Use of deep anterior lamellar keratoplasty (DALK) has been increasing in recent years, and DALK is considered the first therapeutic option, even before penetrating keratoplasty (PKP), for some pathologies, such as advanced keratoconus.1 The integrity of the corneal endothelium is essential in DALK patients as is the status of the ocular surface (tear film, eyelids, conjunctive, limbus). Late graft rejection in anterior lamellar keratoplasty has been described as vascular proliferation into the deep and superficial stroma.2 Therefore, the presence of blood vessels in the donor should be considered a contraindication to lamellar surgery as well as a confirmed risk factor in PKP.
The Krumeich intrastromal corneal ring (ICR) was initially designed to decrease postoperative corneal astigmatism, stabilize refraction, accelerate healing, and, possibly, reduce immune reactions,3 but a secondary property was seen: the ability to stop vascular ingrowth in the donor's cornea. The ICR is made of a cobalt–titanium–molybdenum alloy, which in theory reduced postoperative astigmatism, an assertion that could not be demonstrated with statistical significance.3
We present 2 cases of severe irregular astigmatism associated with deep and superficial vascularization in which DALK was performed, placing an ICR in the donor–recipient union as a prophylactic measure to prevent vascularization of the graft or the interface. Both patients had traumatic unilateral corneal leucoma and corneal vascularization, and endothelial integrity was verified in both eyes by endothelial cell count.
A 38-year-old man presented with a corneal leucoma, thinning, and deep and superficial stromal vascularization due to a previous severe ocular burn in the right eye (Figure 1, A). The corrected distance visual acuity (CDVA) (−5.00) was hand motion (HM). Two amniotic membrane transplants had been performed during the acute phase to avoid perforation and to diminish the inflammatory reaction (Figure 1, B). After the eye was quiet, DALK was proposed to treat the corneal irregularity and opacities.
The procedure was performed under local anesthesia using an 8.0 mm ICR (Humanoptics AG) in the deep stroma. Donor–recipient sizes were 8.5 to 8.0 mm. Pre-descemetic space was reached by manual dissection, leaving less than 100 μm of the recipient's stroma. Sixteen 10-0 nylon single interrupted sutures were used to suture the graft. Routine postoperative treatment consisted of dexamethasone and tobramycin eyedrops, sodium hyaluronate artificial tears, and sodium chloride eyedrops in a tapered therapeutic regimen.
The patient was monitored at 24 hours; 1, 2, and 4 weeks; and then monthly. On each visit, visual acuity was checked and supplementary tests were performed. Anterior segment photography, Sirius Scheimpflug anterior segment examination topography, and Cirrus-HD OCT 500 (Carl Zeiss Meditec AG) images were captured to control corneal thickness, measure the depth at which the ring was located, and verify eventual displacements.
Four months after the lamellar transplantation, the sutures were removed. Cataract surgery was performed after 10 months. At that time, the CDVA (−3.50 +2.00 × 40) was 20/30 in the right eye. After 1 year, there was no evidence of deep or superficial blood vessels ingrowth during the follow-up time, even though there was an area of conjunctivalization (the epithelium, not vessels) (Figure 1, C and D) secondary to a sectorial limbal deficiency. Treatment with corticosteroids was discontinued after all sutures had been removed, and the patient used only artificial tears 3 to 4 times a day.
A 52-year-old woman presented with a 1-year history of cortico-dependent recurrent aseptic keratitis secondary to a foreign body (fish scale) in the left eye. She abandoned the treatment and returned 8 months later with a severe lipoid degeneration (Figure 2, A) and large deep stromal vessels in the lower nasal quadrant (Figure 2, B) associated with corneal thinning. The CDVA (−1.00 +7.50 × 10) was HM. Deep anterior lamellar keratoplasty and an 8.0 mm ICR were implanted with the same follow-up and therapeutic protocol as in Case 1, and manual dissection was also used to reach the predescemetic stroma.
One month after the procedure, inferonasal vessel regression was observed. After 6 months, all the sutures were removed; 2 months later, cataract surgery was performed to treat the residual refractive defect. The final CDVA (−6.00 +12.00 × 175) was 20/40. During the 14-month follow-up, no stromal vascularization, edema, or signs of rejection were seen.
The risk for a graft rejection in DALK is extremely low, but it has been described as a late complication or as an early or mid-term rejection episode in a small case series (4 eyes, 3 patients),2 presenting as vascularization. Although most occurrences resolve with topical steroid treatment, graft rejection can cause poor visual acuity, corneal edema, or chronic opacities that require another keratoplasty procedure. Topical steroids may produce well-known ocular side effects. Advising DALK patients of this potential, although rare, complication has been suggested.4
In a large series of 101 cases in which an ICR was used,3 radially growing vessels were seen to deviate when the vessels reached the edge of the ring, a circumstance that was probably related to an immune phenomena. The ring is made of a cobalt–titanium–molybdenum alloy. Immune reactions secondary to various metals have been described,5 as have retinal, optic nerve, and choroidal toxicity of cobalt, reported in patients with specific hip prosthetic models but not in the anterior segment.6 To our knowledge, there have been no previous reports of toxicity from this ICR, and the absence of in vitro toxicity of the ICR alloy has been demonstrated.7
Based on our previous experience with the Krumeich ICR in PKP, we implanted the device in 2 high-risk DALK patients to prevent interface or stromal graft blood vessel ingrowth. After 1 year of follow-up, the patients did not need treatment with topical steroids and the previously observed vascularization diminished and did not exceed the ring limits centripetally. No episode of graft, stromal, or epithelial rejection has occurred. Both patients use only artificial tears as needed.
To our knowledge, there have been no reports of the use of this ICR in anterior lamellar keratoplasty. Further investigation in a large case series and a prospective study should be done, but the results in this case series encourage us to use the Krumeich ring as a prophylactic device to reduce the use of postoperative steroid eyedrops and prevent vascular ingrowth in selected patients having DALK.
None of the authors has a financial or proprietary interest in any material or method mentioned.
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