Intraocular Refractive Surgery

Question 1

Phakic Intraocular Lenses - Advantages

Answer 1

removable, reversible, preserving natural accommodation, lower risk of endophthalmitis and postoperative retinal detachment because the crystalline lens barrier is preserved

Question 2

Phakic Intraocular Lenses - Disadvantages

Answer 2

potential risks associated with intraocular surgery. optics are not foldable, so their insertion requires a relatively large wound, which may result in postoperative astigmatism. Posterior chamber PIOLs have a higher incidence of cataract formation. PIOL will have to be explanted at the time of cataract surgery

Question 3

Phakic Intraocular Lenses - Indications

Answer 3

near or beyond the FDA-approved limits for laser vision correction, or who are otherwise not good candidates for keratorefractive surgery. –3.00 D and –20.00 D. hyperopia up to +10.00 D. off label for irregular topographies from forme fruste or frank keratoconus

Question 4

Phakic Intraocular Lenses - Contraindications

Answer 4

compromised corneal endothelium, iritis, significant iris abnormality, rubeosis iridis, cataract, or glaucoma

Question 5

Risk - Anterior chamber depth

Answer 5

less than 3.2 mm

Question 6

recommended for all currently FDA-approved PIOLs

Answer 6

peripheral iridotomy is recommended for all PIOLs to reduce the risk of pupillary block and angle closure; is not required for angle-supported PIOLs

Question 7

Iris-fixated phakic intraocular lens - technique

Answer 7

induce pupillary miosis before. The “claw” haptics are fixated to the iris in a process called enclavation

Question 8

Advantage Iris-fixated phakic intraocular lens over PIOLs

Answer 8

PMMA PIOLs require a 6-mm wound. and thus generally require sutures for proper closure, whereas iris-fixated PIOLs made of flexible materials can be inserted through a small, self-sealing wound of approximately 3 mm.

Question 9

Angle-supported phakic intraocular lens - advantage

Answer 9

inserted through a small incision without the need for pupil dilation

Question 10

AC IOL - complications

Answer 10

include raised IOP, persistent anterior chamber inflammation, traumatic PIOL dislocation, cataract formation, and endothelial cell loss
Iris-fixated phakic intraocular lens - glare, starbursts, and halos

Question 11

Posterior chamber phakic intraocular lens - complications

Answer 11

PIOLs increases the risk of cataract formation and pigmentary dispersion. If the posterior chamber PIOL is too large, vaulting increases. too small, the vaulting is reduced, decreasing the chance of chafing but increasing the risk of cataract.

Question 12

Angle-supported phakic intraocular lens - complications

Answer 12

nighttime glare and halos 20.0%, pupil ovalization, and endothelial cell loss

Question 13

Pupil ovalization - when

Answer 13

can occur because of iris tuck during insertion, or it can occur over time as a result of chronic inflammation and fibrosis around the haptics within the anterior chamber angle. Ovalization is more likely when the implant is too large

Question 14

correct residual corneal astigmatism

Answer 14

relaxing incisions and arcuate keratotomies with either blade or femtosecond laser may be used to correct residual corneal astigmatism of less than 2.00 D. Supplemental surface ablation or LASIK could also be considered

Question 15

upper limit of commercially available IOL power

Answer 15

+40.00 D

Question 16

“piggyback” IOL system

Answer 16

2 posterior chamber IOLs are inserted. One IOL is placed in the capsular bag, and the other is placed in the ciliary sulcus

Question 17

“piggyback” IOL system - complications

Answer 17

interlenticular opaque membrane. These membranes cannot be mechanically removed or cleared with the Nd:YAG laser; the IOLs must be removed. Interlenticular membranes have occurred most commonly between 2 acrylic IOLs, especially when both IOLs are placed in the capsular bag. When piggyback lenses are used, they should be of different material. Piggyback IOLs may also shallow the anterior chamber and increase the risk of iris chafing, especially in smaller eyes

Question 18

Incidence of astigmatism

Answer 18

50% of patients have 0.75 D or more corneal astigmatism at presentation for cataract surgery, and 15%–29% have 1.50 D or more corneal astigmatism

Question 19

rotation of the lens - reduction of correction

Answer 19

every 10° off-axis rotation of the lens reduces the correction by approximately one-third. it should be repositioned before permanent fibrosis occurs within the capsular bag. However, waiting 1 week for some capsule contraction to occur may ultimately help stabilize this IOL

Question 20

Light-Adjustable Intraocular Lenses

Answer 20

The light-adjustable IOL is a 3-piece silicone-optic posterior chamber IOL that can be irradiated with ultraviolet light through a slit-lamp delivery system 1–2 weeks after implantation to induce a change in the shape, and thus the power, of the IOL. induce myopic, hyperopic, and astigmatic shifts. In initial work, results indicate that up to 5.00 D of spherical and up to 2.00 D of astigmatic change can be induced. after irradiation, the lens is functionally a monofocal

Question 21

Accommodating Intraocular Lenses - mechanism

Answer 21

movement of its hinged haptics during the accommodative process

Question 22

Multifocal Intraocular Lenses - mechanism

Answer 22

light rays to be split such that different focal points are created where objects will be clearest

Question 23

pupillary diameter when unaided reading ability may diminish

Answer 23

less than 2.0 mm

Question 24

Multifocal Intraocular Lenses - disadvantages

Answer 24

more sensitive to minor optic decentration, more likely to have significant glare, halos, and ghosting. reduction in contrast sensitivity, worse subjective quality of vision. intermediate vision may be less clear than distance or near acuity. more sensitive to posterior capsule opacification