The effect of low dose atropine eye drops on coordinated aiming and focusing in young adult eyes

INTERVENTION: 0.05% atropine sulfate (0.1% BAK) eye drops, 1 drop in each eye at night before bed, for 9 nights To monitor adherence to the intervention, eye drop bottles will be weighed before dispensing, and after conclusion of the clinical trial. Participants will also receive nightly text message reminders at 9pm to encourage compliance. CONDITION: Eye ‐ Diseases / disorders of the eye Progressing myopia; ; Progressing myopia PRIMARY OUTCOME: Change in near fusional reserves (positive and negative), as measured with participant wearing their habitual correction and fixating on a 6/9 equivalent near target in primary gaze, 40cm from the participants eyes. A 50 prism dioptre prism bar will be placed with 1 prism dioptre in front of the participant's right eye with the prism base‐in (negative fusional reserves) to be tested first. Participants will be instructed to report when the letters "become blurred or doubled" but to try to keep the target single as long as possible as the magnitude of base‐in prism is increased. The participant's blur, break, and recovery values for negative fusional reserves will be recorded, before the procedure is then repeated again using base‐out prism to test positive fusional reserves.[2 days and 10 days post‐commencement of intervention] Change in near heterophoria, as measured with participant wearing their habitual correction with a Howell‐Dwyer near card at 33cm, dissociated with 6 base‐down prism in front of the right eye.[2 days and 10 days post‐commencement of intervention] Change in near point of convergence, as measured with the participant wearing their habitual correction, and with a 6/9 equivalent near target held in front of the participant's eyes in primary gaze at a distance of initially 40cm. The target will then be moved slowly towards the participant, and the participant will be instructed to report when the letters on the target "double". The distance at which the participant first reports sustained doubling is reported in cm as the near point of convergence.[2 days and 10 days post‐commencement of intervention] SECONDARY OUTCOME: Change in accommodative amplitude, as measured monocularly and binocularly with the push up method. Accommodative amplitude will be measured monocularly in each of the participant's eyes (right, and then left) while wearing their habitual spectacle correction and fixating on a near target of 6/9 equivalent. The fellow eye will be occluded for the monocular measurements, and the target will be held 40 cm in front of the participant’s eyes in primary gaze. The participant will be instructed to “keep the target clear and single for as long as possible” and report when letters “first start to blur”. The target will slowly be moved towards the participant at a rate of 1‐2 cm per second, until the participant first reports blur. The participant will then be asked if the letters remain blurred, or whether they become clear. If they are cleared, the target is moved closer until the first sustained blur. This distance from target to participant is measured in centimetres (to the nearest half centimetre). If the participant is wearing spectacles, the distance will be measured to the spectacle plane. If the participant is wearing contact lenses, the distance will be measured to the corneal plane. The amplitude of accommodation is then recorded as the inverse of this distance. The procedure will then be repeated for the left eye (with the right eye occluded), and then with both eyes together (no occlusion).[2 days and 10 days post‐commencement of intervention] Change in accommodative posture, which will be measured monocularly on both eyes of each participant using the Grand Seiko WAM‐5500 open‐field autorefractor. Participants will be required to wear their habitual distance correction with their fellow eye patched, while the eye to be measured fixates through the instrument’s open‐field beam splitter on a distance target (6/9 letter on ETDRS chart viewed at a distance of 6 m) followed by a near target (6/9 equivalent letter target suspended from a near‐point rod which will be mounted on the instrument. The distance will be measured once in each eye, and then 3 consecutive measurements will be taken at near for each eye, and averaged.[2 days and 10 days post‐commencement of intervention] Change in binocular accommodative facility (+/‐ 2 D), as measured with participants wearing their habitual spectacle correction and fixating on a near letter target of 6/9 equivalent at a distance of 40cm. Using a +/‐ 2D binocular lens flipper, the plus lenses will first be placed in front of the participant's eyes and the participant will be instructed to say "clear" as soon as the target letters appear clear. The binocular lens flipper will then quickly be flipped to the ‐2.00 D lenses and the participant will once again be instructed to say "clear" when the target appears clear. This will constitute one "cycle". The cycles will continue for 1 minute. The accommodative facility will be recorded as the number of cycles per minute that the participant was able to perform.[2 days and 10 days post‐commencement of intervention] Change in relative accommodation (positive/negative), measured with the participant behind the phoropter with their habitual spectacle correction in place, with eyepieces converged and participant's fixation of a target of 6/9 equivalent vertical letters at 40cm. Positive lenses will be added first in +0.25 D steps until the participant reports sustained blur of the letters (negative relative accommodation). Negative lenses will then be added in ‐0.25 D steps until the participant reports sustained blur (positive relative accommodation).[2 days and 10 days post‐commencement of intervention] Change in score on the 5‐item Dry Eye Questionnaire, as measured by the participant's subjective symptoms of dry eye, assessed using the 5‐item Dry Eye Questionnaire (e.g. eye discomfort frequency and intensity, eye dryness frequency and intensity, watery eyes frequency). The DEQ‐5 gives a composite score reflective of the different ways dry eye symptoms can manifest. The DEQ‐5 was not intended to be used as multiple separate outcomes of eye discomfort.[2 days and 10 days post‐commencement of intervention] Change in score on the Convergence Insufficiency Symptom Survey, as measured by any subjective participant symptoms which may be attributed to convergence insufficiency, as specified in the Convergence Insufficiency Symptom Survey (e.g. tiredness, headaches, discomfort, sleepiness in eyes associated with near work; double vision, loss of concentration, losing place when reading).[2 days and 10 days post‐commencement of intervention] INCLUSION CRITERIA: Healthy, young adult myopes with a myopic refractive error between ‐0.75 and ‐6.00 DS, with no more than 1.50 DC of astigmatism or 2 D of anisometropia, whose refractive error is currently corrected with single vision distance spectacles or contact lenses, and who have stereoacuity of 200 seconds of arc or greater.