Real and Pseudoaccommodation in Accommodative Lenses

Abstract

In the attempt to manage presbyopia, different intraocular lens designs have been proposed such as monofocal IOLs with monovision or multifocal IOLs. Even though the lenses mentioned offer satisfactory visual results, contemporary ophthalmology has not completely answered the presbyopic dilemma by simulating the accommodative properties of the crystalline lens itself. Accommodative IOLs were designed to fill this gap and provide satisfactory vision for all distances by restoring some degree of “pseudoaccommodation.” Pseudo accommodative capability can be linked to monofocal IOL's as well but the results are not satisfactory enough to fully support unaided near vision. Pseudoaccommodation is a complex phenomenon that can be attributed to several static (i.e., pupil size, against-the-rule cylindrical refractive error, multifocality of the cornea) and dynamic (i.e., anterior movement of the implant itself) factors. Objective measurement of the accommodative capability offered by the accommodative IOLs is extremely difficult to obtain, and different methods such as autorefractometers, retinoscopy, and ultrasound imaging during accommodative effort, ray tracing, or pharmacological stimulation have been developed but the results are sometimes inconsistent. Despite the difficulties in measuring accommodation, accommodative IOLs represent the future in the attempt to successfully “cure” presbyopia.

Near vision examination in presbyopia patients: Do we need good homologated near vision charts?

“…In particular, reading speed evaluation based upon reading acuity, the critical print size, and the mean and maximum reading speeds has provided interesting insights into the near-visual performance of presbyopic patients prior to and following therapy. Clinical studies have investigated the reading performance of patients with various models of multifocal and accommodating IOLs [2–5, 9–11, 16, 17, 22], corneal inlays [7], or following laser refractive surgery [19–21]. Also, the reading performance of cataract patients has been analyzed in detail [17, 67, 23], and reading tests have been shown to be useful for estimating potential acuity [14, 68].…”

“…Since then, a number of studies have been performed with these standardized logarithmic reading charts and have shown that it is possible to obtain detailed information about the reading performance achieved with bi-, multi-focal, and accommodative IOLs [2–5, 9–11, 16, 17, 22], corneal inlays, [7], monofocal IOLs [18, 23], and following LASIK/LASEK [15] or refractive laser treatment for presbyopia [18–20]. Interesting insights into the reading performance of cataract patients have also been obtained with the Bailey-Lovie Word Reading Charts [14] and with the MNREAD Charts as e.g.…”

Optical aberrations, accommodation, and visual acuity with a bioanalogic continuous focus intraocular lens after cataract surgery

“…We also measured pseudoaccommodation which is a phenomenon attributed to gaining near vision without changes in refractive power of the ocular system. 6 …”

“…5 The changes in anterior–posterior position of the IOL resulting from contraction of ciliary muscle or vitreous pressure and its multiple focal points with alterations in lens curvature and refractive power are mainly the source of accommodative capacity of this implant. 6 , 7 …”

Achromatic doublet intraocular lens for full aberration correction

“…Different optical solutions incorporated to IOLs have been proposed to correct for this lack of accommodation. Accommodative IOLs are intended to change the eye power [10,11], although their actual implementation has not been successful yet [12][13][14]. Other IOLs incorporated multifocality, distributing the light in the image plane across separated foci [15,16].…”