REVISION 1 : SCHEMATIC EYE

REVISION

SCHEMATIC EYE

SCHEMATIC EYE

mathematical or physical model that represents the basic optical features of the real eye

Optical Fact of Cornea

• Cornea is steep at the centre, flattens towards periphery.

• Corneal power reduced towards periphery.

• Mean radius of anterior corneal surface = 7.8 mm

• Mean radius of posterior corneal surface = 6.7 mm

• Corneal central thickness approximately 0.5 mm.

• Corneal index = 1.376

Multiple Choice

Calculate the power for the anterior cornea.

n air = 1

n cornea = 1.376

r anterior = 8.7 mm

• 48.2 D

• 46.8 D

• 50.2 D

• 52.4 D

Multiple Choice

Calculate the posterior cornea.

n cornea = 1.376

n aqeous = 1.336

r posterior = 6.7 mm

• - 5.97 D

• - 6.00 D

• - 6.25 D

• - 7.00 D

Multiple Choice

Calculate total power for the cornea.

• 42.00 D

• 42.25 D

• 43.00 D

• 43.25 D

Optical Fact of Crystalline Lens

• n at core or nucleus = 1.41

• n at less dense cortex = 1.38

• Anterior radii of curvature = +10mm

• Posterior radii of curvature = - 6mm

Multiple Choice

Calculate the anterior crystalline lens power.

n aq = 1.336

n lens = 1.41

r1 = 10mm

r2 = - 6mm

• 7.00 D

• 7.40 D

• 7.80 D

• 8.00 D

Multiple Choice

Calculate the anterior crystalline lens power.

n aq = 1.336

n lens = 1.41

r1 = 10mm

r2 = - 6mm

• 11.5 D

• 12.0 D

• 12.33 D

• 13.33 D

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