terminology and guidelines for glaucoma ii - Kwaliteitskoepel

1.5 - BLOOD FLOW
1.5.1 - VASCULAR FACTORS AND GLAUCOMA
Factors involved in the aetiology and progression of glaucomatous optic neuropathy are not only pressure dependent
and are also related to the vascular supply of the optic nerve head.
Many observations indicate the need to study the relationship between blood flow and glaucoma:
- existence of normal tension glaucoma (NTG) 1-4
- presence of disc haemorrhages in glaucoma patients
- higher prevalence of retinal vein occlusion in glaucoma patients
- association of NTG and migraine, Raynaud’s phenomenon, vasospasm 5,6,7
- association of NTG and systemic hypotension and excessive number of nocturnal “dips” in diastolic blood pressure 8,9
- association of glaucoma and abnormal blood coagulability profile 10,11
- association of NTG and silent myocadial ischaemia 9
- association of glaucoma (NTG) and cerebral infarcts 12,16
- association of NTG and an history of hypotensive shock or episode of severe blood loss. 5
1.5.2 - MEASUREMENTS METHODS OF OCULAR BLOOD FLOW
Many methods have been used to calculate ocular blood flow: fluorescein angiography 14,15 , scanning laser ophthalmoscope
16 , videoangiography 17,18 , laser Doppler velocimetry 19,20 , laser speckle phenomenon, blue field entoptic phenomenon
21 , pulsatile ocular blood flow 22 , colour Doppler imaging 23,24 , oculodynamography 25-27 . For technical reasons, wide
interindividual variations can occur with problems related to posture, as well as technician experience, patient cooperation.
Multiple measurements are therefore required. More importantly in glaucoma, it is relevant to measure the
blood supply to the retrolaminar portion of the optic nerve head, i.e. small vessels which are difficult to visualise and
have wide anatomic variability.
The number of methods used illustrate the difficulty of measurements of ocular blood flow relative to the blood supply
of the optic nerve head, size of of vessels, individual variations, reproducibility of measurements techniques.
At the present time the clinical role of blood flow measurements in glaucoma management (and the relevance of changes
noted with drug treatments) are unclear and these techniques remain research tools.
However clinical vascular risk factors should be taken into account in glaucoma management especially when the
IOP is low (over 24 hours and with normal CCT) and visual fields show severe and progressive alteration 28 .
1.6 - AXIAL LENGTH MEASUREMENTS
For follow-up of congenital glaucoma axial length measurement is a useful tool, especially to correlate with IOP findings,
refraction and corneal diameter 29,30 .
Ch. 1 - 33 EGS