What Can an Eye Exam Detect? How Your Eyes Can Reveal Signs of Diabetes, High Blood Pressure, Cholesterol and Even Cancer
- Manny Alfaro
- 16 hours ago
- 10 min read
Written by Manny Alfaro
I recently went to the optometrist at Costco for what I thought was going to be a pretty ordinary appointment.
I needed new glasses.
That was it.
Then the eye doctor did something that completely changed the way I think about eye exams.
They looked deep into the back of my eyes and showed me the blood vessels, veins, retina and optic nerve. As we talked about what they could see, the doctor explained that changes in this part of the eye can sometimes reveal clues involving cholesterol and cardiovascular disease, diabetes, high blood pressure and even certain cancers.
I remember thinking:
Wait. You can see all of that by looking into my eyes?
It sounded almost futuristic.
So I started researching it.
It turns out there is some remarkable science behind what eye doctors are able to see — but there are also important limitations everyone should understand.
Your eye exam cannot replace a cholesterol blood test, diabetes screening, cancer screening or your regular physical.
But the back of your eye really can provide doctors with a unique window into what may be happening elsewhere in your body.
And once you understand why, that routine eye appointment suddenly seems much more important.
Why Can an Eye Doctor See So Much About Your Health?
At the back of your eye is the retina, a thin layer of light-sensitive tissue that receives light and sends signals through the optic nerve toward the brain.
Running across the retina is an intricate network of tiny arteries and veins.
During a comprehensive eye examination, an eye doctor can examine structures including the retina and optic nerve. Dilating the pupil allows the doctor to see a larger area inside the eye. (National Eye Institute)
That creates an unusual opportunity in medicine.
Doctors normally cannot simply look at the tiny blood vessels inside your heart, kidneys or brain during a routine office visit.
But retinal blood vessels can be photographed and examined noninvasively.
That is one reason researchers have become increasingly interested in retinal imaging as a potential source of information about cardiovascular and systemic health. (Nature)
What Was the Eye Doctor Probably Looking At?
There are several different tests an optometrist may use.
A traditional dilated examination allows the doctor to look through the pupil and examine the retina and optic nerve.
Digital retinal or fundus photography can create a detailed photograph of the back of the eye.
Other technologies, such as optical coherence tomography, or OCT, can produce detailed cross-sectional images of retinal structures.
I cannot know exactly which test was used during my Costco appointment without looking at the examination report, but the important part is what surprised me:
Those tiny vessels aren't just part of your eyesight. They can also show the effects of diseases that affect blood vessels throughout the body.
Can an Eye Exam Detect Diabetes?
This is one of the clearest examples.
Diabetes can damage the tiny blood vessels that supply the retina.
The National Eye Institute explains that diabetic retinopathy affects retinal blood vessels and may initially cause no symptoms at all. Over time, damaged vessels can become blocked, leak fluid or bleed, while abnormal new vessels may develop. (National Eye Institute)
That means someone can have significant changes developing in the back of the eye while still feeling as though their vision is relatively normal.
Eye doctors may see signs such as:
tiny areas of bleeding
leaking blood vessels
swelling
blocked vessels
abnormal new vessel growth
retinal damage associated with long-term diabetes
This doesn't mean an eye doctor can look at your retina and tell you your exact blood sugar level.
An A1C or other blood-glucose testing is still necessary to diagnose and monitor diabetes.
But an eye examination can reveal damage caused by diabetes and sometimes identify that damage before a person notices changes in vision. (National Eye Institute)
That alone makes regular eye examinations much more important than simply updating your glasses.
Can Your Eyes Show High Blood Pressure?
They can show damage associated with high blood pressure.
Think about what happens when excessive pressure repeatedly pushes against tiny blood vessels throughout the body.
The blood vessels inside your eyes can be affected too.
The American Heart Association explains that uncontrolled high blood pressure can damage tiny vessels in the eyes. It can contribute to retinal blood-vessel damage, fluid accumulation beneath the retina and damage to the optic nerve. (www.heart.org)
An eye doctor may therefore notice vascular changes that raise concern about hypertension.
Again, however, there is an important distinction.
An eye examination doesn't replace having your blood pressure measured.
Instead, the eye may reveal evidence of what elevated blood pressure has been doing to your vascular system.
That is a very different — and fascinating — concept.
Can an Eye Doctor Really See Cholesterol?
This was one of the things that caught my attention during my appointment.
When someone says an eye doctor can "see cholesterol," we need to be careful about what that means.
Your Eye Exam Cannot Tell You Your LDL Number
An optometrist cannot examine your retina and say:
"Your LDL cholesterol is 92."
A blood test called a lipid panel is used to measure total cholesterol, LDL, HDL and triglycerides. (MedlinePlus)
So if an eye doctor tells you that they don't see concerning cholesterol-related changes, that is not the same thing as receiving normal cholesterol blood-test results.
But Cholesterol-Related Plaque Can Affect the Eye
This is where things become fascinating.
Atherosclerotic plaque can develop in major arteries such as the carotid arteries in the neck.
The American Heart Association explains that a central retinal artery occlusion — sometimes described as an eye stroke — can occur when plaque from a carotid artery breaks loose and travels into the circulation supplying the retina. (www.heart.org)
The same underlying vascular disease that threatens the eye may also increase the risk of a stroke involving the brain.
That means abnormalities involving retinal circulation can sometimes provide an important warning that warrants additional cardiovascular evaluation.
So when my eye doctor was reassuring me about what they were seeing, the medically careful way to interpret that is:
They weren't seeing obvious concerning vascular findings in the eye.
That's encouraging.
But it doesn't mean I should throw away my cholesterol blood-test results.
Your Eyes Can Even Reveal Clues About Stroke Risk
This one deserves special attention.
A central retinal artery occlusion, or CRAO, occurs when blood flow to the retina becomes blocked.
The American Heart Association considers obstruction of blood supply to the retina capable of producing retinal stroke, and sudden painless vision loss in one eye can be a medical emergency. (www.heart.org)
Risk factors that may require evaluation after a retinal artery occlusion include:
high blood pressure
high cholesterol
diabetes
obesity
sleep apnea
other cardiovascular risk factors
A sudden, painless loss of vision — especially in one eye — is therefore something people should not simply wait out to see if it gets better. It requires urgent medical evaluation. (www.heart.org)
That is a powerful reminder that our eyes and cardiovascular system are much more connected than many of us realize.
Can an Eye Exam Really Detect Cancer?
This statement also needs some context.
An eye examination cannot screen your entire body for cancer.
A completely normal retinal examination certainly doesn't mean:
"I don't have cancer anywhere."
But eye doctors really can sometimes discover tumors or abnormalities that ultimately lead to a cancer diagnosis.
Eye Cancer Can Be Found During Routine Exams
One example is intraocular, or uveal, melanoma.
The National Cancer Institute describes uveal melanoma as a rare cancer that develops inside the eye and notes that it may cause few or no early symptoms.
In fact, NCI states that intraocular melanoma is sometimes discovered during a regular eye examination when the pupil is dilated and the doctor examines the inside of the eye.
Eye doctors examining suspicious findings may evaluate areas including the:
iris
ciliary body
choroid
retina
optic nerve
Depending upon the abnormality, specialized imaging and additional evaluation may be necessary. (Cancer.gov)
So yes:
An ordinary eye examination can occasionally lead to the discovery of cancer.
But that is very different from saying an eye exam is a general cancer-screening test.
You should still follow recommended cancer screenings based on your age, sex, family history and personal medical history.
Your Optic Nerve Provides Another Window Into Your Health
There was something else fascinating in the picture of the back of my eye.
The optic nerve.
The retina detects light and sends information through the optic nerve toward the brain. Eye doctors therefore aren't simply looking at blood vessels during an examination; they're also examining a critical part of the visual nervous system. (National Eye Institute)
Changes in the appearance of the optic nerve can be important when evaluating diseases such as glaucoma.
The National Eye Institute recommends examining the retina and optic nerve as part of appropriate comprehensive eye evaluation because some serious eye diseases can develop before a patient notices obvious symptoms. (National Eye Institute)
That was another part of my appointment that made me realize how much more an eye exam involves than reading letters from an eye chart.
The Next Frontier: Artificial Intelligence Reading Your Retina
This may be the most futuristic part of the story.
Researchers are now studying whether artificial intelligence can identify patterns in retinal photographs that human beings might not easily recognize.
A major study published in Nature Biomedical Engineering trained deep-learning models using retinal images from 284,335 patients.
Researchers found that retinal photographs contained enough information for the algorithm to make predictions associated with factors including:
age
smoking status
systolic blood pressure
cardiovascular risk
The researchers found that the algorithms were paying particular attention to anatomical structures including retinal blood vessels and the optic disc. (Nature)
That doesn't mean your neighborhood eye doctor can currently photograph your eye and reliably diagnose every cardiovascular condition.
It doesn't.
But it demonstrates just how much biological information may be hidden inside an ordinary retinal photograph.
Researchers increasingly use the term oculomics for the study of biomarkers within eye images that may provide information about diseases elsewhere in the body.
The future may eventually involve combining retinal photographs, artificial intelligence, traditional medical history and laboratory tests to identify certain health risks earlier.
The science is still developing, but the possibilities are remarkable.
What a Normal Retinal Exam Does — and Does Not — Tell You
This is probably the most important takeaway from my entire experience.
If your optometrist examines the retina, blood vessels and optic nerve and says everything looks healthy, that's good news.
It means the doctor didn't see abnormalities that concerned them in the structures they examined.
But don't turn that reassuring result into something the test never claimed to prove.
A normal-looking retina does not prove that:
your LDL cholesterol is normal
your A1C is normal
you don't have cardiovascular disease
you don't have cancer
every blood vessel elsewhere in your body is healthy
Those conditions require their own appropriate medical screening and diagnostic tests. For example, cholesterol is measured with a blood lipid panel, while diabetes management relies on blood testing such as A1C. (MedlinePlus)
Think of the retinal examination as another piece of your health puzzle — not the entire puzzle.
Why This Matters for Families
At Family Finance Warriors, I spend a lot of time talking about protecting the family's finances.
But protecting a family also means protecting our health.
Preventive appointments can sometimes feel like another expense or another obligation on an already crowded calendar.
I went in because I needed glasses.
I walked out realizing that my optometrist had been looking at far more than whether I could read the bottom line of an eye chart.
The exam provided an opportunity to look at structures affected by diabetes, blood pressure, vascular disease and serious eye conditions.
The National Eye Institute notes that many eye diseases may have no symptoms or warning signs in their earlier stages, which is why comprehensive eye examinations can be so valuable. (National Eye Institute)
That's a pretty impressive amount of information to potentially gather during an appointment most of us associate with buying glasses.
Don't Skip the Basics Just Because Your Eyes Look Good
My experience also gave me a different perspective on preventive health.
If your eye doctor says your retinal vessels look healthy, celebrate that.
Then keep doing the basics.
Know your:
Blood pressure.
Blood sugar or A1C when appropriate.
LDL, HDL and triglycerides.
Keep up with recommended physical examinations.
Follow appropriate cancer-screening recommendations.
And don't ignore sudden changes in vision.
Your optometrist, primary-care doctor and other specialists aren't competing with one another.
They're looking at different pieces of the same person.
You.
The Family Finance Warriors Takeaway
I originally walked into Costco thinking about glasses.
I walked out thinking about my arteries.
That's probably the best way I can describe how surprising this experience was.
The retina gives medical professionals an extraordinary opportunity to examine tiny blood vessels and important nervous-system structures directly.
Those structures can show damage associated with diabetes and high blood pressure.
Vascular plaque can affect the retinal circulation. Certain eye cancers can occasionally be discovered during routine examinations. And researchers are now finding that artificial intelligence can extract even more information from retinal photographs than we previously realized. (National Eye Institute)
But the smartest lesson isn't:
"An eye exam can diagnose everything."
It's:
Your eyes may contain clues about your health that you never knew were there.
And that makes routine eye care worth taking seriously.
Related Family Finance Warriors Health Guides
If you're trying to become more proactive about your family's health, these three Family Finance Warriors articles complement this guide:
Quick-Reference Chart: What Can an Eye Exam Reveal?
Health Issue | What an Eye Doctor May See | Can the Eye Exam Diagnose It by Itself? | What Usually Confirms It? |
Diabetes | Retinal bleeding, leakage, blocked or abnormal vessels associated with diabetic retinopathy | No | Blood glucose/A1C + medical evaluation |
High Blood Pressure | Damage or changes involving tiny retinal vessels, retina or optic nerve | No | Blood-pressure measurements + medical evaluation |
High Cholesterol / Atherosclerosis | Vascular abnormalities or complications involving plaque/embolism in retinal circulation | No | Lipid blood panel and cardiovascular evaluation |
Retinal Artery Occlusion / Eye Stroke | Loss of retinal blood flow and characteristic retinal changes | Requires urgent medical evaluation | Ophthalmic and emergency cardiovascular/stroke evaluation |
Glaucoma | Changes involving the optic nerve, combined with eye pressure and other testing | Eye exams are central to diagnosis | Comprehensive ophthalmic testing |
Diabetic Retinopathy | Damaged, leaking, bleeding or abnormal retinal blood vessels | Yes, eye specialists diagnose it through appropriate eye evaluation | Dilated eye exam and additional retinal imaging when needed |
Uveal Melanoma / Eye Cancer | Suspicious tumor or abnormal tissue inside the eye | May be discovered during the exam; additional evaluation is required | Specialist examination and imaging |
Cancer Elsewhere in the Body | Occasionally an abnormal eye finding may prompt further investigation | No | Appropriate medical imaging, laboratory testing, biopsy or other cancer-specific testing |
General Cardiovascular Risk | Retinal-vessel patterns may provide clues; this is an active area of AI research | No | Blood pressure, cholesterol, diabetes testing, history and cardiovascular assessment |
Sources: National Eye Institute, National Cancer Institute, American Heart Association and published retinal-imaging research. (National Eye Institute)
About the Author
Manny Alfaro is the founder of Family Finance Warriors, a husband, father of two and United States Marine Corps veteran. Through Family Finance Warriors, Manny shares real-world research and practical strategies designed to help everyday families make smarter decisions about money, health and building a more secure future. (Family Finance Warriors)
This article is for educational and informational purposes only and is not medical advice. An eye examination can reveal important findings, but it does not replace medical examinations, laboratory testing or recommended cancer, cardiovascular or diabetes screening.
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