AGE RELATED CHANGES IN THE EYE?

“ARE WE AWARE ABOUT IT”

Hira Nath Dahal

• Decreased visual field• corneal hypoxia

dermatochalasisptosis

Periorbit and eyelid

skin & soft tissue atrophy

glabellar rhytids

poliosis

orbital septal dehiscene ⇒ herniation of orbital fat

lacrimal gland dysfunction, ↓ed tear production,

meibomian gland disease & goblet cell dysfunction ⇒

dry eye

LID LAXITY ⇒ ENTROPION, ECTROPION

• associated with ageing, • both can be successfully treated with

surgery if they produce discomfort or a threat to vision.

CONJUNCTIVA:

• atrophy & degeneration

• ↓ in no. & height of epithelial cells

• shortening of inferior fornix

• the number of mucous cells decreases leading to

dry eye.

CORNEA:

• ↓ed corneal sensitivity

• ↑ against-the-rule astigmatism

• no. of the people having with-the-rule astigmatism ↓es with

age

• Arcus senilis

• corneal endothelial cell population decreases along with

polymegathism and pleomorphism

fig: Typical age-related changes including sagging of the upper lid, loss of the normal upper lid crease, eyelid wrinkling and arcus senilis.

ANTERIOR CHAMBER:

• depth ↓es with age, causing

• the increment in the refractive power of the eye

(↑ myopia)

• More interference with aqueous outflow

PUPIL AND UVEA:

• senile miosis

• due to

• atrophy of the dilator muscle fibres, or• an increased rigidity of the iris blood

vessels, or• both

• ↓ retinal blur circles and retinal illuminance

less difference in the diameter of the pupil in the light- and

dark-adapted state

less reactive to light

slight ↑ in the latency of pupillary responses

hypertrophy of ciliary muscle

LENS:

• Morphological Changes:

• ↑ in both the mass & dimension of the lens

• axial thickness of the lens ↑es by about 28% by age 70

over that which existed at age 15 to 20 yrs

• the nuclear thickness remains constant while the cortical

thicknesses increase

• the anterior cortex increases by 0.6mm & the posterior,

by 0.4mm

• flattening of the anterior lens surface & conical bulging of

the posterior lens surface

LENS:…

Morphological Changes:

epithelial cells- becomes flatter & density ↓es

lens fibers- total loss or partial degradation of a no. of plasma

membrane & cytoskeletal proteins

cholesterol:phospholipid ratio ↑es

lens capsule- thickens throughout life (collagen type IV vs. I, III,

IV)

LENS:…

Physiological Changes:

Changes to the cellular junctions and alteration on cation

permeability

membrane potential- from –50mV (at age of 20 yrs) to –20mV (at

the age of 80 yrs)

• sodium concentration - ↑es

• Na+:K+ permeability ratio ↑es by six fold

• free calcium level ↑es Ca ATPase inhibited

LENS:…

• Biophysical Changes:

• UV & visible light absorption ↑es

• ↑ 3-hydroxykynurenine glucoside

(3-HKG)

• ↑ yellow-pigmented proteins

• ↑ fluorophores

• thus transmission of visible light & lens transparency ↓es

• the amount of light reaching the retina in a normal 60-

year-old is only about 1/3rd that reaching the retina of a 20-

year old

• amplitude of accommodation ↓es

LENS:…

• Biochemical Changes:

• overall metabolic activity of the lens ↓es

• ↓ glycolytic activity

• ↓ level / activity of antioxidants

• Changes in Crystallins:

• accumulation of high molecular weight aggregates

• some act as scatter points for light

• ↑ed insolubility

• Exaggeration of normal nuclear ageing change• Causes increasing myopia

• Increasing nuclear opacification

• Initially yellow then brown

VITREOUS:

index of refraction of the vitreous

increases ( hypermetropia)↑

syneresis of the vitreous

Increased vitreous floaters

Decreased support to the posterior

lens surface

RETINA AND NEURAL CONNECTIONS:

in the absence of pathology, only little decline in static

visual acuity with age that can not be accounted for by

miosis and increased density of the lens

pathologies that are the major cause of decline in static

visual acuity are cataract, macular degeneration and

glaucoma

• mesopia occurs at higher levels of ambient illuminace in older people

• The arteries and veins of the retina become narrower with age, reducing the flow of blood.

The ageing retina is duller and exhibits a less

responsive light reflex.

The optic disk may be paler also.

This creates a need for more light in order to read or

accomplish other tasks.

SENILE MACULAR DEGERATION

• Warning signs may include:• gradual, spotty loss of detail vision

(dry macular degeneration);

• sudden and severe loss of central vision (wet macular degeneration);

• a need for more light.

RETINA AND NEURAL CONNECTIONS:…

• ↓ contrast sensitivity due to increased lens

fluorescence and light scatter

• with shift of peak sensitivity to lower frequencies

• ↓ in the ability to discriminate colours

• ↓ visual field size and sensitivity

• absolute level of dark adaptation reached by the elderly is

less than that reached by younger individuals

REFRACTIVE STATUS:

• static power of the eye: hypermetropic shift

• cornea: ↑ against-the-rule astigmatism

• anterior chamber: ↑ myopia

• lens: hypermetropia or myopia

• vitreous: ↑ hypermetropia

OCULAR MOTOR SYSTEM:

under scotopic conditions, aging people have difficulty

with fixation

↑ exotropia with age

the range of voluntary eye movements becomes limited

supraduction ↓es with age

↑ tonic vergence with distance heterophoria (esophoria)

↓ positive fusional vergence but same negative

fusional vergence

↓ accommodation with ↑ AC/A ratio & ↓ CA/C

↓ stereopsis

OTHER CHANGES WITH AGING:

• ↓ aqueous secretion

• ↓ resistance to distraction

• ↓ ability to selectively attend to one source of

information in the presence of competing

messages

↓ ability to separate visual events that happen serially declines

with age

↓ dynamic visual acuity (VA for moving targets)

related to ↓ in the rate of smooth following eye movements

↑ variability in visual performance between individuals