Refractive and Corneal Aberrometric Changes After Crescentic Lamellar Wedge Resection in Pellucid Marginal Degeneration

ARTICLE
Refractive and Corneal Aberrometric Changes After Crescentic
Lamellar Wedge Resection in Pellucid Marginal Degeneration
Selim Genç,
M.D.,
Hanefi Çakır,
M.D.,
Objective: To evaluate the effectiveness of crescentic corneal lamellar
wedge resection for the treatment of pellucid marginal degeneration (PMD)
in improving refractive, visual, and corneal aberrometry.
Methods: The study included 10 eyes of 10 patients who had undergone
corneal lamellar wedge resection for PMD. Pellucid marginal degeneration
was diagnosed based on the clinical signs and corneal topography. The
corneal aberrometry was evaluated with Sirius corneal topography.
Results: The mean follow-up period was 14.1 months (range, 9–24
months). Uncorrected visual acuity was improved in nine eyes and
remained unchanged in 1 case, whereas best-corrected visual acuity was
improved in all eyes postoperatively. By vector analysis, the overall mean
astigmatic drift at the last visit was calculated to be 13.066.3 diopters (D).
At last visit, significant reductions were found for all aberrometric measurements. However, the differences were not significant for the measurements
of trefoil (P¼0.189).
Conclusions: Corneal lamellar wedge resection is a favorable surgical
option for management of PMD, allowing for improved visual acuity,
keratometric cylinder, and corneal aberrations.
Key Words: Crescentic corneal lamellar wedge resection—Pellucid
marginal degeneration—Corneal aberrometry.
(Eye & Contact Lens 2017;0: 1–5)
P
ellucid marginal degeneration (PMD) is an ectatic corneal
disease, which is generally associated with a crescent shape
of inferior peripheral corneal thinning.1 The ectatic corneal morphology causes against-the-rule astigmatism and visual loss.2 The
management of PMD includes a variety of treatment modalities—
spectacles, rigid gas-permeable contact lenses,3 and surgical
techniques such as intracorneal ring segments,4 full-thickness crescentic wedge resection,5 lamellar crescentic wedge resection,6 deep
anterior lamellar keratoplasty,7 and penetrating keratoplasty (PK).8
Intracorneal ring segments are inadequate to decrease high levels
of astigmatism and may not eliminate corneal ectasia, which is
From the Department of Ophthalmology (S.G.), Lütfi Kırdar Kartal Eye
_
Training and Research Hospital, Istanbul,
Turkey; Eye Clinic (H.C., E.G.),
_
Türkiye Hospital, Istanbul,
Turkey; and Department of Ophthalmology (Ü.
_
Ç.), Ümraniye Training and Research Hospital, Istanbul,
Turkey.
The authors have no funding or conflicts of interest to disclose.
Supplemental digital content is available for this article. Direct URL
citations appear in the printed text and are provided in the HTML and PDF
versions of this article on the journal’s Web site (www.
eyeandcontactlensjournal.com).
Address correspondence to Emre Güler, M.D., Türkiye Hospital, Merkez
_
Mah. Darülacaze Cad. No: 14/1, 34381 Şişli/Istanbul,
Turkey; e-mail:
[email protected].
Accepted May 27, 2017.
DOI: 10.1097/ICL.0000000000000409
Eye & Contact Lens Volume 0, Number 0, Month 2017
Emre Güler,
M.D.,
and Ümit Çallı,
M.D.
probably associated with disease progression. Full-thickness wedge
resection and PK include open eye surgery risks and may be
associated with glaucoma due to the marginal location and extend
of the graft.9 The advantages of crescentic lamellar wedge resection
include the removal of pathological tissue which improves the
corneal morphology and irregular astigmatism without the use of
allogeneic tissue and risks of open eye surgery.10
Wavefront technology has been used for the measurement of
ocular or corneal higher-order aberrations (HOAs) which are
uniquely described by a weighted sum of the Zernike terms.11 In
PMD, the increased corneal HOAs, especially the trefoil and spherical aberrations, are the leading causes of optical errors along with
the induced against-the-rule astigmatism and visual acuity
decline.12 In this study, we aimed to evaluate the refractive, visual,
and corneal aberrometric changes after lamellar crescentic wedge
resection in eyes with PMD. To the best of our literature knowledge, this is the first study to analyze the corneal aberrometric
changes after lamellar crescentic wedge resection in PMD.
PATIENTS AND METHODS
Ten eyes of 10 patients with PMD who underwent lamellar
crescentic wedge resection at our institutions between November
2013 and January 2015 were evaluated retrospectively. Included
patients had steep keratometry .57 D, best-corrected visual acuities (BCVAs) between 20/40 and 20/400, and intolerance to spectacle or contact lens use. Excluded patients had a history of ocular
surgery, ocular trauma, and any ocular disease other than PMD.
The study patients had provided their informed consent. The study
was conducted in accordance with the ethical standards stated in
the Declaration of Helsinki and was approved by the Local Ethics
Committee.
Pellucid marginal degeneration was diagnosed based on the
findings of slit-lamp biomicroscopy (corneal ectasia localized
inferiorly along with corneal thinning), corneal topography
(butterfly pattern, high steep contour, and increased keratometric
powers radiating toward the inferior peripheral cornea), and
refractive changes (convincing against-the-rule astigmatism along
with a decline of BCVA).
All eyes had a comprehensive preoperative and postoperative
ophthalmic examination that included uncorrected visual acuity
(UCVA), BCVA, manifest refraction by autorefraction
(TOPCON), intraocular pressure (IOP), slit-lamp biomicroscopy,
and corneal topography with Orbscan (Oculus Optikgeräte GmbH,
Wetzlar, Germany) and Sirius (Costruzione Strumenti Oftalmici,
Florence, Italy) devices. Visual acuity was measured with Snellen
charts and converted to logarithm of the minimal angle of
1
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S. Genç et al.
keratometric powers and corneal wavefront values. The SE was the
sum of the spherical and half of the cylindrical values. The vector
analysis demonstrated the degree of the astigmatic correction
which includes the final amount of astigmatism and change in
astigmatism achieved by surgery.13,14
resolution values. Corneal wavefront analysis was performed in
eight eyes using Sirius device which uses a monochromatic rotating Scheimpflug camera and a Placido disk. The Sirius performs
the aberrometric measurements by the ray-tracing technique. The
corneal wavefront measurements including the root mean square
(RMS) values of HOAs, coma, trefoil, and spherical aberrations
were obtained over a 6-mm optical zone and decomposed into
Zernike polynomials to the sixth order.
Data Analysis
SPSS 21.0 for Windows (SPSS Inc., Chicago, IL) was used for
the statistical analysis. The distribution of the data was normal and
met by the Kolmogorov–Smirnov test (P.0.05). The measured
variables were evaluated by Wilcoxon signed-rank test. P value
less than 0.05 was accepted to be statistically significant.
Surgical Technique
The surgical procedures were applied using peribulbar anesthesia. Initially, the borders of the area to be excised were signed using
a gentian violet under the operating microscope. We aimed to
prepare a corneal tissue with 10-mm length and 1.5-mm width
centrally. Using a 45° metal blade, a crescentic wedge of ectatic
corneal tissue (with a deepening of at least 80% of corneal
thickness) was excised in each case. After wedge resection, anterior
chamber paracentesis was performed using a 1.2-mm single-plane
side-port incision to provide intraocular hypotony, and then the
wound resulting from wedge resection was sutured with 10-0 nylon
suture. Initially, a central suture was applied and was continued one
by one in each side (see Video, Supplemental Digital Content 1,
http://links.lww.com/ICL/A62). Postoperative regimen included
moxifloxacin and dexamethasone eyedrops which were applied
5 times a day for a 4-week period.
Main outcome measures were UCVA, BCVA, spherical equivalent (SE) refraction, and corneal topography findings including
TABLE 1.
RESULTS
The study included six men and four women. The mean age of
patients was 54.467.3 years (range 41–73 years). The mean
follow-up period was 14.164.9 months (range, 9–24 months).
All patients had inferior thinning. Table 1 demonstrates the
preoperative and postoperative data of the patients.
The mean UCVA and BCVA were significantly improved
postoperatively (P were ,0.001 and 0.001, respectively). Uncorrected visual acuity was improved in nine eyes and remained
unchanged in 1 case (case 10, Table 1), whereas BCVA was
improved in all eyes postoperatively. All patients had improved
BCVA with spectacles.
Preoperative and Postoperative Refractive Outcomes
UCVA, logMAR
BCVA, logMAR
SE, D
Patient
Preoperative
Postoperative
Preoperative
Postoperative
Preoperative
Postoperative
1
2
3
4
5
6
7
8
9
10
Mean
SD
P
2.0
1.3
1.0
1.3
1.3
1.5
1.5
2.0
2.0
2.0
1.59
0.38
1.0
0.5
0.4
0.7
0.7
0.5
0.8
1.0
1.8
2.0
0.95
0.54
,0.001
1.3
0.4
0.3
0.7
0.8
0.7
0.7
1.0
2.0
0.4
0.83
0.50
0.2
0.1
0.1
0.2
0.1
0.2
0.3
0.4
0.5
0.2
0.23
0.13
0.001
27.75
25.75
210.0
27.87
211.50
28.62
21.75
27.12
NA
NA
26.03
4.09
24.12
20.25
23.62
21.87
25.12
0.75
1.62
23.75
21.50
22.25
22.01
2.21
0.006
SimK, D
Keratometric Cyl, D
Patient
Preoperative
Postoperative
Preoperative
Postoperative
Vector Change in Keratometric Cyl, D
Follow-up, mo
1
2
3
4
5
6
7
8
9
10
Mean
SD
P
53.20
51.97
55.86
56.66
50.74
51.78
48.44
51.91
55.40
43.50
51.94
3.88
50.40
41.04
44.29
52.03
46.24
44.87
42.64
43.38
45.30
46.20
45.63
3.36
0.001
2.2·156
9.9·11
9.9·26
10.4·11
9.4·166
8.9·176
3.3·152
7.7·133
6.2·167
13.7·171
8.1
3.4
1.2·70
7.1·90
7.7·93
9.9·85
6.8·97
4.3·64
4.8·95
7.3·120
15.3·90
5.2·120
7.0
3.7
0.169
3.5
16.7
16.3
19.6
15.2
12.3
6.9
3.4
21.0
15.6
13.0
6.3
18
24
12
9
15
18
9
12
18
10
14.15
4.94
P,0.05 indicates statistically significant intragroup difference.
BCVA, best-corrected visual acuity; Kf, keratometry flat; Kf, keratometry steep; logMAR, logarithm of the minimal angle of resolution; NA,
Not Applicable; SE, spherical equivalent; SimK, simulated keratometry; UCVA, uncorrected visual acuity.
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Because of advanced ectasia, we managed to assess SE values
for eight of all eyes. For these eyes, the mean SE was 26.0364.09
D preoperatively and 22.0162.21 D postoperatively (P¼0.006).
The mean preoperative simulated keratometry was
51.9463.88 D, and at last visit, it was significantly reduced to
45.6363.36 D (P¼0.001). The mean preoperative keratometric
cylinder was 8.163.4 D, and at the last visit, it was improved to
a postoperative mean of 7.063.7 D (P¼0.169). By vector analyzes, the overall mean astigmatic drift was calculated to be
13.066.3 D at the last visit (Fig. 1).
A detailed data of the corneal aberrometric values is shown in
Table 2. At the last visit, significant reductions were found for all
aberrometric measurements. However, the differences were not
significant for the measurements of trefoil (P¼0.189).
Intraoperative corneal microperforation occurred in one patient,
and it was sutured simultaneously with the absence of postoperative sequelae (Fig. 2). Descemet membrane striae occurred in
all cases; however, none of these were present in the central cornea
and caused irregular astigmatism. In addition, during follow-up
period, no cases had increased IOP or recurrence of PMD. The
selective suture removal time was at least 6 months, and three eyes
had still sutures remaining at last review.
DISCUSSION
Many authors have reported resection of a wedge shaped ectatic
corneal tissue in PMD.5,10,15,16 This surgical approach provides
many advantages superior to penetrating methods which include
the conservation of normal central cornea, mechanically stronger
wound, faster visual recovery, and the absence of steroid-related
adverse effects or immunologic rejection.5,17 The primary purpose
of this surgical procedure is to remove the ectatic corneal tissue,
provide a normal corneal structure, and prevent the progression of
the disease. Full-thickness crescentic wedge resection includes the
risks open eye surgery and glaucoma. To avoid these complications, deep lamellar dissection as close as possible to the Descemet
Aberrometric Changes in PMD
membrane is crucial and to obtain a smooth surface which prevents
striae, interface opacification, and irregular astigmatism.
Limited number of studies evaluated the efficacy of the lamellar
crescentic wedge resection in the management of PMD. Busin
et al.16 performed lamellar wedge resection combined with penetrating relaxing incisions in 10 eyes with PMD. The BCVA
improved in eight patients, and the mean keratometric astigmatism
was reduced from 15.1 D preoperatively to 4.6 D at 6 months
postoperatively. Maccheron et al.10 showed improvement in
BCVA along with a 9.1 D reduction in keratometric cylinder at
postoperative 10 months in seven eyes with PMD. Similar to
previous studies, corneal shape and astigmatism were favorably
corrected along with a significant gain in UCVA and BCVA using
lamellar corneal wedge resection technique. In general, a mild
corneal flattening was induced by the surgery, which resulted in
a decrease in corneal keratometry and hyperopic alteration in SE
postoperatively.
MacLean et al.5 reported the outcomes of full-thickness crescentic wedge resection in 10 eyes with PMD. Postoperatively, an
improvement in BCVA was achieved in all eyes. Mean keratometric astigmatism decreased from 13.8 D to 1.4 D. However, astigmatic drift was noted at long-term follow-up with a mean of 2.1 D
(range 0.5–5.5 D). In addition, three patients showed inferior pannus associated with sutures, and 1 case had corneal hydrops in the
corneal wound postoperatively. In our cases, no patient had astigmatic drift, corneal vascularization, and suture-related
complications.
A few studies have discussed HOAs in patients with PMD.
Kamiya et al.18 reported an increased corneal coma-like aberration
while the spherical-like aberration did not change in the 11 year
follow-up of a case with PMD. The features of ocular HOAs in
eyes with PMD using Zernike terms were evaluated only in one
study.12 They found significantly increased corneal HOAs compared with healthy eyes with the mean total HOA RMS of
0.5660.28 mm, coma of 0.2760.19 mm, and spherical aberration
of 0.08660.10 mm. In the current study, the corneal aberrations
FIG. 1. (A) The preoperative topography of case 2. (B) The same case at 24
months postoperatively showing a 16 D
improvement in astigmatism.
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S. Genç et al.
TABLE 2.
Preoperative and Postoperative Mean Square (RMS) Results of Corneal Wavefront Aberrations
HOA, mm (Mean 6 SD)
Coma, mm (Mean 6 SD)
Trefoil, mm (Mean 6 SD)
Spherical, mm (Mean 6 SD)
Patient
Preoperative
Postoperative
Preoperative
Postoperative
Preoperative
Postoperative
Preoperative
Postoperative
1
2
3
4
5
6
7
8
Mean
SD
P
6.26
4.32
6.15
4.82
5.50
8.39
2.90
3.72
5.25
1.71
4.91
3.83
5.45
4.22
2.28
3.22
1.15
2.45
3.43
1.44
0.015
5.35
8.32
4.50
2.19
4.83
6.04
2.68
3.19
4.63
2.00
4.05
3.42
3.45
1.17
3.16
2.88
1.18
1.86
2.64
1.10
0.004
2.29
6.23
0.89
3.26
1.65
8.54
0.76
1.61
3.15
2.79
2.27
0.84
1.17
3.19
1.88
2.28
1.12
1.18
1.74
1.80
0.189
21.71
21.75
22.97
22.04
21.69
21.54
20.44
20.33
21.55
0.85
20.40
0.28
0.02
20.56
20.28
20.22
20.12
20.08
20.17
0.25
0.003
P,0.05 indicates statistically significant intragroup difference.
HOA, higher-order aberration; RMS, root mean square.
were considerably higher in our cases than the previously reported
as shown in Table 2.
It has been shown that the progression in topographic changes
induce high degrees of against-the-rule astigmatism and coma-like
aberrations.18 In routine clinical practice, corneal aberrations
should be considered when evaluating the optical quality. In eyes
with PMD, the increased corneal aberrations are one of the leading
causes of optical deficits. To the best of our literature knowledge,
the current study is the first to assess the corneal aberrometry after
lamellar crescentic wedge resection in PMD. In our cases, higherorder, coma-like, and spherical-like aberrations were significantly
decreased postoperatively. Furthermore, trefoil also showed
a decrease; however, it was not statistically significant.
The early goal of this surgical method is to provide an
overcorrection in corneal astigmatism which regresses by corneal
remodeling, wound healing, and suture loosening in the postoperative period. Further management of astigmatism can be
achieved by selective suture removal or controlling of corneal
wound healing by topical steroid usage. Therefore, the visual
rehabilitation after lamellar wedge resection involves a long period.
In our cases, the time for selective suture removal was at least
6 months postoperatively, and spectacles were used for visual
rehabilitation at the earliest opportunity.
In this study, we have excised a longer wedge shaped corneal
tissue (10 mm) to achieve homogenous corneal flattening and
normalize the inferior–superior meridian of the cornea. In addition,
anterior chamber paracentesis should be performed to provide
intraocular hypotony. This allows the in folding of the Descemet
membrane and edge-to-edge suturing of the stromal wounds which
enhances the effectiveness of the surgery. Wedge resection may
also be useful to provide an appropriate corneal bed for further
corneal transplantation.
Wedge resection, especially when involves a large amount of
corneal tissue followed by simple closure of wound, may cause
Descemet membrane striae formation and irregular astigmatism. To
prevent this complication, lamellar dissection and/or relaxing
incisions may be considered. In our study, a large amount of
corneal tissue has been excised (1.5-mm width centrally); however,
because of its crescent shape, resection acts as a relaxing incision in
the peripheral cornea. In all cases, Descemet membrane striae
occurred; however; none of these were present in the central cornea
and caused irregular astigmatism.
In conclusion, lamellar crescentic wedge resection is a favorable
surgical option to improve the visual acuity and astigmatism in
advanced PMD which directly targets the corneal ectasia without the
risks of allograft PK and lamellar keratoplasty. Furthermore, corneal
HOAs are significantly improved after this surgery. Future studies of
the outcomes with lamellar crescentic wedge resection in corneas
with PMD in the long term are required to confirm our findings.
ACKNOWLEDGMENTS
The authors thank Prof. Sait E
g rilmez for statistical analysis.
REFERENCES
FIG. 2. Slit-lamp photography shows the postoperative appearance
of a successful excision of a thinned area of cornea at postoperative 3
months.
4
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