Contact glass dynamometry is an ophthalmology (eye care) procedure for determining diastolic and systolic blood pressure in the eye. Furthermore, it is also possible to accurately determine the central venous pressure in the eye within a few seconds. With the help of this contact glass dynamometry procedure, an assessment of possible hypertension (high blood pressure) can be realized, so that, if necessary, treatment to correct the high blood pressure can be carried out following the examination. The development of the procedure, which represents a consistent further development of the Bailliart ophthalmodynamometer, can be traced back significantly to the physician Dr. Bernhard Löw.
Indications (areas of application)
- Internal carotid artery stenosis (narrowing of the brain-supplying carotid artery due to calcification, which can lead to stroke).
- Systemic hypertension (high blood pressure) with possible damage to retinal vessels.
- Central retinal vein occlusion
- Glaucoma (glaucoma – increase in intraocular pressure with accompanying deterioration of vision).
- Endocrine orbitopathy (EO; exophthalmos – protrusion of the eye due to space-occupying inflammatory processes behind the patient’s eyeball).
- Suspicion of possible underperfusion (worsened blood flow) of the brain.
- Suspicion of increased intracranial pressure with headache symptomatology and reduced performance
Contraindications
- Sicca syndrome (autoimmune disease with possible keratoconjunctivitis sicca – drying up of the tear fluid with the symptom of dry eye).
The procedure
The principle of the contact glass dynamometer is based on the application of pressure to the vessel on which the blood pressure measurement is to be made, and is therefore based on the same system as a conventional pressure measurement on the upper arm (brachial artery). The induction of this force can now be determined by measuring the opposing force and subsequently correlated with the intraocular pressure. The force induction is achieved in this procedure by using a contact glass, the Goldmann three-mirror glass (contact glass with a central portion and three mirrors at different angles for viewing the retina – retinal – and in particular the vascular system located there). The measuring equipment required for the determination is located on the back of the contact glass. After the measurement, the determined intraocular pressure is shown on an LCD display. There is a connection between the contact glass dynamometer and a computer-aided system. To the procedure of contact lens dynamometry:
- The patient to be examined is locally anesthetized with the aid of a drip anesthetic and, if necessary, treated with atropine (pupil dilating agent)
- Now takes place the already described measurement of intraocular pressure for subsequent determination of blood pressure values in the arterial retinal vessels
- The pressure exerted by the contact glass is increased until an excess of the diastolic blood pressure was realized
- After reaching and exceeding this significant value is only a pulsation (in the arterial vascular system triggered pressure wave) for example in the artery centralis retinae (diagnostically important artery of the retina) to recognize, following it comes to a collapse of the arterial vessels – a vascular collapse indicates the diastolic pressure and a pulsation is an indication (indication) for the systolic blood pressure
- By using the foot pedal, the physician can now record the blood pressure present in the vascular segment
- Furthermore, the attending physician also has the option of measuring the venous outflow pressure by using a finger to compress the upper eyelid or by using the contact glass to cause an increase in pressure – when the intraocular pressure is increased, a venous pulse can only be triggered if the outflow pressure is too high
Increasing diagnostic significance of the procedure is the determination of the central venous pressure. As a result of this possibility, it is possible to determine, among other things, the blood flow through constrictions of the venous system and the tissue-specific influences of stenosis (narrowing). In addition, new scientific research confirms the correlation of glaucoma with increased venous pressure. To date, there are no known complications associated with the use of this procedure.
Benefit
Through the development of the method, patients affected by the following disease patterns will benefit by assessing their disease progression (course of disease), so that appropriate therapy for the patient can be implemented after the examination is completed:
- Persons at risk for stroke can be offered a risk assessment (information about a possible risk of stroke).
- Indication to patients that visual disturbances may be due to low blood pressures.
The procedure itself is completely painless for the patient and can be performed without the use of medication if the pupil is sufficiently wide.
