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David B. Henson, Yanfang Wang, Ramesh Gautam, Vincent Nourrit, Ingo Schiessl, Cecilia Fenerty; Changes In Perfusion Of The Optic Nerve Head Following Medical Lowering Of Iop In Glaucoma And Glaucoma Suspects. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2840.
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To measure perfusion of the optic nerve head pre and post IOP reduction (prostaglandins) in patients undergoing first time ocular hypertensive treatment.
Thirty patients (56 eyes, mean age 65.9 years SD 9.4) started on medical hypotensive treatment (prostaglandin) for glaucoma (n=34) or suspect glaucoma (n=22) were recruited from the clinics of Manchester Royal Eye Hospital, UK. Multispectral imaging was carried out pre and 1 week post the onset of treatment with a modified digital fundus camera system incorporating a 250W tungsten halogen lamp and fast-tuneable liquid crystal filter (Varispec, Cambridge Research Systems, UK). Eight images were captured sequentially over ~1.5s at wavelengths selected according to absorption properties of blood components (range 496-700nm), and a Beer-Lambert law model was used to produce perfusion maps of the optic nerve head from the aligned images. Pre and post treatment perfusion maps for each eye were intensity and contrast matched prior to being classified by 5 experts (pre/post treatment randomised left/right) as showing greater perfusion ‘definitely left’, ‘maybe left’, ‘no difference’, ‘maybe right’, ‘definitely right’.
The average IOP reduction was 6.7mmHg, range 2-12mmHg. There was poor to good agreement between the experts Kappa (linear weighted) 0.173-0.644. The mean classification of 5 experts showed an increase in perfusion in 30 eyes, no difference in 5 eyes and a reduction in 21 eyes. There was no significant increase in mean classification of perfusion post IOP reduction (t-test, p=0.34). Figure gives an example of perfusion maps pre and post an IOP reduction of 10mmHg. Three experts classified these images as showing ‘no difference’ while the remaining 2 classified as ‘maybe right’.
Multispectral imaging was unable to show a significant increase in perfusion of the optic nerve head with medical reduction of IOP.
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