Laser Cataract Surgery Specific Circumstances

It is important to note that the issues discussed in this section do not relate to the vast majority of patients. They are specific to certain individuals. We will always make clear whether any of these issues are relevant to the patient’s own circumstances.

Extreme anxiety

Typically patients having cataract surgery under local anaesthetic progress through the procedure without any pain or discomfort post-operatively. In circumstances where there is discomfort it is almost always controlled with simple measures such as paracetamol. Most patients have an uneventful course.

It is normal to be anxious about upcoming surgery and some patients will be concerned by the fact they are particularly anxious. They may even believe that a general anaesthetic will be required.

Generally, though, these patients choose to proceed with local anaesthetic once they understand its relative benefits and have had their specific concerns addressed. 

Clearly it is the patient’s ultimate decision regarding their choice of anaesthetic. We will always respect and ultimately proceed with their request.

Some patients are concerned with the sensation they will experience during the procedure. They can expect to feel Dr Connell’s hand resting on their forehead. Most describe a feeling of movement, not pain. They will see coloured lights, shapes and movements but they won’t have a clear view or awareness of the actual procedure.  In the unlikely even they experience significant discomfort, further anaesthetic can be administered. 

Other patients are concerned that they won’t be able to lie still. We pay particular attention to ensuring the patient is comfortably positioned prior to commencing the procedure. This, combined with medication to help relaxation, ensures that they are able to lie still. A small clip is placed under the eyelids to ensure they remain open. Although this is an unusual sensation, it is not painful. Occasionally, we will insert this small clip in our clinic during the pre-operative assessment to provide the patient with the feeling they can anticipate. In this way, the patient is typically reassured.

Patients are given medications by an anaesthetist via an intravenous drip to help them relax. Although this makes them slightly drowsy, they remain able to communicate. If they are experiencing discomfort, further anaesthetic can be administered. The need for further anaesthetic, however, is uncommon.

Most patients undergo the procedure without significant discomfort and often those who are particularly apprehensive are pleasantly surprised.

Refractive lens exchange

Some patients who are particularly short-sighted, long-sighted or who have significant astigmatism may elect to have the cataract surgical procedure despite their lens being clear and without opacity, with the aim of reducing their dependence on glasses. As a consequence glasses prescribed for them are necessarily less powerful and the requirement to wear them for day-to-day activities is diminished.

Blood thinners

Cataract surgery is performed on a part of the eye that is relatively free of blood vessels. Therefore the need for any blood-thinning medications to be temporarily discontinued is diminished.

In fact, in almost all cases, blood-thinning medication can continue, even on the day of surgery. 

Patients taking warfarin are advised to have their INR level taken in the week leading up to surgery.

Fuchs endothelial dystrophy

Fuchs dystrophy is a condition of the endothelium. 

All cataract surgeries result in the loss of some endothelial cells. The phacoemulsification stage of the surgery has the biggest impact on cell loss. The phacoemulsification instrument makes very fine vibrations (35 000 to 45 000 cycles per second), and it is these vibrations that allow the nucleus, the central part of the cataract, to be divided into segments and then removed. Approximately 10 to 15 percent of cells are lost, this number greater for larger, denser or more advanced cataracts. There have been significant developments in surgical technique that minimise endothelial cell loss. Most patients having cataract surgery have high endothelial cell counts. A small loss in these cases from cataract surgery is therefore of no clinical significance.

Patients with Fuchs endothelial dystrophy have a reduced endothelial cell number as a result of their dystrophy. With cataract surgery this endothelial cell loss has greater significance since the pre-surgery endothelial cell count is already low. 

The cornea may become swollen after cataract surgery. It may take several months for the cells to return to normal function and for corneal clarity to be returned. In mild forms it may result in blurred vision for a few hours on waking. On rare occasions the cornea does not return to its clear transparent state, and a corneal transplant is required.

Developments in cataract surgery techniques have resulted in better protection for the endothelial cell layer. These developments have been incorporated into current cataract surgical practice.

LACS has theoretical benefits for endothelial cell protection. Because the laser divides the cataract into pieces, a task that until now has been performed by phacoemulsification, the phacoemulsification is only required to remove the segments. As a consequence, less phacoemulsification is required during the operation. Accordingly there is likely to be less endothelial cell loss, an associated lower rate of corneal deterioration and the need for a corneal transplant is reduced.

Prior corneal transplantation

In patients presenting for cataract surgery who have previously had a corneal transplant, some of the same issues pertinent to Fuchs endothelial dystrophy apply. In such cases particular care and attention is made to minimise endothelial cell loss.

To that end, strong consideration should be given to the performing the procedure using LACS.

Ultimately there is a risk in the cornea transplant failing following cataract surgery. This may require the corneal transplant to be repeated. 

Pseudoexfoliation syndrome (PXF)

Patients with this condition can develop elevated eye pressure, or glaucoma, which damages the optic nerve. Unfortunately in some patients with PXF, the pressure can become dramatically high and cause a particularly aggressive form of glaucoma.

This condition is typically but not exclusively associated with people of Northern European background. It is most common in people from Scandinavian countries.

Most patients with PXF proceed through cataract surgery with an uneventful course. The zonules, which suspend the lens capsule in the eye, have an inherent weakness in PXF. In those uncommon circumstances where the capsular bag is excessively unstable, the intraocular lens (IOL) may need to be positioned in an alternative position, either in the sulcus or anterior chamber. Even more rarely, where the zonules are particularly weak and the cataract falls to the back of the eye, a second operation is required.

There are advantages in patients with PXF having surgery earlier. When there is a cataract that is allowed to mature and become larger, the potential for trauma to the zonules is increased, as is the risk of the need for alternative positioning of the IOL.

In some patients with PXF, eye pressure becomes elevated after cataract surgery. Typically, such pressure rises are controlled with drops. In rare circumstances where the pressure is unable to be controlled in this way, glaucoma surgery is required.

The likelihood of zonular instability and high pressures after cataract surgery is higher if the procedure is performed when the cataract is in a more advanced state.   

Higher amounts of myopia

Patients with medium to high amounts of myopia are dependent on lens correction for most activities. Without lenses, they have their best vision very close to their face, called their “working distance”. This may be at a distance they would comfortably thread a needle or read very fine print. It may be too close however for these tasks to be performed comfortably for long periods.

Cataract surgery has the added benefit of allowing patients with myopia to have their working distance improved. The two most common outcomes for such patients are that they remain short-sighted or are made more emmetropic and have their uncorrected distance vision improved. It is important, however, to point out that there is some variation between patients and their experience for a given refractive outcome.

Patients who choose to remain short-sighted have typically become accustomed to having clear near vision without corrective lenses, something that being short sighted affords them. They choose to keep their best uncorrected vision at this short distance and are therefore able to read in most situations without glasses. There may be the occasional situation where a weak pair of reading glasses is required to read a number in the telephone book or thread a needle in low illumination. In most situations, however, they will be able to read without glasses.

Their existing dependence on corrective lenses for distance viewing will remain.

Other patients who are myopic elect to improve their distance vision without glasses. Post-operatively they are able to view most distance objects without correction, however, they require glasses for near viewing. Most patients with myopia do prefer to retain a small amount of short-sightedness following their surgery. Keeping a small amount of residual short-sightedness allows them to still achieve some vision in the intermediate range without correction. Objects that are typically viewed in the intermediate range are a price on a shelf in a supermarket, a large font on a computer screen or someone’s face across a small table. With increasing age, more of the typical day is taken up with visual tasks at this intermediate range. On the other hand, with increasing age, the necessity to see objects in the very distance becomes less. Visual tasks at this distance include driving a car, watching a television across the room or watching night sport. It can be a potential source of disappointment for a patient, particularly one with myopia, to lose their uncorrected vision in this intermediate range.

It is therefore important, in most cases, that a myopic patient who desires distance vision without correction retains a small amount of myopia to allow some uncorrected intermediate range vision.

Most patients with myopia are delighted with the reduced glasses dependence this surgery allows them. However, a couple of other issues that may limit their ultimate satisfaction also need to be considered. 

As discussed earlier, there are limits to the accuracy of achieving a particular amount of short-sightedness following cataract surgery. Even with modern technology and particular attention to the quality of biometry performed pre-operatively, the final outcome is still within a predetermined range. Most patients with myopia accept some deviation from the prediction, given their increased independence from corrective lenses.

Some patients with myopia are very particular about the distance from their face that they like to perform certain near or intermediate range tasks. Even where the final prediction is achieved very accurately, their ultimate satisfaction with uncorrected vision at this preferred distance can never be guaranteed. It may also not be possible to be certain what this preferred distance is until they have completed their cataract surgery and follow-up to achieve the final visual result. For example, their low-degree, post-operative myopia may result in their best uncorrected vision being at 90cm and their preference is to view a computer screen at 80cm. Again, patients who are highly myopic generally prefer to not have their myopia eliminated completely.

The risk of retinal detachment increases in all patients in the year or two following cataract surgery.  Short-sighted patients have an increased lifetime risk of retinal detachment when compared with non-short sighted patients. This risk is further increased post-operatively. A retinal examination is performed prior to cataract surgery to identify any specific predisposing retinal changes. If found, it is recommended these are treated. Even where this examination does not identify any changes, the post-operative risk is still increased. When a retinal detachment occurs, it requires surgery.

Cataract surgery where there is a history of prior laser vision correction (LASIK, Intralase, PRK or LASEK)

Patients who have undergone laser vision correction have typically enjoyed the benefits that this procedure offers in terms of reduced dependence on glasses for day-to-day activities. They have demonstrated their high motivation to reduce that dependence and enjoyed this benefit, in most cases, for many years.

When those patients subsequently undergo cataract surgery that history of prior laser vision correction needs to be addressed: in particular, the assumptions made about the condition of the cornea in biometry and the process used to determine the required power of the IOL to be implanted after removal of the cataract. This is because the accuracy of the refractive outcome is reduced slightly when compared with the outcome in patients with no history of laser vision correction. This has implications for their future day-to-day glasses requirement.

Numerous techniques exist to determine IOL power in this scenario. Our clinic has the state-of-the-art equivalent K feature of the Pentacam corneal topographer to optimise the accuracy of this refractive outcome.

Consequently, those situations where a patient requires glasses will change. There is also the small possibility that glasses dependence will increase.

With patients who have had their laser vision correction to address short-sightedness, their eye still has the same increased risk of retinal detachment in the year or two following surgery as a patient who has never been short-sighted.

Diabetes mellitus

Patients with diabetes have a higher rate of cataract development when compared to patients without diabetes. Also, patients with diabetes develop signs on the retina of a condition called diabetic retinopathy. Typically this condition is asymptomatic in the early stages. It is only in the late stages that diabetic retinopathy manifests, most commonly as blurred vision. Patients with diabetes require regular examination of their retina with either their optometrist or ophthalmologist to identify any features of diabetic retinopathy.

Prior to cataract surgery, It is important that any diabetic retinopathy treatment has been performed and that the management of the patient’s systemic health (blood sugar levels, blood pressure, cholesterol and smoking status) has been optimised. 

After surgery, patients will return to the optometrist or ophthalmologist for ongoing review. Even with good control of the diabetes, the features of diabetic retinopathy can deteriorate following cataract surgery. If this were to occur the patient would be referred to a retinal specialist for ongoing management of the condition.