What to know when doing a PI?

Procedure:
•Before LPI: Instill 1% pilocarpine then anesthetize eye with 0.5% proparacaine
• Abraham’s type of contact lens is applied. This lens has a +55 D, peripheral
button over a routine contact lens.

How does the lens help?
– Stabilizes the eye
– Helps to open the eye and keep the lids retracted
– Smoothens out the corneal surface
– Provides highly magnified peripheral view
– Reduces axial expansion of plasma, which reduces the spread of the damage
– Increases the power density of the spot.
– Gives pressure to prevent the bleed from increasing

•Site: In the peripheral third of the iris, just
anterior to the arcus.
-A crypt or a thinned area of the iris usually between 11 o’clock and 1 o’clock, where the lids superiorly cover it.

•Size : At least 200 μm but preferable size is 500 μm in diameter.
•End point: Sudden gush of aqueous or outflowing of the pigment from the posterior to the anterior chamber along with sudden deepening of the anterior chamber. -The presence of retro-illumination may be looked for after a few weeks of laser iridotomy, however it is not a sure sign of total penetration.
-Visualization of the anterior lens capsule confirms LPI.

•PARAMETERS: In Indian patients brown irides, LPI can be performed with a Nd:YAG laser, with the following
settings:
– Power—4–8 mJ
– Pulses/burst—1–3
– Spot size—fixed

• Monitoring and follow-up post LPI:
-At 1 hour after completion of LPI, check IOP
-Topical steroid & AGM post-op for 5-7 days
-At 1 week - Check IOP & confirm patency of the iridotomy site, and to check for any significant intraocular inflammation

COMPLICATIONS:
• Postoperative IOP spike
• Anterior uveitis
• Iris bleed & hyphema
• Focal cataract
• Posterior synechiae
• Visual symptoms
• Corneal decompensation.
Rare:
• Aqueous misdirection
• Recurrent herpetic keratouveitis
• Retinal and subhyaloid hemorrhage
• CD/RD
• Macular hole

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Image from Rajan Eye Care Hospital

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