Theme 7: Optical neutralization of the ametropias Principle and value of neutralization. Influence of the vertex distance. Neutralization of the presbyopic.

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Presentation transcript:

Theme 7: Optical neutralization of the ametropias Principle and value of neutralization. Influence of the vertex distance. Neutralization of the presbyopic ametrope Accommodation of the neutralized ametropic eye. Retinal image of the neutralized ametropic eye.

Principle and value of neutralization Goal of neutralization: That the person can see objects at infinity clearly without the need to accommodate Principle of neutralization: The image of an object situated at infinity as seen through a lens should form on the remote point of the eye

Principle and value of neutralization The focal point image of the lens should be situated on the remote point of the eye

Principle and value of neutralization Neutralization of Myopia Concave lens Nearfar

Principle and value of neutralization Neutralization of hyperopia Nearfar Convex lens

Principle and value of neutralization Relation between Refraction (R) and the Power of the Neutralizing Lens (P vp )  v vertex distance (12mm-14mm)

Principle and value of neutralization Relation between Refraction (R) and the Power of the Neutralizing Lens (P vp )

Principle and value of neutralization Neutralization with conventional ophthalmic lens  v = 12mm-14mm Neutralization with contact lens  v  0mm Conventional lens Contact lens

Influence of the vertex distance

f’vpf’vp ’v’v We consider the difference between P vp and R to be significant when it is of the order of 0.25 D which is the normal step between lens powers

Influence of the vertex distance A myope can compensate for small increments of refraction by moving their glasses closer

Influence of the vertex distance A hyperope can compensate for small increments of refraction by moving their glasses away

Neutralization of the presbyopic ametrope First step: Neutralizing the Ametropia Neutralizing for far vision

Second Step: Neutralizing presbyopia Neutralizing for near vision Neutralization of the presbyopic ametrope

Near and Far points conjugated with the near and far points of the eye through the power of the lens

Neutralization of the presbyopic ametrope Near remote and near points conjugated with the far remote and near points through addition

Neutralization of the presbyopic ametrope Example R=-3D; Am vc =1D; d T =-33 cm Range of accommodation of the eye

Neutralization of the presbyopic ametrope Range of accommodation of the eye Far range

Neutralization of the presbyopic ametrope First Step: Neutralizing the ametropia Neutralization for far vision Supposing neutralization with a conventional lens

Neutralization of the presbyopic ametrope Range of accommodation in far vision Near and remote points conjugated with the far remote and near points of the eye through the power of the lens

Neutralization of the presbyopic ametrope Range of accommodation in far vision Far range

Neutralization of the presbyopic ametrope Second Step: Neutralizing Presbyopia Neutralization for near vision

Neutralization of the presbyopic ametrope Range of accommodation in near vision Remote and near points conjugated with the near remote and near points through the power of a lens

Neutralization of the presbyopic ametrope Range of accommodation in near vision Near range

Neutralization of the presbyopic ametrope Range of accommodation in near vision Near remote and near points conjugated with the far remote and near points through addition

Neutralization of the presbyopic ametrope Range of accommodation in near vision Near range

Neutralization of the presbyopic ametrope Range of accommodation in near and far vision There is a blurry vision zone between 1m and 50 cm in front of the eye. An intermediate addition is needed. Far range Near range Blurry vision

Neutralization of the presbyopic ametrope Neutralizing presbyopia. Neutralization for intermediate vision

Neutralization of the presbyopic ametrope Range of accommodation in intermediate vision Near and far points conjugated with the intermediate near and far points through the power of a lens

Neutralization of the presbyopic ametrope Range of accommodation in intermediate vision Intermediate Range

Neutralization of the presbyopic ametrope Range of Accommodation in intermediate vision Far near and remote points conjugated with the intermediate near and remote points through intermediate addition

Neutralization of the presbyopic ametrope Range of accommodation in intermediate vision Intermediate range

Neutralization of the presbyopic ametrope Range of accommodation in far, near and intermediate vision Far range Intermediate range Near range

Neutralization of the presbyopic ametrope Range of accommodation in far, near and intermediate vision The entire zone between infinity and the working distance is covered

Accommodation of the neutralized ametropic eye. Myope A N /A O <1 hyperope A N /A O >1 Si  V =0 (L.C) A N =A O RA N /A O

Accommodation of the neutralized ametropic eye. A neutralized hyperope will accommodate more than an emmetrope The neutralized myope will accommodate less than an emmetrope For a neutralized myope, presbyopia will appear later For a neutralized hyperope, presbyopia will appear earlier.

Retinal image of the neutralized ametropic eye. Axial ametropia P = P o

Retinal image of the neutralized ametropic eye. Refractive Ametropia R + P = P o

Retinal image of the neutralized ametropic eye. Relation with the ametrope without neutralization. The lens augments

Retinal image of the neutralized ametropic eye. Myope: y’ N < y’ UN hyperope y’ N >y’ UN If  V =0 (LC) y’ N = y’ UN Relation with the ametrope without neutralization. The lens augments

Retinal image of the neutralized ametropic eye. Relation with the emmetrope. Relative augmentation of the lens

Retinal image of the neutralized ametropic eye. Axial Ametropia (P = P O ) Myope: y’ N > y’ O hyperope y’ N < y’ O Relation with the emmetrope. Relative augmentation of the lens

Retinal image of the neutralized ametropic eye. Refractive Ametropia (R + P = P O ) Myope: y’ N < y’ O hyperope y’ N > y’ O Relation with the emmetrope. Relative augmentation of the lens