Domains and learning outcomes (C109500)
• One distance learning CPD point for optometrists
Clinical practice
Upon completion of this CPD, ECPs will be able to describe the different causes of nocturnal dry eye disease (s5)
Upon completion of this CPD, ECPs will be able to conduct an assessment and, where appropriate, provide effective treatment for nocturnal dry eye related conditions (s7)

Nocturnal dry eye disease is a condition where dry eye symptoms and signs persist when a person is asleep and can be due to many causes, including problems with the eyelids such as incomplete closure, deficiency in the production of aqueous, sleep apnoea and floppy eyelid syndrome. This article will go through possible causes and management options such as taping the eyelids, lubricants, nighttime eye masks and surgery.

There does appear to be a relationship between sleep and dry eye disease, but it is probably not fully understood. In a study of 1,182 subjects with dry eye disease, researchers found that the more severe the subjects’ dry eye signs and symptoms, the worse they rated their sleep and that those with the worst symptoms were more likely to report problems with waking during the night, rather than difficulties falling asleep in the first instance.1

A 2024 meta-analysis, which examined the association between dry eye and sleep quality, found dry eye patients had worse sleep quality than healthy control subjects.2 However, rather than a sleep disorder causing a dry eye problem, as may be the case with sleep apnoea, it could also be that dry eye causes sleep problems. Dry eye can lead to depression and anxiety, which can in turn lead to poor sleep. Incomplete eyelid closure can make patients more susceptible to being woken by small changes in light levels. Patients with Sjögren’s syndrome may also have dry mouth, which may cause them to wake during the night. 

A randomised controlled trial involving 10 subjects who were deliberately deprived of sleep and a control group of 10 subjects who were not sleep deprived, found those who were sleep deprived had reduced tear volume compared to the control group.3 This suggests that poor sleep may initiate or exacerbate dry eye disease by affecting tear production. In a 2016 study, it was found that when patients have their dry eye treated and/or managed the measurement of their sleep quality improved.4

Nocturnal lagophthalmos is an eyelid condition that occurs when the patient is unable to close the eyelids completely during sleep, and it can lead to signs and symptoms of a dry eye disorder.5 According to a number of studies, incomplete eyelid closure or incomplete blinking is the main cause of exposure keratopathy, as tear film quality is compromised and so the cornea does not get enough protection and nourishment from the tear film.5-9 Nocturnal lagophthalmos should be suspected in patients showing signs of exposure keratopathy, particularly when confined to the inferior cornea and conjunctiva.

Nocturnal lagophthalmos can be classified into three categories with each of them subclassified as i) without corneal and/or conjunctival staining and ii) with corneal and/or conjunctival staining:8

  1. Obvious lagophthalmos – where incomplete closure is visible by assessing the eyelid closure during blinking and closed eye conditions. This can occur for several reasons.
  2. Eyelash-obscured lagophthalmos – thick eyelashes cause incomplete eyelid closure
  3. Overhang-obscured lagophthalmos – from the anterior view, the eyelids look closed, but there is a small gap between the eyelids as the upper eyelid hangs over the lower eyelid.

In the case of nocturnal lagophthalmos, a small study from 2014 showed that there seems to be a considerable association between the sleep position and dry eye symptoms in the contralateral eye, which is theorised to be related to airflow and air quality during sleep.10 Patients sleeping on the right side are likely to have left-eye signs and symptoms of greater significance, compared to the right-eye.7, 8, 10 Therefore, sleep quality is likely to be reduced, causing patient discomfort and irritability during the day, as well as reduced focusing ability and productivity, which can in turn impact their quality of life.7

The aetiology of lagophthalmos can be categorised as proptosis-related, palpebral pathology or idiopathic. Proptosis-related lagophthalmos include those caused by physiological abnormalities, such as intraorbital tumours and endocrine abnormalities such as thyroid eye disease.9 Certain systemic diseases and neurological conditions, facial nerve palsies and trigeminal nerve lesions can cause lagophthalmos so patients must be thoroughly assessed to exclude possible secondary causes of lagophthalmos.9

The second category is palpebral insufficiency or pathology-related, such as due to previous traumatic injury leading to ptosis, or surgery such as blepharoplasty, or periocular conditions such as myasthenia gravis, myotonic dystrophy and external ophthalmoplegia that lead to incomplete eyelid closure and therefore cause dry eye symptoms and signs.8

The third category is a lagophthalmos of idiopathic cause, where the other possible causes have been excluded. Other causes include alcohol consumption and use of hypnotic medications or drugs.7 A case study from 2021 reported lagophthalmos of idiopathic cause, that lead to exposure keratopathy, blurred vision, pain and irritation, foreign body sensation, redness and a sensation of ‘burning’.9

Eyelid taping is a useful and effective way to keep eyes from drying and irritating during sleep, as it prevents the eyes from opening and reduces dry eye symptoms. It can be used to prevent or manage corneal erosions caused by incomplete eyelid closure, ectropion and floppy eyelid syndrome. Tape should be of a medical grade and applied horizontally all the way from inner to outer corner and should cover both eyelids.11-13

It is possible to have weights surgically inserted into the eyelids to improve eyelid closure, but this treatment is mainly used for patients with facial palsies, eg Bell’s palsy. The weights are less effective at night when the patient is lying down and the lids are less affected by gravity.14

Aqueous deficient dry eye disease (ADDE) – This type of dry eye disease is less common compared to evaporative dry eye and mixed dry eye.15 However, when the eyes are closed during sleep, tear exchange is already reduced, so any deficiency in the aqueous production by the lacrimal main and accessory glands could cause more discomfort and dry eye signs.16 During closed eye conditions, due to reduced tear production and reduced tear exchange, dry eye symptoms become exacerbated and patients can experience pain and discomfort during the night and/or upon wakening.

This is why a patient should be assessed for the dry eye disease subtype to aid in a focused treatment plan, as this subtype is harder to manage and can lead to higher rates of morbidity and vision impairment.16

Conventional etiological classification of the aqueous deficient dry eye disease distinguishes Sjögren’s syndrome from non-Sjögren’s syndrome and classifies further depending on the cause (primary/secondary and inherited/acquired).16

It is believed that aqueous deficient dry eye comes before the onset of mixed dry eye, so detection and management of the underlying cause is especially important to increase the likelihood of treatment success.16

Diagnosis of aqueous deficient dry eye disease is achieved by a detailed case history, Schirmer test, tear volume and tear meniscus height and lacrimal gland examination. Other tests like tear stability and osmolarity, ocular surface staining, meibomian gland health examination, nerve status, biomarkers and cytokines and blood workup should ensure that the cause is found and treated.

The management of ADDE includes the use of ocular lubricants, topical immuno-suppressants, secretagogues, autologous serum and punctual plugs.16

As there is a reduced tear exchange during the sleep, and reduced tear production, patients with ADDE require additional lubrication. There are many different artificial tears available on the market and the right treatment requires an individual approach while taking into consideration the patients’ needs. Many ocular lubricants have preservatives, which can sting on instillation and exacerbate dry eye symptoms. For this reason, the use of preservative free ocular lubricants is preferred.

Punctal plugs are an effective and well-established treatment of ADDE, as they prevent the tears from draining and increase lubricant retention. Punctal plugs are inserted into the lacrimal punctae and completely obscure the tear drainage through that point. They are visible on a slit lamp examination and easily removed or replaced.16 The initial plugs used are usually temporary plugs that dissolve over time so that the patient can determine whether or not the plugs were beneficial before deciding on permanent plugs.

There are some contraindications to be aware of when offering punctal plugs as an option so this needs to be taken into consideration. These include allergy to plug material, ectropion and obstruction of the lacrimal canal. If there are active infections such as conjunctivitis or keratitis, or lid inflammations such as blepharitis present, these need to be treated before insertion of the punctal plug.17

Floppy eyelid syndrome

Floppy eyelid syndrome (FES) is where the upper eyelid everts very easily due to tarsal plate laxity. The lid eversions can result in papillary conjunctivitis, burning eyes and redness. The eversions and their side effects are more likely to happen when the patient is asleep due to the eyelid rubbing against the pillow. As the patient is asleep, their lid may remain everted for some time before the patient puts it back into its correct place. It manifests most commonly in middle-aged, overweight males.18

FES is very strongly associated with sleep apnoea and often the first line of treatment for FES is to treat the sleep apnoea. Other management options are change of sleeping position (to avoid contact between the eyelids and pillow or bed), use of artificial tears, use of an eye shield and taping the eyes shut at night.

The use of lubricants may afford some protection from the effects of FES. However, the longest pre-ocular residence time of artificial tears or gel in human eyes has been found to be 81 minutes with averages (depending on the lubricant used) ranging from two minutes to 35 minutes.19 Clearly, longer times would be required to make it through a whole night. However, these measurements were taken on upright, awake patients and the study dates from 2011. 

Longer residence times may be possible in the closed eyes of patients who are lying down, and newer formulations of lubricants may have better residence times. For severe cases of FES that are unresponsive to conservative management, there are surgical options. The eyelids can be tightened by repositioning tendons near the outer canthus, or a full thickness wedge of eyelid may be removed. 

However, a 2010 long term study in Moorfields found a recurrence rate of between 26% and 61% for those patients who had undergone surgical procedures for FES.20 FES is underdiagnosed so consider it as a possibility in cases of recalcitrant papillary conjunctivitis, particularly in middle-aged, overweight men.

Sleep apnoea

Sleep apnoea is the obstruction of breathing during sleep. It occurs because the airways relax and narrow and block airflow. Patients with undiagnosed sleep apnoea get very poor sleep. In milder cases of sleep apnoea, lifestyle changes can help. These changes would typically be losing weight, reducing alcohol intake, cessation of smoking, avoiding certain medications (where possible) and changing sleeping position. Lying on the back is worst for airway constriction and lying on the side is best. If lifestyle changes are not enough to improve sleeping, then a patient may get a CPAP (continuous positive airway pressure) machine, which can keep the airway open at night. 

The mask of the CPAP machine should seal completely around the face. If it does not, then there can be a stream of air towards the eyes which can cause dry eye. The seal may not be complete for a number of reasons. The mask could be an improper fit, in which case the patient should see a technician to get it refitted. The mask may not be cleaned properly, causing a buildup of debris and preventing the mask from sealing correctly. The air pressure setting may be too high causing air to leak out through the seal.

A 2023 meta-analysis of patients with sleep apnoea found that 40% of these patients had floppy eyelid syndrome.21 Patients with sleep apnoea and floppy eyelid syndrome have lower levels of elastic fibres in some organs in the body and the authors of the meta-analysis speculate that this may be the link between the two disorders. 

The analysis also found that 48% of subjects with sleep apnoea had dry eye signs (such as decreased Schirmer I and TBUT, corneal and conjunctival staining) and increased dry eye symptoms (as measured with the OSDI questionnaire); more meibomian gland dropout in sleep apnoea sufferers was noted.

The authors postulate that the intermittent hypoxia caused by unmanaged sleep apnoea may be contributing to dry eye syndrome in these patients. The published research on ocular surface changes with sleep apnoea21-23 does not explicitly state that recruited subjects were not using a CPAP machine, but as subjects’ AHI (apnoea hypopnoea index) scores were high, it could be assumed that subjects were not using CPAP machines. 

There does not appear to be any published research investigating the effect of the use of a CPAP machine on dry eye signs and symptoms in sleep apnoea. If signs and symptoms improved with the use of the machine, then it could be inferred that hypoxia is the primary cause of sleep apnoea-related dry eye. If signs and symptoms do not improve (and assuming the machine is correctly sealed around the face) then there may be some other cause of sleep apnoea-related dry eye.

There are eye masks available to purchase from the Eye Eco Company that are ‘designed to combat dry eyes, night-time lagophthalmos, and other eye irritations’.24 The masks are similar in appearance to soft, large aperture swimming goggles and their premise is that they protect the eyes from the drying effects of incomplete lid closure, air conditioning, heating and CPAP machines. It is possible that they may also prevent accidental lid eversion in patients with FES. While there are satisfied customer reviews of the product available online, there does not appear to have been any research carried out on the effectiveness of eye masks worn overnight for the management of dry eye.

The ideal sleeping position for FES would be supine (lying on the back) as this is the position in which the eyelids are least likely to evert. However, this is the worst position for sleep apnoea, which is often associated with FES. It is difficult to achieve and maintain a change of sleeping position without the use of some kind of physical barrier, e.g., if a patient wanted to sleep on their back, they might have to try attaching tennis balls to the sides and front of their nightwear in order to make it uncomfortable to sleep on either side or on their front. 

Many patients have an almost fixed sleeping position out of necessity due to pre-existing back or shoulder issues. Bandage contact lenses and scleral lenses could be considered in order to protect the ocular surface, but the protection afforded would have to be weighed up against the increased risk of microbial keratitis with the overnight wear of lenses. Surgical solutions have not always shown to be effective in the long term. Taping the eyelids shut, the use of high viscosity ocular lubricants and possibly night-time masks may the best, low-cost management options for many nocturnal dry eye disorders. 

  • Claire Mc Donnell is an optometrist and lecturer at Technological University Dublin. She is also a member of BUCCLE (British and Irish University and College Contact Lens Educators). Her research area is specialist contact lenses. She has presented in the UK, Ireland and Europe on contact lenses and optometric education.
  • Valentina Ivancic is a qualified optometrist from TU Dublin. She is currently working in private practice and interested in dry eye research.

References

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