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The single most common thing we hear from patients with dry eye is that they don't believe they have it. Their eyes are streaming. They're going through tissues. Dry is the last word they'd use. But watering is one of the classic signs. When the tear film breaks down, the surface of the eye gets irritated, and the lacrimal gland responds by flooding the eye with a burst of watery tears. It's the same reflex that kicks in when you chop an onion. Those emergency tears are thin, they lack the oils that keep them in place, and they run straight down your cheek rather than coating the eye properly. So you end up with a wet face and a dry eye at the same time. That contradiction is a decent summary of dry eye in general. Very little about it is obvious. What dry eye actually is Your tear film is only about seven microns thick, which is roughly a tenth the width of a human hair. It has three components working together: a mucin layer that helps tears stick to the eye, a watery layer that carries oxygen and nutrients, and a thin oily layer on top that stops the whole thing evaporating. Dry eye disease is what happens when that film stops doing its job. The current international consensus describes it as a loss of homeostasis of the tear film, with tear instability, increased saltiness of the tears, inflammation, damage to the ocular surface, and changes in the corneal nerves all feeding into each other. That last part matters. Dry eye is not simply a plumbing problem where you've run out of tears. It's an inflammatory condition, and inflammation is why it tends to get worse rather than better if it's left alone. Irritation triggers inflammation, inflammation damages the glands and the surface, the damage makes the tear film less stable, and round it goes. Broadly, dry eye splits into two types: Evaporative dry eye. You make enough tears but they disappear too fast, usually because the oily layer is thin or poor quality. This is the far more common form, accounting for the large majority of cases. Aqueous deficient dry eye. The lacrimal gland isn't producing enough of the watery component. This is the type associated with Sjögren's syndrome and other autoimmune conditions. Plenty of people have both. The symptoms that don't sound like dry eye Grittiness and burning are the ones people expect. These are the ones they don't: •     Vision that blurs and then clears when you blink. A stable tear film is the first refracting surface your eye has. When it breaks up between blinks, vision goes soft. Blink, and it sharpens again. If your sight fluctuates while you read or drive, the tear film is a likely culprit. •     Eyes that feel worse in the morning. Often a sign of poor lid seal overnight or lid margin disease rather than daytime evaporation. •     Contact lenses that used to be comfortable and now aren't. Reduced wear time is frequently the first thing patients notice. •     Tired, heavy eyes by mid-afternoon. Especially on screen-heavy days. •     Light sensitivity. An irritated cornea is a sensitive cornea. •     Stringy mucus at the inner corner. Symptoms and clinical signs often don't line up neatly either. Some people have eyes that look terrible on examination and barely notice. Others have mild-looking surfaces and are genuinely miserable, usually because the corneal nerves have become sensitised. Neither situation means the person is exaggerating or imagining things. What's driving it Screens. We blink around 15 times a minute normally. Staring at a monitor can drop that to five or six, and a good proportion of those blinks are incomplete, meaning the upper lid never fully meets the lower. Incomplete blinks don't squeeze the oil glands properly, so the oily layer thins out over the course of the day. Age. Tear production declines and the oil glands change with age. Most people over 50 have some degree of change even without symptoms. Hormones. Dry eye is considerably more common in women, and the perimenopausal and postmenopausal years are a frequent trigger point. Medication. Antihistamines, some antidepressants, beta blockers, diuretics, hormonal contraception, isotretinoin for acne, and several glaucoma drops can all contribute. Never stop a prescribed medicine because of this — but do mention it to whoever is treating your eyes. Contact lens wear. Long-term wear is associated with changes to the lid margins and oil glands. Environment. Air conditioning, car heaters blowing at the face, aeroplane cabins, central heating, and windy days all speed up evaporation. Previous eye surgery. Laser refractive surgery cuts corneal nerves, which reduces the feedback loop that tells the eye to produce tears. Most recover, but it can take months. Systemic conditions. Sjögren's syndrome, rheumatoid arthritis, thyroid eye disease, rosacea and diabetes are all linked. What actually helps Start with the mechanics Before you buy anything, change what your eyes are doing. The 20-20-20 principle is worth the effort: every 20 minutes, look at something around 20 feet away for 20 seconds. The point isn't really the distance. It's that shifting focus interrupts the staring and prompts a few proper blinks. Then there's deliberate blinking. Close gently, pause for two seconds, squeeze lightly, then open. Five of those, a few times a day. It sounds far too simple to do anything, but for people with incomplete blinking it makes a measurable difference to how the oil glands empty. Raise your monitor conversation: most people should be looking slightly down at their screen, not level or up. A lower gaze angle means less of the eye surface is exposed, and less exposed surface means less evaporation.  Lubricants, chosen properly Not all artificial tears are the same, and the differences matter more than the price. Go preservative-free if you're using drops more than about four times a day. Benzalkonium chloride, the most common preservative, is toxic to the corneal surface with repeated exposure. Unit-dose vials or multidose bottles with a preservative-free valve both work. Match the drop to the problem. Sodium hyaluronate drops hold water well and suit general dryness. Lipid-containing drops, often sold as sprays or emulsions, are aimed at evaporative dry eye and are the better choice if your oil glands are the issue. Thicker gels and ointments last longer but blur vision, so they're usually a bedtime option. Give any new drop a fair trial. Four weeks, used consistently, before you judge it. Warm compresses, done correctly If the oil glands are involved — and they usually are — heat is the intervention that does the heavy lifting. This is covered properly in the article on meibomian gland dysfunction, because there's more to it than holding a flannel to your face for 30 seconds. Where a clinic comes in If self-management isn't enough after a couple of months, there's a lot more available: •     Anti-inflammatory drops. Ciclosporin 0.1% is licensed in the UK for severe dry eye with corneal inflammation. It takes months to work and often stings initially, so expectations need setting up front. •     Short courses of steroid drops to break an inflammatory cycle, always under supervision because of the pressure and cataract risks. •     Low-dose oral doxycycline, prescribed for its anti-inflammatory effect on the oil glands rather than as an antibiotic. •     Punctal plugs. Tiny inserts that block tear drainage, keeping what you produce on the eye for longer. Genuinely useful in aqueous deficient dry eye, less so if evaporation is the problem. •     Intense pulsed light and thermal pulsation treatments for gland dysfunction. •     Autologous serum drops, made from the patient's own blood, for severe surface disease that hasn't responded to anything else. On omega-3 Fish oil supplements were recommended fairly confidently for years. Then a large randomised trial published in 2018 found no significant benefit over an olive oil placebo, which caused a rethink. The picture now is mixed: some smaller studies still show benefit, particularly in gland dysfunction, and the trial has been criticised on the grounds that the placebo may not have been inert. It's reasonable to try, it's unlikely to hurt, but it isn't the reliable fix it was once presented as. Check with your GP if you're on anticoagulants. When to get it looked at sooner rather than later Most dry eye is a quality-of-life problem, not a sight-threatening one. But book an appointment promptly if you have: •     Pain rather than discomfort •     A red eye that isn't settling •     Vision loss that doesn't clear on blinking •     Any red painful eye while wearing contact lenses — this needs same-day attention •     Sudden onset alongside dry mouth or joint pain, which may point to an autoimmune cause worth investigating The realistic outlook Dry eye is usually a condition you manage rather than one you cure. That sounds discouraging, but managed well it stops being something you think about. The people who do best are the ones who identify what's actually driving their case — glands, tear production, blinking habits, environment, or some combination — and treat that specifically, instead of reaching for whichever drop happens to be nearest. If your eyes have been bothering you for months and you've been getting by on supermarket drops, a proper assessment is worth booking. Tear film breakup time, osmolarity, lid margin examination and gland imaging take a few minutes and tend to explain a lot.

The cornea is the clear dome at the front of the eye, and it does something no other transparent structure in the body manages: it repairs itself, repeatedly, while staying clear enough to see through. It's also one of the most densely innervated tissues you have. There are something in the region of 300 to 600 times more nerve endings per square millimetre in the cornea than in the skin. This is why a scratch the width of a hair can feel like a piece of grit lodged under your lid, and why a genuinely small injury can be genuinely agonising. Understanding how healing works makes the recovery timeline much less mysterious, and explains why some eyes recover in two days while others take months. Five layers, three healing capacities From front to back: Epithelium. Five or six cell layers, around 50 microns thick. Completely replaced every seven to ten days under normal conditions, using stem cells that live in the limbus, the ring where the clear cornea meets the white of the eye. This layer heals fast and heals without scarring. Bowman's layer. A tough acellular sheet beneath the epithelium. It does not regenerate. Once breached, it's replaced by scar tissue. Stroma. About 90% of the corneal thickness, made of collagen fibrils arranged with extraordinary regularity. That regularity is why the cornea is transparent. Repair is possible, but the replacement collagen is laid down less neatly, and less neat means less clear. Descemet's membrane. A basement membrane produced by the layer behind it. It can be regenerated. Endothelium. A single layer of cells that pumps fluid out of the stroma to keep it clear. In humans it essentially does not divide. You're born with roughly 3,000 to 4,000 cells per square millimetre and lose them slowly for life. When cells are lost, neighbours stretch and spread to fill the gap. Below about 500 cells per square millimetre, the pump fails and the cornea swells. So healing capacity depends almost entirely on depth. Superficial injuries heal completely. Deeper ones heal, but with consequences. What happens after a scratch A corneal abrasion — the kind you get from a fingernail, a branch, a stray contact lens edge or a speck of grit — sets off a sequence that's remarkably consistent. Hours 0 to 6: the latent phase. Not much visible movement. Underneath, cells at the wound edge are dismantling the anchoring structures that hold them to the underlying membrane, reorganising their internal scaffolding, and preparing to move. Damaged cells at the edge undergo programmed cell death and clear out of the way. Hours 6 to 36: migration. Epithelial cells slide across the defect as a sheet. They don't divide during this phase; they flatten out and crawl, covering roughly 60 to 80 microns an hour. Most small abrasions are fully covered within 24 to 48 hours. This is the stage where pain drops sharply, which is why day two usually feels dramatically better than day one. Days 2 to 7: proliferation. Now the cells start dividing, restacking into the proper multi-layered arrangement and restoring normal thickness. Weeks to months: adhesion. The slowest and most underappreciated part. The anchoring complexes — hemidesmosomes and anchoring fibrils — that glue the epithelium to the layer beneath have to be rebuilt, and that takes six weeks to three months. That last phase explains a condition that catches a lot of people out. Recurrent corneal erosion happens when the new epithelium is covered but not yet properly anchored. It typically strikes on waking, when the lid peels the loose sheet away as the eye opens. Sudden sharp pain, watering and light sensitivity, weeks or even months after an injury everyone had forgotten about. If you've had an abrasion, especially a fingernail or paper cut injury, a lubricating ointment at bedtime for several weeks is a sensible precaution. Why some corneas heal badly Healing depends on more than the injury itself. A poor tear film. The tear film supplies oxygen, growth factors and the moist environment epithelial cells need to migrate. Untreated dry eye or meibomian gland dysfunction slows healing measurably and increases the chance of a defect becoming persistent. This is the direct link between the other two articles on this site and this one. Diabetes. Diabetic corneas have abnormal basement membranes, weaker epithelial adhesion and reduced nerve function. Delayed healing after eye surgery is well recognised. Reduced corneal sensation. The nerves aren't only there for sensation. They release factors that keep the epithelium healthy. When they're damaged — by herpes simplex or zoster, by diabetes, by long-term contact lens wear, by laser refractive surgery, or by certain neurosurgical procedures — the epithelium can break down and refuse to heal, a condition called neurotrophic keratopathy. It's often painless, which is precisely what makes it dangerous. Preservatives. Benzalkonium chloride, present in many multidose eye drops, is toxic to epithelial cells with repeated exposure. Preservative-free formulations are the right choice for any eye that's healing. Topical anaesthetic misuse. Anaesthetic drops abolish the pain of a corneal abrasion almost instantly, which makes them tempting. They are also directly toxic to the epithelium and block healing entirely. Repeated self-administration can destroy a cornea within days. This is one of the genuinely serious mistakes in eye care, and it isn't rare. Limbal stem cell deficiency. If the limbus is damaged — by chemical burns, severe inflammation, or prolonged contact lens wear — the cornea loses its source of replacement cells. Conjunctival tissue grows across instead, bringing blood vessels and opacity with it. Steroid drops. Useful for controlling inflammation and scarring, but they slow epithelial healing and, in the presence of infection or a thinning cornea, can be actively harmful. Always prescription-only, always supervised. Hypoxia. Contact lenses worn too long, or overnight in lenses not designed for it, starve the cornea of oxygen and impair its ability to repair. What supports healing Preservative-free lubricants, frequently. Sodium hyaluronate is particularly useful — it holds water, and there's evidence it encourages epithelial cell migration. Sorting out the ocular surface. Treating underlying dry eye or lid disease is not a side issue. It's often the difference between a defect that closes and one that doesn't. Bandage contact lenses. A soft lens acting as a shield, stopping the lid from wiping over the healing surface with every blink. Fitted and monitored by a clinician, never improvised. Vitamin A ointment, which supports epithelial cell differentiation. Autologous serum drops. Made by diluting a patient's own blood serum, these contain the growth factors and vitamins found in natural tears. Very effective for persistent defects and severe surface disease. Available through hospital services in the UK. Amniotic membrane. Placental tissue applied over the cornea, either as a graft or a ring-mounted disc. It's anti-inflammatory, anti-scarring, and provides a scaffold for cells to grow across. Cenegermin. A recombinant human nerve growth factor drop, approved for moderate to severe neurotrophic keratitis, which addresses the nerve problem rather than just the surface symptoms. Punctal occlusion to keep lubricants and growth factors on the eye for longer. And one thing that has fallen out of favour: pressure patching. It was standard practice for abrasions for decades. The evidence now suggests it doesn't speed healing and may reduce comfort. It should never be used for a contact lens-related abrasion, where sealing the eye risks turning a scratch into a sight-threatening Pseudomonas infection. When healing goes wrong: the warning signs Get seen urgently — same day — if you have: •     A red, painful eye and you wear contact lenses. This is microbial keratitis until proven otherwise. Contact lens-related infections can damage sight within 24 to 48 hours. Take your lenses out, keep the case, and go. •     A white or grey spot on the cornea •     Pain that worsens after day two instead of improving •     Pus or thick discharge •     Vision that is dropping rather than clearing •     Any injury involving chemicals — irrigate immediately with clean water or saline for at least 20 minutes before doing anything else, including phoning ahead •     Any suspicion of a penetrating injury, particularly from hammering, grinding or drilling. Don't press on the eye. Go to A&E. An eye that had a small injury and is steadily getting better is usually fine. An eye that is getting worse is not, and the window for preventing permanent damage can be short. What healing leaves behind If the injury stayed within the epithelium, the cornea returns to exactly how it was. No scar, no visual consequence. If it went deeper, into Bowman's layer or the stroma, keratocytes in the stroma transform into myofibroblasts, which lay down repair collagen and pull the wound closed. The new collagen isn't arranged with the same precision, so it scatters light. The result is haze or a scar. Whether that affects vision depends almost entirely on location. A dense scar off to one side may never be noticed. A faint one directly over the pupil can be genuinely disabling. Corneal scars often fade over the first six to twelve months as the tissue remodels, so early appearance isn't the final verdict. Where scarring does affect sight, options run from rigid contact lenses that mask an irregular surface, through laser treatments that smooth superficial scars, to partial or full-thickness corneal transplantation. Modern lamellar techniques allow surgeons to replace only the damaged layers, which improves outcomes and reduces rejection risk considerably compared with the full-thickness grafts of the past. The cornea is more resilient than most people assume. It just needs the right conditions — a healthy tear film, adequate oxygen, intact nerves, no toxic drops, and enough time.

There are somewhere between 25 and 40 tiny oil glands running vertically through your upper eyelid, and another 20 to 30 in the lower. They're called meibomian glands, after the German physician who described them in the 1660s. Every time you blink properly, they release a small amount of oil onto the edge of the lid, which spreads across the tear film and slows evaporation. When they stop working well, tears evaporate two or three times faster than they should. That is the mechanism behind most dry eye — not a shortage of tears, but a shortage of the oil that keeps them where they belong. The awkward part is that these glands can be quietly deteriorating for years before anyone notices. By the time symptoms show up, some of the gland tissue may already be gone, and gland tissue that has atrophied does not grow back. That's the single most important thing to understand about MGD, and the reason it's worth taking seriously earlier than most people do. What goes wrong Two things, usually at the same time. The openings block. The gland orifices sit along the lid margin, just behind your lashes. Over time they can become capped with hardened oil, keratin and debris. Nothing gets out. The oil itself changes. Healthy meibum is clear and runny at body temperature, roughly the consistency of olive oil. In MGD it thickens. It becomes cloudy, then granular, then in advanced cases something close to toothpaste. Thick oil doesn't flow through narrow ducts, which worsens the blockage, which raises pressure inside the gland, which damages the cells lining it. If the blockage persists, the gland dilates, the tissue atrophies, and eventually it drops out altogether. On a meibography scan — an infrared image of the lids — you can see this directly. Healthy glands look like a neat row of vertical stripes. In advanced MGD there are gaps, shortened stubs and truncated ends. How to tell if you have it Some of the signs are visible in a mirror. Pull your lower lid down gently in good light and look at the margin, the strip of skin just behind the lashes: •     Small white or yellow caps over the gland openings •     Fine red blood vessels crossing the lid margin towards the lashes •     A thickened, irregular or notched lid edge •     Foam or froth collecting at the outer corner or along the lid margin •     Crusting at the lash bases, which points to blepharitis, a frequent travelling companion of MGD Symptom-wise, MGD tends to produce: •     Eyes that feel worse as the day goes on •     Grittiness, burning, or a sensation of something in the eye •     Blurred vision that clears when you blink hard •     Reduced contact lens comfort •     Watery eyes, for the reflex-tearing reasons covered in the dry eye article •     Recurrent styes or chalazia, which are essentially blocked glands that have become inflamed or infected Quite a lot of people with clear gland dropout on imaging report no symptoms at all. That's part of why routine lid margin examination matters even when nothing hurts. Why it happens Blinking, or the lack of it. Every complete blink squeezes the glands. Incomplete blinks — where the upper lid comes down most of the way but doesn't fully meet the lower — don't. Screen use produces a lot of incomplete blinks. So does reading, driving and anything else requiring sustained concentration. Over years, poor blinking means poor gland turnover. Age. Gland dropout increases steadily from around the fourth decade. Skin conditions. Rosacea and seborrhoeic dermatitis are strongly associated. If you flush easily, have visible facial redness, or have a history of dandruff and scaly eyebrows, the lid margins are usually involved too. Demodex mites. These live in hair follicles and are more common with age. In larger numbers they cause a characteristic sleeve of debris around the lash base and can inflame the glands. They need targeted treatment, not just standard lid hygiene. Hormonal changes. Androgens influence gland function, which is one reason MGD becomes more common around and after the menopause. Isotretinoin. Effective for acne, but it shrinks sebaceous glands throughout the body, including the meibomian glands. The effect can outlast the course of treatment. Contact lens wear. Long-term wear is associated with gland dropout, although the mechanism is still debated. Eye makeup on the waterline. Applying eyeliner or kohl to the inner lid margin puts pigment directly over the gland openings. It's a genuine risk factor, and one that's easy to change — apply outside the lash line instead. Treatment: heat is the foundation Meibum needs to be warmed before it will move. The melting point of abnormal meibum is higher than normal meibum, which is why casual attempts at warm compresses so often do nothing. To actually work, a compress needs to hold the inner lid surface at roughly 40°C for around eight to ten minutes. A flannel run under the hot tap loses most of its heat within 90 seconds. If you're using a flannel, you'll need to re-wet it every couple of minutes, and honestly, most people give up. A reusable microwaveable eye mask filled with flax or silica beads is a far better bet. Heat it per the instructions, check the temperature against the inside of your wrist first, and keep it on for the full duration. Comfortably warm, never hot. Burning the eyelid skin is a real risk and the skin there is the thinnest on the body. Then massage. Heat alone softens the oil; something has to move it. With clean hands and eyes closed, use a fingertip to sweep the upper lid downwards towards the lashes, and the lower lid upwards towards the lashes. Firm but gentle, about ten strokes each. Always towards the lash line — that's the direction the ducts run. Then clean. Wipe along the lash base and lid margin with a dedicated lid wipe or a foam cleanser on a cotton pad. This clears away the softened oil and debris you've just released. Diluted baby shampoo was the standard advice for years and still gets recommended, but purpose-made lid cleansers are gentler on the ocular surface and generally better tolerated. Do all three, in that order, once or twice daily. Expect to keep going for at least six to eight weeks before judging the results, and expect to continue in some form indefinitely. MGD comes back when treatment stops. When home treatment isn't enough In-clinic gland expression. A clinician warms the lids and applies controlled pressure with forceps or paddles to clear blocked ducts directly. More effective than anything you can do at home, and often used to reset things before you take over with maintenance. Thermal pulsation systems. Devices such as LipiFlow apply heat to the inner lid surface while massaging from the outside, in a single 12-minute treatment. Results typically last somewhere between nine and eighteen months. Intense pulsed light (IPL). Originally a dermatology treatment for rosacea, now widely used for MGD. Pulses of filtered light applied to the cheeks and lower lids reduce inflammation, close abnormal blood vessels and appear to improve meibum quality. Usually a course of three or four sessions a few weeks apart. The evidence base has strengthened considerably, though it works better for some patients than others and it isn't suitable for all skin types. Topical azithromycin, which has both antibacterial and anti-inflammatory effects on the lid margin. Low-dose oral doxycycline or lymecycline. Prescribed at anti-inflammatory rather than antibiotic doses, typically for several weeks to months. Not suitable in pregnancy or for children, and it increases sun sensitivity. Demodex-directed treatment if mites are found, usually a lid cleanser containing terpinen-4-ol, the active component of tea tree oil. Neat tea tree oil should never go near the eye. Blinking retraining. A structured programme of conscious complete blinks, sometimes with an app or reminder, aimed at the underlying mechanical problem rather than its consequences. The point about acting early Most chronic eye conditions give you some warning. MGD often doesn't. Gland dropout accumulates silently, and the treatments above are far better at preserving remaining glands than at rescuing lost ones. So if you're in your thirties or forties, spend a lot of time on screens, and your eyes get tired by the evening, that's worth mentioning at your next sight test rather than filing under normal. Ask whether your lid margins have been examined and whether meibography is available. It takes a couple of minutes and it tells you where you stand. The glands you protect now are the ones you'll still have in twenty years.