corneal opacities.pptx nebula macula leucoma

causes for corneal opacities

1. DR MAMATA SUBHAKAR R ASSISTANT PROFESSOR DEPARTMENT OF OPHTHALMOLOGY A.C.S. MEDICAL COLLEGE ABNORMALITIES OF CORNEAL TRANSPARENCY & CORNEAL OPACITIES

2. Anatomy of the cornea Gross Anatomy : The cornea is the clear transparent anterior one sixth of the fibrous tunic of the eyeball. The cornea is set into the opaque sclera like a watch glass, the corneo-scleral junction is called the limbus . The cornea has the following features : a smooth brilliant surface. very richly supplied with nerve fibres. has no blood vessels. It is the most powerful refractive medium of the eye

3. Epithelium : is a regular layer of uniform thickness of non- keratinized stratified squamous epithelium . Bowman’s Membrane :is a clear uniform structureless membrane that runs under the epithelium throughout the cornea and ends abruptly at the limbus . Stroma : It forms about 90% of the entire thickness of the cornea. It is made up of regularly arranged lamellae of collagenous fibres associated with some elastic fibres lying in a mucopolysaccharide matrix .

4. Descemet’s Membrane :is a thin fine transparent and highly elastic layer situated posterior to the stroma of the cornea. Endothelium : A single layer of flat hexagonal cells arranged along the inner surface of Descemet's membrane. Nerve Supply : from the naso-ciliary branch of the ophthalmic division of the trigeminal nerve through its long ciliary nerves

5. Functions of the cornea Optical : The cornea is the most powerful refractive medium of the eye (+42Dioptres). Protective : The extreme sensitivity of the cornea is an efficient protective mechanism producing a very quick lid reflex

6. Functions of Cornea Allowing transmission of light due to its transparency Helping in the eye to focus light by refraction Maintaining the structurual integrity of the globe Protecting the eye from infective organisms, noxious substances and UV radiation

7. Transparency of Cornea The following factors are responsible for the transaprency of Cornea:- Relative dehydated state This is maintained by integrity of hydrophobic Epithelium and endothelium The Endothelial pump The osmotic gradient due to hypertonicity of aqueous and tear film

8. Cornea gets it nourishment from Diffusion from aqueous Oxygen in the tear film Capillaries at the limbus 2.Absence of blood vessels and pigment in Cornea 3. Uniform refractive index of all the layers of Cornea and the uniform spacing of the collagen fibrils in the stroma

9. The collagen fibrils are separated by a distance which is less than the wavelength of light so that any irregularly refracted rays of light are eliminated by destructive interference

10. How is the relative dehydrated state of corneal stroma maintained ? The corneal epithelium and endothelium are lipid rich hydrophobic and with good solubility in lipids and water Epithelium has tight junctional complexes which prevent passage of tear fluid into the cornea and loss of tissue fluid from corneal stroma into tear film Corneal stroma is hydrophyllic Endothelium too has junctional complexes and also an active transport mechanism Na+-K+ ATPase pump system

11. Abnormalities of Corneal Transparency With advancing age cornea becomes less transparent and develops dust like opacities due to condensations in the deeper parts of stroma. Also increase in thickness of Bowmans and Decemets membranes

12. The major pathological changes that occur in Cornea are broadly classified as- Keratitis Corneal ulcer Scarring Opacification

13. Keratitis Any type of Inflammation of cornea is called as keratitis Superficial keratitis Keratitis Superficial punctate keratitis Deep keratitis Stromal Endothelitis Or Interstitial keratitis

14. What is the response to Cornea to any Injury? Trauma Infection Surgery If the injury is superficial involving only the epithelium. The Epithelium rapidly regenerates The regeneration is from the epithelial cells present as palisades of Vogt at the limbus. They divide mitotically and replace

15. Injury to the Bowmans membrane. It does not regenrate but replaced by fibrous tissue Injury to stroma also heals by fibrous tissue formation Decemets membrane is very tough and resistant to injury but if there is severe injury . It will develop tears and edges curl in to the Anterior chamber due to elasticity. Decemets membrane can be regenerated partly by endothelium The endothelial cell are closely bound to each other so this layer can be stripped of as a sheet The corneal endothelium does no regenerate but adjacent cells enlarge and fill up the gap

16. Loose epithelium is called epithelial defect. Superficial epithelial defect without any inflammation is called abrasion or erosion Abrasion or erosion will heal in 12-24 hours by regeneration of epithelial cells from periphery A loss of epithelium with inflammation in surrounding cornea is called corneal ulcer. Inflammation will lead out pouring of leucocytes which give yellowish-greyish haze to the cornea surrounding the ulcer. This hazy area is called infiltration

17. Corneal Scar- It is the final outcome of the inflammation. The scar tissue is white and opaque in varying degrees of severity Other non-inflammatory conditions also lead to scarring but the term corneal scarring is reserved for the opacity which follows inflammation All types of infective corneal ulcers involving steoma and Decemets membrane cause corneal scarring and opacifications

18. Bacterial corneal ulcers Fungal corneal ulcers Viral corneal ulcers Protozoal corneal ulcers Parasitic infiltration of the cornea .Corneal Dystrophies

19. Arcus Senilis Arcus guventis Corneal Degeneration Band Shaped keratopathy Climatic droplet keratopathy Salzmann Nodular Degeneration

20. Corneal Opacity Nebula or Nebulamatous corneal opacity –Scarring leading to opacity but the details of iris if seen it is called nebula Macula or Maculomatous corneal opacity- if scarring results in opacity through which iris details are not seen but iris and periphery margins can be made out it is called maculamatous corneal opacity Leucoma or Leucomatous corneal opacity – if the scarring is very dense totally opaque obscuring the view of iris or pupil it is called Leucomatous corneal opacity

21. Adherent Leucoma- If the iris is adherent to the back of the corneal opacity due to healing of perforated corneal ulcer. It is called adherent leucoma Corneairidic scar- If the iris tissue is incorporated into the scar tissue as occurs in healed large sloughed corneal ulcer –it is called Corneairidic scar Anterior Staphyloma- If the iris tissue is seen through the opacity as an ectactic iris it is called Anterior Staphyloma

22. Management of corneal opacity .

23. Corneal Oedema Corneal oedema first affects the epitheliumand seen as steamy in appearance due to accumulation of fluid between the cells Accumulation of fluid between lamellae and around nerve fibres of stroma causes diffuse haziness Long standing oedema causes epithelium to bulge into vesicles or bulla . It is called vesicular or bullous keratopathy Corneal oedema occurs in many inflammatory and degenerative conditions of cornea

24. It is also seen in Acute Glaucoma where the IOP is very high and causes aqueous to seep through the endothelium into the stroma. Striate Keratopathy-STK-It is also a form of Corneal oedema seen after operations with peripheral corneal section. Delicate grey tissues run from the wound due to wrinkling of Decemets Membrane. It will heal gradually as the wound heals

25. Treatment The primary cause of oedema should be eliminated Application of Bandage contact lenses in bullous keratopathy Frequent instillation of concentrated saline solution ointment containing 6% NaCl

26. THANK YOU