At the completion of this article, the reader should…
Have an ability to effectively assess the corneal endothelium’s health.- Understand, and communicate to patients, the importance of delaying surgery to improve surgical outcomes.
- Collaborate effectively on pre- and post-operative care for cataract patients with corneal conditions.
- Identify corneal guttata and its implications for cataract surgery outcomes.
Have an ability to effectively assess the corneal endothelium’s health.
Dr Colby Hart
MBBS (Hons) BSc FRANZCO
Cataract, laser vision correction and
corneal disease and surgery
Bayside Eye Specialists, Brighton, Victoria
Optometrists can play a crucial role in addressing corneal conditions prior to cataract surgery. Dr Colby Hart says proper management of these conditions is essential to reduce complications and ensure more accurate surgical results.
Modern advancements in intraocular lens (IOL) technology, selection formulae and surgical equipment have enabled most cataract surgery patients to achieve excellent outcomes. However, corneal disease in these patients is increasingly common and is a source of patient dissatisfaction when not addressed adequately prior to surgery. When corneal conditions are not identified and managed appropriately before surgery, they can lead to postoperative dissatisfaction and diminished visual quality, even with technically successful surgeries.
The intersection of cataract surgery and corneal health is a critical area for collaboration. By working together to diagnose, manage and treat corneal conditions in the pre-operative phase, optometrists and ophthalmologists can enhance surgical outcomes and improve overall patient satisfaction.
Dry eye disease
Dry eye disease (DED) in patients undergoing cataract surgery is very common. In a recently published meta-analysis on this topic, it was estimated that 21.2% of the population suffer from meibomian gland dysfunction (MGD) and 8.1% of the population have clinical DED.1 In some studies, up to 50% of routine cataract surgery patients had central corneal staining despite being asymptomatic prior to surgery.2
Given the high prevalence of DED in patients undergoing cataract surgery, addressing and optimising this condition prior to surgery offers a valuable opportunity for optometrists and ophthalmologists to enhance clinical outcomes.
DED or not?
One important point to consider is that DED can mimic the symptoms of cataract. Both conditions cause patients to experience a reduction in visual acuity, increasing glare and light sensitivity, difficulty driving at night and reduced contrast sensitivity.3 In fact, many of the questions asked on the ocular surface disease index (OSDI) questionnaire to grade dry eye symptoms relate to these very symptoms.
This means that there are a cohort of patients who, once their ocular surface disease has been optimised, may not actually require cataract surgery. At the very least, minimising the impacts of dry eye disease on these symptoms will allow the optometrist or ophthalmologist to better understand and discuss the risks and benefits of surgery when all other reversible contributing factors have been eliminated.
DED is a complex disease process that can be influenced by many factors including: reduced tear production, ineffective tear production, chronic inflammation, allergy and lid disease.4 One component common to all forms of dry eye disease is that patients have increased inflammatory cytokines in the tear film.5 Those patients with more severe dry eye disease have higher levels of inflammatory cytokines than those with less severe disease, and these cytokines reduce after ocular surface optimisation.6,7
Basic DED optimisation techniques such as the use of preservative free lubricants, warm compresses and lid hygiene provide a good foundation for optimisation but are often not sufficient to rapidly improve the ocular surface which is required to minimise delay in patients needing cataract surgery.8
In this setting, topical steroids or ciclosporin eye drops are often required. Recent studies have shown that a four-week course of fluorometholone9 or 0.09% ciclosporin drops10 significantly improve the signs and symptoms of DED, reduces tear inflammatory cytokine levels, and don’t cause any significant steroid related complications. This optimisation improved the accuracy of refractive outcomes within 0.75D of target after cataract surgery from 88%cto 95%.10 These treatments are easily accessible by optometrists, and initiation of them at the time of referral for cataract surgery in patients with signs of DED and no contraindications to therapy can lead to improved patient satisfaction8 and refractive outcomes.10
In my experience, almost all patients are willing to postpone their cataract surgery by a month to optimise their ocular surface once they understand the significant benefits. Explaining how a short delay can enhance the precision of refractive outcomes and reduce postoperative complications helps patients appreciate the value of this approach. By prioritising the health of the ocular surface, both optometrists and ophthalmologists can achieve better long-term visual outcomes and overall patient satisfaction.
Corneal guttata
Corneal guttata is another frequently encountered condition in patients scheduled for cataract surgery. Mild, asymptomatic forms of guttae have been reported in up to 60% of the elderly population.11 Pre-operative assessment is vital for identifying patients at risk of corneal decompensation following surgery, enabling timely referral and appropriate management.
Central corneal guttata can diminish visual acuity and contrast sensitivity. Recognising this condition during the pre-operative evaluation allows clinicians to manage patient expectations regarding potential vision improvements after cataract surgery, fostering informed decision-making and improved clinical outcomes.
The most accurate way to measure endothelial cell density is using specular microscopy, a device very rarely purchased by optometrists or ophthalmologists outside of major public hospitals. In the absence of this device, it is important to have a repeatable method of examining the endothelial surface in patients requiring cataract surgery.
Endothelial guttae have a ‘beaten metal’ appearance (Figure 1) and can be visualised using the slit lamp with high magnification and a 45-degree slit beam. Transillumination (Figure 2) and specular reflection (Figure 3) techniques are also fantastic for visualising guttae and identifying those patients at risk of decompensation after surgery.
Corneal decompensation
Most people are born with around 3,000 endothelial cells per mm.2 As we age, there is a natural loss of endothelial cells which reduces this count on average to around 1,800 endothelial cells per mm2 by the age of 60. After this, we lose around 1-2% of the remaining endothelial cells per year.
Patients who have less than 1,000 endothelial cells per mm2 at the time of cataract surgery are at high risk of decompensating after surgery, and those with less than 500 endothelial cells per mm2 are likely to be experiencing symptoms of corneal decompensation which starts with morning misting that clears through the day.
Cataract surgery is often the precipitating factor in corneal decompensation, because it leads to the loss of up to 16% of remaining endothelial cells. If this tips the patient over the ‘corneal decompensation threshold’, then they will start to experience symptoms which continue to worsen as they continue to lose 1-2% of their remaining cells per year.11
Clinical evaluation endothelium
The majority of optometry and ophthalmology practices don’t have specular microscopy facilities to evaluate the endothelial cell count of every patient considering cataract surgery. Furthermore, the symptoms experienced by patients who are at high risk of corneal decompensation after cataract surgery may have completely resolved if they are being reviewed by their eyecare practitioner in the afternoon.
The health of the patient’s endothelium can be evaluated quite accurately by asking the following questions:
• Does your vision appear misty when you first wake up in the morning?
• Is your vision mistier first thing in the morning compared to later in the day?
• How many hours after you wake up does your vision usually clear?
• Is the time that it takes for your vision to clear longer now than it was three months ago?
Water is constantly flowing from the anterior chamber, into the cornea, and back into the anterior chamber through the endothelial cells. These cells have salt pumps that pump the salt out of the cornea to create an osmotic gradient which the water follows.
The other mechanism by which water leaves the cornea is by movement across the epithelium into the tear film. In a simplified way, the tear film has a combination of water and salt. When we are awake with our eyes open, the water component of the tears can evaporate, which increases the concentration of salt compared to water in the tear film. This increased concentration of salt pulls water from the cornea into the tear film to reduce oedema of the cornea. During sleep, with our eyes closed, the water component of the tear film is unable to evaporate, which reduces the concentration of salt in the tear film. Overnight, this reduces the pull of water from the cornea into the tear film and we rely predominantly on the endothelial cell mechanism to clear the cornea. In patients with compromised endothelial cells, this leads to corneal oedema.
Patients who have symptoms of morning misting are likely to decompensate further following cataract surgery. Ideally, patients with confluent guttae should have their cataract surgery before they develop these symptoms, to reduce the risk of requiring an endothelial transplant after the surgery.
As the cataracts become denser, they require more energy during the operation for removal. The surgery can also take longer, which can increase the number of endothelial cells lost. Generally, if patients with guttae are unable to achieve 6/6 vision after excluding other causes, have early symptoms of cataract such as increasing glare at night, or early lens changes on slit lamp examination, it is worthwhile referring them to an ophthalmologist for consideration of cataract surgery.
Clear communication from the ophthalmologist to the optometrist regarding the duration of surgery, amount of energy required and expected clinical course of improvement in corneal oedema in these cases are particularly important, particularly if patients are being co-managed with optometrists.
Most cases of corneal oedema after cataract surgery should have cleared by four-to-six weeks in the absence of persistent inflammation. If there is persisting oedema after this time in the settings of guttae pre-operatively, it is less likely to clear. Asking a patient to keep a diary once per week of subjectively how misty the vision is when they first wake up, and then again at one-hour, two-hours and three-hours after waking can give an insight into the trajectory of their improvement.
I ask patients to attach a printed Snellen chart to their fridge, cover the unoperated eye and stand at the same distance once per week to record this. If there are no trends of improvement after four-to-six weeks, they are likely to continue to lose the normal 1-2% of endothelial cells per year, so discussing the potential for an endothelial transplant in this setting is usually appropriate.
Conclusion
Managing corneal conditions like DED and being aware of corneal guttata before cataract surgery is essential for improving patient satisfaction and surgical outcomes. Addressing these issues proactively helps reduce complications and enhance refractive accuracy. Collaboration between optometrists and ophthalmologists ensures better long-term visual results and sets realistic patient expectations, ultimately leading to improved cataract surgery outcomes.
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References
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