A model of chronic hypotony in the rabbit

• Background: Chronic hypotony is an important cause of functional failure after proliferative vitreoretinopathy (PVR) surgery even if the retina is successfully reattached. The purpose of this study was to create a relevant model of chronic hypotony in the rabbit. • Methods: Eighteen pigmented rabbits weighing 3–4 kg were used in our experiment. We performed pars plana lensectomy on 14 eyes of 14 rabbits with a fragmatome and a vitreous cutter. At the end of surgery, we injected 0.2 ml of phosphatebuffered saline containing 100000 cultured rabbit dermal fibroblasts over the epiciliary area. As a control, we performed pars plana lensectomy alone on four eyes of four rabbits. The intraocular pressure (IOP) was measured on days 7, 14, 21, 28. Two rabbits were killed on day 7 and prepared for histology. Two additional rabbits were killed on day 14, and the remaining ten rabbits were killed on day 28. • Results: All 14 eyes following lensectomy and fibroblast injection had an IOP less than 5 mm Hg on each follow-up and a mean of 2.5±0.6 mm Hg (mean±SD) on day 28. Four control eyes with lensectomy alone had an IOP of 7.5±2.1 mm Hg on day 28 (P<0.05). On gross examination, we identified a variety of pathologic changes, including the development of a fibrous translucent epiciliary membrane that caused distortion of ciliary processes, iridociliary adhesion and anterior displacement of the peripheral retina on day 28. Microscopic examination of eyes obtained on day 28 showed changes in the ciliary epithelium that included absence or atrophy of the non-pigmented ciliary epithelium, atrophy and cystic vacuolization of the pigmented ciliary epithelium, and interstitital edema of the ciliary body stroma. • Conclusion: We have created a model of chronic hypotony with epiciliary membrane using cultured fibroblasts in the rabbit. This model may be useful to help elucidate the pathophysiology of chronic hypotony and to investigate potential treatments.     

实验性低眼压动物模型

低眼压模型建立的方法有破坏睫状体、睫状体分离或睫状体脉络膜脱离、建立瘘道、诱导炎症反应、建立增生性玻璃体视网膜病变模型等，均可以不同程度地降低眼压。但有各自的缺点，仍需要进一步研究。建立理想的低眼压动物模型，可为研究其病理生理改变，临床治疗和预防提供实验依据。综述实验性低眼压动物模型建立的方法及降眼压的效果。     

急性低眼压白化兔荧光素虹膜血管造影的研究

目的观察白化兔急性低眼压荧光素虹膜血管造影(IFA)特点,探讨白化兔清醒状态行IFA的可行性。设计实验性研究。研究对象新西兰兔12只(12眼)。方法穿刺抽吸玻璃体制作急性低眼压兔眼模型,随机分为4组,即低眼压0h、2h、4h、8h组(每组各3只3眼),分别在造模前及各自低眼压时间点行裂隙灯、眼前节照相及IFA,之后再从中随机选3只(3眼)作为低眼压1~4d组于低眼压1、2、4d行以上检查。兔捆绑固定后用眼杯撑开受试眼睑裂,耳缘静脉注射荧光素钠注射液行IFA。主要指标虹膜及房水中荧光素渗漏程度及时间。结果兔急性低眼压造成虹膜基质和前房内大量荧光素渗漏,0h渗漏最重,2h渗漏开始减轻,8h以后除虹膜血管网略多外,其余基本接近正常。捆绑固定配合眼杯可使清醒状态兔顺利完成IFA。结论兔IFA证实,急性低眼压会造成血-房水屏障破坏,低眼压早期破坏程度最重,破坏程度随低眼压持续时间延长而逐渐减轻。     

Ultrasound biomicroscopy of chronic hypotony after cataract extraction

Ultrasound biomicroscopy was performed with a UBM 840 (Zeiss-Humphrey) equipped with a 50 MHz probe on a patient with chronic hypotony 1 year after cataract surgery by phacoemulsification with intraocular lens implantation in the capsular bag. This sonographic technique, which provides high-resolution imaging of the anterior segment, showed aqueous humor leakage through the former scleral tunnel incision. Ultrasound biomicroscopy helped detect this patient's postoperative complication and is a good tool for diagnostic procedures in patients with chronic hypotony.     

Ibopamine treatment in chronic hypotony secondary to long-lasting uveitis. A case report

PURPOSE: To assess the clinical efficacy of ibopamine eye drops in severe hypotony secondary to chronic progressive uveitis. METHODS: Case report. A 47-year-old man with a 37-year history of diffuse uveitis and severe refractory hypotony was treated with topical 2% ibopamine (Trazyl) six times a day. Intraocular pressure, visual acuity, visual field and side effects were recorded during 15 months of follow-up. RESULTS: IOP, visual acuity and visual field increased after four days of therapy and lasted for two months when the drug was suspended because of the onset of filamentous keratopathy. A new course of treatment with 2% ibopamine eye drops in a different solvent (BSS) resulted in a stable increase in IOP, VA and visual field, with no side effects in a follow-up of 13 months. CONCLUSIONS: Ibopamine 2% eye drops in BSS solvent seem effective in the treatment of uveitis-related hypotony.     

兔慢性泪囊炎动物模型建立的方法学研究

背景 慢性泪囊炎是一种常见的泪器感染性疾病,易复发,导致患者预后较差.目前关于在病变复发过程中究竟是感染因素还是泪道阻塞因素发挥主要作用仍存在争议,建立合理的动物模型有助于其发病机制的研究,但目前鲜见慢性泪囊炎的建立方法研究. 目的 探索建立兔慢性泪囊炎动物模型的方法,为慢性泪囊炎的临床诊疗研究提供实验依据.方法 采用随机数字表法将66只日本大耳白兔随机分为6个组,每组11只,均以右眼作为实验眼.暂时泪道阻塞组采用质量分数10％甲苯-2.4-二异氰酸酯(TDI)联合榄橄油溶液右鼻腔滴鼻诱导过敏性鼻炎造成暂时性泪道阻塞;永久泪道阻塞组由泪点注入0.15 ml甲基丙烯酸甲酯(MMA)和聚甲基丙烯酸甲酯(PMMA)聚合物;单纯细菌接种组由泪点注入1×107/ml金黄色葡萄球菌悬液0.3 ml;暂时泪道阻塞+细菌组和永久泪道阻塞+细菌组分别在造成暂时性泪道阻塞和永久性泪道阻塞后次日由泪点注入1×107/ml金黄色葡萄球菌悬液0.3 ml;正常对照组由兔泪点注入0.3 ml生理盐水.分别于术前、术后即刻及术后1d、7d观察动物出现慢性泪囊炎的眼部表现情况以判断造模成功率,行泪道冲洗观察泪道是否通畅,并行泪道CT造影检查是否发生泪道阻塞、阻塞部位以及阻塞程度;术后7d行泪道和泪囊黏膜的常规组织病理学检查. 结果 造模后3个月,暂时泪道阻塞组、单纯细菌接种组、暂时泪道阻塞+细菌组和正常对照组无一例出现慢性泪囊炎表现,永久泪道阻塞组和永久泪道阻塞+细菌组分别有8只眼和9只眼出现慢性泪囊炎的症状和体征.泪道冲洗结果提示,永久泪道阻塞组和永久泪道阻塞+细菌组的慢性泪囊炎眼泪道冲洗不通畅,液体完全返流;泪道CT造影检查显示,兔鼻泪管阻塞部位为鼻泪管的远端,即鼻泪管骨内段与鼻内段的转折部位,并可见鼻泪管完全阻塞,阻塞处近端可见明显的鼻泪管扩张,阻塞处远端无明显的造影剂充盈;永久泪道阻塞组模型眼标本可检出革兰阴性杆菌,永久泪道阻塞+细菌组模型眼金黄色葡萄球菌为优势菌.暂时泪道阻塞组、单纯细菌组、暂时泪道阻塞+细菌组和正常对照组兔眼泪囊和泪道黏膜病理组织学检查未发现异常,而永久泪道阻塞组和永久泪道阻塞+细菌组模型眼标本可见炎性细胞浸润和增生性改变.结论 泪道永久性阻塞是兔慢性泪囊炎动物模型建立的必要条件,在兔慢性泪囊炎的发生中起关键作用.     

The surgical management of chronic hypotony due to uveitis

PURPOSE: Evaluate surgery in chronic hypotony secondary to uveitis. METHOD: Retrospective analysis of six patients operated for chronic hypotony (< or =5 mmHg) of at least 1 month's duration. Surgery involved removal of all traction and membranes on the ciliary processes. Use of oil was limited to patients with atrophic ciliary processes. RESULTS: The average postoperative follow-up was 24 months (12-43). The average pressure increase was 7 mmHg at 6 months. Four of six uveitis patients had significantly increased vision. CONCLUSION: Improved vision, and a sustained pressure rise are possible in hypotonous uveitis. The presence of ciliary processes is necessary. However, they do not need to be intact.     

Laser trabecular sclerosis for chronic hypotony after vitreoretinal surgery

PURPOSE: To perform a pilot study of laser trabecular sclerosis (LTS) for chronic ocular hypotony after vitreoretinal surgery. DESIGN: Prospective noncomparative case series. PARTICIPANTS: Three patients with chronic hypotony after vitreoretinal procedures underwent LTS. All patients had undergone complex vitreoretinal surgery with attached retinas postoperatively but with persistent hypotony and poor vision. INTERVENTION: Laser trabecular sclerosis was performed in a fashion similar to laser trabeculoplasty, using a 100-microm spot, 800 to 1000 mW power at 0.1 seconds, and applying heavy confluent treatment in >/=1 sessions throughout the angle where trabecular meshwork was visible. MAIN OUTCOME MEASURES: Intraocular pressure (IOP), best spectacle-corrected visual acuity, and complications were studied. RESULTS: In 1 patient, a single session of LTS was followed by an increase in IOP of approximately 4 mm, with subjective and objective improvement in vision. A second patient exhibited improvement in IOP and visual acuity after 3 sessions of LTS. A third patient underwent 3 sessions of LTS without improvement in IOP or vision. CONCLUSION: Given the limitations of this small series, including the lack of a randomized prospective design, it is not possible to determine the safety or efficacy of LTS, but this study does suggest that this procedure could play a therapeutic role in some patients with chronic symptomatic hypotony after complex intraocular surgery. Further study is warranted.     

前部增生性玻璃体视网膜病变引起慢性低眼压发病机制的探讨

目的探讨前部增生性玻璃体视网膜病变(anterior proliferati ve vitreoretinopathy,aPVR)病理状态下低眼压的发生、发展及转归,为防治aPVR引起的慢性低眼压提供理论依据。方法利用培养的同种兔皮肤成纤维 细胞制作aPVR引起慢性低眼压的动物模型,于术前及术后不同时间点分别观测眼压(intrao cular pressure,IOP),行超声生物显微镜(ultrasound biomicroscopy,UBM)检查,并做病理、电镜观察。结果术后1周、2周、4周、8周实验组平均 眼压明显低于对照组(P<0．01)。UBM显示术后4周实验组虹膜后睫状体内侧条形回声,术后4周及8周实验组周边视网膜牵引性脱离。光镜检查发现实验组4 周及8周睫状体无色素上皮萎缩、缺失。电镜检查发现实验组术后4周和8周睫状体无色素上皮线粒体明显减少,细胞内空泡。结论在aPVR病理状态下,睫状膜的增生和收缩引起对睫状上皮的牵拉,造成睫状体无色素上皮萎缩,可能是引起慢性低眼压的主要原因。(中华眼底病杂志,2001,17:216-220)     

严重眼外伤Ⅰ期术后低眼压的处理及预后

目的探讨危重眼外伤Ⅰ期术中或术后应用全氟丙烷(C3F8)气体对眼压及其预后的影响。方法危重眼外伤26例(26眼)Ⅰ期术中或术后注入纯全氟丙烷气体,观察眼压并于Ⅱ期术中观察气体作用效果及预后评价。结果注气术后眼压得到改善23眼,18眼角膜水肿浑浊经气体充填后恢复透明15眼,Ⅱ期术中在气体作用下视网膜平复状态共21眼。术后随诊3~12月,视力提高22眼,视力不变3眼,视力下降1眼。结论危重眼外伤Ⅰ期术中或术后应用全氟丙烷气体能有效提升眼压同时取得较好预后。     

Ocular hypotony: A comprehensive review

Ocular hypotony is an infrequent, yet potentially vision-threatening, entity. The list of differential causes is extensive, involving any condition that may compromise aqueous humor dynamics or the integrity of the globe and sometimes following medical treatments or procedures. Depending on the cause and the clinical impact, treatment options aim to correct the underlying pathology and to reestablish anatomical integrity, as well as visual function. We review the pathophysiology, clinical presentation, different causes, and associated therapeutic options of ocular hypotony.     

Ultrasound biomicroscopy in chronic ocular hypotony: its impact on diagnosis and management

PURPOSE: To determine the value of ultrasound biomicroscopy (UBM) in the assessment of ocular hypotony in cases where the underlying pathologic mechanism remains unclear after extensive clinical examination. METHODS: In a retrospective study, the records of 60 patients who had undergone UBM to elucidate the underlying structural abnormalities of chronic ocular hypotony (intraocular pressure of 0-8 mmHg) were evaluated. Most patients (47 of 60 eyes) had a history of intraocular surgery or of other ocular diseases (e.g., uveitis), and after careful clinical examination, the cause had remained unclear. All patients were observed up for a minimum of 12 months. RESULTS: The associated pathoanatomy of the hypotony was demonstrated by UBM in 95% of the cases. Ciliary body abnormalities were present in 80% of the eyes. Therapeutic intervention was associated with restoration of normal ocular pressure in 50% of the cases. Often more than one intervention was necessary. A long duration of hypotony did not impede reaching the therapeutic goal of normalizing intraocular pressure and preventing phthisis. CONCLUSIONS: Ultrasound biomicroscopy is a new tool for detecting the underlying structural abnormalities in ocular hypotony. In cases where clinical examination is not sufficient it can be of great help in deciding on a course of treatment.     

Anterior scleral buckling procedure for cyclodialysis cleft with chronic hypotony.

Cyclodialysis clefts occur when the attachment of the ciliary body to the scleral spur is disrupted. The mechanism is usually traumatic or iatrogenic after phacoemulsification or other intraocular manipulation. Treatment becomes necessary when hypotony occurs, with maculopathy being the most visually significant sequela. A patient who failed conventional treatment for hypotony and eventually benefited from a novel surgery to correct his cyclodialysis cleft is described.     

A new model of experimental subretinal neovascularization in the rabbit

Existing animal models of choroidal neovascularization (CNV) present several problems: they are hard to reproduce, they are inefficient, and the CNV created is not sustainable. The purpose of this study is to develop a highly efficient, reliable, sustainable rabbit model of CNV to facilitate the study of anti-angiogenic and anti-proliferative therapies for ocular diseases. Twenty-two pigmented rabbits were used in this study. Eleven rabbits received subretinal injections of either 10 microl of Matrigel with 500 ng of vascular endothelial growth factor (VEGF) or 20 microl of Matrigel with 750 ng of VEGF; eight rabbits received subretinal injections of either 10 or 20 microl of Matrigel only; three rabbits used as controls received subretinal injections of 20 microl phosphate-buffered saline (PBS) alone. Fundus photography, fluorescein angiography, optical coherence tomography, and histologic examinations were performed 1, 2, 4, and 9 weeks after injection. All experimental eyes showed angiographic leakage within this localized area 1 week after injection. The amount of leakage usually increased at weeks 2 and 4 and, in most cases, persisted at week 9. Control eyes demonstrated no leakage at any time point. Optical coherence tomography of treated eyes showed subretinal fluid and the presence of a lesion, possibly vascular or fibrotic, at the site of the leakage. Histologic analysis confirmed the presence of new subretinal blood vessels in the areas of Matrigel deposit. In conclusion, this novel method provides a highly reproducible, reliable, and sustainable rabbit model of experimental choroidal neovascularization. Such a model may prove useful for screening new anti-angiogenic therapies in a larger animal eye.     

A simple treatment for chronic postoperative hypotony of unknown etiology: the injection of balanced salt solution into the anterior chamber

Postoperative hypotony is not rare. When it occurs, effective treatment must be initiated to avoid secondary complications. We report two cases of postoperative hypotony that have been treated successfully with a single injection of balanced salt solution (BSS) into the anterior chamber. One patient developed hypotony three months after combined cataract surgery and trabeculectomy with the use of Mitomycin C (MMC). The cause of hypotony remained unknown. Leakage, hyperfiltration, cyclodialysis, and other possible causes had been excluded. With a single injection of BSS into the anterior chamber the long-standing hypotony was successfully managed. A second patient with hypotony after pars plana vitrectomy was also treated successfully with an injection of BSS into the anterior chamber. We conclude that an injection of BSS into the anterior chamber is an inexpensive and efficacious remedy for postoperative hypotony of unknown etiology.     

Winning the battle of refractory hypotony

Background:Trabeculectomy, a mainstay in the management of glaucoma is associated with various complications, the most dreaded being hypotony.Purpose :We present a challenging case of late-onset refractory hypotony following trabeculectomy.Synopsis:A 64-year-old male patient diagnosed with primary open angle glaucoma in the right eye underwent combined surgery. Three weeks later, he presented with hypotony which responded well with medical management and then he was lost to follow-up. Two years later, he presented with severe hypotony with shallow choroidal detachment in the right eye, which failed to respond to medical management. Compression sutures were placed over the bleb which also failed to work. Subsequently bleb repair was done with corneal patch graft, which helped resolve the bleb leak, with an improvement in visual acuity and intraocular pressure.Highlights:This video highlights the importance of prompt and timely intervention of an overfiltering bleb in preventing irreversible visual loss.Video link: https://youtu.be/8DrxzqQ4qP4