CHAPTER 5

General Ocular Evaluation

Andrea D. Border, John F. Doane, Scot Morris, and James A. Denning

CHAPTER CONTENTS

Visual Acuity Assessment

Eye Dominance Testing

Monovision Considerations

Pupillometry

Slit-Lamp Examination

Fundus Examination

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VISUAL ACUITY ASSESSMENT

• Measure uncorrected distance, near, monocular, and binocular visual acuity. (Fig. 5-1).
  
• Measure best corrected visual acuity (BCVA) for distance, near, monocular, and binocular vision with patient wearing prescribed spectacles or contact lenses (if applicable).
  
• Measure and document acuity preoperatively and at all postoperative evaluations for statistical assessment, progression analysis, and medicolegal documentation.
  
• Carefully educate patients with reduced acuity because of pathology or amblyopi that refractive surgery probably will not improve their BCVA.

Figure 5-1   Pre- and postoperative near-vision acuity should be taken for each eye and both eyes together.

EYE DOMINANCE TESTING

• manifest refraction binocular balance testing [the dominant eye is left with “clearer” vision when equal balance unobtainable for both eyes (see Chapter 6)]
  
• crucial for surgically created monovision (the dominant eye is almost always corrected for distance vision, and the non-dominant eye is targeted for near or intermediate vision)
  
• confirmation or identification of a patient’s dominant eye

Methods

• Ask the patient which eye he or she uses to look through a telescope or focus a camera (identified eye usually dominant).
  
• Perform some or all of the specific methods discussed below.

Pointing

The use of pointing to determine a patient’s dominant eye is simple but obtained results may be unreliable.

Methods

• Instruct the patient to leave both eyes open and point at a distant object using an index finger and with the arm fully extended.
  
• If the object becomes displaced relative to the finger when the patient closes one eye, then the patient closed the dominant eye, but if the object did not become displaced, then the closed eye is nondominant.
  
• Repeat this test to confirm results.

Framing

The framing method of determining a patient’s dominant eye is simple to perform but may provide ambiguous results.

Methods

• A patient uses both hands (thumbs and index fingers) to create a triangle-shaped “frame” around a readily identifiable, small, distant object (Fig. 5-2A).
  
• With arms fully extended and both eyes open, the patient frames the object and then brings both hands toward the face moderately quickly, keeping both eyes open with the distant object sighted and in focus the entire time (Fig. 5-2B). (The patient should frame the dominant eye.)
  
• If the patient cannot perform this task without seeing the distant object as “double,” then the patient may be partially or totally ambiocular (i.e., without a strongly dominant eye).
  
• Instruct the patient to repeat the procedure to confirm results.

Hole Card

This test uses the same principle as the framing method but may also provide ambiguous results.

Figure 5-2   (A) The patient “frames” a distance target with both hands. (B) The patient should select (frame) the dominant eye.

• Place a four prism diopter lens BO over the patient’s suspected dominant eye while the patient fixates with both eyes on a distant object (Fig. 5-3).
  
  
  
  • If this is truly the patient’s dominant eye, the examiner should notice a “shift” in the patient’s opposite (nondominant) eye as it attempts to re-fixate.
  
  
• Next, place the 4^Δ BO prism over the suspected nondominant eye with the patient fixating on the same distant object.
  
  
  
  • If this is truly the patient’s nondominant eye, the examiner should note little to no eye shift in the opposite (dominant) eye.
    
  • If the examiner has difficulty detecting eye shift versus no eye shift when presenting the prism to either eye, try increasing the prism amount to elicit a more substantial reaction.
  
  
• If the 4^Δ BO test and the other eye dominance tests yield conflicting results, then consider the patient to be ambiocular. (Generally, ambiocular patients do not accept monovision well and should be considered very cautiously as monovision candidates.)

Figure 5-3   The examiner places a four-prism diopter lens BO over the patient’s suspected dominant eye as the patient fixates on a distant target.

MONOVISION CONSIDERATIONS

• the patient’s personality, age, hobbies, and goals for refractive surgery
  
• determination of monovision target power (allows a patient adequate near/intermediate vision while maintaining acceptable distance vision)
  
• testing of patients who use computers regularly by using the patient’s habitual computer font size and working distance at a computer terminal
  
• realistic patient expectations about surgical results
  
• ambiocular patients (of 1 in 10 patients in general population unable to accept any level of monovision, most are difficult to measure and quantify; see Eye Dominance Testing)
  
• patient preference of the dominant eye for near vision (should be attempted only with careful trials and documentation and after performing a trial run of monovision with contact lenses)
  
• previous monovision failure
  
  
  
  • possible success with surgical monovision for patients with previously unsuccessful monovision contact lenses (may have been caused by dry eyes, poor lens fit, inaccurate lens powers, or improper eye selection)
    
  • consider cautiously as surgical candidates until proven otherwise
    
  • requires preoperative trial frames for motivated patients
  
  
• patient education
  
  
  
  • discussion of advantages and compromises of monovision with all presbyopic patients and those older than 40 years, the average age of onset for presbyopia (highly motivated patients < 40 years old may be considered if thoroughly educated and intent on undergoing the procedure)
    
  • the possible reversibility of monovision with enhancement surgery if monovision unacceptable [most applicable for radial keratotomy (RK), photorefractive radial keratectomy (PRK), and laser in situ keratomileusis (LASIK) myopic candidates who are intentionally undercorrected in one eye to create monovision]
    
  • notification of the possible postoperative adjustment period that lasts from one to several weeks and may be disorienting
    
  • advantages (lifelong decreased or eliminated dependence on spectacles for near and intermediate tasks)
    
  • disadvantages (possible scotopic halos and glare, compromised depth perception in dim lighting that may be alleviated by thin night-driving eyeglasses)
  
  
• documentation of the discussion about monovision
  
  
  
  • the patient’s decision for or against monovision
    
  • the patient’s understanding of possible consequences of his or her choice (e.g.,possibility of increased night glare vs.need for reading glasses)

• identification of poor monovision candidates before surgically creating monovision (Fig. 5-4)
  
• determination of monovision target powers

Figure 5-4   The trial frame is set up with the patient’s manifest refraction results for each eye, and an occluder lens is then placed over the patient’s dominant eye. The examiner should place a plus power lens appropriate for the patient’s age and visual goals over the patient’s nondominant eye.

• Place the patient’s manifest refraction result for each eye in the trial frame.
  
• Place an occluder lens in the trial frame over the patient’s dominant eye (see Eye Dominance Testing for methods).
  
• Instruct the patient to look at a near vision card, and place a plus lens (for monovision) over the unoccluded eye.
  
• Select the power of the plus lens based on the patient’s age (from +1.00 D at 40 years of age to +2.00 D at 55 years of age) and visual goals (e.g., small near tasks like threading a needle or general intermediate tasks such as seeing a computer).
  
• After acknowledging the patient’s ability to see the near card, remove the occluder lens from the trial frame over the patient’s dominant eye to allow the patient to see binocularly in monovision
  
  
  
  • The patient initially may report ghosting or doubling of the near letters with binocular monovision in the trial frame (often occurs if the optical center is off in the trial frame lenses).
    
  • Instruct the patient to shift the near card slightly to attempt to remove the ghosting.
  
  
• Next, allow the patient to experience monovision at various distances with the trial frame by having the patient walk around with a technician.
  
• Try various monovision target powers with the patient (Fig. 5-5).
  
  
  
  • For example, if a 46-year-old patient has an initial monovision target of +1.50 D but does not see a computer screen well with this lens, the technician should try a target of +1.00 D at the computer).
    
  • If more acceptable to the patient and agreeable with the patient’s goals, adjust the target.
  
  
• If a patient chronically experiences significant ghosting of near letters or experiences outright diplopia or nausea that does not subside, the patient will probably not tolerate monovision.
  
• Single-vision soft contact lenses (for patients who have essentially spherical refractive errors) are an easy, inexpensive way to allow refractive surgery candidates to experience monovision in their own home or work environment.

Figure 5–5   After visual acuities are taken at distance and near with the tentative monovision target, the technician can walk with the patient to allow visualization of various distances in monovision. This patient desires clear computer vision, and the technician is trying various monovision powers to achieve the best focus for the patient at a computer terminal.

PUPILLOMETRY

• Simply line up semicircles (usually ranging from 1.0 to 10.0 mm in increments of 1.0 mm) at the vertical midpoint of the patient’s pupil and determine which semicircle on the card best represents the patient’s pupil size (Fig. 5-6).
  
• Record corresponding measurements from the pupil card in both photopic (light) and mesopic (dim) conditions.

Figure 5-6   Pupil size is measured with a pupil card in photopic and mesopic conditions to determine minimum and maximum physiologic pupil size in a patient.

• Use this gauge in the same manner as the pupil card.
  
• Measure pupil sizes larger than 0.5 mm in scotopic and mesopic conditions by comparing actual pupil size with the full circles and semicircles on the gauge (from 1.0 to 10.0 mm in increments of 0.5 mm) (Fig. 5-7A).

Figure 5-7   (A) The Holladay-Godwin pupil gauge. (B) The Colvard pupil gauge.

This hand-held, battery-operated pupillometer from Oasis (Glendora, CA) preoperatively evaluates and measures the scotopic and photopic pupil size. It allows accurate visualization of the pupil in a darkened examination room by incorporating light amplification technology for accurate scotopic measurements (Fig. 5-7B).

SLIT-LAMP EXAMINATION

• preoperative identification of pterygium (ideally, elimination of it prior to any corneal surgery)
  
• identification of corneal neovascularization or pannus (significant intraoperative bleeding may occur during corneal procedures with either of these)
  
• identification of corneal endothelial pigment spindles (may indicate future or current pigment dispersion, glaucoma)
  
• preoperative documentation of intraocular pressure (IOP) (future readings will be lower than preoperative values by approximately 1.5 mmHg/100 μm of ablated tissue for laser procedures during which significant corneal tissue is removed)
  
• identification of inactive corneal opacities and/or scars and assessment of their impact on visual acuity (Fig. 5-8; see Chapter 3)
  
• identification of dry eye or keratoconjunctivitis sicca (if severe, then may be contraindications for corneal surgery)
  
• recognition of anterior basement membrane dystrophy (may complicate LASIK procedures intraoperatively or delay visual recovery with any refractive surgery procedure) (see Chapter 3)

Figure 5-8   Central corneal scars or opacities must be evaluated for their impact on visual acuity.

• endothelial dystrophies (such as Fuchs’s dystrophy or severe gutatta with a total cell count < 1500) (Fig. 5-9; see Chapter 3)
  
  
  
  • increased risk for future corneal edema and decompensation (bullous keratopathy)
    
  • particularly worrisome with clear lens extraction refractive surgery (associated with a 4-8% cell loss during the procedure)
  
  
• any active anterior segment infectious or inflammatory process (must be completely resolved preoperatively)
  
• keratoconus with or without Vogt’s stria or Fleischer’s ring (Fig. 5-10) (for any corneal refractive surgical procedure)

Figure 5-9   Severe corneal gutatta seen in retroillumination. This patient has a reduced endothelial cell count shown by specular microscopy.

FUNDUS EXAMINATION

• identification and discussion of macular pathology such as pathological myopic degeneration, age-related macular degeneration, or diabetic retinopathy (Fig. 5-11) (discussion with patient warranted if pathology has already affected visual function because refractive surgery will not increase the patient’s BCVA)
  
• identification of patients with prior vitreoretinal, cataract, or strabismus surgery (may complicate refractive surgical procedures such as LASIK or clear lens extraction)
  
• identification of significant vitreal syneresis or lattice degeneration associated with traction or holes (may complicate LASIK or clear lens extraction refractive surgical procedures)
  
• identification of severe glaucoma or other optic nerve disorders (consider on a case-by-case basis) (Fig. 5-12)
  
  
  
  • IOP rises transiently during LASIK surgery
    
  • poor long-term visual prognoses of severe glaucoma with any refractive surgical procedure
  
  
• identification of retinitis pigmentosa (consider on a case-by-case basis with emphasis on patient counseling)
  
  
  
  • aggravation of the associated attenuated vasculature and optic nerve changes because of marked transient rise in IOP during LASIK
    
  • inhibition of night vision in patients with retinitis pigmentosa after other refractive surgical procedures, including LASIK
  
  
• identification and evaluation of posterior staphyloma using ultrasonography particularly when considering clear lens extraction (see Chapter 7)

Figure 5–10   Fleischer’ ring seen around the base of the cone in a patient with keratoconus.

Figure 5-11   Macular degeneration has not yet affected visual acuity in this patient.

Figure 5-12   Severe glaucomatous damage has already occurred in this optic nerve, but central visual acuity is not yet affected in this patient.

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