All of us, if we live long enough, will eventually develop cataracts. This includes glaucoma patients. Cataract in glaucoma patients requires special attention. This is because, one, the disease complicates the decision making; and two, these patients require extra attention during, and after surgery.
Cataract in Glaucoma Patients: Confounding factors
Before cataract surgery
- Vision loss due to cataract may be wrongly attributed to glaucoma.
- You expect your vision to become a hundred per cent after cataract surgery. However, in case the vision loss is due to glaucoma, the same may not happen. In case your doctor thinks that is the case, he will explain the outcomes to you beforehand.
- Advanced glaucomas may have a guarded visual prognosis. Usually, the vision recovery is good after cataract surgery, even in patients of glaucoma.
- Your doctor may not be able to judge the severity of glaucoma because of cataract.
- You will be asked to go for cataract surgery only if the cataract is impairing your vision.
- Your visual fields may not be accurate, or even not possible, in case of advanced cataract. This is because cataract in glaucoma patients leads to a generalized decrease in vision.
- Your doctor may not be able to evaluate your optic nerve, or perform imaging studies accurately. This is because cataract in glaucoma patients makes the optic nerve visualization difficult.
- The cataract may be increasing the degree of angle closure in your eyes.
- Your doctor may need to stop anti-glaucoma medications like pilocarpine and prostaglandin analogs (travoprost, bimatoprost, tafluprost and latanoprost) before cataract surgery.
- In fact, the doctor may discuss the need for glaucoma surgery along with cataract surgery. Your doctor may decide to perform either glaucoma surgery or cataract surgery first, and schedule the other for later. On the other hand, both surgeries may also be done in the same sitting. Your doctor will discuss the risks and benefits of the eventual course of action with you.
- In case of advanced glaucoma, the doctor may counsel you against multifocal lens implantation. Similarly, the femtosecond laser cataract surgery is also not preferred in advanced glaucoma.
After cataract surgery
- You may experience a sudden increase in eye pressure (also called intraocular pressure or IOP)after surgery. This can be due to the surgery itself, or because you will be using steroid drops in the post-operative period.
- Usually, patients experience a drop in eye pressure of about 2-4 mm of Hg in the late post-operative period. This decrease in eye pressure persists over time.
- Your doctor may titrate your eye drops for glaucoma after four to six weeks of surgery, to achieve the target IOP.
- Your doctor may order fresh tests for glaucoma after four to six weeks of surgery to set a new baseline.
Cataract in Glaucoma Patients: Benefits of Cataract Surgery
- You will definitely experience an improvement in your vision related quality of life. Your vision will become clear and sharp, and you will read better.
- The doctor will be able to assess your glaucoma better.
- Usually, your eye pressure will decrease after the surgery. This might mean lesser number of anti-glaucoma eye drops for you.
What Happens to Eye Pressure after Surgery for Cataract in Glaucoma Patients
Experts believe that cataract surgery is likely to reduce IOP in healthy eyes. Evidence in glaucoma patients also points to a drop in eye pressure. Let’s see what happens to the eye pressure in various subgroups after surgery for cataract in glaucoma patients.
In Ocular Hypertention
The Ocular Hypertension Treatment Study evaluated the effect of phacoemulsification (modern cataract surgery) on lowering IOP in patients with higher-than-normal IOPs. The patients who were not on medications were those with no evidence of visual field or optic nerve damage at the time, despite their elevated pressures.
The group of patients that underwent phaco had a pressure drop of about 4 mmHg, which persisted for several years. In fact, OHTS and other studies have found that higher the eye pressure before surgery for cataract in glaucoma patients, higher is the drop in IOP.
We need to remember, however, that this is true only in patients not on treatment for glaucoma.
In Glaucoma
There is no robust data to prove that glaucoma patients already on treatment, experience a similar drop in eye pressure. However, most doctors believe that pressures do decrease after surgery for cataract in glaucoma patients as well. In fact, most doctors have also reported that a higher pre-operative eye pressure means a higher drop in eye pressure following surgery. Also, the pressure drop is also more in patients with fewer eye drops.
Additionally, in case the pressure drop is significant, your doctor can even consider decreasing your glaucoma medication.
Post-operative increase in eye pressure
Post-operative spikes in eye pressure can be due to the following reasons, and your eye doctor will monitor you closely for this.
• The trauma and inflammation because of the surgery can cause IOP increase.
• Use of steroid drops can also cause an increase in eye pressures
• Sometimes, the previous glaucoma surgery can fail due to inflammation or scarring. Consequently, the eye pressures can increase.
These spikes are easily managed, your doctor may decrease steroids and prescribe non steroidal anti inflammatory drops instead. She may or may not increase your glaucoma periods to tide over the brief increase in IOP.
What are the treatment options after surgery for cataract in glaucoma patients
• You can be asked to continue your regular glaucoma drops as before.
• Your doctor may decide to decrease one eye drop and call you back for repeat eye pressure measurements. She can then reintroduce the glaucoma eyed drops as and when needed. This, however, will depend on the severity of your glaucoma.
• In case your eye pressures are higher than expected immediately after surgery, your doctor may increase your glaucoma eye drops.
• If you’ve had a previous glaucoma surgery, your doctor will monitor you very closely. Sometimes, cataract surgery can cause failure of a previously functional glaucoma surgery. This may be due to inflammation or scarring.
What you must discuss with your doctor before cataract surgery if you have glaucoma
• Is my visual prognosis guarded or poor due to glaucoma?
• What are my chances of vision recovery?
• Will you consider changing my eye drops before surgery?
• Will you consider giving me a drug holiday from glaucoma medications after surgery?
• Do you think I am a steroid responder?
• What kind of eye pressure drop can I expect after surgery?
• What are the chances of failure of my previous glaucoma surgery?
• Do I need cataract surgery right now, or can we wait for some time?
• Do you think I am a suitable candidate for mutifocal IOL?
• What will my follow up schedule be like?
• When will I need my fresh set of glaucoma investigations?
