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DONATION DONATION

Corneal Transplantation Figure 1: Full-thickness corneal transplant in a child with Herpes Simplex temic corticosteroids and immunomodulatory therapy may be required

Keratitis at 4-year follow-up.
to resolve the rejection. In a large series of penetrating keratoplasties
(n=4499), Kaplan-Meier survival curves showed survivals of 97 per-
By Natalie A. Johnson, MS1, and Daniel A. Johnson, MD, MBA cent, 79 percent, 72 percent and 69 percent at one, three, five and seven
C orneal transplantation involves exchanging normal corneal stroma, Descemet membrane and endothelium, were then transplanted years, respectively. The predominant reasons for graft failure included
rejection (34 percent), infections (18 percent), glaucoma (9 percent),
into a 76-year-old with endothelial dysfunction following cataract sur-
tissue for that which is diseased or damaged. The 500–600-
primary failure (6 percent), trauma (4 percent) and other causes. Given
micron thick cornea is the most anterior extension of the
gery as a Descemet Stripping Endothelial Keratoplasty (DSEK).
that transplant rejection is a significant cause of graft loss, it is impor-
globe and is divided into five layers: epithelium, Bowman layer, stroma, Due to advancements in the techniques for corneal transplantation,
tant that patients monitor for symptoms of photophobia, pain, redness
Descemet membrane and endothelium. The cornea is responsible for the frequency of these procedures has drastically increased. In 2022
and decreased vision, and know to seek ophthalmologic care immedi-
nearly 75 percent of the eye’s ability to focus light clearly on the retina alone, approximately 72,000 transplants were performed worldwide,
ately for evaluation and management in the event of these changes.
and is composed predominantly of Type 4 collagen fibers uniformly with nearly 50,000 of them having taken place within the United States.
Future goals for corneal transplantation include the development of
arranged to maintain optical clarity. The cornea receives its oxygen sup- Within the United States for this year, the leading indication for ker-
bioengineered corneal tissue, which will prevent allograft rejection and
ply from the tear film, and its nutrients and macromolecules from the atoplasty was due to endothelial disease. Since 2012, for endothelial
provide a solution to a corneal donor shortage. In addition, the devel-
aqueous humor. Cells of the endothelial layer pump fluid from the diseases such as Fuchs corneal dystrophy, the number of endothelial
opment of an ex-vivo expanded endothelial cell culture that can be in-
cornea into the anterior chamber to maintain deturgescence. keratoplasties (Figure 2) has surpassed that of full-thickness corneal Figure 2: Endothelial keratoplasty in a patient with pseudophakic bullous jected into the eye and directed to the Descemet membrane would
keratopathy at 1-month follow up.
In states of disease in which infection or trauma create scars that alter transplants. According to the Eye Bank Association of America, in
revolutionize the management of endothelial disease.
the orderly arrangement of collagen fibers in the corneal stroma, the 2022, there were 15,835 full-thickness, 30,812 endothelial and 476 an-

image reaching the retina degrades. Fluid may also collect within the terior lamellar keratoplasties performed nationwide. References:
corneal stroma as a result of endothelial cell loss from age, surgery or The sheer number of types of keratoplasty procedures has led to the American Academy of Ophthalmology Basic Science and Clinical
trauma. This resulting edema can alter the orderly arrangement of fibers development of a proverbial “alphabet soup” of abbreviations to include Series, Section 2, Fundamentals and Principles of Ophthalmology and
and similarly degrade optical quality. ALK (Anterior Lamellar Keratoplasty), ALTK (Anterior Lamellar Section 8, Cornea and External Disease. 2023-2024. San Francisco,
When corneal clarity, either from edema or scarring, declines below Therapeutic Keratoplasty), DALK (Deep Anterior Lamellar Kerato- CA, EPub
a level required by the patient for adequate functioning, corneal trans- plasty), dDALK (Descemetic Deep Anterior Lamellar Keratoplasty), Crawford AZ, Patel DV, McGhee CNJ. A brief history of corneal
plantation may be considered. Although concepts of corneal surgery pdDALK (pre-Descemet Deep Anterior Lamellar Keratoplasty), transplantation: From ancient to modern. Oman J Ophthlamol 2013
can be dated to Galen (130-200 AD), it was not until 1837 when DMEK (Descemet Membrane Endothelial Keratoplasty), DSEK (De- Sep-Dec; 6 (suppl 1): S12-17
Samuel Bigger reported a successful gazelle-to-gazelle corneal trans- scemet Stripping Endothelial Keratoplasty), DSAEK (Descemet Strip- 2022 Eye Banking Statistical Report. Eye Bank Association of Amer-
plant. Subsequent xenografts to humans failed, as expected. In 1905, ping Automated Endothelial Keratoplasty), DSO/DWEK (Descemet ica. Copyright 2023 EBAA
the first successful human-to-human corneal transplant was performed Stripping Only/Descemet Without Endothelial Keratoplasty), EK Nikolic L, Javanovic V, Jamkov II. One cornea for two patients: case
by Edward Zirm. In this procedure, the enucleated eye of an 11-year- (Endothelial Keratoplasty), FLAK (Femtosecond Laser-Assisted Ker- report. Arq Bras Optalmol 2010;73(3):291-293
old who suffered a penetrating scleral wound was used as the donor for atoplasty), FLEK (Femtosecond Laser-Enabled Keratoplasty) and Figure 3: Full-thickness corneal transplant with endothelial deposits indicat- Williams KA, Muehlberg SM, Lewis RF, Coster DJ. How successful
ing allograft rejection.
a 45-year-old with bilateral alkali burns. Since then, numerous advances PKP/PK (Penetrating Keratoplasty). The selection of the appropriate is corneal transplantation? A report from the Australian Corneal Graft
have paved the way for modern corneal surgery, including the under- technique depends upon the depth of the corneal pathology. For full- Register. Eye 1995, 9:219-227
standing of sterile technique and the refinement of anesthesia. The de- thickness disease, such as a corneal scar from a contact lens-related in- American Academy of Ophthalmology Preferred Practice Pattern:
velopment of specialized instruments, surgical microscopes, inert suture fection, transplantation of all layers of the cornea is typically required. Corneal Edema and Opacification. American Academy of Ophthal-
material, corticosteroids, eye banks and donor storage medium that For diseases of the corneal endothelium, such as Fuchs endothelial dys- mology, 2018. San Francisco, CA. www.aao.org/ppp
can maintain endothelial function for approximately two weeks have trophy, the most common procedures include partial-thickness kerato-
further contributed to this field. plasties, such as DMEK or DSEK. Natalie Johnson is a graduate of the Texas A&M University
Full-thickness transplantation (Figure 1) was previously required in Partial-thickness, or lamellar surgery, has advantages over full-thick- College of Biomedical Sciences and is now a first-year medical stu-
the event of loss of corneal clarity, but evolving techniques have allowed ness procedures in terms of globe stability, less risk of suture-related dent at the Long School of Medicine in the combined MD/MPH
selective replacements for either superficial, deep or full-thickness erosion and infection, and lower incidence of allograft rejection (Figure pathway. She is considering a career in Ophthalmology.
pathology. In fact, in 2010, Ljubis Nikolic and colleagues reported the 3). In 2022, the most common indication for full-thickness transplan-
use of one donor cornea for two different patients. The superficial half tation was corneal ectasia. However, the frequency of these grafts has Daniel A. Johnson, MD, MBA, is the Herbert F. Mueller
of the donor cornea was transplanted into a 60-year-old with a necrotic decreased, mostly attributed to the development of corneal cross-link- Chair, Department of Ophthalmology at UT Health San Anto-
corneal melt to Descemet membrane from herpes simplex keratitis as ing, specialty contact lenses and scleral lenses. transplants, prior rejection and glaucoma. In the event of transplant re- nio. He specializes in the management of uveitis/ocular inflam-
a Deep Anterior Lamellar Keratoplasty (DALK). The remaining pos- The risk of transplant rejection is low for eyes without significant co- jection, topical steroids alone are often used as treatment due to their matory disease and cornea and external diseases. Dr. Johnson is a member
terior layers of the donor cornea, including the posterior corneal morbidities, such as corneal neovascularization, uveitis, prior corneal excellent penetration through the corneal graft. For complex cases, sys- of the Bexar County Medical Society.

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