Transcript The effect of laser in situ keratomileusis on refraction

Hidemasa Torii, MD, Kazuno Negishi, MD, Murat Dogru, MD,
Takefumi Yamaguchi, MD, Nanae Kawaguchi, MD,
Megumi Saiki, CO, and Kazuo Tsubota, MD
Authors have no financial interest
Department of Ophthalmology
Keio University School of Medicine, Tokyo, Japan
ASCRS Symposium & Congress, San Francisco, 2009
Purpose
 To report the three-year observation of a patient who
underwent laser in situ keratomileusis (LASIK) with an
extremely thin residual stromal bed (below 100 μm).
Case report
Case: 35-year-old male
Chief complaint: Visual disturbance in the right eye
Onset and course: He was referred to our clinic for a second opinion.
He had undergone bilateral LASIK using a 15-KHz IntraLase
femtosecond laser microkeratome (Advanced Medical Optics, Irvine,
CA) 1 week previously.
Onset and course (continued)
The patient stated that his preoperative corrected vision was 20/20 or
above in each eye, and he had blurry vision in his right eye
immediately after LASIK, while the uncorrected visual acuity (VA)
in his left eye increased. Our repeated requests to retrieve the
patient’s surgical data from the referral clinic were unsuccessful.
The surgeon who performed LASIK prescribed 0.1% betamethasone
sodium phosphate and 0.1% sodium hyaluronate eye drops. We
continued the medication.
Past history: unremarkable
Family history: unremarkable
1st visit: 7 days after LASIK
BCVA (best corrected visual acuity)
Right eye 20/160 (-1.0 -1.5 X100)
Left eye 20/12.5
Intraocular pressure
10 mmHg both eyes
Biomicroscopic examination
There was a severe diffuse inflammatory reaction at the flap
interface in his right eye and no abnormal findings in the left
eye. The right eye was diagnosed with severe DLK.
The anterior chamber, lens, vitreous, and fundus appeared
normal in both eyes.
The corneal endothelial cell density
Right eye 3,144 cells/mm2
Left eye 3,067 cells/mm2
1st visit: 7 days after LASIK (continued)
Pentacam examination (Oculus Optikgerate GmbH, Wetzlar, Germany)
Pentacam measurements showed a total central corneal
thickness of 535 μm in the right eye and 537 μm in the left eye,
and there was a diffuse high pixel intensity layer (arrow) in the
deep stroma of the right eye which we assumed to be the flap
interface. The distance of the high pixel intensity layer from
the central corneal surface was 470 μm as measured by
Pentacam . There were no remarkable findings in the left eye.
right eye
14 months after LASIK
BCVA (best corrected visual acuity)
Right eye 20/66
Left eye 20/10
Intra ocular pressure
13 mmHg both eyes
Biomicroscopic examination
The examination of the right eye
showed a scar (arrow) in the deep
stroma.
Pentacam examination
The high pixel intensity layer in
the deep stroma (assumed to be
the flap interface) persisted.
right eye
3 years after LASIK
BCVA (best corrected visual acuity)
Right eye 20/66
Left eye 20/10
Intraocular pressure
Right eye 12 mmHg
Left eye 11 mmHg
Biomicroscopic examination
The examination of the right eye
still showed the deep stromal
scar (arrow).
right eye
Pachymetry map and corneal topography
of the right eye
A: 14 months postoperatively
B: 3 years postoperatively
The pachymetry map and
the corneal topography of
the right eye were almost
stable
during
the
observation period.
Discussion
 The reported case was followed for 3 years after LASIK with an
extremely thin residual bed.
 There were two noteworthy points in this case as follows:
 DLK in the early postoperative period which caused formation of a stromal
scar.
 The presence of an extremely thin residual bed that might have led to
iatrogenic keratectasia.
 In this case, we could not obtain information on the amount of
laser energy used during LASIK; however, severe DLK might
develop even when the energy level is within the standard range
(Javaloy et al. 2007). Further studies on association between the
depth of the interface and inflammation after LASIK should be
carried out.
Discussion (continued)
 A thin residual bed is a major risk factor for the development of
post-LASIK ectasia.
 In this case, an extremely thick flap was created for unknown
reasons despite using a laser keratome, which is able to create
predictably thin corneal flaps, and the estimated central residual
bed thickness in this eye was 65 μm.
 Randleman et al. reported that the mean time to the development
of ectasia is 16.3 months (range, 1–45 months) and most cases
of ectasia develop within the first 6 months after surgery;
although some eyes develop delayed-onset ectasia
(Ophthalmology 2003).
Discussion (continued)
In this case, the right eye remained stable topographically and
the visual acuity remained stable for more than 3 years despite a
very thin residual bed.
We speculate that the corneal stromal scar after DLK might have
stiffened the cornea and contributed to the stability of the corneal
shape; a hypothesis which needs to be verified in future studies.
We believe that longer follow-up is necessary in our case and
such cases to identify late-onset keratectasia.