Download A Prospective, Randomized, Contralateral Eye Comparison of

A Prospective, Randomized, Contralateral
Eye Comparison of Epithelial Laser in
situ Keratomileusis and Photorefractive
Keratectomy in Eyes Prone to Haze
Tamer O. Gamaly, FRCS; Alaa El Danasoury, MD, FRCS; Akef El Maghraby, MD
ABSTRACT
PURPOSE: To compare refractive outcome, subepithelial haze, and pain after epithelial laser in situ keratomileusis (epi-LASIK) and photorefractive keratectomy
(PRK).
METHODS: In this prospective, randomized study,
32 eyes of 16 patients were treated for myopia with
epi-LASIK (epi-LASIK group) in one eye and PRK in the
fellow eye (PRK group). All patients underwent ablation
using the NIDEK EC-5000 CX II excimer laser platform.
Mean patient age was 24.8 years (range: 19 to 35
years). Mean preoperative manifest refractive spherical equivalent (MRSE) was ⫺2.76 diopters (D) (range:
⫺1.00 to ⫺4.88 D). Refractive outcome, subepithelial
haze, and pain out to 6 months postoperatively were
compared between groups.
RESULTS: At 6 months postoperatively, the mean MRSE
was ⫺0.22⫾0.27 D (range: 0.25 to ⫺0.88 D) in the
epi-LASIK group and ⫺0.23⫾0.29 D (range: 0.50 to
⫺1.125 D) in the PRK group. There was no statistically
significant difference in the refractive outcomes between
groups. By postoperative day 4, 18% of the epi-LASIK
group and 7% of the PRK group achieved the final uncorrected visual acuity (UCVA). On day 1 postoperatively,
14% fewer patients in the PRK group experienced pain
compared with the epi-LASIK group. On postoperative
day 2, 36% fewer patients in the epi-LASIK group experienced pain. Seventy-one percent of patients in the
epi-LASIK group and 36% of patients in the PRK group
had no haze postoperatively.
CONCLUSIONS: Epi-LASIK and PRK produced similar
refractive outcome. Patients who underwent epi-LASIK
experienced faster recovery of vision, less haze, and less
pain. [J Refract Surg. 2007;23:S1015-S1020.]
L
aser in situ keratomileusis (LASIK) is the most common surgical procedure for the treatment of refractive
errors. However, some disadvantages are associated
with LASIK including flap striae, epithelial ingrowth, and
corneal ectasia.1,2 Furthermore, patients with thin corneas
can be at risk for corneal ectasia postoperatively, because the
structural stability of the cornea can be compromised due to
inadequate residual stromal bed thickness. Patients with steep
corneal curvatures or suspicious topographies are at risk for
complications during or after LASIK and may be better candidates for surface ablation procedures such as photorefractive
keratectomy (PRK), laser epithelial keratomileusis (LASEK),
or epithelial laser in situ keratomileusis (epi-LASIK).
Photorefractive keratectomy is safe and effective for low to
moderate myopia, although it has some disadvantages such as
postoperative pain, slow visual recovery, prolonged steroid
therapy, risk of haze, and myopic regression.3,4 Haze has been
reported for treatments as low as 2.50 diopters (D) and may be
more prevalent in certain populations with brown irides.5,6
Laser epithelial keratomileusis was developed to reduce
some of the complications associated with PRK, such as postoperative pain and haze. Laser epithelial keratomileusis is
safe, efficacious, and predictable. However, there is no standardized procedure for this surgical technique, and concerns
about the effect of alcohol on the epithelium remain.3,7
Epi-LASIK is a surface procedure that automates the separation of the epithelium mechanically. Unlike with LASEK,
alcohol is not required with epi-LASIK, and up to 85% of the
epithelium remains viable.8
This study assessed the safety, efficacy, stability, visual
recovery, and patient satisfaction of epi-LASIK for the treatment of myopia with or without astigmatism using the Moria
Epi-k (Moria SA, Antony, France) automated epithelial sepaFrom Magrabi Eye Hospital, Muscat, Sultanate of Oman.
The authors have no proprietary interest in the materials presented herein.
Presented at the NIDEK NAVEX Seminar, XI Congress of the Middle East African
Council of Ophthalmology; March 28, 2007; Dubai, United Arab Emirates.
Correspondence: Tamer O. Gamaly, FRCS, Magrabi Eye Hospital 106, Rumaila
Building, Al Nahda St, PO Box 513, Postal Code 112, Muscat, Sultanate of
Oman. Tel: 968 24568870; Fax: 968 24568874; E-mail: [email protected]
Journal of Refractive Surgery Volume 23 November (Suppl) 2007
S1015
Epi-LASIK vs PRK/Gamaly et al
rator and the NIDEK EC-5000 CX II excimer laser platform (NIDEK Co Ltd, Gamagori, Japan).
PATIENTS AND METHODS
In this prospective, randomized, contralateral eye
study, 32 eyes from 16 patients were treated with epiLASIK in one eye (epi-LASIK group) and PRK in the
fellow eye (PRK group). The 16 patients were undergoing treatment for myopia with or without astigmatism
using the Moria Epi-K automated epithelium separator
and the NIDEK EC-5000 CX II excimer laser platform.
Mean patient age was 24.8 years (range: 19 to 35 years),
and 69.7% of patients were male. Mean preoperative
manifest refractive spherical equivalent (MRSE) was
⫺2.76 D (range: ⫺1.00 to ⫺4.88 D).
INCLUSION AND EXCLUSION CRITERIA
To be included in the study, patients had to be at
least 18 years of age, have a documented stable refraction for the past 12 months, and be poor candidates
for LASIK because of thin corneas (less than 500 µm).
Exclusion criteria included unstable refraction, keratoconus, suspected keratoconus, pellucid marginal
degeneration, previous ocular surgery, and active
ocular or systemic disease that could affect corneal
wound healing.
Patients were randomized into one of two groups
using a randomization schedule generated by a biostatistician.
All patients were informed of the risks and complications associated with the surgeries and alternatives to vision correction. All patients in the study
signed an informed consent. The study protocol was
approved by the Magrabi Hospital Human Research
Committee.
PREOPERATIVE AND FOLLOW-UP EVALUATION
All patients underwent a baseline ophthalmic
examination and postoperative examination daily at
day 1 to day 7, followed by examinations at 2 weeks, 1
month, 3 months, and 6 months. Snellen uncorrected
visual acuity (UCVA), Snellen best spectacle-corrected
visual acuity (BSCVA), and manifest and cycloplegic
refractions were measured. Slit-lamp examination,
corneal topography and aberrometry using the NIDEK
OPD-Scan (NIDEK Co Ltd), corneal pachymetry using
the DGH pachymeter (DGH Technologies Inc, Exton,
Pa), Goldmann tonometry, and a dilated fundus examination also were carried out. Postoperatively, all patients underwent the same preoperative evaluations
with the exception of a dilated fundus examination,
which was conducted only at month 6 or earlier if
indicated. During the first week, patients were asked
S1016
whether they experienced pain and which eye had
more pain. All patients were masked to the procedure
that each eye underwent.
SURGICAL TECHNIQUES
Epi-LASIK. Preoperatively, the eye undergoing surgery was anesthetized using topical anesthetic. A lid
speculum was inserted to allow maximum exposure
of the globe. Corneal thickness was measured using
an ultrasound probe. Three gentian violet marks were
placed on the peripheral cornea for better visualization
of the epithelial flap. A suction ring with a 7.50-mm
stop was placed on the eye, and forward movement
was initiated with copious irrigation of balanced salt
solution. Once the forward pass was completed, the reverse pass was initiated again with copious irrigation
using balanced salt solution. The epithelial flap was
reflected nasally, the cornea dried using a sterile surgical sponge, and the ablation delivered. Proper alignment of the eye with the laser was achieved with the
laser-aiming diode centered on the first Purkinje image
on the patient’s pupil. Patients fixated on a red fixation light, coaxial with the surgeon’s line of vision and
the excimer laser beam, throughout the ablation. The
flap was repositioned, and the interface was irrigated
with balanced salt solution to remove any debris. The
cornea was dried with a surgical sponge and a bandage
contact lens was placed on the eye.
Photorefractive Keratectomy. Eyes of patients undergoing PRK were also anesthetized using topical
anesthetic. A lid speculum was inserted to allow
maximum exposure of the globe. Corneal thickness
was measured using an ultrasound probe. The central
8.00 mm of the cornea was marked. Mechanical debridement of the epithelium of the central 8.00 mm
was performed using a Beaver blade without damaging Bowman’s membrane. Excimer ablation was
performed according to a customized nomogram
internal to the NIDEK EC-5000 CX II excimer laser
platform. Proper alignment of the eye with the laser
was achieved with the laser-aiming diode centered
on the first Purkinje image on the patient’s pupil. Patients fixated on a red fixation light, coaxial with the
surgeon’s line of vision and the excimer laser beam,
throughout the ablation. The surface of the cornea
was irrigated with balanced salt solution to remove
any debris. A bandage contact lens was placed on
the eye. Postoperatively, patients were instructed
to instill the topical antibiotic/topical nonsteroidal anti-inflammatory medication four times a day
for 1 week and artificial tears four times a day for 1
month. The bandage contact lens was removed after
the epithelium healed.
journalofrefractivesurgery.com
Epi-LASIK vs PRK/Gamaly et al
Figure 1. Manifest refractive spherical
equivalent 6 months postoperatively (N=24
eyes).
Figure 2. Uncorrected visual acuity 6
months postoperatively (N=24 eyes).
OUTCOMES ANALYSIS
Refractive outcomes for both epi-LASIK and PRK
were compared. In addition, postoperative pain experienced with both procedures was compared, as was
postoperative corneal haze. All outcomes are reported
at 6 months postoperatively, with the exception of
postoperative pain, bandage contact lens removal,
visual recovery, and corneal haze.
RESULTS
No complications occurred during surgery in either group. Six months postoperatively, 75% (24/32)
of patients were available for follow-up. All patients
in the epi-LASIK group were within ⫺1.00 D of the
intended MRSE at 6 months postoperatively (Fig 1).
Journal of Refractive Surgery Volume 23 November (Suppl) 2007
The postoperative UCVA was similar in both the PRK
and epi-LASIK groups (Fig 2). No eye in either group
lost more than 1 line of BSCVA 6 months postoperatively (Fig 3). Stability was similar for both groups
(Fig 4).
All patients in both groups were within ⫺1.00 D
of the intended MRSE at 6 months postoperatively. Twelve (68.75%) eyes were between plano and
⫺0.50 D in the epi-LASIK group compared with 11
(62.50%) eyes in the PRK group. Two (12.50%) eyes
were between ⫹0.50 and ⫹0.10 D in the epi-LASIK
group compared with 3 (18.75%) eyes in the PRK
group. Three (18.75%) eyes in both groups were between ⫺0.51 and ⫺1.00 D (see Fig 1). No patient had a
⬎0.50-D change in MRSE between 3 and 6 months.
S1017
Epi-LASIK vs PRK/Gamaly et al
Figure 3. Safety at 6 months postoperatively (N=24 eyes).
Figure 4. Change in mean MRSE over time
(N=24 eyes).
Figure 5. Visual recovery at 6 months.
This graph shows the percent of eyes that
achieved their final UCVA at each examination (N=24 eyes).
S1018
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Epi-LASIK vs PRK/Gamaly et al
Figure 6. Subepithelial haze at 6 months
postoperatively (N=24 eyes).
Figure 7. Postoperative pain as reported by
patients (N=24 eyes).
Uncorrected visual acuity was 20/20 or better in
12 (75%) eyes in the epi-LASIK group, whereas 11
(68.75%) eyes achieved the same level in the PRK
group. Fifteen (93.75%) eyes had an UCVA of 20/25
or better in the epi-LASIK group, and 14 (87.50%) eyes
reached this level in the PRK group. Fifteen (93.75%)
eyes in both groups had an UCVA of 20/30 or better.
All patients in both groups read 20/40 or better at distance without correction (see Fig 2).
In the early postoperative period (less than 1 week),
visual recovery in the epi-LASIK group was faster than
in the PRK group (Fig 5). Fewer eyes in the PRK group
had no subepithelial haze (haze), and no eyes in the
epi-LASIK group had grade 1 or higher haze 6 months
postoperatively (Fig 6).
The results of a subjective patient questionnaire
about postoperative pain in the first 4 postoperative
days are plotted in Figure 7.
The average time of contact lens removal was 4 days
(50% of patients) (Fig 8).
Journal of Refractive Surgery Volume 23 November (Suppl) 2007
DISCUSSION
Results of the eye study reported here show that
there was less haze, faster visual recovery, and less
pain in the eyes that underwent epi-LASIK compared
with the fellow eyes that underwent PRK. However,
MRSE, safety, and stability did not differ between
groups. Both epi-LASIK and PRK were equally safe, effective, and predictable.
Patients who are not candidates for LASIK often
undergo a surface ablation procedure such as PRK,
LASEK, or, recently, epi-LASIK. However, haze is a
possible unpredictable complication. Based on earlier
studies of PRK, it appears that racial factors may play a
role in the development of haze.5,6 Postoperative haze
reduces visual quality.9 A number of concerns about
the use of alcohol and mitomycin C (MMC) during
LASEK and PRK remain. The devitalization of epithelial cells caused by alcohol and corneal edema, recurrent erosion, melting, perforation, and endothelial cell
loss caused by MMC have been reported.3,7,10-13
S1019
Epi-LASIK vs PRK/Gamaly et al
Figure 8. Average days to removal of bandage contact lens (N=24 eyes).
The significant absence of corneal haze in the epiLASIK group makes this procedure a suitable alternative to both PRK and LASEK. The epithelial separation
during the epi-LASIK procedure occurs just below the
lamina densa and does not require alcohol for separating.
Thus, the majority of epithelial cells remain vital postoperatively.8 The absence of haze in the majority of eyes
that underwent epi-LASIK indicates that the use of MMC
may not be warranted with this procedure.
Other advantages of epi-LASIK include the preservation of stromal stability and decreased severing
of corneal nerves as well as the potential to decrease
the future risk of ectasia due to the increased residual
bed thickness. One disadvantage of epi-LASIK is the
potential need for a full epithelial flap cut; however,
such procedures can be converted to PRK. Another
disadvantage is a deeper-than-intended separation at
the level of the stroma. In our early cases (not included
in this study), one such separation did occur, due to
improper assembly of the epi-K epithelial separator.
However, the cornea healed without adverse sequelae
or loss of BSCVA by 1 month postoperatively.
Due to the friable nature of the epithelial sheet,
meticulous handling is required.
One disadvantage of this study is the small sample
size; however, we believe the randomized, contralateral eye study design increases the reliability of the
results because it eliminates differences in individual
wound-healing effects.
We found epi-LASIK and PRK similar in efficacy and
predictability in reducing myopia with or without astigmatism. Epi-LASIK reduces the risk of corneal haze, is less
painful, and provides faster visual recovery than PRK.
S1020
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