Peripheral Iridotomy and Iridoplasty

Peripheral Iridotomy and Iridoplasty

Jeff M. Miller

The concept of pupillary block is central to understanding the mechanism of a peripheral iridotomy (PI). As forward aqueous flow between the lens and posterior iris is impeded, pressure builds behind the iris. This distends the iris forward, narrows the anterior chamber angle, and reduces aqueous clearance through the trabecular meshwork.

An iridotomy is essentially a bypass mechanism allowing aqueous to escape to the anterior chamber from behind the iris. This equalizes the pressure between the anterior and posterior chambers and keeps the angle open. The first known attempt at this process was in the 19th century with a surgical iridectomy.1 Laser peripheral iridotomy (LPI or PI) was introduced in the 1970s using an Argon laser, and by the 1980s, laser iridotomy had displaced surgical iridectomy as the more common procedure.2,3

Today, both the photodisruptive Q-switched Nd:YAG laser 1064 nm (usually shortened to just “YAG”) and the photothermal Nd:YAG-KTP 532-nm laser (often referred to as a “Green laser” or, erroneously, an Argon laser) may be utilized with a PI. Typically, a PI is completed with a photodisruptive 1064-nm Nd:YAG while a green laser, if utilized, is used to pretreat the iris in order to thin the targeted tissue. Pretreating with a green laser is often beneficial for a thicker, brown iris as it reduces the amount of tissue to penetrate, reduces the amount of energy needed from the Nd:YAG, and often provides an easier PI procedure. However, the green laser’s limited applications in other primary eye care procedures may not justify the additional expense.


The stronger contraindications to a PI include corneal opacities (edema, scar) prohibiting a clear view; a very shallow anterior chamber in which the corneal endothelium would be at risk from laser energy; or a patient unable to fixate and/or maintain posture in the slit lamp. Significant intraocular inflammation would also preclude the use of an ophthalmic laser. PIs should be avoided in secondary angle closure that does not feature pupil block such as neovascular glaucoma, irido-corneal endothelial syndrome, and inflammatory glaucoma. A PI is generally avoided in medication-induced angle closure (e.g., topiramate) due to the lack of efficacy.9

Relative contraindications include chronic corneal conditions (e.g., Fuchs endothelial dystrophy) and chronic retinal conditions (cystoid macular edema, epiretinal membrane). The risk-benefit ratio should be assessed for these patients. For mild and stable conditions, a PI may still be indicated after informed consent. For more severe disease, the underlying condition may need to be addressed first and/or other narrow-angle treatment options, such as cataract surgery, should be explored.

The presence of peripheral anterior synechiae, while not a contraindication, is related to the effectiveness of a PI. The amount of synechiae is inversely correlated with the expected amount of angle-opening post PI, and angle quadrants with peripheral anterior synechiae may not show appreciable opening after the PI.10


Informed consent should include a description of the procedure in plain language. For example, “A laser will be used to create a small opening in the colored part of the eye (iris) to allow fluid to flow freely from behind the iris to the drainage system in the front of the eye. This will help reduce the risk of a certain type of glaucoma known as angle-closure glaucoma.”

Potential alternative treatments, such as eye drops, monitoring, or invasive surgery, should be listed. Risks and complications inherent to any laser procedure include but are not limited to increased eye pressure, floaters, eye inflammation, irritation, and temporary blurring of vision. Complications more specific to PI include hyphema or microhyphema; the need for a repeat PI procedure; visual disturbances such as glare, halos, or lines in vision; as well as retinal detachment and permanent vision loss. While the incidence of retinal detachment after PI is very low, perhaps due to most eyes being hyperopic with a short axial length, it should still be considered for an informed consent.11

A note from the counseling physician should be included and phrased similar to, “I have counseled this patient as to the nature of the proposed procedure, the attendant risks involved, and the expected results.” The patient’s and doctor’s names should be printed and signed with the date as well as a witness signature (typically a staff member).


If not already performed, angles should be viewed via gonioscopy to assess visible structures and any pathology such as peripheral anterior synechiae. Additionally, anterior segment OCT may be performed.

The iris should be examined for a suitable location for the PI. This should be near the limbus, at least two thirds (or more) the distance from the pupil to the limbus. Traditionally, the PI has been placed at the 11:00 or 1:00 position with the 12:00 position avoided in case air bubbles are encountered. Some studies indicated that PI placement near the temporal limbus actually resulted in less dysphotopsia; specifically, less complaints of line/streak images.12 Subsequent studies have not shown a clear difference between superior and temporal placement of the PI.13 Either approach—placing the PI superior or temporal—is appropriate and is a matter of doctor preference. If the PI is placed superiorly, a partially exposed PI, as opposed to a PI fully covered by the upper lid, has a higher chance of visual complaints by the patient.14

Once the general location for the PI has been determined, the doctor should attempt to identify a crypt or relatively thinner area of the iris for the exact placement of the PI. Of course, not all irides will have a thin crypt in an acceptable location. If not, then proceed with a suitable location based on the recommendations mentioned previously.

To increase iris tonicity and facilitate laser penetration of the iris, one drop of pilocarpine 1% or 2% is instilled into the selected eye approximately one-half hour before the procedure. Higher concentrations of pilocarpine have the potential to cause forward rotation of the lens and iris and should be avoided. In addition to pilocarpine, an alpha-agonist such as brimonidine (0.1%-0.2%) or apraclonidine 1% should be instilled into the selected eye to blunt any potential IOP spike. Immediately before the procedure, proparacaine should be instilled into both eyes; instillation in the fellow eye will help control blinking during the procedure.


A laser (Abraham) lens is recommended (see Figures 14.1, 14.2, 14.3). While the procedure can be performed without a laser lens, use of a lens has several advantages: (1) it provides a 1.5× magnified view of the targeted tissue for the doctor; (2) it helps to focus and concentrate the laser energy; and (3) it provides an easy and inconspicuous method of staunching an iris bleed and potential hyphema. The most effective way to
stop bleeding is to apply gentle pressure with the Abraham lens for 30 to 60 seconds. If a lens is not being utilized, digital pressure must be applied to the globe to stop the bleeding.

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Jun 23, 2022 | Posted by in OPHTHALMOLOGY | Comments Off on Peripheral Iridotomy and Iridoplasty

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