New oculomotor characteristics of achromatopsia
Treatments include tinted glasses and/or contact lenses, low vision aids, atropine drops and a patch for amblyopia, and eye muscle surgery for nystagmus or any abnormal body posture. head and associated strabismus.
Reviewed by Richard W. Hertle, MD.
Achromatopsia is a rare autosomal recessive genetic disorder that primarily affects retinal cone cells and affects approximately 1 in 30,000. In addition to poor vision, affected children have intense blepharospasm, photophobia, dyschromatopsia and infantile nystagmus syndrome (INS).
Important special tests include color vision, optical coherence tomography (OCT), fundus autofluorescence, visual fields, electroretinography (ERG), and genetic testing, according to Richard W. Hertle, MD , chief of pediatric ophthalmology and director of the Children’s Hospital Medical Center in Akron, Ohio.
Hertle also uses eye movement recordings to characterize nystagmus and its response to treatment.
These treatments include tinted glasses and/or contact lenses, low vision aids, atropine drops and patches for amblyopia, and eye muscle surgery for nystagmus or any abnormal body posture. head and associated strabismus.
Color blindness data analysis results
Hertle described his experience with 17 patients affected by the disease from 2010 to the present. Data were collected from a prospective database that included ERG results, eye movement recordings, visual evoked responses, OCTs, photographs, contrast sensitivity functions, and genetic testing. Other tests in older children included corneal topography, MRI, and laboratory tests, if available.
He demonstrated typical OCT findings of disturbance in the outer retinal segments, particularly in the ellipsoidal area.
All 17 patients (ages 3 months to 12 years; follow-up, 1 to 10 years) underwent eye muscle surgery; 13 for an associated head-down head posture, treating a characteristic eccentric upward gaze null position. This included bilateral superior rectus recession and inferior oblique myectomy. Of the remaining 4 patients, 2 had bilateral horizontal rectal surgery for head posture and strabismus, and 1 each had bilateral horizontal rectal surgery for strabismus alone.
According to Hertle, all 17 patients had INS, with 86% having a newly described recording feature of achromatopsia, known as a double-jerk waveform, consisting of a high-frequency pendular oscillation in the frame. of the slow phase of nystagmus.
Patients had no vergence damping – that is, they did not improve when their eyes converged – or a latent component
which is typically present in 40% to 50% of patients with INS, which may make them look like fusion maldevelopment nystagmus syndrome, when in fact they have INS. They also had no spontaneous change in direction/intensity of nystagmus (periodicity). Additionally, 40% had amblyopia and 94% had head posture (mostly chin down), Hertle reported.
Mean preoperative visual acuity in all patients was poor (i.e. 20/280). After surgery, patients had a significant change, 20/180, which is a full LogMAR line of vision improvement. Hertle showed a before and after video of a patient who had significantly improved fixation, decreased blepharospasm and nystagmus 6 months after surgery. This improvement is concomitant with a significant decrease in the double jerk component of the slow phase.
Hertle said he believes contrast sensitivity is a superior measure of the visual system compared to optotypical vision in patients with nystagmus. The results indicated that at low spatial frequencies there was improvement after eye muscle surgery, while no improvement was observed at high spatial frequencies.
New findings from this study included a dominant double-jerk INS waveform; an eccentric null position of upward gaze, with a compensatory chin-down posture and improved binocular acuity; contrast sensitivity; abnormal head posture; nystagmus; photophobia; and blepharospasm after eye muscle surgery.
Hertle hypothesized that the double-twitch waveform may be due to disturbed developmental calibration between the retina, the nucleus of the optic tract, and the ocular motor system.