Data on vitrectomy. 1  Patients with proliferative retinopathy have a 33% risk of a vitreous haemorrhage at some time. 2  About 25% of these haemorrhages are recurrent or severe and need a vitrectomy. 3  After vitrectomy about 20% bleed needing a washout.  After vitrectomy, 33% have vision better than 6/18. 3% develop rubeotic glaucoma.
The Earth's atomospheric ozone layer is located in the tropopause, which is located just. above the troposphere. The tropopause is the bottom limit of the stratosphere several. miles above the surface of the Earth.
Most ozone is found in a layer more than 10 kilometers (6 miles) above the Earth. This stratospheric ozone layer prevents the Sun's harmful, high-energy radiation from reaching Earth's surface. Ozone in the stratosphere is constantly being created and destroyed by the action of light and photochemistry.he stratospheric ozone layer has become substantially depleted throughout much of the globe since the 1980s because of enhanced human production and use of ozone-depleting chemicals, such as chlorofluorocarbons, halons, and others, during the 20th century.