ageing and presbyopia Flashcards
(21 cards)
What is presbyopia, and how is it related to the ageing eye?
: Presbyopia is an age-related condition where the eye loses the ability to accommodate or focus on nearby objects. It occurs due to the loss of elasticity in the crystalline lens, which makes it harder for the eye to change its shape for near vision.
What causes presbyopia in the ageing eye?
Presbyopia is caused by changes in the crystalline lens. The lens becomes thicker, less flexible, and more rigid with age, which reduces its ability to focus on nearby objects.
At what age does presbyopia typically begin to occur?
Presbyopia typically begins to occur around the age of 40 as the lens loses its ability to accommodate properly.
What is the role of the ciliary muscle in accommodation?
The ciliary muscle is responsible for changing the shape of the lens to focus on near objects. In presbyopia, the lens becomes less responsive to the actions of the ciliary muscle, reducing accommodation.
What is the amplitude of accommodation, and how does it change with age?
The amplitude of accommodation is the range of focus that the eye can achieve, measured in diopters (D). As a person ages, the amplitude decreases, making it harder to focus on near objects, leading to presbyopia.
: How do Helmholtz’s theory and Schachar’s theory explain presbyopia?
Helmholtz’s theory: Focuses on the loss of elasticity in the lens, preventing it from changing shape to focus on near objects.
Schachar’s theory: Suggests that increased tension in the equatorial zonules prevents the lens from becoming more spherical during accommodation.
What is the near vision triad, and how does it relate to accommodation?
The near vision triad involves three actions when focusing on a near object:
Accommodation: The lens becomes more curved to focus on close objects.
Convergence: The eyes move inward to focus on the near object.
Pupil constriction: The pupils constrict to enhance depth of field.
How does the crystalline lens change as we age?
As we age, the crystalline lens becomes thicker, less flexible, and more rigid, which leads to a reduction in accommodation and the development of presbyopia.
What is the relationship between presbyopia and near vision correction?
As presbyopia develops, the ability to focus on near objects diminishes. This often results in the need for reading glasses, bifocals, or multifocal lenses to assist with near vision tasks.
How does presbyopia affect an individual’s ability to focus on nearby objects?
Presbyopia reduces the eye’s ability to change focus from distant to near objects due to the rigidity of the lens, making activities like reading or using smartphones more difficult.
What is the normal range for the amplitude of accommodation in a young, healthy eye?
In a young, healthy eye, the amplitude of accommodation can range from 10-12 diopters. This decreases with age as the lens loses its flexibility.
How do reading additions work to correct presbyopia?
Reading additions are positive lenses prescribed to help with near vision. For example, a +1.00 D addition is commonly prescribed to compensate for the loss of accommodation caused by presbyopia.
How does the age-related yellowing of the lens affect vision?
As the lens yellow with age, it causes a reduction in blue light transmission, which can affect color perception and contrast, especially in dim lighting.
: What is the effect of lens opacity (e.g., cataracts) on vision in older adults?
Cataracts cause clouding of the lens, leading to blurry vision, glare, and reduced contrast sensitivity. Cataract surgery is a common solution when vision becomes impaired.
What is birefringence, and how is it related to the ageing eye?
Birefringence occurs when light passes through materials like the lens and is split into two components due to differences in refractive index. It can be observed in stress patterns within the lens as a result of age-related changes.
What is the role of ciliary body and zonules in accommodation?
The ciliary body controls the ciliary muscles, which contract to change the shape of the lens for near vision. The zonules are fibers that hold the lens in place and help control its shape during accommodation.
What are entoptic phenomena, and how are they related to the ageing eye?
Entoptic phenomena are visual effects caused by structures inside the eye. Common examples include floaters (shadows of vitreous particles) and phosphenes (flashes of light), which can become more noticeable with age.
What changes occur in the retina as the eye ages?
As the eye ages, the retina can become thinner, and there is a decline in macular function, leading to conditions like age-related macular degeneration (AMD). Peripheral vision may also decline.
What are the benefits of bifocal lenses in presbyopic patients?
Bifocal lenses provide a dual-focus design, with a near-vision segment for close-up tasks and a distance segment for far vision, correcting presbyopia and allowing clear vision at multiple distances.
What is the main difference between monovision and bifocals for presbyopia correction?
Monovision involves correcting one eye for distance and the other for near vision, while bifocals have a single lens with two areas: one for distance and one for near vision. Monovision may take some adjustment for depth perception.
How does cataract surgery help improve vision in older adults?
Cataract surgery removes the cloudy lens and replaces it with an intraocular lens (IOL), restoring clarity of vision and reducing glare. Patients may also need prescription lenses after surgery for near vision tasks.
