Phaco associated with increase of NAION

Bascom Palmer study tracks incidence of nonarteritic anterior ischemic optic neuropathy.

MONT TREMBLANT, Canada — Phaco procedures are associated with an increased incidence of nonarteritic anterior ischemic optic neuropathy (NAION), according to a study performed by Timothy J. McCulley, MD.

A preoperative history of NAION may contribute, he added.

Previous studies have examined the issue, but none has reported whether occurrences of NAION are spontaneous and coincidental or if they are associated with phaco.

“Our data suggests that there is likely an increased incidence of NAION following cataract extraction,” he said. “All were of the delayed type, occurring in the weeks and months following a period of good visual acuity.”

Dr. McCulley, a fellow at Bascom Palmer Eye Institute in Miami, reported the results at the North American Neuro-Ophthalmology Society meeting.

Random sample

Dr. McCulley looked at all cataract procedures performed at Bascom Palmer in the years 1993 to 1997, which resulted in 10,206 records. He excluded cataract extraction by methods other than phaco, combination procedures, patients less than 50 years old and phaco cases followed outside the facility.

Within a random sample of 224 phaco cases, 7% were done on patients less than 50 years old, 7% had combination procedures and 36% were done by physicians at another facility or did not have follow-up at Bascom Palmer. This left more than 5,000 cases for study.

Three patients

Dr. McCulley found three cases of NAION within 1 year of surgery. The first was a 72-year-old female with an ocular history of epiretinal membrane in the left eye. She had borderline hypertension, diabetes and nonspecified arthritis. She underwent an uncomplicated phacoemulsification with a foldable, posterior chamber IOL. She had a retrobulbar injection. She had a non-complicated postoperative course and onset of NAION in the operative eye 29 days postoperatively.

The second case was an 88-year-old female. She had a history of a NAION in the non-operated eye 21 months prior to her surgery. She also had pseudoexfoliation in both eyes not associated with an increase in intraocular pressure. She had a past medical history of hypertension and anemia.

Her surgery also was uncomplicated. It involved phaco done through a scleral tunnel with a posterior chamber IOL. She had local anesthesia. She had an uncomplicated postoperative course until 31 days postoperatively, when she developed NAION in her operated eye.

The third case involved a 76-year-old female. She also had a history of NAION in her non-operated eye 11 years previous to surgery. She was healthy other than a mild, nondescript arthritis.

She underwent scleral tunnel phacoemulsification. She also had local anesthesia. During the surgery, a posterior capsular tear occurred, for which the surgeon performed an anterior vitrectomy. She had adequate capsular support and the posterior chamber IOL was implanted into the sulcus. She had postop cystoid macular edema. Onset of NAION was 117 days postoperatively.

Incidence calculated

Three cases out of approximately 5,000 gives a 1-year incidence of 51.8 per 100,000 cataract extractions.

Of the three cases, two patients had a history of NAION in the fellow eye. The incidence rate among patients with no previous history was 17.3 per 100,000.

A history of NAION in the fellow eye is likely a major risk factor for NAION following cataract extraction, he said.

“Our study group may have had a higher prevalence of patients with a history of NAION going into cataract extraction than we would find in the general population,” he said. “Also, cataract and NAION may share risk factors, and may account for higher incidence in our cataract extraction population.”

For Your Information:

Timothy J. McCulley, MD, can be reached at the Bascom Palmer Eye Institute, 900 NW 17th St., Miami, FL 33136 U.S.A.; +(1) 305-326-6021; fax: +(1) 305-326-6374.