The caster can see what his eye would normally see by concentrating for a round and spending a blood pool point. The caster can only see Obfuscated characters if his Auspex is high enough.
When activated the eye glows dimly (but see below) and can only be damaged by fire (which destroys it) causing one health level of damage to the caster which cannot be soaked (but can be healed with blood in the normal way) (or how about using Intelligence to soak diff.9?) as well as a headache which lasts all night (-1 dice off all actions). It takes one complete round to break the link but if the caster wants to break it quickly then he must roll Wits+Alertness (diff 7).
If the caster has the Obfucate discipline then he can attempt to prevent the eyefrom glowing in use although he can't keep the eye invisible. eg. If the caster has a suitably brooding picture of his mad ancestor then he can perform the ritual over one of the eyes and use Obfucate to make the eye look like the eye in the painting when in use. The level of Obfucate req'd to dothis is irrelevent but obviously a character with a higher Auspex can see the eye as it would normally appear.
The ritual takes an hour longer to perform if the caster is attempting to Obfuscate it (no roll is req'd) however the caster must maintain the "cloak" by spending 1BP Pt a night.