Copyright 2001 American Medical Association. All Rights Reserved.
Applicable FARS/DFARS Restrictions Apply to Government Use.2001
Laser-assisted in situ keratomileusis (LASIK) has become the most common
surgical option to correct myopia. Certain preexisting conditions are contraindications
for LASIK, and they include unstable vision, keratoconus, thin corneas, pregnancy,
and autoimmune diseases. A careful evaluation can help select the good candidates
and predict which patients will have a guarded outcome. We describe the clinical
and histologic features of a patient who underwent penetrating keratoplasty
due to progressively worsening vision from corneal ectasia after LASIK.
A 32-year-old woman came to the Refractive Surgery Center, Wilmer Eye
Institute, Baltimore, Md, seeking a second opinion after LASIK was done elsewhere.
Her chief complaint was that her vision had worsened since surgery and she
could not function anymore with any form of visual aids.
Her ocular history was significant for keratoconus suspected by 2 ophthalmologists
but not by the last physician who recommended and performed bilateral simultaneous
LASIK. Before LASIK, she wore rigid gas-permeable contact lenses until she
became intolerant to those.
During the preoperative evaluation, an autorefractor revealed keratometry
readings of 47.75 and 51.75 OD and 49.37 and 55.00 OS. Her manifest refraction
revealed a visual acuity of 20/25 OD with −11.25 + 3.75 × 085
and 20/70 OS with −13.00 + 3.75 × 080. Her best-corrected visual
acuity with rigid gas-permeable contact lenses was 20/20 OU. Preoperatively,
her central corneal pachymetry readings were 511 µm OD and 482 µm
OS, as obtained by a scanning slit measurement system (Orbscan Topography;
Bausch & Lomb, Inc, Rochester, NY). She underwent full-correction LASIK
in both eyes. One month postoperatively, the patient's best-corrected visual
acuity was 20/40 OD with −3.25 + 0.50 × 125 and 20/50 OS with −2.25
+ 0.75 × 85.
When we first examined the patient, 5 months after the surgery, her
best-corrected visual acuity was 20/200 OD with −10.50 + 0.50 ×
90 and 20/100 OS with −9.75 + 0.75 × 90. Her central corneal pachymetry
reading was 365 µm OU by ultrasonographic pachymetry. Corneal topography
revealed central steepening in both eyes (Humphrey Visual Instruments, San
Leandro, Calif) (Figure 1). Her
keratometry readings, as indicated by the corneal maps, reached 55 and 61
OD and 54 and 58 OS. No posterior corneal curvature measurements were obtained.
On slitlamp examination, she had well-centered LASIK flaps with nasal hinges
in both eyes. The corneal epithelium was dry centrally and stained with fluorescein.
The stroma appeared thin and bulging forward (Figure 2). The lamellar interface appeared clear in both eyes. The
rest of the anterior segment, including the anterior chambers, irides, and
lenses, appeared normal. Intraocular pressures were 11 mm Hg OU by applanation
tonometry. The results of her dilated retinal examination were unremarkable.
Despite punctal plugs and the hourly use of preservative-free tears with lubricating
ointment at night, her visual acuity continued to deteriorate. Corneal topography
revealed that the surface of the right eye was more irregular. A contact lens
fit was attempted, but the patient did not believe she could tolerate the
lenses. A diagnosis of corneal ectasia was made based on the progressive worsening
of the cornea together with central thinning as measured by pachymetry, and
penetrating keratoplasty was recommended because the cornea was too thin and
dry to tolerate any other intervention. The patient underwent an uncomplicated
corneal transplantation (8.0-mm donor size to 7.5-mm recipient size), and
corneal tissue was sent for histologic studies (Figure 3).
Corneal topography of the right
eye after laser-assisted in situ keratomileusis, showing central steepening.
S-merid indicates the distance from the vertex (large crosshair) and its location
on the semimeridian; CIM, corneal irregularity measure.
Slitlamp appearance of the cornea,
showing stromal thinning and bulging after laser-assisted in situ keratomileusis,
seen best just above the lower pupillary margin.
Section of the corneal button
showing the edge of the lamellar cut (lower right corner) and a paracentral
thin area (periodic acid–Schiff, original magnification ×3).
The light microscopy reveals one margin of the corneal flap with a discontinuity
of the Bowman layer and a slanted area of mild scarring (Figure 4). Looking at a central area, there is a faint delineation
between the flap and the remainder of the stroma (Figure 5). The flap area has a slight increase in cellularity compared
with the remainder of the stroma. Centrally, the cornea, including all layers,
measured 317 µm in thickness, and the flap measured 81.5 µm.
Discontinuity of the Bowman layer
and a slanted area of mild scarring (arrow) at one margin of the corneal flap
(periodic acid–Schiff, original magnification ×100).
Central area with a faint delineation
(arrow) between the flap and the remainder of the stroma (periodic acid–Schiff,
original magnification ×160).
Transmission electron microscopy showed the discontinuity of the Bowman
layer (Figure 6) and a zone of irregular
collagen with a slight increased number of fibrocytes in the plane between
the flap and the remainder of the stroma (Figure 7). There was no endothelial damage.
One margin of the corneal flap,
with discontinuity of the Bowman layer (arrow) and an area of scarring (asterisk)
(original magnification ×2200).
Central cornea with an area of
irregularity of the collagen and an increased number of fibrocytes (between
arrows) in a plane between the corneal flap and the remainder of the stroma
(original magnification ×8800).
This case represents an example of corneal ectasia after LASIK, for
which the underlying risk factors for ectasia appear to be a combination of
keratoconus, thin preoperative central corneas, and possibly a lamellar keratectomy.
Several cases of corneal ectasia after LASIK have been reported,1- 5
but only one report1 included pathologic
findings. The histologic features of our case echo previous light microscopic
features. However, to our knowledge, transmission electron microscopic features
have not been previously described. Even though the histopathologic changes
are consistent with the clinical findings, it is still the physical properties,
strength, and stability of the thin cornea after LASIK that need to be studied
to understand why some patients have a guarded outcome. Seitz et al6 studied the posterior corneal curvature changes
after LASIK, and concluded that increased negative keratometric diopters and
oblate asphericity of the posterior corneal curvature pointed toward early
keratectasia after LASIK. Until a better understanding of the biomechanical
properties of the corneal deformation is reached, certain general guidelines
should be followed. These include performing central corneal pachymetry and
corneal topographic imaging in the preoperative evaluation of every potential
refractive surgery patient and avoiding LASIK in patients whose final corneal
stromal bed thickness is less than 250 µm or who appear to have keratoconus.
Finally, corneal deformation and ectasia with a possible need for more corneal
surgery, including lamellar or penetrating keratoplasty, should always be
included as part of the informed consent.
The pathologic features of corneal ectasia include an interruption of
the Bowman membrane with mild anterior cellularity, a thinner stromal thickness,
and no endothelial damage.
Corresponding author: Walter J. Stark, MD, The Wilmer Eye Institute
at Greenspring Station, 10755 Falls Rd, Suite 110, Baltimore, MD 21093.
Jabbur NS, Stark WJ, Green WR. Corneal Ectasia After Laser-Assisted In Situ Keratomileusis. Arch Ophthalmol. 2001;119(11):1714-1716. doi: