Cataract surgery is the most common outpatient procedure worldwide. With advancements in biometry, it is increasingly viewed as a refractive procedure.
Additionally, as premium intraocular lens (IOL) selections (and their prices) continue to grow, so do patient expectations.
As co-managing optometrists, it is our job to ensure a full understanding of potential outcomes before surgery and to treat complications after.
Assessing post-operative refractive error
The first step in explaining visual outcomes to a patient is understanding all components that influence post-operative refractive error. Keratometry, axial length, and anterior chamber depth are the most important parameters in IOL calculation and subsequently visual outcome.1
A refractive surprise, which is failure to achieve intended post-operative target refraction, may result from errors in pre-operative biometry.2 Discrepancies may occur due to technical errors while obtaining the measurement or if the eye falls outside the parameters of a statistically “normal” eye.3
High ametropia, exceptionally long or short axial length, and irregular corneal astigmatism can all lead to less accurate measurements and IOL calculations. Common sources of irregular corneal astigmatism include prior refractive surgery, chronic dry eye, contact lens wear (rigid and soft), pterygium, and corneal scarring.
Factoring in IOL position after cataract surgery
The proper position of the lens is also essential to post-operative refractive error. Forward deviation of the IOL can lead to myopia, and backward deviation leads to hyperopia. Decentration or tilt may also influence post-operative refractive error by inducing increased astigmatism and coma aberrations.4
Standard monofocal lenses tend to be less impacted by decentration than multifocal lenses.5 In toric lenses, a 1° rotation results in a 3.3% loss of astigmatism correction.6 Lens rotation increases in patients with large white-to-white values (horizontal corneal diameter), and a surgeon may decline implanting a toric lens if the value is too high.
Addressing post-operative decreased vision
Overall, most patients (73 to 98%) report satisfaction with their vision after cataract surgery.7 It is difficult to define success in the visual outcome as it has objective and subjective components.
One study considered uncorrected visual acuity of 20/60 and better a success.8 From my experience, we consider 20/40 or better uncorrected to be a normal expectation. Despite advancements in technology, patients can still forget that the goal of cataract surgery is also to remove their glasses correction (in addition to their cataract). While some pseudophakic patients may still rely on spectacle correction for various tasks, their dependence on glasses is significantly reduced after cataract surgery.
“Patients may also compare their post-surgical uncorrected vision to their previous corrected vision.”
Reminding them of the initial goal and giving them quantitative results of their improved vision may ease their worries. When a patient complains of poor distance vision, I have found that listening and responding with a positive attitude can go a long way. Sometimes all they need is some encouragement that their vision is fantastic or, at the very least, statistically a success.
It is also important to explain any of the aforementioned biometric parameters that decrease the likelihood of hitting the refractive target that are relevant to your patient.
Correction of residual refractive error
Residual refractive error can be adjusted with spectacle or contact lens correction. Some patients may elect to have corrective corneal-based laser refractive surgery depending on corneal thickness. Some surgeons offer complementary refractive surgery should a patient be dissatisfied with their visual outcome with a premium lens. In these instances, it is essential to explain that correction of any residual myopia or astigmatism will compromise their uncorrected near vision.
Other options to correct large refractive errors are piggyback lenses or IOL exchange when an excimer laser is not available, or corneal thickness is insufficient.9 These options are typically reserved for more extreme cases due to the risk for complications, including corneal endothelial decompensation, posterior capsular rent, vitreous loss, and persistent unsatisfactory visual outcome.10
Optometrists play with physical optics every day, and it can be easy to forget how complicated and confusing it is to someone without the proper background (e.g., most patients). I often see patients express disappointment with their vision despite 20/20 uncorrected distance acuity. After speaking to the patient, it is clear they do not understand the principles of a monofocal lens.
Reminding them that needing a bifocal or reading glasses is perfectly normal after surgery is comforting, and a quick discussion about task-oriented reader strengths may leave them satisfied.
Using presbyopia-correcting IOLs
Presbyopic correction with a premium lens is a delicate balance of visual quality and depth of field. If a patient with a presbyopia-correcting lens is struggling with reading, the answer to their problem may depend on which lens was implanted. There are true multifocal lenses, including trifocal and bifocal, extended depth of focus lenses (EDOF), and newer hybrid and monofocal EDOF designs.
For true multifocal lenses (most commonly J&J Tecnis, Alcon ReStor, and PanOptix), a diffractive lens technology is used to provide simultaneous distance and near vision. While this advanced technology gives good distance and near vision (plus intermediate for PanOptix), it does so by dividing the light into different focal points, resulting in reduced contrast sensitivity. We can compensate for this loss of contrast by having the patient increase lighting while reading; this can be easily demonstrated in-office.
If a patient selects an EDOF lens (Alcon Vivity or J&J Tecnis Symfony), a refractive design is used to create an elongated focal point rather than two or three discrete foci.11 This design allows for better distance and intermediate vision but provides less near vision than its multifocal counterparts.
“Thus, a low power reader is often required for fine print or extended near work in these patients.”
Although EDOF lenses have shown less reduction in contrast sensitivity than multifocal lenses, there is a reduction compared to monofocal lenses, and they will also notice improved near vision with more lighting in their environment.12
Lastly, all post-operative cataract patients have been trained for years to hold reading material at a fixed working distance relative to their prescriptions. This “sweet spot” may change after having surgery. Occasionally, a patient’s complaint may be easily fixed by having them bring the material closer and further according to their implanted lens and post-operative refractive error.
Managing post-operative positive and negative dysphotopsia
Pseudophakic dysphotopsia is a term designated to any light-related visual disturbance encountered by a patient after cataract surgery.13 Patients may complain of light streaks, arcs, a shimmer, or starburst. These symptoms of positive dysphotopsia are typically induced by oblique light. Positive dysphotopsia is thought to be caused by optic edge, IOL material, and reduced optic diameter.
Conversely, negative dysphotopsia is also possible and perceived as a dark, temporal peripheral arc-shaped shadow. Incidence of negative dysphotopsia is as high as 49% during immediate post-operative care; however, it decreases to 0.2% to 2.2% over the following year.14 Negative dysphotopsia may be attributed to lens design (material, edge thickness, optic size), pupil size, edema from incisions, distance between the iris and IOL, and anterior phimosis.
Approximately 15 to 20% of patients experience this early, and this number decreases to 3% at 1 year.15 The reduction in symptoms comes with neuroadaptation. Multifocal and EDOF lenses are more likely to cause symptoms of glare and halo due to their unique designs with high add models, causing more severe symptoms.16 Typical neuroadaptation occurs as early as 3 months and as late as 1 year after cataract surgery.17
Kindly remind your patient that they have lived with their natural lens for 60+ years and it is normal to take up to a year to completely adapt to their new optic system.
Other potential complications after cataract surgery
All other sources of decreased vision or glare must be assessed and ruled out before allowing for proper neuroadapation.
1. Post-operative dry eye disease
Dry eye disease can occur in up to 37.4% of patients who did not previously have dry eye after cataract surgery.18 Risk factors for post-operative dry eye are older age, female sex, systemic or psychiatric disease and medication, pre-existing dry eye or meibomian gland dysfunction, preservatives in eye drops, surgical technique, and lifestyle.
Post-operative dry eye symptoms include discomfort, ocular fatigue, and decreased vision. Peak dry eye symptom severity appears to occur 1 day to 1 week after surgery; however, several studies have noted severe symptoms persistent throughout the duration of the study (one year). Corneal denervation and reduced tear film break-up time return to baseline within 1 to 3 months of surgery.19
Managing dry eye disease after cataract surgery
Although several components leading to post-operative dry eye are out of our control, we can treat, monitor, and reassure these patients. Preservative-free artificial tear use, especially hyaluronic acid-based drops, reduces dry eye symptoms and improves the clinical outcome after surgery.20
Over-the-counter remedies are first line; however, more complex topical medications such as cyclosporine and diquafosol (not available in the US) are being prescribed more frequently with success.21
2. Post-operative posterior capsule opacification
Posterior capsule opacification (PCO) is the most common complication in cataract surgery, occurring in up to 50% of patients.22 This occurs when residual lens epithelial cells in the capsule proliferate and differentiate into myofibroblasts, spreading and forming a film over the intraocular lens. PCO typically occurs within the first 2 to 5 years after surgery; however, up to 30% of patients may develop PCO in the first 3 months after surgery.23
Patient age is an important risk factor; children are expected to have a 100% risk and patients under 40 years are expected to develop PCO three times more quickly than those over 60 years.24,25
Treating posterior capsule opacification after cataract surgery
PCO is treated with Nd:YAG laser capsulotomy. Treatment is indicated if the patient reports impairment in needed or desired activities attributed to decreased vision, thorough anterior and posterior exams have ruled out further pathology, best-corrected visual acuity 20/50 or worse, or best-corrected visual acuity decreases two lines with glare. Insurance will contribute or cover the procedure if the above requirements are met.26
Complications of Nd:YAG capsulotomy include retinal detachment, cystoid macular edema, IOL displacement, anterior uveitis, and increased intraocular pressure. These risks should be weighed against the severity of PCO when counseling the patient on pursuing treatment.
3. Post-operative Irvine-Gass syndrome
Irvine-Gass syndrome is defined as the presence of cystoid macular edema or central macular thickening following cataract surgery.27 Irvine-Gass syndrome is a common complication; however, the exact incidence varies widely due to varied diagnostic criteria based on clinical findings and visual impairment. Optical coherence tomography (OCT) of the macula shows cystic intraretinal spaces and may include small areas of photoreceptor detachment.28
Fluorescein angiography is the gold standard diagnostic tool in combination with OCT to rule out other causes of macular edema and shows a characteristic petaloid macular leakage pattern.
Cystoid macular edema (CME) causes vision impairment in 1 to 2% of patients and peaks 6 weeks after surgery.29 Subclinical edema can be seen in about 30% of patients on fluorescein angiography and up to 40% on OCT. The presence of epiretinal membrane, history of uveitis, diabetes, and topical glaucoma medications increase the risk for CME. The exact etiology has not been defined, but multifactorial inflammation seems to be the agreed-upon pathophysiological origin.
Treating Irvine-Gass syndrome after cataract surgery
Uniform treatment has also evaded consensus. Treatment with topical non-steroidal anti-inflammatory drugs (NSAIDs) shows improved function and morphology. Topical NSAIDs combined with oral carbonic anhydrase inhibitors may be more effective than NSAID alone; however, the sample size is small. The addition of topical corticosteroid shows questionable efficacy.29
The most accepted approach is initial treatment with topical NSAID. There is no established timeline for the application of more invasive treatments, such as periocular and intravitreal injections. Although the definition of refractory edema based on duration remains unclear, it is common to employ advanced treatment at 3 months, and patients should be referred to an ophthalmologist accordingly.
Final thoughts on co-managing complications from refractive cataract surgery
As the demand for ophthalmic surgery increases, post-operative co-management with optometrists is becoming more common. Many ophthalmologists recognize our merit and eagerness to assist in patient care and will happily agree to co-management.
Although we do not perform surgery, it is essential for us to have a thorough understanding of pre-operative, intra-operative, and post-operative facets that affect our patients. Being well acquainted with all aspects of cataract surgical care and keeping open communication with the surgeon builds trust.
This bond between optometry and ophthalmology is a major stepping stone to practicing full-scope optometry and pushing our scope to match our potential.
