Can an implanted lens become cloudy years later? Capsule clouding, calcification and glistenings

"I had cataract surgery years ago and my vision was excellent, and now the blurring has come back. Has the cataract returned? Or has the lens itself gone bad?" This question worries many patients, and the answer starts with reassuring news: a cataract does not come back, because the cloudy natural lens was removed. The most common reason for blurring to return is not the artificial lens at all, but a thin layer behind it. Less often, changes happen inside the artificial lens itself, and most of them need no treatment. Each of these has a different meaning and a different treatment.

First: posterior capsule clouding, the most common

In cataract surgery the artificial lens sits inside the outer bag of the natural lens, called the capsule. Over time, cells may grow on the back of this bag and make it cloudy. This is posterior capsule opacification, the most common complication of modern cataract surgery. It causes gradual blurring and reduced contrast (Maedel et al., 2021).

A patient may notice glare from lights before noticing a drop in vision itself. In a study that measured the effect of this clouding, light scatter inside the eye was affected when the clouding covered less than 1% of the center of the capsule, while the reading on the letter chart did not fall until it covered 78% (Meacock et al., 2003).

The usual treatment is a short laser session, called YAG laser (Nd:YAG), that opens a small window in the capsule. It targets the capsule, not the artificial lens. It can have a few complications, such as raised eye pressure or swelling of the center of the retina (Maedel et al., 2021). This clouding is less likely with lenses that have a sharp edge and water-repellent material, as we explain in our article on hydrophobic or hydrophilic lenses.

Second: glistenings inside the lens

On examination, a doctor may see tiny shiny dots inside the artificial lens, called glistenings. They are extremely small fluid-filled bubbles that form inside the lens material because it sits in a watery environment. They can appear in all types of lenses, but they are mainly linked to lenses made of water-repellent acrylic. Lenses differ in how prone they are to them, depending on their material, how they are manufactured and how they are packaged (Werner, 2010).

The important question is whether they weaken vision. In a Swedish study that followed patients from 10 to 15 years after surgery, these dots increased over time, yet no important effect on everyday vision appeared (Mönestam and Behndig, 2016). In another study of 34 eyes, they were not linked to visual acuity, contrast or light scatter (Stanojcic et al., 2019). But a retrospective study of 140 eyes found lower contrast and more light scatter when they were present (Luo et al., 2018).

So the evidence is not entirely consistent. The conclusion the reviews agree on is that in most cases these dots do not reduce visual acuity and do not require the lens to be changed, although they may increase light scatter in some patients (Kanclerz et al., 2021). Removal of a lens because of them has rarely been described (Werner, 2010).

Third: calcification, less common but with a greater effect on vision

Calcification is calcium deposited on or just under the surface of the artificial lens, so that it loses its clarity. Most reports concern water-loving (hydrophilic) lenses, including water-loving lenses coated with a water-repellent surface (Darcy et al., 2019; Kanclerz et al., 2021). After examining more than 400 removed lenses, researchers divided it into two main types: primary, linked to the lens itself and how it was made or packaged, and secondary, caused by conditions inside the eye. They noted that no material is completely immune to secondary calcification (Neuhann et al., 2008).

The clearest trigger of secondary calcification is air or gas injected inside the eye during a later operation. These operations include corneal endothelial transplants and vitreous operations that use gas. It has also been described after some glaucoma operations (Darcy et al., 2019; Werner et al., 2015). In a series of 14 eyes that needed a lens exchange after vitreous surgery, the clouding appeared after 20.5 months on average (Bopp et al., 2023). We explain gas and its effects in our article on the gas bubble after retinal surgery.

Unlike glistenings, calcification usually reduces vision when it happens (Kanclerz et al., 2021). In a study of 372 eyes having a corneal endothelial transplant, 12.9% of the lenses became cloudy, and vision was clearly weaker in these eyes (Lorenzana-Blanco et al., 2023).

How does the doctor tell them apart?

With a slit-lamp examination after dilating the pupil, the doctor sees where the clouding is and what it looks like. Capsule clouding lies behind the lens, on the bag. Glistenings are fine scattered dots inside the lens itself. Calcification usually appears in the middle of the lens, in the pupil area, and mainly on its front surface (Darcy et al., 2019). The doctor may also need to examine the retina, because blurring after surgery can have a cause other than the lens.

Does every change in the lens mean it must be replaced?

No. Capsule clouding is treated with laser without touching the lens. Glistenings are monitored in most cases (Kanclerz et al., 2021). Calcification that clearly weakens vision is effectively treated by exchanging the lens, and vision improved after exchange in the studies (Lorenzana-Blanco et al., 2023; Bopp et al., 2023). But a lens exchange is a new operation with its own risks, so it is decided according to how much vision is affected and the condition of the eye (Lorenzana-Blanco et al., 2023). We explain what happens when a lens needs to be refixed or exchanged in our article on the dislocated intraocular lens.

Questions patients often ask

Can a cataract come back after surgery?

No, because the natural lens was removed. When blurring returns years later, the most common cause is posterior capsule clouding (Maedel et al., 2021).

Does the laser session treat lens calcification?

No. The laser opens the capsule behind the lens. Calcification is on the lens itself, and if it clearly affects vision, the treatment is a lens exchange (Lorenzana-Blanco et al., 2023).

The doctor said my lens has glistenings. Should I have it replaced?

In most cases no, because these dots do not usually reduce visual acuity (Kanclerz et al., 2021). This is decided by your symptoms and the examination, not by their presence alone.

My lens is water-loving and I need retina or cornea surgery. What should I do?

Tell the surgeon which lens you have before the operation, because air and gas inside the eye are linked to calcification of these lenses (Darcy et al., 2019). The surgeon weighs this possibility against the need for the operation itself. See also our article on cataract after vitrectomy.

Summary

Blurring that returns after cataract surgery does not mean the disease has returned. The most common cause is capsule clouding, which is treated with laser. Glistenings inside the lens are common in some materials and usually do not affect vision. Calcification is less common, is linked mainly to water-loving lenses and to air or gas injected in later operations, and may need a lens exchange if it weakens vision. The examination decides the cause, and it is wrong to assume that every blur means a damaged lens.

This information is for health education and does not replace a medical examination.