Vitreous substitutes: challenges and directions

The natural vitreous body has a fine structure and complex functions. The imitation of the natural vitreous body by vitreous substitutes is a challenging work for both researchers and ophthalmologists. Gases, silicone oil, heavy silicone oil and hydrogels, particularly the former two vitreous substitutes are clinically widely used with certain complications. Those, however, are not real artificial vitreous due to lack of structure and function like the natural vitreous body. This article reviews the situations, challenges, and future directions in the development of vitreous substitutes, particularly the experimental and clinical use of a new artificial foldable capsular vitreous body.

Study of retinal vessel oxygen saturation in ischemic and non-ischemic branch retinal vein occlusion

AIM：To explore how oxygen saturation in retinal blood vessels is altered in ischemic and non-ischemic branch retinal vein occlusion（BRVO）.·METHODS：Fifty BRVO eyes were divided into ischemic（=26）and non-ischemic（=24）groups,based on fundus fluorescein angiography.Healthy individuals（=52 and=48,respectively）were also recruited as controls for the two groups.The mean oxygen saturations of the occluded vessels and central vessels were measured by oximetry in the BRVO and control groups.·R ESULTS：In the ischemic BRVO group,the occluded arterioles oxygen saturation（Sa O2-A,106.0%±14.3%）,instead of the occluded venule oxygen saturation（Sa O2-V,60.8%±9.4%）,showed increases when compared with those in the same quadrant vessels（Sa O2-A,86.1%±16.5%）in the contralateral eyes（〈0.05）.The oxygen saturations of the central vessels showed similar trends with those of the occluded vessels.In the non-ischemic BRVO group,the occluded and central Sa O2-V and Sa O2-A showed no significant changes.In both the ischemic and non-ischemic BRVOs,the central Sa O2-A was significantly increased when compared to healthy individuals.·CONCLUSION：Obvious changes in the occluded and central Sa O2-A were found in the ischemic BRVO group,indicating that disorders of oxygen metabolism in the arterioles may participate in the pathogenesis of ischemic BRVO.

Intravitreal anti-VEGF agents, oral glucocorticoids, and laser photocoagulation combination therapy for macular edema secondary to retinal vein occlusion: preliminary report

AIM： To evaluate the efficacy and safety of combined anti-vascular endothelial growth factor （VEGF） agents, oral glucocorticoid, and laser photocoagulation therapy for macular edema （ME） secondary to retinal vein occlusion （RVO）. METHODS： This study included 16 eyes of 16 patients with RVO-associated ME. Patients were initially treated with oral prednisone and an intravitreal anti-VEGF agent. Two weeks later, patients underwent standard laser photocoagulation. Best-corrected visual acuity （BCVA）, central retinal thickness （CRT）, and retinal vessel oxygenation were examined over 12mo. RESULTS： Patients received 1.43＋0.81 anti-VEGF injections. Mean baseline and 12-month IogMAR BCVA were 0.96±0.51 （20/178） and 0.31±0.88 （20/40）, respectively, in eyes with central retinal vein occlusion （CRVO） （P〈0.00）, and 1.02±0.45 （201209） and 0.60±0.49 （20/80）, respectively, in eyes with branch retinal vein occlusion （BRVO） （P〈0.00）. At 12mo, CRT had significantly decreased in eyes with CRVO （P〈0.00） and BRVO （P〈0.00）. Venous oxygen saturation had significantly increased in eyes with CRVO （P〈0.00） and BRVO （P〈0.00）. No examined parameters were significantly different between the 2 RVO groups. No serious adverse effects occurred. CONCLUSION： Anti-VEGF, glucocorticoid, and photocoagulation combination therapy improves visual outcome, prolongs therapeutic effect, and reduces the number of intravitreal injections in eyes with RVO- associated ME.

Vitreous function and intervention of it with vitrectomy and other modalities

The vitreous body,the largest intraocular component,plays a key role in eye development,refraction,cell barrier function,oxygen metabolism and the pathogenesis of assorted diseases.Age,refraction and systemic diseases can cause vitreous metabolic abnormalities.With the continuous development of vitrectomy techniques and equipment,vitreous injections and vitrectomies have increased over the recent decades.However,the normal oxygen tension gradient in the vitreous helps to protect the lens and anterior chamber angle from oxidative stress damage,whereas the increased vitreous oxygen tension around lens and the trabecular meshwork after vitrectomy may lead to postoperative nuclear cataract and a high incidence of open angle glaucoma.As a conventional procedure,scleral buckling holds several advantages over vitrectomy in selected cases.This review raises concerns regarding the function of the vitreous,and encourages conducting vitreous interventions prudently.

Vitreous function and intervention of it with vitrectomy and other modalities

The vitreous body, the largest intraocular component, plays a key role in eye development, refraction, cell barrier function, oxygen metabolism and the pathogenesis of assorted diseases. Age, refraction and systemic diseases can cause vitreous metabolic abnormalities. With the continuous development of vitrectomy techniques and equipment, vitreous injections and vitrectomies have increased over the recent decades. However, the normal oxygen tension gradient in the vitreous helps to protect the lens and anterior chamber angle from oxidative stress damage, whereas the increased vitreous oxygen tension around lens and the trabecular meshwork after vitrectomy. It may lead to postoperative nuclear cataract and increase the risk for glaucoma. As a conventional procedure, scleral buckling holds several advantages over vitrectomy in selected cases. This review raises concerns regarding the function of the vitreous and encourages conducting vitreous interventions prudently if it is possible.