Previous studies have described anterior segment OCT as a valuable technique in the clinical and preoperative assessment of patients with Peters’ anomaly. In this study, we performed OCT on such patients after they underwent PK to observe the microstructure of the anterior segment during the postoperative follow-up period. We found that 83.1% of the operated eyes had postoperative AS, which varied in range and site. Over half of the cases developed synechiae within two quadrants. The adherent iris strands were most commonly seen at the site of the internal GHJs, while other sites included the peripheral host cornea with or without angle synechiae.
AS is a frequent complication encountered after PK. Peripheral AS may cause secondary angle-closure glaucoma and lead to graft failure. AS at the graft-host interface was regarded as a poor prognositic factor, being associated with the loss of graft clarity via interfering with the adequate wound healing of the posterior aspect of the cornea and promoting endothelial disturbances, retrocorneal membranes, and corneal vascularization, which facilitated immune rejection.13, 14 The reported incidence of peripheral AS after PK in adult patients varied between 8% and 46.7%, with or without IOP elevation.15–17 Our results revealed a considerably higher prevalence rate of postoperative AS in infants and children with Peters’ anomaly.
Pediatric PK is more complicated and technically more difficult than adult PK due to decreased scleral rigidity, alarming posterior pressure, anterior movement of the lens-iris diaphragm and increased fibrin release, which may lead to the adherence of the iris to the peripheral cornea and the wound. The present study found that preexisting iris-corneal adhesion and a shallow anterior chamber were risk factors for postoperative synechieae. Corneal opacification, along with iridocorneal adhesions, is one of the major characteristics of Peters’ anomaly. In addition, such patients have smaller anterior segment dimensions. During surgery, they are more likely to experience hemorrhages and injury to the iris, which may intensify the inflammatory response and fibrinous reaction, causing postoperative AS. On the other hand, it is hypothesized that due to long-standing adhesion, the iris may become flaccid with advanced atrophic changes and tends to retain this abnormal position, leading to the reformation of synechiae postoperatively.18 Because patients with severe disease often had larger areas of preexisting iris-corneal touch and smaller ACD values,9 they were found to be more susceptible to generate postoperative AS.
Preexisting iridocorneal adhesion has been identified as a poor prognostic factor. Yang et al reported that the graft failure rate was higher in eyes with preexisting iridocorneal adhesions over two quadrants in cases of Peters’ anomaly.19 Other studies have found that preoperative diagnoses, such as adherent leukoma and infectious keratitis, featured with preexisting iridocorneal adhesions and inflamed floppy iris, increased the odds of postoperative AS and secondary angle-closure glaucoma.20–22 It is paramount to perform synechiolysis after the wound is closed to help prevent postoperative AS formation. Despite optimal synechiolysis, a high prevalence rate of postoperative AS was still observed in the current study.
Other factors contributing to the formation of postoperative AS in these patients included small corneal size and small graft size. In eyes with Peters’ anomaly, the size of the donor tissue was tailored to the size of the opacity and of the host cornea. Because of the increased elasticity of the infant cornea and sclera, it is recommended that the diameter of the donor tissue be 0.5-1.0 mm larger than the recipient opening.23 In the current study, 95.8% of the cases had a graft-host disparity within this range. Also, there was a significant correlation between the graft size and the recipient corneal size (p=0.005). Eyes grafted larger donor cornea buttons may have larger corneal sizes and thus allow adequate space of the anterior segment during the process of wound healing and wound retraction, and may help reduce the risk of postoperative synechiae. Moreover, a negative correlation was identified between the width of the host corneal bed and quadrants of postoperative AS. This suggested that the narrower the host corneal bed was, the closer the surgical manipulation and the GHJs were to the corneal limbus, which may induce larger amounts of AS.
In this study, an association between malapposition of the internal GHJ and postoperative AS was also observed. The prevalence of GHJ malappositions in the patient population was 60.2%, which was similar to that previously reported in cases of adult PK.12, 24 AS formation might follow such malapposition because the iris tends to adhere to bare stroma more readily.25 Proper wound apposition and meticulous wound closure are essential to avoid iris incarceration in the wound intraoperatively and may prevent or lessen the risk of postoperative synechiae.17, 25 However, achieving proper tissue apposition and wound closure can be difficult due to thinner and more pliable corneal tissue, anterior displacement of the lens-iris diaphragm, and wound retraction. Graft-host misalignment may be induced and increase the chances of adherence of the iris to the surgical wound.
The limitations of this study are mainly related to its short-term nature. Postoperative OCT scans were obtained only when young patients came for suture removal, due to the requirement of general anesthesia during examination. After the sutures were completely removed, we lost track of the OCT evaluations for these children. In cases where AS formation is a concern, the areas involved should be closely watched for the development of IOP elevation, graft rejection or other postoperative complications. Hence, a portable hand-held OCT device is recommended in routine and long-term follow-ups to observe the AS progression, provide precise data about the anterior segment structures, and clarify the effect of postoperative AS on the prognosis of PK in Peters’ anomaly patients. Second, in cases with thick and dense opacity in the peripheral cornea and the limbus area, the current OCT scanning system (wavelength = 830 nm) limited the visualization of the structures in the anterior chamber angle. A longer-wavelength OCT modality that allows for higher penetration and reproducible measurements may be useful and complementary in prognostic analysis, as well as guiding postoperative management.
In conclusion, this retrospective study provides insights into the characteristics of anterior synechiae after PK in pediatric patients with Peters’ anomaly. We demonstrated that AS was a common postoperative complication in these patients, and that several risk factors were associated with its occurrence. The results allow predictions to be made regarding which patients are more likely to form postoperative AS and help clinicians to evaluate and manage patients with this rare yet challenging disease. Still, the prognostic effects of postoperative AS on graft survival and visual success remain to be determined. Anterior segment OCT allows characterization of the type and the extent of postoperative AS, thus it is recommended during the clinical and surgical follow-up of these patients to help reduce associated morbidity.