Secondary PDEK can follow therapeutic penetrating keratoplasty for corneal ulcer
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A corneal ulcer refractory to medical management often proceeds to therapeutic penetrating keratoplasty in the late stages.
Therapeutic penetrating keratoplasty (TPK) in such cases usually is performed to remove the infective load, and these eyes will require optical keratoplasty subsequently. Even though the infective source is removed from the eye after TPK, the visual acuity remains subnormal in such eyes due to poor quality of the cornea and nonavailability of high-grade donor cornea during the TPK period. Nevertheless, doing an endothelial keratoplasty such as pre-Descemet’s endothelial keratoplasty (PDEK) will help provide good quality of vision in such eyes for the long term. In this column, we discuss our experience of secondary PDEK on post-TPK eyes with prior infective corneal ulcer.
Source: Dhivya Ashok Kumar, MD, FRCS, FICO, FAICO, Amar Agarwal, MS, FRCS, FRCOphth, Soosan Jacob, MS, FRCS, DNB, and Preethi Naveen, MS
Corneal ulcer refractory to treatment
Corneal ulcers are common in tropical regions. Patients who are elderly or immunosuppressed or have a comorbidity such as diabetes can have prolonged treatment course and failure to medical management. Apart from contact lens users, trauma with vegetative matter can also be an etiology for long-term therapy in corneal ulcers. In a review of a large series in India, bacterial corneal ulcers were noted to be common, followed by fungal and mixed infections. A prior injury to the cornea was noted in 65.4% of cases, and corneal culture was positive in 68.4% of cases. When no significant improvement is noted with more than 6 weeks of topical/systemic treatment or progression is noted with maximum medical therapy, the treating physician opts for TPK.
Role of TPK in corneal ulcer
In TPK, the full-thickness cornea with the infective foci is removed and replaced by a donor cornea (Figure 1). The appropriate size corneal trephine depends on the diameter of corneal involvement, and the infected cornea is excised in toto and replaced with the donor cornea of measured size. Full-thickness interrupted sutures are placed and followed up with topical medications after TPK. As these procedures are usually performed on an emergency basis, the surgeons do not wait for a good grade of donor cornea. Hence, they use low-grade corneas for initial emergency tectonic support. Many times TPK offers visual improvement, but quality of vision may not be as efficient as in optical keratoplasty. At times, the transplanted corneal graft can survive with effective endothelial function if the endothelial count was high during the procedure with little loss after surgery. However, this may not be possible in the majority of cases as endothelial dysfunction can set in long term. In the popular Singapore Corneal Transplant Study, researchers concluded that tectonic and therapeutic keratoplasty procedures for corneal infections and perforations constitute a significant proportion of corneal transplantation performed in Asia and carry a graver prognosis in terms of graft survival.
Preliminary workup in secondary PDEK
Endothelial keratoplasty can be performed as a secondary procedure on a preexisting TPK graft. No improvement of vision, poor optical quality of the graft and bullous keratopathy are common indications for PDEK after TPK. The preoperative workup includes routine visual assessment, IOP, anterior segment OCT, specular microscopy, fundus examination, pachymetry, digital photography, conjunctival swab for microbial growth and ultrasound B-scan. Informed consent is needed for all patients, and the surgery is usually performed under peribulbar anesthesia. The preferred time duration for a good outcome is a minimum of 6 months after the initial TPK. Anterior chamber inflammation should be controlled, and there should not be any recurrence of infection at the time of preoperative PDEK.
PDEK after TPK
In the second stage, secondary PDEK is performed in the operating room with sterile precautions. A type 1 bubble (PDEK graft) is harvested from a good optical grade donor corneal button by the pneumatic method and kept in storage medium on the table. On the recipient bed, a 2.8-mm limbal or corneoscleral incision is made with a keratome. A trocar anterior chamber maintainer is fixed for a good, stable anterior chamber. We can also combine PDEK with phacoemulsification in eyes with coexisting cataract. In eyes with an irregular or abnormally dilated pupil (such as Urrets-Zavalia syndrome), pupilloplasty by the single-pass four-throw method is performed before PDEK intraoperatively (Figure 2). The pupilloplasty will thus act as a good iris-pupil diaphragm, preventing the air bubble from slipping inside. After completing additional procedures if needed, the surgeon can proceed to PDEK.
A descemetorhexis is performed with a reverse Sinskey hook, and the recipient endothelium (of the TPK graft) is manually stripped (Figure 3). The pre-harvested PDEK graft is then loaded onto the cartridge of a foldable IOL injector, and the spring of the injector is removed to prevent any damage to the graft. The graft is injected into the anterior chamber through the incision. The graft is slowly unfolded using air and fluidics, avoiding any direct contact with the graft to prevent any inadvertent endothelial cell loss due to manipulation (Figure. 3). Once the graft is unfolded, air is injected beneath the donor lenticule to facilitate its adhesion with the host cornea. The main port and side port are hydrated and closed with 10-0 monofilament nylon sutures. Precautions are to be taken not to disturb the original graft-host junction of the TPK graft, and the PDEK graft size should be sized accordingly, not too large to overlap the junction.
Our results with secondary PDEK
In a short series, we noted improvement in decimal equivalent mean distance visual acuity from 0.02 ± 0.01 preoperatively to 0.54 ± 0.17 postoperatively. Overall corneal clarity of grade 4 was noted in nine eyes, grade 3 in two eyes and grade 2 in one eye in the series. Mild subepithelial haze was noted in two eyes, and the percentage specular loss was 28.2% ± 10.6%. No correlation was observed between the postoperative graft clarity and preoperative endothelial density. Eyes with combined procedures such as phacoemulsification with IOL and pupilloplasty also showed good functional and anatomical outcomes (Figure 4).
Summary
Even though anatomical success is noted after TPK, functional outcome is limited due to nonavailability of quality grafts at the time of TPK and poor endothelial function postoperatively. Therefore, secondary endothelial keratoplasty such as PDEK is valuable in cases with good functional outcome. Good timing of the second surgery, preoperative good inflammatory control and a good quality donor graft can provide better outcomes in such cases in the long term.
- References:
- Agarwal A, et al. Br J Ophthalmol. 2014;doi:10.1136/bjophthalmol-2013-304639.
- Narang P, et al. Cornea. 2023;doi:10.1097/ICO.0000000000003383.
- Panda A, et al. Ophthalmic Surg. 1995;26(4):325-329.
- Sharma N, et al. Curr Opin Ophthalmol. 2010;doi:10.1097/ICU.0b013e32833a8e23.
- Srinivasan M, et al. Br J Ophthalmol. 1997;doi:10.1136/bjo.81.11.965.
- Tan DT, et al. Ophthalmology. 2008;doi:10.1016/j.ophtha.2007.08.049.
- For more information:
- Amar Agarwal, MS, FRCS, FRCOphth, director of Dr. Agarwal’s Eye Hospital and Eye Research Centre, is the author of several books, including Phaco Nightmares: Conquering Cataract Catastrophes, Bimanual Phaco: Mastering the Phakonit/MICS Technique, Dry Eye: A Practical Guide to Ocular Surface Disorders and Stem Cell Surgery and Presbyopia: A Surgical Textbook. He can be reached at aehl19c@gmail.com; website: www.dragarwal.com.
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