Models of Accommodation Deficiency in Presbyopia Patients

Abstract

Purpose: We describe new phenomenological illumination-dependent static models of the accommodation deficiency for patients with presbyopia. Such models are suitable for vision restoration with adaptive-optics accommodating eyeglasses and contact lenses. Methods: Data from fifteen participants over the age of 45 and diagnosed with presbyopia was collected. Participants were asked to wear a pair of mechanically-tunable eyeglasses and clearly identify the optotypes corresponding to the LogMAR 0.0 line on Early Treatment of Diabetic Retinopathy Study (ETDRS) charts, by suitably adjusting the optical powers of the lenses on these tunable eyeglasses for each measurement. Seven ETDRS charts, placed at distances from the patients varying from 4 m through 30 cm, were used under three chart illumination levels (75 lx, 500 lx and 800 lx). The optical power of the lenses in the patient-adjusted tunable eyeglasses was subsequently measured using a Shack-Hartman wavefront sensor for each chart, which provided the accommodation deficiency data of the participants. Results: The measured accommodation deficiency data from 15 presbyopes was curve-fitted to a model for each patient. The calculated root-mean-square error values for the fitted models ranged between 0.09 D - 0.67 D over a 3.08 D accommodation stimulus range. Conclusions: The data shows that while accommodation deficiency in humans is a function of the stimulus, it is also strongly dependent on the object illumination and age of the patients. The models adequately describe the relation between static accommodation deficiency, accommodation stimulus and object illumination.

Correcting Presbyopia With Autofocusing Liquid-Lens Eyeglasses

“…This allowed the distance sensor to gather real time distance data of an object placed directly in its line of sight and communicate this distance to the control electronics which set the corrective optical powers on the variable-focus lens. The relationship between the object distance and the lens corrective power was determined using patient-specific empirical accommodation deficiency models [102] programmed into the control electronics. Patient data necessary to test these eyeglasses were obtained from a recent, unpublished clinical trial study undertaken by authors of this article [102], [103] We used a 633 nm light source and the Shack-Hartman wavefront sensor to measure the various optical powers generated by this system at various object distances, as shown in the schematic of Fig.…”

“…Hence, remnant accommodation plays a crucial role when a presbyope is trying to achieve clear focus. In order to restore normal vision, the variable-focus lens must reproduce the accommodation deficiency (AD) curve [102] as shown in Fig. 5, which is the difference between the expected ideal response of the accommodative system (clear focus) and the degraded accommodation response (AR) of the presbyopic eye.…”

“…Therefore, we chose to use model functions for the AD that require just a few parameters (and measurements), to describe the AD more economically. Multiple accommodation response models, which express the accommodation response of an ocular system in terms of the object distance, have been suggested so far [102], [109].…”

“…We use a newly developed model described in [102], which relates the accommodation response to the object distance using a sigmoid function:…”

“…Accommodation stimulus is the reciprocal of the object distance from the eyes, while the accommodation deficiency is the defocus error present in the human ocular system. The solid line represents a typical AD model, developed in a recent study [102].…”