Nd:YAG Laser Capsulotomy
The Nd:YAG laser is used to treat secondary opacification of the posterior capsule and/ or contraction of the anterior capsule. Alternatively, intraocular surgical cleaning of the capsule may be performed during concurrent anterior segment surgery to maintain an intact posterior capsule if desired. To reduce the possibility of vitreous prolapse around the IOL and into the anterior chamber, posterior capsulotomy would ideally be delayed if possible until there is adequate apposition and fusion of the anterior and posterior capsules peripheral to the lens optic. Otherwise, the ideal time to treat symptomatic posterior capsule opacity with posterior capsulotomy has not been established.
In addition to capsulotomy, the Nd:YAG laser can be used for vitreolysis, synechiolysis, iris cystotomy, iridotomy, anterior hyaloidotomy for malignant glaucoma, removal of precipitates and membranes from an IOL surface, and fragmentation of retained cortical material.
The success rate of Nd:YAG laser posterior capsulotomy exceeds 95%. Indications for Nd:YAG capsulotomy include the following:
visual acuity symptomatically decreased as a result of PCO
a hazy posterior capsule preventing a clear view of the ocular fundus required for diagnostic and therapeutic purposes
monocular diplopia, a Maddox rod–like effect, or glare caused by wrinkling of the posterior capsule or by encroachment of a partially opened posterior capsule into the visual axis
contraction of anterior capsulotomy (capsular phimosis) causing encroachment on the visual axis, excessive traction on the zonular fibers, or alteration of the lens optic position
capsular block syndrome
Contraindications for Nd:YAG laser capsulotomy include the following:
inadequate visualization of the posterior capsule
a patient who is unable to remain still or hold fixation during the procedure (use of a contact lens or retrobulbar anesthesia may enhance the feasibility of a capsulotomy in such patients)
active intraocular inflammation, uncontrolled glaucoma, high risk of retinal detachment, and suspected CME (all relative contraindications)
The center of the visual axis, usually 3–4 mm in diameter, is the desired site for posterior capsulotomy. Dilation is not always necessary for the procedure, but it may be helpful when a larger opening is desired.
A high plus-powered anterior segment laser lens may improve ocular stability and enlarge the cone angle of the beam, reducing the depth of focus. The smaller focus diameter facilitates the laser pulse puncture of the capsule, and structures in front of and behind the point of focus are less likely to be damaged.
Capsulotomy can be performed in a spiral (Fig 11-15A), cruciate (Fig 11-15B), or inverted D–shaped pattern, beginning in the periphery to reduce the likelihood of central optic pitting until ideal energy levels and focus have been established. Occasional IOL dislocation into the vitreous has been reported after capsulotomy, particularly with silicone plate–haptic lenses. Constructing the capsulotomy in a spiraling circular pattern, rather than in a cruciate pattern, creates an opening that is less likely to extend radially, reducing the risk of dislocation. Also, the diameter of the capsulotomy should not exceed that of the IOL optic.
When minimal laser energy is applied, the anterior vitreous face may remain intact. A ruptured anterior vitreous face will usually not result in anterior chamber prolapse by the barrier effect of a PCIOL, although in rare instances vitreous strands can migrate around the lens and through the pupil.
Any PCIOL can be damaged by laser energy, but the threshold for lens damage appears to be lower for silicone than for other materials. The surgeon focuses the laser just behind the posterior capsule; pulses too far behind the IOL will be ineffective. The safest approach is to focus the laser beam slightly behind the posterior surface of the capsule for the initial application and then move anteriorly for subsequent applications until the desired puncture is achieved.
Figure 11-15 Illustrations of Nd:YAG laser posterior capsulotomy. A, A spiral pattern (arrow) may reduce the risk of radial tears. B, A cruciate pattern (arrows) or inverted D–shaped pattern (not shown) with an inferior flap hinge allows for initial punctures in the periphery and may help reduce the risk of central IOL laser damage.
(Illustration by Christine Gralapp.)
In cases of anterior capsule contraction, multiple relaxing incisions of the fibrotic ring relieve the contracting force and create a larger optical opening (see Fig 11-14).
Occasionally, the Nd:YAG laser is insufficient to address exceptionally dense fibrosis, which may require surgical manipulation with a discission knife, vitrectomy handpiece, or scissors.
Complications of Nd:YAG laser capsulotomy include:
transient or long-term elevated IOP
damage to or dislocation of the IOL
corneal abrasions (from the focusing contact lens for the laser surgery)
Transient elevation of IOP occurs in a substantial number of patients, with pressure levels peaking 2–3 hours after surgery. This elevation is likely due to obstruction of the outflow pathways by debris scattered by the laser treatment. It is more common in eyes with vitreous prolapse, those without in-the-bag fixation of the IOL, or those with preexisting glaucoma. Such elevation responds quickly to topical glaucoma medications, which can be continued for 3–5 days after the procedure.
To reduce the risks of postprocedure IOP spikes, inflammation, and CME following any type of laser capsular surgery, many surgeons prescribe prophylactic preoperative and postoperative ocular hypotensive medications (α-adrenergic agonist or β-blocker drops), as well as either topical corticosteroids or NSAIDs, although there is insufficient evidence to uniformly recommend these prophylactically in patients without additional risk factors. In patients with a history of CME or in high-risk patients such as those with diabetic retinopathy, the prophylactic use of topical corticosteroids or NSAIDs may be beneficial.
Nd:YAG laser capsulotomy may increase the risk of retinal detachment; the reported incidence is 0%–3.6%. Approximately 50%–75% of retinal detachments after cataract extraction occur within 1 year of surgery or within 6 months of capsulotomy, often in association with posterior vitreous detachment (PVD). In many cases, it is difficult to ascertain whether the retinal detachment is related to the capsulotomy or to the cataract surgery itself or whether it is simply a consequence of a naturally occurring PVD. Factors that increase the risk of retinal detachment after Nd:YAG capsulotomy include axial myopia, male sex, young age, trauma, vitreous prolapse, a family history of retinal detachment, and preexisting vitreoretinal pathology. It is important to instruct all patients to promptly report any new symptoms suggesting a PVD or retinal tear.
Excerpted from BCSC 2020-2021 series: Section 11 - Lens and Cataract. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.