Download Bilateral Aphakic Epikeratophakia-Induced Irregular Astigmatism

Bilateral Aphakic Epikeratophakia-Induced Irregular Astigmatism
Corrected with a Scleral Lens
Abigail G. Graeff, OD, Chantelle Mundy, OD, FAAO
Havener Eye Institute, The Ohio State University Wexner Medical Center Department of Ophthalmology and Visual Science
Introduction
Epikeratophakia onlay procedures were first introduced by Werblin in 1979 and
further developed by Kaufman and McDonald in 1980.1 This procedure involves
donor corneal tissue lathed into a lamellar disk and surgically transplanted onto
the anterior surface of the host cornea and stabilized via a small incisional “pocket”
in the host tissue periphery. Indications for this surgery included pediatric or adult
aphakia, hyperopia, myopia, and keratoconus. There were many advantages to
this procedure, including potential reversibility, minimal invasion, and preservation
of posterior layers of the host cornea.2 This procedure was particularly useful in
the pediatric aphakic population as it is indicated for aphakic patients with contact
lens intolerance, unilateral cataracts, and trauma induced cataracts with anterior
segment damage contraindicating an intraocular (IOL) lens implantation.2
Epikeratophakia demonstrated a favorable success rate and impressive stability
over long-term follow-up care. However, complications included myopic shifts and
graft-host interface edema and scarring.
Methods
Conclusion
Discussion
A diagnostic contact lens fitting was conducted in both eyes. Prognosis with
contact lenses was guarded the patient had a history of contact lens intolerance
due to discomfort. Because of this, scleral lenses were used for the diagnostic
fitting (Europa scleral, Visionary Optics). Corneal topography and Endothelial
Cell Counts were taken in both eyes (Pentacam, Oculus and CellChek Specular
Microscope, Konan Medical). Pachymetry was 976 microns in the right eye and
978 in the left eye.
Available literature concerning the success of scleral lens wear and
epikeratophakic corneal onlay procedures is limited. However, quantifying endothelial
cell counts can signify corneal pump integrity and therefore potential risk for corneal
edema. Low endothelial cell counts, usually counts less than 600-700 mm2, could result
in corneal edema as the increased corneal thickness increases stress on endothelial
cells rendering them incapable of maintaining corneal deterguescence. In a study of
average endothelial cell counts pre- and 16 months post-epikeratophakia surgery, the
average endothelial cell count pre surgery was 1450 per mm2 (+/- 218) and 1438 per
mm2 (+/- 218) 16 months post-surgery. Both endothelial cell counts were low, but did not
vary significantly after surgery, thus concluding that epikeratophakia is well tolerated by
the cornea and can be performed safely without substantial trauma to the host
endothelium.3 Because of this, scleral lenses are not contraindicated in epikeratophakic
patients.
Figure 4 (Left): The
anatomy of a postepikeratophakic eye 4
Case Presentation
A 49 year old white female, referred by her glaucoma specialist for a cornea
and contact lens evaluation, presented to our OSU clinic with a chief complaint of
blurred vision with her current glasses. She was born with congenital cataracts
and underwent bilateral cataract surgery as a child and as a result, was aphakic.
She then had an epikeratophakia onlay procedure at age 20 to treat her pediatric
aphakia. She was also diagnosed at age 10 with Type 1 Diabetes Mellitus. She is
currently using an insulin pump, notes stable blood sugar readings, and average
HbA1c readings of 6.8mg/dl. She is being treated for Ocular Hypertension of both
eyes with Cosopt BID OU. She is also taking Fluorometholone 0.1% BID OU.
Upon slit lamp examination, external examination was normal for both
eyes. There was a slight anisocoria with the right pupil displaced nasally. During
the corneal examination, epikeratoplasty lenticules were noted in both eyes. No
corneal edema was noted and the interface between the donor lenticule and the
host corneal tissue was clear with no scarring or deposits noted. No NVI noted in
both eyes. Both eyes were aphakic. Goldmann applanation IOP was 23 mmHg in
the right eye and 25 mmHg in the left eye. Upon DFE, C/D ratios were 0.2 in both
eyes. No NVD or NVE or CSDME was noted in either eye.
Figure 7 (Above): This is the right eye with the 16.0 mm final scleral lens in place
demonstrating uniform vault. Notice a slight nasally displaced pupil.
Figure 8 (Below): This is the left eye with the 16.0 mm final scleral lens in place
demonstrating uniform vault and no edge blanching.
Current Spectacle Rx:
Sphere
Cylinder
Axis
ADD
Distance VA PH VA
OD
+6.50
-3.50
096
+2.50
20/300
20/100
OS
+5.75
-1.75
141
+2.50
20/150
20/70
There are several complications associated with epikeratophakia procedures.
Complications can be graft-centric, including failure of graft tissue to reepithelialize, graft
haze, infection, deposits and vascularization of the graft tissue.5 However, complications
can also be associated with refractive changes or visual compromise. These
complications include induced irregular astigmatism, reduced contrast sensitivity, and
progressive myopic shifts (Kang). Because of these complications, treating pediatric
aphakes with epikeratophakic onlay procedures has been replaced by refractive surgery
and IOL implantation.
Scleral Lens fitting:
OD
OS
Brand
Visionary Optics,
Europa Scleral
BC
7.181
Diameter
16.0
Power
+7.50
PC
Standard
VA
20/25
Visionary Optics,
Europa Scleral
6.888
16.0
+7.25
Standard
20/25
Upon follow-up visit, she notes good comfort and vision and is able to wear
lenses for 12 hours per day. Upon over-refraction, a small amount of residual
astigmatism remained and prescribed along with a bifocal as a pair of glasses
to wear over the contacts. After settling time, there was slight corneal touch on
the right eye, therefore it was steepened by 2.00 D.
Over-Refraction:
Sphere
Cylinder
Axis
ADD
Distance VA
OD
+0.50
-0.75
088
+2.50
20/25-2
OS
+1.25
-0.50
085
+2.50
20/25+2
Final Scleral Lens Prescription:
OD
Figure 1 (Top): Scheimpflug image of right eye using the Pentacam corneal topographer. The interface between
the host cornea and epikeratophakic lenticule is visible. Also visible is a deep anterior chamber and aphakia.
Figure 2 (Bottom): Sheimpflug image of left eye using the Pentacam corneal topographer.
Figure 3: (Right): Slit lamp optic section of diagnostic scleral lens .
In patients with pediatric aphakia treated with epikeratophakia, long-term
success of the procedure has been documented for upwards of 20 to 30 years
post-surgery. In patients with refractive error shifts or induced irregular
astigmatism from epikeratophakic lenticules, rigid gas permeable lenses have
proven a successful treatment option in both comfort and visual acuity
improvements. As little is known concerning scleral lens wear and
epikeratophakia, more research is needed in order to fully understand
prognostic success with lens wear.
OS
Brand
BC
OZD
Visionary
Optics,
Europa
Scleral
Visionary
Optics,
Europa
Scleral
6.89
8.5mm 16.0 mm
Diameter Power Peripheral Curves CT
+6.50
6.89
8.5mm 16.0 mm
+7.25
PC1:
PC2:
PC3:
PC4:
PC1:
PC2:
PC3:
PC4:
6.780/2.10
9.00/0.75
13.00/0.50
14.50/0.40
6.806/2.10
9.250/0.75
13.250/0.50
14.50/0.40
Material
Vault
0.64
Boston
XO
300
microns
0.64
Boston
XO
300
microns
Figure 6 (Left):
Axial/Sagittal Curvature
(Front Surface) map of
Right eye using the
Pentacam Corneal
Topographer. This map
is consistent for
irregular astigmatism.
Figure 7 (Right):
Axial/Sagittal Curvature
(Front Surface) map of
Left eye using the
Pentacam Corneal
Topographer. This map
is consistent for
irregular astigmatism.
As irregular astigmatism is poorly treated with spectacle lenses, rigid gas
permeable contact lenses are an effective treatment in improving both visual acuity and
perceived visual quality. Scleral lenses, particularly, are successful in patients with
irregular astigmatism as they have improved comfort over smaller diameter rigid gas
permeable contact lenses. Scleral lenses must be carefully monitored when first
dispensed as corneal edema may result in situations such as contact lens overwear,
corneal hypoxic events, or a tight fitting lens. In patients with epikeratophakia, increased
corneal thickness combined with below average endothelial cell counts predisposes
them to corneal edema.
References
1. Rostron, Chad K. Introduction to epikeratophakia. Laser and conventional
refractive surgery. Chapter 8, 1996. Pages 157-209.
2. Kang, Julia, Florence Cabot, and Sonia H. Yoo. "Long-term follow-up of
epikeratophakia." Journal of Cataract & Refractive Surgery. Volume 41.3
(2015): 670-673.
3. Guss, R. B., et al. "Endothelial cell counts after epikeratophakia
surgery."Annals of ophthalmology. Volume15.5 (1983): 408-409.
4. Morgan, Keith S. “Optical Rehabilitation of Aphakia with Epikeratophakia”.
Duane’s Ophthalmology (2006). Chapter 103.
http://www.oculist.net/downaton502/prof/ebook/duanes/pages/v6/v6c103.html
5. Greenbaum, Aaron, Igor Kaiserman, and Isaac Avni. "Long-term reversibility
of epikeratophakia." Cornea. Volume 26.10 (2007): 1210-1212.