After-cataract is a condition in which lens epithelial cells (LECs) remaining in the capsular bag after cataract surgery proliferate and migrate, causing opacification of the posterior capsule. Clinically, when it involves the pupillary area, it is called posterior capsule opacification (PCO).
The most common complication after cataract surgery, with at least 1 in 4 patients developing some form of posterior capsule opacification (PCO) within 5 years postoperatively. According to international meta-analyses, the incidence of PCO is approximately 11.8% at 1 year, 20.7% at 3 years, and 28.4% at 5 years. The incidence varies depending on the material and design of the intraocular lens used, as well as patient background factors (e.g., diabetes, uveitis, atopic dermatitis, congenital cataract, high myopia).
Nd:YAG laser posterior capsulotomy is a standard outpatient treatment, with hundreds of thousands of procedures performed annually in the United States, posing a significant social and economic burden. In recent years, with the widespread use of single-piece hydrophobic acrylic intraocular lenses and changes in edge design, the rate of YAG laser capsulotomy has been increasing again.
Even after the lens is removed during cataract surgery, lens epithelial cells remain within the capsular bag. These cells proliferate on the posterior capsule postoperatively, causing opacification and decreased vision (posterior capsule opacification). Nd:YAG laser posterior capsulotomy usually restores vision quickly.
Symptoms of posterior capsule opacification vary depending on the type and degree of opacity.
Elschnig pearls
Appearance: Frog-egg or pearl-like cell proliferation on the posterior capsule. Observed as well-defined small granules under retroillumination.
Cause: Regenerated lens fibers that migrate from the equatorial Soemmering ring to the center of the posterior capsule.
Characteristics: Causes significant visual impairment due to forward scattering of incident light. Mainly forms when the intraocular lens is fixated within the capsule.
Fibrous opacification
Appearance: Fibrous opacity mainly composed of collagen. Appears poorly defined and wrinkled. Spreads from the area where the anterior and posterior capsules are in contact.
Characteristics: Mainly backward scattering with mild impairment. Common in cases of extra-capsular fixation or asymmetric fixation of the intraocular lens.
Liquid after-cataract: A type where milky white fluid accumulates between the intraocular lens and the posterior capsule. Often accompanied by Elschnig pearls.
Diagnosis of after-cataract is primarily based on retroillumination with a slit-lamp microscope. After dilation, the posterior capsule is examined by retroillumination to determine the type and severity. In addition to visual acuity, contrast sensitivity and glare testing are also used to assess visual function.
After cataract surgery, residual lens epithelial cells within the lens capsule proliferate and migrate, invading the posterior capsule. The “barrier effect” provided by the posterior edge of the intraocular lens optic is initially effective, but when a Soemmering ring forms 3 to 5 years postoperatively, the previously formed capsular bend disappears, and quiescent lens epithelial cells become reactivated, gaining access to the space behind the optic (delayed secondary barrier failure).
Nd:YAG laser posterior capsulotomy is indicated when visual dysfunction due to posterior capsule opacification reaches a level that does not meet the patient’s daily functional requirements, or when posterior capsule opacification interferes with fundus observation 6). Prophylactic laser irradiation to a clear posterior capsule is not performed 6). In eyes with multifocal intraocular lenses, early consideration of indication may be given because of the greater functional impact under low-contrast conditions 6).
Nd:YAG laser posterior capsulotomy is often performed on an outpatient basis, and medical accidents involving misirradiation of phakic eyes have been rarely reported. There have been multiple cases where posterior subcapsular cataract was mistaken for posterior capsule opacification 4,5).
Moshirfar et al. (2022) reported a case of YAG laser irradiation mistakenly applied to a phakic eye with posterior subcapsular cataract, which was misidentified as posterior capsule opacification 4). Subsequent cataract surgery required extraction under conditions of posterior capsule rupture, and the final best-corrected visual acuity reached 20/20.
Kodama et al. (2025) reported a similar case, in which surgical cataract extraction and vitrectomy were performed after erroneous irradiation of a phakic eye 5). They emphasized that thorough implementation of a preoperative timeout is essential to prevent such “never events.”
Although rare, such cases have been reported. Posterior subcapsular cataract resembles posterior capsule opacification in appearance, and misirradiation can occur due to incomplete pupil dilation, inadequate verification of the operative eye, or misreading of records. Thorough preoperative pupil dilation and patient verification are essential 4,5).
First-line treatment for posterior capsule opacification. Can be performed on an outpatient basis and has a high rate of visual function recovery.
Procedure selection:
Ohashi et al. (2021) reported a case of a 67-year-old woman who underwent simultaneous Nd:YAG laser posterior capsulotomy in both eyes, in which a full-thickness macular hole formed only in the left eye where vitreomacular adhesion remained 2). The irradiation energy was relatively low at 1.2 mJ/pulse (total 25.2 mJ), and it was considered that vitreous contraction and traction, rather than the laser pulse itself, were the main causes of macular hole formation.
“Optic Capture” broadly refers to a state in which the optic of an intraocular lens is captured and constrained away from its intended position (within the capsular bag or at the anterior capsulotomy edge), or a surgical technique that intentionally creates such a state.
Intraoperative intentional optic capture (posterior optic buttonholing): A technique in which the intraocular lens optic is inserted posterior to the posterior capsule through the opening of a continuous curvilinear capsulorhexis (posterior optic buttonholing). The haptics are placed in the capsular equator. This blocks the migration of lens epithelial cells behind the optic, virtually eliminating posterior capsule opacification.
Accidental or postoperative optic capture (pupillary capture): A condition in which the intraocular lens optic is displaced anteriorly in front of the iris due to scleral-fixated intraocular lenses or postoperative IOL decentration (pupillary capture). This can cause decreased vision, increased intraocular pressure, uveitis, pigmentary glaucoma, and cystoid macular edema 1).
Pupillary capture occurring with scleral-sutured intraocular lenses can cause decreased visual acuity, ocular discomfort, and pupil deviation. In many cases, repositioning of the IOL posteriorly in the operating room is required, but in some cases, it can be safely managed with a 30-gauge needle paracentesis technique in an outpatient setting 1).
After cataract surgery, residual lens epithelial cells at the equator form Soemmering’s ring. These cells migrate onto the posterior capsule and form Elschnig pearls. Meanwhile, lens epithelial cells that undergo epithelial-mesenchymal transition produce extracellular matrix containing collagen, leading to fibrosis.
The physical barrier created by the sharp edge of the intraocular lens and anterior capsule overlap effectively prevents early posterior capsule opacification by blocking lens epithelial cell migration. However, 3 to 5 years after surgery, as Soemmering’s ring at the equator expands, the traction on the posterior capsule changes, reducing the barrier effect. Long-term clinical studies have shown that even with sharp-edged hydrophobic acrylic IOLs, the YAG laser rate reaches 42% at 10 years.
The evidence demonstrated by research is summarized below6):
In posterior optic buttonhole fixation, the optic is embedded into the opening of the continuous curvilinear capsulorhexis of the posterior capsule, creating a state where the posterior capsule exists on both the anterior and posterior sides of the optic (capsule-intraocular lens barrier). This barrier:
When the vitreous is removed, the vitreous support for the intraocular lens is lost, making it unstable. Additionally, the absence of the lens capsule causes iris flaccidity (iridodonesis/flaccid iris), increasing anteroposterior movement of the iris, and during mydriasis the optic can easily prolapse anterior to the iris (optic capture)1).
In cases where the scleral suture was placed 2 mm posterior to the limbus, the recurrence rate of optic capture was statistically significantly lower compared to cases with less than 2 mm (p=0.025)1).
Posterior optic buttonholing is being researched and practiced as a surgical technique that can virtually eradicate posterior capsule opacification. A follow-up study of 1000 consecutive cases over 4-6 years reported a retinal detachment rate of 0.2%, indicating good safety, and it is expected to become a routine procedure replacing standard in-the-bag fixation. However, inadequate pupil dilation and zonular insufficiency are contraindications, and sufficient surgeon training is required.
For negative dysphotopsia, reverse capture, in which the intraocular lens optic is placed anterior to the anterior capsulotomy edge, has been reported to be effective in improving symptoms in some cases6). However, debate continues, and there is no standardized protocol.
Kokame et al. (2022) developed an outpatient paracentesis technique using a 30G needle for postoperative pupil capture of suture-fixated intraocular lenses1). Pupil capture occurred in 18 of 495 eyes (3.6%), and all 54 outpatient procedures were performed painlessly under topical anesthesia. The ability to manage without emergency transfer to the operating room has been evaluated as an effective alternative in situations with limited operating room access (e.g., COVID-19 pandemic).
