Therapeutic keratoplasty is indicated in cases in which infectious corneal disease progresses despite maximal medical therapy, the globe integrity and useful vision are compromised[8, 11, 12]. We report the outcome of modified tectonic corneoscleral graft (TCG) with corneal infections involving the limbus and partial sclera. The existing literature looking particularly at this subset of patients is sparse. Moreover, these patients may be advised evisceration because of lower probability of a successful outcome and hopeless of eye salvation. This is one of the reasons why case-control studies cannot be designed. We hereby report our results of modified TCG in such devastating cases.
The finding of our study indicated that fungi was more common than bacteria, of which Fusarium was the most common. It was consistent with findings that fungal keratitis is the principal cause of blindness in Asia and Fusarium was the most common causal agent causing fungal keratitis in developing country[14, 15]. More attention should be paid to Pythium Insidiosum, which needs to be confirmed by DNA sequencing. It had high rate of postoperative recurrence and enucleation[16, 17]. In this series, two patients with enucleation were Pythium Insidiosum infection.
In the current cohort, surgical modifications were made compared with Hirst’s method to improve the success rate and reduce postoperative complications. First, the diseased cornea along the corneal limbus and adjacent infected sclera were excised, to ensure that all pathogens were removed. Second, the fresh donor cornea with a thinned scleral ring was overlapped and fixed on the implant bed with sutures, and the anterior chamber was reformed with viscoelastic agent. It not only reduces the difficulty of the side-by-side suture at corneal limbus, but also reduces the risk of secondary glaucoma due to the 360° formation of anterior chamber with viscoelastic agents. Remarkable improvement was noted that the IOP of all patients was within the normal range after surgery. Third, the donor was retained from 2mm scleral ring posterior to the limbus, making it possible to reconstruct the anterior segment structure.
The procedure is effective in eradicating infection, salvaging the eyeball and saving some useful vision. Previous reports revealed that the recurrence rate of infection ranged from 30.4–65.0% for end stage corneal disease[8, 9, 12]. Of those receiving therapeutic large-diameter keratoplasty, there may still be cases where the infection cannot be completely removed. In this study, there was a much better exception postoperatively that 23/25 cases got rid of infection and restored anatomic integrity of the eye. In addition, some studies have demonstrated poor visual outcomes because of the well-known risks of surgery and the consequences of the infectious disease itself[8, 10, 12]. Another study showed that large-diameter penetrating keratoplasty may reduce postoperative astigmatism and improve visual acuity outcomes. In the present series, the rate of monocular blindness declined from 100–57%. There were 10 patients with best corrected visual acuity greater than 0.05. In 3 cases, the eyeballs were preserved, but the visual acuity was hand movement, which was related to the complicated cataract caused by inflammation and postoperative complications.
Previous studies of penetrating keratoplasty for the treatment of infectious keratitis have shown graft survival rates of 78.4%-95.0%[20–22]. But few reports have reported graft survival for large-diameter penetrating keratoplasty, which may be related to the rare cases of severe infection. Our study showed the survival of ocular surface stability declined gradually with time, from 73.6% at 1 year to 43.9% at 3 years. At the final follow-up (mean, 17.5±8.9 months), 84.0% of the eyes had a stable ocular surface, indicating better long-term results.
It is noteworthy that the occurrence of complications that may lead to transplantation failure, especially graft rejection [23, 24]. High risk factors include; (1) ultra-large diameter corneal graft[25, 26], (2) severe infection and (3) fungal infection in which topical glucocorticoids are avoided in the early post-surgical period[28, 29]. For preventing graft rejection, we used tacrolimus and glucocorticoids locally with concentration gradients. In this series, the incidence rate of immune rejection was 36%, and higher than that of conventional penetrating keratoplasty (5%-18%) [24, 30]. However, our further analysis, we found that 16.7% of the patients did not have regular follow-ups and did not use the topical drugs regularly. 4 cases occurred immune rejection of corneal grafts 2 weeks to 1 month after surgery. All the four patients with fungal corneal ulcer did not receive topical glucocorticoids in the early postoperative period, which may be another reason for early postoperative immune rejection. Thus, tacrolimus is a potent immunosuppressant[31–33] and should be the first choice for antirejection after TCG. In addition, good compliance also reduces immune rejection after successful operation.
This study still needs to increase the number of cases and extend the follow-up time. The disadvantage is that the number of cases is small, as a single case may have a large impact on the outcome, so survival analysis of implant transparency and comparison of fungal and bacterial outcomes have not been performed.
In summary, as is evident from our study, modified TCG with scleral ring was an effective way to avoid primary evisceration, provide structural stability and preserve useful vision for devastating corneal ulcers involving limbus and sclera. Regular application of tacrolimus, timely addition of glucocorticoid and good compliance may decrease the postoperative course challenging.