Photodisruption is a form of minimally invasive surgery. It uses rapid bursts of an intensely focused laser source directed to the area of the eye where plasma forms. The focal volume absorbs the laser light, which causes an increase in temperature. The temperature rise, as a result, leads to the expansion and formation of plasma.
Following the rapid rise in temperature, pressure in the focal region also increases. The heightened tension and plasma expansion generate a shock wave and a bubble that later collapses. Plasma formation is vital as it enables the cutting of tissue. It achieves this through evaporating materials from the focal volume of the laser light.
Photodisruption was first used clinically in 1972 to treat open-angle glaucoma but became truly clinically useful in the early 1800s after the development of Nd:YAG lasers that operate in the Q switch mode.
The technique has become well established for treatment in capsulotomy for secondary cataract and acute angle-closure glaucoma. Other procedures, such as pupillary membranectomy, vitreous membranes division, and synechiolysis, have also been successful.
Nd:YAG laser photodisruption uses two kinds of pulses depending on the treatment. These are;
- Picosecond or femtosecond laser pulses
- Nanosecond laser pulses.
Before the Procedure
Before the procedure, the doctor may conduct a comprehensive exam to check the state of the eye. Patients may need to provide information on their health history and other medical issues, including; allergies, current medication, respiration, and blood pressure.
Before consenting to the surgery, the ophthalmologist should clearly explain its risks, benefits, and alternatives.
Since it is a minimally invasive technique, it does not require special preparations such as fasting and changing into theater clothes. In most instances, patients return home on the same day. It is advisable to have someone drive one home after treatment since bright light can be a bother.
The doctor begins by instilling dilating drops to get maximum dilation. Aesthetics eye drops then follow to allow comfortable fitting of a unique contact lens on the front surface of the eye. The contact lens helps to focus the laser beam on the treatment area and keep the eyelids open.
Once the lens is in place, there will be a bright light that allows the doctor to see the eye's internal structure. Laser settings are adjusted, including adjusting power, spot size and duration, number of pulses per shot, and offset of the laser.
The patient will then place their chin on the laser machine's frame and hold on to the handles. The doctor should ensure proper positioning and fixation of the head. The ophthalmologist turns on the Nd:YAG laser and aims the beam to the treatment area. The laser uses photodisruption to apply a series of focal ablations to disintegrate the offending tissues.
In the case of capsulotomy for secondary cataracts, the laser beam's function is to open the posterior capsule. For the treatment of acute angle-closure glaucoma, the laser beam creates a hole in the iris to allow it to fall away from the drainage area inside the eye.
Documentation is essential in any medical procedure, and therefore the surgeon will carefully document all the laser settings.
Once the process is complete, the doctor removes the contact lens and then rinses the eye. S/he may administer eye drops to control pressure spikes. After 30-60 minutes, s/he will check for pressure to ensure that it is not rising.
Risk & Complications
Photodisruption procedures have minimal complications. However, due to increased temperature and pressure that causes a micro explosion, there is a possibility of damage to the surrounding tissues.
Other risks that may come about from using photodisruption include:
- Inflammation - It is not uncommon for eye procedures to cause inflammation. It is, however, quite mild.
- Eye pressure is also a common occurrence if a lot of power was necessary to perform the procedure.
- Lens pitting - The laser beam may cause scratches on the artificial lens implant (contact lens) and will only become a problem if the pitting occurs directly on the visual axis.
- There might be mild light sensitivity and a scratchy feeling on the surface of the eye 24-72 hours after the procedure.
- In the treatment of acute angle-closure glaucoma, there may be bleeding of the iris. Aftercare & recovery
Aftercare & Recovery
Aftercare routines may involve the following:
- Use of anti-inflammatory drops for a few days or at most a week.
- Wearing sunglasses while out in the sun.
- Taking prescribed drugs to prevent the risk of eye pressure.
- Application of contact lenses on the eye to apply pressure and stop bleeding
- Check up to monitor and evaluate progress. The doctor should inform the patient on the next visit.
The use of Photodisruption has been very successful over the years. Its use ensures minimal invasion of transparent or opaque tissues, especially with the use of low pulses.