that may be associated with corneal thickening, such as in Fuch corneal dystrophy, or inflammatory residue, such as keratic precipitates. The anterior chamber depth and clarity should be documented.
Clinicians should examine the preoperative corneal thickness of patients considering LASIK. A central pachymetry measurement should be performed on all LASIK patients to ensure that the refractive correction can be accomplished with excessive removal of corneal tissue. After the creation of the flap and the laser procedure, it seems that at least 250 µm of posterior "untouched" corneal tissue must remain to minimize the risk of postoperative ectasia.
Clinicians should evaluate patients for any iris abnormalities, especially the presence of any iris transillumination defects that may indicate pigment dispersion syndrome. Myopes are at increased risk for developing pigment dispersion syndrome. A thorough examination of the lens should be performed to check for the presence of any visually significant or progressive opacities. Congenital opacities or small developmental opacities are typically not contraindications for refractive surgery. However, any progressive lens opacity, such as a posterior subcapsular opacity, should be documented and refractive cataract surgery may be an option. For small lens opacities in which it is difficult for surgeons to determine whether the congenital opacity is old or an early, small, progressive cataract, patients should not undergo refractive surgery for 6 months to 1 year after initially documenting the lens opacity.
It is important to test and document intraocular pressure (IOP) to rule out any ocular hypertension or glaucoma. Topical steroids are used in many refractive procedures. Therefore, steroid-induced glaucoma can occur and must be monitored.
Dilated Fundus Exam
Dilated fundus exams are crucial to examining the retina for pathology. Peripheral retinal
degenerations, tears, holes, or dystrophies should be treated appropriately and documented.
Corneal Topography
The ability to quantitatively evaluate the central and peripheral cornea with computed
corneal topography has become a standard component of the preoperative refractive corneal
surgery evaluation. Surgeons will want to attempt to rule out keratoconus in all patients who are evaluated
for refractive surgery. A significant number of keratoconus cases remain undetected with
refraction, clinical evaluation, and conventional keratometry, but still have a
keratoconus-type pattern on computed topography. This topographic form of keratoconus
is known as preclinical, or forme fruste, keratoconus. It may not be possible to exclude mild keratoconus
even with topographic studies, but it is important to consider this possible
diagnosis as patients with any degree of keratoconus have the potential for
unpredictable results and for postsurgical irregular astigmatism, especially with
incisional procedures. Computed corneal topography is also useful for evaluating the
postoperative effects of refractive surgery. It can help to analyze astigmatic surgical
plans, monitor contact lens-induced corneal warpage, and evaluate postsurgical refractive
effect.
Patient Counseling
Clinicians should discuss the nonsurgical alternatives, such as glasses or contact lenses
with the patient. Well-informed patients will understand that refractive procedures such
as LASIK are performed to decrease the patient's dependency on spectacles or contact
lenses, but may not completely eliminate the need for occasional lens use. Clinician-patient
consultation should emphasize expected outcomes, likelihood of success (chance of
attaining 20/20 and 20/40 visual acuity), chance of loss of best corrected visual acuity,
risk of infection, scarring, glare, and the potential need for
retreatments. The patient should be made aware that because of
individual variability in wound healing, clinicians cannot guarantee the
surgical outcome, and the patient's expectations of surgery should
take this into consideration. Occupational or recreational visual demands and
coexisting medical conditions are factors that will affect the patient
on an individual basis. Clinicans should provide patients with the
opportunity to request clarification or raise questions. Using
videotapes may enhance the transfer of this information from the
clinician to the patient. Literature and consent forms for review at
home can also be helpful in ensuring that the patient has had the
ability to absorb the important information. A well-informed patient is
often a calm patient intraoperatively and pleasant to handle
postoperatively, and has an understanding of the expected surgical
outcomes.
Bibliography
Gimbel HV, Penno EEA, eds. LASIK Complications: Prevention and Management. Intraoperative Complications. 2001.
McDonald MB, Steinert RF, Bafna S. Laboratory and clinical studies of excimer laser refractive surgery. In: Wu HK, et al, ed. Refractive Surgery. New York, NY: Thieme Inc; 1999.