Which mechanism produces glistenings in a hydrophobic acrylic intraocular lens?

Absorbed water separating into microscopic pockets as lens temperature changes Hydrophobic acrylic absorbs a small amount of water from the aqueous; when lens temperature changes, that water separates into microscopic pockets which scatter light.

Enzymatic breakdown of the acrylic polymer by aqueous proteins

Ultraviolet photo-oxidation of the lens chromophore

Deposition of aqueous calcium phosphate inside the polymer

What is the typical diameter of the microvacuoles seen in IOL glistenings?

1 to 20 micrometers The vacuoles measure roughly 1 to 20 micrometers across and may occupy the central optic or be scattered throughout it.

How do IOL glistenings appear on slit-lamp retroillumination?

Dark points within the lens optic Under direct illumination the vacuoles look like small bright refractile points, whereas on retroillumination the same vacuoles appear dark.

Bright golden refractile flecks

A uniform milky haze across the optic

Brown granular clumps on the anterior surface

Which visual complaint is most typical of dense IOL glistenings?

Glare and haze at night with reduced contrast sensitivity Dense glistenings may cause a mild drop in contrast sensitivity with glare or haze, especially at night, while chart acuity is often normal.

Sudden painless loss of central vision

Progressive peripheral field constriction

Monocular vertical diplopia on downgaze

Which feature separates posterior capsule opacification from IOL glistenings?

It is haze behind the lens that clears with laser capsulotomy Posterior capsule opacification is haze behind the lens that responds to laser capsulotomy, whereas glistenings lie within the lens material and cannot be removed by capsulotomy.

It causes bright refractile points inside the lens optic

It is typically bilateral and symmetrical

It appears only months to years after implantation

What is the appropriate management for the great majority of eyes with IOL glistenings?

Observation with reassurance Observation is appropriate in nearly all eyes, with reassurance that the vacuoles sit within the lens material, are not infection or inflammation, and usually stay stable.

Prompt intraocular lens exchange

A course of topical corticosteroid

A pseudophakic patient has dense glistenings in one eye only. What does this asymmetry warrant?

A search for another cause of the change Dense glistenings are usually bilateral and symmetrical, so a unilateral dense change should prompt a search for a different explanation.

Immediate explantation of the affected lens

Reassurance that asymmetry is the expected pattern

Nd:YAG treatment of the denser eye

How does calcification of a hydrophilic intraocular lens appear at the slit lamp?

Granular white deposits on or within the lens Hydrophilic lens calcification produces granular white deposits on or within the lens, with a different lens material and time course from glistenings.

Fine brown dots that can be wiped off the optic

Bright refractile microvacuoles in the central optic

Cells and fibrin layered on the anterior surface

When do IOL glistenings typically become visible after cataract surgery?

Months to years after surgery Glistenings tend to appear months to years after implantation, and their density increases with time and with exposure to temperature changes.

During the first postoperative week

Only after a second intraocular procedure

IOL Glistenings: Slit-Lamp Signs and Management

IOL glistenings are tiny, fluid-filled microvacuoles that form inside the optic of some hydrophobic acrylic intraocular lenses, and they shine like glittering droplets under the slit lamp.

They are common in lenses of this material, they increase with time, and in most patients they have no effect on vision.

The clinical question is when they matter, and how to separate them from opacities that do.

What Are IOL Glistenings?

Hydrophobic acrylic lenses absorb a small amount of water when they sit in the aqueous humor.

When the temperature of the lens changes, water that has entered the polymer can separate into microscopic pockets, and these pockets scatter light.

The vacuoles are typically 1 to 20 micrometers in diameter, and they may be seen in the central optic or throughout it.

They tend to appear months to years after surgery, and their density increases with time and with exposure to temperature changes.

The material, the manufacturing process, and the packaging influence how many form, and newer lens materials have been designed to reduce them.

Clinical Features

Most patients are asymptomatic, and the finding is discovered at the slit lamp.

In direct illumination, the vacuoles appear as small, bright, refractile points in the lens optic, and with retroillumination they look dark.

Dense glistenings may be associated with a mild decrease in contrast sensitivity and a feeling of glare or haze, particularly at night.

The visual acuity measured on a chart is often normal, which is why the complaint may seem out of proportion to the examination.

The vacuoles are in the lens itself and do not move with the position of the eye, and they cannot be removed with laser capsulotomy.

Test your knowledge 10 questions from this article

Differential Diagnosis

Calcification of hydrophilic lenses: granular white deposits on or within the lens, with a different material and time course
Posterior capsule opacification: haze behind the lens that responds to laser capsulotomy (see YAG laser capsulotomy)
Pigment dispersion on the lens surface: fine brown dots on the anterior surface that can be wiped off
Inflammatory precipitates: cells and fibrin on the lens surface in uveitis
Surface light scattering: fine, whitish changes on the optic surface seen with certain lens materials

A careful slit-lamp examination that focuses first on the anterior surface, then the optic, and then the posterior capsule usually separates these.

Clinical eye photograph illustrating Iol Glistenings

Evaluation

Document the density with a grading scale and a photograph, and measure the best-corrected acuity and the contrast sensitivity.

Ask about glare, halos, and night vision, and try to relate the symptoms to the density of the vacuoles.

Look at the other eye, because the problem is often bilateral and similar.

Rule out other causes of reduced contrast, including macular disease, posterior capsule opacification, and dry eye, before attributing symptoms to glistenings.

Management

Observation is appropriate in the great majority of eyes.

Patients should be reassured that the vacuoles are within the lens material, that they are not a sign of infection or inflammation, and that they usually remain stable.

In the very small number of patients with symptoms that are clearly related to dense glistenings, a lens exchange can be discussed, but the risks of surgery must be weighed against the benefit.

Laser techniques to reduce the vacuoles have been described in laboratory and early clinical studies, but they are not standard care.

Any lens exchange should follow the usual principles for explantation, and the surgeon should consider the status of the capsule and the zonules (see capsular tension ring indications).

Record the lens model and the date of surgery in the chart, because this helps in later decisions.

Counselling and Documentation

Patients who read about glistenings on the internet may worry that the lens is failing.

A clear explanation that the vacuoles are tiny, that they sit within the optic material, and that the retina and optic nerve are unaffected reassures most patients.

Make a note of the lens model in the record, together with the grade of the glistenings and the date of the examination.

This note is valuable if the patient later develops decreased contrast or night vision problems, because it shows the finding was present and stable.

Dense glistenings tend to be bilateral and symmetrical, and a unilateral dense change should prompt a search for another cause.

Patients with persistent complaints and a normal examination can be tested for contrast sensitivity, which may confirm the deficit and help decide on management.

Newer hydrophobic acrylic materials have been engineered to produce fewer vacuoles, so the severity depends partly on the lens platform that was used.

When a patient is planning a second eye operation after developing symptoms in the first, discuss the lens choice with this history in mind.

References

Werner L. Glistenings and surface light scattering in intraocular lenses. J Cataract Refract Surg. 2010;36:1398-1420.
Miyata A, Yaguchi S. Equilibrium water content and glistenings in acrylic intraocular lenses. J Cataract Refract Surg. 2004;30:1768-1772.
Salmon JF. Kanski’s Clinical Ophthalmology: A Systematic Approach. 9th ed. Elsevier; 2020.
American Academy of Ophthalmology. Basic and Clinical Science Course, Section 11: Lens and Cataract. AAO; current edition.

Test yourself

A few questions straight from this article.

1 / 10 0 correct

What are IOL glistenings?
Glistenings are tiny fluid-filled microvacuoles that form inside the optic of certain hydrophobic acrylic intraocular lenses and scatter light under the slit lamp.
Which mechanism produces glistenings in a hydrophobic acrylic intraocular lens?
Hydrophobic acrylic absorbs a small amount of water from the aqueous; when lens temperature changes, that water separates into microscopic pockets which scatter light.
What is the typical diameter of the microvacuoles seen in IOL glistenings?
The vacuoles measure roughly 1 to 20 micrometers across and may occupy the central optic or be scattered throughout it.
How do IOL glistenings appear on slit-lamp retroillumination?
Under direct illumination the vacuoles look like small bright refractile points, whereas on retroillumination the same vacuoles appear dark.
Which visual complaint is most typical of dense IOL glistenings?
Dense glistenings may cause a mild drop in contrast sensitivity with glare or haze, especially at night, while chart acuity is often normal.
Which feature separates posterior capsule opacification from IOL glistenings?
Posterior capsule opacification is haze behind the lens that responds to laser capsulotomy, whereas glistenings lie within the lens material and cannot be removed by capsulotomy.
What is the appropriate management for the great majority of eyes with IOL glistenings?
Observation is appropriate in nearly all eyes, with reassurance that the vacuoles sit within the lens material, are not infection or inflammation, and usually stay stable.
A pseudophakic patient has dense glistenings in one eye only. What does this asymmetry warrant?
Dense glistenings are usually bilateral and symmetrical, so a unilateral dense change should prompt a search for a different explanation.
How does calcification of a hydrophilic intraocular lens appear at the slit lamp?
Hydrophilic lens calcification produces granular white deposits on or within the lens, with a different lens material and time course from glistenings.
When do IOL glistenings typically become visible after cataract surgery?
Glistenings tend to appear months to years after implantation, and their density increases with time and with exposure to temperature changes.