What are the symptoms of Posterior Capsule Opacification?
The symptoms of PCO are very similar to the symptoms of cataract.
Blurred vision. This usually develops gradually, over months or years.
Seeing glare and streaks around lights at night.
Difficulty reading, including road signs when you’re driving.
Risk factors for developing Posterior Capsule Opacity
You may wonder why some patients develop PCO months after their cataract surgery, while other patients don’t develop it for many years. There are several reasons for this, including the intraocular lens material, surgical technique, and age of the patient. Below is a list of the key risk factors for developing PCO.
Risk factor 1: Intraocular lens material and design
The most important factor affecting your likelihood of developing PCO is the material that your artificial intraocular lens is made of. Although all modern intraocular lenses are made from acrylic plastic, this exists in two forms: acrylics that attract water (hydrophilic) and acrylic that repel water (hydrophobic).
Intraocular lenses made from hydrophilic acrylic are much more prone to attracting PCO than lenses made from hydrophobic acrylic. It has been calculated that hydrophilic lenses may be 30-70 times more likely to develop PCO than hydrophobic lenses. However, many surgeons will still choose to implant hydrophilic intraocular lenses due to their thinner size and favourable optical properties.
The edge profile of your intraocular lens also significantly influences your likelihood of developing PCO. Lenses that have square, sharp edges have a much lower risk of PCO than lenses with smooth round edges. Research indicates that the square edge acts as a physical barrier that impedes the migration of lens cells across the lens capsule. Intraocular lenses with square edges therefore help to prevent PCO from reaching the centre of the lens capsule, where it would cloud a patient’s vision.
Hydrophilic lenses inherently have less-square edges than hydrophobic lenses, as they are made from a dehydrated material that is cut and then rehydrated. As the lens re-hydrates it swells, causing the lens edge to becomes slightly rounded. In contrast, hydrophobic lenses are cut to shape and left permanently dehydrated. This leaves the edge profile square and sharp.
Risk factor 2: Your age
Younger patients develop posterior capsule opacity much faster than older patients. Young patients heal more vigorously following any surgical procedure – their lens capsule also tends to opacify much faster. Children undergoing cataract surgery will invariably develop posterior capsule opacity, usually within 12 months of the surgery (or less). In contrast, many 80 year old patients may not develop significant PCO within their lifetime. When performing cataract surgery for patients less than 55 years of age I tend to favour hydrophobic intraocular lenses, to help to delay their onset of PCO.
Risk factor 3: Meticulous Surgical Technique
Although PCO is not a serious problem, I always do everything I can to delay its onset for my patients. There are two main surgical strategies to reduce the likelihood of PCO when performing cataract surgery.
Firstly, I always pay meticulous attention to polishing the patient’s lens capsule to remove as many residual lens cells as possible. I use a soft silicone capsular polisher for this purpose, as the lens capsule is incredibly delicate (just 3 microns in thickness!). Removing all lens cells from the capsule is facilitated by performing exactly correctly a step of the operation called “hydrodissection”. During this step, I inject sterile water between the lens capsule and the cataract, to from a cleavage plane that precisely separates the cataract from the capsule. Attention to detail with this step is one of the most under-appreciated aspects of modern day cataract surgery (in my humble opinion!).
The other surgical step that slows the onset of PCO is the capsulorrhexis. This is the circular opening that is made at the front of the lens capsule in order to access the cataract. The perfect capsulorrhexis is a circle 5.5mm in diameter centred on the pupil. This perfectly-sized capsulorrhexis enables the capsule to tightly shrink-wrap around the intraocular lens in a manner that impedes the growth of residual lens cells
The Treatment of PCO: YAG laser capsulotomy
Similar to acataract, PCO causes gradual blurriness of vision.Fortunately, the treatment of PCO is easy, safe, and painless. Furthermore, the treatment lasts for life and therefore only needs to be performed once.
PCO is removed using a laser procedure performed in clinic. The procedure is called “YAG laser capsulotomy”. The ‘YAG’ refers to the type of laser used to generate the laser energy – a neodymium yttrium aluminium garnet (Nd:YAG) laser.
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