Suitability of multifunction devices Myah and Myopia Master for monitoring myopia progression in children and adults.

PURPOSE: To assess the feasibility of using multifunction instruments to measure axial length for monitoring myopia progression in children and adults. METHODS: Axial length was measured in 60 children (aged 6-18 years) and 60 adults (aged 19-50 years) with multifunction instruments (Myah and Myopia Master) and stand-alone biometers (Lenstar LS900 and IOLMaster 700). Repeatability (measurements by the same examiner) and reproducibility (measurements by different examiners) were computed as the within-subject standard deviation (Sw) and 95% limits of agreement (LoA). Inter-instrument agreement was computed as intraclass correlation coefficients. The threshold for detecting myopic progression was taken as 0.1 mm. Measures were repeated only in children following the administration of 1% tropicamide to determine the impact of cycloplegia on axial length. RESULTS: Overall, the IOLMaster 700 had the best repeatability in children (0.014 mm) and adults (0.009 mm). Repeatability Sw values for all devices ranged from 0.005 to 0.021 mm (children) and 0.003 to 0.016 mm (adults). In children, reproducibility fell within 0.1 mm 95% of the time for the Myah, Myopia Master and IOLMaster 700. Agreement among all devices was classified as excellent (ICC 0.999; 95% CI 0.998-0.999), but the 95% LoA among the Myah, Myopia Master and Lenstar LS900 was ≥0.1 mm. Cycloplegia had no statistically significant effect on axial length (all p > 0.13). CONCLUSIONS: The Myah and Myopia Master multifunction instruments demonstrated good repeatability and reproducibility, and their accuracy was comparable to stand-alone biometers. Axial length measurements using different instruments can be considered interchangeable but should be compared with some caution. Accurate axial length measurements can be obtained without cycloplegia. The multifunction instruments Myah and Myopia Master are as well suited for monitoring myopia progression in children as the stand-alone biometers IOLMaster 700 and Lenstar LS900.

Stimulus characteristics of a novel air-based multiple stimulus aesthesiometer.

PURPOSE: To identify the stimulus airflow characteristics and confirm the consistency of a novel air jet-based aesthesiometer capable of producing and applying multiple stimuli separated either by time and/or by space. METHODS: A novel aesthesiometer (Dolphin Aesthesiometer) was designed around a micro-blower under software management. Two nozzle attachments assisted in airflow control (flexible tube 1.6 mm diameter; brass tube 0.5 mm diameter). Four studies that tested the characteristics of the airflow and stimulus consistency were completed: (i) airflow pattern/trajectory, (ii) airflow surface dispersion, (iii) force of airflow across a range of stimulus strengths and (iv) thermal effects on the ocular surface. RESULTS: Stimulus characteristic studies revealed: (i) airflow is coherent within the expected test distance range for the instrument, and spread rate is constant irrespective of stimulus strength; (ii) airflow dispersion occurs upon encountering a surface and dispersion increases with increasing airflow rate; (iii) a consistent and small force (10-4 N) is applied by the airflow and (iv) repeatable thermal effects occur in relation to the airflow, and the mode of stimulation of the Dolphin aesthesiometer is predominantly thermal in nature. CONCLUSIONS: These studies confirm the repeatability and consistency of the novel instrument. The device is suitable for measuring corneal sensitivity. The availability of additional air jets allows the application of multiple stimuli to facilitate corneal summation investigations.