Lecture 9: cataract Flashcards
What is the age-linked prevalence of cataract?
30% of UK population over 65 years of age
What is the aetiology of traumatic cataract?
Blunt trauma
Penetrating injuries
Concussion
Infrared radiation
Electric shock
Ionizing radiation
Post-surgery (e.g. post-vitrectomy)
What are the metabolic causes of cataract?
Diabetes
Hypoglycaemia
Galactosaemia
Galactokinase deficiency
Mannosidosis
Fabry’s, Lowe’s, Wilson’s disease
Hypocalcaemia
What are other causes of cataract?
Corticosteroids (systemic and topical)
Chlorpromazine
Secondary – e.g. anterior uveitis
High myopia
Rubella
Myotonic dystrophy
Atopic dermatitis
Down’s syndrome (trisomy 21)
What is LOCS III?
-Lens Opacities Classification System
-Uses standard photographs
-Grades PSC, nuclear and cortical opacities
What is the cortical grading like in LOCS grading system?
-2 retro (1 posterior capsule, 1 iris plane) + 1 slit-lamp
-Observer compresses 3-D info to compare with standards
-Subjective aggregation of opacity
-Scale 0.1 (clear) to 5.9
What is the nuclear grading scale like in LOCS grading system?
What is the PSC grading scale line in LOCS?
scale 0.1 to 6.9
scale 0.1 to 5.9
What grading system was developed from LOCS III?
What are its features?
WHO simplified 3 grading system
Field use
Slit-lamp based
Aimed at obtaining comparable data across countries
Minimal training
What is oculus pentacam?
Blue light enhances scatter
Densitometry trace
Objective quantification of opacification
What are the symptoms of cataract?
forward light scatter-reduces contrast
stray light-consequence of light scatter at the retina from 1-90 degrees. can be measured psychophysical
back scatter-seen on slit-lamp. net curtain effect.
What type of surgery is used for cataract extraction?
What are the advantages?
phacoemulsification
-the nucleus is emulsified into small fragments a small anterior chamber incision is possible.
-minimally invasive: a small incision means a minor trauma and makes possible rapid visual rehabilitation.
-The surgically induced astigmatism is also minimized.
- safe and more accurate result for the patient.
-no sutures
-single post-op outpatient visit
-prescribe reading glasses at 1 month
What is the process of phacoemulsification?
What are the strategies of nucleus removal?
capsulorhexis (tearing capsule)
hydro-dissection
sculpting
nucleus removal
Divide and conquer
-Central sculpting is performed in the middle of the lens in a cross pattern.
-The lens is cracked into four pieces and the quadrants are emulsified.
Phaco chop
- most favorable for hard nuclei.
-The phaco tip is embedded in the center of the nucleus and held still while a “chopper” is used to divide the nucleus into many pieces in a movement from the edge of the lens to the center.
What complications can you get of cataract surgery?
-posterior capsule thickening (treated with YAG laser posterior capsulotomy)
-cystoid macular oedema (irvine-gass syndrome, usually resolves spontaneously)
-endophthalmitis (infection)
-retinal detachment
What complex cases can you get after cataract surgery?
white cataract
phakodonesis (mobile lens)-need to reinforce the capsular bag
Aniridia-iris damage
astigmatism
high myopia
high hypermetropia
What are the solutions for astigmatism?
Limbal Relaxing incisions
AK (astigmatic keratotomy)
Toric IOLs
BIOPTICS! (2nd stage laser Rx)
LASEK
LASIK (90% of refractive procedures)
