1. Cataracts 1 Flashcards
What is the definition of cataract?
Cataract is any opacity of the crystalline lens.
Describe len anatomy in terms of vascularity, nerve innervation, structures (3), and cell types (2) and connection to other structures.
- Avascular
- Non-innervated
- Components: capsule, cortex with endothelium, nucleus
- Cell types: Cuboidal & Bow cells
- Connnected by zonules to ciliary body
What are the 2 main functions of the ciliary body?
- Produce aqueous
- Acts as a muscle to focus the lens
What is it called when the lens turns yellow?
Nucleosclerosis
What proteins does a lens contain? What are their purposes?
30-70% protein.
* α, β = protective
* γ = clumping in nucleus hardening
Describe the metabolism process that takes place in a len.
Anaerobic glycolysis occurs in the lens epithelium. This prodces energy needed for ion pumps, protein synthesis and to provide antioxidants (glutathione)
How is fluid transported across the lens?
Water enters the lens via the thin posteiror capsule. Water is then pumped out of the anterior epithelium via Na+/K+-ATPase.
Lens growth process
1. ... cells elongate and lose ... to form fibres.
2. Lens fibres elongate and meet at ..., forming: anterior suture (...) and posterior suture (...)
3. Continuous addition of ... to outer coat with age leads to increased ... with age. This increases ... with age and ... promotes cataract formation.
4. ... accumulate, causing yellowing
5. Expansion and aging cause ... thinning, which also causes increase in ... and cataract formation.
Lens growth process
1. Bow cells elongate and lose nucleus to form fibres.
2. Lens fibres elongate and meet at suture line, forming: anterior suture (Y) and posterior suture (inverted Y)
3. Continuous addition of fibres to outer coat with age leads to increased protein density with age. This increases refractive index with age and compression promotes cataract formation.
4. Chromophores accumulate, causing yellowing
5. Expansion and aging cause posterior capsule thinning, which also causes increase in fluid uptake and cataract formation.
What is the commonest cause of blindness in non-western countries?
Cataract
How does the prevalence of age-related cataract differ between race?
Indians have higher prevalence compared to Caucasians with age.
What are the 4 types of cataracts? Which one is the most common?
- Artefacts
- Congenital - sight debilitating vs non-debilitating
- Acquired - induced/ toxic, secondary/ metabolic, trauma/ radiation
- Senile - PSC/ cortical/ nuclear [most common]
What are the 3 types of anterior cataractous artefacts?
- Epicapsular stars
- Persistent pupillary membrane
- Leticonus (cone bulging of lens cortex & thining of capsule - associated w high myopia & Alport’s syndrome)
What are the two types of posterior cataractous artefacts?
- Mittendorf dots (persistent hyaloid artery remnant)
- Nets or whorls (vitreous condensations)
What are the 3 types of congenital cataracts?
- Sight debilitating
- Non-sight debilitating
- Associated w systemic disorder e.g. Galactosemia/ Rubella
Which congenital cataract causes ‘oil droplet’ cataract? How is this confirmed?
Galactosemia.
Blood test for GL-1 kinase
What type of cataract does congenital rubella cause?
Dense nuclear opacity
How does a congenital axial or sutural cataract appear?
Chalky white clusters on or near suture line
May be polychromatic or sparkling with crystals
How does a Cerulean congential cataract appear?
White to blue dots or spots in deep cortex, near the nucleus
How do a pulverulent, zonular and coronary congenital cataract appear?
- Pulverulent - dense cataract located in embryonic nucleus
- Zonular is a ‘zone of cataract’ in outer nucleus
- Coronary is when zonular has riders = wedges/ lines into the cortex
What are the common causes of acquired cataracts? (5)
- Corticosteroids (PSC)
- Tranquillisers/ Antipsychotics (Phenothiazine)
- Cholesterol-reducing drugs (Tiparanol)
- Miotics (1-2% Pilocarpine)
- Pesticides (Diquat)
What are the 6 most important causes of secondary/ metabolic cataract?
- Diabetes (advanced senile changes; true diabetic cataract = snowflakes)
- Galactosemia
- Myotonic dystrophy
- Atopic dermatitis
- Various syndromes - Down’s, Marfan’s, Alport’s
- Associated with eye diseases - RP, uveitis, glaucoma
What are the 4 major causes of traumatic/ radiation cataracts?
- Blunt injury
- Explosive injury
- Penetrating injury
- Radiating heat/ electrical shock e.g. glass blower cataract (large water vacuoles)
How does trauma cause cataracts? Can these cataracts be reverse?
Trauma or FB triggers inflammation inside the eye and thus cause the formation of cataracts. Cataracts may have a variable time of onset after injury.
Early cataract changes may be reversed.
What does SOAP stand for?
Subjective
Objective
Assessment
Plan
What are the 3 subjective consequences of cataracts? Which type of cataract causes the most issues?
Cataract causes an altered refractive state in the lens, ∴
* Poor vision: VA, contrast, spatial frequency,
* Glare sensitivity
* Diplopia/ polyopia/ ghosting/ monocular diplopia
Worst in PSC as cataract is close to the nodal point
What are the 4 methods for cataract detection?
- Red-reflex
- Direct illumination
- Indirect illumination - ‘ripples on beach’
- Specular reflection
Red reflex is formed by light refected from RPE/choroid. Therefore any opacities anterior to that can block light and form shadows.
Red reflex can be assessed using the ophthalmoscope or retinoscope. When moving your body, the relative motion of the corneal reflex to the shadow informs where the opacity lies.
* if with = behind nodal point (in vitreous)
* if against = in front of nodal point (in lens or AC)
Which techniques allow you to cut through the lens like a knife? What are the other benefits of this technique?
Slit lamp
* Gives position and depth information - esp with narrow beam + large angles
* Can visualise the suture lines to define the nucleus
Normal age changes to the lens isn’t a cataract until what happens?
It becomes a cataract when the age-related colour changes enter the nucleus of the lens
Which 2 grading systems are commonly used to grade cataracts?
- LOCS-3 - uses comparative photos for grading
- Wisconsin - divide lens into 8 pie sectors: inner & outer zones. Record the number of segments with any cataract
How will normal px response differ with high contrast vs low contrast Snellen charts? What about px with cataracts?
Normal px will drop 2 lines with low contrast vs high contrast.
Px with cataract will drop more than 2 lines with low contrast. They will also complain more about nighttime driving. Important t assess whether they are still legal to drive.
