Headaches from contact lenses are nearly always a focusing problem, not a comfort problem. Your eye muscles are compensating for something slightly wrong, and the strain shows up as a headache hours later — usually behind the eyes, across the brow, or at the temples.
The most likely cause: the power is slightly off
Not dramatically wrong — if it were, you would notice blur immediately. Slightly wrong is worse, because your focusing system can compensate for it, and compensating all day is what produces the ache.
Two specific versions:
Over-correction. A minus lens that is a quarter or half dioptre too strong forces you to focus continuously just to see clearly at distance. This is the single most common cause and the easiest to fix.
Vertex compensation missed. Above roughly ±4.00 dioptres, the contact lens power should differ from the spectacle power, because the lens sits on the eye rather than 12 mm in front of it. If the spectacle number was copied straight across, you are over-corrected by design. See how to read your prescription and why the two differ.
Uncorrected astigmatism
A low cylinder — 0.75, say — often gets left out of a spherical lens because the vision seems acceptable.
It is acceptable for an hour. Over a full day your visual system keeps trying to resolve an image that will not quite come into focus, and that effort has a cost. If your headache builds through the afternoon and you have astigmatism on your glasses prescription but not your contacts, that is a strong lead. See toric lenses.
If you are over 40
Presbyopia produces exactly this pattern: fine in the morning, brow ache by evening, worse after reading or screen work.
Distance-only contacts leave your near focusing to do all the work unaided. Options are multifocals, monovision, or readers over your contacts. See lenses for presbyopia.
Screens make everything above worse
Not a separate cause so much as an amplifier. Sustained near work drops your blink rate by roughly half and holds your focusing system at a fixed close distance for hours.
Two things help independently of the lens: the 20-20-20 rule (every 20 minutes, look 20 feet away for 20 seconds) and deliberately blinking fully. See lenses for screen work.
Causes that are not about focus
- A too-tight lens. A base curve that is too steep grips the eye and can produce a dull ache around it. It may feel comfortable otherwise, which is why this one gets missed.
- Dryness. Straining to see through a drying lens is its own low-grade effort — see dry eyes.
- Swapped lenses. Worth ruling out in ten seconds if your two eyes have different powers.
- The lenses are coincidental. Dehydration, caffeine, sleep, posture and screen time all cause headaches in people who happen to wear contacts.
How to narrow it down yourself
Two tests that tell you most of what you need:
- Wear glasses for three days. If the headaches stop, it is the lenses. If they continue, it is not.
- Note the timing. Morning headaches point away from lenses. Headaches that build through the day and ease within an hour of removal point straight at them.
Take both answers to your appointment. “It starts around 2pm and goes twenty minutes after I take them out” is far more useful than “my contacts give me headaches,” and it usually shortens the diagnosis to one visit.
When a headache is not an eye problem
Seek medical attention promptly for a headache that is sudden and severe, comes with vision loss, double vision, a droopy eyelid, an unequal pupil, nausea or vomiting, or that wakes you from sleep. Those patterns are not about your contact lenses.
General information, not a substitute for clinical care. Reviewed by Dr. Teresita Bollar, OD.
