Crystalline Lens

Where is the lens located?

between the iris and anterior vitreous humour

The lens comprises of what three major structures?

Lens Capsule, Lens Epithelium (Anterior), Lens Fibres

What is the Lens Capsule?

outer envelope which completely surrounds the lens

What is the Lens Epithelium (Anterior)?

On the anterior surface, there is layer of epithelial cells between the lens capsule and the lens fibres

What is Lens Fibres?

long, thin fibres which are tightly packed together

where does the lens fibres stretch from?

posterior to anterior lens surface

what do lens fibres form

Y sutures

where is a Y suture found

both the anterior and posterior surfaces of the normal lens- it appears as a very faint and small Y shape with cloudy-white colouring

Describe the position of the Y suture if it is located on the anterior surface

upright

Describe the position of the Y suture if it is located on the posterior surface

inverted

where are the lens epithelial cells found

only found between the capsule and anterior lens surface- there are none posteriorly

what is the bulk of the lens made up of?

fibres

Name the 2 categories that the bulk of the lens is categorised into

lens nucleus and lens cortex

what is the lens nucleus

central core of the lens

what is the lens cortex

surrounds the nucleus

what is the equator of the lens?

imaginary band which encircles the lens from the top to bottom

what is the crystalline lens held by

zonules; suspensory ligaments that are attached to both the lens capsule and the ciliary body

what are zonules

suspensory ligaments that are attached to both the lens capsule and the ciliary body

what does the term sclerosis (or sclerotic) mean

hardening of the nucleus

what is Nuclear Cataract

develops within the nucleus (core) of the crystalline lens

name symptoms of nuclear cataract

Slowly developing

Bilateral, but often asymmetrical

Painless blurring of vision

Improvement in unaided near vision

Second Sight of the Aged

Increase in refractive index of crystalline lens

what does Second Sight of the Aged cause

an increase in the refractive index of the nucleus of the crystalline lens

what does an an increase in the refractive index of the nucleus of the crystalline lens lead to?

increase in the dioptric power of the eye which pushes the refractive error in the direction of myopia.

If the patient was either emmetropic or myopic prior to developing the nuclear cataract, we would expect this process to cause the patient’s (unaided) distance vision to ______?

deteriorate

If the patient was hypermetropic prior to developing the nuclear cataract, the patient’s unaided distance vision is likely to _____?

improve

what are the characteristic features of a nuclear cataract

➢ Opacity is most dense in the centre of the lens

➢ Yellow discolouration of the lens nucleus, which progressively darkens to deep brown as the cataract develops.

what is the progressive darkening of the crystalline lens is referred to as

brunescence

what do you need to record for cataract

type and maturity

how is the maturity of cataract assessed

extent, density and brunescence

what appearance of a cataract means its more mature

larger, denser and darker

describe Cortical Cataract

develops within the cortex of the crystalline lens- the region which surrounds the central nucleus

what are the symptoms of cortical cataract

• Gradual onset

• Bilateral, but may be asymmetrical

• May be less effect on central vision- clear nucleus

• Visual Acuity might be normal

• Glare; incoming light scattered by cortical opacities, scattered light reduces retinal image contrast, veiling glare

• Monocular Diplopia; ghost image created due to light scatter, diplopia persists when fellow eye closed. Second image fainter

what are signs of cortical cataract

• Mid-peripheral opacities, clear nucleus

• Cortical Spokes: Straight lines or wedge-shaped opacities

• Direct viewing: cloudy-white

• Radial pattern of cortical spokes

• Advanced: bicycle wheel

what slit lamp technique should be used for cortical cataracts

retro-illumination

how to record cortical cataract

type and extent

what is mixed cataract

combination of nuclear and cortical opacities

what is the most common age-related opacities of the crystalline lens

Mixed (nuclear and cortical)

where does Posterior subcapsular cataracts develop

posterior (i.e. back, close to the anterior vitreous) aspect of the crystalline lens

where do the opacities develop between in posterior subcapsular cataract

between the lens fibres and posterior lens capsule

the opacity in posterior subcapsular cataract is often situated close to what?

visual axis

posterior subcapsular cataracts typically appear to be located near where?

centre of the pupil

what are the symptoms of Posterior Subcapsular Cataract

• Profound effect on vision

• Disproportionate to clinical signs

• Central location of opacity

• Close to nodal point

• Near vision typically affected more than distance vision

➢ Fine resolution for reading

➢ Miosis at near

• Poor vision in bright light- miosis • Glare

what are the signs of a posterior subcapsular cataract

• Direct view: white-yellow opacity, centre of pupil

• High mag: rough, granular texture

• Advanced: Dense plaques

• Retro-illumination: central, dark, reduced transparency

what is an Anterior Subcapsular Cataract caused by

change in the nature of the lens epithelial cells (located underneath the anterior lens capsule) into more fibrous tissue which reduces their optical clarity

where is the opacity located in anterior subcapsular cataract

located close to the anterior surface of the crystalline lens

where does Christmas tree cataract develop

within the cortex or nucleus (but often develops across both)

what is the characteristic shape of Christmas Tree Cataract

individual branches (or needles) protruding from a central zone

describe the branches in Christmas tree cataract

branches sparkle with (often multi-coloured) reflections

how does the effect of christmas tree cataract affect a px’s vision

depends upon the size and location of the opacity

describe the pxs symptoms for Christmas tree cataract

asymptomatic; referral for surgical removal is not required

name 4 risk factors for acquired cataract

increasing age

smoking

UV exposure

positive family history

what cataract is most likely to develop for a smoker

nuclear

what sort of opacities will show for UV light exposure

cortical opacities

name 3 systemic diseases associated with cataracts

Diabetes

Myotonic Dystrophy

Atopic Dermatitis

what cataract are diabetes more likely at risk for

early development of nuclear cataract and classic diabetic cataract

what is classic diabetic cataract

develops within the lens cortex and has a characteristic ‘snowflake’ appearance

describe how diabetic cataract resolve

resolve spontaneously as sugar levels return to normal

what is Myotonic Dystrophy

progressive muscle weakening and disability

describe the specific types of cataracts that myotonic dystrophy patients may have

➢ Young patients (20-30 years old) develop reflective opacities in the lens cortex. These may look similar to a Christmas tree cataract. At this stage, depending on severity, vision may be unaffected.

➢ In later years (40-50 years old), the patient may develop significant wedge-shape cortical opacities and a star-shaped posterior subcapsular cataract. These opacities often severely impair VA.

what is Atopic Dermatitis

form of eczema which causes the skin to become red, itchy and inflamed

In severe cases of Atopic Dermatitis, patients are at risk of developing an?

anterior subcapsular cataract and posterior subcapsular

the use of what increases the chance of cataract?

steroid use

steroid use increases the risk of developing what type of cataract?

posterior subcapsular cataract

what is a Traumatic Cataract

Any form of blunt or or penetrating trauma to the eye carries

how do traumatic cataracts traditionally develop as

star or flower shape

the trauma experienced from a cataract may also carry a risk of?

retinal detatchment

how should traumatic cataracts be managed

referred as an emergency to an Ophthalmologist

what is the management for acquired cataract

always routine; patient can expect to wait several months before their appointment with an Ophthalmologist

When should patients be referred for cataract surgery?

a cataract which is negatively affecting the patient’s quality of life to a significant extent is a good indication for cataract surgery

Should we refer all patients for surgery when we detect any sign of a cataract?

no, its an elective procedure.

Should we only refer patients for cataract surgery when their vision is very poor?

no benefit to Mr Opacity because his VA is very good, however he has significant glare. so refer

What does the operation involve?

Performed as a day-case procedure. typically lasts 15-20 minutes, done under topical anaesthesia

The surgeon will first make an incision in the cornea and tear open the anterior aspect of the lens capsule.

An ultrasound tool breaks-up the patient’s cataractous crystalline lens- this is known as phacoemulsification.

The debris is vacuumed from the patient’s eye, leaving behind the empty lens capsule. Finally, the surgeon replaces the patient’s lens with a new, clear plastic lens

what measurements should be taken for first hospital appointment after our referral?

axial length and keratometry (These measurements enable the Ophthalmologist to calculate the appropriate power of intra-ocular lens)

what is a Congenital Cataract

patients are born with a cataract already in place

how does a healthcare practitioner check for congenital cataract

Check red reflex in each eye (i.e. using retro-illumination)

Congenital cataracts will appear as dark, less transparent areas

what is the most significant risk of congenital catarac

development of amblyopia

what is the childs eye deprived of in childhood cataract

meaningful sensory stimulation due to the lens opacity

what is the management option for congenital cataract

referred to a paediatric ophthalmologist as an emergency; require a telephone call to the local hospital eye department

how are Congenital cataracts treated

treated surgically: the patient’s cataract lens is removed

how is a congenital cataract dealt with after surgery

Contact lenses or spectacles are often used in the meantime to provide the additional 20D

what are common examples of opacities in congenital cataract

blue dot and sutural opacities