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Barry N. Wasserman, MD; Chrishonda C. McCoy, MD

Arch Ophthalmol. 2007;125(9):1293-1294.

Refractive surgery can improve uncorrected vision over a wide range of refractive errors. However, impaired binocularity has been reported after refractive surgery.¹ Decompensated strabismus and loss of stereopsis can be disturbing, even when visual acuity outcome is excellent. Improved stereopsis after refractive surgery is rarely reported and is usually found in the pediatric population.² We present a case of improved stereopsis after laser in situ keratomileusis (LASIK) treatment of anisometropia in an adult.

Report of a Case
A 32-year-old woman was first seen for LASIK evaluation, complaining that her eyes did not "work well together." She had been prescribed glasses at age 6 years, but she did not wear them. She denied therapy for amblyopia or strabismus. She had no significant medical history and her medication included only birth control.

Uncorrected visual acuity was 20/150 OD and 20/30 OS. Preoperative best-corrected visual acuity was 20/25 OD and 20/20 OS. Cycloplegic refraction was + 2.75 – 4.50 x 116 OD and – 0.75 – 0.25 x 80 OS. Titmus stereoacuity testing without correction yielded 5 of 9 dots (100 seconds of arc). Pupil, extraocular motility, slitlamp, intraocular pressure, and dilated retinal examination results were all normal. No contact lens trial was performed.

The patient underwent LASIK surgery with the Moria CB manual microkeratome (Moria USA, Doylestown, Pennsylvania) and the VISX STAR S4 Laser (VISX USA Inc, Santa Clara, California). At postoperative week 1, the patient stated that her eyes were working better together. Uncorrected visual acuity was 20/25 OD and 20/20 OS. Stereoacuity testing results were now 8 of 9 dots (50 seconds of arc). At 1 month after the operation, the patient felt her depth perception was "perfect." Her vision was unchanged and manifest refraction was plano – 0.50 x 146 OD and plano – 0.25 x 13 OS. Stereoacuity had improved to 9 of 9 dots (40 seconds of arc). At 7 months, she maintained Titmus stereoacuity (40 seconds of arc) and stated that the dots had become even easier to see.

Comment
Refractive surgery effectively improves visual acuity and reduces refractive error. However, it can adversely affect binocular function. Reports describe decompensation of strabismus following refractive surgery, with resultant esotropia, exotropia, or hypertropia.¹ The strabismus can lead to asthenopia or even diplopia.³ In cases of monovision refractive surgery, some patients will lose subjective depth perception.⁴ Stereoacuity may be difficult to recover, even when monovision is reversed with correction.

This case presents improved stereopsis in an adult with long-standing anisometropia. Despite minimal amblyopia in the right eye (best-corrected visual acuity, 20/25), her subjective and objective binocularity improved within 1 week after LASIK. She further improved to 40 seconds of arc at 1 month after the operation, which was maintained at 7 months. She did have some optical correction as a child, which may have yielded her some increased stereoacuity potential. Her preoperative decreased stereoacuity may have been related to her not wearing corrective devices and may have improved with contact lens trial. However, she had a subjective and objective improvement with time after LASIK resolved her anisometropia. In a MEDLINE search, we were unable to find cases in which an adult patient had improved stereoacuity after refractive surgery.

Patients with a history of strabismus or undergoing monovision refractive surgery should be warned of decreased binocularity. However, some patients with anisometropia may experience an improvement in binocularity after refractive surgery.

AUTHOR INFORMATION
Correspondence: Dr Wasserman, Department of Pediatric Ophthalmology, Wills Eye Hospital, 840 Walnut St, Philadelphia, PA 19107 (bwasserman{at}americansurgisite.com).

Financial Disclosure: None reported.

REFERENCES
1. Godts D, Tassignon MJ, Gobin L. Binocular visual impairment after refractive surgery. J Cataract Refract Surg. 2004;30(1):101-109. FULL TEXT | WEB OF SCIENCE | PUBMED 2. Phillips CB, Prager TC, McClellan G, Mintz-Hittner HA. Laser in situ keratomileusis for treated anisometropic amblyopia in awake, autofixating pediatric and adolescent patients. J Cataract Refract Surg. 2004;30(12):2522-2528. FULL TEXT | WEB OF SCIENCE | PUBMED 3. Kushner BJ, Kowal L. Diplopia after refractive surgery: occurrence and prevention. Arch Ophthalmol. 2003;121(3):315-321. FREE FULL TEXT 4. Fawcett SL, Herman WK, Alfieri CD; et al. Stereoacuity and foveal fusion in adults with long-standing surgical monovision. J AAPOS. 2001;5(6):342-347. WEB OF SCIENCE | PUBMED

SECTION EDITOR: W. RICHARD GREEN, MD

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