Keratitis

Keratitis is an inflammatory condition that affects the cornea of your eye.
The cornea is the clear part that covers both the iris and the pupil.
Keratitis can be caused by an infection or injury to the eye.
Keratitis is a common condition.
People who wear contact lenses may experience keratitis more frequently than people who don’t wear contacts. In either case, you can take steps to help prevent this condition.
If you do develop keratitis, see your doctor right away.

1. Keratitis Memoona Arshad M. Anas Khan Group 11 - Sem 8th ISM - IUK

2. Cornea The cornea is the transparent part of the eye that covers the front portion of the eye. It covers the pupil (the opening at the center of the eye), iris (the colored part of the eye), and anterior chamber (the fluid-filled inside of the eye). The cornea’s main function is to refract, or bend, light. The cornea is responsible for focusing most of the light that enters the eye.

3. Cornea (Contd..) The cornea is composed of proteins and cells. It does not contain blood vessels, unlike most of the tissues in the human body. Blood vessels may cloud the cornea, which may prevent it from refracting light properly and may adversely affect vision. Since there are no nutrient-supplying blood vessels in the cornea, tears and the aqueous humor (a watery fluid) in the anterior chamber provide the cornea with nutrients. The cornea is comprised of five layers: the epithelium, Bowman’s layer, the stroma, Descemet’s membrane, and the endothelium. The first layer, the epithelium, is a layer of cells covering the cornea. It absorbs nutrients and oxygen from tears and conveys it to the rest of the cornea. It contains free nerve endings. It also prevents foreign matter from entering the eye. The cornea tends to repair itself quickly from minor abrasions. However, deeper abrasions may cause scars to form on the cornea, which causes the cornea to lose its transparency, leading to visual impairment.

4. Cornea Structure The cornea consists of five layers namely: The epithelium Bowman’s membrane Substantia propria or stroma Descemet’s membrane The endothelium

5. Nerve Supply The nerve supply is purely sensory. It is derived from the ophthalmic division of the 5th cranial nerve through the nasociliary branch.

6. Overview Keratitis is an inflammatory condition that affects the cornea of your eye. The cornea is the clear part that covers both the iris and the pupil. Keratitis can be caused by an infection or injury to the eye. Keratitis is a common condition. People who wear contact lenses may experience keratitis more frequently than people who don’t wear contacts. In either case, you can take steps to help prevent this condition. If you do develop keratitis, see your doctor right away.

7. Types of Keratitis Infectious keratitis Bacteria: Pseudomonas aeruginosa and Staphylococcus aureus are the two most common types of bacteria that cause bacterial keratitis.It mostly develops in people who use contacts improperly Fungi: Fungal keratitis is caused by Aspergillus, Candida, or Fusarium. As with bacterial keratitis, fungal keratitis is most likely to affect those who wear contact lenses Parasites: An organism called Acanthamoeba has become more common in the United States in those wear contact lenses. The parasite lives outdoors and may be picked up by swimming in a lake, walking in a wooded area, or getting infected water on your contact lenses. Viruses: Viral keratitis is primarily caused by the herpes simplex virus, which progresses from conjunctivitis to keratitis. Noninfectious keratitis eye injury, such as a scratch wearing your contacts too long using extended-wear contacts wearing your contacts while swimming living in a warm climate, which increases the risk of plant materials damaging your cornea a weakened immune system exposure to intense sunlight, called photo keratitis

8. Etiology It is always exogenous infection commonly due to pyogenic organisms which invade the cornea from outside such as Staphylococcus, Pneumococcus, Pseudomonas, E. coli, etc. The common causative bacterial organisms of corneal ulcer are as follows: Gram-positive cocci—Staphylococcus aureus, S. albus, Streptococcus hemolyticus, S. pneumoniae (Pneumococcus). Gram-negative cocci—Neisseria gonorrhoea (gonococcus), N. meningitidis (meningo-coccus). Gram-positive bacilli—Nocardia asteroides, Corynebacterium diphtheriae (diplobacilli). Gram-negative bacilli—Pseudomonas aeruginosa, Proteus, Klebsiella, Moraxella, Hemophilus, Escherichia coli, etc. Mycobacteria—Mycobacterium tuberculosis, M. leprae. Three pathogens can invade normal intact epithelium: Neisseria gonorrhoeae Neisseria meningitidis Corynebacterium diphtheriae.

9. Keratitis Symptoms Symptoms of keratitis include: red eyes pain and irritation in the affected eye vision changes, such as blurriness or inability to see sensitivity to light inability to open your eye eye discharge excessive tearing Without treatment, keratitis symptoms will progress and get worse. When symptoms appear can depend on the type of keratitis. For example, bacterial keratitis symptoms can appear right away.

10. Healthy Eye VS Keratitis

11. Diagnosis Any suspected symptoms of keratitis should be looked at right away. Your doctor can help make a diagnosis so that you can receive treatments before any complications arise. To diagnose keratitis, your doctor will first talk to you about the history of your symptoms and then look at your eyes. If your eye is sealed shut from an infection, they will help you open it so they can conduct a full examination of the cornea. A slit lamp or penlight may be used during the exam. A slit lamp works by magnifying the structures within your eye so your doctor can get a closer look at any damage being caused by keratitis. A penlight is used for checking your pupil to look for any unusual changes. A stain may be applied to the eye surface to help your doctor look for any other changes. To rule out an infection, your doctor may request lab testing. They will collect either a corneal or tear sample to identify the exact cause of the keratitis. Your doctor may also test your vision with an eye chart.

12. Complications Corneal Opacity Nebula If the corneal scar involves Bowman’s membrane and superficial layers of stroma, the resulting opacity is slight. It is so very faint that the finer details of iris are clearly visible through the opacity.

13. Complications (Contd..) Macula The corneal opacity is dense when it involves about half the thickness of the stroma. The fine details of the deeper structures are observed partially Leucoma A thick white, dense and totally opaque scar results when almost full thickness of stroma is involved. Nothing can be seen through the leucoma.

14. Complications (Contd..) Ectatic Cicatrix [Keratectasia] (ectasia = bulge forwards, cicatrix = fibrous scar) There is marked thinning at the site of ulcer. It bulges forwards even in the presence of normal intraocular pressure. There is no iris adhesion to the cornea. The cicatrix may become consolidated and flat later on

15. Complications (Contd..) Descemetocele [Keratocele] Few ulcers especially those due to pneumococcus and septic organisms extend rapidly. Descemet’s membrane offers great resistance but eventually it may herniate as a transparent vesicle called the descemetocele. It may persist surrounded by white cicatricial ring or it may rupture. Perforation Etiology Sudden strain due to cough, sneez or spasm of orbicularis muscle may cause perforation. Course The aqueous gushes out resulting in the collapse of anterior chamber (IOP = zero). There is forward displacement of iris-lens diaphragm. The only benefit is that the nutrition of the cornea improves, pain is relieved and scarring takes place.

16. Complications (Contd..) Complications of Perforation Prolapse of iris When part of iris protrudes through the ulcer it is known as prolapse of iris.

17. Complications (Contd..) Anterior synechia The adhesion of iris to the posterior surface of cornea is known as the anterior synechia. There is no incarceration of iris within the layers of the cornea. Adherent leucoma It is a leucomatous opacity in which the iris tissue is incarcerated within the layers of the cornea.

18. Complications (Contd..) Anterior staphyloma The adherent leucoma becomes ectatic due to secondary glaucoma or weakness of corneal scar tissue. The ectatic cicatrix in which iris is incarcerated is called anterior staphyloma. Corneal fistula The ulcer ruptures repeatedly due to straining factors. The opening in the cornea is lined by the epithelium therefore it does not heal leading to fistula formation. The aqueous leaks continuously through the corneal fistula. It is usually situated in the centre. Anterior capsular cataract It is formed when the lens comes in contact with the ulcer. Dislocation or subluxation of lens occurs due to stretching and rupture of zonule. Intraocular haemorrhage Sudden lowering of intraocular pressure results in dilatation and rupture of choroidal blood vessels leading to intraocular haemorrhage. Purulent iridocyclitis and panophthalmitis usually occurs in gonococcal infection and hypopyon ulcers.

19. Treatment How your keratitis is treated depends on what is causing it. If you have an infection, you will need to take prescription medications. Your doctor may prescribe eye drops, oral medications, or both. These include: antibiotics for bacterial infection s biocides for parasitic infections antifungals for fungal infection s antivirals for viral infections Not all forms of keratitis infections respond to medications in the same way. Acanthamoeba keratitis can sometimes be antibiotic-resistant, so your doctor may need to look at your eyes again if the infection doesn’t clear up. Also, antiviral medications may not fully eliminate the virus that caused your keratitis; you’ll need to be on the lookout for recurring infections as a result. Noninfectious keratitis doesn’t need medication. You’ll only need a prescription if your condition worsens and develops into an infection. An eye patch can help protect the affected area and encourage the healing process.

20. Outlook When treated promptly, you will likely recover from keratitis. However, complications can arise if it’s left untreated. Untreated keratitis can lead to permanent vision damage. Other possible complications include: corneal scars recurring eye infections chronic (long-term) inflammation sores in the cornea, known as corneal ulcers In severe cases, you may need a procedure known as a cornea transplant. Your doctor will likely recommend this surgery if keratitis causes vision damage or blindness.

21. Prevention While keratitis can happen to anyone, there are steps you can take to help prevent its occurrence. This is especially true if you wear contacts. You can: make sure you don’t go to bed with your contacts in remove contacts before swimming only handle your contacts with clean hands use the right types of cleaning solution, never water or diluted solutions replace your contacts regularly, as recommended by your doctor Preventing viral infections can also help decrease your risk for keratitis. Make sure you wash your hands thoroughly before touching your eyes, especially if you think you’ve been exposed to a virus.

22. References https://www.healthline.com/health/keratitis#prevention https://www.healthline.com/human-body-maps/cornea#1

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