Cataracts Flashcards
What are cataracts?
Vision-impairing disease characterised by gradual, progressive loss of transparency of the lens
It is one of the leading causes of visual morbidity and blindness worldwide
What are posterior subscapular cataracts?
lie in front of the posterior capsule
manifest as vacuolated or plaque- like appearance
they are associated with steroid use and DM
patients have particular trouble with bright sunlight/oncoming headlight
reading vision is affected more than distance vision
What are cortical cataracts?
Opacities which start as clefts and vacuoles on the cortex between lens fibres
subsequent opacification leads to radial spoke like opacities
They are closely related to environmental stresses
E.g UV exposure, diabetes and drug ingestion
What are nuclear cataracts?
Nuclear sclerosis characterised by a yellowish hue and in later stages a brownish discolouration
Have a correlation with smoking, with calcitonin and milk intake
What can age related cataracts be exacerbated by?
Allergy Hyper/hypotension Mental retardation UV light Infrared radiation Diabetes
What are congenital cataracts?
Detected at birth
Jevenile cataracts develop in first 12 years of life
1/3 are inherited
Can be total or partial:
Partial:
Polar- anterior or posterior
Zonular- lamella, stellate sutural or nuclear
What are traumatic cataracts?
Iris is torn away from its normal insertion causing shrinking and damage
needs to be sutured and allowed to repair before reconstruction occurs
Blunt- rosette-shape appearance or are of the PSC variety
Penetrating- whole lens can become cataract if large, or leave an opacity that is localised to site
How can cataracts be divided by their maturity ?
Immature
Mature- cortex completely opaque
Hyper-mature- small and wrinkled lens material due to leaking out of material
What are the clinical features of cataracts?
Decreased visual acuity: gradual progressive deterioration and disturbance in vision (PSC can result in reduction in near acuity more than distance vision. Nuclear sclerotic cataracts have decreased distance acuity and good near vision)
Glare- decrease in contrast sensitivity in brightly lit environments or disabling glare during the day to glare with oncoming headlights at night
Myopic shift- increase the diopteric power of the lens resulting in a mild-to-moderate degree of myopia- this so-called second sight in presbyopic patients is associated with nuclear sclerotic cataract
Monocular diplopia- when nuclear changes are concentrated in the inner refractile area in the centre of the lens
What are the investigations used for cataracts?
History and slit lamp examination
Lab tests to detect comorbidities
Occular B-scan US- a posterior pole pathology is suspected and an adequate view of the back of the eye is obscured by the dense cataract- this is helpful in palnning out the surgical management and providing a more guarded post-operative prognosis for the visual recovery of the patient
An accurate biometry (axial length and keratometry) should be performed to calculate for the IOL power to be used- the power of the IOL on the operated eye must be compatible with the refractive error of the fellow eye to avoid complications- eg. post-operative anisometropia
Corneal integrity, specifically the endothelial layer- slit lamp examination. pachymetry and specular microscopy to predict post-operative corneal morbidities to weigh the risks vs. benefits of performing cataract extraction- eg. corneal oedema or corneal decompensation
Which medical agents are being investigated for the treatment of cataracts?
aldose reductase inhibitors sorbitol-lowering agents aspirin glutathione-raising agents anti- oxidant vitamins C & E
What is intracapsular cataract extraction (ICCE) ?
ICCE is now reserved in cases where zonular integrity is impaired severely to allow successful lens removal and IOL implantation in ECCE
larger limbal incisions and subsequent risk of delay in healing, visual rehabilitation, significant astigmatism, post-operative would leaks, post-operative cystoid macular oedema (CME), retinal detachment and post-operative corneal oedema made it unpopular
What is extracapsular cataract extraction (ECCE)?
Involves the removal of the lens nucleus through an opening in the anterior capsule with retention of the integrity of the posterior capsule
a smaller incision leads to less trauma to the corneal endothelium, better anatomic placement of IOL (within an intact posterior capsule), reduces the incidence of CME, retinal detachment, endophthalmitis
What is phacoemulsification (PE)?
Both ECCE and PE are similar in that extraction of the lens nucleus is performed through an opening in the anterior capsule or by anterior capsulotomy followed by irrigation and aspiration of cortical material and placement of the IOL in the posterior capsular bag
PE uses smaller incisions, affording more rapid would healing and faster visual rehabilitation a relatively closed system allows a better control of IOP, safeguards against +ve vitreous pressure and choroidal haemorrhage
What isphacoemulsification (PE)?
Both ECCE and PE are similar in that extraction of the lens nucleus is performed through an opening in the anterior capsule or by anterior capsulotomy followed by irrigation and aspiration of cortical material and placement of the IOL in the posterior capsular bag
PE uses smaller incisions, affording more rapid would healing and faster visual rehabilitation- a relatively closed system allows a better control of IOP, safeguards against +ve vitreous pressure and choroidal haemorrhage
