Experimental and Clinical Investigations Into the Resistance to Outflow of Aqueous Humour in Normal Subjects

THE agreement between data on the resistance to the outflow of the aqueous humour obtained by compression of the eyeball in vivo and those obtained by perfusion of freshly enucleated eyes shows that tonography yields approx- imately accurate results.The normal resistance to outflow in man varies fiom 2'9 to 7 3 mm.Hg, the average being 4 5 (Prijot and Weekers, 1952).Our most recent deter- minations yielded analogous results (minimum 2 1, maximum 6 9, average 4 0; see below).These figures are in agreement with those given by Grant and Trotter (1955), who established an average coefficient of facility of out- flow of 0 233 for normal subjects, i.e. an average resistance of 4 29. .On the other hand, using perfusion of freshly enucleated human eyes, Grant and Trotter (1955) found an average facility of outflow of 0'27, i.e. a resistance of 3*7.Frangois, Rabaey, and Neetens (1955) obtained the following values: Resistance Number of Eyes Maximum Average Minimum 61 2 4 8.3The aim of the plesent investigations is to study certain factors which influence the resistance to outflow of aqueous humour in normal subjects.Technique Resistance to outflow was determined in vivo by tonography.Calculations were made with the aid of the most recent tables on ocular tension (1954) and on tonometric pressure