Hemi-central retinal artery occlusion in young adults.

Dear Editor,

We thank Chopdar[1] for the interest in our article,[2] and concur with the author about our finding of early branching of the central retinal artery (CRA) prior to its entry through the lamina cribrosa. We used the term ‘Hemi-central retinal artery occlusion’ to describe a clinical entity. This early branching pattern of CRA has been documented on Doppler imaging [Fig. 7] for the first time in our report.[2] This provides evidence for an embryological basis of the unusual branching pattern of CRA.

The author states, “In Case 1, [Fig. 1] shows associated choroidal infarct of the upper half of the fundus.” We agree that choroidal infarction may be seen concomitantly along with central retinal artery occlusion (CRAO) but we did not encounter such lesions in our case, as is also evident from Fig. 3. Choroidal ischemic lesions as seen in malignant hypertension consist of retinal pigment epithelial lesions (secondary to choroidal infarction), serous retinal detachment and in some eyes, white lines due to choroidal sclerosis.[3] Our patients lacked any of these lesions. Fundus fluorescein angiography (FFA) findings of choroidal ischemia may range from delayed filling of choroidal circulation to near-total lack of choroidal perfusion in infarction. A spectrum of choroidal perfusion defects have been reported to exist with CRAO.[4] Amalric described it earlier[5] and similar findings (Amalric sign) have also been reported by others in cases with CRAO and lateral posterior ciliary artery occlusion. The author further states that, “Fig. 2 shows that the upper artery is a cilioretinal artery whereas the lower one is the true central retinal artery.”

Figs 2, 9, 14 and 18 depict separate evolution of central retinal hemi-trunks from the optic disc cup and not at the margin of the optic disc.[2] This has been corroborated with Doppler imaging that shows branching from CRA and not from choroidal circulation. Cilioretinal arteries have been shown histologically to originate from short posterior ciliary arteries and, in rare instances, directly from choroidal vessels.[6] First described by Muller in 1856,[6] they appear ophthalmoscopically to emerge from the optic disc or disc margin separately from CRA or its branches.[7] They make a characteristic bend as they leave the disc margin and are recognizable on fundoscopy. It has also been recognized, however, that ophthalmoscopic examination is not a true guide to the presence or absence of a cilioretinal artery.[4] Hence, it is difficult to say just from Fig. 2 of Case 1 that the upper artery is a cilioretinal artery.

The author further states that, “FFA in Fig. 3 shows that the upper artery is brighter than the lower indicating that this is an earlier branch”.

FFA in our cases shows that the upper artery is brighter than the lower but this does not necessarily mean that it is a cilioretinal artery. However, carotid Doppler study in all cases showed bifurcation of CRA into two hemi-trunks just behind the lamina cribrosa, ruling out the possibility that the upper artery is an earlier branch. We rather postulate that the affected branch being possibly less tortuous in its course shows earlier filling than the other.

Finally, the author states that, “Cases 2, 3, and 4 are identical to Case 1 and all of them are associated with choroidal and retinal ischemia”. This aspect has already been dealt with as above.