Thanks for the additional information.
Sorry to hear that Willie is not feeling well. Based on what you are describing, a toxin from a plant or chemical outside could cause his symptoms. Other reasons that his pupils could be dilated are high blood pressure (hypertension), kidney
disease, an eye disorder itself such as retinal detachment, uveitis, or an infection in both eyes. A neurologic disease such as head trauma or and infection, such as toxoplasmosis, could also cause the pupils to become dilated.
I am glad to hear that Willie is drinking and eating. Since there are so many different toxins and disorders that can cause dilated pupils and overall not feeling well the best way to get a more exact diagnosis would be to take him to your vet to have an exam and possible some bloodwork to make sure his kidney and liver function tests are normal. Many toxins that cause dilated pupils can also cause some damage to these organs therefore this is a way that you could rule out a toxin.
I would watch his vision very closely because disorders such as high blood pressure and the eye diseases can potentially cause loss of vision for him. A vet could give him medications to help with high blood pressure or a disease such as toxoplasmosis to reverse any potential long term vision changes.
Overall I would consider having your vet examine him if this is possible otherwise watch him very closely for any vision changes or lethargy.
Hope this helps -please reply if you have questions.