Adaptation to Progressive Additive Lenses: Potential Factors to Consider

Abstract

People develop presbyopia as part of the normal aging process. Most presbyopes adapt to progressive additive lens (PALs), while others do not. This investigation sought to determine whether the ability to modify disparity vergence or phoria was correlated to PALs adaptation. In experiment 1, a double-step paradigm quantified the ability to modify convergence responses in sixteen presbyopes. In experiment 2, thirty-one incipient presbyopes participated in a 5-minute sustained fixation task to evoke phoria adaptation where the magnitude and rate of phoria adaptation were measured. Then, the experiment was repeated after wearing PALs for one month. Linear regression analyses were conducted between the following parameters: near point of convergence, positive fusional vergence at near, vergence facility, net change in the magnitude of phoria adaptation, and the rate of phoria adaptation. The ability to change convergence average peak velocity was significantly greater (p < 0.03) in presbyopic PALs adapters compared to presbyopic PALs non-adapters. The rate of phoria adaptation and vergence facility were significantly greater (p < 0.03) in incipient presbyopic PALs adapters compared to incipient presbyopic PALs non-adapters. Vergence facility and the rate of phoria adaptation may have potential clinical utility in differentiating which patients may adapt to PALs and which ones will have more difficulty.

Figure 1

Experimental protocol of (A) the short-term vergence modification for Experiment 1 and (B) the phoria adaptation for Experiment 2.

Figure 2

Ensemble plots for 4° single and double convergence responses from a subject from the PNAS (left column) and PAS (right column) groups for Experiment 1.

Figure 3

Summary of the average peak velocity (°/s) with one standard deviation of (A) 4° convergence steps during baseline and modification phases (B) first and second high-velocity components during the modification phase. Individual subject data from eight subjects who did not adapt to PALs (PNAS) and eight subjects who did adapt to PALs (PAS) were averaged.

Figure 4

(A) Change in convergence peak velocity and (B) High-velocity component ratio for the eight individual subjects who did not adapt to PALs (PNAS) and the eight subjects who adapted to PALs (PAS). Group level summary plots are shown as the average with one standard deviation.

Figure 5

Normalized phoria measurements with exponential fit line before wearing PALs (black triangle, black line) and after one month of wearing PALs (white circle, gray line) during 5 minutes of 8.44° binocular fixation of a subject who did not adapt to PALs (IPNAS upper plots) and a subject who adapted to PALs (IPAS lower plots). Positive values mean an esophoric change in the subject’s phoria level and negative values means an exophoric change in the subject’s phoria level.

Figure 6

(A) Normalized average rate of phoria adaptation and exponential fit of IPNAS group before (upside down triangle, black line) and one month after wearing PALs (open circle, gray line). (B) Normalized average rate of phoria adaptation and exponential fit of IPAS group before (triangle, black line) and one month after wearing PALs (open circle, gray line). Group level average and one standard deviation of the rate of phoria adaptation (C) and the change in magnitude of phoria adaptation (D) before (black bar) and one month after wearing PALs (white bar) of IPNAS, IPAS and all subjects.

Figure 7

Correlation and statistical significance analysis between all parameters measured during the data collection. Pearson’s correlation coefficient values (r²) are displayed in each bin. The color map shown below correspond to the r² and p values. NPC: near point of convergence, RPC: recovery point of convergence, BO: base-out vergence range, BI: base-in vergence range, CISS: convergence insufficiency symptom survey score, RPA: rate of phoria adaptation, Mag: magnitude of change in phoria, Baseline: Before wearing PALs, Post One month after wearing PALs. Positive correlation is denoted in red and negative correlation is denoted in blue. Data are from Experiment 2 studying incipient presbyopes.

Figure 8

The line of no discrimination (dashed black line) and the receiver operating characteristic (ROC) curves (solid black line) with the optimal threshold (indicated as gray circle) for PALs acceptability for the following parameters: (A) baseline peak velocity (accuracy = 75%), (B) change in convergence peak velocity (accuracy = 88%), (C) high-velocity ratio (accuracy = 88%), (D) rate of phoria adaptation (accuracy = 71%), (E) change in phoria magnitude (accuracy = 71%), and (F) vergence facility (accuracy = 73%).