Last week, I had the opportunity to attend the NZAO conference at the Beehive in Wellington, at New Zealand Parliament. Paul Graveson's session, Understanding Visual Function and Dysfunction in Patients With Dry AMD: a Guide for the General Optometrist, opened day 2 and explored macular degeneration (AMD), including the impact of advanced disease and geographic atrophy, and it offered a particularly powerful way of explaining something that can be difficult for patients and their families to understand.

You can have reasonably good visual acuity and still struggle to see clearly.

For many people, an eye test is simply about reading the letters on a chart. If you can read the bottom line, you assume your vision must be good. But vision is much more complex than that, and macular degeneration is an excellent example of why.

Your vision is more than the letters on an eye chart

Visual acuity measures how well you can distinguish letters or symbols of a particular size under controlled conditions. It is an important part of an eye examination, but it doesn't tell us everything about how you see the world.

The macula is the central part of the retina responsible for detailed vision. It helps us recognise faces, read books, see fine detail and carry out many of the tasks we take for granted every day.

In age-related macular degeneration, damage to the macula can affect the quality and completeness of central vision. The result isn't necessarily that everything becomes uniformly blurry or dark. Instead, parts of what you are looking at may become distorted, faded or missing altogether.

This is where an analogy shared during the conference really stuck with me.

Imagine trying to complete a puzzle with missing pieces

Think about a jigsaw puzzle. You might remove a few pieces, but still have enough of the picture left to recognise what it represents. Your brain can use the remaining information to work out the overall image.

Now imagine gradually removing more and more pieces.

At first, you might still recognise the picture without much difficulty. But as the gaps grow, it becomes increasingly difficult to understand what you are looking at. Eventually, so much information is missing that putting the picture together becomes a real challenge.

This is a useful way to understand what can happen in advanced macular degeneration, particularly when a person develops geographic atrophy.

Geographic atrophy involves the progressive loss of retinal cells in affected areas of the macula. As these areas expand, more of the visual information needed for detailed central vision can be lost.

The important point is that the remaining pieces of the picture may still be visible. The difficulty is that too many of the pieces needed to make sense of the whole image are missing.

Why reading can become so difficult

Reading is a perfect example of this problem.

When you look at a page, you don't process every letter independently. Your eyes move across words and lines, while your brain combines the visual information to help you understand what you're reading.

Someone with advanced macular degeneration might still be able to identify an individual letter, or even a word, when it falls within an area they can see clearly.

But the words surrounding it may be distorted or missing. Finding the next word, keeping track of a line and moving smoothly through a paragraph can become exhausting.

Imagine trying to read a sentence when you can see the word directly in front of you, but the words before and after it keep disappearing. You might be able to work out individual pieces, yet struggle to put the sentence together.

That is why someone can retain a reasonable visual acuity measurement and still experience significant difficulties with reading, recognising faces, navigating familiar environments or completing everyday tasks.

Their vision hasn't necessarily disappeared altogether. Rather, the information they need to interpret the world has become incomplete.

Why this matters when we assess eye health

As optometrists, we need to look beyond a single number on an eye chart.

A comprehensive eye examination considers the health of the retina and macula, alongside visual acuity, symptoms, medical history and other clinical findings. Retinal imaging and optical coherence tomography (OCT), can help us assess retinal structures and identify changes that may not be apparent from visual acuity alone.

It is also important to understand what a person is experiencing in daily life. Are they struggling to read despite being able to see the letters? Are faces becoming harder to recognise? Are they finding it difficult to move around in unfamiliar places or perform tasks they used to manage easily?

These experiences matter. They help us understand the functional impact of an eye condition, not just what the test results tell us.

For people living with macular degeneration, appropriate monitoring, advice, low-vision support and referral for specialist assessment or treatment can all play an important role in their care.

Seeing the person, not just the test result

One of my key takeaways from the NZAO conference was a reminder that good eye care requires us to understand more than what a person can read on a chart.

A test result gives us valuable information, but it doesn't always tell the full story of someone's visual experience.

The puzzle analogy is a simple way to explain a complex condition. It helps us appreciate why losing relatively small areas of retinal function can have a substantial impact, and why more extensive damage can make everyday activities so challenging.

At Ashburton Eyecare, our goal is to help people see the world to the best of their ability. That means looking beyond the letters on the chart, understanding what matters to each person and considering how their vision affects their quality of life.

Because good vision isn't just about seeing the pieces. It's about being able to put them together.

If you have noticed changes in your central vision, increasing difficulty reading or distortion when looking at straight lines, arrange a comprehensive eye examination. Sudden changes in vision should be assessed urgently.