This is a condition where the lens nucleus falls into the vitreous cavity during cataract surgery. When the entire lens capsule detaches due to zonular rupture, it may be predictable preoperatively. If posterior capsule rupture occurs during surgery, if a continuous curvilinear capsulorhexis (CCC) tear extends to the posterior capsule, or if zonular rupture enlarges intraoperatively, only the lens nucleus may drop. If the lens capsule is damaged, lens proteins can cause an inflammatory reaction in the vitreous cavity, requiring prompt management.
Incidence of nucleus drop1)
| Study | Incidence (%) |
|---|---|
| Cataract PORT 1994 | 0.28 |
| Schein et al 1994 | <1 |
| NEON 2000 | 0.1 |
| Zaidi et al 2007 | 0.18 |
| Jaycock et al 2009 | 0.2 |
| Greenberg et al 2011 | 0.16 |
The incidence of posterior capsule rupture and zonular dehiscence is 1.5–3.5%, and some cases of capsular rupture lead to nucleus drop 1). Retained lens fragments requiring reoperation are reported at 0.18% 1). Overall severe complications (endophthalmitis, suprachoroidal hemorrhage, retinal detachment) are 0.5%, and have decreased over time with the adoption of small-incision surgery 1).
According to multiple large-scale studies, the incidence rate is reported to be 0.1–0.28%. This is lower than the incidence of posterior capsule rupture (1.5–3.5%), and only a portion of posterior capsule rupture cases lead to nucleus drop. With the widespread adoption of small-incision, sutureless surgery, intraoperative intraocular pressure management has improved, and the incidence has been decreasing over the years.
Typical intraoperative signs include disappearance of the nuclear fragment from the surgical field with sudden deepening of the anterior chamber, sudden tilting or sinking of the nucleus, and a sharp decrease in aspiration power. The appearance of a clear area in the pupillary zone also suggests posterior capsule rupture. If these signs are observed, the procedure should be promptly stopped and the status of the posterior capsule and the position of the nucleus should be confirmed under the microscope.
Nuclear drop is broadly classified into preoperatively predictable drop and intraoperatively occurring drop.
Preoperatively predictable drop: Drop of the entire lens capsule due to zonular rupture (lens subluxation). It is important to check for lens tremulousness on preoperative slit-lamp examination.
Intraoperatively occurring drop: Caused by posterior capsule rupture, extension of a CCC tear to the posterior capsule, or intraoperative enlargement of zonular rupture.
Patient-Related Risk Factors
Diseases causing zonular weakness: Aging, exfoliation syndrome, Marfan syndrome, Weill-Marchesani syndrome, homocystinuria
Cataract status: Mature (hypermature) cataract, traumatic cataract, atopic cataract
Ocular history: Retinitis pigmentosa, history of retinal detachment surgery, history of vitrectomy, uveitis, history of laser iridotomy
Anatomical factors: Small pupil, shallow anterior chamber, high myopia (axial length >26 mm), primary angle-closure glaucoma
Surgeon and Technique-Related Risk Factors
Surgeon experience: Surgeon experience is an important risk factor for posterior capsule rupture. Inexperienced surgeons should carefully select high-risk cases and seek support from senior surgeons 2)
Surgical maneuvers: Unsuccessful CCC (extension of tear to posterior capsule), excessive ultrasound energy or irrigation leading to posterior capsule rupture
Insufficient preoperative evaluation: Overlooking zonular weakness, underestimating nuclear sclerosis
Preoperatively, it is important to assess the zonular status by checking for phacodonesis, exfoliation material, and anterior chamber depth using slit-lamp examination. Cataract hardness grading (Emery-Little classification) under mydriasis should also be performed. If zonular weakness is suspected, prepare a capsular tension ring (CTR) or capsule expander, and ensure the facility and system are ready to handle vitrectomy if needed.
| Evaluation Item | Confirmation Content |
|---|---|
| Medical History | History of ocular trauma, surgery (post-vitrectomy, post-retinal detachment surgery), use of alpha-1 blockers |
| Slit-Lamp Examination | Corneal clarity, anterior chamber depth, presence of exfoliation material, phacodonesis |
| Zonular Assessment | Presence of phacodonesis in sitting and supine positions, asymmetry of anterior chamber depth |
| Examination Under Mydriasis | Cataract hardness grading (Emery-Little classification), differentiation of posterior polar cataract |
| Corneal endothelium | Check endothelial cell density with specular microscopy |
Direct observation under the microscope confirms that the nuclear fragment has passed through the posterior capsule and fallen. If signs such as the nuclear fragment disappearing from the field of view, sudden deepening of the anterior chamber, or a sharp drop in suction power are observed during surgery, suspect this condition.
During surgery, it is directly observed under the microscope. Postoperatively, the degree of inflammation is assessed with slit-lamp examination, and the location and size of the nucleus are confirmed with fundus examination or ocular B-mode ultrasound. The retinal status (presence of retinal tear or detachment) is also evaluated simultaneously. Since the hardness and location of the dropped nucleus directly influence the choice of vitrectomy technique, accurate preoperative evaluation is essential.
If nucleus drop is confirmed during surgery, first perform anterior vitrectomy, complete IOL fixation, and safely conclude the surgery. If vitrectomy is needed, prompt referral to a facility capable of vitrectomy is necessary. Do not attempt to aspirate the nucleus from the anterior chamber side with a vitreous cutter (risk of retinal traction).
As conservative treatment, observe with steroid eye drops and, if necessary, oral steroids. Small nuclear fragments may cause floaters but can be absorbed spontaneously. If intraocular pressure rises due to inflammation, removal of the nucleus is necessary.
A. Nucleus confined to the anterior vitreous cavity
A 27G needle is inserted through the sclera into the pars plana, the lens is lifted to the pupillary area, and then an incision is made for extraction. Creating a large incision from the start is dangerous because it can cause massive vitreous prolapse.
B-1. Vitreous cutter method (soft nucleus)
Three ports are created and three-port vitrectomy is performed. The cut rate of the vitreous cutter is reduced to 200–500 cpm, and the nucleus is aspirated while being sandwiched with a light guide to avoid damaging the retina. This is possible with 25G/27G vitrectomy, but for Emery-Little classification grade 4 or higher, removal and aspiration with a vitreous cutter become inefficient.
B-2. US Fragmatome method (moderately hard nucleus)
Phacoemulsification and aspiration are performed using a dedicated ultrasound tip (fragmatome) that can be used in the vitreous cavity. Conventional pars plana lensectomy-vitrectomy can be combined with ultrasonic fragmentation. The nucleus is drawn to the aspiration port of the US tip, lifted to a position not contacting the retinal surface, and fragmented and aspirated 7).
B-3. PFCL (liquid perfluorocarbon) floatation method (hard nucleus)
This is an effective technique for hard nuclei 3)4)5). PFCL is injected into the vitreous cavity to float the dislocated lens up to the posterior surface of the iris. After floatation, the corneal endothelium is protected with an ophthalmic viscosurgical device (OVD), and the nucleus is emulsified and aspirated by PEA (phacoemulsification and aspiration) or removed entirely with a lens loop through a corneoscleral incision. PFCL can also be applied in cases with preexisting retinal detachment.
B-4. Kebab method (cotton candy method) (also applicable to hard nuclei) 6)
This is a technique to remove the dislocated nucleus without using PFCL, using a pencil-type bipolar and a phaco handpiece. The procedure is: ① core vitrectomy (non-contact wide-angle viewing system recommended) → ② apply the bipolar tip to the dislocated lens and pass current to adhere (output about 50%, about 1 second × several times) → lift the lens to the iris plane → ③ perform PEA with the phaco handpiece (aspiration pressure 70 mmHg, aspiration flow rate 30 mL/min).
It can also handle hard nuclei (Emery-Little classification grade 4-5) and can be performed with small incision and no sutures. In a study of 6 cases (8 eyes) at Nihon University Itabashi Hospital, visual acuity improved from 1.67±0.09 logMAR to 1.14±0.40 logMAR at 1 month postoperatively, intraocular pressure from 24.5±16.8 mmHg to 11.0±2.8 mmHg, and corneal endothelial cell density from 2,600±323 to 2,387±431 cells/mm² (only mild decrease). No postoperative complications occurred in any case, and the dislocated lens was removed through a 2.4 mm incision wound6).
After removal of the dislocated lens, secondary fixation of the IOL is necessary. With the widespread use of intrascleral fixation (flange technique), IOL fixation can be performed in a short time even in cases without a capsular bag. By combining the kebab technique and intrascleral fixation surgery, all steps can be performed with small incisions and no sutures.
Extent of Zinn zonule rupture and surgical technique selection
| Extent of Zinn zonule rupture | Capsule preservation | Surgical technique |
|---|---|---|
| Up to 1/4 | Possible | Cataract surgery with CTR (in-the-bag fixation) |
| 1/4 to 1/2 | Case by case | Anterior vitreous cutter-assisted out-of-the-bag fixation or scleral suture or vitrectomy + intrascleral fixation |
| More than 1/2 | Difficult | Kebab technique (vitrectomy + intrascleral fixation) |
If nucleus drop is recognized during cataract surgery, first complete anterior vitrectomy and IOL fixation to safely finish the initial surgery. Then promptly refer the patient to a facility capable of vitrectomy. Vitrectomy may be performed on the same day or a few days later, but early surgery is desirable if inflammation and elevated intraocular pressure due to lens protein persist. Choose the surgical technique based on nuclear hardness, location of the dropped nucleus, and associated findings (e.g., retinal tear).
Risk of retinal detachment: There are multiple reports on the incidence of retinal detachment after PPV for dropped nucleus8)9). Moore et al. reported retinal detachment in eyes that underwent PPV for dropped nucleus8), and Merani et al. analyzed outcomes after pars plana vitrectomy for retained nuclear fragments9).
When small nuclear fragments are absorbed spontaneously, the visual prognosis is good. If a large nucleus drops, removal by vitrectomy is necessary, and if the procedure is appropriate and prompt, a certain degree of visual recovery can be expected. Delayed treatment or complications such as retinal damage or endophthalmitis lead to a poor prognosis. In reports of the kebab technique, visual acuity improved from 1.67 to 1.14 logMAR at 1 month postoperatively, with no severe impact on the corneal endothelium.
American Academy of Ophthalmology Preferred Practice Pattern Cataract and Anterior Segment Committee. Cataract in the Adult Eye Preferred Practice Pattern. Ophthalmology. 2022;129(1):P1-P126.
European Society of Cataract and Refractive Surgeons. ESCRS Recommendations for Cataract Surgery. 2023. https://www.escrs.org/escrs-guideline-for-cataract-surgery/
Chang S. Low viscosity liquid fluorochemicals in vitreous surgery. Am J Ophthalmol. 1987;103(1):38-43.
Shapiro MJ, Resnick KI, Kim SH, et al. Management of the dislocated crystalline lens with a perfluorocarbon liquid. Am J Ophthalmol. 1991;112(4):401-405.
Lewis H, Blumenkranz MS, Chang S. Treatment of dislocated crystalline lens and retinal detachment with perfluorocarbon liquids. Retina. 1992;12(4):299-304.
Aso H, Yokota H, Hanazaki H, et al. The kebab technique uses a bipolar pencil to retrieve a dropped nucleus of the lens via a small incision. Sci Rep. 2021;11(1):7897.
Girard LJ, Canizales R, Esnaola N. Subluxated (ectopic) lenses in adults. Long-term results of pars plana lensectomy-vitrectomy by ultrasonic fragmentation with and without a phacoprosthesis. Ophthalmology. 1990;97(4):462-465. PMID: 2326024. doi:10.1016/S0161-6420(90)32560-5.
Moore JK, Scott IU, Flynn HW Jr, Smiddy WE, Murray TG, Kim JE, et al. Retinal detachment in eyes undergoing pars plana vitrectomy for removal of retained lens fragments. Ophthalmology. 2003;110(4):709-713; discussion 713-714. PMID: 12689890. doi:10.1016/S0161-6420(03)00020-4.
Merani R, Hunyor AP, Playfair TJ, et al. Pars plana vitrectomy for the management of retained lens material after cataract surgery. Am J Ophthalmol. 2007;144(3):364-370.
