Corneal opacity explained

Corneal opacity
Field:Ophthalmology
Synonyms:Corneal scarring
Symptoms:Loss of vision
Complications:Blindness
Onset:Congenital or acquired
Treatment:Corneal transplantation
Frequency:4th main cause of blindness globally (5.1%).[1]

Corneal opacification is a term used when the human cornea loses its transparency. The term corneal opacity is used particularly for the loss of transparency of cornea due to scarring. Transparency of the cornea is dependent on the uniform diameter and the regular spacing and arrangement of the collagen fibrils within the stroma. Alterations in the spacing of collagen fibrils in a variety of conditions including corneal edema, scars, and macular corneal dystrophy is clinically manifested as corneal opacity.[2] The term corneal blindness is commonly used to describe blindness due to corneal opacity.

Keratoplasty also known as corneal transplantation is the main treatment option for visual improvement in corneal opacity. Other treatments which may improve visual outcome includes optical iridectomy, phototherapeutic keratectomy and keratoprosthesises. Corneal tattooing may be used for improving the cosmetic appearance of the opaque eye.

Types

Depending on the density, corneal opacity is graded as nebular, macular and leucomatous.

Nebular corneal opacity

Nebular corneal opacity is a faint opacity which results due to superficial scars involving Bowman's layer and superficial stroma. A nebular corneal opacity allows the details of the iris to be seen through the opacity. A thin, diffuse nebula covering the pupillary area interferes more with vision than a strictly localized dense leucoma, so long as the latter does not block the whole pupillary area. This is because the leucoma stops all the light which falls upon it, whereas the nebula refracts it irregularly, allowing many of the rays to fall upon the retina where they blur the image formed by the regularly refracted rays.[3]

Macular corneal opacity

Macular corneal opacity is a semidense opacity produced when scarring involves about half the corneal stroma.[4]

Leucomatous corneal opacity (leucoma simplex)

Leucomatous corneal opacity is a dense white opacity which results due to scarring of more than half of the stroma. A number of different presentations of leucomatous corneal opacity exist:

Presentation

Signs and symptoms include the following:

Complications

Congenital corneal opacity that affecting vision will cause amblyopia. That type of amblyopia is known as form-deprivation amblyopia (or amblyopia ex anopsia).[9]

Secondary changes in corneal opacity

Secondary changes may be seen in long-standing cases include: hyaline degeneration, calcareous degeneration, pigmentation and atheromatous ulceration.

Causes

Genetics

Pediatric corneal opacities may be congenital or acquired.

Congenital corneal opacities

Congenital reasons for this condition include:

Acquired pediatric corneal opacities

Acquired reasons for this condition include:

Treatment

Keratoplasty

See main article: Keratoplasty. Keratoplasty also known as corneal transplantation is the main treatment option for visual improvement in corneal opacity. In this, the opaque cornea is replaced with donor tissue. Depending on type and density of corneal opacity different types of keratoplasty may be used such as:[28]

Optical iridectomy

Optical iridectomy creates a clear entrance pupil, improving vision in patients with segmental corneal opacities. An area of clear peripheral cornea can produce retinal images compatible with good visual acuity.[30]

Phototherapeutic keratectomy (PTK)

Excimer laser phototherapeutic keratectomy (PTK) is useful in superficial (nebular) corneal opacities.[31]

Tattooing of scar

Keratopigmentation or corneal tattooing is a procedure used for centuries to improve the cosmetic appearance of corneal scars. Tattooing will not improve vision. For tattooing procedure Indian black ink, gold or platinum may be used.

Techniques

Keratoprosthesis

See main article: Keratoprosthesis. Keratoprosthesis is a surgical procedure where damaged or opaque cornea is replaced with an artificial cornea. Artificial corneas currently in commercial use include Boston keratoprosthesis, Osteo-Odonto-Keratoprosthesis (OOKP), AlphaCor, KeraKlear Artificial Cornea etc.[34] [35]

Epidemiology

Corneal opacity is the 4th main cause of blindness globally (5.1%). Using the World Health Organization's (WHO; Geneva, Switzerland) blindness definition,1 45 million people worldwide are bilaterally blind, of which 6 to 8 million are blind due to corneal disease. In some African areas, nearly 90% of the total blindness is due to corneal pathology.[36]

Europe

The prevalence of congenital corneal opacities (CCO) is estimated to be 3 in 100,000 newborns. This number increases to 6 in 100,000 if congenital glaucoma patients are included. A study of live births in Spain reported that corneal opacities accounted for 3.11% of congenital eye malformations (Bermejo et al, 1998). About 4% of keratoplasties done in the pediatric population in Denmark are due to congenital anomalies (Hovlykke et al, 2014).[37]

India

In NPCB survey (2001–2002) Corneal opacity was the 6th major cause of blindness in India, which accounts for 0.9% of total blind population. In the RAAB (Rapid Assessment of Avoidable Blindness) survey (2006–2007) Corneal opacity including Trachoma was mentioned as the second major cause of blindness, which accounts for 6.5% of total blindness.[38]

See also

Notes and References

  1. Web site: WHO -Priority eye diseases . https://web.archive.org/web/20060322164215/http://www.who.int/blindness/causes/priority/en/index8.html . dead . March 22, 2006 . www.who.int.
  2. Altered Corneal Stromal Matrix Organization Is Associated With Mucopolysaccharidosis I, III and VI . J Alroy, M Haskins, D E Birk. Experimental Eye Research. 2001. 68. 5. 523–30. 10.1006/exer.1998.0622. 10328965.
  3. Book: Ramanjit Sihota . Radhika Tandon . Parsons' diseases of the eye . 978-81-312-3818-9 . 195, 221 . 22 . The posterior segment. 15 July 2015 . Elsevier India .
  4. Book: AK Khurana . Comprehensive Ophthalmology . Jaypee . 121–122 . 6 . Diseases of the Cornea.
  5. Profile of Glaucoma in a Major Eye Hospital in North India. J Das, S Bhomaj, Z Chaudhuri, P Sharma, A Negi, A Dasgupta. Indian Journal of Ophthalmology. 2001. 49. 1. 25–30. 15887712.
  6. Book: Khurana . AK . Comprehensive ophthalmology . 31 August 2015 . Jaypee, The Health Sciences Publisher . 978-93-5152-657-5 . 133–139 . 6th.
  7. Web site: Shachar Tauber . Help for Patients With Corneal Scarring . CRSToday.
  8. Spadea . Leopoldo . Maraone . Giorgia . Verboschi . Francesca . Vingolo . Enzo Maria . Tognetto . Daniele . Effect of corneal light scatter on vision: a review of the literature . International Journal of Ophthalmology . 18 March 2016 . 9 . 3 . 459–464 . 10.18240/ijo.2016.03.24 . 27158621 . 4844042 . 2222-3959.
  9. Web site: Amblyopia.
  10. Web site: John P. Whitcher . M. Srinivasan . Madan P. Upadhyay . Corneal blindness: a global perspective . www.who.int.
  11. Web site: What is trachoma . https://web.archive.org/web/20160922072707/http://www.who.int/trachoma/disease/en/ . dead . September 22, 2016 .
  12. Web site: Onchocerciasis (African River Blindness) . American Academy of Ophthalmology . 2019-11-21 . JHubert H Fam .
  13. Schonberg . Stacy . Stokkermans . Thomas J. . Ocular Pemphigoid . StatPearls . 2020 . StatPearls Publishing. 30252356 .
  14. Web site: Congenital Hereditary Endothelial Dystrophy - EyeWiki . eyewiki.aao.org.
  15. Web site: Posterior Polymorphous Corneal Dystrophy - EyeWiki . eyewiki.aao.org . en.
  16. Web site: Reference . Genetics Home . Congenital stromal corneal dystrophy . Genetics Home Reference . en.
  17. Book: Oxford handbook of ophthalmology . Oxford university press . 978-0-19-881675-1 . 4th . Cornea. 2018 .
  18. Salour . Hossein . Owji . Nasser . Sadeghipour . Alireza . Congenital Corneal Staphyloma . Journal of Ophthalmic & Vision Research . 2009 . 4 . 3 . 182–184 . 23198071 . 3498567 . 2008-2010.
  19. Moshirfar . Majid . West . William . Ronquillo . Yasmyne . Lattice Corneal Dystrophy . StatPearls . 2020 . StatPearls Publishing. 32310559 .
  20. Web site: Granular Corneal Dystrophy: Background, Pathophysiology, Epidemiology . 10 June 2020.
  21. Web site: Cystinosis Hereditary Ocular Diseases . disorders.eyes.arizona.edu.
  22. Cogan . David G. . Kuwabara . Toichiro . Ocular Pathology of Cystinosis: With Particular Reference to the Elusiveness of the Corneal Crystals . Archives of Ophthalmology . 51–57 . en . 10.1001/archopht.1960.00950020053008 . 1 January 1960. 63 . 13810884 .
  23. Book: Creig S . Hoyt . David . Taylor . Pediatric ophthalmology and strabismus. . January 2012 . Saunders/Elsevier . 9780702046919 . 4th.
  24. Barre . Jay . R K . Blach . R S . Wells . Ocular manifestations of ichthyosis . British Journal of Ophthalmology .
  25. Web site: Myra Vita F Ocubillo . Congenital Clouding of the Cornea: Background, Pathophysiology, Epidemiology . 2018-10-10.
  26. Web site: Themes . U. F. O. . Frenkel . Shahar . Congenital Corneal Opacity . Ento Key . 9 November 2016.
  27. Web site: Mucopolysaccharidoses Fact Sheet .
  28. Radhika Tandon . M Vanathi . Noopur Gupta . Rashmi Singh . Corneal transplantation in the modern era . Indian Journal of Medical Research .
  29. Book: Salmon, John F.. Kanski's clinical ophthalmology : a systematic approach. 31 October 2019. 978-0-7020-7713-5. Ninth. [Edinburgh]. 1131846767.
  30. Optical Iridectomy in Children With Corneal Opacities. Kannan Sundaresh, Jitendra Jethani, Perumalsamy Vijayalakshmi . Journal of AAPOS . 2008. 12. 2. 163–5. 10.1016/j.jaapos.2007.10.008. 18155942.
  31. Web site: Phototherapeutic keratectomy . American Academy of Ophthalmology . 2020-03-01 . Antonio Jaime Villarreal Gonzalez, Alejandro Rodríguez-García. .
  32. Web site: Corneal tattooing . American Academy of Ophthalmology . 2020-03-01 . Isdin Oke .
  33. New Surgical Strategy for Corneal Tattooing Using a Femtosecond Laser . Jin-Hyoung Kim, Doh Lee, Tae-Won Hahn, Suk-Kyue Choi . 42110930. Cornea. 2009. 28. 1. 80–4. 10.1097/ICO.0b013e318181a83c. 19092411.
  34. Zarei-Ghanavati . Mehran . Liu . Christopher . Keratoprosthesis: Current Choices and Future Development . Asia-Pacific Journal of Ophthalmology . 2 December 2019 . 8 . 6 . 429–431 . 10.1097/APO.0000000000000268 . 31789643 . 6903338 . 2162-0989.
  35. Web site: Foldable artificial cornea may provide another option for corneal transplantation . www.healio.com.
  36. Web site: Corneal Blindness.
  37. Web site: Congenital Corneal Opacities - Europe. November 2015.
  38. Book: Khurana . AK . Comprehensive ophthalmology . Jaypee, The Health Sciences Publisher . 978-93-5152-657-5 . 478 . 6th . Systemic and community ophthalmology. 31 August 2015 .