This study was performed according to the tenets of the Declaration of Helsinki and was approved by the local ethics committee. The measurements were carried out after informed voluntary consents of the parents or legal representative of the child for it had been received.
When selecting a group of children for TPST, as well as corneal pneumotonometry, we were guided by the following criteria. Children with pathological conditions of the upper eyelid (inflammatory diseases, scars, eyelid deformity), with pronounced scleral pathology in the projection of the measurement area, with erosion, ulcers, corneal edema, those who underwent keratoplasty or had penetrating eye trauma, as well as the children with high anisometropia (more than 2 diopters) have been excluded from the examination.
Taking into account the above criteria, 42 children (84 eyes), including 23 boys and 19 girls, aged 5 to 14 years, with average age M ± SD (± m) 9.3 ± 2.7 (± 0.4) years old, have been selected for the examination, including:
18 eyes (9 children) aged 5 to 11 (average age 6.6 ± 1.9 (± 0.7)) with hyperopic cycloplegic refraction + 0.75 to + 3.75 diopters (on average for the sphere equivalent + 1.5 ± 0.9 (± 0.2) diopters).
64 eyes (33 children) aged 5 to 14 (average age 9.6 ± 1.9 (± 0.5) years) with myopic cycloplegic refraction of − 0.5 to − 6.75 diopters (on average for the sphere equivalent − 3.1 ± 0.9 (± 0.2) diopters).
2 eyes (2 children aged 5 and 8) with emmetropic cycloplegic refraction.
In addition, 6 children aged 4 to 9 (average age 7.0 ± 1.8 (± 0.7) years) with cycloplegic refraction of + 1.25 to − 3.0 diopters were examined, who were not included in the comparative statistical analysis, since it was not possible to determine their IOP by pneumotonometry (as they refused the measurement procedure).
For transpalpebral tonometry, we used an EASYTON tonometer (JSC Yelatma Instrument Making Enterprise, Russia, Registration Certificate for a medical device No. RZN 2015/2997 dated November 17, 2016).
Non-contact pneumotonometry (pneumotonometer Reichert 7 AutoTonometer, USA) has been used as a comparison method.
All children underwent a standard ophthalmological examination, which included determination of visual acuity, autorefractometry in conditions of cycloplegia (after instillations of Sol. Cyclopentolate 1%), and a thorough examination of the fundus.
The IOP was measured in the sitting position, on the right and left eyes, sequentially with an EASYTON transpalpebral tonometer (see Fig. 1) and a Reichert 7 AutoTonometer pneumotonometer without use of any anesthetics.
To measure the IOP using an EASYTON tonometer, the child tilted his/her head back and fixed his/her gaze on a bright object (toy) at an angle of 45–60° to the horizontal axis; the tonometer rod was located on the upper eyelid in the scleral area corresponding to the corona ciliaris in the 12 o'clock meridian.
Each measurement (with an EASYTON tonometer and a pneumotonometer on the right and left eyes) was performed three times. For further analysis, the average value of these three IOP measurements was calculated for each eye with each tonometer.
After the IOP measurement procedure with an EASYTON tonometer and a Reichert 7 AutoTonometer pneumotonometer completed, the child or his/her legal representative was asked to fill out a short questionnaire, which allowed us to evaluate the measurement procedure according to the following criteria:
Sense of discomfort during the procedure
Pain during the procedure
Fear/anxiety during the procedure
The child's resistance during the procedure (this item was filled in by the doctor who performed the measurement).
The assessment was carried out on a five-point scale, where 1 point corresponded to the maximum intensity of sensation, and 5 points—to its absence.
Statistical processing of the obtained data included determination of the mean value, the standard deviation (M ± SD) and standard square error (m), as well as the Student's T-criterion. The parameter values were considered different if p < 0.05.