Dichoptic Rescue for Spectacle-Flip Sabotage of Anisometropic Amblyopia Therapy

Introduction

Successful amblyopia therapy is at the mercy of compliance.¹

The Pediatric Eye Disease Investigator Group (PEDIG) amblyopia treatment studies (ATS) have demonstrated that successful amblyopia therapy for patients younger than 10 years of age with strabismic and/or refractive etiologies involves correction of refractive error, and then consistent part-time occlusion and/or atropine penalization of a non-myopic sound eye.² Dichoptic therapy, especially the recently approved Curesight (Novasight, Airport City, Israel) can improve amblyopic visual acuity and stereopsis.³ Part of the advantage of Curesight with eye tracking is virtual, real-time monitoring of treatment compliance.

Hyperopic anisometropia is a common cause of profound amblyopia. If spectacles are not prescribed early enough, then anti-suppression therapy such as part-time patching is usually added to the spectacles. If patching compliance is not satisfactory, then atropine 1% is often prescribed for the sound eye. The only way an atropinized, hyperopic sound eye could resolve near images would be to have a high plus lens over it.

A novel treatment is described for a young patient who discovered that Spectacle-flip allowed her to enjoy near video games during amblyopia therapy. The spectacle-flip effectively sabotaged or incapacitated the beneficial value of anisometropic hyperopic glasses plus atropine penalization.

Case Report

A bright 5-year-old Alaska Native girl with severe anisometropic refractive amblyopia had been referred to our pediatric ophthalmology specialty clinic. One year earlier, her optometrist diagnosed her with amblyopia, gave her spectacles and offered part-time patch therapy over her left, sound eye. Unfortunately, in her foster living situation, she peeled off her occlusion patches so the therapy produced family frustration but not better visual acuity.

A confirmatory exam revealed cycloplegic refraction right eye of +6.00 +0.50 x 88 and left eye of +1.00 +0.50 x 92. Her patched HOTV acuities were logMAR 0.9 right eye and logMAR 0.0 left eye. She had stereo acuity 400 seconds of arc and alignment of 5 PD micro-esotropia without nystagmus. Her optic nerves and maculae appeared normal. She was prescribed new spectacles and informed of various additional amblyopia treatment options. The time course of her best corrected visual acuity and stereo acuity are shown in Figure 1. Details (metric and USA) of her clinical course are shown in Table 1.

Table 1 Characteristics of Anisometropic Amblyopia Patient

She returned to be considered for the multi-center, USA randomized clinical trial of CureSight dichoptic therapy. Patched, calibrated M&S Clinical Trials Suite EVA surround HOTV acuities were logMAR 0.9 right eye and left eye logMAR −0.1. She had 5 prism diopter distance esodeviation and 400 seconds of arc stereo. Unfortunately, the poor amblyopic visual acuity disqualified her for the Curesight clinical trial, therefore atropine 1% drop daily on weekends was prescribed for the sound, left eye.

Figure 1 Time course of prior and dichoptic amblyopia therapy including spectacle-flip sabotage while on atropine for anisometropia therapy. Notes: Best corrected visual acuity (logMAR) is plotted versus age in months with the amblyopic right [R] eye in blue and the sound left [L] eye in dark red. Stereo acuity in arc seconds shown at the top with details in the text. Comparative mean visual acuity and age for the Israel multicenter CureSight study are superimposed in orange, data from Wygnanski-Jaffe et al.3

Over the next three months, she observed that her dominant left eye was blurry for screen viewing with the atropine drop however she discovered she could flip her spectacles placing the higher plus lens in front of her cyclopleged, sound left eye making near work more enjoyable. She either slid her glasses sideways or flipped them upside down. Her spectacles measured +4.50+1.00×90 right amblyopic eye and +0.50+1.00×90 sound left eye. Her guardian was favorably impressed with her new-found interest in near activities. On examination, patched HOTV was logMAR 1.0 right eye and the left atropinized eye diminished to logMAR 0.4. Her guardian was warned about the adverse impact of the flipped-spectacles method of viewing near detail. Atropine was stopped and she was instructed to desist from flipping her spectacles. A special IRB was sought to allow her an option at dichoptic therapy.

The legal guardian provided signed, informed consent to a modification of the CureSight clinical trial that allowed enrollment with worse levels of amblyopia in children over a wider range of entry ages (WCG IRB study number 1349156, Protocol #20230623, Clinical Trials registration NCT06165705). Her enrollment visual acuity was logMAR 0.9 right eye and logMAR 0.0 left eye.

A CureSight table top computer console left over from the USA FDA clinical trial was retro-fit with a new Tobii eye tracking device that was held with magnets below the monitor screen. The patient and guardian were oriented to the device and commenced therapy prescribed as 90 minutes per day, six days per week using home internet delivered content (YouTube videos) that CureSight real-time split into a blue channel for the right amblyopic eye and a red channel that presented eye-tracking aimed central blur when viewed through specifically prescribed anaglyph goggles over her existing spectacles.

After one month of prescribed CureSight, right eye acuity was 0.7 logMAR while the left eye was −0.1 with 140 sec arc Titmus stereo. PDI Check dynamic autostereoscopic stereo was 428 sec arc.⁴

One month later, WiFi had been less reliable in different home and she was wearing an old pair of spectacles. However she was enjoying 90 minutes per day viewing YouTube on the CureSight. Visual acuity right eye was 0.8 logMAR and left eye −0.2 logMAR however she required being held from creeping up to lean too close to the M&S screen for patched acuity testing. The PDI Check dynamic stereo was 85 seconds of arc stereo.

One month later her compliance for home therapy remained a challenge even though she enjoyed watching the YouTube videos. She tried to view with her spectacles off but the CureSight would remind her not play until correct spectacles were on. She would also dislodge the Tobii eye tracker from its magnetic position, and again the CureSight would not play video until the eye-tracker was in position. Visual acuity right while she tried to peak with sweaty eye patches was logMAR 0.8 in her old glasses and acuity left was logMAR −0.2. PDI Check stereo was 71 seconds of arc. New spectacles were provided.

Two months later with the new spectacles compliance on her CureSight online monitor was a consistent 90 minutes per day and she was enjoying Kindergarten. Visual acuity right eye improved to logMAR 0.6 and left eye logMAR −0.2. Titmus stereo was 200 seconds of arc while PDI Check was 211. Her ocular alignment and refraction remained stable At the conclusion of this intervention, both patient and guardian continued to enjoy the CureSight dichoptic therapy especially compared to their prior experience with patching or atropine.

Discussion

When amblyopia therapy requires compliance several methods have been devised to enhance, monitor and follow patients.^{5, 6} Occlusion therapy can have compliance improved with elbow splint arm restraints,⁷ shutter goggles,⁸ taping over the patch,⁹ glue on the patch,¹⁰ sewn-on occlusion shields¹¹ or opaque contact lenses.¹² Blurring the sound eye with a cycloplegic drop like atropine may have better compliance than patching¹³ and compliance with blur can be enhanced by modifying the lens on the sound eye,¹⁴ using Bangerter foils¹⁵ and dichoptically blurring part or all of the sound eye image.¹⁶ The motivation to comply with therapy can be improved by child-preferred patches,¹⁷ more interesting content,¹⁸ parent education¹⁹ and reward systems.¹ The duration of wearing an eye patch or drops for amblyopia therapy can be monitored with a calendar,²⁰ a temperature-under-patch device,²¹ supervision,²² and eye tracking behavior.³ Clinicians should adapt some of these techniques especially for patients with compliance challenges. The Curesight therapy offers several of these (Central monitoring center calendar and education, interesting content, supervision and eye-tracking) and improves stereo in addition to visual acuity in contrast to the consistent, month-long occlusion of the intra-operative sew-on shield.

Supervision may be the key to superior vision recovery in amblyopia therapy.²² The eye-tracking component of CureSight not only directs the region of sound-eye blur real-time in dichoptic content delivery, but can also monitor level of alertness with fixation losses and blinking, and also whether the spectacles are over the correct eye. Spectacles remain a critical component of amblyopia therapy.^{23, 24}

Spectacle-flip is a rare but feared complication. Our patient loved watching videos, and discovered ways to improve her view. Though not by her deliberate intent, the spectacle-flip effectively sabotaged her conventional atropine/hyperopic anisometropic spectacle therapy. In my experience as a PEDIG investigator since 2000, this patient is my first to suffer from spectacle-flip sabotage of therapeutic efficacy. CureSight for our patient achieved 3 logMAR lines de-novo improvement from her severe amblyopia with a consistent increase in stereopsis. The patient and guardian were still motivated to continue even more dichoptic therapy with child-friendly content. The maximum residual amblyopia acuity retrieval – perhaps even rivalling the sound eye – for a 7-year-old, treated amblyopic child is not yet known.

In conclusion, the orientation and location of sturdy spectacles is a critical aspect of successful amblyopia therapy and must be monitored in some reliable way. Eye tracking, as a component of some types of dichoptic therapy, is a practical real-time tool for precise monitoring of the amblyopia treatment process and duration.