1. Degenerative changes in cornea

2. Age related corneal degeneration
Arcus senilis
It is the most common peripheral corneal opacity, frequently occur with predisposing systemic conditions in elderly individuals,occusionaly arcus associated with familial or non familial dyslipoprotaneamia,it is most frequently bilateral ,unilateral condition is rare and my occur in association with carotid disease and ocular hypotony
Sign
Lipid stromal deposit ,form a band in peripheral cornea separated from limbus by clear corneal zone
Corneal guttata
Consist of focal accumulation of collagen on the posterior surface of descement membrane, the lesion appear as warts or excencesrese and are secreted by abnormal endothelial cells

3. Keratoconus
It is progressive disorder, in which cornea assume irregular conical shape,,onset around puberty with slow progressive visual impairment
Both eyes are affected in almost all cases, although involvement commonly asymmetrical
The role of inheritance are not clear,offsprings are affected in about 10% of the cases
AS. Transmission are proposed
Association
Systemic disorder,: down ,ehler danlos,marfan syndroms,osteogenesis imperfecta and mitral valve prolapse
Ocular association: vernal keratocongectivitis,aniridia,ectopia lentis,retinitis pigmentosa,rigid contact lens wear and constant eye rubbing

4. Presentation
Unilateral visual impairment due to progressive myopia and astigmatism which subsequently become irregular
Patient report frequent changes of spectacle
As a result of asymmetrical nature of the disease the fellow usually have normal vision with negligible astigmatism which however increase as the condition progress
Sign
1-early
apical corneal protrusion
Retinoscopy show irregular seizer reflex
Slit lamp show very fine vertical deep stromal striae called vogt lines
Corneal topography is the most sensitive method for detection of early keratoconus

5. 3-Acute hydropes 2-Late sign Progressive corneal thinning
Progressive visual deterioration
Bulging of lower lid in down gaze (munson sign)
Epithelial iron deposit (fleischer ring) my surround the base of the cone
3-Acute hydropes
Caused by acute influx of aqueous humor into the cornea as aresult of rupture of descement membrane, causing
Sudden drop of V.A.
Discomfort and watering
Breaks usually heals within 6-10 wks and corneal edema resolved leaving variable amount of stromal scar
Treatment of acute phase is with hypertonic saline, patching or soft bandage contact lens
Permanent treatment:keratoplasty

6. Contact lens Treatment of keratoconus Therapeutic indication
Spectacles. in early cases to correct mild irregular astigmatism
Rigid contact lens. when astigmatism cannot corrected by spectacles
Keratoplasty. In advanced progressive cases
Contact lens
Therapeutic indication
1-optical:
A. irregular astigmatism
B. superficial corneal irregularity
C. anisometropia, which my fallow cataract surgery

7. 2-promotion of epithelial healing
A. persistent epithelial defect ,to protect the regenerated epithelium from constant rubbing by blinking
B. recurrent corneal erosion
3- pain relief
A. bulbous keratopathy which condition occur as aresult of loss of endothelial cell leading to development of corneal edema which when rapture cause sever pain with blinking as following complicated cataract surgery
B. wet filamentary keratitis as in brain stem stroke
C. Protection of corneal epithelium from aberrant lashes
3-preservation of corneal integrity
A. descematocele which sever corneal thinning which intended to rupture
B. splinting and apposition of small corneal wound till healing

8. 4-miscelenous indication
A.Ptosis prop as in patient with ocular myopathy
B. maintenance of fornices in eyes with cicatrizing conjunctivitis
C. drug delivery
Complication
Conjunctival
allergic conjunctivitis
Giant papillary conjunctivitis
Corneal complication
Epithelial edema due to hypoxia
Corneal vascularization due to hypoxia
Sterile corneal infiltrate
Microbial keratitis
Corneal warping, sever and permanent astigmatism my be caused by chronic corneal hypoxia