In this article about survivorship bias, we start by reflecting back to the 1930s. During World War II, the Allied forces wanted to make their bomber planes safer. They looked at the aircraft that returned from missions and carefully mapped out all the bullet holes.

The logical first thought was to add more armour to the areas that were most frequently hit, like the wings and the fuselage. It seemed to make perfect sense.

But a statistician named Abraham Wald saw a critical, life-threatening flaw in their thinking. He argued that the military should do the exact opposite. They should reinforce the areas where there were no bullet holes at all. The reason was simple but profound.

The military was only looking at the planes that had survived. The bullet holes they were seeing were in places an aircraft could get hit and still make it back home. The planes that were hit in the unmarked places, the engines, the fuel system, and the cockpit, were the ones that never returned. They were the silent, missing evidence.

This is the classic story of survivorship bias. It’s our natural human tendency to focus on the people, things, or strategies that “survived” a process. We inadvertently overlook those that did not, simply because they are not visible to us. This powerful cognitive trap is everywhere, and we need to be acutely aware of this form of survivorship bias in optometry.

Why We Must Spot Survivorship Bias in Optometry

t is so important that we are aware of this particular bias in optometry. It can quietly and persistently influence our clinical decisions, our business strategies, and our standards of practice.

We might think a certain approach is working well because we are only seeing the successful outcomes. We get positive feedback from the happy patients, the ones who adapt to a new lens or whose treatment is a success. We don’t see the patients who were unhappy, confused, or dissatisfied and simply voted with their feet, never to return to our clinic. We only see the survivors.

This can lead to a dangerously false sense of security in our methods. It can stop us from questioning, from improving, and from seeing the full picture of our impact on patient care. It feels good to focus on success, but it takes real professional courage to actively look for the failures.

Recognising survivorship bias in optometry is not just an academic exercise. It is a fundamental part of providing safe, effective, and truly patient-centred care. It forces us to ask a harder, more important question: what about the evidence I don’t see?

How this bias in optometry can affect our work

I once worked as a locum in a practice where it was common for optometrists to record “no change” in a patient’s prescription. From their point of view, it seemed like a success. The patients were happy because they didn’t have to spend money on new glasses. The optometrists felt they were confirming the stability of the patient’s vision and building goodwill. They were looking at the “survivors”—the patients who kept coming back and didn’t complain.

But this was a classic case of survivorship bias in optometry. The “no change” was often based on a small 0.25D difference from the previous test, not from the glasses the patient was actually wearing every day. After three or four such visits, a clinically significant change of 0.75D or more had built up, but it was being missed because each small step was dismissed.

I regularly saw patients with six-year-old glasses that were scratched, worn, and no longer fit for purpose, struggling with symptoms that were clearly refractive. The system that seemed successful on the surface was, in reality, failing them. Even when I explained that their prescription was stable, I would tell them they might want to update their glasses for style or due to wear and tear.

Many patients didn’t even realise this was an option and were thrilled to hear they could go out and pick a new pair. They were “surviving” with glasses they didn’t like because of a system built on this subtle survivorship bias.

The dangers of not tackling survivorship bias in optometry

The dangers of not confronting survivorship bias in optometry extend beyond clinical judgements. As a locum, I often inherit patient records from optometrists who have retired after long careers.

Sometimes, I’ll see record cards with very minimal notes, lacking the detail we are now expected to provide. It can be tempting to look at this and think, “Well, they had a long and successful career. They were never struck off for poor record-keeping, so their methods must have been fine.”

This is a dangerous trap. You are looking at a survivor. You have no idea if they were ever audited, if they ever had a complaint against them that was settled quietly, or if they were simply lucky never to have faced a serious clinical issue that required detailed records. The evidence you don’t see is the potential for near-misses or the problems that were never reported.

Following their example because they “survived” is a huge risk. Professional standards evolve for a reason, usually in response to the “planes that didn’t make it back” – the cases where things went wrong. They may be retired, but you have your whole career ahead of you. You cannot use someone else’s survival as evidence to cut corners in your own practice. This is a critical form of survivorship bias to avoid.

How Survivorship Bias Affects the Patient’s Viewpoint

This form of bias in optometry doesn’t just affect clinicians; it heavily influences our patients’ decisions too, often in ways that can be detrimental to their health.

We see it all the time. A patient might say, “My friend bought his glasses online and they’re absolutely fine, so I’ll do the same.” They are looking at the one success story they know. They are not seeing the silent majority of people for whom online glasses were not fine (the ones with inaccurate measurements, poor fitting, and visual discomfort who had to come back to a practice to get things sorted). They only see the survivor. They don’t see the data showing a significant percentage of online glasses fail to meet the required standards. This is a clear example of survivorship bias.

We see the same logic with smoking. A patient might resist advice to quit by saying, “My dad smoked 20 a day his whole life and lived to be 90 without any eye problems.” They are focusing on the one person who survived against the overwhelming statistical odds. They are ignoring the invisible evidence of all the people who developed macular degeneration, cataracts, or other diseases as a direct result of smoking.

The single survivor’s story feels more powerful and real to them than the data. This is survivorship bias in optometry at its most personal, and it’s our job to gently help patients see the bigger picture beyond the one story they are clinging to.

Addressing Bias in Optometry Day-to-Day

So, how do we consciously fight against this cognitive trap in our busy clinics? The first step is to get out of the “it’ll be fine” mindset and actively look for the missing data.

We must actively recall the GOC standards we are held to and strive to do our best for every single patient. This means getting all the information, justifying our actions clearly in the records, and not taking shortcuts. It means advocating for our patients’ health and helping them understand their own risk factors.

For me, being a natural overthinker can actually be a tool. I tend to play out multiple possible outcomes in my head, which helps guide me down the correct path. But a more structured approach for everyone is to actively find the reasons behind your successes. Be objective though and don’t let it evolve into Imposter Syndrome.

If a new contact lens seems to be working well, ask yourself: am I only hearing from the happy wearers? What about the ones who might have dropped out? Perhaps you could implement a system to follow up with patients who don’t return for their follow-up appointments.

It’s about actively looking for the silent, missing data. It means questioning your own justifications at times, not to create self-doubt, but as a powerful tool for professional growth and to counter survivorship bias in optometry.

Conclusion

The story of the WWII planes teaches us a vital lesson. The most important evidence is often the evidence that we cannot see.

In our clinics, this means we must train ourselves to think about the patients who don’t return, the treatments that fail silently, and the advice that is ignored. Relying only on the “survivors”, or the happy patient, the successful outcome, the colleague who never got caught, gives us a dangerously incomplete and overly optimistic picture of our practice.

Being a truly excellent clinician means fighting against this inherent survivorship bias that faces us in optometry. It means we must constantly seek out the full story, not just the happy ending we see in front of us. This reflective practice is at the very heart of our duty of care.

Further Reading

A selection of books cover the topic of survivorship bias in more depth. The links to the following products are affiliate links that will generate a small commission fee for The Eye Care Advocate (at no cost to yourself), which help support the ongoing project this website aims to achieve. The author or The Eye Care Advocate cannot be held responsible for the content or sales made on 3rd party websites.

The Invisible Graveyard: Hidden Lessons of Missed Opportunities
by Kanat Daurenbek

We are taught to learn from success. But what if the most important lessons are hidden in the failures we never see?

“The Invisible Graveyard” takes you on a compelling journey to the rarely explored side of success, uncovering the powerful stories of missed opportunities and overlooked mistakes. It examines the cognitive biases that draw us to survivor stories and prevent us from learning from the silent evidence of failure. If you want to understand why we make the decisions we do and learn how to see the full picture, this book provides the tools to make more balanced, insightful judgements in your career and life. Don’t just learn from success; master the art of learning from what’s missing.

Top 100 Cognitive Biases Explained
by Five Mile Publications

Why Do Smart People Make Dumb Decisions? The Answer Lies in Your Brain’s Hidden Shortcuts. Every day, your brain takes mental shortcuts to help you survive and thrive—but sometimes, those shortcuts backfire. From overconfidence to confirmation bias, these invisible forces shape your choices, skew your perception of reality, and silently steer your emotions, relationships, and beliefs.

In Top 100 Cognitive Biases Explained!, this book unpacks the most fascinating mental glitches that influence your thinking without you even realizing it. Whether you’re making financial decisions, arguing with a friend, or scrolling social media, your brain is being tricked—and this book reveals exactly how. If you want to understand the hidden forces that shape our thinking, this is an essential read for seeing the world—and ourselves—more clearly.