Nabovati 2020.

Study characteristics
Methods	Study design: RCT Number randomized: 64 (32 assigned to prism reading glasses; 32 assigned to placebo reading glasses) Unit of randomization: individual participant (convergence insufficiency is a binocular vision disorder) Number analyzed: 61 (three participants lost to follow up) Number of centers: 1 Date of first enrolment: November 2018 Length of follow‐up: 12 weeks Sample size estimation: not reported
Participants	Country of recruitment: Iran Mean age: 25.5 ± 5.5 (SD) years (no data presented by treatment group) Sex: 44% were male (no data presented by treatment group) Key inclusion criteria: 18 to40 years old; convergence insufficiency diagnosed as 1) exophoria at near of at least 4 prism diopters greater than at far, 2) receded near point of convergence (NPC) break (≥ 6 cm), 3) insufficient positive fusional vergence (PFV) at near, i.e. failing Sheard's criterion (near PFV less than twice the near exophoria); 4) A normal monocular accommodative amplitude according to Hofstetter's formula: measured monocular amplitude is above the minimum accommodative age‐expected amplitude according to formula: 15 ‐ 0.25 x (age); moderate to severe stages of CI based on the amount of PFV measured at baseline; not a candidate for vision therapy due to financial issues, time limitation, or lack of motivation. Key exclusion criteria: best corrected visual acuity worse than 20/25 in either eye; constant strabismus; latent or manifest nystagmus; previous treatment of CI in the past year; history of strabismus or refractive surgery; history of any intraocular surgery; use of ophthalmic or systemic drugs affecting binocular vision or accommodation; and history of ocular trauma
Interventions	Intervention regimen #1: prismatic spectacles Non‐emmetropic participants were instructed to wear the prescribed prism lenses only for near‐work activities lasting more than 15 minutes. If a participant was ametropic and required distance optical correction, two pairs of glasses for near and far were prescribed and the prescribed prism was only applied in the near spectacles. The participant was instructed to use the distance glasses routinely and wear the near spectacles for near‐work activities like reading. Intervention regimen #2: placebo spectacles Non‐emmetropic participants were instructed to wear the prescribed plano lenses only for near‐work activities lasting more than 15 minutes. If a participant was ametropic and required distance optical correction, two similar pairs of glasses were prescribed. One pair was introduced as near glasses and the participant was asked to use them for near‐work activities.
Outcomes	Primary outcome: Convergence Insufficiency Symptom Survey score Secondary outcomes: near exophoria, near PFV, NPC, vergence facility, monocular accommodative facility, accommodative response, negative relative accommodation, and accommodative convergence/accommodation (AC/A) ratio
Notes	Funding sources: not reported Subgroup analyses: none reported Trial registration: not available
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"The permuted block design approach was applied for the randomisation process using Microsoft Excel software".
Allocation concealment (selection bias)	Unclear risk	"Each participant was first randomly assigned to either treatment (prism) or control (placebo) groups by a coordinator outside the optometry examination room."
Blinding (performance bias and detection bias) Primary outcome	High risk	"The patients were masked to the group to which they were assigned." "Since it was possible to identify the type of the assigned correction by the experienced examiner, the examiner was not masked to the participant's group assignment at the outcome examination."
Blinding (performance bias and detection bias) Secondary outcomes	High risk	"Since it was possible to identify the type of the assigned correction by the experienced examiner, the examiner was not masked to the participant's group assignment at the outcome examination."
Incomplete outcome data (attrition bias) Primary outcome	Low risk	One participant (out of 32) and two participants (out of 32) were lost to follow up in the prism group and placebo group, respectively.
Incomplete outcome data (attrition bias) Secondary outcomes	Low risk	See above.
Selective reporting (reporting bias)	Unclear risk	Although there was a trial registration number with the Iranian Registry of Clinical Trials, we could not retrieve the registration information. All outcomes described in the Methods were reported.