Keratitis
Keratitis is an inflammation of the cornea. This eye condition is diagnosed when certain signs are found on the eye exam: corneal swelling (edema), infiltration of inflammatory cells, and ciliary congestion.
In this article:
- What Is keratitis?
- Symptoms
- When to see a doctor
- Types of keratitis
- Infectious keratitis
- Noninfectious keratitis
- Causes
- Risk Factors
- Complications
- Prevention
- Caring for your contact lenses
- Preventing viral outbreaks
- Is keratitis contagious?
- Diagnosis
- Allergic keratitis
- Bacterial keratitis
- Pseudomonas keratitis
- Nocardia keratitis
- Atypical mycobacteria keratitis
- Viral keratitis
- References
What Is keratitis?
Keratitis is an inflammation of the cornea. This eye condition is diagnosed when certain signs are found on the eye exam: corneal swelling (edema), infiltration of inflammatory cells, and ciliary congestion.
Keratitis is caused by infectious and non-infectious diseases, which may be systemic or localized to the ocular surface. Amongst the types of keratitis, “microbial keratitis” accounts for the majority and is primarily a cause of major concern in developing countries. However, noninfectious keratitis is also a serious problem for vision.
The eye has a strong defense to deal with most of the infectious agents; however, there exist some organisms which can evade this line and cause infection. The corneal epithelium is an important barrier protecting the inner parts of the eye. Most of the organisms cannot penetrate intact epithelium, so they cannot cause keratitis in the absence of injury. Neisseria meningitides, N. gonorrhea, Corynebacterium diphtheria, Haemophilus influenzae, and Listeria species are the virulent organisms with the potential to penetrate even intact epithelium and cause keratitis.
Ulcerative keratitis was significantly higher among contact lens wearers. There is also increased concern for keratitis following eye surgery.
It is important to identify factors that cause a chronic injury of the eye such as ingrown eyelashes, foreign body and improper eye lens care causing scratching.
Fungal corneal ulcers are very common in developing nations. However, herpes virus is a major concern in developed nations.
Seasonal allergy is a significant treatable condition preventing development of the corneal ulcers.
Symptoms
The most common complaints of patients with keratitis include:
- eye redness,
- eye pain,
- feeling of “sand in the eye” – an irritation of the eye
- photophobia
- blurry vision
When to see a doctor
Types of keratitis
Inflammation of the cornea can happen with or without infection. While the symptoms can be similar, it is important to know if the infection is present for the management and treatment of keratitis.
Infectious keratitis
- Bacterial keratitis – including Pseudomonas, Staphylococcus, Streptococcus, Moraxella, Nocardia, and Atypical Mycobacteria
- Protozoal keratitis – including Acanthamoeba
- Keratitis by Oomycete – Pythium keratitis. Morphologically, very similar to fungi; however, unlike fungi, the cell wall here contains (1-3) (1-6) beta D glucan
- Fungal keratitis – This includes infection by Aspergillus, Fusarium, Candida (yeast), Cladosporium, Alternaria, Curvularia, and Microsporidia
- Viral keratitis – This includes infection by Herpes simplex virus (HSV), Herpes zoster virus (HZV), Adenovirus, and others.
- Parasite infestation – Onchocercal keratitis (sclerosing keratitis).
Noninfectious keratitis
- Local causes – includes trichiasis, giant papillae, foreign body
- Peripheral ulcerative keratitis
- Collagen vascular diseases, like rheumatoid arthritis, granulomatosis with polyangiitis, polyarteritis nodosa, relapsing polychondritis, systemic lupus erythematosus, and others
- Neurotrophic corneal ulcer (post- herpes zoster ophthalmicus, trigeminal nerve damage due to surgery or tumor)
- Xerophthalmia
Causes
There are many causes of the keratitis:
- Bacterial infection
- Viral infection
- Parasitic infection
- Dry eye syndrome
- Allergy
- Eye surgery
- Contact lens
- Trauma
- Systemic inflammatory diseases
Rheumatoid arthritis (RA) is known to cause the spectrum of ocular abnormalities:
- Severe dry eye
- Scleritis
- Sclerokeratitis
- Peripheral ulcerative keratitis.
History of small joint pain with or without finger deformities are important clues to reach the diagnosis. If systemic findings are not correctly identified, a corneal perforation and severe systemic disease will develop with time.
Wegner granulomatosis (WG)/granulomatosis with polyangiitis is a connective tissue disorder (necrotizing vasculitis) that is known to cause eye disease:
- Keratitis
- Episcleritis
- Scleritis
The patient can present with peripheral ulcerative keratitis. A careful examination might reveal a depressed nasal bridge or destruction of the pinna of the ear. History of nasal bleed is an important symptom. An early diagnosis is important to decrease not only morbidity but also mortality.
Other systemic conditions causing keratitis are:
- Systemic lupus erythematosus
- Relapsing polychondritis
- Polyarteritis nodosa.
When the keratitis and corneal ulcer is found on exam, it is important to take a correct diagnosis in order to stop the progression of the disease.
Risk Factors
Risk factors are any conditions that disrupt the corneal integrity and open it up to the invasion of the outside agents. Various systemic causes can result in alteration of the local ocular surface milieu and subsequent development of severe dry eye and keratitis.
As viral keratitis is transmitted through eye touching, it is important to implement good hygiene in schools and daycares. Crowded spaces with shared objects (shopping cards, sport venues, concerts etc) is a risk factor in transmission of adenoviruses and all other viral diseases including COVID-19.
Contact lens wear continues to be a significant risk factor for the development of acute sight-threatening corneal infections (microbial keratitis). Contact lens wear can predispose to microbial keratitis, but it also causes “sterile” inflammatory responses. Finally, compromise to unique defenses that protect the eye during eye closure may contribute to the reasons why extended contact lens wear is a risk factor for infection versus daily wear. Indeed, it is known that the biochemistry of the closed eye ocular surface differs from that of the open eye, and these differences likely relate to defense against microbes.
Complications
While keratitis is easy to treat when identified on time, untreated inflammation of the cornea leads to ulcers which may cause:
- Toxic iridocyclitis
- Secondary glaucoma
- Descemetocele
- Perforation of corneal ulcer
Sequelae of Corneal Perforation can be dramatic and affect an ability to see:
- Iris prolapse
- Anterior dislocation of lens
- Anterior capsular cataract
- Corneal fistula
- Purulent uveitis
- Intraocular hemorrhage
- Corneal scarring- nebula, macula, leucoma, adherent leucoma
- Keratectasia
- Disorganized anterior chamber
- Autoevisceration
- Phthisis bulbi
Missed or untreated keratitis leads to blindness.
Prevention
Considering the majority of cases of keratitis due to trauma. So, it is advisable to use eyeshields when performing jobs that can have tiny shavings or sand fly into the eye.
A good follow-up and care after an eye surgery will help prevent bacterial keratitis.
People who develop recurrent HSV keratitis (more than 3 episodes in a year) should take oral antiviral prophylaxis for 1 year.
Xerophthalmia develops as a result of malnutrition. Vitamin A supplementation, as per WHO guidelines, need to be recommended as soon as possible.
Caring for your contact lenses
Extended/overnight lens wear remains the most significant risk factor for infection. Clearly, infection of the cornea requires a microbe(s). During contact lens wear microbes can enter the eye from the wearer’s lid margins, their fingers upon lens insertion (or removal), or via the contact lens, from the care solutions, or the storage case.
Proper use of a contact lens disinfection system (if it is effective), may reduce the probability of contamination, at least via some of these avenues. Generally speaking, good hygiene minimizes microbial contamination, and reduces the risk of infection and disease in other tissues and circumstances. Indeed, hand washing is considered one of the most effective preventive approaches against infectious disease in general.
Preventing viral outbreaks
Considering the contagious nature of the disease, maintenance of personal hygiene has a very important role in preventing its transmission.
Is keratitis contagious?
While viral keratitis is extremely contagious, mechanical keratitis is not contagious at all. That is why it is important to see a specialist who will determine the cause of keratitis.
Diagnosis
Diagnosis is first suspected by the clinical signs, such as eye redness, tearing and irritation. The keratitis diagnosis is made by an ophthalmologist who performs an eye exam. The routine protocol for any corneal ulcer is to look for the characteristic features of the ulcer, followed by corneal scraping to identify the causative organism.
Allergic keratitis
Allergic disease of the eye does not stop on one specific structure – it usually affects all external surfaces of the eye and even eyelids. Allergic keratoconjunctivitis and vernal conjunctivitis are the common allergy eye diseases. It is important to have a good history.
Usually, there is a clear connection of the symptoms (such as itchy eyes, red and swollen eyes) with the history of the exposure. For example, if the eyes itch and become red after your child pets a cat, you need to see an allergist who will do the allergy skin scratch test. treating the allergy is of upmost importance, as this will eliminate chronic use of the medications and eye complications, such as keratitis.
Bacterial keratitis
Staphylococcal keratitis can be either because of direct invasion of the organism or because of staphylococcal antigen. Staphylococcal antigen-induced keratitis is usually affecting the peripheral cornea and hence the name ‘marginal keratitis.’ Marginal keratitis is invariably associated with staphylococcal blepharitis.
In early-stages of Gram-positive infection, the cuff of cellular infiltration is noted around the corneal focus of infection and is not diffuse, unlike Pseudomonal keratitis.
Pseudomonas keratitis
In early-stage, diffuse and dense corneal cellularity is noted much beyond the focus of infection. Pseudomonas is a gram-negative bacteria with predominantly greenish-yellow corneal infiltrate and extensive collagenolysis. The symptoms are more acute and rapidly progressive. Corneal melt might progress to corneal perforation or endophthalmitis if not taken care of in the early stages.
Nocardia keratitis
Nocardia is a weakly acid-fast bacteria (Modified Kinyoun stain). There may be a history of either trauma or intraocular surgery with corneal infiltrates usually starting adjacent to the surgical incision site. The infiltrates are granular, superficial to mid-stromal with the wreath-like pattern often in the mid-peripheral cornea.
Atypical mycobacteria keratitis
The Atypical mycobacteria are acid-fast bacilli causing keratitis with a protracted course. There may be a history of trauma with corneal foreign bodies or a history of corneal surgery (LASIK). The onset of keratitis in trauma cases can vary from days to weeks; however, the post-LASIK cases usually have an average time of presentation of 3.4 weeks. The disease has a waxing and waning course. The corneal infiltrate has a typical cracked windshield appearance with radiating lines in the middle one-third of the corneal stroma.
Viral keratitis
Dual staining with Rose-Bengal and fluorescein stain is a very important clinical tool to make a diagnosis of HSV epithelial disease. Fluorescein stain makes the dendrites and geographical ulcers more evident by staining the base of ulcer, and Rose-Bengal stains the cells at the margin of the ulcer, which are loaded with viruses. The diagnosis of epithelial disease is mostly clinical.
References
Keratitis following laser refractive surgery: Clinical spectrum, prevention and management. Das S, Garg P, Mullick R, Annavajjhala S.Indian J Ophthalmol. 2020 Dec;68(12):2813-2818. doi: 10.4103/ijo.IJO_2479_20.PMID: 33229656 Free PMC article. Review.
Parasitic keratitis – An under-reported entity. Khurana S, Sharma M.Trop Parasitol. 2020 Jan-Jun;10(1):12-17. doi: 10.4103/tp.TP_84_19. Epub 2020 May 20.PMID: 32775286 Free PMC article.
Scleritis and peripheral ulcerative keratitis. Galor A, Thorne JE.Rheum Dis Clin North Am. 2007 Nov;33(4):835-54, vii. doi: 10.1016/j.rdc.2007.08.002.PMID: 18037120 Free PMC article. Review.
Keratitis. Singh P, Gupta A, Tripathy K.2021 Aug 10. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan–.PMID: 32644440 Free Books & Documents. Review.
Pathogenesis of contact lens-associated microbial keratitis. Fleiszig SM, Evans DJ.Optom Vis Sci. 2010 Apr;87(4):225-32. doi: 10.1097/OPX.0b013e3181d408ee.PMID: 20190671 Free PMC article. Review.