Neurotrophic Keratopathy

Neurotrophic keratitis (NK) is a degenerative disease in which patients experience a reduction or complete loss of corneal sensitivity due to trigeminal nerve impairment.1 Such decreased corneal sensitivity leaves the cornea susceptible to injury and decreases reflex tearing, leading to epithelium breakdown and poor corneal healing. Corneal ulceration, melting, and perforation may likewise be seen in people who have NK.2

NK is classified as an orphan disease with an estimated prevalence of less than 50/100,000 individuals.3 The likelihood of developing this rare disease increases with age and is classified into three stages of increasing severity.4

For those who have NK, the prognosis depends upon a wide range of factors, including the specific cause behind corneal sensitivity impairment, the degree of corneal hypo/anesthesia, and any association with other ocular surface diseases.5 It is generally accepted that the more severe the corneal sensory impairment, the higher the probability of progression.6

What Causes NK?

The trigeminal nerve plays a key role in maintaining the anatomical integrity and function of the ocular surface, as well as in providing corneal sensation.7 Thus, an impairment of the trigeminal nerve can cause morphological and metabolic epithelial disturbances, leading to epithelial defects. 8

Though the disease itself is rare, there are a number of ways one might acquire it. Several ocular and systemic diseases, such as herpetic infections and diabetes, can be causes of NK. Injury and surgery, such as LASIK, can likewise trigger the disease. Indeed, damage at any level of the fifth cranial nerve, from the trigeminal nucleus to the corneal nerve endings, can cause NK in which hypoesthesia (reduction of corneal sensitivity) or anesthesia (loss of corneal sensitivity) occur. 9

How Is NK Diagnosed?

The common factor in cases of NK is loss of corneal sensation, known as hypoesthesia. The diagnosis is therefore based chiefly on decreased corneal sensitivity as well as on a history of conditions associated with trigeminal impairment or presence of persistent corneal epithelial defects or ulcers.

Unfortunately, most people who have NK don’t see an eye doctor as soon as they develop the disease. This is mainly due to the fact that most people with NK have reduced corneal sensation and therefore don’t realize anything is wrong until vision is impaired or the disease progresses. Indeed, there is a marked discrepancy between clinical findings and symptoms.10

When NK is suspected, a comprehensive eye exam is critical, as are additional exam elements including esthesiometry, an assessment of corneal sensitivity using a cotton-tipped applicator or handheld instrument. Other tests may include corneal staining, Shirmer’s testing and possibly a culture to check for infection.

Pharmaceutical and Surgical Treatments for NK

Currently, no specified medical treatment exists for NK.11  Surgical interventions do exist, however there are not any therapies that can improve the impairment of corneal sensitivity or restore visual acuity.12 Proper management is based on clinical severity and aims to promote corneal healing and prevent progression of the disease.13

When more aggressive strategies are needed, doctors may advise the use of amniotic membrane or tarsorrhaphy (surgical lid closure). Looking ahead, several novel treatments may improve the clinical outcome of NK. 14

Scleral Lenses for NK

Due to the high risk of persistent epithelial defects, ulcers, corneal melting, and perforation after surgery, treatment of NK must be conservative.15 To this end, it has been proposed that scleral lenses can help to establish and maintain the integrity of the ocular surface, and may improve visual acuity. Scleral lenses provide a protective shield between the corneal surface and the environment, including the eyelids, which can disrupt the vulnerable corneal surface in NK.

Scleral lenses are different from other contact lenses because they vault over  the entire corneal surface and rest on the white part of the eye, known as the sclera. Liquid fills the space between your eye and the back surface of the scleral lens. This fluid-filled chamber protects and bathes the cornea, giving it time to heal when needed. In this way, scleral lenses protect the ocular surface while optimizing visual function.16 Indeed, these lenses have been shown to be a valid long-term alternative to standard treatment options such as tarsorrhaphy.17

If you have NK, visit your eye doctor to determine the most appropriate management strategy for you.

 


[1] Bonini S, Rama P, Olzi D, Lambiase A. Neurotrophic keratitis. Eye (Lond) 2003;17:989–995.

[2] Sacchetti M, Lambiase A. Diagnosis and management of neurotrophic keratitis. Clin Ophthalmol. 2014; 8: 571–579.

[3] Sacchetti M, Lambiase A. Diagnosis and management of neurotrophic keratitis. Clinical ophthalmology 2014;8:571-9.

[4] Semeraro F. et al. Neurotrophic Keratitis. Ophthalmologica;231:4, May 2014.

[5] Mantelli F, Nardella C, Tiberi E, Sacchetti M, Bruscolini A, Lambiase A. Congenital Corneal Anesthesia and Neurotrophic Keratitis: Diagnosis and Management. BioMed Research International. 2015;2015:805876.

[6] Sacchetti M, Lambiase A. Diagnosis and management of neurotrophic keratitis. Clinical ophthalmology 2014;8:571-9.

[7] Müller LJ, Marfurt CF, Kruse F, Tervo TM. Corneal nerves: structure, contents and function. Exp Eye Res. 2003;76:521–542.

[8] Sacchetti M, Lambiase A. Diagnosis and management of neurotrophic keratitis. Clin Ophthalmol. 2014; 8: 571–579.

[9] Sacchetti M, Lambiase A. Diagnosis and management of neurotrophic keratitis. Clin Ophthalmol. 2014; 8: 571–579.

[10] Sacchetti M, Lambiase A. Diagnosis and management of neurotrophic keratitis. Clin Ophthalmol. 2014; 8: 571–579.

[11] Sacchetti M, Lambiase A. Diagnosis and management of neurotrophic keratitis. Clin Ophthalmol. 2014; 8: 571–579.

[12] Sacchetti M, Lambiase A. Diagnosis and management of neurotrophic keratitis. Clin Ophthalmol. 2014; 8: 571–579.

[13] Sacchetti M, Lambiase A. Diagnosis and management of neurotrophic keratitis. Clin Ophthalmol. 2014; 8: 571–579.

[14] Sacchetti M, Lambiase A. Diagnosis and management of neurotrophic keratitis. Clin Ophthalmol. 2014; 8: 571–579.

[15] Sacchetti M, Lambiase A. Diagnosis and management of neurotrophic keratitis. Clin Ophthalmol. 2014; 8: 571–579.

[16] Weyns M, Koppen C, Tassignon MJ. Scleral contact lenses as an alternative to tarsorrhaphy for the long-term management of combined exposure and neurotrophic keratopathy. Cornea. 2013 Mar;32(3):359-61.

[17] Weyns M, Koppen C, Tassignon MJ. Scleral contact lenses as an alternative to tarsorrhaphy for the long-term management of combined exposure and neurotrophic keratopathy. Cornea. 2013 Mar;32(3):359-61.