Thyroid eye disease and diabetes-related dry eye

Thyroid disease and diabetes are two of the systemic conditions that reliably show up behind stubborn dry eye, and they get there by completely different routes. Thyroid eye disease is mostly a mechanical problem: the eye sits further forward, the lids sit further apart, and more surface is exposed to the air. Diabetes-related dry eye is mostly a nerve and gland problem, tied to how well blood glucose has been controlled over time.

What they share is the part that matters most for treatment. In both, the dry eye is manageable, but the systemic condition is what drives it, so the person treating that condition is as important as the person treating your eyes.

Thyroid eye disease: exposure is the mechanism

In thyroid eye disease the tissues behind and around the eye swell, pushing the eye forward, and the upper lid tends to retract upward. The result is a wider palpebral aperture: more of the ocular surface sits exposed between the lids, and there is more of it for each blink to cover.

Three consequences follow. Tears evaporate from a larger area. Blinks are more likely to be incomplete, so the lower cornea is wiped less often than it needs to be. And at night the lids may not fully close, which is a distinct problem in its own right and one we cover in our article on sleeping with your eyes open. If your eyes are worst on waking, that overnight exposure is the first thing to consider.

This is why thyroid-related dry eye often does not respond well to drops alone. Lubricants replace what is lost; they do not narrow the gap that is losing it.

When thyroid disease shows up as dry eye first

It happens, and the presentation is subtle enough to be worth describing. Gupta and colleagues reviewed 539 patients referred for dry eye evaluation at a specialist centre over two years. Twenty-one of them were diagnosed with occult thyroid eye disease, based on typical findings on orbital echography.

All 21 presented with dry eye symptoms. Their median age was 57, with a range of 24 to 78, and 86% were women. None carried a prior diagnosis of thyroid eye disease, and none had the typical findings the condition is known for: no protruding eye, no restricted eye movement, no double vision. What raised the suspicion instead was redness of the conjunctiva, with or without swelling, localised over the extraocular muscles, present in every one of them, and a subtle widening of the gap between the lids in 48%.

The routine dry eye findings were unremarkable by comparison: corneal fluorescein staining in 57%, a rapid tear break-up time in 31%, and an abnormal Schirmer test in only 19%. Four patients had another rheumatological condition associated with dry eye, three with Sjögren's syndrome and one with rheumatoid arthritis. Patients were treated topically with ciclosporin 0.05% two to four times a day, with or without a steroid, and other measures were used as needed, including warm compresses, artificial tears and punctal plugs. That regimen was chosen and supervised in a specialist clinic; it is not a protocol to ask for by name. Most, 76%, had an improvement in symptoms. The authors concluded that occult thyroid eye disease should be considered in the differential diagnosis when evaluating dry eye patients.

Keep the scale in mind: 21 patients out of 539, at a tertiary referral centre, identified retrospectively. This is not a common explanation for dry eye. It is a reason for a clinician to look at the pattern of redness and the width of your lid opening rather than only at your tear film, and a reason to mention any thyroid history when you book.

Thyroid signs that need attention quickly

Dry eye symptoms are not urgent. Some of the things that can accompany thyroid eye disease are. Contact your optometrist or ophthalmologist promptly, or go to an eye emergency service, if you develop double vision, a change in your vision or in how colours look, pain behind or around the eye, or an eye that is visibly becoming more prominent. New inability to close an eye belongs in the same category.

Those symptoms point to the orbit rather than the ocular surface, and they are assessed and managed by an ophthalmologist working with the doctor treating your thyroid.

Diabetes and the tear film

Diabetes is one of the leading causes of dry eye. In their review, Zhang and colleagues describe dry eye as the most frequently encountered condition of the ocular surface system, identify diabetes mellitus as one of its leading causes, and note that an increasing prevalence of diabetes-associated dry eye has been reported in recent years. They also state plainly that poor glycaemic control affects both the anterior and the posterior segments of the eye.

We are not going to quote you a percentage, because the abstract of that review does not give one, and the figures that circulate online vary widely depending on the population studied and the definition used. The honest summary is that dry eye is common in diabetes and that the risk tracks with how well glucose has been controlled.

The same review is careful about mechanism, stating that the pathogenesis and specific features of diabetes-related dry eye remain uncertain, and that interventions are limited to those used for dry eye generally. The processes usually discussed are reduced corneal sensation, so the eye does not signal that it needs to blink; peripheral neuropathy affecting the nerve supply to the lacrimal gland; and changes in the meibomian glands themselves. Treat those as the leading explanations rather than settled ones.

Reduced corneal sensation deserves a line of its own, because it inverts the usual rule. If the nerves reporting discomfort are blunted, the surface can be more damaged than it feels. A person with diabetes whose symptoms seem mild may still have significant staining at the examination, which is a good argument for being examined rather than going by how the eyes feel.

Why glucose control and eye checks both matter

Since poor glycaemic control affects the front and the back of the eye, the work you do with your diabetes team is also dry eye treatment, even though it never feels like it. It is slower than a drop, and it is the only part of this that addresses the driver.

Keep the two kinds of eye appointment separate in your mind. Diabetic retinal screening looks at the back of the eye for retinopathy, and comfortable eyes tell you nothing at all about it. Dry eye assessment looks at the front. Attending one is not a substitute for attending the other, and the front-of-eye tests involved are described in our guide to dry eye tests.

What this means for treatment

For both conditions the surface treatment is the standard staged ladder the DEWS II management review derived, applied step by step according to severity and with the systemic driver in mind. Preservative-free lubricants used regularly. Attention to blinking, screens and the environment, which matters more when the aperture is wide or corneal sensation is reduced. Lid hygiene and warmth where the meibomian glands are involved, which our article on meibomian gland dysfunction explains. Overnight protection where the lids do not fully close. Prescription anti-inflammatory treatment where the surface is inflamed, prescribed and monitored by an ophthalmologist or an optometrist with prescribing rights.

If an examination confirms a meibomian gland component, warming the lids is a first-line, guideline-recommended step for that part of the problem, and the Meibocare E-Heated Eye Mask is designed to bring the eyelids to about 42 °C on the recommended setting and timer. Be clear on what it is for: it addresses the evaporative, gland-related component only. It does nothing about lid retraction, exposure or blood glucose. If you have an eye infection, have had eye surgery recently, have glaucoma, reduced corneal sensation, or notice any change in your vision, speak to your optometrist or ophthalmologist before starting or continuing heat therapy. That advice applies with extra force in diabetes and in active thyroid eye disease, where sensation may be blunted and the lids may already be swollen.

The reassuring part is that the ocular surface usually responds. Neither condition makes dry eye untreatable. They simply mean that treating the eyes alone gets you part of the way, and the rest is covered by the endocrinologist, diabetes team or general practitioner looking after the underlying condition. If you also have a rheumatological diagnosis in the mix, our piece on Sjögren's syndrome and dry eye covers that overlap.

Frequently asked questions

Can thyroid problems cause dry eyes?

Yes, mainly through exposure. Thyroid eye disease pushes the eye forward and retracts the upper lid, so a larger area of surface is exposed, blinks are more often incomplete, and the lids may not close fully overnight. Lubricants help the symptoms but do not narrow the gap causing them, which is why thyroid-related dry eye often needs the thyroid condition addressed too.

Can dry eye be the first sign of thyroid eye disease?

Occasionally. Among 539 patients referred for dry eye evaluation at one centre, 21 were found to have occult thyroid eye disease on orbital echography. None had a prior diagnosis, and none had protrusion, restricted movement or double vision. The clues were redness over the eye muscles in all of them and subtle widening of the lid opening in about half.

Does diabetes cause dry eye?

Diabetes is described as one of the leading causes of dry eye, and reports of diabetes-associated dry eye have increased in recent years. The mechanisms are not settled, but reduced corneal sensation, nerve damage affecting tear production and changes in the meibomian glands are the usual explanations. Poor glucose control affects both the front and the back of the eye.

Will better blood sugar control improve my dry eyes?

It is a reasonable expectation rather than a promise. Poor glycaemic control is described as affecting both the anterior and posterior segments of the eye, so working with your diabetes team addresses the driver in a way that drops cannot. Improvements are gradual, so judge them over months, and keep attending diabetic retinal screening regardless of how your eyes feel.

Educational information only, not medical advice. References: Gupta A, et al. Am J Ophthalmol. 2009;147:919–923; Zhang X, et al. J Ophthalmol. 2016;2016:8201053; Jones L, et al. Ocul Surf. 2017;15:575–628.