Six weeks ago, I visited an elderly lady called Maureen who can no longer go out unaccompanied due to a physical illness that affects her mobility. She’s 85, opinionated about Brexit, funny and bright as a button. She was recommended to our domiciliary service by her local Specsavers after being a customer there for more than 20 years.

At the time of the test I noticed some moderate cataract and discussed her options with her. Despite it reducing her visual acuity a little, she was adamant she did not want surgery and we agreed that I should go back in a year and have another look. We found that a new prescription helped so I advised new glasses for distance and near which were ordered on the day and fitted within a couple of weeks.

Then just last week, Maureen’s son rang me to say he was concerned that his mother had been told she had cataracts and had not been referred for surgery. He wanted her to be referred and wanted me to explain why I didn’t refer her at the time.

He clearly thought that, as her son, he had every right to have information about his mother’s test, and to demand that she be referred. But that is not necessarily the case.

I faced a similar situation a few months ago where another patient’s son called to ask about his father’s eye test. Although the son said he had power of attorney, I needed to check with him as there are different kinds giving different permission. In his case, it was a Health and Welfare Lasting Power of Attorney (LPA) because the father had decided he wanted his son to make decisions on his behalf, even though he was still capable of making some decisions himself, which meant I could share the information with the son.

The premise of the Mental Capacity Act 2005 is that I have to assume my patient has the capacity to make his or her own decisions – even if it’s something that does not seem sensible to me – unless I have evidence to the contrary. A patient may be capable of making some decisions but not others. They may be able to decide which frame they like best, for instance, but not whether it is within their budget.

As an optometrist I want to make every effort to encourage and support patients to make decisions for themselves or to be part of a decision that is made about them.

Back to Maureen. As she has got full capacity, and wants to make her own decisions, her son doesn’t have any rights to insist that she’s referred, even when it feels like the right thing to do.

Everything has to be in the best interests of the patient. If I’m satisfied that the patient has given permission, which is often easily given when the relative is present at the test, or that the relative has the correct legal power, I can discuss anything with them as if they were the patient. If they haven’t got the necessary permission or legal power then I can’t.

Our responsibility is to the patient in the first instance, not their relatives. In domiciliary it’s not uncommon for the family to think that they should have a right to know what happened at the eye test. It can be really difficult, and it’s essential to understand the legislation around LPAs, the Data Protection Act 1998 and the new General Data Protection Regulation.

In Maureen’s case, I didn’t want to quote the law at her already worried son, so I had to be diplomatic. I gently told him that there are laws to protect vulnerable people and that legally I wasn’t able to talk to him about his mother’s specific case unless she had said it was OK and I needed evidence of that. I explained that we could still talk more generally so we did talk about cataracts and the fact that older people typically can have a small amount of cataract and that it usually doesn’t need immediate referral.

Her son went away happier, fully informed about the options that a patient may have with regards to possible future cataract surgery and Maureen will be reviewed again in a year’s time.

Sanjiv Koasha is a Specsavers domiciliary optometrist director in Birmingham.