June 2018

COVER FEATURE

Neuro-ophthalmology for the anterior segment surgeon
Does cataract surgery increase the risk of NAION in some patients?


by Vanessa Caceres EyeWorld Contributing Writer


Fundus of a patient with NAION

The fellow eye
Source: Neil Miller, MD


Some neuro-ophthalmologists think the risk for postop NAION is much lower now; others think there is still a higher risk and advise waiting on fellow eye surgery until there is significant visual compromise if NAION has occurred in the first eye.


Study finds a lower risk nowadays, but not all ophthalmologists agree

How high is the risk for nonarteritic anterior ischemic optic neuropathy (NAION) after uncomplicated cataract surgery?
Results from a study published in 2017 questioned long-held beliefs on this topic.1 However, not all ophthalmologists are ready to change their mind on the risk level.
The retrospective cohort study, published in the American Journal of Ophthalmology, focused on the prevalence and incidence of post-cataract surgery optic neuropathy (PCSON) with the use of today’s modern cataract techniques. Cases of NAION have been documented after uncomplicated cataract surgery, and these can appear immediately postoperatively or days, weeks, or months after surgery, the authors wrote. They also cited previously reported data that found when PCSON occurs after cataract surgery in one eye, there is a 53% risk of a similar event occurring in the fellow eye if it also has cataract surgery.
Some ophthalmologists think there is a link between optic neuropathy and increased IOP, raised intraorbital pressure from a retrobulbar or peribulbar anesthetic, systemic perioperative hypotension, or a combination of these factors.
Although exact causes of the delayed form of NAION are unclear, there may be a connection with intraocular surgery-related posterior pole edema as this involves the nerve and results in vascular compression, according to the study’s authors.
Because of changes in anesthetic and surgical techniques, the authors decided to investigate the incidence and prevalence of post-cataract surgery optic neuropathy.
Study researchers included patients with a diagnosis of NAION as identified with the ICD-9 diagnostic code 377.41 (ischemic optic neuropathy), which led to 651 patients. These patients were seen within the Wilmer Eye Network system between 2010 and 2014. Inclusion criteria included a history of acute unilateral vision decrease, a visual field defect consistent with NAION, a relative afferent pupillary defect, and observed optic disc swelling.
The main study outcome measure was the prevalence and incidence of PCSON and the temporal association between surgery and PCSON onset. A secondary outcome was the risk of PCSON in the fellow eye in patients who had a prior unilateral spontaneous NAION.
Among the 651 patients, 165 of those (25.3%) were excluded because their NAION took place before the study period, and another 114 (17.5%) had experienced NAION but did not meet the other study inclusion criteria. Yet another 184 patients were excluded because their visual loss was subsequently linked to a process other than NAION, such as retinopathies or optic neuritis.
Ultimately, 188 patients with NAION were included in the study, with a median age of 63.8 years. Fifty-three percent of the patients were male, and 88.8% of all patients were white.
Among the study group, 18 patients (9.6%) had a history of ipsilateral cataract surgery within a year prior to developing NAION (the PCSON group).
There was a total incidence of 10.9 cases per 100,000 (95% CI, 1.3, 39.4). No significant temporal pattern was associated with NAION case distribution. Among the 18 patients who had cataract surgery within the previous year, 17 had bilateral sequential cataract surgery. Of these, four (23.5%) had developed bilateral PCSON, whereas in 13 (76.5%), the PCSON was unilateral. “Of the 13 patients with unilateral PCSON after bilateral sequential cataract surgery, five had developed it in the first operated eye but not in the second, and eight had developed it in the second operated eye but not the first,” the authors wrote. All patients in the group were older than age 58 (median age, 71 years), and 14 had at least one known systemic disease that has been considered a NAION risk factor.
Local anesthesia was used in all but one procedure; topical anesthesia was most commonly used, followed by retrobulbar and sub-Tenon’s anesthesia.
No patients had immediate postop NAION; in fact, the median interval between cataract surgery and NAION was 173 days, with a range of 9–328 days, according to the authors.
The analysis found that spontaneous NAION was more common in current smokers and in those with hyperlipidemia compared with the PCSON group.
The findings led the authors to conclude that the prevalence and incidence of NAION after cataract surgery are comparable to those of the general population and that there is no significant temporal relationship between modern cataract surgery and the subsequent development of NAION in the operated eye. “We suspect that this difference reflects the shift in cataract surgery methods over the last few decades, from intracapsular and extracapsular methods with retrobulbar or peribulbar anesthesia to a predominantly phacoemulsification technique, carried out under topical anesthesia,” the authors wrote.
The study acknowledged that use of a single ICD-9 diagnostic code for NAION could be a potential source of error. “[S]ome patients with NAION may have been assigned, at least initially, an incorrect or inadequate diagnostic code, such as visual field defect, optic disc edema, or optic disc swelling,” they wrote. Although this could invalidate the results if it occurred even one or two times, all of the patients were examined by neuro-ophthalmologists who would have made the appropriate diagnosis, said study author Neil Miller, MD, Frank B. Walsh Professor of Neuro-ophthalmology, Wilmer Eye Institute, Johns Hopkins School of Medicine, Baltimore.

On the other hand

Not all surgeons are convinced that the risk of NAION after cataract surgery is as low as this study found. In an editorial published in the same journal issue as the study, Timothy McCulley, MD, associate professor of ophthalmology, Wilmer Eye Institute, Johns Hopkins School of Medicine, Byron Lam, MD, professor, Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, and William Feuer, MD, Bascom Palmer Eye Institute, shared their thoughts about the NAION study.2 They pointed out the study’s use of only one diagnostic code to identify NAION and a small sample size with a very large confidence interval. “The hazard in underestimating the risk of NAION associated with cataract surgery lies in the second-eye involvement. …With the potential devastating consequence of bilateral NAION, proceeding with caution when considering cataract extraction in patients with a history of NAION seems prudent and appropriate,” the editorial authors wrote.
The editorial authors do think that the risk of NAION has likely decreased with modern cataract surgery techniques, just not as much as the study identified.

Take-home pearls

What should cataract surgeons and neuro-ophthalmologists advise patients regarding the risk of NAION after cataract surgery? EyeWorld asked a few of the authors from the study and the editorial to share their take-home message. Here’s what they shared.
“I used to tell patients who had post-cataract NAION in one eye that they had a 50% risk of developing a similar event in the other eye and that they should not undergo cataract surgery unless they were truly unable to perform their daily activities because of poor vision in the second eye,” Dr. Miller said. “I now tell them that we used to think this was the case, but that I do not think this is the case any longer. I also tell them that if they do undergo cataract surgery, they should have it performed under topical anesthesia.”
Ahmadreza Moradi, MD, Mount Sinai Health System, New York, an author of the NAION study, said, “Our study could not support the idea that patients who have experienced NAION in one eye have an increased risk of NAION following non-complex cataract surgery in the fellow eye.”
“I have no doubt cataract surgery or other intraocular procedures can be a trigger factor for NAION,” Dr. Lam said. “This is particularly true when the surgical procedures are complicated by surgical trauma and increased intraocular pressure. … If a patient has NAION in one eye, I would defer cataract extraction in the fellow eye until the cataract has a notable impact on activities of daily living.”
“Where it becomes important is if there is a history of [ischemic optic neuropathy] in one eye, whether it’s associated with cataract surgery or not, and then having cataract surgery in the other eye,” Dr. McCulley said. “Three points of advice: (1) Make efforts to not have a pressure spike to trigger optic neuropathy. (2) Do whatever you can to control inflammation. Work with a seasoned surgeon. (3) If the patient is borderline on the cataract’s visual impact, wait till the patient really needs it, until there is more substantial visual compromise.”

References

1. Moradi A, et al. Post-cataract surgery optic neuropathy: Prevalence, incidence, temporal relationship, and fellow eye involvement. Am J Ophthalmol. 2017;175:183–193.
2. McCulley TJ. Nonarteritic anterior ischemic optic neuropathy and intraocular surgery. Am J Ophthalmol. 2017;175:xiv–xvi.

Editors’ note: The physicians have no financial interests related to their comments.

Contact information

Lam
: blam@med.miami.edu
McCulley: tmccull5@jhmi.edu
Miller: nrmiller@jhmi.edu
Moradi: ahmadreza.moradi1@gmail.com

Does cataract surgery increase the risk of NAION in some patients? Does cataract surgery increase the risk of NAION in some patients?
Ophthalmology News - EyeWorld Magazine
283 110
220 200
,
2018-05-28T13:48:17Z
True, 6