The document discusses various causes of corneal blindness globally, including infectious diseases like trachoma, vitamin A deficiency, and onchocerciasis. It outlines signs and symptoms, as well as prevention and treatment options. The most common cause of blindness is microbial keratitis resulting from corneal abrasions in developing areas. Simple tools like fluorescein dye and prophylactic antibiotics administered by community health workers can effectively diagnose and prevent infectious keratitis. Overall the document provides an overview of major corneal diseases and blindness issues particularly impacting poor communities worldwide.

1. B Y S . P E R S I S B E N E T T A ,
M . O P T OM 2 N D Y E A R
COMMUNITY
CORNEAL
DISEASES

2. INTRODUCTION
• Blindness from corneal disease is a major ophthalmic public health problem.
• According to the most recent WHO global data on the causes of blindness (2002), ‘corneal opacities’
affected 1.9 million people (5.1% of the total number of bind people).
• If other conditions causing blindness through corneal pathology are included, such as trachoma, vitamin
A deficiency, ophthalmia neonatorum, and onchocerciasis, the number would be significantly higher.
• It also disproportionately affects poor rural communities, because of the increased risk of eye injuries
from contaminated objects such as plant material, limited access to treatment, and higher prevalence of
communicable diseases such as trachoma and onchocerciasis.

3. CAUSES
• There are many different conditions which can damage the structure and shape of the cornea leading to
visual impairment and blindness.
• These include infectious, nutritional, inflammatory, inherited, iatrogenic (doctor-caused), and
degenerative conditions.
• Overall, in low- and middle-income countries, infectious keratitis tends to be the most common
problem.
• However, other conditions, such as trachoma or onchocerciasis, may dominate in some areas.

4. TRACHOMA
• Trachoma, caused by recurrent infection with Chlamydia Trachomatis, causes blinding corneal
opacification through the traumatic effect of entropion / trichiasis and possibly secondary bacterial
infection.
• Once established, trachomatous corneal opacification is difficult to treat: the results of corneal grafting
are often disappointing, in part due to a dry and damaged ocular surface.
• The disease is more common in poor classes owing to unhygienic living conditions, overcrowding
unsanitary conditions, abundant fly populations, paucity of water, lack of materials like, separate towels
and handkerchiefs, and lack of education and understanding about contagious diseases.
• Modes of infection: can be by direct spread, materials transferred and vector transfer.

5. PREVENTION AND MANAGEMENT
• Blinding trachoma can be prevented through the full implementation of the SAFE Strategy (Surgery for trichiasis, Antibiotics
for infection, Facial cleanliness and Environmental improvement to control transmission).
• Topical therapy:
• Tetracycline
• Erythromycin
• Sulfectamide
• Systemic therapy:
• Azithromycin
• Tetracycline
• Doxycycline
• Combined therapy
• Tetracycline

6. XEROPHTHALMIA
• Xerophthalmia, which is caused by vitamin A deficiency and sometimes precipitated by measles, accounts
for more than half the new cases of childhood blindness each year.
• In addition to blindness, these young children are at increased risk of death.
• Prevention is key: vitamin A supplementation, measles vaccination, and nutritional advice have led to a
marked reduction in this condition.

7. ONCHOCERCIASIS
• Onchocerciasis (river blindness) leads to blindness through an inflammatory response to the microfilaria of
Onchocerca volvulus in the retina and the cornea.
• caused by the parasitic worm Onchocerca volvulus.
• It is transmitted to humans through exposure to repeated bites of infected blackflies of the genus Simulium
• Symptoms include severe itching, disfiguring skin conditions, and visual impairment, including permanent
blindness.
• More than 99% of infected people live in 31 African countries.
• In the human body, the adult worms produce embryonic larvae (microfilariae) that migrate to the skin, eyes
and other organs.
• When a female blackfly bites an infected person during a blood meal, it also ingests microfilariae which
develop further in the blackfly and are then transmitted to the next human host during subsequent bites.

8. • Onchocerca volvulus that can lead to visual morbidity via multiple mechanisms including
chorioretinitis, uveitis, and sclerosing keratitis.
• It manifests systemically but is best known for its cutaneous and ocular pathologies.
• Onchocerciasis is the second leading cause of blindness due to infection in the world.
• The associated iridocyclitis is thought to result from this inflammatory response, which in turn can lead
to cataract formation.

9. • O. volvulus involves all ocular tissues. Initially, it can involve the eyelid and conjunctiva, leading to
eyelid nodules and edema, chronic conjunctivitis, chemosis, and phlyctenule-like kerato-conjunctival
lesions.
• Then, by direct invasion, microfilariae infect the cornea and sclera.
• Corneal manifestations include fine interpalpebral sub-epithelial punctate lesions.
• These “snowflake opacities” can lead to a chronic sclerosing keratitis and discrete nummular scars with
stromal edema, corneal infiltration, and neovascularization.
• It is the sclerosing keratitis that contributes to this nematode's permanent blinding effect.

10. • The microfilariae invade the iris and the ciliary body, leading to iridocyclitis that can be severe.
• This can result in correctopia, iris atrophy and extensive synechiae that can result in secondary
glaucoma, as well as early cataract formation.
• Posterior chamber involvement can include chorioretinal lesions.
• Peripapillary chorioretinitis can result in optic nerve dysfunction secondary to optic nerve edema and
optic neuritis, eventually leading to optic atrophy.

13. SIGNS AND SYMPTOMS
• Symptoms are caused by the microfilariae, which move around the human body in the subcutaneous
tissue and induce intense inflammatory responses when they die.
• Infected people may show symptoms such as severe itching and various skin changes.
• Some infected people develop eye lesions which can lead to visual impairment and permanent blindness.
• In most cases, nodules under the skin form around the adult worms.

14. PREVENTION
• There is no vaccine or medication to prevent infection with O. volvulus.
• Between 1974 and 2002, disease caused by onchocerciasis was brought under control in West Africa
through the work of the Onchocerciasis Control Programme (OCP), using mainly the spraying of
insecticides against blackfly larvae (vector control) by helicopters and airplanes.
• This has been supplemented by large-scale distribution of ivermectin since 1989.
• The African Programme for Onchocerciasis Control (APOC) was launched in 1995 with the objective of
controlling onchocerciasis in the remaining endemic countries in Africa and closed at the end of 2015
after beginning the transition to onchocerciasis elimination.
• Its main strategy has been the establishment of sustainable community-directed treatment with
ivermectin (CDTI) and vector control with environmentally-safe methods where appropriate.

15. • Colombia was the first country in the world to be verified and declared free of onchocerciasis by WHO.
• WHO recommends treating onchocerciasis with ivermectin at least once yearly for between 10 to 15
years.
• Control programmes have been very effective in preventing blindness through the mass distribution of
ivermectin and measures to control the Simulium fly.

16. MICROBIAL KERATITIS
• Traumatic corneal abrasion is a common event and is the major risk factor for microbial keratitis in low-
and middle-income countries.
• Microbial keratitis is an infection of the cornea. Corneal opacities, which are frequently due to microbial
keratitis, remain among the top five causes of blindness worldwide.
• The most common cause of microbial keratitis is infection following a corneal abrasion.
• People are at greater risk of corneal injuries from agricultural activities, manual labor, and domestic
work, which can result in infections of the cornea through contact with contaminated objects.
• Microbial keratitis tends to affect people at younger ages, in their prime working years.

17. A community health volunteer practices applying fluorescein to detect corneal abrasions. NEPAL.

18. PREVENTION AND MANAGEMENT
• Opportunities for rehabilitation through surgical procedures are also limited by a lack of donor corneas
for transplants.
• Even when appropriate medical care is available, the corneal scarring that accompanies healing often
results in visual impairment, despite successful antimicrobial treatment.
• An exception is that natamycin has been shown to be more effective than voriconazole for fungal
corneal ulcers.
• These studies demonstrated that village health workers can be trained to diagnose corneal abrasions and
provide prophylactic treatment, and suggested that this simple intervention might be effective.
• Simple topical antibiotic prophylaxis for a few days while the epithelium heals can protect the eye from
developing potentially blinding infection.

19. • These studies also indicate that the following simple tools may be used to identify and prevent microbial
keratitis.
• Fluorescein dye: Applied to the eye using sterile strips or solution, fluorescein will stain corneal epithelial
defects/abrasions.
• Blue torch: A blue light shone onto the cornea with fluorescein dye will highlight a corneal abrasion, which is
visible as a bright green area.
• Loupes: Magnifying loupes are helpful in determining the existence of a corneal abrasion.
• Prophylaxis: Once a corneal abrasion is identified, antibiotic and antifungal ointments should be applied three
times a day for 3 days to prevent infection.
• Education: Health education campaigns inform local community members about corneal infections and
encourage them to seek care in the event of ocular injury.

20. • Causes of corneal blindness
• Infectious
• Bacterial keratitis
• Fungal keratitis
• Viral keratitis
• Trachoma
• Onchocerciasis
• Leprosy
• Ophthalmia neonatorum

21. • Nutritional
• Vitamin A deficiency (Xerophthalmia)
• Inflammatory
• Mooren’s ulcer
• Steven’s Johnson Syndrome
• Inherited
• Corneal stromal dystophies
• Fuch’s endothelial dystrophy

22. • Degenerative
• Keratoconus
• Trauma
• Corneal abrasion predisposing to microbial keratitis
• Penetrating trauma
• Chemical injury
• Doctor-caused (iatrogenic)
• Pseudophakic bullous keratopathy

23. REFERENCE LINK
1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4579989/
2. https://www.who.int/news-room/fact-sheets/detail/onchocerciasis
3. https://www.cehjournal.org/article/corneal-blindness-prevention-treatment-and-rehabilitation/
4. https://eyewiki.aao.org/Onchocerciasis_(African_River_Blindness)