| Abstract|| |
Objective(s): To evaluate the effect of optic nerve circulation, using color Doppler imaging (CDI) on progression of visual field damage in primary open angle glaucoma and chronic angle closure glaucoma.
Material and Methods (s): The study included randomly selected 25 patients with established primary open angle glaucoma, 15 patients with chronic angle closure glaucoma, who underwent medical treatment/had undergone laser or surgical procedure for glaucoma and 15 healthy volunteers of same age group were taken as control group. Color Doppler imaging of ophthalmic artery (OA), central retinal artery (CRA) and posterior ciliary artery (PCA) were conducted and various variables recorded to determine ocular blood flow in glaucomatous patients.
Result(s): Patients with stable visual field had higher diastolic velocity and lower resistivity index (RI) in all three ocular vessels (P<.001), compared with those with deteriorating visual field. Significant correlation was found between severity of glaucomatous visual field defects and degree of impairment of retrobulbar haemodynamics.
Conclusion(s): Color Doppler imaging variables of OA, CRA and PCA correlate with risk of visual field deterioration in glaucomatous patients suggesting major role of vascular factor in pathogenesis of glaucomatous optic neuropathy.
Keywords: color doppler imaging (CDI), primary open angle glaucoma (POAG), chronic angle closure glaucoma (CACG), resistivity index (RI), peak systolic velocity (PSV), end diastolic velocity (EDV), intraocular pressure (IOP), flow velocity waveform (FVW), ophthalmic artery (OA), central retinal artery (CRA), posterior cillary artery (PCA).
|How to cite this article:|
Sharma N C, Bangiya D. Comparative study of ocular blood flow parameters by color doppler imaging in healthy and glaucomatous eye. Indian J Radiol Imaging 2006;16:679-82
|How to cite this URL:|
Sharma N C, Bangiya D. Comparative study of ocular blood flow parameters by color doppler imaging in healthy and glaucomatous eye. Indian J Radiol Imaging [serial online] 2006 [cited 2020 May 28];16:679-82. Available from: http://www.ijri.org/text.asp?2006/16/4/679/32298
| Introduction|| |
Glaucoma is defined as group of disorders that have common characteristics of degeneration of optic nerve associated with typical visual field defects and usually associated with elevation of IOP. In glaucoma patients, several risk factor associated with progression of visual field loss have been suggested, most frequently reported are initial IOP, initial visual field defects, sex, race, high peripapillary atrophy-disc ratio, high cup disc ratio, disc hemorrhages, myopia, nocturnal hypotension and diabetes mellitus. Growing evidence from various studies indicate that vascular factors play a major role in the pathogenesis of glaucomatous optic nerve disease. Color Doppler imaging has been widely used in glaucoma to study pathogenetic aspects of disease and vascular effects of its treatment. In both POAG and CACG group, several abnormalities of blood flow in OA, CRA and short PCA were reported. In patient who underwent surgery to lower IOP, significant increase in end diastolic velocity and decrease in resistivity index were observed in short PCA and CRA. Color Doppler imaging found to show circulatory alteration early in the disease, might be used in future to know if given treatment could normalize circulatory alterations and on the basis of this, to predict chances of having further increase in damage to optic nerve and treatment modalities might be changed in future with emphasis directed more on normalization of circulatory alteration rather than just IOP.
| Subject and Methods|| |
Subjects: Study included randomly selected 25 patients with established POAG, 15 patients with CACG, who underwent medical treatment / had under gone laser or surgical procedure for glaucoma and 15 healthy volunteers of same age group were taken as control group.
Exclusion criteria for control group :- Patients with cardiovascular disease, DM, systemic hypertension or hypotension, migraine or vascular disease were not included in this study. Smokers, patients on systemic medication affecting blood flow, high myopic persons, patients with media opacities, were not included in study.
Equipment(s): Color Doppler imaging variables of all three vessels in POAG and CACG group were obtained by using TOSHIBA NEMIO '30' with 12 MHz linear array electronic probe.
Study protocol:- During examination, patients were adviced to assume supine position and ultrasound probe was applied gently over superotemporal part of closed eye lids using sterile methyl cellulose as coupling gel and points towards orbital apex by tilting it approximately 20-30º to saggital plane. The same transducer was applied on ipsilateral common carotid artery and blood flow velocity seen to rule out any carotid artery disease. Only those patients with normal carotid waveform were taken in the study. The doppler variables (PSV, EDV, RI) for OA, CRA and short PCA were measured and mean, standard deviation were calculated. P value calculated to determine statistical significance of these vessels in glaucoma and normal subject.
| Result|| |
Visual field changes in glaucoma patients were divided arbitrarily into mild, moderate and severe group. POAG patients have negative correlation of field changes with blood flow velocity, it was statistically significant for PSV & EDV doppler variables (severity of visual field deterioration increase blood flow velocities decreases), there was positive correlation of visual field deterioration with RI (increase deterioration of visual field increase in RI) (Table 1, 2, 3). Our result are in accordance with study of Cellini et al (1996-97), who found PSV decrease and RI to be increased significantly in patients with greater visual field damage. Similar results also reported by Renklin et al (1996) study
Peak Systolic Velocity :- PSV in ophthalmic artery was found to be significantly decrease (p<0.001) in POAG & CACG group as compared to control group (Table 1), higher blood flow velocity found in CACG patients compared to POAG patients, might be due to better vascular autoregulation which could protect them from developing damage to optic nerve.
End Diastolic Velocity:- EDV in POAG & CACG groups found to be decreased in all three vessels as compared to control group (Table 2) and was statistically significant (p<0.001). EDV of ophthalmic artery in patients of POAG was not significantly decreased as compared to patients of CACG but EDV of CRA and short PCA was significantly decreased in POAG patients as compared to CACG patients, CRA (P<0.001) and PCA (p<0.05)
Resistivity index: Resistivity index show significant increase in all three vessels of POAG & CACG group as compared to control group (p<0.001) [Table - 1][Table - 2][Table - 3], but RI of POAG versus CACG show no significant difference in OA (p>0.05), significant in CRA (p<0.05) and also significant in PCA (p<0.001).
RI has advantage that its value does not depend on Doppler angle (Contrary to PSV/ EDV), as it's the ratio and hence its absolute value can be used for comparison of results even in different studies which are not suitable for PSV and EDV because their value changes with change in Doppler angle.
| Conclusion|| |
Based on CDI value, in group of glaucoma patients those who eventually had more progressive visual field loss, diastolic velocities were significantly lower and resistivity index were significantly higher compared with stable patients [Table - 1][Table - 2][Table - 3]. Numerous factors other than ocular hemodynamics may have affected the clinical course of the patients. Various therapeutic interventions (medications, laser, and surgical procedures) that had differed among patients during the follow up, and some individual factors (genetics, life habits, and treatment compliance), might have modulated patients response to therapy and might affect the reproducibility of our results. Despite these limitations, a homogeneous group of patients was selected at the outset by CDl, a technique proven to be most useful in ocular blood flow assessment and in depicting the clinical picture of patients with glaucoma.
Our findings are consistent with the large body of evidence supporting the effect of vascular factors in pathogenesis of glaucomatous optic neuropathy and the key position of the OA, CRA & short PCA in the orbital vascular anatomy and in the optic nerve blood supply.
The prognostic aid of CDI in patients with glaucoma supports the use of this technique to select the most appropriate monitoring and therapeutic strategies. The results obtained in our series should be validated in an independent population.
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N C Sharma
D-12, M.B. Government Hospital Campus, Udaipur-313001, Rajasthan
Source of Support: None, Conflict of Interest: None
[Figure - 1], [Figure - 2], [Figure - 3]
[Table - 1], [Table - 2], [Table - 3]