Pathophysiologie der Katarakt-Entwicklung nach Vitrektomie

Abstract

Cataract formation is one of the most common complications after vitrectomy and cataract extraction in such cases will have to be performed under more difficult conditions. A knowledge of the different types of cataract, their frequency and causes may help to develop strategies to prevent this complication. In addition to a progressive nuclear opacification, which may occur after any type of vitrectomy, transient feathering of the lens often occurs after intraocular gas tamponade, while permanent subcapsular opacification may occur in silicone oil-filled eyes. Nuclear opacification after vitrectomy morphologically and histologically resembles age-related cataracts, but shows a faster progression: two years after vitrectomy half of the eyes require cataract extraction and there seems to be an age limit: the opacification progresses faster in patients over 50 years old. The main cause for nuclear cataracts most probably is oxidative stress. Oxygen in the avascular lens is provided by diffusion, meaning that the surrounding oxygen content is crucial for the oxygen content within the lens and thus for the formation of reactive oxygen species. In rabbits and also in humans the partial oxygen pressure is highly elevated in the vitreous cavity after vitrectomy and posterior to the lens since the vitreous is lacking as a diffusion barrier for the oxygen. The partial oxygen pressure might be additionally elevated by ventilation with oxygen and a high oxygen pressure in the infusion fluid during surgery. This elevated partial oxygen pressure may lead to increased oxygen stress and thus to lens opacification by oxidation of structural proteins. The key for the prevention of cataract formation therefore seems to be avoidance of oxidative stress, factors that might increase the protective or repair systems are so far not available. Ventilation with oxygen should be minimised as should be the partial oxygen tension in the infusion fluid. New hydrogels as vitreous substitutes might have a beneficial influence on intraocular partial oxygen tension.

Air as Tamponade for Retinal Detachments

“…An additional factor is age. Both patients were older than 50 years, an age at which a significantly enhanced rate of cataract progression can be expected following vitrectomy (18,19). From a technical standpoint, the retina was reattached in both patients, suggesting that this technique is also possible in phakic patients, possibly in those of young age where the risk of developing a cataract is significantly smaller.…”

Apoptosis Factors of Lens Epithelial Cells Responsible for Cataractogenesis in Vitrectomized Eyes with Silicone Oil Tamponade

“…Vitrectomy surgery can markedly increase intraocular oxygen tension for prolonged periods after surgery, and this exposes the crystalline lens to abnormally high oxygen [ 22 ]. Studies have found that the oxidation of lens protein during vitrectomy was one of the reasons for nuclear cataract after vitrectomy [ 23 ], whereas adding antioxidants into the perfusion fluid during vitrectomy could inhibit the abnormal lens epithelial cell growth and lens fiber formation and thus prevent the cataractogenesis [ 24 ].…”

Netzhautablösung – Teil 2

“…Die Revision besteht in einem Wiederablösen der Netzhaut durch subretinale BSS oder Luftinjektion mittels 41-G-Kanüle [34,35] [36].…”