From what strength does an astigmatism have to be corrected?

There is no fixed limit, and that is not an evasion: what decides it is whether you notice anything. Almost every eye has a slight curvature, and the great majority of people notice nothing of it — then there is nothing to do either. It usually only becomes a nuisance when letters acquire shadows, when vision stays slightly blurred at every distance, or when headaches come in the evening. Children are the special case, and there the bar lies lower: if a higher curvature stays uncorrected in a child, the eye never gets a sharp image precisely during the time when vision is maturing — out of that weak sight (amblyopia) can develop, a lag that can only be made up to a limited extent once visual development ends at school age. Then there is what parents are rarely told: a child does not compare and does not report a weaker eye of its own accord, least of all when the other one sees well. That is why correction in children happens earlier and more consistently than in adults — and why an ophthalmic check at pre-school age makes sense even when nothing stands out.

Does an astigmatism get stronger over time?

In most adults it stays remarkably stable over years; what can shift slowly is the axis. The exception matters: if the cylinder increases markedly within a few months, if the axis moves from one measurement to the next, or if it affects mainly one eye in a young person, then that is not a normal course — then the shape of the cornea needs measuring. A new curvature after an injury, after an inflammation of the cornea or after a procedure on the eye also has a cause that one should know. A sudden change over days, by contrast, is almost never an astigmatism and needs examining promptly.

Why do lights pull rays at night — and does a correction improve it?

With an astigmatism a point of light is not imaged as a point but drawn out lengthwise. At night the pupil is wide, more light comes through the outer areas of the cornea, and the contrast between a bright headlight and dark surroundings is great — which is why what hardly bothers you by day stands out precisely then. A well-matched correction improves this markedly in most people. Starbursts and glare do not always disappear completely with it, because the tear film, a lens that is beginning to cloud and pupil width all play a part as well. If glare when driving at night is your main problem, please tell us that at the appointment — then we look more specifically. One distinction belongs at this point, even though it rarely applies: coloured rings or halos around lights together with eye pain or headache, nausea, a red eye or foggy vision are not astigmatism. Behind that can lie an acute rise in pressure inside the eye, and that needs examining immediately — not at the next free appointment and not the following morning.

Can you wear contact lenses with an astigmatism?

Yes. For a regular astigmatism there are soft toric lenses which, by the way they are built, do not slip in the eye but hold their axis. With higher values and with an irregular cornea, rigid lenses are the more reliable solution, because a tear film forms beneath them that evens out the irregularities. Fitting toric lenses takes longer than fitting ordinary ones, and it needs follow-up appointments — that belongs to the thing and is no sign that something is not working. Hygiene stays non-negotiable: clean hands, wearing times kept to, fresh cleaning solution. A red, painful or light-shy eye with a lens in always means: lens out and call the same day.

What is the difference between an astigmatism and a keratoconus?

An ordinary astigmatism is a build: the cornea is more strongly curved in one axis than in the other, but it stays regularly shaped and largely stable over the years. A keratoconus is a disease of the cornea in which it becomes thinner and bulges forward; the curvature becomes irregular as a result and increases. The difference cannot be read off the spectacle value but off the shape: a spectacle value is a number, the corneal surface is a map. That is why with increasing or unusual values we measure the topography instead of simply prescribing a new lens.

Why does a new pair of glasses with a cylinder feel so strange at first?

Because a cylindrical lens does not only make the image sharper but also distorts it slightly in one direction. Anyone getting a cylinder for the first time, or whose axis has changed, often reports sloping floors, tilted door frames or the feeling of holding their head wrongly. The brain computes this distortion out, in most people within a few days, in some over a few weeks. Wear the glasses continuously during this time — wearing them on and off tends to prolong getting used to them rather than make it easier. If it stays uncomfortable afterwards, that is a reason for a check and not for persevering: sometimes the axis is not right, sometimes the centring of the lens.

Can astigmatism be trained away?

No. Eye exercises do not change the shape of the cornea — it is tissue, not a muscle, and its curvature cannot be influenced by will. What exercises can bring about is a certain habituation to a blurred image; the measured curvature stays the same. Nor does it help to leave the glasses off 'so that the eyes have to work again'. And one point that matters more than all the exercises: rubbing the eyes vigorously is not a treatment but a mechanical load on the cornea — anyone who rubs constantly should have the cause assessed rather than putting up with it.

Refractive errors

Astigmatism laser surgery, lenses or glasses — what really matters

Letters with shadows, lights that pull rays at night, and a pair of glasses that never seems quite right: an astigmatism is often behind it. The question we are asked about it most often is 'can astigmatism be lasered?' — and the honest answer has two parts. Yes, a regular astigmatism can be corrected with the laser. And no, we do not do it ourselves: we measure, we tell you whether you are a candidate for it at all, and we correct with what lies in our own hands — a spectacle lens, a toric contact lens and, when the lens is being replaced anyway, a toric artificial lens.

Book an appointment — have your cornea measured Prefer to phone? Call now

What an astigmatism is

The cornea is the clear window right at the front of the eye and at the same time its strongest lens. If it is curved equally in all directions — like a section cut from a sphere — it brings the light together at a single point. If it is more strongly curved in one axis than in the axis across it, no point forms any more but a stretched-out area instead. A point of light is then imaged as a short line, letters acquire shadows, and the image stays a little restless at every distance.

The medical name for it is astigmatism — from the Greek, literally 'without a point'. German also once used the word Stabsichtigkeit (rod-sightedness), after exactly that little rod the point turns into. Curvature of the cornea, astigmatism and Stabsichtigkeit mean the same thing; one term appears in the medical report, the other comes up in conversation.

On your glasses prescription you find them as two entries: the cylinder in dioptres, which says how large the difference between the two axes is, and the axis in degrees from 0 to 180, which says where that difference lies. The two numbers belong together — the right power on the wrong axis does not correct anything.

Two things here are more important than they sound. Firstly: a slight curvature is present in almost every eye, and it is of no significance. A finding is not yet a complaint. Secondly: unlike short-sightedness, where only distance vision goes blurred, an astigmatism bothers you at every distance. That is also why it does not help to pull the book closer or to hold it further away.

An astigmatism usually does not come alone. The combination with short- or long-sightedness is the normal case, and from about the age of forty-five presbyopia settles over both. How these forms interact and where they differ is set out in the overview of the four forms of refractive error.

Symptoms: distorted vision, shadows, rays around lights

Most people do not come to us with the word 'astigmatism' but with one of these descriptions:

Distorted or slightly blurred vision — and that applies close up as much as at a distance, not only at one distance
Letters with shadows or double contours, digits mixed up, a text that cannot quite be 'pinned down'
Starbursts and halos around lights at dusk, glare from oncoming headlights when driving at night
Screwing up the eyes, to get a sharper image through the narrower lid opening
Headaches and burning eyes in the afternoon, particularly after screen work — the effort of constantly re-sharpening a blurred image
In children: going very close to a book or the blackboard, screwing up the eyes, a tilted head position, tiring quickly over homework and avoiding tasks close up

Two things about this that are regularly confused. Reversed letters and reading difficulties are not in themselves a sign of an astigmatism — they are the hallmark of dyslexia, and neither glasses nor vision training treat that. Have the eyes checked all the same, so that a refractive error is not missed; reading performance should be assessed separately from that and without losing time, because support works most readily in these years. And the second point: a child does not compare. An eye that sees worse than the other does not report it — which is why an ophthalmic check at pre-school age even when nothing stands out makes sense.

What is not part of an astigmatism: a deterioration in vision that appears within days; straight lines that suddenly look bent, or a grey patch in the middle of the image; pain; a red eye. And one combination that is often taken for 'my astigmatism': coloured rings around lights together with eye pain or headache, nausea, a red eye or foggy vision are not astigmatism. Behind that can lie an acute rise in pressure inside the eye, and that needs examining immediately, not at the next appointment. These signs all point to something else, and none of them becomes clearer by waiting.

Regular or irregular — the distinction on which everything hangs

For the consultation no question is as decisive as this one. It determines whether glasses can correct completely at all, which contact lens is an option, and whether a laser procedure is an option or expressly not.

Regular astigmatism

The common case: the cornea has two principal meridians at right angles to one another — a flatter and a steeper one — and between them the curvature changes evenly. You can picture the surface like the back of a spoon: curved differently along its length than across its width, but even and without dents. This shape can be compensated for completely with a cylindrical spectacle lens. A toric contact lens comes very close to that, as long as it holds its axis reliably, and a toric artificial lens takes most of the cylinder with it at a cataract operation — a small remainder can stay behind, more on that below.

A regular astigmatism is usually congenital and stays stable over years. What shifts slowly in many people over the course of life is the position of the steeper axis — an unhurried process over decades, not a disease, but a reason to have the values determined afresh every few years instead of carrying the old prescription forward.

Irregular astigmatism

Here there are no longer two clean principal meridians. The surface is unevenly shaped, often asymmetrical, and the light is scattered in several directions at once. The consequence is vision that cannot be brought fully into focus with any pair of glasses: it gets better, but never entirely good, and ghost images remain even when you cover one eye.

Causes are scars after an injury or after an inflammation of the cornea that has healed with scarring, changes following earlier procedures on the eye, a pterygium that grows onto the cornea from the corner of the lid and distorts it — and, as the most common cause in young people, a keratoconus. Because glasses reach their limit here, rigid contact lenses are the usual route: a tear film forms beneath them that evens out the irregularities, so that the smooth lens surface takes over the refraction. Refractive laser methods are as a rule not indicated with an irregular cornea.

Does the curvature sit in the cornea or in the lens?

Mostly in the cornea — it supplies the greater part of the eye's refractive power, and its shape can be measured from outside. A smaller part can come from the lens inside the eye. For everyday life that makes no difference, for two decisions it does: a toric artificial lens compensates for the curvature of the cornea, not the earlier curvature of your own lens — and when spectacle values change rapidly in middle age without the corneal shape changing, sometimes a beginning clouding of the lens (cataract) is the explanation.

When an astigmatism points to a keratoconus

The most common misjudgement on this subject is at the same time the most consequential: an increasing astigmatism is treated as 'a curvature that has simply got stronger' and answered with a new lens. In most cases that is right. In some it is the first visible sign of a disease of the cornea.

We look more closely at this combination:

The cylinder increases and the axis moves — from one measurement to the next, over months instead of over decades
Young age — the change typically begins in adolescence or in early adulthood
A marked difference between the two eyes, with no recognisable cause
Ghost images that remain when you cover one eye, together with pronounced glare and starbursts
Frequent, vigorous eye rubbing in the history, usually with an allergy

What answers this question is not another refraction but a measurement of the corneal shape. A spectacle value says which lens makes the image sharpest; the topography says why the value changes at all. Everything else — the course, the diagnosis and the treatment routes that exist for it — is on its own page: Keratoconus — when the cornea loses its shape.

One more sentence, which at this point is worth more than any reassurance: the great majority of astigmatisms are exactly that and nothing else. We do not write this section in order to cause worry but because the distinction can be made with a measurement of a few seconds — and because it has to be made before any decision about a laser procedure in any case.

How we measure an astigmatism

Establishing a curvature is simple. Judging whether it explains your symptoms, whether it is regular and whether it is changing is the actual work. That includes:

refraction — first objectively by machine, then checked against your own impression; this is where the cylinder and the axis come from. How that works in detail is set out under Eye test. In children and adolescents we also measure, where the question calls for it, after giving eye drops that switch off focusing at near for a time — the so-called cycloplegic refraction. Without this step the strong focusing of young eyes joins in during the measurement and hides part of the values; the prescription would then come out too weak.
Keratometry — the measurement of the curvature at the centre of the cornea, in seconds and without touching the eye.
Corneal topography — a measurement of the entire surface, presented as a colour map. It is the step that separates regular from irregular, and therefore the most important one where the readings are increasing. How it works and which other examinations can belong with it is set out under Corneal topography and the other eye examinations.
Slit-lamp examination — cornea, tear film, lens. This is where it shows whether a scar, a growth or a clouding is involved.
Assessment of the tear film — an unstable tear film breaks up between two blinks and in doing so does exactly what an irregular astigmatism does. Anyone who complains of fluctuating sharpness that improves briefly after blinking often has dry eyes with an unstable tear film and not necessarily a corneal problem.

What is not necessary: Not every astigmatism needs a topography. A small cylinder that has been unchanged for years, in eyes free of symptoms, is adequately assessed with a refraction and a look at the slit lamp. And nobody has to buy a new pair of glasses every year because 'the values need re-measuring' — if you see well and the values are stable, the result of the measurement is: no change.

The topography does become necessary with increasing or unusual values, when fitting rigid contact lenses, at any suspicion of a corneal disease, before a cataract operation with a toric artificial lens, and before any assessment of whether a laser procedure is an option.

Routes to correction: glasses, toric contact lenses, toric artificial lens

Three routes are available for an astigmatism without a refractive procedure being needed — and for the great majority of people the first one is already enough.

Glasses with a cylindrical lens

A cylindrical lens refracts the light more strongly in one axis than in the other and so compensates for exactly what the cornea does. It corrects a regular astigmatism completely, can be changed at any time and puts no load on the ocular surface. Short- or long-sightedness is corrected in the same lens; a long-sightedness that has long been compensated for by effort sometimes only comes to light in the process.

The only reliable drawback is getting used to it. A new cylinder, or one whose axis has changed, distorts the image in one direction, and the brain usually needs a few days for that, sometimes a few weeks: floors look sloped, door frames tilted. Wear the glasses continuously during this time. If it stays uncomfortable, come back — then it is often the axis or the centring that is not right, and not your patience.

Toric contact lenses

An ordinary soft lens rotates in the eye; for a cylinder that is useless, because the axis then does not stay put. Toric lenses are therefore built differently — with a ballast or with flattened zones at the edge — so that blinking turns them back into the same position again and again. They give an image at natural size, a wide field of view and do not get in the way during sport.

The price for that is effort: fitting takes longer than with spherical lenses and needs follow-up appointments, because the fit and the rotation have to be assessed. Then there is hygiene, which is not negotiable — clean hands, wearing times kept to, fresh cleaning solution, no lens in an irritated eye. Every contact lens carries a risk of corneal inflammation, and that can permanently impair vision. Anyone prone to dry eyes often tolerates toric lenses less well in the evening than in the morning.

Toric artificial lens at a cataract operation

If your own lens is being replaced anyway, the astigmatism can be taken into account during that procedure: a toric artificial lens carries the cylinder within it and is inserted on the matching axis. The requirements are a regular cornea, a careful measurement of shape and axial length, and planning that brings the two together. What the procedure itself involves and how it works is set out under Cataract treatment — how the procedure works and choosing the artificial lens. Whether a toric lens is an option for you is decided not there but on your measurements.

Two things belong with this so that the expectation is right. Firstly: a special lens is an extra cost, not a component of basic health insurance — more on that below. Secondly: even after very good planning a small residual cylinder sometimes remains, which makes glasses worthwhile for particular tasks. Anyone who reckons with that is more satisfied afterwards than someone who does not.

Lasering astigmatism: what happens, and who is a candidate

Lasering changes the shape of the cornea: tissue is removed at precisely calculated points, so that the steeper and the flatter principal meridian end up refracting equally. Depending on the technique this happens directly at the surface (the names PRK and LASEK come up for this in conversation), under a thin flap folded back briefly (LASIK, femto-LASIK), or by taking out a small disc of tissue from inside the cornea (lenticule extraction). The cylinder is corrected together with an existing short- or long-sightedness — an astigmatism on its own is rarely the only reason for a procedure.

What has to be settled before the decision

Whether a procedure is possible and sensible is decided not by the wish but by the findings. What is examined includes:

Stability of the values — fluctuating or increasing values are not operated away, they are explained first
Shape and thickness of the cornea — enough load-bearing tissue must remain after the tissue is removed, and the topography must be regular
No sign of a keratoconus — nor an early form that is still free of symptoms; in that situation removing tissue is expressly not indicated, because it weakens the cornea further. How that is recognised is set out under Keratoconus: signs, course and what can be done about it.
Tear film and ocular surface — dry eyes usually get temporarily worse after a procedure, in some people for months
Retinal findings, intraocular pressure, lens — a procedure on the cornea changes nothing about what lies behind it

If one of these points argues against removing tissue, that does not take everything off the table — it depends which one. With a cornea that is regularly shaped but too thin for tissue to be removed, the lens rather than the cornea can be the point of attack: a toric lens that is placed in the eye in addition to your own — a phakic intraocular lens. Whether that makes sense in your case at all depends among other things on the space available in the front section of the eye and is a question for the examination, not for the wish. With a keratoconus or an irregular cornea it is expressly no substitute: there it is first about the corneal disease itself and about rigid contact lenses. These procedures too we do not carry out ourselves — we measure, we put it in context and we pass you on to a centre that offers them.

What a laser procedure does not achieve

These points rarely appear in advertising, but they belong before the decision and not after it. A procedure changes the refractive power of the cornea — it treats no disease, and it does not stop presbyopia: reading glasses come from the mid-forties all the same. Glare and starbursts at dusk can persist or appear anew in the first months. A residual cylinder is possible, as is a corrective procedure. And freedom from glasses cannot be promised to anyone — whoever promises you that has not measured your cornea.

One complication expressly belongs on this page, because the whole text hangs on the stability of the cornea: if too little load-bearing tissue remains after the tissue is removed — or if the shape was not entirely regular beforehand — the cornea can bulge forward over time and lose its shape. The technical term for that is keratectasia, and the result resembles what a keratoconus does. It is rare. But it is the reason that before such a procedure the topography and the corneal thickness count, and not the calendar.

Our role — and what it expressly is not

Refractive laser surgery we do not carry out ourselves at Sehklinik. That is the reason we can talk about this subject differently from somewhere that sells the procedure. What happens here is: the complete examination including measurement of the corneal shape, the judgement of whether you are a candidate for such a method — with no commercial interest behind it —, a clear word when we advise against it, the referral to a centre that carries out the procedure if you decide on it, and the ophthalmic check afterwards.

The other part is just as clear: for correction with a spectacle lens, with toric contact lenses and with a toric artificial lens at a cataract operation, you are in the right place with us. The difference between 'we correct' and 'we advise and pass on' runs exactly along this line, and we would rather draw it ourselves than let you discover it later.

What does not help against an astigmatism

A fair amount is offered around this subject. These things do not stand up to scrutiny, and we would rather say so plainly:

Eye training and vision exercises. The curvature of the cornea cannot be influenced by will. Exercises can change how used you are to a blurred image, but not the measured readings.
Leaving the glasses off 'for practice'. The eye is not straining itself in the process, it simply sees worse. In children it is harmful as well, because vision does not develop properly on a permanently blurred image.
Vigorous eye rubbing. It relieves briefly and puts mechanical load on the cornea. Anyone who rubs constantly usually has a reason for it — an allergy, dry eyes, inflammation of the eyelid margin —, and that reason needs treating.
Food supplements. No preparation changes the shape of the cornea.
A new pair of glasses every year 'to be safe'. With stable readings and good vision, no change is the expected result of a measurement and no reason for new lenses.
Correcting every small curvature. A small cylinder without symptoms needs no lenses. What is treated is what bothers you — not what is on the printout.

And one worry we often hear we can take from you — for adults: an astigmatism is not a disease of the eye, in the adult eye it does not on its own lead to blindness, and it does not get stronger from screen work. The one restriction concerns children: there an uncorrected higher curvature is indeed consequential — not as blindness, but as weak sight (amblyopia) that can only be made up to a limited extent once visual development is complete. What screen work actually does is strain the tear film — and so make the symptoms an uncorrected curvature causes anyway more noticeable in the evening.

Immediately, not tomorrow: sudden loss of vision, severe eye pain with nausea or coloured rings around lights, a red, painful eye under contact lenses. During consultation hours, call us — +41 44 500 69 00; outside those, the ophthalmic emergency service applies, or you go directly to the emergency department of an eye clinic.
Call the same day if you have new flashes of light, a sudden swarm of black dots or a shower of floaters, a shadow from the side, straight lines that suddenly look distorted, a grey patch in the middle of the image or rapidly worsening vision: +41 44 500 69 00. These signs weigh all the more heavily when a short-sightedness is added to the astigmatism — the normal case described on this page. An astigmatism itself changes over years, not overnight: what comes suddenly has another cause.

Where to find us

Measurement, advice and monitoring for an astigmatism we offer at all three locations. You will find an overview with directions and opening hours under Locations.

Sehklinik Zürich

Hallenstrasse 8, 8008 Zürich
Phone: +41 44 422 25 55
Mon–Fri 08:00–12:00 / 13:00–17:30
Tram 11/15 to 'Zürich, Kreuzplatz', three minutes on foot — Getting here and details

Sehklinik Wetzikon

Bahnhofstrasse 126, 8620 Wetzikon
Phone: +41 44 930 61 00
Mon–Fri 08:00–12:00 / 13:00–17:30
Bus 850/851/852 to 'Wetzikon ZH, Schloss', one minute on foot — Getting here and details

Sehklinik Meilen

Dorfstrasse 94, 8706 Meilen
Phone: +41 44 923 03 81
Mon, Tue, Thu, Fri 08:00–12:00 / 13:00–17:30; Wednesday varies, please ask by phone
S6/S7 to Meilen station, two minutes on foot — Getting here and details

Outside consulting hours the ophthalmic emergency service applies. If you would rather write than phone, you can reach us through the contact form; referring colleagues will find the details they need under Referring physicians.

Costs & health insurance

What does the insurer pay for — and what not?

With astigmatism, basic health insurance separates the same two things as with any refractive error: the medical assessment of a finding is treatment of illness. The aid with which you then see sharply is, in adults, as a rule not. What applies in your case we tell you before the examination — not with the invoice.

Service	Coverage	What this means for you
Ophthalmic assessment for distorted or worsening vision	Basic insurance (OKP)	Where there is a medical indication — distorted vision, rapidly changing readings, glare, symptoms or a noticeable finding. Your deductible and co-payment apply as at any doctor's appointment. For children and adolescents there is as a rule no deductible; the co-payment is capped lower than for adults.
Corneal topography for a medical question	Basic insurance (OKP)	Where a corneal disease is suspected, with an irregular cornea, when fitting rigid lenses for a medical reason, and in planning a cataract operation. The same measurement as part of a suitability assessment for a refractive procedure, by contrast, is billed privately — it is the question being asked that counts, not the device.
Glasses: cylindrical lenses and frame	Self-pay service	In adults, basic health insurance as a rule does not pay for glasses. For children and for certain medical situations there are special rules; some supplementary insurance policies make a contribution. Ask your health insurer beforehand, not afterwards.
Toric contact lenses and fitting them	Self-pay service	Fitting and materials you as a rule pay for yourself. With particular medical findings — an irregular cornea, for instance, or the state after procedures on the cornea — a contribution to the cost can be examined. That needs a medical justification and a request to your insurer before the fitting.
Cataract operation with a toric artificial lens	Basic health insurance, special lenses at extra cost	Where there is a medical indication, the procedure is a mandatory benefit. A toric lens that also corrects the astigmatism goes beyond that; the difference and the additional examinations that go with it you pay yourself. What that means in your case we set out for you before the procedure.
Suitability assessment for a planned laser procedure	Self-pay service	The examination that establishes whether you are suitable for a procedure to replace your glasses does not treat any illness and is therefore billed privately. We tell you the extent of it beforehand. If the assessment shows a finding that needs treatment, that part is billed as what it is.
Refractive laser surgery to correct astigmatism	Self-pay service	A procedure whose purpose is to make a visual aid unnecessary is not a mandatory benefit of basic health insurance. Some supplementary insurance policies contribute a share, often tied to conditions — obtain the agreement in writing before an appointment is fixed. This procedure we do not carry out ourselves; we examine, we advise and we check you afterwards.

Not sure which category your concern falls into? Call us — +41 44 500 69 00. We tell you on the phone what to expect, and with that same information you check with your health insurer. An invoice that comes as a surprise is an avoidable annoyance.

Related conditions

Keratoconus Refractive errors Eye examinations

Medically reviewed by PD Dr. med. Andrea von Rückmann

Your ophthalmologistPD Dr. med. Andrea von RückmannView profile

Frequently asked questions

: A regular astigmatism can in many cases be corrected with the laser; the cornea is reshaped so that its two principal meridians refract equally. Whether that is possible and sensible in your case depends on several things: on the size of the cylinder, on the thickness and the shape of the cornea, on the quality of the tear film, on age, and on whether the values have been stable for some time. With an irregular cornea and where a keratoconus is suspected, such a procedure is expressly not indicated. Refractive laser surgery we do not carry out ourselves at Sehklinik. What we do take on is the complete preliminary examination, a judgement with no commercial interest behind it, the referral to a centre that carries out the procedure, and the ophthalmic check afterwards.
: There is no fixed limit, and that is not an evasion: what decides it is whether you notice anything. Almost every eye has a slight curvature, and the great majority of people notice nothing of it — then there is nothing to do either. It usually only becomes a nuisance when letters acquire shadows, when vision stays slightly blurred at every distance, or when headaches come in the evening. Children are the special case, and there the bar lies lower: if a higher curvature stays uncorrected in a child, the eye never gets a sharp image precisely during the time when vision is maturing — out of that weak sight (amblyopia) can develop, a lag that can only be made up to a limited extent once visual development ends at school age. Then there is what parents are rarely told: a child does not compare and does not report a weaker eye of its own accord, least of all when the other one sees well. That is why correction in children happens earlier and more consistently than in adults — and why an ophthalmic check at pre-school age makes sense even when nothing stands out.
: In most adults it stays remarkably stable over years; what can shift slowly is the axis. The exception matters: if the cylinder increases markedly within a few months, if the axis moves from one measurement to the next, or if it affects mainly one eye in a young person, then that is not a normal course — then the shape of the cornea needs measuring. A new curvature after an injury, after an inflammation of the cornea or after a procedure on the eye also has a cause that one should know. A sudden change over days, by contrast, is almost never an astigmatism and needs examining promptly.
: With an astigmatism a point of light is not imaged as a point but drawn out lengthwise. At night the pupil is wide, more light comes through the outer areas of the cornea, and the contrast between a bright headlight and dark surroundings is great — which is why what hardly bothers you by day stands out precisely then. A well-matched correction improves this markedly in most people. Starbursts and glare do not always disappear completely with it, because the tear film, a lens that is beginning to cloud and pupil width all play a part as well. If glare when driving at night is your main problem, please tell us that at the appointment — then we look more specifically. One distinction belongs at this point, even though it rarely applies: coloured rings or halos around lights together with eye pain or headache, nausea, a red eye or foggy vision are not astigmatism. Behind that can lie an acute rise in pressure inside the eye, and that needs examining immediately — not at the next free appointment and not the following morning.
: Yes. For a regular astigmatism there are soft toric lenses which, by the way they are built, do not slip in the eye but hold their axis. With higher values and with an irregular cornea, rigid lenses are the more reliable solution, because a tear film forms beneath them that evens out the irregularities. Fitting toric lenses takes longer than fitting ordinary ones, and it needs follow-up appointments — that belongs to the thing and is no sign that something is not working. Hygiene stays non-negotiable: clean hands, wearing times kept to, fresh cleaning solution. A red, painful or light-shy eye with a lens in always means: lens out and call the same day.
: An ordinary astigmatism is a build: the cornea is more strongly curved in one axis than in the other, but it stays regularly shaped and largely stable over the years. A keratoconus is a disease of the cornea in which it becomes thinner and bulges forward; the curvature becomes irregular as a result and increases. The difference cannot be read off the spectacle value but off the shape: a spectacle value is a number, the corneal surface is a map. That is why with increasing or unusual values we measure the topography instead of simply prescribing a new lens.
: Because a cylindrical lens does not only make the image sharper but also distorts it slightly in one direction. Anyone getting a cylinder for the first time, or whose axis has changed, often reports sloping floors, tilted door frames or the feeling of holding their head wrongly. The brain computes this distortion out, in most people within a few days, in some over a few weeks. Wear the glasses continuously during this time — wearing them on and off tends to prolong getting used to them rather than make it easier. If it stays uncomfortable afterwards, that is a reason for a check and not for persevering: sometimes the axis is not right, sometimes the centring of the lens.
: No. Eye exercises do not change the shape of the cornea — it is tissue, not a muscle, and its curvature cannot be influenced by will. What exercises can bring about is a certain habituation to a blurred image; the measured curvature stays the same. Nor does it help to leave the glasses off 'so that the eyes have to work again'. And one point that matters more than all the exercises: rubbing the eyes vigorously is not a treatment but a mechanical load on the cornea — anyone who rubs constantly should have the cause assessed rather than putting up with it.

Measure first, then decide.

Whether your symptoms really come from the astigmatism, whether the value has changed and which route to correction suits your everyday life — that is settled by an examination, not by a guess. Call us; we will tell you what makes sense and what does not.

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