Brief Answer:
A Lot of structures are involved in conduction of Visual Impulses.

Detailed Answer:
Dear Sir,

Light Falls on Your Retina (a layer in eye). From this impulses start and go via Optic Nerves . From Optic Nerves to Optic Chiasma. From Optic Chiasma to Optic Tracts. From Optic Tract to Lateral Geniculate Bodies. From Lateral Geniculate Bodies to Optic Radiations. From Optic Radiations to Occipital Cortex

So
A Lots of structures are involved in conduction of Visual Impulses.
Of these, quite a few are supplied by Internal Carotid Arteries and quite a few from Vertebra Basilar Arteries

So,"stroke last summer that affected vision and memory" can be either an Internal Carotid Artery Problem or Vertebra Basilar Artery Problem

It is not necessary that Only Occipital Lobe Damage affect Vision. Impairment of Blood Circulation to
1. Retina
2. Optic Nerves
3. Optic Chiasma
4. Optic Tract
5. Lateral Geniculate Bodies
6. Optic Radiations
or a combination of these can affect Vision

Now Coming to your statement that there is no damage to Optic Nerve, it is quite possible that one of the above structures other than Optic Nerve have been involved by the blood clot.

This is what I meant by "You had a stroke last summer that affected my vision and memory. This can very well due to Obstruction in Carotid Arteries Or Anterior Circulation Stroke. Carotid Arteries supply Ophthalmic Artery - The artery to Optic Nerve and Orbit - and hence you can get visual disturbance even when Occipital and Parietal Lobes are not involved. Memory can be affected due to Anterior Circulation Stroke too"

and

"it is perfectly possible for a plaque breaking off from one of the carotid arteries to cause a stroke in which you had memory disturbances and vision disturbances"

So
To Conclude

"The internal carotid arteries supply blood to the anterior three-fifths of cerebrum, except for parts of the temporal and occipital lobes."
But
Involvement of Anterior three fifths of cerebrum can also produce disturbances in vision and memory

If we still have doubt as to which lobe was affected during the stroke, we can look at the CT or MRI taken during the episode.

If Occipital Lobes had been involved as per CT and MRI, then the clot must have risen from Carotid artery and gone to the occipital lobes through the circle of Willis

If Areas supplies by Anterior Circulation are involved, then the most logical explanation is that the visual disturbances is through one of the structures in the Optic Pathway I have mentioned above

Hope you found the answer helpful.

If you need any clarification / have doubts / have additional questions / have follow up questions, then please do not hesitate in asking again. I will be happy to answer your questions.

Let me know if I can assist you further.
Take care.

-oOo-

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