The academic and economic strength of Acta is based on the quality of Nordic ophthalmology. Acta has modernized in recent years, introducing computer technology and Internet use into manuscript submission and processing, as well as electronic publishing and access. The academic quality of the journal is ever increasing, as is its international exposure. The readership of Acta consists of practically all ophthalmologists in the Nordic countries and subscribers and libraries all over the world. Online usage of Acta has been increasing rapidly, with more than 100 000 articles downloaded in 2004 (Fig. 1). Online access to Acta is utilized by ophthalmologists and eye health care researchers all over the world: in 2004, for example, more than 2400 articles were downloaded in Australia and 2200 in South Korea.

Exfoliation syndrome (XFS) is an age-related disorder common in many populations although there are also considerable ethnic and geographical differences (Ringvold 1999). XFS is characterized by the accumulation of abnormal microfibrillar deposits that line the aqueous bathed surfaces of the anterior segment of the eye; this may lead to elevated intraocular pressure (IOP) and exfoliation glaucoma (XFG), the latter being characterized by rapid progression, high resistance to medical therapy and worse prognosis than primary open-angle glaucoma (Schlotzer-Schrehardt & Naumann 2006). This condition was first reported by the Finnish ophthalmologist Lindberg in his doctoral theses in 1917, some 90 years ago. An English version was published in this journal in 1989 (Lindberg 1989). A recent study found 15-year risk of XFS conversion to XFG to be about 60% (Jeng et al. 2007).

Removal of the vitreous humour influences the physiology of the eye. The diffusion characteristics of small molecules in the vitreous cavity are changed dramatically by the removal of vitreous gel and its replacement by aqueous humour. This effect is predicted by the Stokes−Einstein equation (Sinko 2006). In vitrectomy the vitreous gel is replaced by water. As vitreous humour is 99% water, the chemical change is not terribly great, but there is an enormous change in viscosity. All liquids possess a definitive resistance to flow; viscosity is a measure of internal flow friction or the resistance of liquid molecules. The higher the magnitude of viscosity, the more resistant the liquid will be to flow. The viscosity of water is 1.00 centipoise (cp) at 20 °, whereas that of vitreous gel is 300–2000 cp (Lee et al. 1992; Soman & Banerjee 2003). The change in viscosity has a major effect on diffusion and thereby on the transport of all substances through the vitreous cavity. The amount (M) of compound flowing through a unit cross-section (S) of a flow barrier in unit time (t) is known as the flux (J):