Branch Retinal Vein occlusion and Glaucoma
Dr Swati. Mishra, Dr Prabhat Nangia, Dr Sarang Lambat, Dr Vinay Nangia
Suraj Eye Institute, 559 New Colony, Nagpur
A female, 78 years of age, presented to us for a regular checkup. She was a known diabetic and hypertensive since past 4 years. On examination the unaided visual acuity was 6/6p, N6 in right eye (RE) and 6/6, N6 in left eye (LE). The anterior segment showed pseudophakia in both eyes (BE). Intraocular pressure (IOP) measured with Goldman applanation tonometer was 16 mmHg in RE and 15 mmHg in LE.
She was started on combination of brimonidine tartrate (0.2%), timolol maleate (5%) for glaucoma and carboxymenthycellulose drops for lubrication.
Venous occlusions are known to occur in association with glaucoma. In this patient in the RE there is the presence of superotemporal BRVO, which is associated with the presence of significant collaterals especially temporal to the fovea running vertically. BRVO is often known to be associated with loss of retinal nerve fiber layer in the segment of the optic disc associated with the area where the occlusion has occurred. The retinal nerve fiber layer shows the presence of loss in the inferotemporal segment and global loss in the RE. The LE also shows generalised thinning of the RNFL.
The possibility of developing a venous occlusion increases with age and in the Central India Eye and Medical Study the prevalence was found to be 0.42%. Therefore one may always assess the macula to rule out the presence of BRVO in an eye with glaucoma and similarly one may rule out glaucoma in an eye with BRVO. This may be done by making an assessment of the optic disc and using structural and functional tests.
A red herring would be – initially the swelling (false thickening) of the RNFL in the segment where there is BRVO due to the parapapillary oedema. This may hide the presence of pre-existing RNFL loss. Similarly following resolution of the BRVO induced oedema over a period of time, the segment of the neuroretinal rim coinciding with the area of BRVO may show pallor associated with RNFL loss, even in the absence of glaucoma. This RNFL loss in the absence of glaucoma may be wholly related to the BRVO.
In this patient, there is also the presence of an area of hard exudates arranged in a circinate fashion superotemporally. It is likely that in the centre of this area lie microaneurysms or a macro-aneurysm. This could not be ascertained, since a FFA could not be done. The importance of such a lesion is that it interferes with the ganglion cell deviation and thickness map in this patient, since the segmentation may be inappropriate in this area of retinal oedema associated with the hard exudates.
These differentiations are important, to understand the clinical picture of a patient with RNFL loss in association with both BRVO and or glaucoma.
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Dr Vinay Nangia
MS, FRCS, FRCOphth
Suraj Eye Institute