Thanks so much for the answers to my questions.
While I know it must seem shocking to you that Lucey could lose her vision so suddenly, it usually does happen this quickly. Vision loss is often quite acute with no warning signs at all.
Cataracts can develop which will cause blindness but the lens are white in appearance when this happens, not cloudy as you are describing. This also tends to be a more gradual process but can be secondary to diabetes (which I'd want to rule out in a cat this age if they developed).
Most likely, her lens are becoming thicker secondary to her age and are not related to her acute vision problems.
For a cat her age, there could be several different explanations for this problem:
1. Hypertension which is rarely primary in a cat but typically secondary to either problems with the kidneys or hyperthyroid disease or diabetes. Blood work would be needed to determine if she has one of these underlying conditions. Blood pressure measurements can also be done to determine if she's hypertensive and she could be treated for it.
However, in most cases, vision loss will be permanent. The advantage of diagnosing and treating hypertension is so that additional damage is not done to her organs such as her kidneys. So, while she probably wouldn't regain her sight, further damage could be prevented.
2. Fungal infections such as cryptococcus can cause acute blindness but may not be common where you live (they aren't where I practice). This LINK discusses this condition.
3. Feline Infectious Peritonitis (FIP) if she's been an outside cat; if she's been inside, then this is not a likely cause of acute blindness for her.
This may be a more difficult diagnosis to make, but blood work might be suggestive of it. Cats with this condition are usually much sicker as well.
This LINK discusses this condition.
4. Lymphoma which, unfortunately, is a cancer. This condition might be more difficult to diagnose as well. Blood work might show changes or she might start developing other signs such as lethargy, weight loss or disinterest in food.
5. Toxoplasmosis usually causes inflammation in the eyes (uveitis) but could cause blindness. This LINK discusses this condition. This is probably the best condition on the list since it can be treated with Clindamycin.
6. Retinal diseases such as a detached retina; we often don't have a good understanding of why these conditions occur.
Again, permanent vision loss would be expected.
Many older cats will have a condition called Iris Atrophy where their pupils remain dilated. Their iris doesn't have the elasticity it did when the cats were younger; therefore, the pupil remains more dilated.
I realize that my answer may not be what you want to hear but I would be doing a disservice to both you and Lucey if I were less than truthful and honest in my response to you. I hope you understand.
I also hope that this is helpful and provides you with the possible explanations for her acute vision loss. Deb