The
ocular perfusion pressure (PP) as the difference between pressure in retinal
artery (PAR) and the ocular pressure (IOP) is an important factor of sufficient
oxygen supply of retinal tissue. Constant or intermittent reduction of PP
either by elevation of IOP or by decreasing of PAR may be the essential cause
of glaucoma. A decisive cause of elevation of IOP may be decreasing facility of
outflow (FO). Measuring IOP is an ophthalmologic standard procedure, but
assessments of PAR and FO are more complicated methods. Early diagnosis of
glaucoma may be improved by easy and simultaneous assessments of PAR, IOP and
FO. We developed a new instrument which allows tonometry, tonography and
ophthalmodynamometry. The instrument is based on the principle of applanation
tonometry. An electric motor moves an applanation body against the eye, the
cornea is applanated and thus IOP is successively elevated. A sensor in the
centre of the applanation area registers continuously the actual IOP. A second
forced sensor positioned between the motor and the applanation body registers
the force necessary to produce a given applanation area. The quotient
force/actual IOP allows to assess the applanation area. The actual values of
force and pressure are evaluated to drive or stop the motor.