Stage 1 Visit 1 - Cataracts

What features does the lens have to facilitate its transparency and low light scatter?

Absence of BV, lack of cell organelles and tightly packed and regularly shaped fibres

Why is scatter minimised although the AH has a different refractive index to the lens fibres?

Minimised space between lens fibres due to a hexagonal structure which allows them to be packed in a dense fashion.

oxidative stress with regards to crystalline lens

it alters the proteins that allow lens fibres to have the structure needed for transparency - form of protein denaturation

what does protein denaturation cause?

Increased opacity due to increased light scatter

What causes increased lens thickness

Cortical fibre production (continually added throughout life) in the axial and sagittal planes alongside AGE

• This occurs around the lens nucleus

maximum size of a nuclear cataract

6mm equatorially and 4mm sagittally.

nuclear fibres are maximum at birth - more aren’t added

which types of cataract can you assess with a ret

PSC and Cortical lens opacities - can assess location, shape and density as the opacities are retroilluminated by the ret reflex

Can assess density of nuclear cataract but not shape/size

what is the most common cataract

cortical followed by nuclear

cortical is 4x more prevalent in warm climates (closest to equator)

PSC is least common but presents the most debilitating sx in its early stages - relatively high share of surgical interventions

risk factors for all cataracts

• AGE - PRIMARY RF

• smoking - strongest with nuclear

• UV radiation - strongest with cortical

• Diabetes - develop cataract at a younger age

• Females - live longer

• +FH

• trauma - image

• medications - strongest with PSC - corticosteroids (end in -one/-sone) and chlorpromazine - anti-psychotic

characteristics of nuclear cataract

age related sclerosis of the nucleus - leads to myopic shift

hardening of the nucleus - can be more difficult to fragment during phacoemulsification

chromophores

symptoms of nuclear cataracts

• blurred vision

• glare

• altered colour vision

What are cortical fibres influenced by?

• Lifelong mechanical stress associated with accommodation - increases thickness within the lens nucleus

• Nucleus hardens = frictional stress between nuclear and cortical fibres causes damage to the cortical fibres which is associated with cortical opacity development

SX of cortical cataracts

only occur once there is pupillary involvement;

• blurred vision - astigmatic shift

• monocular dipl. - driven by uncorrected astigmatic blur

• glare due to light scatter

Where region of the cortex do cortical opacities begin?

• Equatorial region of the cortex

most common location of cortical opacities

infero-nasal as this quadrant is most exposed to UV exposure as reduced shading from the nose

• If the sun is above to the right it targets our left infero-nasal region

What countries are most affected by cortical cataracts?

• Those closest to the equator e.g Singapore

• Angle between Earth and Sun is 90 degrees, so sun is high and penetrates the lower lens more effectively (UV EXPOSURE)

why does PSC occur;

• Metabolic activity of epithelial cells disrupts the regularity of the underlying lens fibres

• result in scattered light thus increasing opacity

SX of PSC

• Blurred vision - due to aberrations

• glare - due to light scatter

• contrast sensitivity massively reduced relative to other opacities

PSC Sx are dependent on;

• PUPIL SIZE - bright = miosis = greater influence of PSC as less light bypasses the opacity

• Sx greater at near - due to miosis when converging

• Pupil size decreases with age therefore more SX when older

• SX minimized at night as pupil size is larger (opposite of cortical)

cause of Congenital cataracts

• metabolic disorders

• abnormalities with autosomal dominant inheritance

• Chromosomal abnormalities

• idiopathic (unknown cause) - most common

disorders of lens growth

• lens can be subluxated (anomaly of lens position) - where the lens is no longer centred on the pupil known as ectopia lentis - due to trauma/developmental anomaly. Leads to unusual Rx and potentially surgical removal

• Aphakic px usually born without a lens

Manage cataracts optically

• Optimally correct RX - will correct low order but not high order aberrations

• Dispense

  • UV absorption (UVA) - also helps reduce LS

  • absorptive tints (sunglasses) - not good for Cortical as causes dilation

  • anti-reflection coatings

Referral criteria

set by the ICB;

• How it affects vision and quality of life

• one eye or BE

• risks and benefits of surgery

• if px wants surgery

• factor in if px at risk of any other conditions and we can’t view fundus?? e.g px has WET AMD + Cataract

• increased lens thickness = changes iris position = compromises anterior chamber = raised IOP = GLAUCOMA - image

WHAT DOES THE DIRECT REFERRAL SCHEME INVOLVE?

• full eye exam - fundoscopy and lens assessment - may require dilation to view the fundus

• discussion of surgery, pros and cons

• where px wants the surgery - BRI or ISPs e.g SpaMedica

• Any GH issues

• Transport to/from hospital

NHS pay £30 per direct cataract referral to HES

4 copies of this form

• 1 to the provider e.g BRI

• 1 to the Px’s GP

• 1 to keep for the practice

• 1 to give to px

Rx goals with surgery

• myopia - benefits near as px will be able to see close up without specs e.g -2.50 can see up to 40cm clear. will have to purchase SVD specs.

• most common is usually plano/-0.50D as marginally helpful for near and distance isn’t very blurred

• Monovision IOL - e.g plano in RE, -2.50DS LE - trial c monovision CL first?

• hypermetropia - worst result

• Toric IOL considered for corneal astigmatism > 1.00DC

• Multifocal/Accommodating IOL available privately -img

  • Results show minimal difference compared to non-accommodating IOL

What happens at the Pre-Op assessment?

• Biometry

  • Keratometry

  • Axial length

  • Anterior chamber depth

Together allow the calculation of required IOL power

• Discuss Rx goals

surgical procedure to remove cataracts

phacoemulsification - carried out under local anaesthetic

3mm corneal incision

1) Removal of the central circular portion of the anterior capsule

2) Insert the phaco probe which breaks the hard nucleus into fragments. The same probe is used to vacuum lens fragments from the eye. The softer cortex is removed by suction alone

3) The probe is then removed and a foldable IOL is inserted via a needle and is held in place by ‘haptics’

The surgery is typically self healing hence doesn’t require sutures

What injection are px given at the end of their cataract surgery?

• Intracameral Antibiotics e.g Vancomycin - injected into AC

what drug will the px be given post surgery;

NSAIDs and steroid drops to be used 4x a day for around 4 weeks

Drugs act as prophylactics

What happens post-surgery?

• Px has a review appointment 4/52 after surgery

• Check for complications

• Specs can be prescribed - think about anisometropia/adaptation in new rx

Complications of cataract surgery (1 in every 1000 cases)

• Corneal Oedema - surgical disruption to AC - BV, halos

• Endophthalmitis - serious and sight threatening - infection of the anterior and posterior chambers

• Raised IOP - surgical disruption to AC/response to MEDS - slow development over weeks

• Anterior Uveitis - post op inflammation

• Retinal Detachment - ocular surgery risks RD

• Adverse drug reactions

• PCO

Posterior capsular opacification

Most common complication post surgery

Onset anywhere from 3/12 to 4 years post op - average = 2 years

10% of px have some degree of PCO within 3 years

routine referral

Cystoid Macular Oedema

Relatively Common post surgery - Needs an OCT to confirm.

Onset 3/52 - 6/52

75% of cases resolve spontaneously within 6/12 - TAs or NSAIDs can speed up resolution

Around 90% of cases are resolved within 2yrs

leads to gradual blurred vision

Suspect CMO if VA lower than expected - not always noticeable on OCT

same day phone call

Optometric management of inflammation/infection/ Raised IOP post surgery

Same day phone call

Require ophthalmological opinion to rule out Endophthalmitis + Anterior uveitis