Key words : Corneal patch graft, Infectious perforation, Inflammatory perforation

Introduction

Corneal perforation is a serious emergency that may develop due to trauma, infection, or inflammation.¹ It has severe complications, such as cataract formation, glaucoma development, and endophthalmitis. Ensuring ocular integrity is a priority when treating corneal perforations.² Conservative treatments such as bandage contact lenses and a pressure patch can be used to buffer the leak. In cases where conservative approaches are insufficient, surgical treatments such as fibrin glue, multilayer amniotic membrane transplant, patch grafting of conjunctival flaps, and tectonic penetrating keratoplasty can be applied.^1,3 The preferred method of treatment mostly depends on the size and location of the perforation site. Although adhesives and plugs with relatively low tissue resistance, such as the amniotic membrane, seem to be beneficial in small perforations, use of corneal tissues, especially in the repair of 2-mm and 3-mm and larger perforation areas, provides more effective and successful results.⁴

In the light of the fact that the number of patients waiting for transplant per 1 donor cornea in the world is still 70, corneoscleral rim application in corneal perforations seems more accessible and logical versus tectonic corneal transplant, because tectonic corneal transplant is known to have a lower success rate, especially in the acute approach.⁵ In addition, patch grafting in inflammatory and infectious pathologies also contributes to ensure the integrity of the globe with a healthy structure by removing necrotic debris.⁶

Although corneoscleral patch grafting is a known method, the number of published studies in the related literature is limited. In the present study, we present the demographic and clinical characteristics of corneal perforations that were successfully controlled with corneoscleral patch grafts.

Materials and Methods

Our study was carried out after the approval of the ethics committee and in compliance with the principles of the Declaration of Helsinki. The data of patients with corneal perforation who underwent corneal or corneoscleral patch grafting from 2016 to 2021 were evaluated retrospectively.

Age, sex, perforation etiology, first and last examination notes, tissue type used in surgery, tissue size, follow-up time, and additional surgical interventions were evaluated from the records. The clinical features of the patients were examined from the anterior segment photographs of the eyes.

All patch grafts were prepared from rims that remained after penetrating keratoplasty of donor corneas obtained from the eye bank. Rims were stored in hypothermic corneal transplant solution until the time of the surgery, and prepared grafts included full-thickness tissue. In the cases included in this study, due to the presence of perforation, full-thickness patch graft was used instead of lamellar patch graft, which is less immunogenic. After removal of the necrotic tissue in the perforation area, measurements were conducted with a caliper, and the size of the patch tissue suitable for the wound architecture was determined after marking with a sterile pen. Manual adjustment according to the architecture of the wound area was made with micro scissors and forceps. No special equipment was used (for example, no punches were used). The prepared patch grafts were transferred to the recipient bed with separate 10-0 sutures. Postoperatively, all patients were hospitalized until the wound healing was completed without any leakage, which was a minimum 5 days. After epithelial healing, apart from topical wide-spectrum antibiotic drops started on the first day, topical steroid instillation was added. A minimum of 6 months of follow-up was organized after the patients’ discharge to evaluate further complications or requirements.

Results

Fifteen patients were included in the study. The mean age was 64.9 ± 19.7 years (range, 15-81 years), and the female-to-male ratio was 0.85. The mean follow-up period was 31.5 ± 24.5 months (range, 6-61 months). The mean value for best corrected visual acuities, measured as logarithm of the minimum angle of resolution (logMAR score) was 1.80 ± 1.02 logMAR (range, 3.0-0.2 logMAR) at the first preoperative examination and 1.83 ± 1.06 logMAR (range, 3.0-0.2 logMAR) at the final follow-up examination.

Corneoscleral patches were used in 6 patients (40%), and corneal patches were used in the remaining 9 patients (60%) (Figure 1). The mean value of the longest diameter of the patch graft was 4.6 ± 1.9 mm (range, 2-8 mm). The minimum perfo-ration size was 2 mm. Major surgical indications for patch use were classified into 3 groups: infection, inflammation, and trauma. Inflammatory causes (n = 7; 46.7%) were the most common causes, followed by infectious (n = 6; 40%) and traumatic causes (n = 2; 13.3%). Details for causes of perforations are shown in Table 1.

From the patient data, we observed that the globe integrity was preserved in nearly all of the eyes during the follow-up period, except for 1 patient with rheumatoid arthritis whose eye required limbal conjunctival resection and regrafting to overcome wound leakage and graft melting at the second week (Figure 2). Although no other complications due to suture or any infective cause were observed, additional surgical procedures were required in 5 eyes: lateral permanent tarsorrhaphy (3 eyes) and penetrating keratoplasty (2 eyes) for visual rehabilitation. None of the patients developed glaucoma; however, 2 eyes required cataract surgery. Both cataract cases were unrelated to the acute perforation and were performed 6 months and 1 year, respectively, after patch grafting.

Before the patch graft procedure, 9 of the patients received amniotic membrane transplants, which could not control the perforation. No other tectonic attempts were performed (eg, no fibrin glue application), because all patients had a wound size greater than 2 mm. According to the patient data, for infectious perforations treated with wide-spectrum antibiotics and for perforations with inflammatory causes, the patients were given topical immunosup-pressants. All grafts were made after standard medical treatment proved insufficient.

Discussion

Repair of acute corneal perforations requires subs-tantial knowledge of multiple surgical approaches. When conservative interventions fail, methods such as tissue adhesive, amniotic membrane transplant, conjunctival flaps, patch grafts, and tectonic penetrating keratoplasty are applied, depending on the size of the defect.^1,2 Patch grafts are crucial to successful treatment of perforations with relatively large tissue loss.⁷ In the present study, we observed that the patch-graft method is effective in the allocation of acute corneal perforation.

The etiology of corneal perforations shows the main causes to be inflammation, trauma, and infections. Although corneal transplant is preferred in large and central perforations, the long-term success rate for such cases is expected to be low and may require multiple transplant attempts when emergency tectonic keratoplasty is applied to the eye with intense inflammation.^8,9 To overcome the corneal graft limitation, the use of patch grafts in the repair of corneal perforations has been recognized as an important option in corneal transplant clinics. In the patch-graft approach, custom-sized patches prepared in accordance with the wound architecture may provide greater success.^6,10

Infectious etiologies are the main cause of corneal perforations, especially in developing countries. Colonization of microorganisms, especially those that demonstrate resistance against standard treatment agents, can cause corneal lysis with severe tissue loss that could require further interventions.^1,11 In a study from India, Vanathi and colleagues¹² reported that the main reason for surgical interventions secondary to perforations is keratitis. Although in the current study infectious perforation etiology seems to be highly important, the main cause remains inflammation. Rush and colleagues¹³ presented their results of penetrating keratoplasty in corneal perforation and defined sterile and inflammatory causes as the most common surgical indication for repair after perforation, with specific emphasis on inflammatory perforations secondary to neurotrophic keratopathy and autoimmune diseases. Inflammatory diseases may cause cytokines and chemokines in tear film to penetrate deep into corneal tissues, which may lead to loss of the barrier function of the sphere.¹⁴ In the present study, infection and inflammation were found to be the primary etiological factors. Even for successful surgery, additional procedures may be required if the excessive inflammation cannot be controlled. A patient in our study required further intervention in the form of limbal conjunctival resection and regrafting.

Another important cause of perforations is penetrating corneal injuries.¹⁵ Additional surgical procedures may be needed for such cases, especially in cases where tissue loss is present and cannot be repaired with sutures alone. Surgical methods used in penetrating injuries are tissue adhesives and amniotic membrane transplant. Although tissue adhesives seem to be successful in repair, these can be disadvantageous from time to time due to their opaque structure, potential to cause secondary inflammation, implementation difficulties, and high financial cost.^1,16 Patch grafts prepared in a special size that is specific for the injured area are becoming more accessible, especially in clinics where keratoplasty is performed. In the present study, patch grafts were applied to 2 trauma-related corneal perforations.

There are also rarer causes for corneal perforations that are not included in this study. Iatrogenic reasons or other inflammation-related cases may lead to corneal perforations. Iatrogenic causes include perforations after surgeries such as glaucoma surgery and pterygium excisions.^17-19 In such cases, perforation may be seen either during surgery or after dellen formation. Again, in clinics where corneal transplants are already performed, patch grafting can be an easily applicable alternative.

Various modifications have been described in the literature to increase the success of patch-graft applications. The main goal is to achieve the same architecture as the damaged tissue in its original form, by maintaining an appropriate apposition between the graft and the host. As in the present study, the general method is to use a caliper to measure the exact diameter of the damaged tissue and freehand dissection. Although Vanathi and colleagues¹² reported on hand dissection, Wong and colleagues²⁰ prepared stapled lamellar grafts using a crescent blade for clamped edges between 2 sterile fabrics. Another recommended approach is to use a trephine with an appropriate diameter. Kerenyi and Suveges²¹ described eccentric and biconvex keratoplasty. Although this method seems like a viable alternative, in fact, there is no established method for use of trephines, and its success rate is low. In addition, in light of the low rate of corneal donation, using almost all donor tissue does not seem to be a reasonable option. Some authors, such as Chai and colleagues,²² have used an artificial anterior chamber to generate donor tissue for the 3-dimensional structure of the wound, which again requires a complex approach. In the present study, full-thickness grafts were used rather than lamellar grafts. Rejection may be a concern for full-thickness grafts; however, the main advantage is the ease of the preparation. Lamellar dissection requires more surgical experience, and remaining rim tissues may be inappropriate for further attempts if the first procedure is not successful.

The advantage of the current study is that freehand dissection requires no special equipment and is an easily accessible method for using discarded tissue and residual tissue from donor corneas. Accessibility to the rims highlights this method, even if it requires a highly skilled surgeon with complex suturing ability to properly close the wound.

Although patch-graft applications are effective in corneal perforation repair, the procedure has some significant disadvantages, such as preparation and application of a patch according to the wound architecture, which requires substantial surgical experience. Also, as for any transplanted tissue, there remains the potential for a rejection reaction.¹ We observed no rejection reaction in the current study, but this may be associated with appropriate and long-term topical steroid therapy following epithelial healing.

Likewise, in patch grafts, especially in paracentral and central transplants, high level visual acuity may be impaired due to scarring.⁷ In the current study, visual acuity was preserved after surgery, as judged by a comparison of the mean values demonstrated by patients preoperatively versus postoperatively; however, better visual outcomes have been reported in the literature. Vanathi and colleagues¹² achieved a 1-line improvement, and Soong and colleagues²³ stated differing results between cases. Although acute application of patch-graft treatment may prevent further complications, penetrating keratoplasty may be required for visual rehabilitation in the subsequent follow-up. However, as expected, graft survival is likely to be higher in this type of transplant, which is typically performed under elective conditions. In the present study, penetrating keratoplasty was applied to 2 patients to provide visual rehabilitation during their follow-up. In addition, in the case of corneal perforation as the cause of visual loss, cataract may develop with the involvement of the capsule in the acute stage or the associated intense inflammation may trigger the development of cataract in the follow-up process.²⁴ In this study, it was observed that lens opacification progressed at a level that required cataract surgery in the first year after surgery in 2 patients.

Limitations
The main limitations of our study are (1) its retrospective nature and (2) lack of a control group. Prospective studies to compare other methods are needed.

Conclusions

Patch grafts are a valuable and effective alternative method to preserve acute sphere integrity in corneal perforations with tissue loss. The patch graft can be specially prepared according to the size of the wound and tissue loss, and tissues are easily obtained in clinics where keratoplasty is performed.

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