Abstract

Background:  Primary Open-Angle Glaucoma (POAG), is sometimes called "the silent thief of sight" because in the early stages of the disease there are no warning signs — no pain or vision loss. The trabecular meshwork in the angle of anterior chamber where the aqueous exits the eye become blocked. Hence the pressure inside the eye, ie, intraocular pressure (IOP) increases. The fact that the optic nerve head perfusion is directly related to retrobulbar circulation, which is directly accessible to ultrasound study, makes Colour Doppler imaging (CDI) a prime tool for the evaluation of early changes in vascular flow related to glaucoma. The use of CDI has been validated already in the evaluation of moderate and advanced glaucoma patients, consistently detecting flow velocity alterations and increased resistivity index in these patients in comparison with healthy individuals.

Aim: Primary objective is to assess the blood flow in ocular vessels namely Central Retinal Artery, Short Posterior Ciliary Arteries and Ophthalmic Artery in patients with established Primary Open Angle Glaucoma (POAG) with visual field defects compared with patients of the same disease without visual field defects in standard automated perimetry. The present study search alteration in ocular blood flow indices in POAG and to assess if reduced retro-ocular blood flow is associated with disease progression. Circulatory alteration early in the disease, might be used 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 in glaucoma patients. Hence treatment modalities might be changed in future with emphasis directed more on normalization of circulatory alteration rather than just IOP.

Materials and Methods: This is a descriptive study with diagnostic test evaluation. 64 patients, above 40 years of age, attending the weekly glaucoma clinic in the Ophthalmology outpatient department and referred to the Department of Radio diagnosis of T.D. Medical College Alappuzha, who are clinically diagnosed to have Primary open angle glaucoma constituted the study group. PSV, EDV and RI of Ophthalmic, central retinal and short posteroir ciliary arteries are studied. Analysis of The diagnostic performance of RI of Ophthalmic artery, Central retinal artery and Short posterior ciliary arteries was evaluated using Receiver Operating Characteristic (ROC) curve analysis, keeping perimetry based classification of visual field defect as the base. ROC curves were also used to compare the diagnostic performance of the three RI values. The data analysis was done in IBM SPSS statistics version 23 and MED CALC version 16.8.4.

Results: Mean intraocular pressure and cup-disc ratio were found statistically significant among the two groups with and without field defects. The study showed significantly lower velocities (PSV and EDV) of ophthalmic artery and central retinal artery in POAG patients having visual field defects in comparison with those without visual field defects. There was no statistically significant difference in the PSV of short posterior ciliary artery among the 2 subgroups of the sample. The resistivity index (RI) was significantly higher in all the three ocular vessels in POAG patients having visual field defects, when compared with those having a stable visual field. The diagnostic capability of RI of ocular vessels- ophthalmic artery, central retinal artery and short posterior posterior ciliary arteries in patients with and without field defects were compared using the ROC curves, which showed statistically significant area under curve in all the above mentioned vessels.

Conclusion: In view of the statistically significant differences in the Doppler indices of ocular vessels among the POAG patients with and without visual field defects, further research is required in this field to establish the usefulness of colour Doppler imaging in POAG.