Nystagmus & Laser Vision Correction

by | Feb 1, 2025 | Grand Rounds | 0 comments

CASE OVERVIEW

A 23-year-old male with a history of horizontal nystagmus and contact lens intolerance was interested in vision correction surgery. Refractive error in the right eye was -3.50 -1.75 x 65, which allowed 20/30 acuity, and in the left eye, -4.75 -2.00 x 170, which allowed 20/40 acuity.

Corneal thickness measurements were 540 microns in the right eye and 557 microns in the left eye. Computerized topography showed no evidence of irregular astigmatism. Anterior segment examination was normal except for the finding of the horizontal nystagmus.

WHAT ARE THE TREATMENT OPTIONS TO CORRECT HIS MYOPIA AND ASTIGMATISM ? DOES THE NYSTAGMUS INTERFERE WITH AN IDEAL OUTCOME?

Both LASIK and PRK are reasonable options to obtain best uncorrected acuity. Given the finding of horizontal nystagmus, it was felt that PRK would be a safer option to decrease the potential of flap slippage and the need for surgical repositioning.

WHAT WAS DONE:

PRK was performed in both eyes, and a rotary brush was used to remove 9 mm of central epithelial cells in both eyes. The high speed active eye tracker was used at the time of the excimer ablation treatment. Mitomycin C was applied for 30 seconds to decrease the risk of corneal haze.

Postoperatively, the eyes healed well, and the bandage contact lenses were removed at 5 days. Uncorrected acuity continued to improve, and at 3 weeks postop, he had an uncorrected acuity of 20/40 in the right eye and 20/50 in the left. This gradually improved over time, achieving an uncorrected acuity which was similar to the preop best corrected acuity.

KEY LEARNING POINTS:

1. VISION WILL BE LIMITED: Patients with nystagmus can have laser vision correction, however the vision will be limited secondary to the involuntary eye movements, which prevent a steady foveal image.
 
2. QUALITY OF VISION: This is typically better after laser vision correction than glasses, because the laser ablation is centered over the pupil. With glasses and nystagmus, the patient is not always focused in the center of the glasses.
 
2. EXCIMER LASER EYE TRACKERS: Sophisticated and fast eye trackers are available on all excimer systems today to ensure a well centered ablation. Over 20 years ago, eye trackers were not available, which increased the risk of a decentered ablation.
 
3. LASER VISION CORRECTION OPTIONS: While PRK may be preferred over LASIK in nystagmus patients due to avoiding flap-related complications, careful patient selection and counselling regarding realistic expectations is essential.
 
4. UNDERSTANDING NYSTAGMUS: Nystagmus can be horizontal, vertical, or rotary. It can be congenital or acquired. Acquired nystagmus may be associated with serious health conditions, especially those affecting the brain, such as stroke, brain tumour, toxicity (alcohol or drug use), or head trauma. Inner ear problems may be a cause of nystagmus. Sometimes there is no identifiable cause for acquired nystagmus and this is referred to as idiopathic nystagmus.