OCT ANGIOGRAPHY AND DOPPLER SONOGRAPHY IN NORMAL-TENSION GLAUCOMA

[The importance of OCT angiography and Doppler ultrasound methods in diagnosis of optic neuropathies]

This review of literature presents an assessment of circulatory disorders of the optic nerve and the retina in patients with optic neuropathy of different origin by ultrasound and OCTA methods, outlines basic principles of analyzing the state of blood flow in the ocular vessels, and analyzes the results of Russian and foreign research on this topic.

HIGHLIGHTS OF HYPERTENSIVE AND NORMOTENSIVE GLAUCOMA

The paper presents the up-to-date overview of pathogenesis, functional and structural changes in normotensive glaucoma (NTG) and its differences from hypertensive glaucoma (HTG). The autors point out new facts that distinguish both diagnostic groups. In the first place are the results of OCT angiography, which verify the pathology of NTG to the anterior part of optic nerve. Our findings confirmed that vascular component (VD) is more involved in changes of visual field than in perfusion parameters, especially in arteria ophtalmica (AO). Perfusion in arteria centralis retinae (ACR) does not play a significant role in NTG changes in the visual field. VD has very little effect on changes in visual field in HTG. Similarly, the retinal nerve fiber layer (RNFL) for changes in the visual field. Howerver, VD is moderately influenced by changes in RNFL. It should be emphasized that we compared the sum of sensitivity in the central part of the visual field (0-22 degrees) with RNFL and VD. In NTG, the anterior part of the optic nerve is altered. Mainly VD contributes to visual filed changes in NTG. It is also important to note that when the intraocular pressure (IOP) increased above 20 mm Hg, the macular and papillary VD was significantly reduced. Antiglaucomatous treatment with prostaglandins and beta-blockers is essential for the reduction of IOP in HTG. This reduction shoud be bellow 20 mm Hg, in eyes with thinner cornea the decrease in IOP should be more pronounced. It does not matter which antiglaucoma treatment was used. However, it should be noted that prostaglandins have a greater effect on disease progression, but the greater protective effect on the visual field have beta-blockers. Neuroprotectives should be recommended systemically in patients with HTG. When treating NTG, it is important to maintain blood flow of the posterior pole of the eye, but mainly of the anterior part of the optic nerve. Prostaglandins are not suitable in NTG patients, although their effect on IOL reduction is high. Beta-blockers (betaxolol and carteol) and brimonidine are most suitable. Corneal thickness has no effect on disease progression.

OCT ANGIOGRAPHY AND DOPPLER ULTRASOUND IN HYPERTENSION GLAUCOMA

AIMS

The main aim of this work was to find out if there is a correlation between vessel density (VD) and results of measured perfusion values in ophthalmic artery and in central retinal artery of the same eye in a group with hypertension glaucoma (HTG).

MATERIALS AND METHODS

The file included 20 patients with HTG, thereof 13 women of average age 68.7 years (49-80 years) and 7 men of average age 58.4 years (27-81 years). Criteria for inclusion in the study: visual acuity 1,0 with possible correction less than ±3 diopters, approximately the same changes in visual fields in every patient, intraocular pressure (IOP) less than 18 mmHg, no other ocular or neurological diseases. VD was measured by Avanti RTVue XR by Optovue firm, perfusion parameters were measured using Doppler ultrasound with Affinity 70G machine by Philips firm. The peak systolic velocity (PSV) and end diastolic velocity (EDV) and resistance index (RI) were measured both in ophthalmic artery (AO) and in central retinal artery (CRA). Visual field (VF) was examined by quick threshold glaucoma program by Medmont M 700 machine. The sum of sensitivities in apostilbs (abs) was evaluated in the range 0-22 degrees of visual field. The results of sensitivities in visual field were compared to VD and perfusion parameters in CRA and AO of the same eye.

RESULTS

Pearsons correlation coefficient (p = 0,05) was used to assess the dependency between chosen parameters. By comparing VF and VD from measured areas, strong correlation (r = 0.64, resp. 0.65) was revealed. It was then proved that VD (WI-VDs) correlates with RICRA weakly (r = -0.35) and moderately strongly (WI-VDa r = -0.4, PP-VDs r = -0.43 and PP-VDa r = -0.45). This means that with increasing resistance index in CRA the density in VD decreases. The other correlations between VD and perfusion parameters (PSV and EDV) in CRA and AO were not significant.

CONCLUSION

Measured values showed that the vascular component of VD has a huge impact on the changes in visual fields in HTG. Weak to moderate influence exists between VD and RI in CRA. OCTA has proven to be more suitable than Doppler ultrasound for determining the condition of blood circulation in the eye.

Optical coherence tomography angiography and the visual field in hypertensive and normotensive glaucoma

BACKGROUND

Hypertensive glaucoma (HTG) causes damage to the retinal ganglion cells and eventually to the entire visual pathway due to high intraocular pressure (IOP). However, increased IOP will also affect the vessel density (VD) of the posterior pole of the eye and the related retinal ganglion nerve fibres (RNFL). In normotensive glaucoma (NTG), the retinal ganglion cells are relatively intact. The pathology is at the level of ganglion fibres. The unanswered question is what has altered ganglion cell fibres at the level of the retina and optic nerve head in NTG?

AIM

The aim of this study was to determine whether there is a correlation between the retinal nerve fibre layer (RNFL) and vessel density (VD) at the same altitudinal half of the retina and the sum of sensitivities of the contralateral half of the visual field of the same eye in hypertensive and normotensive glaucoma (NTG).

METHODS

Our group included 20 patients with HTG and 20 patients with NTG. The Pearson's correlation coefficient r was used for evaluation of the relationship of the peripapillary RNFL and VD, visual field (using the fast threshold glaucoma program) as the sum of sensitivities in apostilbs (asb) to the extent of 0-22 degrees. The results of sensitivity were compared with the RNFL and VD of the contralateral altitudinal half of the retina in the same eye.

RESULTS

In the HTG group there was a moderate relationship between RNFL and VD (both hemifields), but no relationship between RNFL and VF. VD SH and VF IH showed weak correlation and VD IH and VF SH showed no correlation. In patients with NTG, we found a strong correlation between RNFL and VD (both hemifields), between VD SH and VF IH a moderate correlation, between VD IH and VF SH also a moderate correlation and a weak correlation between RNFL and VF.

CONCLUSION

By comparing the RNFL and VD at the same altitudinal halves of the retina, we found a moderate correlation in HTG and a strong correlation in NTG. We found no or a weak correlation between VD and VF in HTG. In NTG the relationship between VD and VF showed a strong correlation. These findings reveal the differences in the diagnostic groups.