Over the years, indications for evisceration have expanded to include both infectious and noninfectious intraocular inflammation, resulting in a total loss of vision, end-stage glaucoma, and post-traumatic severe ocular injuries.9 Compared with enucleation, evisceration is easier, quicker, and less disruptive to tissues, therefore leading to fewer complications and better ocular motility and eventual cosmesis.10, 11 It also protects against the theoretical risk of meningitis after enucleation of an infected eye.12 Evisceration includes placing an orbital implant within the scleral shell for improved postoperative cosmetic rehabilitation of the socket;13, 14 however, this procedure has been associated with many complications, including decreased motility, cosmetically unacceptable enophthalmos (due to inadequate volume replacement), infection, implant migration, exposure, and extrusion.9 Above all, implant extrusion is one of frequent and severe complications.1, 13, 15
Implant extrusion following evisceration was first noted in 1939 when Burch3 reported a 25% extrusion rate. Researchers have attempted to identify risk factors for implant extrusion after evisceration, of which endophthalmitis was considered the most dominant.2, 5, 6 As a consequence, many have advocated for no primary implant in cases of endophthalmitis and have argued that an implant should only be inserted as a secondary procedure, months or years after evisceration.2, 6 Some surgeons prefer not to perform evisceration until the ocular infection is eradicated.5 Eliminating infection before implant insertion has led to delayed primary wound closure in patients with an infected wound.12, 16 Although delayed primary closure has certain theoretical advantages, primary implantation of orbital implants avoids prolonged hospitalization and the need for two surgeries.8 For this reason, some in the field prefer to take the small risk of implant extrusion, as opposed to not placing an implant or subjecting the patient to a secondary procedure.7, 17 Studies of primary implant placement in infected eyes undergoing evisceration report low complication rates and good implant retention.12, 18–21 Practice patterns have recently shifted toward the use of primary orbital implants in these patients.22
In the current study, no implant extrusion was observed in the non-endophthalmitis group (Table 2),18 similar to the outcomes reported in previous studies;17, 22 thus, there appears to be no problem with the surgical technique itself. The implant extrusion rate in the endophthalmitis group was 8.2%, and the difference in implant extrusion rates between the two study groups (endophthalmitis versus non-endophthalmitis) was statistically significant. Thus, endophthalmitis is a potential risk factor for implant extrusion, which is consistent with previous studies.5, 6, 12, 16
There is still a debate as to whether primary or secondary implantation is better in patients with endophthalmitis. The primary implant technique is simple, more cost-effective, and more convenient for patients.18 However, if implant extrusion occurs, it will result in more surgeries and more pain for the patient, at a greater cost than the planned secondary implantation.6 To our knowledge, no previous studies have attempted to identify risk factors for extrusion through univariate and multivariate analyses. Gupta et al.28 attempted to analyze risk factors for implant extrusion using univariate analysis, but their results were inconclusive. Here, we identified the risks through univariate analysis of hypothetical risk factors, on which multivariate analysis was performed to consider the interactions among factors. Using univariate logistic regression analysis, endophthalmitis (OR, 15.49; 95% CI, 1.7 to 2038.56; p = 0.010) and endogenous endophthalmitis (OR, 18.73; 95% CI, 3.22 to 125.21; p = 0.002) were risk factors for implant extrusion (Table 3). However, when analyzed in multivariate analysis, neither were critical risk factors for implant extrusion.
Many authorities believe that eyes infected with a virulent protease-secreting organism, such as Pseudomonas, are at higher risk of implant extrusion.19, 24, 25 However, it is difficult to use this information in clinical practice. It takes a long time to detect causative organisms before surgery, and it is possible that the bacteria cannot be detected. Instead, preoperative CT findings can easily and quickly predict the probability of extrusion after evisceration with primary implantation. In our study, orbital cellulitis in the CT results (OR, 320.54; 95% CI, 29.67 to 44801.64; p < 0.001) was a risk factor for implant extrusion in univariate logistic regression analysis, and multiple logistic regression analysis revealed that orbital cellulitis was the only risk factor for extrusion (OR, 52.98; 95% CI, 2.18 to 15367.34; p = 0.009) (Table 3).
There is also debate regarding whether the implant type affects extrusion.17, 29 Some studies have reported that porous implants cause less extrusion,29 while others have reported the opposite.17 In our study, there was no significant difference in the extrusion rate between porous and non-porous groups. Our comparison of the rate of extrusion according to implant type revealed that hydroxyapatite (OR, 0.07; 95% CI, 0.00 to 0.66, p = 0.016) was a negative risk factor for implant extrusion in the univariate logistic regression analysis (Table 3). On the other hand, the non-porous silicone implant had a borderline significance with an OR of 4.14. We speculate that the result of low extrusion risk in patients using hydroxyapatite implants demonstrated selection bias. When the conjunctival of the Tenon’s capsule is severely inflamed, wound healing may be impaired and increase the likelihood of extrusion. Although there is a debate about endophthalmitis as risk factor for extrusion, inexpensive non-porous silicone implants were actively recommended for patients with endophthalmitis. After non-porous silicone implants became no longer available in Korea, inexpensive types of implant among the porous implants were recommended and frequently used, cutting down the usage of the relatively expensive Hydroxyapatite implants. If non-porous silicone implants were still available, it is highly expected that only non-porous silicone implants would be used in all five exposed cases. In this case, the OR of the non-porous silicone implant would have been higher and statistically significant. Therefore, a randomized prospective study is necessary to evaluate the risk rate according to implant type without selection bias.
Karesh and Dresner31 argued that implant extrusion is related to the placement of an oversized implant. In contrast, Liu et al.19 reported that a smaller implant did not necessarily involve a lower extrusion risk. In the current study, the axial length of the fellow eye did not differ between extrusion and non-extrusion groups. However, the size of the implant was statistically significantly smaller in the group with extrusion (p = 0.001). Using univariate logistic regression analysis, implant size (OR, 0.50; 95% CI, 0.30 to 0.79, p = 0.004) was a negative risk factor for implant extrusion, but it was not a risk factor using multivariate analysis. Implant size also appears to be affected by selection bias, similar to implant type. In general, for optimal cosmetic results, the largest implant is selected without creating undue tension in the wound closure. However, for patients who appear to be at high risk of extrusion during surgery, there is the possibility that the surgeon would choose a smaller-sized implant than usual to reduce the risk.
This study is the first to apply multivariate analysis to determine whether endophthalmitis is a risk factor for extrusion. However, it had several limitations. First, the patients were distributed over a 15-year period. This should not have a significant impact on the results, as the patients in this study underwent surgery by a single surgeon and there was no significant change in the surgical technique during this period. Second, despite being a risk factor, the numbers of patients with endogenous endophthalmitis and orbital cellulitis were relatively small. Recruiting more patients and additional analyses would yield statistically much stronger results. Lastly, it is likely that there was a selection bias in the results. Our univariate analysis results indicated that size and type of implant are risk factors for extrusion, although they were not identified as risk factors using multivariate analysis. A prospective, randomized study may clarify the influence of the implant on extrusion.
In conclusion, evisceration with primary orbital implantation is a feasible option in endophthalmitis; however, the risk of extrusion should be taken into consideration. In particular, when performing evisceration in a patient with orbital cellulitis, it is desirable to perform secondary implantation only after any infection is controlled.