Patient selection and education, combined with careful treatment prior, during and post-surgery are key to minimising dry eye associated with cataract surgery.
Faced with an ageing population, the incidence of cataract surgery – already a common medical procedure – will continue to increase.
Dry eye disease is one of the most common causes for complaint after uneventful cataract surgeries, especially when multifocal IOLs are used.1 Numerous studies demonstrate the procedure may change corneal sensitivity, foreign-body sensation, ocular fatigue and ocular redness – symptoms associated with dry eye. Alterations to corneal nerves during surgery are increasingly recognised as key players in the pathology of postoperative dry eye and visual aberrations.2
Those who have pre-existing dry eye are likely to experience worse dry eye post-operatively.
it is of considerable value to identify patients with a damaged ocular surface and associated tear-film instability before cataract surgery
Research indicates that being aware of a patient’s dry eye prior to surgery and planning accordingly, can lead to improved patient outcomes, however assessing dry eye can be problematic.
Chao et al writes that “with the possible exception of tear osmolarity, tests used in the assessment of dry eye are notoriously non-pathognomic – lacking correlation between signs and symptoms – and have significant overlap between normal and abnormal values.3
Numerous research papers cite TearLab’s osmometry system as the fastest, most cost effective and objective measurement of tear osmolarity for diagnosis of dry eye. Based on electrical impedance, it quickly measures osmolarity of the tear film in a clinical setting using very small tear volume. Epitropoulos writes that tear osmolarity is less variable than corneal staining, conjunctival staining and Meibomian gland grading when evaluating dry eye.3
Another way to detect the likelihood of dry eye post cataract surgery is to measure Matrix Metalloproteinase-9 (MMP-9) the presence of which is elevated in tears.4
Identifying Those at Risk
According to a study conducted by Ana Gonzalez-Mesa et al, patients with tear osmolarity values of 312mOsm/L or higher were more likely to experience more ocular discomfort post-surgery.1
In a prospective, observational study researchers measured tear osmolarity between the operated and fellow non-operated eyes of 52 patients. They found no significant differences in mean tear osmolarity between the 28 men and 24 women enrolled to participate although significantly (P= 0.01) more women had hyperosmolar tear values using the 312 mOsm/L cut-off level.1
Seeking OptImal Refractive Outcomes
Tear osmolarity can also make a difference to the refractive outcomes achieved from cataract surgery by influencing the choice of intraocular lens. Dr. Alice Epitropoulos et al, explains that keratometric measurements of the anterior corneal curvature, which are a necessary component of all IOL power calculation formulas, can be impacted by an unstable tear film, the “hallmark” of dry eye disease.3
Epitropoulos’ study found repeatability of keratometry values and therefore IOL calculations was statistically significantly poorer for those with hyperosmolar tears than those with normal osmolarity. Repeatable, reliable keratometry testing was important to accurately calculate IOL powers, especially when a toric IOL was being implanted.3
“Tear osmolarity is an ideal candidate for identifying tear instability because heightened osmolarity plays a causal role in the damage, desquamation and destabilisation of the ocular surface,” she writes… “We hypothesise that it is of considerable value to identify patients with a damaged ocular surface and associated tear-film instability before cataract surgery to increase the confidence in the K measurements.”3
Femtosecond vs Phacoemulsification
A study comparing 73 patients who had femtosecond laser-assisted cataract surgery and 64 who had phacoemulsification cataract surgery found both procedures worsened dry eye post-operatively.5 Schirmer tests to evaluate the aqueous layer of tear film and tear meniscus height reflecting tear volume; non-invasive tear break up time; fluorescein staining; a subjective questionnaire and the Ocular Surface Disease index (OSDI) were all used in the evaluation.5
Femtosecond-assisted surgery was found to have a higher risk for staining and dry-eye symptoms, with patients who had pre-existing dry eye and femtosecond-assisted surgery experiencing more severe ocular surface staining than those who had conventional surgery.5
The study reported that both femtosecond laser–assisted cataract surgery and conventional phacoemulsification had an adverse effect on all measured dry eye parameters, “being most distinct at one week and did not recover to preoperative level by one month, indicating that all patients were unable to recover from dry eye symptom in the early post-operative period”.5
Foreign body sensation was the most frequentcomplaint (62.5 per cent), followed by ocular discomfort (49.2 per cent), especially at day one and the one week follow up. Subjective symptoms one week after surgery were more severe for patients who had undergone femtosecond laser surgery than those who had undergone phacoemulsification. Patients with pre-existing dry-eye who had laser-treatment had higher ocular surface staining scores than phaco-treated eyes.5
The study authors wrote, “our result has demonstrated that, although symptoms and signs may ameliorate over time, the ocular surface is more prone to damage during femtosecond laser–assisted surgery in the context of an underlying chronic dry eye. Further study is needed to identify the recovery rate from surgically induced dry eye regarding the patients diagnosed with previous dry eye and those without.”5
Prevention and Treatment
Prevention and treatment of dry eye associated with cataract surgery should commence prior to the surgery itself with the aim of protecting and improving the ocular surface. According to the Report of the Inaugural Meeting of TFOS i2, the risk of dry eye post cataract surgery can be reduced by using preoperative surveys and tests to ensure the most appropriate surgical candidates are selected in the first instance. These candidates will have a high TFBUT (>8 seconds) and a high tear volume (Schirmer test >10 mm).2
Report lead author Professor Wendy Chao writes that antibiotics and toxic preservatives should be avoided; underlying pathologies may inform treatment; and if significant keratitis is observed after the application of diagnostic drops, special therapies may be necessary in the perioperative period. Importantly, patients should be alerted to the risks of post-operative dry eye in the informed consent. During surgery, the ocular surface can be best preserved by using anaesthetics and other substances with low toxicity, speculum time should be minimised, intrasurgical dessication avoided and incisions should be as small as possible. Following surgery, antibiotics should be minimised. Additionally, Professor Chao writes, preservative-free artificial tears containing hydroxypropyl (HP)-Guar may reduce ocular surface inflammation and dry eye compared to standard treatment alone (tobramycin and dexamethasone eye drops)100.3
Summarising, Professor Chao says “careful patient selection and education, combined with preoperative, intraoperative, and post-operative treatment may improve results and patient satisfaction.”3
1. González-Mesa A, Paz Moreno-Arrones J, Ferrari D,
Teus MA, Role of tear osmolarity in dry eye symptoms after cataract surgery, American Journal of Ophthalmology (2016), doi: 10.1016/j.ajo.2016.08.002.
2. Chao Wendy, Blemonte Carlos, Benitez Jose, Bron Anthony, Dua, Harminder S, Nichols, Kelly K, Novack Gary D., Schrader Stefan, Wilcox, Mark, Wolffsohn James, Sullivan David A. Report of the Inaugural Meeting of the TFOS i2 ¼ initiating innovation Series: Targeting the Unmet Need for Dry Eye Treatment. The Ocular Surface, April 2016, Vol 14, no. 2.
3. Alice T. Epitropoulos, Cynthia Matossian, Gregg J. Berdy, Ranjan P. Malhotra, Richard Potvin. Effect of tear osmolarity on repeatability of keratometry for cataract surgery planning. J Cataract Refract Surg 2015; 41:1672–1677
5. Yinhui Yu, Huixia Hua, Menghan Wu, Yibo Yu, Wangshu Yu, Kairan Lai, Ke Yao. Evaluation of dry eye after femtosecond laser–assisted cataract surgery. J Cataract Refract Surg 2015; 41:2614–2623 Dry eye disease (DED) is one of the most frequent causes for patients to visit the ophthalmologist and is faced by cataract surgeons on a regular basis. It should be remembered that it is a progressive disease, so the symptoms get worse the longer it is left untreated. It should therefore be considered as a risk factor when planning surgery, as the visual outcomes can be significantly influenced by it.
Dr. Uday Bhatt
Dry eye disease (DED) is one of the most frequent causes for patients to visit the ophthalmologist and is faced by cataract surgeons on a regular basis. It should be remembered that it is a progressive disease, so the symptoms get worse the longer it is left untreated. It should therefore be considered as a risk factor when planning surgery, as the visual outcomes can be significantly influenced by it.
When preparing a patient for cataract surgery, the first issue is to establish whether they have dry eye. In my clinical practice, a “yes” answer from a patient to this simple question, “Do you have any ocular irritation, burning or itching symptoms?” is enough. Only after this would I consider quantifying the problem.
There are a number of DED evaluation questionnaires (Ocular Surface Disease Index, Standard Patient Evaluation of Eye Dryness questionnaire, McMonnies dry eye questionnaire, Subjective Evaluation of Symptoms of Dryness, and DEQ-5 dry eye questionnaire) that might be suitable for a clinical study but none of these are appropriate for a busy practice.1 An easy to use simpler validated questionnaire, the UNC Dry Eye Management Scale, is also available. However we are still in search of an easy tool to quantify the problem that we can easily replicate.
Increased Patient Expectations
It is a fact that we are now offering cataract surgery to our patients much earlier than we did a decade ago.2 This is underpinned by massive advancements in the field of cataract surgery that minimise the risks and also give better visual outcomes through availability of toric and multifocal IOL platforms, but at the same time we are faced with increased patient expectations.
Dry eyes can reduce the quality of vision greatly, despite an excellent cataract surgery, and therefore should not be underestimated. In the past few years, industry has sensed the importance of ocular surface health in achieving the best visual outcomes. Dry eye disease represents a rapidly advancing field, and newer techniques and devices are now commercially available to help us better make a diagnosis.
New Diagnostic Developments
As stated before, dry eye is a multifactorial problem, and hence difficult to find one test or solution to work.3 Patients should be approached from a holistic perspective to properly diagnosis the disease. For example, taking note of the skin quality on patient’s face before even examining the patient at the slit lamp. Additionally the value of a good history from the patient as well as evaluating the tear film, lid margin and ocular surface can never be underestimated.
For diagnostic purposes, new developments have been made to detect chemical changes in tears in dry eye.4 These include detection of osmolarity and MMP-9 changes in tears in dry eyes. One common thing among dry eye patients is tear hyperosmolarity.5 TearLab uses a single-use microchip embedded with gold electrodes that measure the electrical impedance of the tear fluid to measure osmolarity of a tear sample in a tiny channel in the chip. Although widely used, there is enough debate as to how much can be determined by testing this one factor. Another device called the RPS InflammaDry Detector detects the presence of MMP-9, a cytokine produced by epithelial cells experiencing inflammation that appears to be a reliable marker for the presence of early ocular surface disease and dry eye.6 A similar system called the TearScan MicroAssay System is being developed that quantifies levels of lactoferrin (a dry-eye marker) and IgE (an allergy marker) in the tear film, helping to distinguish dry eye from allergy problems.
There are some new imaging modalities found to be helpful in detecting tear film instability in dry eyes. Tomey’s Tear Stability Analysis System (TSAS) reflects rings off the surface of the tear film while taking a series of pictures, one per second. The instrument then calculates the number of areas of irregularity appearing over time and displays the results graphically. Physicians report that a more rapid climb in the irregularity score correlates with the severity of dry eye.
Another device that can do multiple dry-eye-related tests is the Keratograph 5M topography system from Oculus.7 It can do tear film meniscus measurement, meibomian gland photography (meibography), non-invasive tear film breakup time measurement, viewing of lipid layer of the tear film and also quantification of conjunctival redness (for monitoring improvement).
Although removing cells from the surface of the eye and sending them to a laboratory for testing is a more complex approach, it allows a far more detailed analysis. The EyePrim (OPIA Technologies, France) is a sampling device that’s used to obtain cells from the ocular surface for biological testing.8 It can be used without anaesthetic and is a reliable, fast, efficient and painless method. We should see some more research into this to make it a more clinically attractive option.
Restasis (Cyclosporin 0.05 per cent solution, Allergan) for DED has been around for some time but its uptake has been lukewarm due to many factors.9 Recently in July 2016, the US Federal Drug Administration (FDA) approved Xiidra (lifitegrast ophthalmic solution 5 per cent, Shire Pharmaceuticals) for the treatment of both the signs and symptoms of DED. It is a first-in-class LFA-1 (lymphocyte function-associated antigen-1) inhibitor that acts to prevent both the activation as well as the recruitment of those activated lymphocytes to the ocular surface.10 A week after the FDA approval of Xiirdra for the dry eye patients, Allergan submitted FDA application for a new device called Oculeve intranasal tear neuro-stimulator for DED associated with reduced tear production.11 This is an exciting potential option for patients suffering from this condition.
In conclusion, to have good visual outcomes following cataract surgery, dry eyes should not be overlooked. Better diagnostic tools will lead to better treatment options for DED, extending the portfolio of services of ophthalmologists to better manage their patients’ expectations.
Dr. Uday Bhatt is a cataract and laser vision correction surgeon with a subspecialty interest in cataract, the cornea and anterior segment diseases. Dr. Bhatt has special interest in collagen cross linking (CXL) for keratoconus and the latest techniques such as DSEK (endothelial graft) and lamellar surgery DALK (lamellar graft) for corneal problems. He practices at Vision Eye Institute Footscray, Camberwell and Coburg.
Dr Michael Lawless
The American Academy of Ophthalmology lists the following as risk factors for dry eye: older age, female gender, post-menopausal women, estrogen therapy, androgen deficiency and low dietary intake of Omega 3 fatty acids. This pretty much summarises many of the patients who present for cataract surgery and so it is timely that we look at diagnosing and dealing with dry eye peri-operatively.
The articles quoted here contribute to our understanding. The long, densely packed summary of the Meeting of the Tear Film and Ocular Surface Society, published by Chao in April 2016 is a marvellous summary.
Some of the other studies can be more confusing to interpret. For example, the study by Yinhui et al talks about ocular discomfort at day one. This may be due to many causes, most likely simply irritation at the entry of the primary incision site and unrelated to dryness.
Similarly the studies suggesting femtolaser assisted cataract surgery gives rise to more dryness. It is not the laser itself of course, but the fact that there is an extra step whereby the patient interface is applied to the ocular surface and this can be in place for a variable time, depending on the eyes anatomy and the skill and experience of the surgeon. This patient interface application can lead to disturbance of the ocular surface. Similarly, because it is an extra step, one or two extra drops of local anaesthetic are required and this in itself can contribute to ocular surface irritation. Therefore it is the issues around the laser process, rather than the femtosecond laser itself, that surgeons are aware of when deciding whether a femto approach is going to be better for the individual patient.
Difficulties with Dry Eye Diagnosis
How difficult it is for the profession at present, when there is increasing consensus that tear osmolarity would seem to be the gold standard for helping diagnose and manage dry eye and yet it is not widely available. It is an expensive machine to purchase and the test itself incurs a cost that needs to be paid for. The value of this test will increase as it performs a greater variety of analysis and as this happens it may tip more and more practitioners into feeling that it is necessary for their clinical practice.
In wrestling with this issue, our practice now performs tear osmolarity testing and then does a standard questionnaire – the OSDI, available as an App on an iPhone – for any prospective laser refractive or cataract patient. Tear osmolarity has to be performed prior to any other tests. It requires a consistent technique by a skilled technician and it must be done before any drops are used or tests are performed for it to be reliable. This is not something you can do part-way through testing when you think someone may have some dry eye symptoms; you have to do it ahead of time in order for it to be reliable. Early reports of inconsistencies in the readings were due to not having a suitable standard environment and the technical expertise of the person performing the test.
Optimising Tear Quality
With knowledge from the OSDI questionnaire and the tear osmolarity, we can see that patients are either clearly normal or clearly abnormal and there is a group in the middle who look reasonably normal but have a borderline abnormal osmolarity, often but not always with a high OSDI score.
These latter two groups are counselled, prior to cataract surgery that their ocular surface health is not ideal and has to be improved prior to performing biometry. As alluded to in these papers, accurate biometry and keratometry are essential for correct intraocular lens power selection, particularly with small toric IOLs and tri-focal IOLs, and so the patients are given a regime to optimise their tear quality before coming back for these tests. These might include oral Omega 3s, non-preserved tears, and attention to their lid margin disease if this is a factor, with SteriLid cleanser and sometimes non-preserved topical corticosteroids. We take as long as necessary, sometimes three weeks, sometimes six weeks and make sure the tear quality is as good as it can be prior to testing. This also demonstrates to the patient that we are going to every length possible to get them an accurate result. It also means they move through the process of surgery and the post-operative care more comfortably because their tears have been optimised and if they have tear related issues post-operatively, at least they know it was a factor prior to surgery.
So what we are effectively doing is treating the inside (oral Omega 3’s, oral Doxycycline or Azithromycin) and treating the outside with lid hygiene, SteriLid cleanser, heat, and topical non-preserved tears and topical corticosteroids, depending on the type and severity of the disease. This is with the knowledge that dry eye disease is at a 7:1 ratio, due to Meibomian gland inflammation and evaporative disease rather than true aqueous deficiency, but also understanding that as time goes on and the disease inevitably progresses, these two things merge and become almost indistinguishable in the late stages of dry eye disease.
It is not enough to have the best surgical technique and best intraocular lenses; the ocular surface needs to be healthy pre- and post-operatively to maximise what patients can achieve with modern day technologies.
Dr. Michael Lawless is recognised throughout the world as an authority in laser eye surgery. His areas of specialisation are laser vision correction, cataract surgery, lens surgery, and corneal transplants. Dr. Lawless has performed over 25,000 surgical procedures and published over 100 articles in the peer reviewed literature. He is Clinical Associate Professor at the University of Sydney and practices at Vision Eye Institute (Bondi Junction and Chatswood).