What is the purpose of a Nd:YAG peripheral iridotomy?

A peripheral iridotomy (PI) uses the Nd:YAG laser to create a small hole in the peripheral iris. This allows aqueous humor to flow directly from the posterior chamber to the anterior chamber without passing through the pupil, relieving or preventing pupillary block -- a mechanism where the iris bows forward and occludes the trabecular meshwork (angle closure). PI is used prophylactically in narrow-angle eyes at risk of acute angle-closure and therapeutically in patients who have experienced an acute attack.

What is SLT and how does it differ from ALT (argon laser trabeculoplasty)?

Both SLT (selective laser trabeculoplasty) and ALT target the trabecular meshwork to improve aqueous outflow and lower IOP. SLT uses a nanosecond-pulsed laser that selectively targets melanin in trabecular meshwork cells without causing thermal damage to surrounding tissue -- it is 'selective.' ALT uses a continuous-wave argon laser that creates visible coagulation burns and scar tissue. Because SLT causes no structural damage, it can be safely repeated; ALT typically cannot be repeated more than twice. SLT has largely replaced ALT in most practices.

What are anti-VEGF injections used to treat?

Anti-VEGF (vascular endothelial growth factor) intravitreal injections treat conditions characterized by abnormal blood vessel growth (neovascularization) or fluid leakage from abnormal vessels: wet age-related macular degeneration (wet AMD), diabetic macular edema (DME), proliferative diabetic retinopathy (PDR), central and branch retinal vein occlusions (CRVO, BRVO), and less commonly other neovascular conditions. Common anti-VEGF agents include ranibizumab (Lucentis), bevacizumab (Avastin), aflibercept (Eylea), and faricimab (Vabysmo).

Why is povidone-iodine required before intravitreal injection?

Povidone-iodine (Betadine) applied to the conjunctival surface immediately before injection dramatically reduces the bacterial load on the ocular surface, the primary source of organisms that could be introduced into the vitreous during injection. Endophthalmitis is the most feared complication of intravitreal injection, with incidence of approximately 1 in 1,000 to 1 in 5,000 injections. Povidone-iodine antisepsis is the intervention with the strongest evidence for reducing this risk and must be performed for every injection.

What should a patient expect after an intravitreal injection?

Patients should be counseled to expect: mild pressure or discomfort at the injection site (usually brief), possible temporary floaters caused by the small air bubble in the medication, mild redness at the injection site, and occasional brief awareness of the fluid spreading inside the eye. These are all normal. They should return or contact the office immediately if they experience sudden severe pain, dramatic vision loss, increasing redness over 24-48 hours, or new onset of floaters or flashing lights -- these symptoms may indicate a complication requiring urgent evaluation.

Laser and Injection Procedures for the CPOA Exam

Overview of Laser Procedures in Eye Care

Several laser procedures are performed in outpatient eye care settings. The CPOA assists with patient preparation, documentation, and post-procedure care. Understanding the purpose and basics of each procedure allows the CPOA to prepare correctly and counsel patients effectively.

Nd:YAG Laser Capsulotomy

The Nd:YAG laser (neodymium-doped yttrium aluminum garnet) delivers pulses of infrared laser energy that create photodisruption -- tiny plasma explosions that cut tissue without coagulating it.

Posterior capsulotomy (PC-YAG): Creates a hole in the clouded posterior capsule in posterior capsule opacity (PCO) after cataract surgery. Performed at the slit lamp using a contact lens. Fast (minutes), performed under topical anesthesia.

Nd:YAG peripheral iridotomy (PI): Creates a small hole in the peripheral iris to relieve or prevent pupillary block in narrow-angle and angle-closure glaucoma. Allows aqueous to bypass the iris and drain to the trabecular meshwork.

CPOA Role for YAG Procedures

Instill dilating drops (for PC-YAG) or constricting drops/pilocarpine (for PI) as ordered.
Apply topical anesthetic before the contact lens is placed.
Assist with positioning the patient at the slit lamp.
After the procedure, instill anti-glaucoma drops (IOP often spikes after YAG) if ordered, and measure IOP at 30-60 minutes post-procedure.
Provide post-procedure instructions (possible flashing lights for days after PC-YAG are normal; floaters from debris).

Selective Laser Trabeculoplasty (SLT)

SLT uses a Q-switched, frequency-doubled Nd:YAG laser to target melanin in trabecular meshwork cells, improving aqueous outflow and lowering IOP in open-angle glaucoma. It is safe to repeat, does not cause visible structural damage to the trabecular meshwork (selective), and is an alternative or adjunct to glaucoma drops.

CPOA Role for SLT

Instill anti-inflammatory drops (NSAID or steroid) and topical anesthetic as ordered.
Seat the patient at the laser slit lamp. Apply the gonioscopy contact lens (coated with methylcellulose coupling solution).
Measure post-procedure IOP (30-60 minutes post-SLT) -- IOP can spike transiently.
Schedule follow-up IOP check at 4-6 weeks to assess treatment response.

Laser Photocoagulation

Retinal laser photocoagulation uses a thermal laser (argon green or diode) to create small burns on the retinal surface. Applications:

Panretinal photocoagulation (PRP): Treats proliferative diabetic retinopathy and neovascular glaucoma by destroying ischemic peripheral retina, reducing the stimulus for neovascularization.
Focal laser: Treats diabetic macular edema by sealing leaking microaneurysms.
Retinopexy: Creates a chorioretinal adhesion around a retinal tear or hole to prevent progression to detachment.

💡 Clinical Tip: Panretinal photocoagulation causes significant peripheral vision loss by design -- it destroys peripheral retina to save central vision from neovascular complications. Patients must be counseled before PRP that they may notice reduced night vision and peripheral vision after the treatment. This is expected and normal.

Intravitreal Injections (Anti-VEGF)

Intravitreal injections deliver medication directly into the vitreous cavity. Anti-VEGF agents (ranibizumab/Lucentis, bevacizumab/Avastin, aflibercept/Eylea, faricimab/Vabysmo) block vascular endothelial growth factor, reducing abnormal blood vessel growth and fluid leakage in wet AMD, diabetic macular edema, and retinal vein occlusions.

Injections are given monthly or bimonthly for sustained disease control. Patients may receive dozens of injections over years.

CPOA Role for Intravitreal Injections

Prepare the injection area: povidone-iodine (Betadine) drop to the conjunctival surface is required for antisepsis before injection.
Apply topical anesthetic drops.
Position the patient correctly.
Prepare the injection field (speculum placement in some practices).
Post-injection: apply tobramycin or equivalent antibiotic drop if ordered.
Counsel patients on normal post-injection expectations: mild pressure, possible floaters from air bubble in the injected medication, and reassurance that the pinch sensation is temporary.
Schedule the next injection appointment.

⚠️ Common Mistake: Skipping the povidone-iodine prep before intravitreal injection. Povidone-iodine antisepsis of the conjunctival surface immediately before injection is the most important step in preventing endophthalmitis after intravitreal injection. It must not be skipped, even in patients with iodine sensitivity -- the doctor should prescribe an alternative antiseptic in such cases.

Key Takeaways

YAG laser: capsulotomy (PCO) or peripheral iridotomy (narrow angle). CPOA prepares drops, positions patient, checks post-procedure IOP.
SLT: lowers IOP in open-angle glaucoma. CPOA applies anesthetic and coupling gel, checks post-procedure IOP, schedules 4-6 week follow-up.
Retinal photocoagulation: treats diabetic retinopathy (PRP), macular edema, and retinal tears. CPOA counsels on expected peripheral vision changes after PRP.
Intravitreal anti-VEGF injections: treat wet AMD, DME, RVO. CPOA prepares eye with povidone-iodine, applies topical anesthetic, schedules ongoing monthly/bimonthly injections.
Povidone-iodine antisepsis is essential before every intravitreal injection.