Using a mobile phone in the dark, cold medicine, and acute glaucoma: triggers, intraocular pressure, and treatment sequence

Glaucoma is often called a "vision thief" because it steals vision almost silently. Acute angle-closure glaucoma is called a "vision robber" because it can push intraocular pressure to dangerous levels in a very short time.

But what truly causes Hong Kong people to delay seeking medical treatment is often not how vicious the "robber" is, but rather...It will stop by itselfThe Department of Health's Drug Office clearly states that the symptoms of acute angle-closure glaucoma are unstable and can last for one or two hours before disappearing again—but each time symptoms appear, vision is impaired more. As a result, many people, after experiencing a round of pain and seeing it subside, mistake it for a migraine or gastrointestinal discomfort, thus wasting the most crucial few hours.

This article focuses on acute angle-closure cataracts: why they occur (dark environment and medication, not calendar), how high the intraocular pressure is during an attack, how to distinguish them from migraines, the order of treatment after arriving at the emergency room, and the most practical question: "Can cataract surgery be performed at the same time?"

Your situation	suggestion
After using your eyes in a dimly lit environment, you may experience eye strain, seeing rainbow halos around lights, and experiencing headaches or nausea.	Seek immediate medical attention or go to the emergency room.Don't wait for it to retreat on its own.
I experienced the pain once, but it subsided on its own after an hour or two.	You should still see an ophthalmologist as soon as possible—this is the most typical, yet most easily overlooked, symptom.
Those with farsightedness, short eyeballs, or who have been told they have a narrow anterior chamber angle may be at risk.	Regular eye exams are recommended, along with anterior chamber angle assessments.
I am considered a high-risk individual and am planning to buy cold and flu medicine, allergy medication, or motion sickness medication on my own.	Ask a doctor or pharmacist first.
I have been diagnosed with glaucoma and am currently using eye drops to lower my intraocular pressure.	Take your medication on time and have regular follow-up appointments; do not stop or reduce your medication on your own.
Headache, vomiting, and blurred vision occurred simultaneously	First consider the issue of intraocular pressure; don't just treat it as gastroenteritis or a migraine.

I. Chronic and Acute: Two Completely Different Rhythms

"Glaucomatus" is a general term, which can be divided into at least two completely different categories. Mixing them up is a source of many misunderstandings.

	Chronic (mainly open-angle type)	Acute (mainly angle-closure type)
Progress speed	Several years to several decades	Hours to days
Symptoms	Initially, there was almost nothing; the surrounding view narrowed first, like a tunnel.	Severe pain in one eye, redness, blurred vision, halos around lights, headache, nausea and vomiting
Timing of seeking medical treatment	It is often discovered during an eye exam or at a later stage.	This is an ophthalmic emergency and requires immediate treatment.
Typical background	High myopia, high intraocular pressure, family history, diabetes, hypertension	Farsightedness, small eyeballs, shallow anterior chamber, female, older

One point needs correction. It's commonly said that "chronic glaucoma includes open-angle, primary, and secondary types," but this conflates two different classification axes. In reality:

• Angle axis—Whether the drainage channels for aqueous humor are open or closed, depending on...Open angle type與Closed angle；
• Etiological axis—Are there any other reasons for the division?Primary與Secondary。

Therefore, the correct combination is "primary open-angle glaucoma," "primary angle-closure glaucoma," and "secondary glaucoma," not listing "open-angle, primary, and secondary" as three separate conditions. Secondary glaucoma can result from eye injuries, uveitis, tumors, advanced cataracts, diabetes, or long-term use of corticosteroids—this is a crucial point.Department of Health Drug OfficeIt's written very clearly.

It's also important to note that both open-angle and closed-angle types can be acute or chronic. Closed-angle type isn't necessarily "acute"; there are also chronic closed-angle types. It's only when the angle of the anterior chamber is suddenly and completely blocked that an acute attack that breaks out within a few hours occurs.

II. How high is intraocular pressure during an attack? Three sets of real data.

The reference range for intraocular pressure in the general population is: 10 to 21 mmHg(mmHg)Information from the Hong Kong Eye OrganizationThis is also the number. Measurement results can be affected by corneal thickness, measurement time, instrument, and posture, so a single reading is not the whole picture.

So how high does it rise during an attack? Three cohort studies from different regions provide fairly consistent answers:

Research	Region and Year	Number of examples	Average intraocular pressure at the time of visit
Hong Kong queue	Hong Kong, 1999-2009	40 eyes	49.2 ± 14.0 mmHg
Scotland Foresight	Scotland, 2011-2012	114 cases	52 mmHg(Standard deviation 11)
Japan Single Center	Japan, 2009 to 2025	229 eyes	53.2 ± 15.4 mmHg

In other words, while the statement "from a normal 10 to 21, suddenly jumping to 40 to 60" is correct in its direction, a more accurate way to put it is:The average blood pressure during an acute attack is around 50 mmHg.That is, more than twice the normal upper limit; in some cases it can be even higher.

As an aside, some reports describe intraocular pressure as "10 to 21 degrees," which is a colloquial abbreviation; the formal unit is millimeters of mercury (mmHg). It is not advisable to write "degrees" when writing medical records and prescriptions to avoid confusion with visual acuity.

Third, anterior chamber angle closure is a consequence, not the only cause.

Many people believe that acute glaucoma is simply "the sudden closing of the anterior chamber angle." This description is only half correct: angle closure is...resultThere are several mechanisms that drive it to shut down.

A study examining 72 acutely ill eyes using ultrasound biomicroscopy (PMID 27770479The most prominent mechanism distribution was found to be:

mechanism	Proportion	What does it mean?
Iris lens crowding	68.1%	The iris is pushed forward by the relatively large lens, and the angle of the anterior chamber is narrowed.
Pupillary block	23.6%	Aqueous humor trapped behind the iris pushes the iris forward.
High-fold iris	8.3%	The iris root is positioned anteriorly, and the anterior chamber angle is already shallow.

Why talk about this? Because it directly affects treatment options. Laser iridotomy addresses the "pupil block" aspect; if the main problem is an oversized lens that pushes the entire iris forward, laser treatment alone may not be sufficient—this is precisely why "lens removal" has been included in discussions in recent years.

IV. Trigger 1: Dark environment and dilated pupils

When there is insufficient light, the pupil naturally dilates to increase the amount of light entering the eye. As the pupil dilates, the peripheral iris overlaps in the center, making the already narrow anterior chamber angle even narrower, making it more difficult for aqueous humor to drain, and thus increasing intraocular pressure. For people with a pre-existing narrow anterior chamber angle, this step is enough to trigger an acute attack.

That's what the official documents say too.When describing the symptoms of acute angle-closure glaucoma, the Department of Health's Drug Office specifically noted visual disturbances.It usually occurs in low light conditions.This statement is more direct than many popular science articles.

How can this be verified in research?In ophthalmology, there's a long-standing test called the "dark room provocation test": the subject stays in a dark environment for a period of time, and then intraocular pressure is measured. A modified study using optical coherence tomography (OCT)...PMID 21336147The study included 76 eyes suspected of having anterior chamber angle closure. Results showed that 42% showed an intraocular pressure increase of 8 mmHg or higher after 1.5 hours of dark adaptation, meeting the positive criteria—that is,...The simple act of turning off the lights was enough to cause a significant increase in intraocular pressure in 40% of suspected cases.。

So the key point about "using your phone in the dark" isn't the phone itself, but...Turn off the lightsWhen lying down and using your phone, the environment is almost completely dark, the pupils are constantly dilated, and the eyes are fixed at the same distance for a long time. These two conditions combined are not ideal for people with shallow anterior chambers.

Why "increasing screen brightness and turning on eye protection mode" is not the answer?

Adjusting the screen brightness may seem to "shrink the pupils," but its actual effect is limited: the pupil primarily follows...Ambient lightThe difference lies in the fact that a small illuminated screen contributes far less to the overall brightness than the room itself; conversely, turning the screen to its brightest setting in a completely dark room actually increases glare and contrast. Eye-care mode alters color temperature, not pupil size.

The truly effective approach is simple:Turn on a background lightIf the room has basic lighting, the pupils won't remain dilated for extended periods. (Internal website)6 ways to protect your eyes>and<Spending 8 hours a day in front of electronic screens increases the risk of severe dry eye syndrome by 14%> This discusses viewing distance and dry eyes, which can be referenced as well.

Fifth, triggering factor two: cold medicine, allergy medication, and mydriatic eye drops.

The statement that "a cold can cause glaucoma" is not entirely accurate. What is truly related is...Some ingredients in cold medicineas well asThe eye drops used when I went to see a doctor for a cold to dilate my pupils.。

category	Common examples	mechanism	feature
Anticholinergic drugs, first-generation antihistamines	Some cold and flu medicines, allergy medications, and motion sickness medications	Pupil dilation causes pupillary block.	Those with shallow anterior chambers have the highest risk; it can occur in one or both eyes.
Adrenaline decongestants	Some oral nasal decongestants	Pupil dilation	Same as above
Mydriatic eye drops	Used when examining the fundus	Pharmacological mydriasis, with direct effects	Scottish study: Nearly one-fifth of cases are related to this.
Sulfonamide drugs (such as topiramate)	Some medications for migraines, epilepsy, and weight management	Ciliary choroidal exudation, anterior lens displacement, acute myopic drift	Bilateral, non-pupil block typeThe processing direction is opposite.

How important are the numbers?

• Scotland 114 cases:40% identified identifiable triggers, of which nearly one-fifth were related toMydriatic eye dropsrelated(PMID 28794074）。
• 72 cases in Hong Kong(1998-2000): 23.61 TP4T had an upper respiratory tract infection before the onset of the disease, and 34.71 TP4T had used cough medicine.PMID 11514744）。
• Multiple case reports documentedBilateral acute angle-closure glaucoma developed after taking over-the-counter cold and flu medication.(For example PMID 39214584）。

A review of drug-induced factors (PMID 42589938The report points out that the most commonly involved drugs include sulfonamide derivatives (mainly topiramate), serotonin-based antidepressants and triptans for migraines, potent anticholinergics, and adrenaline-based decongestants; adverse events mostly occur in...Shortly after starting medication or increasing the dosageAppear.

A crucial distinction: the two types of acute glaucoma require opposite treatment approaches.

Topiramate and similar products cause this.ciliary choroidal exudationPushing the lens and iris forward as a whole is considered "non-pupil block type," usually bilateral, and often accompanied by a sudden increase in myopia. The treatment for this condition is...Discontinue use of the causative drugIn addition, it rapidly lowers intraocular pressure; and in exudative cases,Cycloplegic agents are more suitable than miotics—This is exactly the opposite of the intuition that "pupils constrict".

Therefore, the statement "use miotics for acute glaucoma" cannot be generalized. Miotics (such as pilocarpine) do play a role in pupillary block glaucoma by increasing aqueous humor outflow; however, which one to use and when to use it depends on the mechanism. This is why such cases must be diagnosed by an ophthalmologist, rather than being treated by buying eye drops from a pharmacy.

Practical reminder:Do not stop taking medications prescribed by your doctor on your own. What you should do is—if you know you have a narrow anterior chamber angle or a family history of glaucoma, tell the pharmacist before buying cold medicine, allergy medication, or motion sickness medication, and proactively mention it during your ophthalmology or internist follow-up appointments.

Sixth, the third trigger: the season – “especially in winter”, right?

It's commonly said that winter's shorter days and longer nights, coupled with dim indoor lighting and the peak season for colds, lead to a surge in acute glaucoma cases. This reasoning sounds plausible, but looking at the data...Studies in East Asia do not support the notion of a "winter peak".。

area	Number of examples	Peak of attacks	Relationship with climate
Shantou, 2012 to 2016	1,155	Summer, June	Rainfall, ground temperature and the incidence of disease are positively correlated.
Shenzhen, 2017-2021	997	May	Relative humidity is positively correlated
Japan, 2009 to 2025	229 eyes	No significant seasonal differences	Monthly p=0.095, quarterly p=0.895
Hong Kong, 1998-2000	72	The month of influenzanegative correlation	The correlation coefficient was −0.388 (P=0.031).

The four sets of data are in the same direction:No unusually long winters have been observed in Hong Kong or neighboring regions.In Shantou and Shenzhen, the peak season is often late spring and early summer, while in Japan, it's more common throughout the year.

So why do we have the impression of "winter"? Because winter does indeed involve two things happening simultaneously:The indoor lighting is dim(Short daylight hours, fewer lights on)Use a lot of cold medicineThese two events themselves were the triggers—in other words, what truly mattered was...BehaviorIt's not the temperature or the calendar.

This conclusion is actually more useful: you don't need to be wary based on the seasons, you need to be wary based on...contextBeware of dimly lit rooms, newly taken cold medicine, and recently used eye drops that dilate the pupils.

Incidentally, the relationship between season and intraocular pressure does exist in another type of glaucoma: the intraocular pressure of patients with open-angle glaucoma is on average higher in winter than in summer.PMID 33526849(204 eyes, normal intraocular pressure glaucoma group 13.2 mmHg in winter vs. 12.0 mmHg in summer). But that is "intraocular pressure values fluctuate with the seasons", which is different from "acute attacks are concentrated in winter".

7. What does an attack look like, and why is it mistaken for a migraine?

During an acute angle-closure seizure, the following symptoms usually occur simultaneously:

• My eyes suddenly felt sharp, throbbing pain, and felt as hard as stone to the touch;
• Red eyes and corneal edema;
• Sudden blurred or decreased vision;
• When looking at lights, a rainbow-colored halo appears around them (iridescence).
• Headache on the same side, accompanied by nausea and vomiting.

The reason this set of symptoms is dangerous is that it has two "false alarms".

The first false alarm: it will relieve itself.The Department of Health's Drug Office describes the symptoms as "unstable, lasting for one or two hours before disappearing again, but each time symptoms appear, vision is impaired more." Many people feel relieved after the first relief and do not seek medical attention.

The second deceptive tactic: It looks like another disease.Severe headaches accompanied by vomiting are easily mistaken for migraines; vomiting accompanied by abdominal pain is often mistaken for gastroenteritis. The difference lies in...The performance of the eyes themselvesSymptoms include: unilateral eye pain, redness, blurred vision, and seeing halos around lights. If any two of these symptoms are present, intraocular pressure should be considered first.

The cost of a few days' delay is quantifiable.

The prospective study in Scotland compared people who sought medical attention three days or more later with those who sought it promptly.PMID 28794074）：

Results (six months later)	Seek medical attention promptly	Three days or more late
Develop into glaucoma	22.6%	60.8%
Corrected visual acuity (LogMAR, the lower the number, the better).	0.34	0.74
Number of eye drops needed to lower intraocular pressure	0.52	1.20

Long-term follow-up in Hong Kong also shows that the damage is permanent: among 40 patients with acute unilateral attacks, approximately 7.5 years after the attack,The retinal nerve fiber layer of the affected eye is 25.21 TP4T thinner than that of the other eye.（PMID 25590844Thinning of the nerve fiber layer corresponds to visual field defects.

The same study also showed that most people's vision improved after treatment—six months later, 75% visual acuity reached 6/12 or better. Therefore, the correct statement is not "blindness overnight, irreversible," but rather:An attack can cause permanent damage in a very short time, but if treated early, most people can still retain usable vision; the longer it is delayed, the greater the cost.

8. Upon arrival at the emergency room: the order of treatment.

The treatment of acute attacks follows a specific order; it doesn't mean immediately rushing into the operating room.

Step 1: Lower the intraocular pressure first

According to information from the Hospital Authority and the Drug Office, several types of drugs may be used simultaneously:

• Topical eye drops—β-blockers reduce aqueous humor production; α2-receptor agonists and carbonic anhydrase inhibitors reduce production and increase efflux;
• Oral or intravenous acetazolamide—It reduces the production of aqueous humor and has a mild diuretic effect when used systemically;
• Intravenous hyperosmolar mannitol— Reducing the volume of the vitreous body, resulting in a significant decrease in intraocular pressure, is typically used for short-term treatment;
• If necessary, add pain relievers and antiemetics, and treat corneal edema.

While taking medication, we will start to consider the next step, because the medication only "suppresses" the intraocular pressure and does not solve the problem of why the angle of the anterior chamber is closed.

Step 2: Deactivation Mechanism

Laser iridotomyThis involves creating a small opening in the iris to allow aqueous humor to bypass the pupillary block and flow directly to the angle of the anterior chamber. This is one of the standard practices for treating angle-closure glaucoma. However, as mentioned in Section 3, if the primary mechanism is an oversized lens that pushes the entire iris forward, laser treatment alone may not be sufficient.

Step 3: Treating the lens

If you also have cataracts, removing the lens addresses two issues simultaneously: the cataract itself, and the lens that takes up space and narrows the angle of the anterior chamber. The Department of Health's Office of Drug Control states, "If you also have cataracts, cataract removal may open the angle of the anterior chamber and increase the outflow of aqueous humor, thereby reducing intraocular pressure."

Step 4: The other eye also needs to be treated.

If one eye has experienced an attack, the other eye usually has a similar anatomical structure and is considered high-risk. Therefore, clinically, prophylactic laser iridotomy is generally considered for the other eye, rather than waiting for an attack. The actual procedure is determined by the ophthalmologist based on the anterior chamber angle, intraocular pressure, and lens condition.

If you have been diagnosed with glaucoma and are currently taking medication, please visit [website address].Does sleeping on your stomach increase intraocular pressure?> An article summarizing sleeping positions, intraocular pressure measurement limits, and the effects of various medications can be read in conjunction with this article.

IX. Lens Removal: Two of the Most Important Pieces of Evidence

The phrase "cataract surgery can also treat glaucoma" is frequently heard in outpatient clinics. There is some basis to this claim, but the weight of the evidence needs to be clearly stated.

EAGLE Trial: Randomized Controlled Trial of 419 People

EAGLE test(*Lancet*, 2016) recruited 419 patients aged 50 and older from ophthalmology departments of 30 hospitals in five countries.No cataractsPatients newly diagnosed with primary angle-closure glaucoma (intraocular pressure ≥30 mmHg) or primary angle-closure glaucoma were randomly assigned to either "early clear lens extraction" or "standard treatment (laser iridotomy + topical medication)" and followed up for 36 months.

• The EQ-5D health status score was higher in the removal group. 0.052(95% CI 0.015–0.088);
• Mean intraocular pressure 16.6 mmHgLower than standard treatment 1.18 mmHg(95% CI −1.99 to −0.38);
• The cost-benefit ratio of each additional quality of life adjusting life years is: £14,284。

Cochrane System Evaluation: 99 Eyes in Hong Kong and Singapore

Another piece of evidence that is closer to the local situation is Cochrane 2023 Systematic ReviewsIt found only two randomized controlled trials that met the criteria, totaling... The study involved 99 eyes and 99 participants, predominantly of Chinese descent, and took place in Hong Kong and Singapore.Comparison of "phacoemulsification lens removal" and "laser iridotomy":

result	number	Certainty of evidence
Intraocular pressure control rate at 18 to 24 months	RR 1.66(1.28–2.15)	低
12-month average intraocular pressure	低 3.20 mmHg(−4.79 to −1.61)	低
Another intraocular pressure-lowering surgery is required within 24 months.	RR 0.07(0.01–0.51)	Extremely low

Two points need to be clearly stated at the same time:FirstBoth studies were rated as having a high risk of bias and a low to very low certainty of evidence.secondThese results refer to "primary angle-closure glaucoma," not all glaucoma. The first-line treatment for open-angle glaucoma remains eye drops and laser treatment, without involving lens removal.

Therefore, the reasonable conclusion is: [correct/correct].Also has cataracts, or significant anterior chamber crowding.For patients with angle-closure glaucoma, lens extraction is an option supported by randomized controlled evidence that can address both issues simultaneously; however, it is not a case of "all glaucoma patients should undergo cataract surgery." Ultimately, the decision rests with the ophthalmologist, taking into account the anterior chamber angle, lens, intraocular pressure, and overall condition.

10. Who is at high risk: Hong Kong's figures

Acute angle-closure glaucoma has a fairly clear population distribution. A two-year prospective study in Hong Kong (…)PMID 11514744)Discover:

• The crude incidence rate for the population aged 30 and above is:10.4 cases per 100,000 people per year；
• The age-specific incidence rate rises to 70 years or older58.7 cases per 100,000 people per year；
• The relative risk for women is higher than for men. 3.8 times(95% CI 1.7–8.4).

The male-to-female ratio in another Hong Kong cohort is 1 to 7（PMID 25590844The average age is 68.3 years.

Besides age and gender, the main risk factors include:

• Farsightedness與Eyeballs are relatively short—A short anteroposterior diameter of the eyeball results in a shallower anterior chamber;
• I was toldNarrow anterior chamber angleOr the anterior chamber is shallow;
• Severe cataracts—The lens thickens, pushing the iris forward;
• Family history—However, it should be noted that only 5.61 TP4T patients in the aforementioned Hong Kong study had a positive family history, soNo family history does not mean no risk.；
• Ethnicity – Asian people are at higher risk of acute angle-closure type (Department of Health, Office of Drugs).

As forHigh myopiaIt is a risk factor for open-angle glaucoma, which is different from acute angle-closure glaucoma, and the two should not be confused.

Inspection recommendations:Starting at age 40, a full eye exam should be scheduled, including assessment of intraocular pressure, optic nerve, visual field, and anterior chamber angle. Those diagnosed with anterior chamber angle stenosis should have their intraocular pressure monitored regularly as advised by their doctor.New technology from PolyU helps patients detect glaucoma early.> Introduced the progress of local screening technologies.

11. Daily routine: Three useful items, two useless items

Three useful items

First, give the room some light.Avoid reading or using your phone for extended periods in complete darkness. You can continue using your phone, just turn on a bedside lamp—this step directly targets the "pupil dilation" mechanism.

Second, discuss the medication issue in advance.If you know you have a narrow anterior chamber angle or a family history of glaucoma, ask the pharmacist before buying cold and flu medicine, allergy medication, or motion sickness medication; when you see an ophthalmologist or other specialist, mention this background. If you experience eye pain or blurred vision after a cycloplegic refraction, do not wait until your next follow-up appointment.

Third, complete the inspection thoroughly.An "eye exam" is not just about checking the prescription for glasses. The four items that are related to glaucoma assessment are intraocular pressure, optic nerve, visual field, and anterior chamber angle.

The Department of Health's Drug Office also mentioned several lifestyle details worth noting: drinking 1 liter or more of liquid in a short period of time may temporarily increase intraocular pressure; large amounts of caffeine may increase intraocular pressure; stress may trigger acute angle-closure glaucoma in high-risk individuals.

Two useless items

First, increase the screen brightness.As mentioned in Section 4, the pupil follows the ambient light, not the bright light from the screen; turning the screen to its brightest setting in a completely dark room will actually increase glare.

Secondly, turn on the eye protection mode.The eye protection mode adjusts the color temperature and blue light ratio, but it has no effect on pupil size. It can make your eyes feel more comfortable, but it cannot replace turning on the lights.

There is one more thing to clarify:No health supplement can prevent or reverse glaucoma.Glaucoma causes irreversible optic nerve damage. Currently, the only evidence suggests that lowering intraocular pressure can slow disease progression. Instead of spending money on eye supplements, it's better to get thorough checkups and use eye drops regularly.

XII. Frequently Asked Questions

Does using your phone in the dark really cause acute glaucoma?

This is possible for people with a pre-existing narrow anterior chamber angle. In a dark environment, the pupil dilates, causing the peripheral iris to stack towards the center, further narrowing the angle and increasing intraocular pressure. One study showed that in 76 eyes suspected of having anterior chamber angle closure, 42% experienced an increase in intraocular pressure of 8 mmHg or more after dark adaptation. However, it should be emphasized that this is...TriggersNot everyone will develop it; people with a wide anterior chamber angle have a much lower risk.

Can acute glaucoma cause blindness overnight?

"Blindness overnight" emphasizes the urgency, but it can easily lead people to believe that the condition is "beyond saving." A more accurate understanding is that an acute attack can cause permanent nerve damage within hours to days. Those who delay seeking medical attention for more than three days have a 60.81 TP4T chance of developing glaucoma six months later, compared to only 22.61 TP4T for those who seek timely treatment. Even so, six months later, 751 TP4T individuals still have vision of 6/12 or better. Early medical intervention makes a significant difference in outcomes.

Does an intraocular pressure of over 21 mmHg mean glaucoma?

No. High intraocular pressure does not equal glaucoma. Some people have high intraocular pressure but no damage to the optic nerve or visual field; this is called ocular hypertension. Some glaucoma patients have consistently normal intraocular pressure. Therefore, diagnosis requires examining the optic nerve and visual field, not just a single number. This is explained in more detail in another article on intraocular pressure within this website.

Is it more likely to flare up in winter?

Looking at data from Hong Kong and neighboring regions, this is not the case. Shantou had the most cases in June (1,155), Shenzhen had the most in May (997), Japan had the most (229) on average throughout the year, and Hong Kong's monthly incidence rate of 72 cases showed a negative correlation with the month of the flu. The impression of "more cases in winter" is mainly due to darker indoor environments and increased use of cold medicine in winter—these are the real contributing factors.

Can high-risk individuals take cold medicine?

It's not a blanket ban, but you should ask first. Some cold and flu medications contain anticholinergic or adrenaline-like ingredients, which may dilate the pupils; mydriatic eye drops have a more direct effect. If you know you have a narrow anterior chamber angle, a family history of glaucoma, or have had glaucoma attacks, tell the pharmacist before buying medication, and avoid increasing the dosage or mixing multiple cold and flu medications on your own.

Can glaucoma be cured?

No. The Department of Health's Drug Office states that glaucoma cannot be cured, and the damage it causes is irreversible; however, early detection and appropriate treatment can prevent or delay further vision loss. The goal of treatment is to control the disease and preserve existing vision.

Can cataract surgery also treat glaucoma?

For individuals with angle-closure glaucoma and concurrent cataracts, two things can be addressed simultaneously—lens removal opens the angle of the anterior chamber and increases aqueous humor outflow. Both the EAGLE trial and the Cochrane systematic review support this approach; however, the latter has very low to extremely low certainty of evidence, and both studies carry a high risk of bias. For open-angle glaucoma, lens removal is not the primary treatment.

Why do I need to get laser treatment in my other eye too?

Because the anatomy of both eyes is usually similar, if one eye has experienced an attack and the other is also at high risk, prophylactic laser iridotomy is generally considered clinically, rather than waiting for an attack to occur. The specific arrangements are determined by the ophthalmologist based on the anterior chamber angle, intraocular pressure, and lens condition.

How can I tell if my headache and vomiting are related to eye pressure?

Check for any simultaneous changes in the eyes: unilateral eye pain, redness, sudden blurred vision, or seeing rainbow halos around lights. If two or more of these symptoms are present, intraocular pressure should be the primary concern, and you should go directly to the emergency room. Relying solely on painkillers or anti-nausea medications will waste crucial time.

What kind of examination is needed to determine if the anterior chamber angle is narrow?

A gonioscopy examination by an ophthalmologist is required, and in some cases, anterior chamber angle optical coherence tomography (OCT) or ultrasound biomicroscopy may also be included. This is not usually included in the prescription testing for glasses, so you should proactively inform the doctor that you need a glaucoma-related evaluation.

XIII. Sources of Information

• Department of Health, Drug Office: <Glaucoma Drugs>
• Department of Health Elderly Health Services: <Common Eye Problems and Eye Care Tips>
• Hong Kong Eye Organization: Glaucoma Special Report
• Epidemiology of acute primary angle-closure glaucoma in the Hong Kong Chinese population: prospective study. Hong Kong Med J(2001)
• Cross-sectional study of the retinal nerve fiber layer thickness at 7 years after an acute episode of unilateral primary acute angle closure. Medicine(2015)
• The incidence of acute angle closure in Scotland: a prospective surveillance study. Br J Ophthalmol(2018)
• Seventeen-Year Clinical Analysis of Acute Primary Angle-Closure Glaucoma at a Single Japanese Tertiary Center. Cureus(2026)
• Seasonal variations and climatic factors on acute primary angle-closure admission in southern China. Acta Ophthalmol(2021)
• Monthly variations and climatic factors on acute primary angle-closure admissions in Shenzhen. Int J Ophthalmol(2026)
• Seasonal fluctuation in intraocular pressure and its associated factors in primary open-angle glaucoma. Eye(2021)
• Modified dark room provocative test for primary angle closure. J Glaucoma(2012)
• Hidden mechanisms beyond the pupillary block in acute angle closure: ultrasound biomicroscopic study. Clin Exp Ophthalmol(2017)
• Systemic Medications as Triggers of Acute Angle-Closure Glaucoma: A Narrative Review. J Clin Med(2026)
• Bilateral simultaneous acute angle closure glaucoma triggered by an over-the-counter cold and influenza medication. BMJ Case Rep(2024)
• Effectiveness of early lens extraction for the treatment of primary angle-closure glaucoma (EAGLE): a randomized controlled trial. Lancet(2016)
• Lens extraction versus laser peripheral iridotomy for acute primary angle closure. Cochrane Database Syst Rev(2023)

Source: A local media interview with ophthalmologist Dr. Lee Wan-Wei in December 2020. The metaphors of "vision thieves" and "vision robbers," the use of eyes in dark environments, cold medicine, and the practice of performing cataract surgery simultaneously all come from this interview.

Health Reminder

This article provides health education and general information and does not constitute medical advice, nor can it replace a doctor's diagnosis and prescription. Diagnosing glaucoma requires multiple examinations, including those of intraocular pressure, optic nerve, visual field, and anterior chamber angle; it cannot be determined by a single number or self-observation.

If you suddenly experience severe pain in one eye, redness in the eye, a sudden decrease in vision, seeing rainbow halos around lights, accompanied by headache or vomiting, please...Call 999 immediately or go to the emergency room.Do not wait for the symptoms to subside on their own. If you have been diagnosed with glaucoma, please take medication and attend follow-up appointments as instructed by your doctor. Do not stop taking medication, reduce the dosage, or add other eye drops on your own.