COLOUR DOPPLER VELOCIMETRY OF CENTRAL RETINAL ARTERY IN GLAUCOMATOUS AND NORMAL SUBJECTS Dr. Harmeet Singh Waraich Dr. K.P. Chaudhary M.D. Dr. P.C. Negi D.M.(Prof. & Head , Ophthalmology) ( Prof. & Head, Cardiology) Deptt.of Ophthalmolgy I.G.M.C. SHIMLA
Glaucoma can be defined as a multifactorial optic neuropathy with a characteristic loss of optic nerve fibres presenting as :-Classical optic nerve head features.Visual field changes.May or may not be associated with elevated IOP and angle anomalies in the presence or absence of any cause for the disease. Role of IOP in the current definition is only one of the multiple factors responsible for the disease.
IOP and Glaucoma in the present contextConsidering the intraocular pressure as a primaryvariable, glaucoma can be classified as :-1) High Tension Glaucoma-POAG (IOP> 21mm of Hg )2) Normal Tension Glaucoma-NTG(IOP < 21mm of Hg )3) Ocular Hypertension-OHT
Pathogenesis of Glaucomatous optic nerve damage Two main mechanisms have been proposed1) One suggests, mechanical damage directly to the axons or small vessels by structural alterations at the lamina cribrosa. – MECHANICAL THEORY2) The other suggests, primary problem in the blood flow of the optic nerve as a result of localised organic change with or without a low perfusion pressure or vasospasm. – VASCULAR THEORY
Evidence in support of Vascular Theory.1) In NTG patients, despite the IOP <21mm of Hg , there is progressive damage of optic nerve head suggesting that vascular factors have predominant role in NTG.2) In OHT , IOP> 21 mm of Hg does not cause glaucomatous damage , which supports that IOP alone is not sufficient to cause optic nerve damage.3) NTG is associated with various vascular disorders like hypotension, migraine, Raynaud’s phenomenon which suggests that same pathophysiological mechanism is causing ONH damage.
VASCULAR COMPROMISE – NTGPatients of NTG may suffer from ocular blood flow deficits.Increased choroidal filling time.Increased vascular downstream resistance in CRA & SPCA.Increased areas of ICG hypofluorescence in peripapillary region.Diffuse cerebral ischemia.
Role of perfusion pressure & vascular resistance of retrobulbar vessels.Blood flow of optic nerve head = Perfusion pressure ResistanceBlood flow has direct relation with perfusion pressure and inverserelation with resistance of vessels.Perfusion pressure = Mean arterial pressure – IOPFall in perfusion pressure due to decreased mean arterial pressure orincreased IOP results in decreased perfusion of ONH.Increased resistance of retrobulbar vessels also decreases ONHperfusion and thus accelerates glaucomatous damage.
Measurement of ONH Perfusion Colour Doppler imaging is an ultrasound technique that combines B scan gray scale imaging of tissue structure , coloured representation of blood flow based on Doppler shifted frequencies and pulsed Doppler measurement of blood flow velocities. With the advent of colour Doppler it has become possible to visualize retrobulbar vessels and to calculate the blood flow velocities in these vessels.
COLOR DOPPLER SCAN SPCACRAOAOA (Reverse flow)
COLOUR DOPPLER VELOCIMETRY OF CENTRAL RETINAL ARTERY IN GLAUCOMATOUS AND NORMAL SUBJECTS. STUDY CONDUCTED IN THE DEPTT. OF OPHTHALMOLOGY I.G.M.C. SHIMLA AIM OF STUDY To assess the blood flow velocities ( Peak Systolic Velocity and End Diastolic Velocity ) and Resistive Index in Central Retinal Artery in patients with chronic open angle glaucoma in comparison with non-glaucomatous control population.
REVIEW OF LITERATURE In 1989, Ericson – first to describe qualitative appearance of CDI in normal orbits Quantitative estimation – done by Lieb et al (1991), Guthoff et al (1991) and Williamson et al( 1993). In 1995, Rankin et al– found positive correlation of visual field changes with retro bulbar hemodynamic parameters. In 2000, Schumann et al suggested that eyes with progressive visual field defects in pts with NTG had statistically significant lower blood flow velocities and higher resistive indices in CRA than with practically stable visual field defects.
Material & MethodsGroup I.30 patients of chronic open angle glaucoma fulfilling the selectioncriteria.Group II30 normal age and sex matched healthy volunteers.Criteria for selection of patients of Gr. I .Patients fulfilling 2 outof 3 undermentioned selection criteriaIOP consistently above 21+1 mm of Hg.Reproducible visual field defects. Glaucomatous optic disc changes.
Exclusion criteriaPatients having history of Intraocular surgeryCardiovascular diseaseSystemic hypertension or hypotensionDiabetes mellitusMigraineActive ocular infection or inflammation
Pre procedure evaluation Written informed consent was obtained after explaining the procedure. Detailed history Visual acuity IOP recording – Goldmann applanation tonometer Slit lamp Biomicroscopy – 78 D lens Gonioscopy – Goldmann 3 Mirror Goniolens PS Evaluation – Indirect ophthalmoscope Visual field analysis- Humphrey visual field analyzer
Technique of Colour Doppler Imaging of Central Retinal Artery An ATL ( Advanced Technologies Limited) HDI 3000 Colour Doppler with 7.5 MHz linear phased transducer was used for colour Doppler imaging of Central Retinal Artery. All the examinations were done with patients in supine position. To examine the Central Retinal Artery the B scan image of the optic nerve was used to localize the area of anterior optic nerve. The sample volume was placed with the centre about 3mm behind the surface of the disk.
From the spectral waveform of Central Retinal Artery, PeakSystolic Velocity (PSV) and End Diastolic Velocity ( EDV)were measured. Resistive Index was calculated using the formula PSV-EDV/ PSVResistive index is a ratio and is Doppler angle independent.
RESULTS Std. Std. Error Significance GROUP N Mean Deviation Mean (2-tailed)AGE glaucoma 60 61.92 10.496 1.344 0.131 normal 60 59.60 5.428 .701PSV glaucoma 60 9.48 3.348 .429 0.869 normal 60 9.57 2.554 .330EDV glaucoma 60 2.89 1.066 .137 0.000 normal 60 3.93 1.219 .157RI glaucoma 60 0.69 .062 .008 0.000 normal 60 0.59 .062 .008
RESULTS Std. Std. Error Significance GROUP N Mean Deviation of Mean (2-tailed)IOP glaucoma 60 18.00 7.057 .904 0.039 normal 60 16.00 2.314 .299SBP glaucoma 60 123.80 8.546 1.094 0.350 normal 60 122.67 3.909 .505DBP glaucoma 60 80.82 6.136 .786 0.312 normal 60 79.93 2.875 .371MEAN glaucoma 60 95.10 6.833 .875 0.374 normal 60 94.27 2.357 .304PP glaucoma 60 77.16 6.778 .868 0.413 normal 60 77.93 2.603 .336
NORMAL 59.6GLAUCOMA 61.92 0 20 40 60 80 100 GLAUCOMA NORMAL Series1 61.92 59.6 Series1Comparison of Age group of Normal & Glaucoma patients ( P value = 0.131)
NORMAL 16 IOP GLAUCOMA 18 15 16 17 18 19 Series1Comparison of IOP of Normal and Glaucoma patients ( P value=0.039)
NORMAL 77.93 PP GLAUCOMA 77.16 76.6 76.8 77 77.2 77.4 77.6 77.8 78 Series1Comparison of Perfusion pressure of Normal & Glaucoma patients ( P value = 0.413)
NORMAL 9.57 PSV GLAUCOMA 9.48 9.4 9.45 9.5 9.55 9.6 Series1Comparison of PSV of Normal & Glaucoma patients (P value = 0.869)
NORMAL 3.93 EDV GLAUCOMA 2.89 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Series1Comparison of EDV in Normal & Glaucoma patients ( P value =0.000)
NORMAL 0.59 RI GLAUCOMA 0.69 0.54 0.56 0.58 0.6 0.62 0.64 0.66 0.68 0.7 Series1Comparison of RI of Normal & Glaucoma patients ( P value = 0.000)
DISCUSSIONColor Doppler Imaging and spectral analysis are attractive toolsfor noninvasive vascular investigation of retrobulbar vessels.Central retinal artery can be easily identified by its position withinthe optic nerve head and its characteristic waveform.Measurements from central retinal artery are most reproducible.This study shows that there is significant decrease in mean EndDiastolic Velocity (EDV) and increase in Resistive Index (RI) inglaucoma patients as compared to normal subjects substantiatingvascular theory of glaucoma.Perfusion pressure was found to be lower in Glaucoma patients ascompared to normals but the difference was not significant.
DISCUSSIONA decrease in EDV is a sensitive indicator of downstream resistance which leads to decreased perfusion.Changes in resistance affect the diastolic flow velocity more than systolic velocity.Resistive Index represents a quantification of end organ resistance, the formula is suited to low resistance vascular beds typical of the cerebrovascular region.Resistive index can be used to assess the effectiveness of various pharmacological interventions directed at increasing the
SUMMARY AND CONCLUSIONS There is no doubt that vascular compromise plays an important role in the pathogenesis of Glaucoma especially NTG. Colour Doppler can be used in investigating cases of POAG & NTG on regular basis to assess the retrobulbar haemodynamic variables . It can prove to be a promising investigation to assess vascular compromise in these patients. We can evaluate the severity of the disease, its progression and efficacy of treatment in glaucoma patients with the help of CDI which is a wonderful investigation to assess retrobulbar haemodynamic profile.