KERATOCONUS-1.pptx

KERATOCONUS-1.pptx

• 1.
  KERATOCONUS Gr. Kerato =cornea, conus =cone-shaped PRESENTED BY : SUJIT K SHAH 2ND YEAR HEI, PU
• 2.
  Definition • It isa non-inflammatory ectatic condition of the cornea in which there is progressive central thinning of the cornea changing it from dome-shaped to cone-shaped.
• 3.
  Discovery Eye Foundation
• 4.
  Etiology • The definitivecause of keratoconus is unknown. It is being believed that some factors produce molecular changes in the corneal tissue which in turn derange corneal biomechanisms and act as precursor for corneal thinning and development of keratoconus formation.
• 5.
  Factors affecting molecularchanges in the cornea include: 1. Heredity 2. Eye rubbing 3. Hormonal changes 4. Other environmental factors include contact lens use, UV light, atopy
• 6.
  Pathophysiology • All layersof the cornea are believed to be affected by KC, although most notable features are the thinning of the corneal stroma, the ruptures in the Bowman layer, and the deposition of iron in the basal epithelial cells, forming the Fleischer ring. •Breaks in and folds close to the Descemet membrane result in acute hydrops and striae, respectively.
• 7.
  Changes occuring inthe cornea • Thinning in corneal stroma • Breaks in Bowmans membrane • Iron deposit in the basal layer of the epithelium • Variable amount of diffuse scarring
• 9.
  Classification • Based onseverity of curvature • Based on the size and shape of cone
• 10.
  Based on severityof curvature Mild keratoconus: <48 D Moderate keratoconus: 48-54 D Severe keratoconus: >54 D
• 11.
  Based on sizeand shape of cone Nipple cone has a small size (<5 mm) and steep curvature Oval cone is larger (5-6 mm) and ellipsoid in shape Globus cone is very large (>6 mm) and globe like
• 12.
  Clinical features Symptoms. Patientpresents with: • Progressive myopia and astigmatism • Vision become progressively blurred and distorted which does not improve fully despite full correction with glasses • Glare • Light sensitivity and ocular irritation • Diplopia and polyopia • Blurred vision when wearing glasses and CL
• 13.
  Sign. The hallmarkof keratoconus is central and paracentral stromal thinning, apical protrusion of anterior cornea and irregular astigmatism. Following signs may be elicited on examination: • Placido disc examination shows irregularity of circles.
• 14.
  •Fleischer’s ring (aniron colored ring surrounding the cone) •Vogt’s striae (stress line caused by corneal thinning)
• 15.
  •Munson’s sign (localised bulgingof lower lid when pts. look down is positive in late stage) •Rizzuti sign(a bright focus of light is seen at the nasal limbus when penlight is projected on the cornea from temporal aspect)
• 16.
  Associations • Ocular conditions,eg. Ectopia lentis, congenital catarct, aniridia, retinitis pigmentosa, VKC, floppy eyelid syndrome • Systemic conditions, eg. Marfan’s syndrome, asthma, eczema, Down’s syndrome and mitral valve prolapse
• 17.
  Investigation • Keratometry. Normalaverage keratometric values are 45 D. In keratoconus , keratometric values are increased and based on severity of ketaroconus is graded. • Corneal topography, i.e. study of shape of corneal surface, is most sensitive method for detecting early keratoconus. • Pentacam. Provides data concerning the anterior and posterior surface and thickness of the cornea.
• 18.
  • An orbscanis the most advanced topography unit. This unit can simultaneosly measure the curvature and thickness of the cornea over the entire surface.
• 19.
  Treatment • Spectacle correctionmay improve vision in early cases. However, later in the course of disease the falling vision may not be corrected by glasses due to irregular astigmatism. • Contact lenses (rigid gas permeable) usually improve the vision in early cases. In early to moderate cases, a specially designed scleral CL (Rose-K) may be useful. • Corneal collagen cross linking with riboflavin and UV-A rays may slow down the progression of disease.
• 20.
  • Intracorneal ringsegments (Intacts) are reported to be useful in early to moderate cases by flattening affect. • Topography guided photorefractive keratectomy (PRK) • Keratoplasty may be required in later stages.
• 21.
  References • A KKhurana, 9th edition , Revised reprint • American academy of ophthalmology • https://quizlet.com/494798224/keratoconus- and-crosslinking-flash-cards/ • https://en.wikipedia.org/wiki/Munson%27s_si gn • https://www.researchgate.net/figure/The-red- arrow-indicates-vertical-ridges-parallel-two- of-the-cone-Vogts-striae-4_fig1_342991632
• 22.
  Thank you