Sir,

We would like to thank to Dr. McLeod for his constructive contributions to our paper describing retinal vascular occlusions in two cases with homocystinaemia.1 In our paper, we have primarily focused on the finding of homocystinaemia as a cause of vascular occlusions in young patients; however, we have not discussed the probable mechanisms of association of arterial and venous obstructive disease. Three different clinical syndromes have been suggested describing simultaneous arterial and venous obstructions of the retina including; the combination of central retinal artery and vein obstruction; combined occlusion of central retinal vein and cilioretinal artery; and combined branch retinal artery and central retinal vein obstruction.2 We agree with Dr McLeod in that the arterial obstruction may actually be a relative hypoperfusion of the cilioretinal arteries secondary to increased retinal venous pressure.3, 4 Although this dependent occlusion is the most probable explanation, therapeutic lowering of the intraocular pressure was attempted in the presented case considering the other possibilities like two simultaneous (but separate) occlusions which may be the case in a patient with homocystinaemia.