Diplopia: Seeing clearly but double

Baltimore-Diplopia is an unexpected and unwelcome complication that can occur-albeit rarely-after refractive surgery, said Hee-Jung Park, MD, MPH.

The key to preventing this complication is a careful history-taking and preoperative evaluation, she stressed.

"Sometimes after an uneventful cataract or refractive surgery, strabismus rears its ugly head," said Dr. Park, assistant professor of ophthalmology at the Krieger Children's Eye Center at the Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore. "Patients come to our service saying that they can see clearly, but double.

The incidence of diplopia that persists after that time period is low, ranging from 0.67% to 0.85%. Ophthalmologists must work to identify patients and associated risk factors to prevent this diplopia, Dr. Park noted.

Case study

Dr. Park presented a few case studies of patients who presented with postoperative diplopia. The first patient was a 32-year-old veterinary surgeon who presented 6 months after LASIK surgery with the main complaint of having difficulty with near work, and fatigue after trying to focus. To do near work, she had resorted to closing one eye.

The patient's visual acuity at distance was 20/20, and at near, 20/20 in both eyes. Manifest refraction showed slight over-correction after the refractive surgery. She was orthophoric at distance without spectacle correction. However, at near, she developed an intermittent esotropia of 18 prism diopters (PD) with moderate control.

With +1.75 D of near correction, her deviation improved a to an esophoria of 8 PD. With stronger reading prescription of +2.50 D, her deviation improved further to esophoria of 4 PD. Randot stereo-acuity without glasses measured 200 seconds of arc. By increasing the reading add to +2.75 D, her stereo-acuity improved to 25 seconds of arc.

The results of this patient's preop evaluation were:

This patient reported during the preoperative visit that she needed to remove her glasses for near work and mentioned that she could not read while wearing her distance glasses.

This veterinary surgeon was dissatisfied with the need for reading glasses for her daily work. She opted for strabismus surgery and underwent bimedial rectus recessions with a good outcome. However, 3 years later, the patient developed recurrent esotropia at near and returned to using the reading glasses. She was unhappy with the outcome of the surgery, even though her visual acuity was excellent.

"This patient had accommodative esotropia in a setting of myopia," Dr. Park said. "This is not a common combination, but it does exist, and we have to be aware of these patients. And [patients with early presbyopia] can manifest accommodative esotropia.

"Had this patient's deviation been measured with the target refractive correction preoperatively, this problem could have been identified prior to surgery," she added.