Preliminary evaluation of smartphone-based addition measurement in a presbyopic population

Abstract

Purpose: To evaluate the viability and accuracy of a mobile application (app) for subjective measurement of presbyopic addition, comparing its performance with standard clinical methods.

Methods: Twenty presbyopic subjects (aged 52 to 64) participated in the study. Clinical measurements of sphero-cylindrical refraction and its correction was achieved using trial lenses. Addition was also clinically measured using a standard and a tentative method. A set of 12 trial lenses ranging from 0 to 2.75 D were randomly put on top of the far distance correction, generating the correction addition correction or different levels of under/over correction of the addition. Participants then used a smartphone-based app to subjectively determine binocularly their near point (NP) using a push-up method while looking at a blue stimulus that rescaled as a function of the face-device distance measured using the front camera of the device. For each induced level of under/over correction of the addition, participants completed three measurements of their near point.

Results: Linear regression analysis showed a strong correlation (R² = 0.82) between app-measured and clinical addition values. Bland-Altman analysis revealed a mean over estimation of -0.22± 0.38 D with a limit of agreement of ±0.74 D of the near correction. Cumulative error analysis indicated that 61.7 % of app measurements were within 0.25 D of clinical values, and 82.5 % within 0.50 D CONCLUSIONS: A smartphone-based subjective measurement of presbyopic addition can potentially be used to assess the addition needed to detect the under or over corrected addition in full presbyopic subjects.

Keywords: Accommodation; Addition; Near point; Presbyopia; Smartphone.

Fig. 1

Optical effect of the addition lens in an emmetropic or distance vision corrected eye. The addition lens optically “moves” the stimulus (S) placed a distant d from the eye, to place S’ beyond de patient’s NP, so it can be seen comfortably by using only the half of the patient’s amplitude of accommodation (AA).

Fig. 2

An illustration of the benefit of using blue visual stimuli to avoid impractically far face-device distances. In the top panel an emmetropic eye forms an image of a white stimulus placed far away on the retina. In the middle panel the stimulus color is just changed to blue, and the same eye forms a blurred retinal image similar as a 0.7D myopic eye. In the bottom panel the object is brought closer to the same eye, to a distance of 1.42 m (vergence of −0.70 D) allowing the eye to form a clear the image on the retina again.

Fig. 3

Stimulus used for NP measurements with the app. Image a illustrates how the subject perceives the stimulus within their clear vision range, while Image b depicts how the stimulus appears when viewed outside this sharp vision range.

Fig. 4

Over addition measured by the app for different clinically induced over addtion values. Linear regression analysis including the 3 repeated measures of AppOverAdd and a IndOverAdd. The red line represents a mean fit across all subjects (intersubject), the black line represents a 1:1 relation. Error bars represent ±1 SD within subject.

Fig. 5

Adjusted over addition measured by the app for different clinically induced over addtion values. The red line represents a mean fit across all subjects (intersubject), the black line represents a 1:1 relation, and error bars represent ±1 SD within subject.

Fig. 6

Bland-Altman plot of 3 repeated measures of AppOverAdd. Each color represents a IndPower, from left to right from 0.00 D to 2.75 D in steps of 0.25 D The solid black line represents the mean of all differences and the dashed black lines the LOAs (± 1.96SD). A positive value in the Y-axis represents a under estimation of the measured performed by the app of the addition needed for the correction of near vision.

Fig. 7

Cumulative distribution of errors between the values of over-addition measured by the app and the clinical ones.