Corneal Visual Impairment

#StrongerTogether Brother and sisters after successful corneal grafting

Brother and sisters after successful corneal grafting by Shabana Shahzad for #StrongerTogether photo competition.

Corneal visual impairment encompasses a wide variety of infectious, degenerative, and inflammatory eye diseases that cause scarring of the cornea, the clear window positioned at the front of the eye.

For further details on Corneal Anatomy and physiology: National Eye Institute (USA)

Presence of scar tissue following eye injury, or infection, can result in the cornea becoming cloudy or opaque, termed corneal opacity. The scar tissue scatters the light passing through the cornea, leading to blurred vision or even total loss of sight.

Magnitude

Corneal Opacity accounts for 3.46% of global blindness and 1.65% of global blindness and visual impairment (IAPB Vision Atlas). As a leading cause of blindness in children (Solomon, 2005) and within developing nations, Corneal blindness affects all age groups. As approximately 80% of cases are avoidable (i.e. preventable or treatable), it is essential that ophthalmology maximises a patients’ opportunities for successful visual recovery (Gain et al, 2015). Unfortunately, CB remains an under reported cause of vision impairment (Robaei & Watson, 2014), – with a scarcity of data to increase equitable access to services.

Causes

Corneal opacity may be caused by a wide variety of disorders, including congenital, nutritional, traumatic, infectious, degenerative, and hereditary conditions.

Repeated Trachoma infection causes corneal scarring and is a significant cause of CB in low income settings where trachoma is endemic.

The main causes of CB in children are xerophthalmia caused by Vitamin A deficiency, ophthalmia neonatorum (affecting an est. 1.6% – 12% of all newborns, Matejcek & Goldman, 2013; Teoh & Raynolds, 2003; Wagner RS, Aquino, 20008), and ocular infections such herpes simplex keratitis. In teenagers, keratoconus and chronic allergic conjunctivitis can cause corneal blindness.

Ocular trauma and suppurative keratitis are common causes of corneal opacity and may be under-reported.

Although both onchocerciasis, and leprosy are public health successes these diseases still cause corneal visual impairment (est. prevalence in 2003 of 200 000–300 000 – being 0.5–1% cause of blindness. Courtright & Lewallen, 2003).

Corneal infections, inflammatory disease, and trauma, can be treated or prevented in order to minimise scarring and prevent blindness. However, other conditions, such as keratoconus, or hereditary corneal dystrophies, cannot be prevented, and require long term treatment, such as corneal transplants.

Corneal opacity can result from poor quality cataract surgery. As more cataract operations are performed, there may be an increase in the number of eyes with corneal opacity caused by cataract surgery.

Others

Pterygium Dr.Lawrence Hirst

Pterygium/ Courtesy: Dr. Lawrence Hirst

There are other conditions, such as pterygium that can also impact vision.

Treatment

In significant cases, treatment may only be relieved by a surgical procedure corneal transplantation.

Prevention and treatment plans will depend on specific cause, and the severity and the stage of presentation. Many patients may also require surgical intervention. Prevention and treatment remain dependent on the access to services, resources and trained personnel.

Information consolidated by: Global Alliance of Eye Bank Associations, International Council of Ophthalmology, World Council of Optometry, and eye tissue providers: Eversight International, Lions NSW Eye Bank-AU, LV Prasad Eye Institute Eye Bank -India, Keralink International, and SightLife. With thanks to David Yorston.

References

  1. Courtright P & Lewallen S. Ocular manifestations of leprosy. In: Johnson G, Minassian D, Weale R, West S (eds)The Epidemiology of Eye Disease Arnold: London 2003; pp 306–317. As sited in: Hogeweg. M., & Keunen, J, E, E. Prevention of blindness in leprosy and the role of the Vision 2020 Programme. Eye (2005) 19, 1099–1105. 6701984
  1. Philippe Gain, MD, PhD; Rémy Jullienne, MD; Zhiguo He, PhD; Mansour Aldossary, MD; Sophie Acquart, PhD; Fabrice Cognasse, PhD; Gilles Thuret, MD, PhD. (2015). Global Survey of Corneal Transplantation and Eye Banking. JAMA Ophthalmol. doi:10.1001/jamaophthalmol.2015.4776 Published online December 3, 2015
  2. Eye Bank Association of Australia and New Zealand (EBAANZ). Community and FAQ page. http://www.ebaanz.org/faqs/ As seen on 20.03.2017
  3. Eye Bank Association of America (EBAA) Description of Diseases page. http://restoresight.org/cornea-donation/descriptions-of-diseases/ As seen on 20.03.2017
  4. European Eye Bank Association (EEBA). Donation and Transplantation page. http://www.eeba.eu/article/Donation%2B%2526%2BTransplantation/c/89 As seen on 20.03.2017
  5. (2014). Leprosy. American Association of Ophthalmology. http://eyewiki.org/Leprosy As seen on 18.05.2017
  6. Hall, L., & Pearlman, E. Pathogenesis of Onchocercal Keratitis (River Blindness). Clinical Microbiology Review. 1999 Jul; 12(3): 445–453.
  7. Matejcek , A., & Goldman, M, D. Treatment and prevention of ophthalmia neonatorum. Canadian Family Physician. 2013, November, 59. 1187-1190
  8. Teoh DL, Reynolds S. Diagnosis and management of pédiatrie conjunctivitis, PediatrEmerg Care 2003;19(I):48-55. 4,
  9. Wagner RS, Aquino M, Pédiatrie ocular inflammation. Immunol Allergy Clin North Am 2008;28{l):169-88
  10. Robaei, D., & Watson S. Editorial: Corneal blindness: a global problem. Clinical and Experimental Ophthalmology 2014; 42: 213–214 doi: 10.1111/ceo.12330
  11. Solomon, A. State of the World’s Sight. Vision2020: the Right to Sight 1999-2005. Geneva: World Health Organization. WHO Press, 2005.
  12. Whitcher, P, Srinivasan, M., & Upadhyay, M, P. Corneal blindness: a global perspective. Bulletin of the World Health Organization, 2001, 79 (3) 214-221
  13. IAPB Vision Atlas http://atlas.iapb.org/global-burden-vision-impairment/gbvi-global-cause-estimates/