Ocular and specular accommodation

Specular accommodation

accommodative stimulus is equal to the reciprocal of the distance from the target to the spectacle plane when patient is fully corrected

Ocular accommodation

vergence of light at the eye when veiwing a distant object through the distance RX minus vergence of light at the eye when veiwing a near object under the actual veiwing conditions

Which patient would have a higher stimulus to ocular accommodation when wearing spectacles: myope or hyperope?

Hyperope; they have to work harder when wearing the glasses to see near objects compared to the myope

Does the power of lenses affect the stimulus of accommodation?

Yes, it changes the stimulus to accommodation.

Who will have diffuculty veiwing near targets earlier in life: hyperope or myope?

Hyperope because they need to accommodated more to see the same target. (A 40-something corrected hyperope has to accommodate more than a 40-something corrected myope when viewing the same near target)

Does the power of a contact lenses change the stimulus to accommodation?

No the CL acts in conjunction with the eye and because there is no gap between the two we do not worry about the image formed by the contact. We treat the eye as an emmetropic eye.

Will a myope have to accommodate more in contacts or glasses?

Contacts

Will a hyperope have to accommodate more in contacts or glasses?

Glasses

When myopes view a near target what type of prism by decentration do they experience?

Base in prism

Do myopes have an higher or lower vergence when veiwing a near target?

Lower. The base in prism effect moves the image of the near target outwards (temporally), reducing the stimulus to vergence (amount eyes need to turn inwards).

Do Hyperopes have an higher or lower vergence when veiwing a near target?

Higher. The base-out prism effect moves the image of the near target inwards (or nasally), thereby increasing the stimulus to vergence (amount eyes need to turn inwards).

Will myopes prefer to do near work in contacts or glasses? Why?

Glasses because they will experience less vergence and less accommodation (the stimulus for both accommodation and vergence is lower in glasses)

A hyperope fitted with plus spectacle lenses centered for their distance PD experiences ______________ when they converge to look at a near target.

Base out prism

Do patients fitted with CLs experience prism by decentration?

No, the pt does not experience prism by decentration because the CLs stay centered on the eye while it converges.

For corrected myopes, it is easier to read in

glasses, compared with CLs.

For corrected hyperopes viewing a near target, the stimulus for both accommodation and vergence is lower in

CLs than glasses.

For corrected hyperopes, it is easier to read in

CLs compared with glasses.