Bruce Willis' wife can determine his needs from looking into his eyes.

The Die Hard star's ability to communicate has been severely impacted by his frontotemporal dementia (FTD) but Emma Heming Willis has learned to read his body language to make "judgement calls" about anything that is bothering her husband.

In an extract from her book The Unexpected Journey: Finding Strength, Hope, and Yourself on the Caregiving Path shared by Us Weekly, Emma wrote: "Because Bruce can't communicate with me (due to the variant of FTD he has, primary progressive aphasia), I must make judgment calls for him about absolutely everything.

"I can't ask him how he's feeling, what's wrong or if something hurts.

"Instead, I read his body language or look into his eyes to understand what's bothering him and what he's experiencing.

"I compare this to the instinct that you have as a parent. With just one glance at your child, you can tell immediately if something isn't right.

"And with one look at Bruce, I can tell if his neck hurts or if he's got a headache."

The 47-year-old model recently revealed that Bruce - with whom she has daughters Mabel, 13, and 11-year-old Evelyn - now lives in a separate home and she recalled breaking the news to their kids that their 70-year-old dad would be living elsewhere.

She wrote: "'We've come to a point in Daddy's disease where the care he requires is changing. It has to be more tailored to his every need.' I told them.

"'And you should be in a home that is more tailored to your needs now. 'Also, Daddy would want you to have playdates, sleepovers, and more freedom than you've been able to have here. That would make him so happy.' "

Emma reassured their daughters that the Moonlighting actor's new house would be a "second home" for the girls.

She described it as a "place they'd keep personal things like toys, arts and crafts supplies, bathing suits, pjs, and games, and that we could go stay with him anytime they wanted".

Along with his kids with Emma, Bruce also has three adult daughters with his former wife, Demi Moore, 62 - Rumer, 37, Scout, 34, and Tallulah, 31.