What are the filaments of filamentary keratitis composed of?

Degenerated epithelial cells and mucus Filaments are strands of degenerated corneal epithelial cells mixed with mucus that adhere to the corneal surface.

Fibrin strands and red blood cells

Calcium hydroxyapatite crystals

Lipid secreted by meibomian glands

Which symptoms do the corneal filaments in filamentary keratitis typically cause?

Ocular pain and foreign body sensation Because the filaments adhere to the cornea and tug on the epithelium with each blink, they cause pain and a foreign body sensation.

Painless gradual central vision loss

Coloured haloes with night glare

Proptosis with binocular diplopia

What underlies the development of filamentary keratitis?

Altered tear film components or corneal surface abnormality The condition arises from alteration in tear film components, abnormality of the corneal surface, or both, which is why it accompanies many ocular surface diseases.

Direct bacterial invasion of the corneal stroma

Reactivation of herpes simplex in the trigeminal ganglion

Immune complex deposition within Bowman layer

Which condition is a recognised risk factor for filamentary keratitis?

Sjogren syndrome Systemic disease affecting the ocular surface, such as Sjogren syndrome, is listed among the risk factors along with aqueous tear deficiency, corneal exposure, blepharoptosis and ocular surgery.

What is the first-line medical therapy for filamentary keratitis?

Lubricant drops and ointment Topical lubrication with drops and ointment is first line, alongside treating the underlying condition such as dry eye or blepharoptosis.

A six-week course of oral doxycycline

Why is topical 10% N-acetylcysteine used in filamentary keratitis?

It reduces the viscosity of tear film mucin N-acetylcysteine is a mucolytic that thins the mucinous component of the tear film, making filament formation less likely.

It sterilises the ocular surface

It suppresses corneal nerve sensation

It stimulates epithelial cell division

How do topical sodium chloride drops help in filamentary keratitis?

They deturgesce and compact the corneal epithelium Hypertonic sodium chloride drops draw fluid out of the epithelium, deturgescing and compacting it.

They increase aqueous tear production

They enzymatically dissolve the filament core

They block the ocular inflammatory cascade

For how long should a bandage contact lens be left in place in filamentary keratitis?

No more than one month Bandage lenses are a temporary measure and should not be left in place longer than one month, used with artificial tears and prophylactic topical antibiotics.

Indefinitely until filaments recur

What is true of manual filament removal at the slit lamp in filamentary keratitis?

It relieves symptoms only temporarily without medical therapy Filaments can be lifted with jeweller forceps while sparing the epithelium at their base, but this only gives temporary relief and fails without concurrent medical treatment.

A single session is usually curative

It removes the need for topical lubricants

It is best performed with a diamond burr

In which situation is punctal occlusion useful in filamentary keratitis?

When aqueous tear deficiency underlies the disease Punctal occlusion, by temporary plugs or by cauterisation for a permanent solution, helps when aqueous tear deficiency is the underlying problem.

When active microbial keratitis is present

Only in the first week after keratoplasty

When the corneal epithelium is intact and healthy

Filamentary Keratitis: Disease entity and management

DISEASE

Filamentary keratitis is a condition in which strands (“filaments”) composed of degenerated epithelial cells and mucus develop on and adhere to the corneal surface causing pain and foreign body sensation.

The etiology of filamentary keratitis is related to an alteration in the components of the tear film and/or abnormalities of the corneal surface. It is associated with a number of ocular surface diseases and conditions.

Any alteration of the tear film or corneal surface can increase the risk of filamentary keratitis.

Common risk factors include:

Aqueous tear deficiency as in keratoconjunctivitis sicca (or dry eye)
Corneal exposure (e.g. seventh nerve palsy)
Occlusion abnormalities such as blepharoptosis
Ocular surgery (e.g. keratoplasty)
Systemic diseases with effects on the ocular surface (e.g. Sjogren’s syndrome)
Extended use of anticholinergic medications
Superior limbic keratoconjunctivitis
Other ocular surface abnormalities.

MANAGEMENT

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General treatment

Filamentary keratitis treatment can be challenging and is often chronic. Paramount in the overall treatment of filamentary keratitis is the management of underlying conditions such as dry eye syndrome, medication toxicity, and blepharoptosis.

Medical therapy

First-line treatment includes topical therapy with lubricant drops and ointment. Low water-content bandage contact lenses may be helpful temporarily in cases that do not respond to lubrication alone.

The bandage contact lens should be used in combination with artificial tears and prophylactic topical antibiotics. A mucolytic agent such as 10% N-Acetylcysteine can be used topically to decrease the viscosity of the mucinous component of the tear film.

Topical sodium chloride drops may also help by deturgescing and compacting the corneal epithelium. Adjunct treatment with botulinum toxin may be considered in refractory cases. There are case reports and small case series that demonstrate the efficacy of sutureless amniotic membrane grafts to manage this condition.

Another possible treatment for refractory keratitis is autologous serum eye drops. Anti-inflammatory treatment will be needed, such as topical steroids (pulse or chronic), cyclosporine, and lifitegrast.

Medical follow up

Patients should be re-examined shortly after the initiation of medical therapy. Bandage contact lenses should be left in place for no more than one month.

Surgery

Filaments can be removed at the slit lamp using the jeweler’s forceps. Care should be taken to avoid disrupting the epithelium at the base of the filament if possible. Manual removal of the filaments may help in alleviating symptoms temporarily but is only a temporary measure and is not successful without concurrent medical treatment.

Punctal occlusion may also be helpful in cases of underlying aqueous tear deficiency either using temporary plugs or cauterization as a permanent solution.

REFERENCES

Davidson RS, Mannis MJ. Filamentary Keratitis. In: Krachmer JH, Mannis MJ, Holland EJ, editors. Cornea. Vol 1. 3rd ed. Philadelphia: Elsevier/Mosby; 2011. P. 1093-96.
Van Meter WS, Katz D, Cook BG. Filamentary Keratitis. In: Holland EJ, Mannis MJ, Lee WB, editors. Ocular Surface Disease: Cornea, Conjunctiva, and Tear Film. Philadelphia: Elsevier Saunders; 2013. P. 213-16.
Zaidman GW, Geeraets R, Paylor RR, et al. The histopathology of filamentary keratitis. Arch Ophthalmology 1985; 103: 1178-81.
Tanioka H, Yokoi N, Komuro A, et al. Investigation of the corneal filament in filamentary keratitis. Invest Ophthalmol Vis Sci 2009; 50:3696-702.
Gumus K, Lee S, Yen MT, Pflugfelder SC. Botulinum toxin injection for the management of refractory filamentary keratitis. Arch Ophthalmol. 2012 Apr;130(4):446-50. doi: 10.1001/archophthalmol.2011.2713. PMID: 22491914.
Case report on biotissue website; Harthan JS, Sicks LA, “Sutureless Amniotic Membrane (Prokera) for Filamentary Keratitis: A Case Series, J Dry EyeOcc Surf Dis Vol 2(SP1):e10-e16; May 9, 2019.

Test yourself

A few questions straight from this article.

1 / 10 0 correct

What are the filaments of filamentary keratitis composed of?
Filaments are strands of degenerated corneal epithelial cells mixed with mucus that adhere to the corneal surface.
Which symptoms do the corneal filaments in filamentary keratitis typically cause?
Because the filaments adhere to the cornea and tug on the epithelium with each blink, they cause pain and a foreign body sensation.
What underlies the development of filamentary keratitis?
The condition arises from alteration in tear film components, abnormality of the corneal surface, or both, which is why it accompanies many ocular surface diseases.
Which condition is a recognised risk factor for filamentary keratitis?
Systemic disease affecting the ocular surface, such as Sjogren syndrome, is listed among the risk factors along with aqueous tear deficiency, corneal exposure, blepharoptosis and ocular surgery.
What is the first-line medical therapy for filamentary keratitis?
Topical lubrication with drops and ointment is first line, alongside treating the underlying condition such as dry eye or blepharoptosis.
Why is topical 10% N-acetylcysteine used in filamentary keratitis?
N-acetylcysteine is a mucolytic that thins the mucinous component of the tear film, making filament formation less likely.
How do topical sodium chloride drops help in filamentary keratitis?
Hypertonic sodium chloride drops draw fluid out of the epithelium, deturgescing and compacting it.
For how long should a bandage contact lens be left in place in filamentary keratitis?
Bandage lenses are a temporary measure and should not be left in place longer than one month, used with artificial tears and prophylactic topical antibiotics.
What is true of manual filament removal at the slit lamp in filamentary keratitis?
Filaments can be lifted with jeweller forceps while sparing the epithelium at their base, but this only gives temporary relief and fails without concurrent medical treatment.
In which situation is punctal occlusion useful in filamentary keratitis?
Punctal occlusion, by temporary plugs or by cauterisation for a permanent solution, helps when aqueous tear deficiency is the underlying problem.