The effect of asymmetrical accommodation on anisometropic amblyopia treatment outcomes

Comparative Analysis of Physiological Vergence Angle Calculations from Objective Measurements of Gaze Position

Eccentric photorefractometry is widely used to measure eye refraction, accommodation, gaze position, and pupil size. While the individual calibration of refraction and accommodation data has been extensively studied, gaze measurements have received less attention. PowerRef 3 does not incorporate individual calibration for gaze measurements, resulting in a divergent offset between the measured and expected gaze positions. To address this, we proposed two methods to calculate the physiological vergence angle based on the visual vergence data obtained from PowerRef 3. Twenty-three participants aged 25 ± 4 years viewed Maltese cross stimuli at distances of 25, 30, 50, 70, and 600 cm. The expected vergence angles were calculated considering the individual interpupillary distance at far. Our results demonstrate that the PowerRef 3 gaze data deviated from the expected vergence angles by 9.64 ± 2.73° at 25 cm and 9.25 ± 3.52° at 6 m. The kappa angle calibration method reduced the discrepancy to 3.93 ± 1.19° at 25 cm and 3.70 ± 0.36° at 600 cm, whereas the linear regression method further improved the accuracy to 3.30 ± 0.86° at 25 cm and 0.26 ± 0.01° at 600 cm. Both methods improved the gaze results, with the linear regression calibration method showing greater overall accuracy.

Bifocal use in hyperopic anisometropic amblyopia treated with atropine: a proof-of-concept randomized trial

OBJECTIVES

To investigate the effect of bifocal wearing in the amblyopic eye when atropine is used in the sound eye for the treatment of hyperopic anisometropic amblyopia.

METHODS

Children 4-8 years old were randomly assigned to bifocal + atropine (n = 16) or only atropine (control, n = 19) groups of treatment in a proof-of-concept study. Measurements included visual acuity (logMAR), prism and cover test, stereoacuity (Randot preschool or Randot circles), contrast sensitivity (MARS test), accommodation (Grand Seiko WAM5500 and dynamic retinoscopy), retinoscopic and subjective refraction, before starting treatment and at 6 months, except accommodation, which was remeasured at 9-11 months. Main outcome measure was change in logMAR lines of visual acuity, and secondary outcome measures were change in stereoacuity and contrast sensitivity in the amblyopic eye, at 6 months.

RESULTS

Improvement in visual acuity of the amblyopic eye was significantly better (p = 0.04) in the atropine plus bifocal (3.3 ± 0.9 logMAR lines) than in the atropine only group (2.6 ± 0.8 logMAR lines), whereas change in stereoacuity and contrast sensitivity was not significantly different between the two groups. Differences in accommodative gain, which was impaired in the amblyopic compared to the sound eye, before treatment, decreased after treatment, in the atropine group (0.62 ± 0.16 vs 0.79 ± 0.2, p = 0.3), and atropine + bifocal group (0.69 ± 0.15 vs 0.82 ± 0.2, p = 0.4).

CONCLUSIONS

Use of bifocal lens add in the amblyopic eye of children with hyperopic anisometropic amblyopia, treated by atropine penalization, is beneficial in the follow-up period of 6 months.

Do monocular myopia children need to wear glasses? Effects of monocular myopia on visual function and binocular balance

Objective

This study aims to compare the binocular visual functions and balance among monocular myopic adolescents and adults and binocular low myopic adolescents and explore whether monocular myopia requires glasses.

Methods

A total of 106 patients participated in this study. All patients were divided into three groups: the monocular myopia children group (Group 1 = 41 patients), the monocular myopia adult group (Group 2 = 26 patients) and the binocular low myopia children group (Group 3 = 39 patients). The refractive parameters, accommodation, stereopsis, and binocular balance were compared.

Results

The binocular refractive difference in Group 1, Group 2, and Group 3 was -1.37 ± 0.93, -1.94 ± 0.91, and -0.32 ± 0.27 D, respectively. Moreover, uncorrected visual acuity (UCVA), spherical equivalent (SE) and monocular accommodative amplitude (AA) between myopic and emmetropic eyes in Group 1 and Group 2 were significantly different (all P < 0.05). There was a significant difference in the accommodative facility (AF) between myopic and emmetropic eyes in Group 2 (t = 2.131, P = 0.043). Furthermore, significant differences were found in monocular AA (t = 6.879, P < 0.001), binocular AA (t = 5.043, P < 0.001) and binocular AF (t = -3.074, P = 0.003) between Group 1 and Group 2. The normal ratio of stereopsis according to the random dots test in Group 1 was higher than in Group 2 (χ2 = 14.596, P < 0.001). The normal ratio of dynamic stereopsis in Group 1 was lower than in Group 3 (χ2 = 13.281, P < 0.001). The normal signal-to-noise ratio of the binocular balance point in Group 1 was lower than Group 3 (χ2 = 4.755, P = 0.029).

Conclusion

First, monocular myopia could lead to accommodative dysfunction and unbalanced input of binocular visual signals, resulting in myopia progression. Second, monocular myopia may also be accompanied by stereopsis dysfunction, and long-term uncorrected monocular myopia may worsen stereopsis acuity in adulthood. In addition, patients with monocular myopia could exhibit stereopsis dysfunction at an early stage. Therefore, children with monocular myopia must wear glasses to restore binocular balance and visual functions, thereby delaying myopia progression.

Accommodative Exercises to Lower Intraocular Pressure

Purpose

This study investigated how a conscious change in ocular accommodation affects intraocular pressure (IOP) and ocular biometrics in healthy adult volunteers of different ages.

Methods

Thirty-five healthy volunteers without ocular disease or past ocular surgery, and with refractive error between −3.50 and +2.50 diopters, were stratified into 20, 40, and 60 year old (y.o.) age groups. Baseline measurements of central cornea thickness, anterior chamber depth, anterior chamber angle, cornea diameter, pupil size, and ciliary muscle thickness were made by autorefraction and optical coherence tomography (OCT), while IOP was measured by pneumotonometry. Each subject's right eye focused on a target 40 cm away. Three different tests were performed in random order: (1) 10 minutes of nonaccommodation (gazing at the target through lenses that allowed clear vision without accommodating), (2) 10 minutes of accommodation (addition of a minus 3 diopter lens), and (3) 10 minutes of alternating between accommodation and nonaccommodation (1-minute intervals). IOP was measured immediately after each test. A 20-minute rest period was provided between tests. Data from 31 subjects were included in the study. ANOVA and paired t-tests were used for statistical analyses.

Results

Following alternating accommodation, IOP decreased by 0.7 mmHg in the right eye when all age groups were combined (p = 0.029). Accommodation or nonaccommodation alone did not decrease IOP. Compared to the 20 y.o. group, the 60 y.o. group had a thicker ciliary muscle within 75 μm of the scleral spur, a thinner ciliary muscle at 125–300 μm from the scleral spur, narrower anterior chamber angles, shallower anterior chambers, and smaller pupils during accommodation and nonaccommodation (p's < 0.01).

Conclusion

Alternating accommodation, but not constant accommodation, significantly decreased IOP. This effect was not lost with aging despite physical changes to the aging eye. A greater accommodative workload and/or longer test period may improve the effect.

Characterization, passive and active treatment in strabismic amblyopia: a narrative review

Strabismic amblyopia is characterized by a distorted spatial perception. In this condition, the neurofunctional disorder occurring during first years of life provoke several monocular and binocular anomalies such as crowding, deficits in the accommodative response, contrast sensitivity, and ocular motility abilities. The inhibition of the binocular function of the brain by the misaligned amblyopic eye induces a binocular imbalance leading to interocular suppression and the reduction or lack of stereoacuity. Passive treatments such as occlusion, optical and/or pharmacological penalization, and Bangerter foils has been demonstrated to be potentially useful treatments for strabismic amblyopia. Recent researches have proved new pharmacological options to improve and maintain visual acuity after occlusion treatment in strabismic amblyopia. Likewise, the active vision therapy, in the last years, is becoming a very relevant therapeutic option in combination with passive treatments, especially during and after monocular therapy, in the attempt of recovering the imbalanced binocular vision.