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.
Highlights
Presbyopia is often overlooked as a health condition since corrective modalities such as presbyopic spectacle lens corrections, contact lenses, or intraocular lenses are readily available and provide adequate vision over a range of distances
Adaptation to progressive additive lens (PALs) will be defined in this study as the subject’s self-report of whether s/he will continue to wear PALs daily. This knowledge may provide insight regarding the successful adaptation to PALs, allowing clinicians to better prescribe treatments suited to the individual to reduce visual symptoms associated with presbyopia
The ones who adapted to PALs were called incipient presbyopic adapting subjects (IPAS) and those who tried but could not adapt to PALS were called incipient presbyopic non-adapting subjects (IPNAS)
Summary
Presbyopia is often overlooked as a health condition since corrective modalities such as presbyopic spectacle lens corrections, contact lenses, or intraocular lenses are readily available and provide adequate vision over a range of distances. Some presbyopes have difficulty when wearing PALs and may experience moderate to severe visual symptoms such as blurred vision, headaches, perceived movement of the peripheral visual field or “swim”, balance issues, and nausea[18] These individuals discard PALs and use other corrective modalities such as reading glasses. Previous studies have suggested that phoria adaptation, or the ability to sustain consistent eye alignment in the presence of a binocular stimulus, may be a primary factor in maintaining stable and comfortable binocular vision[28,29,30] These studies have shown a clear relationship between disparity convergence and phoria, where the change in the magnitude of phoria reduces the load on the disparity convergence system. Using the knowledge acquired from the proposed experiments described below, this study seeks to determine which parameter(s) from the vergence and phoria systems best correlated with PALs acceptability
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