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Laser-Assisted In Situ Keratomileusis for Patients With Dry Eye
Ikuko Toda, MD;
Naoko Asano-Kato, MD;
Yoshiko Hori-Komai, MD;
Kazuo Tsubota, MD
Arch Ophthalmol. 2002;120:1024-1028.
ABSTRACT
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Objective To evaluate the efficacy and safety of laser-assisted in situ keratomileusis
(LASIK) in patients with preoperative dry eye.
Methods We divided the 543 eyes that underwent LASIK into the following 3 groups:
eyes with definite dry eye (DE group), with probable dry eye (PDE group),
and without dry eye (NDE group). We evaluated visual outcome, dry-eye status,
and complications.
Outcome Measures We compared uncorrected and best-corrected visual acuity, manifest refraction,
symptoms, tear function, ocular surface abnormality, complications, corneal
sensitivity, endothelial cell count, and patient satisfaction among the groups.
Results We found no significant differences among the groups in uncorrected
and best-corrected visual acuity, manifest refraction, and patient satisfaction.
A dry-eye symptom, dryness, was more severe in the DE than the NDE group after
LASIK. The mean results of the Schirmer test with anesthesia and tear breakup
times were significantly lower and the fluorescein score was higher in the
DE than the NDE groups after LASIK. We found no differences in the incidence
of complications among the groups. Corneal sensitivity was recovered within
6 months after LASIK in the DE and PDE groups and within 3 months in the NDE
group.
Conclusions The efficacy and safety of LASIK were not affected by preexisting dry
eye. However, preexisting dry eye is a risk factor for severe postoperative
dry eye with lower tear function, more vital staining of the ocular surface,
and more severe symptoms.
INTRODUCTION
LASER-ASSISTED in situ keratomileusis (LASIK) is an effective procedure
to correct refractive error, which induces little wound-healing response and
inflammation in the corneal tissue. These factors contribute to stable postoperative
refraction, excellent predictability, quick recovery of visual acuity, and
no haze formation. However, some patients still experience regression, epithelial
ingrowth, or postoperative inflammatory reactions such as diffuse lamellar
and microbial keratitis.1-2
In general, good candidates for LASIK should have no ocular and systemic
diseases, including active uveitis, keratoconus, and diabetes mellitus, which
may adversely affect postoperative wound healing. Although dry eye is not
an absolute contraindication for LASIK, compromised tear function and ocular
surface may influence the outcome of LASIK. Patients often request refractive
surgery owing to contact lens intolerance caused by dry eye. A previous study
from our group reported that photorefractive keratectomy could be performed
safely on patients with contact lens intolerance due to dry eye as long as
reflex tearing was noted.3 Epithelial wound
healing, recovery of corneal sensitivity, and visual outcomes of these patients
were comparable with previously published data. It is expected that LASIK
can be performed safely on patients with dry eye because less epithelial wound-healing
response is involved postoperatively compared with photorefractive keratectomy.
However, LASIK has its own disadvantages, ie, the corneal nerves are cut by
making a flap and recovery time is increased4
when dry eye itself develops.5-6
Thus, we investigated whether the outcome, including visual performance and
incidence of complications, was comparable between subjects with and without
preoperative dry eye.
Dry eye is a major reason for patients to consider LASIK, and it is
a common post-LASIK complication.2, 5-6
Our previous study demonstrated that post-LASIK dry eye develops with compromised
tear function and ocular surface for at least 1 month after surgery.7 Tear function and dry-eye symptoms improve within
several postoperative months in most cases; however, some patients still have
dry eye 1 year after undergoing LASIK. Although the mechanisms for post-LASIK
dry eye are unclear, more severe post-LASIK dry eye may develop in patients
with preoperative dry eye for longer periods compared with subjects without
preoperative dry eye. The purpose of this study was to investigate whether
(1) preoperative dry eye may affect the visual outcome and incidence of complications
after LASIK, and (2) preoperative dry eye is a risk factor for severe postoperative
dry eye.
PATIENTS AND METHODS
We enrolled 543 eyes of 290 consecutive patients (mean age, 33.1 years)
who underwent LASIK from January 1, 1998, through March 31, 2000, at the Minamiaoyama
Eye Clinic, Tokyo, Japan, in this study. These eyes were divided into the
following 3 groups on the basis of preoperative dry-eye status: eyes with
definite dry eye (DE group; 111 patients and 168 eyes), with probable dry
eye (PDE group; 153 patients and 300 eyes), and without dry eye (NDE group;
49 patients and 75 eyes). Dry eye was diagnosed according to the modified
criteria established by the Japanese Dry Eye Association.8
The subcriteria consisted of results of a Schirmer test with anesthesia of
no greater than 5 mm, and/or tear breakup time (BUT) of no greater than 5
seconds, and a fluorescein score of at least 1 and/or a rose bengal score
of at least 3. Briefly, patients who satisfied both subcriteria were diagnosed
as having DE; those who satisfied 1 of 2 subcriteria, PDE. The mean ±
SD preoperative refraction in spherical equivalent was -7.24 ±
3.09 diopters (D) in the DE group, -6.82 ± 2.85 D in the PDE
group, and -6.5 ± 2.54 D in the NDE group.
For the surgical procedure, a corneal flap was created with a microkeratome
(LSK One; Moria, Antony, France; or MK-2000; NIDEK Co, Ltd, Gamagori, Japan),
and laser ablation was performed using an excimer laser (Apex-plus; Summit
Technology, Walnut Creek, Calif; or EC-5000; NIDEK Co, Ltd). Hyaluronate sodium
(Hyalein; Santen Pharmaceutical Co, Ltd, Osaka, Japan) and balanced salt solution
(BSS Plus; Alcon Laboratories, Ft Worth, Tex) were frequently applied intraoperatively
to prevent dehydration of the ocular surface. Immediately after surgery, high
viscous methylcellulose (Lacryvisc; Alcon, Hünenberg, Switzerland) was
instilled in the eye and patients were asked to close their eyes and rest
for 15 minutes. Low-dose corticosteroids (0.1% fluorometholone [Flumetholon;
Santen Pharmaceutical Co, Ltd]), antibiotics (ofloxacin [Tarivid; Santen Pharmaceutical
Co, Ltd]), and 0.3% hyaluronate sodium eyedrops were prescribed 5 times a
day. Eyedrop therapy was discontinued at 1 week postoperatively. Hyaluronate
sodium eyedrops remain on the ocular surface longer than isotonic sodium chloride–based
artificial tears9 and prevent the symptoms
and oular surface damage caused by post-LASIK dry eye.7
To evaluate the efficacy of the LASIK correction, uncorrected (UCVA)
and best-corrected visual acuity (BCVA) and manifest refraction in the spherical
equivalent were examined at 1, 3, and 6 months and 1 year after LASIK.
For the dry-eye examination, we assessed dry-eye symptoms and performed
a Schirmer test with anesthesia, measurement of tear BUT, and fluorescein
and rose bengal staining of the ocular surface. For subjective symptoms of
dry eye, dryness was graded by the patients according to the following scale:
0 indicates none; 1, mild; 2, moderate; 3, strong; and 4, very strong. The
Schirmer test with anesthesia was performed 5 minutes after instilling 10
µL of 0.5% fluorescein sodium and 0.4% benoxinate hydrochloride into
the conjunctival sac. The Schirmer strip was placed for another 5 minutes,
and the length of the wet portion was measured. Vital staining of the ocular
surface was performed by instillation of 2 µL of preservative-free mixed-dye
solution (1% rose bengal and 1% fluorescein) into the conjunctival sac.10 Fluorescein staining results were graded from 0 to
3 for the upper, middle, and lower thirds of the cornea. Rose bengal staining
results were graded from 0 to 3 for the temporal conjunctiva, cornea, and
nasal conjunctiva. Staining was graded by the extent as 0 for negative; 1,
scattered minute; 2, moderate spotty; and 3, diffuse blotchy. The tear BUT
was measured as the number of seconds between the last complete blink and
the first disturbance of the precorneal tear film.
The safety of LASIK was evaluated by incidence of intraoperative (epithelial
defect, bleeding, and flap repositioning) and postoperative (recurrent erosion,
diffuse lamellar keratitis, microstriae, and epithelial ingrowth) complications,
corneal sensitivity, loss of BCVA, and endothelial cell count. Corneal sensitivity
was measured with an esthesiometer (Cochet-Bonnet; Luneau Ophthalmologie,
Chartres, France) consisting of a nylon filament 60.0 mm long and 0.12 mm
in diameter. Patients were asked to look straight ahead and to indicate when
they believed that the top of the nylon filament touched the cornea. The measurement
was started at 60.0 mm, and the length of the filament was decreased by 5.0-mm
increments to increase its rigidity. The corneal sensitivity was defined as
the length of the filament that produced a first positive response. We photographed
the corneal endothelium using a specular microscope (Konan Medical, Inc, Tokyo),
and calculated mean cell density.
We surveyed overall patient satisfaction with the outcome of LASIK,
using a grade of 1 for very satisfied; 2, satisfied as expected; 3, not very
satisfied; and 4, regretted undergoing LASIK.
We performed statistical analysis by means of the t test, Wilcoxon rank sum test, or Kruskal-Wallis test. Values of P<.05 were considered statistically significant.
RESULTS
VISUAL OUTCOME
We found no significant differences among the DE, PDE, and NDE groups
in UCVA and BCVA, except at 1 month, when the UCVA was better in the NDE than
in the DE group (P = .03). Average postoperative
manifest refraction was within ±0.5 D in all groups at all follow-ups.
Manifest refractive deviation due to emmetropia was slightly larger in the
DE than in the NDE group at 3 months (-0.25 ± 0.76 vs 0.01 ±
0.55 D; P = .01), but we found no differences among
the groups at other follow-up points.
DRY-EYE CONDITION
We found significant differences between the DE and NDE groups in degree
of symptoms of dryness before LASIK and at 3 and 6 months and 1 year after
LASIK. Dryness was more severe in the PDE than in the NDE group at 6 months
and 1 year after LASIK (Figure 1).
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Figure 1. Dry-eye symptoms before and after
laser-assisted in situ keratomileusis (LASIK) in the groups with definite
(DE) and probable dry eye (PDE) and without dry eye (NDE). Asterisk indicates P<.01; dagger, P<.05; and
error bars, SD.
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The mean result of the Schirmer test with anesthesia was lower in the
DE and PDE groups compared with the NDE group at all follow-ups after LASIK
(Figure 2A). The tear BUT was shorter
in the DE than in the NDE groups before LASIK and at all the follow-ups after
LASIK, and the PDE group value was between those in the other groups (Figure 2B). For ocular surface abnormality,
the fluorescein score was higher in the DE than in the NDE group before LASIK
and at all follow-ups after LASIK, and staining intensity was between these
values in the PDE group (Figure 3A). The rose bengal score was higher in the DE and PDE groups than in the NDE
group preoperatively and at 3 months after LASIK (Figure 3B).
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Figure 2. Tear function before and after
laser-assisted in situ keratomileusis (LASIK) in the DE, PDE, and NDE groups.
A, Schirmer value. B, Tear breakup time (BUT). Asterisk indicates P<.01; dagger, P<.05; and error bars,
SD. Group names are explained in the legend to Figure 1.
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Figure 3. Vital staining of ocular surface
before and after laser-assisted in situ keratomileusis (LASIK) in the DE,
PDE, and NDE groups. A, Fluorescein score. B, Rose bengal score. Asterisk
indicates P<.01; dagger, P<.05;
and error bars, SD. Group names are explained in the legend to Figure 1.
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SAFETY
Intraoperative epithelial defect occurred in 4 eyes in the NDE group
(P = .2). Fifty-eight eyes (34.5%) in the DE, 78
(26.0%) in the PDE, and 20 (26.7%) in the NDE groups had bleeding from the
pannus (P = .5). Flap repositioning was performed
immediately after surgery owing to flap folds or dislocated flaps in 4 eyes
(2.4%) in the DE, 11 (3.7%) in the PDE, and 2 (2.7%) in the NDE groups (P = .7). We found no significant differences in the incidence
of postoperative complications, ie, epithelial ingrowth of 6 eyes (2.0%) in
the PDE group, diffuse lamellar keratitis of 1 eye (0.6%) in the DE group,
microstriae of 5 eyes (3.0%) in the DE and 8 eyes (2.7%) in PDE groups, and
no recurrent corneal erosion.
Loss of BCVA of more than 2 lines was observed in 2 eyes (1.2%) in the
DE, 7 (2.3%) in the PDE, and 1 (1.3%) in the NDE groups (P = .4) at 1 year after LASIK.
Corneal sensitivity recovered to preoperative levels within 6 months
after LASIK in the DE and PDE groups and within 3 months in the NDE group
(Figure 4). However, no statistical
difference was found among the groups at any follow-ups. Endothelial cell
count was unchanged after LASIK in all groups.
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Figure 4. Corneal sensitivity before and
after laser-assisted in situ keratomileusis (LASIK) in the DE, PDE, and NDE
groups. Asterisk indicates P<.01; dagger, P<.05; and error bars, SD. The P
values for the differences between the groups at the same follow-ups are shown
at the bottom. Group names are explained in the legend to Figure 1.
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PATIENT SATISFACTION
We found no significant differences in satisfaction among the groups
at 3 and 6 months and 1 year after surgery.
COMMENT
Dry eye is a common disease that often causes patients to consider LASIK
because of difficulty wearing contact lenses. Among all patients who underwent
LASIK in our clinic before March 31, 2000, 35.2% and 41.2% of patients were
diagnosed as having DE and PDE, respectively, according to the modified criteria
of the Japanese Dry Eye Association.8 Thus,
more than 75% of the patients undergoing LASIK have preoperative dry eye.
In the present report, we compared the outcome of LASIK among patients who
had DE, PDE, and NDE.
The efficacy of LASIK, determined by means of postoperative UCVA, BCVA,
and manifest refraction, was almost comparable in the 3 groups. However, UCVA
at 1 month and manifest refraction at 3 months were better in the NDE than
in the DE group. We speculate that these differences were due to slight differences
in the amount of correction between the groups. The mean refractive correction
was -7.20 D in the DE group and -6.47 D in the NDE group (P = .07).
Tear function and ocular surface condition determined by results of
the Schirmer test, tear BUT, and rose bengal and fluorescein stainings were
more compromised after LASIK in the DE group compared with the NDE group.
This finding suggests that patients with preoperative dry eye have more severe
post-LASIK dry eye compared with the NDE group. The examination data of patients
in the PDE group yielded values that were between those of the DE and NDE
groups. A typical dry-eye complaint, dryness, was more marked in the DE group;
however, the differences among all groups were not significant at 1 month
after LASIK, because this symptom temporarily increased in the NDE group and
returned to preoperative levels by the follow-up. In contrast, the subjective
score of dryness was more severe and unchanged in the DE group throughout
the follow-up. These data may indicate that preoperative dry eye is a risk
factor for severe postoperative dry eye.
The precise mechanism for post-LASIK dry eye is not clear. Wilson11 suggested the term LASIK-induced
neurotrophic epitheliopathy (LNE) for a condition of transient ocular
surface abnormality, such as punctate keratitis and rose bengal staining of
the cornea after LASIK. They speculate that LNE is attributable to interruption
of sensory nerve input to the corneal epithelium, which may last for 6 months
or longer postoperatively. They also suggest that preexisting dry eye may
be a risk factor for LNE. Although tear function is not affected in this condition,
LNE and post-LASIK dry eye may be caused by the same mechanism of neurotrophic
damage. Our results in this study indicate that preexisting dry eye could
lead to postoperative uncomfortable symptoms caused by dry eye and/or LNE.
Epithelial problems during or after LASIK surgery were of biggest concern
in patients with preexisting dry eye. Although we treated some patients who
had severe ocular surface damage caused by dry eye with punctal plugs before
surgery, most of our patients underwent LASIK without any dry-eye pretreatment
except for artificial tears. Epithelial defect, recurrent erosion, and epithelial
ingrowth did not preferentially occur in patients with preoperative dry eye.
Incidence of other problems, such as flap dislocation, flap folds, microstriae,
and diffuse lamellar keratitis was not increased in patients with dry eye.
For long-term complications, we found no statistically singnificant difference
in the loss of BCVA between the groups. However, recovery of corneal sensitivity
was significantly slower in patients with dry eye. This finding may be explained
by dysfunction of tear dynamics in dry eye, because corneal sensitivity is
sometimes decreased in these patients.12 Alternatively,
delayed recovery of corneal nerves may be responsible for tear deficiency
in these patients. The other possibility is that the difference may be attributable
to the amount of corneal tissue ablation, which was increased in the DE group
in this study. Kim and Kim13 reported that
greater reduction of corneal sensitivity was observed in cases with deeper
ablation.
CONCLUSIONS
Our results indicate that the efficacy and safety of LASIK were not
affected by preexisting dry-eye status. With the proper ocular surface management,
patients with dry eye can be good candidates for LASIK. However, our results
also suggest that preexisting dry eye is a risk factor for severe postoperative
dry eye with lower tear function, more vital staining of the ocular surface,
and more severe dry-eye symptoms until 1 year after LASIK. Patients with dry
eye who expect complete resolution of their symptoms after LASIK with removal
of contact lenses should be warned that their dry-eye symptoms may persist
after LASIK. We have recently found that some patients complain of dry-eye
symptoms for more than 1 year after LASIK. The pathogenesis and risk factors
of such symptoms are now under investigation.
AUTHOR INFORMATION
Submitted for publication October 23, 2001; final revision received
March 19, 2002; accepted April 16, 2002.
We thank Chikako Sakai of the Minamiaoyama Eye Clinic for her assistance
in statistical analyses.
Corresponding author and reprints: Ikuko Toda, MD, Minamiaoyama Eye
Clinic, 2-27-25 Minamiaoyama, Minato-ku, Tokyo 107-0062, Japan (e-mail: ikuko{at}tka.att.ne.jp).
From the Minamiaoyama Eye Clinic, Tokyo, Japan (Drs Toda, Asano-Kato,
Hori-Komai, and Tsubota); and the Department of Ophthalmology, Tokyo Dental
College, Chiba, Japan (Dr Tsubota).
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