Shruthi Mankal

Introduction

Filamentary keratitis is a condition characterised by the presence of filaments on the corneal surface (1). First described in 1882 by Leber, these filaments comprise of mucus, epithelium and cellular debris (2,3).

Although relatively uncommon, filamentary keratitis has strong associations with several ocular surface diseases and systemic conditions, making it a condition frequently encountered in clinical practice (4). Corneal filaments can cause significant morbidity, with the chronicity of the condition and debilitating symptoms significantly impacting quality of life (5). This review provides an overview of the pathophysiology, clinical features, diagnosis and management of filamentary keratitis.

Pathophysiology

Filamentary keratitis is a chronic ocular surface disorder in which the exact pathogenesis remains unclear, though several interacting mechanisms are thought to contribute:

• Tear-film instability, often associated with aqueous-deficient or evaporative dry eye, reduces the protective and lubricating properties of the tear film, leading to epithelial desiccation and localised corneal surface damage (4).
• Mucin and epithelial debris can adhere to these compromised areas of the corneal surface, forming the core of filaments (3).
• Local inflammation may further exacerbate mucin production, subsequent filament formation and predispose to a cycle of ongoing ocular surface injury (2).
• Mechanical shearing from blinking pulls on adherent filaments, causing recurrent microtrauma and delayed resolution (6).

Although the relative contribution of each factor remains uncertain, this multifactorial model is widely accepted in the literature. Risk factors associated with the development of filamentary keratitis include conditions which alter the components of the tear film or compromise the corneal surface (2,4), as outlined in Table 1.

Ocular surface disease and exposure syndromes

Keratoconjunctivitis sicca / Dry eye disease (most common)

Exposure keratopathy

Blepharitis

Neurotrophic keratopathy

Facial nerve palsy

Brainstem injury

Extended contact lens use

Inflammatory disorders

Allergic conjunctivitis

Superior limbic keratoconjunctivitis

Ocular surgery-related

Penetrating keratoplasty

Cataract surgery

Refractive surgery

Systemic conditions (effecting the ocular surface)

Sjogren’s syndrome

Rheumatoid arthritis

Systemic lupus erythematosus

Graft-versus-host disease

Occlusive syndromes

Blepharoptosis

Strabismus

Prolonged eye patching

Medications

Topical (Benzalkonium chloride containing drops, antiglaucoma medications) and systemic (antidepressants, corticosteroids)

Clinical features

Patients classically present with a foreign-body sensation. Other common symptoms include redness, grittiness, discomfort exacerbated by blinking, blurred vision, photophobia, epiphora and blepharospasm (2,7,8).

Investigations

• Slit lamp examination and fluorescein staining (1,5):
  • Firmly adherent filaments on the corneal surface are pathognomonic
    • Their location of the filaments may indicate the underlying cause (for example, filaments in the intrapalpebral space in dry eye disease;  superior filaments in ptosis)
    • Staining with Rose Bengal may improve filament detection
  • Subepithelial opacities may be visible at the base of filaments
  • Corneal epithelial defects are common
• Consider further investigations for underlying diagnosis (1):
  • Schirmer’s test
  • Tear break-up time
  • Meibography
  • Autoimmune work-up (e.g. for Sjogren’s syndrome / rheumatoid arthritis)
  • Medications review

Management

There is no consensus on a stepwise management approach for filamentary keratitis. Treatments namely focus on addressing the patient’s symptoms, treating underlying conditions and restoring the ocular surface to prevent recurrence (2).

Symptomatic relief

Filaments can be removed to provide immediate, albeit temporary symptomatic relief (9). Filaments may be removed under the slit lamp, either using forceps or a cotton swab moistened with saline (2,10). Care should be taken to avoid epithelial disruption at the base of the filament as this may slow resolution (2).

Medical management

Conventional treatments include preservative-free lubricating eye drops and/or ointment to restore the epithelial barrier (2,11). If symptoms persist with lubricants alone, low water-content bandage contact lenses may be a beneficial adjunct, acting to protect the cornea and enable epithelial healing (1,5). Bandage contact lenses should be used in conjunction with topical antibiotics (1). Topical sodium chloride may increase hydration and promote epithelial cell adherence to corneal tissue (1,3), whilst hypertonic saline (5%) may reduce filament formation (4). Other therapeutic options for refractory keratitis include botulinum toxin and autologous serum eye drops (12,13).

Management should also target underlying conditions.  Anti-inflammatory medications including non-steroidal anti-inflammatory drugs (NSAIDs), cyclosporine and corticosteroids may reduce ocular surface inflammation and improve symptoms (1,2). Topical corticosteroids additionally reduce filament adhesion, showing particular benefit in those with dry eye disease and Sjogren’s syndrome. Topical mucolytics such as N-acetylcysteine can help reduce mucus viscosity in the tear film and help prevent filament formation(1).

Surgical management

In cases with significant aqueous tear deficiency, punctal plugs or cautery may be beneficial. Severe cases of filamentary keratitis refractive to medical management may require further surgical intervention, including ocular surface reconstruction (2,14).

Follow up and complications

All patients require follow-up after initiating medical management. Follow-up should focus on assessing treatment response, monitoring for complications and reviewing ongoing risk factors (4). Infectious keratitis is an important complication to monitor for, which ensues from epithelial defects or the use of bandage contact lenses (4). Bandage contact lenses should be removed within 1 month.

References

1. Starns M, Mannis T, Bunya V, Woodward M, Hossain K, Halfpenny C, et al. EyeWiki. 2025. Filamentary Keratitis. Available from: https://eyewiki.org/Filamentary_Keratitis [Accessed 02/12/2025].
2. Weiss M, Molina R, Ofoegbuna C, Johnson DA, Kheirkhah A. A review of filamentary keratitis. Surv Ophthalmol. 2022; 1;67(1):52–9. doi: 10.1016/j.survophthal.2021.04.002
3. Albietz J, Sanfilippo P, Troutbeck R, Lenton AM. Management of Filamentary Keratitis Associated with Aqueous-Deficient Dry Eye. Optometry and Vision Science. 2003;80(6):420–30. doi: 10.1097/00006324-200306000-00007.
4. Ortiz-Morales G, Nordmann-Gomes MC, Navarrete-Azuara M, Loya-Garcia D, Navas A, Ramirez-Miranda A, et al. Filamentary Keratitis: A Persistent Challenge in Ocular Surface Disease. Semin Ophthalmol. 2025;1–9. doi: 10.1080/08820538.2025.2507296.
5. Kowalik BM, Rakes JA. Filamentary keratitis–the clinical challenges. J Am Optom Assoc. 1991; 62(3):200–4. Available from: https://europepmc.org/article/med/1813523#impact
6. Lemp MA, Mathers WD. Corneal epithelial cell movement in humans. Eye. 1989;3(4):438–45. doi: 10.1038/eye.1989.65.
7. Lee SM, Jun RM, Choi KR, Han KE. Clinical manifestation and risk factors associated with remission in patients with filamentary keratitis. Am J Ophthalmol. 2020;218:78–83. doi: 10.1016/j.ajo.2020.05.037.
8. Tsubota K, Kaido M, Yagi Y, Fujihara T, Shimmura S. Diseases associated with ocular surface abnormalities: the importance of reflex tearing. British journal of ophthalmology. 1999;83(1):89–91. doi: 10.1136/bjo.83.1.89.
9. Van Meter WS, Katz D, Cook BT. 28 – Filamentary Keratitis. In: Holland EJ, Mannis MJ, Lee WB, editors. Ocular Surface Disease: Cornea, Conjunctiva and Tear Film. London: W.B. Saunders; 2013: 213–6. Available from: https://www.sciencedirect.com/science/article/pii/B9781455728763000286
10. Chen S, Ruan Y, Jin X. Investigation of the clinical features in filamentary keratitis in Hangzhou, east of China. Medicine. 2016;95(35):e4623. doi: 10.1097/MD.0000000000004623.
11. Ubels JL, McCartney MD, Lantz WK, Beaird J, Dayalan A, Edelhauser HF. Effects of preservative-free artificial tear solutions on corneal epithelial structure and function. Archives of ophthalmology. 1995;113(3):371–8. doi: 10.1001/archopht.1995.01100030127036.
12. Read SP, Rodriguez M, Dubovy S, Karp CL, Galor A. Treatment of refractory filamentary keratitis with autologous serum tears. Eye Contact Lens. 2017;43(5):e16–8. doi: 10.1097/ICL.0000000000000217.
13. Gumus K, Lee S, Yen MT, Pflugfelder SC. Botulinum toxin injection for the management of refractory filamentary keratitis. Archives of Ophthalmology. 2012;130(4):446–50. doi: 10.1001/archophthalmol.2011.2713.
14. Lent-Schochet D, Dhungana A, Kim IJ, Shah H, Farooq A V. Medical and surgical approach to ocular surface reconstruction. Ann Eye Sci. 2024;9(1):1. doi: 10.21037/aes-23-33