Transcript Complications in refractive surgery

“Development of Unilateral Corneal Ectasia After PRK with Ipsilateral
Preoperative Forme Fruste Keratoconus”
Jacob Reznik, MD¹; James J. Salz, MD²; Alena Klimava, MS³.
1. Wilmer Ophthalmological Institute, Johns Hopkins University, Baltimore, MD, USA
2. Laser Vision Medical Associates, Cedars Sinai Medical Center, Los Angeles, CA, USA
3. The Johns Hopkins University School of Medicine, Baltimore, MD, USA
Corresponding author:
Jacob Reznik, MD
Wilmer Ophthalmological Institute
Johns Hopkins University
600 N. Wolfe Street, Wilmer B27
Baltimore, MD 21287
E-mail: [email protected]
Phone: (410)955-5700
Fax: (410)955-0046
The authors have no proprietary interest in the materials presented herein.
Abstract:
Purpose: To describe clinical and topographic features of a prominent keratectasia after photorefractive
keratectomy (PRK) in a patient with abnormal preoperative topography.
Methods: A 25-year-old man underwent bilateral uneventful PRK for moderate myopia of - 5.75 - 1.75 x
95 OD and - 7.50 -1.25 x 80 OS with BSCVA 20/25 OU. Preoperative corneal pachymetry was 500 μm
OD and 460 μm OS. The total calculated ablation depth was 70 μm in the right eye and 100 μm in the left
eye. Preoperative corneal topography revealed forme fruste keratoconus (FFK) OD with I-S ratio of 4.
Results: 5 years postoperatively, the patient developed unilateral inferior keratectasia OD with refraction
of + 0.50 - 5.50 x 90 with BSCVA of 20/100 and central pachymetry of 481 μm with inferior pachymetry
of 374 μm.
Conclusion: This case reports adds to the growing body of evidence in the ophthalmic literature suggesting
that patients with preoperative FFK or early keratoconus may develop clinically-significant progression of
corneal ectaisa after PRK.
Case report:
A 25-year-old man was evaluated for refractive surgery to correct moderate myopia. The patient denied
previous contact lens wear and his ocular history was otherwise unremarkable. No previous history of
chronic eye rubbing, other trauma, or atopy was reported. No family history of corneal ectasia was
reported. No signs of clinical keratoconus were seen on slit-lamp biomicroscopy. Dilated funduscopic
examination was within normal limits.
BSCVA was 20/25 in both eyes with a refraction of - 5.75 - 1.75 x 95 OD and - 7.50 - 1.25 x 80 OS.
Preoperative central corneal pachymetry was 500 μm OD and 460 μm OS.
Keratometry readings were 42.50/42.25 x 90 OD and 43.25/44.00 x 90 OS with no distortion of the
keratometer mires OU.
No clinical signs of keratoconus were observed with slit-lamp biomicroscopy in both eyes. Corneal
topography (Optikon 2000) was normal OS and abnormal OD with obvious inferior steepening and I-S
ratio of 4. (Figure 1). The abnormal topography was discussed with the patient. He was informed that
laser in situ keratomileusis (LASIK) was absolutely contraindicated secondary to abnormal topographic
findings. He was informed that if he agreed to PRK this might accelerate the progression of keratectasia
and if this did in fact happen, he would most likely require a hard contact lens and possibly even a
penetrating keratoplasty.
On 4/1/98, patient received -6.86 -0.75 X 180 excimer laser correction with the Visx Star laser (VISX
Inc., Santa Clara, California, USA) with ablation zone 6.0 x 5.7 mm for ellipse and 5.5 mm for sphere
OS; 303 pulses were administered. The fellow eye was similarly treated on 5/27/98 with correction of 4.71 -2.33 X 90; ablation zone of 6.0 mm x 4.9 mm; 435 pulses were administered. The total calculated
ablation depth was 70 μm in the right eye and 100 μm in the left eye.
The early postoperative course was uneventful. 6 weeks after the procedure, UCVA was 20/20 OU, and
BSCVA OD was 20/15 (plano -0.25 X 35). Slit-lamp biomicroscopy was normal OU.
At 5 years follow up UCVA was CF at 6 feet OD and 20/40 OS. BSCVA was 20/25 OD with refraction
of +0.50 -5.50 x 90 and 20/20 with refraction of -1.00 sphere OS. Corneal pachymetry OD was 481 μm
centrally and 374 μm inferiorly. With preoperative pachymetry of 500 μm OD, we thought the
postoperative values might have been related to a combination of corneal epithelial hyperplasia and new
collagen deposition. Pachymetry of the fellow eye was 450 μm centrally and 450 μm inferiorly.
Corneal topography (Zeiss Hymphrey Systems) showed marked inferior steepening OD and was normal
topography in the fellow eye. (Figure 2) The patient underwent Intacs (Addition Technology, Inc.)
insertion with IntraLase femtosecond laser (IntraLase Corp.) channels OD in 01/2005.
Most recent follow up in 04/06 revealed UCVA CF at 6 feet OD. BSCVA was 20/70 with - 3.50 - 2.25 x 105.
The fellow eye remained stable both topographically and clinically. (Figure 2)
Patient was referred for SynergEyes (SynergEyes Inc., Carlsbad, CA) contact lens fit. (Figure 3) SynergEyes is a
hybrid contact lens made of a rigid gas permeable (RGP) center fused to a soft, hydrophilic outer skirt. This
design is thought to provide vision correction through the central RGP portion of the lens combined with a
soft periphery to bear the weight and improve centration qualities. BCVA with SynergEyes contact lens in
our patient was 20/20-2 OD with plano over-refraction. Topography OD again showed inferior steepening.
(Figure 4)
Topography with the SynergEyes contact lens in place showed a marked improvement in the corneal
contour. (Figure 5)
Discussion:
Keratectasia is a known major complication of LASIK. To date, over 100 cases have been reported in
refractive surgery literature (1). Several preoperative risk factors have been proposed for keratectasia after
LASIK, such as high myopia, forme fruste keratoconus (FFK), and low residual stromal bed, but cases
with mild myopia, normal topography, and residual stromal bed >300 μm also may develop ectasia. (2,3)
Keratectasia is also one of the most difficult post-LASIK complications to manage; current options
include RGP contact lenses, intracorneal rings, phakic toric IOLs and lamellar or penetrating keratoplasty
(4,5,6).
Even though the upper limit of myopia suitable for treatment by LASIK has been arbitrarily set as -12.0,
keratectasia cases after LASIK was noted in cases treated for much lower degrees of myopia, from –4.0
to –7.0 D (7). Inferior corneal steepening was noted in some of these cases pre-operatively. In the
absence of refractive instability or biomicroscopic features of keratoconus these corneal changes have
been termed forme fruste keratoconus (FFK) (8). There are a few case reports indicating good long-term
refractive outcomes and corneal stability after PRK in such cases as compared to LASIK (9,10). One
study of a corneal forward shift after PRK using a scanning-slit corneal topography found that these
changes usually stabilize 6 months after surgery (11). A more recent case report described a patient with
thin central corneas (485 microns in the right eye and 500 microns in the left eye) and corneal topography
revealing asymmetric bow-tie astigmatism with inferior steepening in the right eye and a small area of
inferior steepening in the left eye, who underwent a PARK in the right eye and LASIK in the fellow eye
(12). Both eyes had similar myopic and astigmatic refractive error. 22 months postoperatively, patient
developed keratectasia in the post-LASIK eye; post-PARK fellow eye remained stable both clinically and
topographically. The authors have concluded that PARK/PRK may be a safer procedure, especially in the
eyes with pre-operative risk factors.
Discussion (continued):
Our patient had a clear preoperative FFK in the right eye and normal topography in the left eye. His other
risk factors included BSCVA of less than 20/20 and relatively thin corneas. He elected to proceed with
bilateral PRK and had developed progressive corneal changes consistent with clinical keratoconus in the
right eye. The left eye has remained stable over the period of 7 years in regards to visual acuity, corneal
topography and biomicroscopic findings. The question to ask here is would this patient have developed
progression of FFK in the right eye without PRK? Previous studies have clearly demonstrated
spontaneous progression of FFK into clinical keratoconus (13). Our patient has developed progressive
unilateral corneal changes after PRK. His refraction has been stable in that eye for several years preoperatively.
It is not unreasonable to suggest that post-PRK biomechanical corneal weakening had
accelerated progression of unilateral FFK to clinical keratoconus. A recent longitudinal study of
keratoconus patients concluded that around 50% of clinically normal fellow eyes will progress to
keratoconus in 16 years. (14) It is also not unreasonable to theorize that out patient may still develop
clinical keratoconus in the fellow eye in the future.
This case report illustrates that in FFK may progress to clinical keratoconus after PRK procedure. A few
recent publications have advocated choosing PRK over LASIK for patients with preoperative risk factors
for developing corneal ectasia. Moreover, a recent article by Bahar et. al. (15) suggested that a wavefront
supported PRK appears to be effective for treatment of myopia and astigmatism in patients with
suspected keratoconus and thin, irregular corneas. Authors suggest that patients in whom LASIK surgery
is contraindicated because of suspected FFK, especially when the I-S difference is greater than1.5 D, are
good candidates for wavefront-supported PRK treatment, as it saves ablated tissue and treats corneal
surface irregularities. A major drawback of the study remains short-term (less then 40 months) follow up
(less then 40 months).
Discussion (continued):
We conclude that the issue of PRK safety over LASIK for patients with FFK and thin, irregular corneas
needs to be studied further before any recommendations of its preference is universally accepted. In
addition, a careful preoperative discussion, clinical evaluation and informed consent are of a paramount
importance for patients with preoperative risk factors who desire refractive surgery, either LASIK or
PRK.
Figure 3
Figure 4
Figure 5
References:
1. Lifshitz T, MD; Levy J, MD; Klemperer I, MD; Levinger S, MD. Late Bilateral Keratectasia After
LASIK in a Low Myopic Patient.J Refract Surg. 2005;21:494-496
2. Randleman JB, Russell B, Ward MA, Thompson KP, Stulting RD. Risk factors and prognosis for
corneal ectasia after LASIK. Ophthalmology. 2003;110;267-275.
3. Binder PS. Ectasia after laser in situ keratomileusis. J Cataract Refract Surg. 2003;29:2419-2429.
4. Eggink FAGJ, Houdijn Beekhuis WH. Contact lens fitting in a patient with keratectasia after laser in
situ keratomileusis. J Cataract Refract Surg. 2001;27:1119-1123.
5. Geggel HS, Talley AR. Delayed onset keratectasia following laser in situ keratomileusis. J Cataract
Refract Surg. 1999;25:582-586
6. Siganos CS, Kymionis GD, Astyrakakis N, Pallikaris IG. Management of post-LASIK Corneal Ectasia
with INTACS. J Refract Surg. 2002;18:43-46
7. Amoils SP, Deist MB, Gous P, Amoils PM. Iatrogenic keratectasia after laser in situ keratomileusis for
less than -4.0 to -7.0 diopters of myopia. J Cataract Refract Surg. 2000; 26:967–977
8. Seiler T, Quurke AW. Iatrogenic keratectasia after LASIK in a case of forme fruste keratoconus.
J Cataract Refract Surg. 1998; 24:1007–1009
9. Sun R, Gimbel HV, Kaye GB. Photorefractive keratectomy in keratoconus suspects. J Cataract Refract
Surg. 1999; 25:1461–1466
10. Bilgihan K,O et al. Results of photorefractive keratectomy in keratoconus suspects at 4 years. J
Refract Surg. 2000; 16:438–443
11. Miyata K, MD; Kamiya k, MD; Takahashi T, MD; Tanabe T, MD; Tokunaga T, COT; Amano S, MD; Oshika
T, MD. Time Course of Changes in Corneal Forward Shift After Excimer Laser Photorefractive Keratectomy Arch
Ophthalmol. 2002;120:896-900
12. Rao S.K., DO, DNB, FRCSEd; Srinivasan B, MS; Sitalakshmi G, DO, FRCSEd; Padmanabhan P,
MS. Photorefractive keratectomy versus laser in situ keratomileusis to prevent keratectasia after corneal
ablation. J Cataract Refract Surg. 2004; 30:2623–2628
13. Maguire LJ, Lowry JC. Identifying progression of subclinical keratoconus by serial topography
analysis. Am J Ophthalmol. 1991;112: 41-5
14. Li X, Rabinowitz YS, Rasheed K, Yang H. Longitudinal study of normal eyes in unilateral
keratoconus patients. Ophthalmology 2004; 111: 440-6
15. Bahar I, Levinger S, Kremer I. Wavefront-supported Photorefractive Keratectomy With the Bausch &
Lomb Zyoptix in Patients With Myopic Astigmatism and Suspected Keratoconus. J Refract Surg.
2006;22:533-538