Download Achieving Better Than 20/20 Visual Acuity

REFRACTIVE SURGERY
Achieving Better Than
20/20 Visual Acuity
Top strategies for improving outcomes after laser vision correction.
BY STEVEN C. SCHALLHORN, MD
O
ver the years, LASIK surgery
has become safer, more precise, and more predictable.
Patients’ expectations of
success with the procedure have
therefore increased. Achieving results
of 20/20 or better in most cases is
critical, because uncorrected distance
visual acuity is the single most important factor in patients’ satisfaction
after LASIK. Great outcomes promote
the field of laser vision correction and
drive the reputations of surgeons,
laser centers, and their networks of
referring clinicians. For anyone who
wants to improve results, here are
some steps to consider.
Figure 1. One-month results in 32,569 eyes with low-to-moderate myopia undergoing LASIK.
EXCELLENT RESULTS: NOW THE RULE
The evidence shows that achieving an outcome better
than 20/20 should now be the norm for low-to-moderate
myopes rather than the exception.
In a recent retrospective analysis, Jan Venter, MD, and I
reported 1-month outcomes for 32,569 eyes of 17,713 patients who were treated at Optical Express centers in 2008.
The study included all eyes in Optical Express’ central
database that had a preoperative manifest spherical equivalent of 6.00 D or less, preoperative cylinder of 6.00 D or
less, a refractive target of emmetropia, and no prior refractive surgery. All treatments were performed with the Star
S4 IR excimer laser system (Abbott Medical Optics Inc.,
Santa Ana, CA) using a wavefront-guided ablation profile
(Advanced CustomVue). Flaps were created with either
the IntraLase FS laser (Abbott Medical Optics Inc.; 75.7%)
or the Moria Evo3 One Use-Plus microkeratome (Moria,
Antony, France; 24.3%), depending on the patient’s preference. Of this large pool of treated eyes, 91.8% saw 20/20 or
better uncorrected, and 71.6% saw 20/16 or better
1 month postoperatively1 (Figure 1). The average improvement in UCVA was 10 lines. These outstanding outcomes
are not just those achieved by a few expert surgeons in the
tightly controlled environment of a clinical trial; they are
the day-to-day results of 30 different surgeons practicing
at 41 laser centers.
Others have demonstrated similarly good results. For
example, David Tanzer, MD, recently reported on more
than 300 eyes treated with myopic LASIK using the Star
S4 IR excimer laser and a femtosecond laser to create
the flap. One month after surgery, the majority (84%) of
those eyes could see 20/12.5 or better.2
PATIENT SELECTION
The selection of good candidates for surgery remains
critical to success. Eye care specialists should perform a
careful preoperative examination to ensure that patients have no lenticular or macular pathology that
might prevent them from achieving a visual acuity of
20/20 or better. If the patient is otherwise a good candidate for vision correction, physicians should also consider the status of the ocular surface. Dry eye has been
associated with poor outcomes and regression of refractive effect after LASIK.3 Delaying surgery for a few weeks
NOVEMBER/DECEMBER 2010 ADVANCED OCULAR CARE 23
REFRACTIVE SURGERY
the patient will often see better when presented
with the aberrometry-derived cylindrical correction. Historically, eye care specialists have tended
to provide patients with the least amount of
cylinder they will tolerate in a manifest refraction.
That may be a sound strategy for prescribing
spectacles or contact lenses, but it is not precise
enough for corneal laser correction.
SURGICAL TECHNOLOGY
Technological advances such as femtosecond
lasers for the creation of the LASIK flap, FourierFigure 2. In night-driving simulations, patients who have wavefrontbased wavefront analysis, variable spot scanguided surgery see improvements in their ability to detect and identify
ning, iris registration, and customized ablation
road hazards compared to preoperatively, whereas about 40% of paplay a major role in improving outcomes. Pertients undergoing conventional surgery see significant losses on this
haps the most significant of these is customized
measure compared to preoperatively.
ablation. Compared with conventional treatments, wavefront-guided customized ablations
have been shown to significantly improve patients’ contrast sensitivity, reduce glare and
halos,4,5 and even improve functional night
vision. In night-driving simulations, the mean
ability to detect and identify road hazards improved after wavefront-guided surgery compared to preoperatively. On the other hand,
approximately 40% of patients who had conventional surgery had a significant decrease in
their ability to detect or identify road hazards
compared to preoperatively. In contrast, fewer
than 3% of those undergoing wavefront-guided
surgery experienced significant losses on this
measure compared to preoperatively6 (Figure 2).
Figure 3. In a large, retrospective comparison of eyes with flaps created
Femtosecond laser technology has also imby the IntraLase FS laser or a mechanical microkeratome, the laser
proved outcomes. In our studies at Optical Exgroup had better UCVA 1 day postoperatively, especially at the 20/20
press, we compared outcomes in eyes with LASIK
and 20/16 ranges.7
flaps created by a femtosecond laser versus a
microkeratome. Predictability was similarly high in
in order to treat any preexisting ocular surface disease
both groups, but the femtosecond group had better UCVA,
can go a long way toward improving outcomes.
especially at the 20/16 or better ranges7 (Figure 3). This difference was maintained through 1 month, and at 3 months,
PREOPERATIVE MEASUREMENTS
a significant difference persisted at the 20/16 level.
Achieving optimal results demands a commitment to
Unpublished studies my colleagues and I conducted
excellence in every detail, including the preoperative
at the Naval Medical Center in San Diego also demonrefractions. During both the manifest and wavefront
strated statistically significant differences between the
refractions, the patient should have a healthy tear film, fix- number of eyes treated with a femtosecond laser versus
ate properly, and not accommodate. The manifest refraca microkeratome that achieved 20/16 and 20/12.5
tion can be made more efficient and more accurate by
UCVA. Other studies have demonstrated a significant
using the refraction obtained with an aberrometer, such as increase in higher-order aberrations among eyes with
the WaveScan (Abbott Medical Optics Inc.), as a starting
flaps created by a mechanical microkeratome but not in
point. I have found that, when the manifest cylinder does
eyes with flaps made using the IntraLase FS laser.8,9
These subtle differences matter. Patients with 20/12.5
not match the wavefront (not an uncommon occurrence),
24 ADVANCED OCULAR CARE NOVEMBER/DECEMBER 2010
REFRACTIVE SURGERY
“Simply treating the ocular surface
can actually reduce patients’ need
for an enhancement.”
UCVA are happier than those with 20/16 UCVA, who in
turn are more satisfied than their 20/20 counterparts.
POSTOPERATIVE MANAGEMENT
Aggressive lubrication of the ocular surface with artificial tears and the eye care specialist’s attention to any signs
or symptoms of dry eye are key during the postoperative
period. Even mild dry eye can reduce visual results from
LASIK at this stage. Simply treating the ocular surface can
actually reduce patients’ need for an enhancement.
The most important thing any surgeon can do to improve outcomes is to track them. Recording outcomes
consistently and then using those data to personalize
nomograms and assess the effect of new technology are
the best way to ensure continued improvement.
CONCLUSION
There have been phenomenal advances in laser vision
correction during the last decade. They include improved
diagnostic equipment and a greater understanding of the
proper selection of surgical candidates. The refractive procedures performed today—particularly creation of the
LASIK flap with a femtosecond laser and wavefront-guided
treatments—have unparalleled safety and effectiveness,
and they have raised the bar for outcomes. ■
Steven C. Schallhorn, MD, is the global medical director of Optical Express. He is a consultant to Abbott Medical Optics Inc. Dr. Schallhorn
may be reached at [email protected].
1. Schallhorn SC,Venter JA.One-month outcomes of wavefront-guided LASIK for low to moderate myopia with the
Visx Star S4 laser in 32,569 eyes.J Refract Surg.2009;25(suppl):S634-641.
2. Tanzer DJ.Bringing LASIK to the next level with advanced femtosecond technology:a clinical comparison.Paper
presented at:The XXVII Congress of the ESCRS;September 15,2009;Barcelona,Spain.
3. Albietz JM,Lenton LM,McLennan SG.Chronic dry eye and regression after laser in situ keratomileusis for myopia.J
Cataract Refract Surg.2004;30:675-684.
4. Schallhorn SC,Farjo AA,Huang D,et al;American Academy of Ophthalmology.Wavefront-guided LASIK for the
correction of primary myopia and astigmatism:a report by the American Academy of Ophthalmology.
Ophthalmology.2008;115(7):1249-1261.
5. Lee HK,Choe CM,Ma KT,Kim EK.Measurement of contrast sensitivity and glare under mesopic and photopic conditions following wavefront-guided and conventional LASIK surgery.J Refract Surg.2006;22(7):647-655.
6. Schallhorn SC,Tanzer DJ,Kaupp SE,et al.Comparison of night driving performance after wavefront-guided and
conventional LASIK for moderate myopia.Ophthalmology.2009;116(4):702-709.
7. Tanna M,Schallhorn SC,Hettinger KA.Femtosecond laser versus mechanical microkeratome:a retrospective comparison of visual outcomes at 3 months.J Refract Surg.2009;25:S668-S671.
8. Tran DB,Sarayba MA,Bor Z,et al.Randomized prospective clinical study comparing induced aberrations with
IntraLase and Hansatome flap creation in fellow eyes:potential impact on wavefront-guided laser in situ keratomileusis.J Cataract Refract Surg.2005;31(1):97-105.
9. Chan A,OU J,Manche EE.Comparison of the femtosecond laser and mechanical keratome for laser in situ keratomileusis.Arch Ophthalmol.2008;126(11):1484-1490.
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