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Ophthalmology Management

Article

The impact of post-cataract CME

Strategies for preventing cystoid macular edema and the risk factors to consider.

By: Han Y. Yin, MD, Keith A. Walter, MD
Ophthalmology Management February 1, 2021 Vol 25, Issue February 2021 Page(s): 18, 20

Postoperative cystoid macular edema (CME) and postoperative pain are common complications of cataract surgery.1,2 This was first described by Dr. S. Rodman Irvine3 and later confirmed by fluorescein angiography.4 The occurrence ranges from less than 1% to as high as 19%. Postoperative CME for cataract surgery occurs 4 to 6 weeks into the postoperative period and is responsible for temporary or permanent vision loss,5 which places a burden on patients as it requires close monitoring.

A popular accepted pathogenesis involves surgical trauma to intraocular tissues, which induces the release of prostaglandins and other inflammatory mediators.6 The elevated concentration of intraocular inflammatory mediators increases the permeability of perifoveal capillaries, leading to the disruption of the blood-retinal barrier.7,8 The pathologic hyperpermeability of retinal blood vessels and compromised blood-retinal barrier allow fluid leakage across the retinal vessel wall. This results in the cystic accumulation of extracellular intraretinal fluid in both the retina’s outer plexiform and inner nuclear layers.9

The rate of post-cataract surgery CME occurrences have decreased to 0.1% to 2.35% with modern small incision on clinical exam.10,11 However, with optical coherence tomography (OCT) evidence of CME after small incision phacoemulsification, the reported rates range from 4% to 11% with some studies reporting it to be as high as 41%.12 However, most patients with CME found via angiography or OCT do not have visual changes, and most patients with clinical CME experience spontaneous improvement by 3 to 12 months.12

Here, we will discuss the strategies for CME prevention and the risk factors to consider.

RISK FACTORS

Several factors result in a higher risk of developing CME. These high-risk demographics can be broadly categorized into two groups: intrinsic and extrinsic factors with overlapping groups. Intrinsic groups include those with underlying conditions such as diabetes with or without retinopathy, glaucoma, branch retinal vein occlusion, uveitis, pseudoexfoliation syndrome, pre-existing epiretinal membrane and prior ocular surgeries, especially vitreoretinal procedures.13-18 Extrinsic factors are challenges that cataract surgeons encounter during the cataract removal process. These factors include pseudoexfoliation syndrome, intraoperative floppy iris syndrome and chronic angle closure glaucoma, which often leads to use of a pupillary expansion device (PED)18,19 and potential disruption of posterior capsule.14 While these factors are not comprehensive, they account for the majority of post-cataract CME, which are preventable with proper measures.

PREVENTION

Prevention of CME is the key, and several modalities have been proposed to prevent intrinsic factors such as tight glycemic control and preoperative anti-VEGF therapy for diabetics and retinal occlusive disorders.20,21 Adequate control of uveitis without recurrence has been proposed prior to cataract extraction.22 Removal of the epiretinal membrane prior to phacoemulsification, in combination with or after phacoemulsification, could improve patients’ vision and prevent possible CME development.23,24

Only a few methods are available to improve extrinsic factors. Intraoperative lidocaine with epinephrine have been used to improve pupillary dilation; however, many surgeons still need a PED, which prolongs phacoemulsification time.25,26 These factors increase intraoperative time, phacoemulsification energy and ocular manipulation, which is responsible for potential increase prostaglandin releases that catalyze CME formation.

Multiple topical drugs have been used to prevent pain and CME in cataract surgery, including topical steroid eyedrops and non-steroidal anti-inflammatory agents (NSAIDs). Several studies comparing topical NSAIDs to topical steroids showed lower rates of CME in the NSAIDs group.27-29 A recent meta-analysis30 found a positive therapeutic effect of NSAIDs for reducing the risk of CME and could not conclude the equivalence or superiority of NSAID with or without steroids compared to corticosteroid alone.

Furthermore, utility of NSAIDs instead of corticosteroid can potentially eliminate steroid responders and result in an IOP spike in high-risk glaucoma patients.31 While most steroid-induced glaucoma resolves after discontinuation of steroids, up to 3% steroid responders may have irreversible elevation of IOP.32 In addition, about 1% to 5% of patients with steroid-induced glaucoma need glaucoma surgery to normalize their IOP.33 All of these modalities help attenuate postoperative inflammatory response but do not directly improve most extrinsic factors.

REDUCING CME AND CONTROLLING PAIN

Topical NSAIDs have been known to reduce postoperative CME as well as control pain and inflammation, whether alone or with a steroid.34 Typically, routine cataract surgery without the protection of a topical NSAID results in 3% to 4% of patients with reduced visual acuity from CME and up to 30% with macular thickening.35

Prostaglandins formed as a result of the activation of the inflammatory cascade during cataract surgery have been implicated in producing pain, inflammation and CME.36 Prostaglandin formation is drastically reduced by NSAIDs via inhibition of cyclo-oxygenase enzymes (COX 1&2).37 In animal studies, sustained suppression of COX enzymes has been shown in all ocular tissues measured up to 12 hours after cataract surgery with the use of Omidria (phenylephrine and ketorolac injection 1% / 0.3%, Omeros).38

Recently, Omidria received FDA approval for postoperative pain and inflammation in patients undergoing cataract surgery.39 It is also indicated to maintain pupil dilation during cataract surgery, which is the main reason for its use.25,26,40,41 Omidria is not a topical drug, but a constant infusion of phenylephrine and ketorolac added to the irrigate used during cataract surgery.

Omidria helps improve cataract surgical outcomes, reduce surgical complications and reduces the need of pupil-expanding devices in femtosecond laser-assisted cataract surgery and standard phacoemulsification.25,26,40,41 These factors have influence on patient outcomes and can reduce postoperative CME rate.14,19 This drug is the first product that can improve aforementioned extrinsic factors for cataract surgery and reduce postoperative inflammation.37,38 Using intraoperative Omidria only for preventing postoperative cataract CME is being evaluated, with approximately 5% of CME found with OCT macular evaluation. This result is promising for patients with difficulty instilling postoperative drops and helps improve patient compliance rate.

SUMMARY

Postoperative cataract CME numbers will continue to rise, due to an increasing aging population in the world who will need cataract removal. However, new and less invasive strategies have been developed to mitigate surgical complexity and reduce CME, such as intraoperative use of Omidria. This finding can change the course of postoperative care and gives the possibility of not needing postoperative drops after routine small incision phacoemulsification. Also, using topical steroids with NSAIDs shows little to no difference compared to using topical NSAIDs alone in routine cases. This will lessen the drop burden on patients undergoing routine cataract extraction and can decrease the deleterious effect of steroids. Larger prospective studies are needed to confirm the efficacy of only intraoperative use of Omidria for reducing overall postoperative CME compared to other topical therapies. OM

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About the Authors

Han Y. Yin, MD, received his medical degree from Florida International University School of medicine. He completed his ophthalmology residency at SUNY Upstate Medical University and completed his cornea fellowship at Wake Forest University. Email him at hyin@wakehealth.edu.

Han Y. Yin, MD, received his medical degree from Florida International University School of medicine. He completed his ophthalmology residency at SUNY Upstate Medical University and completed his cornea fellowship at Wake Forest University. Email him at hyin@wakehealth.edu.

Keith A. Walter, MD, joined the Wake Forest Baptist Health Eye Center and department of ophthalmology in 1996 and was promoted to full professor in 2014. He is director of the Cornea and Refractive Surgery Fellowship. Also, he invented the EndoSerter, a unique single-use, disposable device used to implant donor tissue during DSAEK procedures. Email him at kwalter@wakehealth.edu.

Keith A. Walter, MD, joined the Wake Forest Baptist Health Eye Center and department of ophthalmology in 1996 and was promoted to full professor in 2014. He is director of the Cornea and Refractive Surgery Fellowship. Also, he invented the EndoSerter, a unique single-use, disposable device used to implant donor tissue during DSAEK procedures. Email him at kwalter@wakehealth.edu.

Disclosures: Dr. Walter revealed a relatioinship with Omeros.

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