Clinical Manifestations, Outcomes, and Histopathology of Recurrent Uveitis in Patients Underwent Pupil Coroplasty Combined with Cataract Surgery

Purposes: This study was aimed to evaluate the clinical manifestations of recurrent uveitis in patients underwent pupil coroplasty combined with cataract surgery, and discovery the histopathological changes of iris tissues. Methods: There 28 patients with recurrent uveitis-induced cataract, who had underwent pupil coroplasty, phacoemulsication, and intraocular lens implantation were enrolled in this study. The clinical manifestations and outcomes of the enrolled patients were analyzed. The histopathological changes of iris tissues were observed by hematoxylin and eosin (HE) staining. Results: The uveitis were idiopathic in 89.29% cases (n = 25). Before the surgery, 20 cases had no topical medication for at least 3 months. The preoperative BCVA was > 0.5 in all cases. During the follow-up of 5-10 years, no recurrence of uveitis was found in 96.43% cases (n = 27). Uveitis only recurred in one case along with the onset of ankylosing spondylitis at the 6 th week after the surgery. HE staining showed obvious atrophy of iris stroma in all samples. The hyperplasia of pigment cells was observed in the pigment epithelium (n = 9) and even invaded into stroma (n = 19). The inltration of inammatory cells in iris tissues was found in 7 cases, and neovascularization in the surface of the iris was found in 2 cases. Conclusion: Recurrent uveitis was characterized by the atrophy of iris stroma, and some cases also exhibited hyperplasia of pigment cells and inltration of inammatory cells. The surgery proposed in this study can effectively prevent the long-term recurrence of uveitis.


Background
Uveitis is a severe in ammatory ocular disease, which can lead to visual impairment and even irreversible blindness [28]. The prevalence of uveitis depends upon multiple factors, including the age, sex, race, geographic distribution, environment, genetics, and social habits [25]. The estimated annual incidence of uveitis is about 17-52 persons per 100,000 people, and a prevalence of approximately 38-284 cases per 100,000 people in some developed countries [9,15,18]. Uveitis is usually classi ed based on anatomical location, duration and course of in ammation, and nature of in ammation. Anterior uveitis is the most prevalent form of uveitis, accounting for approximately > 50% cases [7]. In clinical, the uveitis is idiopathic in most cases (48-70%), and the traumatic, in ammatory, and infectious immunologic disorders can also induce the occurrence of uveitis [10]. Until now, the main treatment strategy for uveitis is to protect the ocular tissues from damage through inhibiting in ammation, and activating immunosuppression to stop fueling T cell reactivity [26]. Topical corticosteroid is usually applied as the rst-line therapy for uveitis. Conventional immunomodulatory agents are added as second-line therapy utilized for their durable control of ocular in ammation and as a steroid-sparing agent [24]. However, uveitis is easy to relapse even after effective treatment due to the reappearance of infectious organisms and the localization of immune complexes in the uveal tract [3,14].
Uveitis can lead to a variety of complications, such as cataract, retinal neovascularization, choroiorentianl scars, cystoid macular edema, glaucoma/hypertension, epiretinal membranes, and retinal detachment [16]. Cataract is one of the most frequent complications of uveitis, and also a major cause of visual loss [5]. Both the intraocular in ammation and the long-term local or systemic use of corticosteroid contribute to the onset of cataract [6,12]. Cataract surgery is one of the most common outpatient procedures performed in China, but it is still a great challenge for patients with uveitis. The outcomes of cataract surgery in cases with uveitis is not predictable due to diverse factors, including surgical techniques, uncertain in ammatory sequelaes, and the variable and unpredictable reversibility of complications [5].
Patients with a history of uveitis are at higher risk for post-operative and recurrent in ammation following cataract surgery [4,8,12]. Before cataract surgery, the quiescent uveitis for at least three months is generally accepted as the minimum amount of time prior to surgical intervention [12]. Scrupulous case selection and aggressive control of pre and postoperative intraocular in ammation are also important for the postoperative success [27]. Recently, some encouraging outcomes on visual acuity were revealed in patients with uveitic cataract after surgery. For example, Singh K et al. have shown that the best corrected visual acuity (BCVA) is improved in 92.58% (n = 50) eyes and cystoidmacular edema was only found in 5% (n = 3) eyes after cataract surgery [22]. Yangzes S et al. have revealed that all children with uveitic cataract had signi cant improvement in BCVA post cataract surgery, and 55.17% (n = 32) eyes achieved a visual acuity of 20/40 or more [27]. Balta O et al. have found that the BCVA of 20/40 or better was achieved in 81.8% eyes (n = 18) in idiopathic anterior uveitis, 80.0% eyes (n = 8) in herpes simplex virusassociated anterior uveitis, 90.0% eyes (n = 9) in Fuchs' heterochromic iridocyclitis, and 100% (n = 13) in anterior uveitis associated with collagen vascular diseases over the 4 years of follow-up [1]. However, it is worth noting that uveitis is usually not quiescent after cataract surgery, and the recurrence of uveitis can be observed at an uncertain time [1,29].
In this study, we analyzed the baseline characteristics, preoperative intervention, postoperative care, outcome, and follow-up of 28 recurrent uveitis-suffered patients underwent pupil coroplasty, phacoemulsi cation with clear-cornea incision, and intraocular lens implantation. The histopathological changes of iris tissues in these patients were further analysed. Our ndings may reveal the underlying histopathological mechanism of recurrent uveitis, and provide guidance for the clinical treatment of recurrent uveitis.

Subjects
Total 28 patients underwent cataract surgeries, including pupil coroplasty, phacoemulsi cation with clearcornea incision, and intraocular lens implantation were screened from Beijing Tongren Hospital (Beijing, China) between July, 2009 and March, 2013. The cataract surgeries were performed by an experienced surgeon. The patients had suffered from anterior uveitis for twice at least, exhibiting pupil deformation and adhesion, and formation of organizational membrane. The uveitis-induced cataract (including agerelated cataract) was diagnosed as any lens opacity with visual acuity of 20/40 or less in the absence of other causes of visual loss according to Lens Opacities Classi cation System. The patients were followed up for 5-10 years. Both the preoperative and postoperative manifestations of the enrolled patients were analyzed, including the baseline characteristics, preoperative intervention, postoperative care, outcome, and follow-up. This study was approved by the ethics committee of Beijing Tongren Hospital in accordance with the Declaration of Helsinki (TRECKY2012-02). Written informed consents were obtained from all cases.

Histopathological examination
The iris tissues were collected from patients during cataract surgery. The isolated tissues were immediately xed in 10% formaldehyde, dehydrated in graded ethanol (70 to 100%), cleared in xylene, para n-embedded, and sliced at 5 μm. After dewaxed in xylene and rehydrated in graded ethanol, the tissue sections were stained with Hematoxylin and Eosin (HE). The histopathological change of iris tissues was observed under a microscope (IX71, Olympus, Japan).

Baseline characteristics and preoperative intervention
A total of 28 patients with an age range of 14-82 years old were enrolled in this study, among which 10 (35.71%) were males and 18 (64.29%) were females. All the enrolled patients had suffered from anterior uveitis. Except that in 2 cases with ankylosing spondylitis and 1 case with Sjogren's syndrome, the uveitis in the left 25 cases were all idiopathic. The uveitis-induced cataract (including age related cataract) was determined in all cases. There were 12 cases also had secondary glaucoma, and two of them lost control of intraocular pressure (intraocular pressure > 21 mmHg). The preoperative BCVA was 0.6 in 1 case, < 0.5 in 21 cases, and < 0.1 in 6 cases. All patients had no systemic medication within 3 months before the surgery. There 8 cases maintained topical eye drops for lowering intraocular pressure, and one of them also received eye drops of glucocorticoid for anti-in ammation at the same time. The other 20 patients had no topical medication for at least 3 months. In the perioperative period (3 days before the surgery), all cases received eye drops of levo oxacin four times a day. Two cases with uncontrolled intraocular pressure received intravenous injection of 20% mannitol. The intraocular pressure was immediately decreased to < 26 mmHg in 1 case after injection for 30 min, while it was not reduced to a normal level for another case (> 26 mmHg). By applying preoperative anterior chamber puncture, the following cataract surgery was successfully performed in this case. Iris hemorrhage was an intraoperative complication observed in 2 cases.

Postoperative care and follow-up
After surgery, all patients received 3 weeks of topical eye drops of tobramycin and dexamethasone for anti-in ammation, as well as topical eye drops of recombinant bovine basic broblast growth factor for nutrition. One case with aqueous are continued to use the above topical eye drops until the in ammation was disappeared (at the 6 th week after the surgery). There was an obvious improvement in visual gain of call cases, with a preoperative BCVA of > 0.5. These patients also exhibited normal intraocular pressure, right position of intraocular lens, and no occurrence of the complications of posterior cataract, corneal edema, and corneal decompensation. In addition, postoperative keratic precipitates was found in 2 cases, which was recovered within 1 week. During the follow-up of 5-10 years, no recurrence of uveitis was found in 27 cases (96.43%). Notably, uveitis recurred in one case with the onset of ankylosing spondylitis at the 6 th week after the surgery.

Histopathological manifestations
The histopathological changes of iris tissues were observed by HE staining. All samples exhibited obvious atrophy of iris stroma (Fig 1A and B). The hyperplasia of pigment cells was observed in the pigment epithelium (n = 9, 32.14%) and even invaded into stroma (n = 19, 67.86%) (Fig 1A and B). In addition, the in ltration of in ammatory cells in iris tissues was found in 7 cases (25.00%), and neovascularization in the surface of the iris was found in 2 cases (7.14%) (Fig 1A).

Discussion
Cataract is one of the most frequent complications of uveitis, which can be induced by chronic in ammatory response and use of corticosteroids [20]. Surgery is generally considered as the only effective therapeutic strategy for uveitis complicated with cataract, and the commonly used surgical strategies include extracapsular extraction, intracapsular extraction, lensectomy, and phacoemulsi cation [11]. At present, the surgical program for uveitic cataract mainly depends on the experience of doctors.
There is still no clear standard for the selection of scrupulous cases, indications and contraindications, surgical techniques, and operation time [5,27]. Foster et al. have described four indications for cataract surgery in patients with a history of uveitis, including phacoantigenic uveitis (active in ammation as a result of leak-age of lens proteins), visually signi cant cataract, cataract that impairs fundus assessment in cases with suspected fundus pathology, and cataract that precludes adequate visualization of the posterior segment in cases undergoing posterior segment surgical procedure [19]. In this study, all the enrolled patients with uveitis-induced cataract belong to the indication of visually signi cant cataract, and the phacoemulsi cation with clear-cornea incision combined with intraocular lens implantation were performed. Except the need of immediate mandatory cataract extraction for phacoantigenic uveitis, preoperatively control of in ammation for at least 3 months has become the guarantee of successful surgery. A meta-analysis based on 89 articles has shown that among uveitic eyes with quiet uveitis before cataract surgery, visual acuity of 20/40 or better was achieved in 68% following phacoemulsi cation, 72% following extracapsular cataract extraction, and 40% following pars plana lensectomy [13]. On the contrary, active uveitis at the time of cataract surgery was associated with worse visual outcomes [13]. Consistent with this consensus, all patients enrolled in this study had no systemic medication within 3 months, and 71.43% patients had no topical medication for at least 3 months before the surgery. Encouragingly, an obvious improvement in visual gain (BCVA > 0.5) was revealed in call cases. Glaucoma is another potentially blinding complication of uveitis, which can be induced by in ammation, secondary corticosteroid response, and angle abnormalities [23]. The surgery is thought to be necessary for glaucoma patients who cannot control the in ammation by drugs. Here, obvious improvement in visual gain was also revealed in one case maintaining topical eye drops of glucocorticoid before the surgery. The surgery may be conducive to the excretion of immune complexes, prostaglandins, and toxic substances in aqueous humor, thereby controlling intraocular pressure and in ammatory reaction.
Although the cataract surgery achieves relatively good outcome on visual gain in patients with uveitic cataract, postoperative complications and recurrence are still di cult problem to solve. For example, Rahman I et al. have shown that during a minimum follow-up of 5 years, 24% macular oedema or scarring, 96% posterior capsule opaci cation, 15% glaucoma drainage were found in 61 patients underwent cataract extraction with intraocular lens implantation [17]. Yangzes S et al. have revealed that the complications of visual axis opaci cation (39.66%), cystoid macular edema (31.03%), and glaucoma (8.62%) were common in total 58 eyes underwent cataract surgery [27]. Here, only the occurrence of keratic precipitates was found in 2 cases after the surgery. This complication may be attributed to the prolonged in ammatory response induced by local dysimmunity. There is nothing to worry that the keratic precipitates was recovered within 1 week. On the other hand, the recurrence risk of uveitis remains.
Zhang Y et al. have found that uveitis recurred in 14 eyes (18.9%) within 3 months and in ammation recurred in 34 eyes (45.9%) in the whole follow-up period [29]. Balta O et al. have determined that the incidence of postoperative recurrence of uveitis was 52.7% in 48 patients underwent cataract surgery during 4 years of follow-up [1]. Therefore, avoiding postoperative recurrence has become a great challenge in clinical practice. In this study, in addition to the phacoemulsi cation with clear-cornea incision, and intraocular lens implantation, pupil coroplasty was also performed in patients with uveitic cataract. Encouragingly, no recurrence of uveitis was found in 96.43% cases (n = 27) during the follow-up of 5-10 years. The ndings on the underlying pathological mechanism of chronic uveitis showed that the lymphocytes in patients with uveitis exhibit great resistance to apoptosis, resulting in long-term existence of autoreactive lymphocytes, and subsequently leading to the chronicity and recurrence of uveitis. In addition, the destruction of blood aqueous barrier induced by in ammation leads to severe damage of iris microcirculation through enhancing the permeability of blood vessels and weakening the barrier function. Then freely released immune cells and in ammatory mediators directly contribute to the expansion of in ammatory injury. Therefore, we speculated that the low recurrence of uveitis revealed in this study may be attributed to the removal of pathological tissues to some degrees. Furthermore, the only patient with recurrent uveitis attributed to immunosuppression induced by the onset of ankylosing spondylitis. Our results indicated that pupil coroplasty may reduce the recurrent risk of uveitis due to iris in ammation. However, the in ammation induced by other immunologic disorders is still inevitable for the recurrence of uveitis.
A previous study based on equine experimental uveitis has observed the histopathological characteristics of engorgement of blood vessels, neovascularization, focal or diffuse mononuclear proliferation, exudative retinal detachment, and disorganization of retinal layers [21]. In order to discover the underlying pathological mechanism of uveitis in human, HE staining was performed to reveal the histopathological changes of uveitis-suffered iris tissues in this study. An obvious atrophy of iris stroma was observed in all cases, which is considered as a prominent feature of uveitis. The in ammation-induced immune abnormality may contribute directly to the iris atrophy in uveitis. Notably, the iris atrophy can also be observed in uveitis at a quiescent period, which is considered as one of the potential causes of recurrence. Since iris cells have an ability to bind and accumulate drugs [2], the atrophy of iris tissues may also contribute to the recurrent of uveitis via inhibiting the combination and reactivity of drugs. In this study, we also observed the hyperplasia of pigment cells in the pigment epithelium and stroma in 32.14% and 67.86% cases, respectively. This phenomenon may be explained that the local immune injury greatly in uences the normal structure of iris tissue, leading to the abnormal proliferation of pigment cells. In ammation in iris tissues was the main pathological feature for uveitis, especially for uveitis at the active stage. Uveitis is known to be initiated by the recognition of T cells to retinal or cross-reactive antigens, and recruited in ammatory cells result in the damage of speci c tissues. The inhibition of in ammation and immunosuppression has become the preferred therapeutic strategy for uveitis [26]. Here, we observed the in ltration of in ammatory cells in iris tissues in 25% cases. This phenomenon indicated that patients with a quiet uveitis also have an activated in ammation in iris. Recurrent uveitis is mediated by autoaggressive Th response, which could be induced by dysregulated immune response and T cells in ltration [21]. Therefore, the persistent in ammatory state in iris tissues may directly lead to the recurrence of uveitis after surgery in these cases. It is noteworthy that no recurrence of uveitis was revealed in these cases, except one case with ankylosing spondylitis. This phenomenon may directly attribute to the removal of pathological tissues. Surprisingly, although recurrent uveitis is characterized by a persistent in ammatory response, the in ammatory cell in ltration was not observed in the left 75% cases. It remains unclear why the in ammatory cells were disappeared somehow, and this is an urgent problem to be solved in future.

Conclusion
The atrophy of iris stroma was a prominent feature of uveitis. The hyperplasia of pigment cells and in ltration of in ammatory cells in iris could also be observed in some cases. During the follow-up of 5-10 years, there were no recurrence of uveitis was found in most cases underwent pupil coroplasty, phacoemulsi cation with clear-cornea incision, and intraocular lens implantation. Uveitis only recurred in one case along with the onset of ankylosing spondylitis after the surgery.

Declarations
Ethics Statement: This study was approved by the ethics committee of Beijing Tongren Hospital in accordance with the Declaration of Helsinki (TRECKY2012-02). Written informed consents were obtained from all cases.
Competing interests: The authors declare that they have no competing interests.
Funding: Not applicable.