Cataract Surgery, Complications, and Special Situations

Question 1

compare/contrast cohesive and dispersive OVD

Answer 1

cohesive: high molecular weight, high surface tension, high pseudoplasticity, poor coating ability, easy to aspirate
dispersive: low molecular weight, low surface tension, good coating ability, difficult to aspirate, useful in plugging posterior capsule tear and in anteriorly displacing dropped lens material from the vitreous back towards the phaco tip

Question 2

cavitation v chatter

Answer 2

cavitation: bubble formation at phaco tip
chatter: repulsion of nuclear fragments when ultrasonic stroke overcomes the vacuum (can be reduced by reducing phaco power)

Question 3

duty cycle v power v energy v stroke

Answer 3

• duty cycle: percentage of time that phaco power is on
• power: percentage of maximal stroke length; correlates to ability of phaco needle to break down lens material
• energy: power x time
• stroke: linear distance that the phaco tip traverses

Question 4

aspiration flow rate v rise time v surge v vacuum

Answer 4

• aspiration flow rate: rate of fluid passage through the aspiration port
• rise time: time it takes the vacuum to build once the aspiration port had been occluded (directly proportional to the aspiration flow rate)
• surge: rapid flow of fluid into the phaco tip after vacuum overcomes occlusion; if exceeds the capability of the irrigation line, can cause anterior movement of capsule and other structures
• vacuum: magnitude of negative pressure created in the aspiration tube; directly proportional to aspiration rate

Question 5

ways to decrease surge

Answer 5

increase inflow rate, decrease vacuum, low compliance tubing of small diameter, smaller tip

Question 6

correlation between phaco tip bevel angle and force generated

Answer 6

steeper angle means larger surface area of port, which at a given pressure means higher force

Question 7

foot pedal positions

Answer 7

1: irrigation
2. irrigation + aspiration
3. irrigation + aspiratoin + phaco

Question 8

hydrodissection v hydrodelineation. when is the latter not useful?

Answer 8

hydrodissection: separation of cortex from capsule
hydrodelineation: separation of various layers of the nucleus with BSS. not useful in white or densely brunescent nuclei

Question 9

settings for dense nucleus removal

Answer 9

moderate-high power, moderate vacuum, low aspiration

Question 10

Young corneas are ____ shaped tend to have _____ astigmatism with steepening at ____ and positive cyl in the MRx with axis _____ and power ____.
Old corneas?

Answer 10

young: oblate, with the rule, 90, 90, 180
old: prolate, against the rule, 180, 180, 90

Question 11

what is coupling with regards to astigmatic correction

Answer 11

flattening at the area where a suture is cut or relaxing incision made, and steepening 90 degrees away

Question 12

astigmatic keratotomy v limbal relaxing incision

Answer 12

both involve relaxing incisions parallel to limbus, flattening the cornea in that meridian and steepening 90 degrees away. AK is done on the cornea and thus can lead to glare and discomfort. LRI is done at the limbus to ameliorate these complications. LRI can fix astigmatism from 0.5 to 3.0 diopters.

Question 13

most common complication of phacoemulsification

Answer 13

posterior capsule rupture

Question 14

POD#1 epithelial edema with clear and compact stroma?

Answer 14

likely due to high IOP with intact endothelium, could be caused by residual lens material

Question 15

peripheral corneal edema that spares the center after intracap CE

Answer 15

Brown-McLean syndrome

Question 16

risk factors for corneal melt (keratolysis)

Answer 16

tear film abnormalities from KCS or Sjogren’s; RA; topical NSAIDs

Question 17

high IOP, persistent AC cell, and faint retrocorneal membrane with overlying edema following cataract surgery

Answer 17

epithelial downgrowth

Question 18

mild pain, limbus-to-limbus corneal edema, hypopion, dilated and irregular pupil, and elevated IOP a few hours after cataract surgery? most common causes? treatment?

Answer 18

TASS (toxic anterior segment syndrome). toxic material in AC, most commonly from inadvertent introduction of toxic substances into AC from improperly cleaned equipment, especially IA handpiece, cannulas, or tubing. treat with agressive topical steroids +/- systemic steroids

Question 19

management of post-op wound leak

Answer 19

• cycloplegics
• aqueous suppressants
• DECREASE topical steroids (to induce inflammatory wound healing)
• pressure patch or BCL
• preventive topical antibiotics