Refractory Media Of Eye S4 March 10

VISION; Refractory Media of the Eye Dr. Nisreen Abo-elmaaty Physiology Department

Visible Light ,[object Object],[object Object]

Basic Concepts ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],Focal Point Focal Length Dioptric power of a lens is a measure of its ability to refract light rays. Refractive power = 1 meter / focal length = ? Dioptre. Thus, Dioptric power is inversely related to focal length

The Eye Ball ,[object Object],[object Object]

Ocular Chambers & Fluids ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Vitreous Chamber Aqueous Chamber

Aqueous Humour ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object]

Functions of Aq.H ,[object Object],[object Object],[object Object],[object Object]

Vitreous Humour ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],Refractive Media of the Eye 1.34 Vitreous Humour +20 Dioptres 1.40 Lens 1.33 Aqueous Humour +39 Dioptres 1.38 Cornea 1 Air Refractive power Refractive Index (RI) Medium

The Optical System of the Eye The divergent light rays must pass through an optical system that brings them back into focus. The cornea & lens is the optical system of the eye that focus light rays onto the retina

Cornea ,[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],The Lens

The Lens ,[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object]

Accommodation Reflex (Near Response) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

The lens becomes more spherical during near vision (contraction of ciliary muscle)

[object Object],[object Object],Area 8, Frontal eye field area Superior Colliculus, midbrain Somatic III n. supplying medial recti Convergence Edinger-Westphall n. of III n. Ciliary ganglion + Ciliary ms . +Constrictor pupillae ms . The image falls on fovea centralis ↑ curvature of lens ↑ its refractive power ↑ depth of focus ↓ excess light Prevents aberrations

Pathway of Accommodation reflex:

1 100 60 5 50 40 7 20 30 10 14 20 14 10 10 Amplitude of Accommodation (dioptres) Nearest point (cm) Age (years)

[object Object],[object Object],[object Object]

Cylindrical lens in suitable plane Contact lens. Biconvex lens ( ↑ refractive power) Biconcave lens (diverge) ttt - Unequal curvature of cornea or lens. -short eye ball - Weak lens -long eye ball -Strong lens Cause Focus of rays in one plane is at different distance from that of rays in another plane. Focus behind retina Focus in front of retina Defect Astigmatism Hypermetropia Myopia

[object Object],[object Object],[object Object],[object Object],[object Object]

Control of Pupillary Diameter ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Light Reflex ,[object Object],[object Object],[object Object]

[object Object],[object Object],b -> bitemporal hemianopia (heteronymous hemianopia) c ->homonymous hemianopia Lesion area 17(d) -> homonymous hemianopia of opposite side with macular sparing

Refractory Media Of Eye S4 March 10

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Refractory Media Of Eye S4 March 10