Clear Lens Extraction

Key Points at a Glance

Key Points of This Disease

• Clear lens extraction (CLE) is a surgery in which the clear lens without cataract is removed and an intraocular lens (IOL) is inserted.
• The main indications are high refractive errors such as high myopia and high hyperopia that are difficult to correct with LASIK or PRK.
• It is also effective for angle-closure glaucoma, and there is evidence that it provides better intraocular pressure control than laser iridotomy ¹⁾.
• The surgical technique is essentially the same as standard cataract surgery (phacoemulsification + IOL implantation).
• Because the lens is clear and soft, there is an advantage of being able to minimize ultrasound emission.
• The type of IOL (monofocal, multifocal, toric) and target refractive value are selected according to the patient’s preference.
• As a complication, there is a risk of retinal detachment, especially in high myopia, and adequate retinal evaluation is necessary before surgery.

1. What is clear lens extraction?

Clear lens extraction (CLE) is a refractive surgery that removes the clear crystalline lens and inserts an intraocular lens (IOL), using the same technique as cataract surgery. The only difference from cataract surgery is that there is no lens opacity. It is also called refractive lens exchange (RLE).

Indications

The main indications for CLE are the following two.

• Correction of high refractive errors: Patients with high myopia or hyperopia that cannot be corrected by LASIK or PRK are candidates. It is also indicated for presbyopic patients who desire multifocal IOL implantation.
• Treatment of angle-closure glaucoma: Removing the lens deepens the anterior chamber and opens the angle. The EAGLE study showed that CLE is more effective and cost-effective than laser peripheral iridotomy (LPI) for primary angle-closure glaucoma (PACG) ¹⁾.

Patient Selection Considerations

Age is an important selection criterion. Younger individuals retain accommodative ability and are generally not candidates because CLE induces presbyopia. Evaluation of axial length and retinal detachment risk is essential, as high myopia increases the risk of postoperative retinal complications.

Contraindications

CLE is contraindicated or high-risk in the following conditions.

• Age-related macular degeneration
• Poorly controlled diabetes or diabetic retinopathy
• Poorly controlled glaucoma
• History of corneal refractive surgery
• Recurrent inflammatory eye disease
• Corneal disease

Q What is the difference between clear lens extraction and LASIK?

A

LASIK is a surgery that changes refraction by cutting the cornea with a laser, and is indicated for mild to moderate refractive errors. CLE is a surgery that removes the lens and inserts an IOL, and is mainly indicated for high refractive errors and presbyopia that cannot be treated with LASIK. CLE results in loss of accommodation, so it is not usually performed in young patients.

4. Preoperative evaluation and tests

Preoperative evaluation for CLE is the same as for cataract surgery. The following examinations are required.

• Refraction test and axial length measurement: Essential for IOL power calculation. The target refraction is selected based on the patient’s preference and the type of IOL ²⁾.
• Corneal topography: Used to evaluate astigmatism and select IOL. Determines the indication for toric IOL or LRI (limbal relaxing incisions).
• Gonioscopy: Important for evaluating the angle in cases of angle-closure glaucoma. Quantitative assessment using anterior segment OCT or ultrasound biomicroscopy is recommended.
• Fundus examination: Especially in high myopia, preoperatively examine for retinal tears or lattice degeneration. Identify risk factors for retinal detachment in advance.
• Corneal endothelial cell count: Measured to assess the risk of intraoperative endothelial damage.

In selecting the target refractive value of the IOL, it is recommended that the patient and surgeon engage in sufficient shared decision-making ²⁾.

5. Standard Treatment

Surgical Technique

The surgical technique for CLE is essentially the same as phacoemulsification and aspiration (PEA) with IOL insertion. The main steps are as follows:

• Anesthesia: Topical anesthesia is standard. In some cases, sub-Tenon’s anesthesia is used.
• Corneal incision: A small incision of 2–3 mm is made. A self-sealing wound usually eliminates the need for sutures. The incision may be placed on the steep meridian to reduce astigmatism.
• Anterior capsulotomy (CCC): A continuous curvilinear capsulorhexis is performed. This is important for IOL fixation and centering.
• Lens removal: Since the clear lens has a soft nucleus, a capsular technique with minimal ultrasound oscillation is possible. In some cases, the nucleus can be aspirated using only the I/A handpiece. The advantage is less invasion of the corneal endothelium.
• IOL insertion: A foldable IOL is inserted through a small incision and fixed within the lens capsule.
• Removal of viscoelastic material and wound closure: The viscoelastic material is thoroughly aspirated to prevent postoperative intraocular pressure elevation, and wound watertightness is confirmed.

IOL Selection

The type of IOL is selected according to the patient’s wishes and lifestyle ²⁾.

Monofocal IOL

Distance correction: The most basic IOL that focuses on distance.

Postoperative: Reading glasses are needed for near vision.

Advantages: High optical quality, less glare and halos.

Multifocal IOL

Distance and near: Focuses on both distance and near.

Spectacle independence: Suitable for patients who want to see both distance and near without glasses after surgery²⁾.

Cautions: Abnormal photopsias such as glare and halos may occur.

Monovision

Right-left difference correction: The dominant eye is set for distance, and the non-dominant eye for near.

Indications: Effective for patients who have adapted to monovision with contact lenses.

Advantages: Can reduce spectacle dependence with monofocal IOLs.

Multifocal IOLs can reduce dependence on glasses for distance, near, and intermediate vision, but may cause unpleasant optical phenomena such as glare and halos. Thorough explanation to the patient is essential ²⁾.

CLE for Angle-Closure Glaucoma

CLE for primary angle-closure disease (PACD) can show better results than standard treatment including LPI in terms of intraocular pressure control and health-related quality of life in selected cases ¹⁾. The EAGLE study included patients aged 50 years or older, without cataract, and newly diagnosed with PAC (IOP ≥30 mmHg) or PACG ¹⁾.

• Intraocular pressure control: In the EAGLE study, the early lens extraction group showed superior IOP reduction compared to the standard treatment group ¹⁾.
• Improvement in anterior chamber and angle: Lens extraction deepens the anterior chamber and widens the angle.
• Reduction in additional treatments: In the EAGLE study, the early lens extraction group tended to require fewer additional glaucoma treatments ¹⁾.

In cases where acute attack or the indication for lens extraction is not clear, it is also possible to prioritize conventional treatments such as LPI and then consider CLE afterward ¹⁾.

Precautions in Treatment

• Since CLE completely eliminates accommodative ability, thoroughly explain the onset of presbyopia in younger patients.
• In high myopia, the risk of postoperative retinal detachment increases. Perform a thorough fundus examination preoperatively and consider prophylactic laser photocoagulation if necessary.
• When selecting a multifocal IOL, explain in advance that abnormal photic phenomena such as glare and halos may occur.
• CLE is not recommended for patients with complications or ocular diseases (e.g., age-related macular degeneration, diabetic retinopathy).

Q What are the disadvantages of multifocal intraocular lenses?

A

Multifocal IOLs can cause nighttime glare (light halos) and halos (rings of light). Some patients report decreased contrast sensitivity and waxy vision. In cases of dissatisfaction, IOL exchange may be necessary, so thorough preoperative explanation is important.

Q Is CLE effective for angle-closure glaucoma?

A

For primary angle-closure glaucoma, CLE has shown better results in terms of intraocular pressure and quality of life compared to standard treatment in cases meeting the EAGLE study criteria ¹⁾. See the Standard Treatment section.

6. Complications

Complications of CLE are essentially the same as those of cataract surgery.

• Posterior capsule rupture/vitreous prolapse: This is a representative complication that can occur during surgery. If it occurs, anterior vitrectomy and extracapsular fixation of the IOL are performed.
• Retinal detachment: Especially in high myopia, posterior vitreous detachment tends to occur early after surgery, increasing the risk of retinal detachment. Long-term follow-up is important.
• Endophthalmitis: This is one of the most serious complications caused by postoperative bacterial infection.
• Toxic anterior segment syndrome (TASS): Presents with sterile anterior segment inflammation in the early postoperative period.
• Corneal endothelial damage: Ultrasound energy or instrument manipulation can cause endothelial cell loss. In CLE, the risk is lower than in standard cataract surgery because the nucleus is soft.
• Posterior capsule opacification: Proliferation of residual lens epithelial cells causes opacification of the lens capsule. It is treated with Nd:YAG laser posterior capsulotomy.

The EAGLE study reported that early lens extraction is also cost-effective compared to standard treatment ¹⁾. However, decisions must consider individual axial length, retinal risk, age, and the impact of loss of accommodation.

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7. Latest Research and Future Perspectives (Research-Stage Reports)

For Patients: Please Read Carefully

The following content is currently at the research stage or under clinical trial and is not standard treatment available at general hospitals. This is reference information for professionals regarding future medical developments.

Accommodating IOL

Development of IOLs aimed at reproducing the accommodative function of the crystalline lens is underway. These lenses are designed to change focal length in response to contraction of the ciliary muscle, and if commercialized, they could expand the indications for CLE in younger patients.

Extended Depth of Focus IOL (EDOF)

Unlike conventional multifocal IOLs, EDOF IOLs provide continuous vision by extending the depth of focus. They are reported to cause less glare and halos and are expected to be a promising IOL option for CLE.

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8. References

1. Azuara-Blanco A, Burr J, Ramsay C, et al. Effectiveness of early lens extraction for the treatment of primary angle-closure glaucoma (EAGLE): a randomised controlled trial. Lancet. 2016;388(10052):1389-1397. doi:10.1016/S0140-6736(16)30956-4.
2. American Academy of Ophthalmology Preferred Practice Pattern Cataract/Anterior Segment Panel. Cataract in the Adult Eye Preferred Practice Pattern. Ophthalmology. 2022;129(1):P1-P126. doi:10.1016/j.ophtha.2021.10.006.