corneal diseases

Corneal Disease

Lecturer: Miss.Yumna Tariq M.Phil. Scholar ( Optom)

Congenital abnormalities of cornea1. Microcornea:• a congenital condition• the corneal diameter is <10 mm (or <9 mm in

newborns). • Unilater or bilateral• It is believed to arise due to arrest of growth of the

cornea in the 5th gestational month.• Hypermetropic

2.Megalocornea:• Large corneal diameter > 13mm• Bilateral• Usually X-linked• 90% of the affected individuals are Males• High Myopia and Astigmatism

Megalocornea

c. Cornea Plana:Severe decrease in corneal curvature resulting in reduced refractive power of the cornea ( 20D – 30D)• Rare• Bilateral• Hypermetropia

Normal cornea vs cornea plana

Corneal ectasias:Ectasia: • an enlargement, dilation, or ballooning effect

Corneal ectasia?• are a group of uncommon, noninflammatory, eye disorders

characterised by• bilateral thinning of the central, paracentral, or peripheral

cornea

• Most common1. Keratoconus2. Keratoglubous3. Pellucid marginal degeneration

1.Keratoconus:

• a progressive, non- inflammatory,• bilateral, asymmetric disease• characterized by paraxial stromal thinning and weakening

that leads to corneal surface distortion.• Onset = around puberty, slow progression thereafter until

the 3rd & 4th decades of life• Role of heredity?• Most pts. do not have positive family Hx.

Presentation:

1. Reduce visual Acuity2. Frequent changes in spectacle prescription3. Glare4. Ghost images5. Monocular Diplopia

Signs:1. Progressive myopia and irregular astigmatism2. Rizzuti sign -------> conical reflection on the nasal cornea when

a penlight is shone from the temporal side3. Munson sign --------> bulging of Lower Eyelid in Down Gaze4. Oil droplet reflex -------> by Direct Ophthalmoscopy5. Scissor Reflex --------> Retinoscopy6. Bowmans scarring ------- > due to previous hydrops7. Stromal vertical, fine lines (Vogt Straie) --------> Slit Lamp8. Epithelial Iron deposits ( Fleischer Ring) ----> S/L cobalt blue

filter9. Apical Scarring ------> at the apex of the cone10. Acute hydrops ----> rapture in Descmet’s membrane 11. Prominent corneal Nerves

External Signs:

Slit Lamp findings:

Retro illumination sign

Munson sign & Rizzuti Sign:

&

Scissor reflex & oil droplet reflex

&

Fleischer ring & Vogt Straie:

&

Hydrops & Corneal Nerves

&

Detection of Keratoconus:1.Retinoscopy2. Slit lamp3. Keratometer4. Corneal Topography

CLASSIFICATION OF KERATOCONUS

Classification based on shape of Cone:

• Nipple Shape:

small diameter ( 5mm)

round shape

Easiest to fit with CL

• Oval Cones: Large dia ( > 5mm)

Often displaced inferiorly

More difficult to fit wit Cl

• Globus Cones: Largest Dia ( >6mm)

75% of the total cornea is affected

Most difficult to fit with lenses

ON THE BASIS OF Keratometer Reading:

Grades of Keratoconus:

• Mild K ( < 48 D)• Moderate K ( 48D – 54D)• Severe K ( > 54D )

Associations:

Systemic:• Downs Syndrome• Marfan’s Syndrome• Turner syndrome • Ehlers- Danlos Syndrom etcOcular :• Persistent Eye rubbing• Aniridia• Retinitis pigmentosa

Treatment:• Spectacles:• RGP ( Rigid Gas Permeable Contact Lenses)• Keratoplasty

2. Keratoglobus:

“the condition in which the entire cornea is abnormally thin”

Or Generalized thinning of cornea

Onset: at birthSigns: ectasia is Generalized acute hydrops occur less commonly Cornea is more prone to rupture on traumaManagement: • CL ------ scleral CL• Surgery ------poor results

3.Pellucid marginal degeneration:

• Inferior corneal thinning ( sometimes superior cornea too)• Bilateral• Onset: 20 years to 40 years• Cresent shape band of inferior cornea extending from 4 – 8 o’clock• Intact epithelium • No fleischer rings, no Vogt straie• High Astigmatism ( against the rule)

Treatment:Spectacles: not usefullCL: RGP CLSurgery: keratoplasty

Thanks.