BLOG: ODs play pivotal role in recognizing post-cataract surgery dysphotopsias
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Dysphotopsias are a common complaint at the 1-day cataract post-op, and yet they can be frustrating to both patient and practitioner. The exam reveals a standard surgery, and the patient couldn’t be more convinced that something is wrong.
First, we should break down dysphotopsias into their two categories: positive dysphotopsia and negative dysphotopsia. Positive is, thankfully, more common and more likely to dissipate with time. Patients can describe the artifacts as a bright crescent, ring or streak, most often in their temporal vision. Shielding above the eye or wearing a brimmed hat often makes them less noticeable.
Negative dysphotopsias are described as a dark shadow, bar or blinder (think horse blinder), again often in the patient’s temporal field. (Be sure to rule out a retinal detachment!) These are more likely to persist or, if they dissipate, take years to do so rather than months. Even so, many patients will have their symptoms resolve or lessen to a tolerable amount, only being seen in certain lighting conditions. For most patients observing dysphotopsias, they only require an explanation, reassurance and a few weeks’ time to neuro-adapt. But for others, while it may appear to the provider that the patient has had a successful cataract extraction that healed well, some patients can be made miserable by their visual disturbances.
If the tincture of time isn’t enough for someone noticing positive dysphotopsia, you may consider medications to constrict the pupil. Topical brimonidine may be adequate; if not, a trial of topical pilocarpine might do the trick. Because cataract patients tend to be older, pilocarpine is often well tolerated.
And as a quick aside, for patients who are noticing dysphotopsias on their first eye but are not frustrated, one can consider proceeding with their second eye with the addition of optic capture. This technique requires the surgeon to implant the IOL into the bag, then pop the optic of the lens out and in front of the capsulotomy. The haptics remain in the bag, and the margin of the optic and the capsulotomy no longer overlap, theoretically reducing the patient’s risk of symptoms.
While nothing in life is a sure thing, reverse optic capture certainly isn’t, with patients experiencing mixed results. For this reason, it is an added element in the second eye for less bothered patients and is rarely used as a primary treatment for truly symptomatic cases. It is also often difficult to go back and use as a secondary treatment on an eye that has already undergone cataract extraction because unless the surgeon planned for it, the capsulotomy is often too large.
Alternatively, patients who are very symptomatic for dysphotopsias after their first procedure can be encouraged to postpone the second surgery for a few weeks to see if they adapt. If not, a different IOL should be considered for the second eye. More on this later.
Effects of implant design
If you’ve been in the game long enough, you might have noticed that dysphotopsias were less of an issue decades ago. The reason for this can be traced to what implants are now our go-to, specifically their edge design and refractive indices. Modern acrylic IOLs have a square edge design to lessen the incidence of posterior capsular opacification (PCO) but at the risk for more positive dysphotopsias. They are also a higher index material than PMMA, a past favorite IOL material.
This newer square edge design seems to refract light off the IOL edge onto the retina in a concentrated region. The patient interprets this as a bright line of glare in their vision. Older PMMA lenses had a rounded edge that also caught light but refracted it over a larger and apparently more tolerable area of the patient’s retina. As a profession we’ve largely moved away from PMMA not just because of greater incidence of PCO, but also because they are unfoldable and require a larger incision during surgery. However, they are still used for patients with intolerable positive dysphotopsia if surgical intervention is warranted (IOL exchanges).
Negative dysphotopsia is less understood but may also have something to do with IOL edge design redirecting light and throwing a shadow onto the retina (perceived by the patient as a dark bar); however, many factors likely have to come into play. For example, while smaller pupils seem to reduce symptoms for positive dysphotopsia, smaller pupils are thought to be a risk factor for observing negative dysphotopsia. Research continues to be done. For symptomatic negative dysphotopsia patients, some surgeons prefer a silicone IOL with a rounded edge design for lens exchanges.
Keeping this all in mind, if a patient is still significantly affected by dysphotopsias at their 1-month post-op, it might be time to bring them to their surgery team’s attention because while we want to give the patient a few weeks for neuroadaptation (even 1 to 2 months), IOL exchange becomes more difficult with time. Few surgeons want to take on such a challenge after 6 months, and patient education includes telling them that IOL exchange is a higher risk procedure than the initial cataract extraction. This education must cover the fact that a larger incision will need to be made, it may require sutures, and there is higher risk of infection and increased risk for retinal detachment.
It is also so important to listen to the patient. Dysphotopsia symptoms, especially positive dysphotopsia, can superficially be chalked up to a PCO. However, the last thing one wants to do is refer this patient for an Nd:YAG because it becomes nearly impossible to do a lens exchange for a post-YAG patient whose real issue was dysphotopsia. If you find a surgeon up to the task of IOL exchange after the patient has a compromised open capsule, it is a riskier procedure across the board and will require an anterior vitrectomy.
Optometrists play a pivotal role in postoperative care when it comes to recognizing dysphotopsia, educating their patients on its likely transient nature and comanaging with the surgeon when it’s not. Addressing symptomatic dysphotopsias has no one-size-fits-all approach, but we should start with patient education, move on to pharmacological intervention, and save surgery for those patients who remain dissatisfied with their outcome.
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