Accommodation in phakic and pseudophakic eyes measured with subjective and objective methods

New insights in presbyopia: impact of correction strategies

Presbyopia occurs when the physiologically normal age-related reduction in the eyes focusing range reaches a point, when optimally corrected for distance vision, that the clarity of vision at near is insufficient to satisfy an individual’s requirements. Hence, it is more about the impact it has on an individual’s visual ability to function in their environment to maintain their lifestyle than a measured loss of focusing ability. Presbyopia has a significant impact on an individual’s quality of life and emotional state. While a range of amelioration strategies exist, they are often difficult to access in the developing world and prescribing is generally not optimal even in developed countries. This review identified the need for a standardised definition of presbyopia to be adopted. An appropriate battery of tests should be applied in evaluating presbyopic management options and the results of clinical trials should be published (even if unsuccessful) to accelerate the provision of better outcomes for presbyopes.

Comparison of objective accommodation in phakic and pseudophakic eyes between age groups

PURPOSE

To compare objective accommodation of phakic and pseudophakic eyes between two different age groups.

METHODS

Eighty-three eyes (83 participants aged ≥ 40 years) with a visual acuity of 20/25 or better, and refractive error < spherical - 1.0 diopters (D) and cylindrical 1.0 D, were included. Forty-four patients had undergone phacoemulsification and monofocal intraocular lens implantation and were examined 6 months post-surgery. Participants were divided into groups 1 (pseudophakic, age < 60 years), 2 (pseudophakic, ≥ 60 years), 3 (phakic, < 60 years), and 4 (phakic, ≥ 60 years). Objective accommodation and pupil diameter to 2.0- and 3.0-D stimuli were measured with a binocular open-field autorefractor.

RESULTS

The mean objective accommodation was 0.29 ± 0.47 D, 0.01 ± 0.21 D, 1.00 ± 0.88 D, and 0.01 ± 0.13 to a 2.0-D stimulus, and 0.26 ± 0.51 D, - 0.06 ± 0.21 D, 1.42 ± 1.21 D, and - 0.06 ± 0.21 to a 3.0-D stimulus in groups 1, 2, 3, and 4, respectively. For both stimuli, the values in group 1 exceeded those in groups 2 and 4, and were smaller than those in group 3, while the values in group 3 exceeded those in groups 2 and 4. The mean pupillary diameter was - 0.5 ± 0.8 mm, - 0.3 ± 0.8 mm, - 0.6 ± 0.5 mm, and - 0.6 ± 0.9 mm to a 2.0-D stimulus, and - 0.6 ± 0.8 mm, - 0.6 ± 0.8 mm, - 0.9 ± 0.5 mm, and - 1.0 ± 1.1 mm to a 3.0-D stimulus in groups 1, 2, 3, and 4, respectively. There was significant correlation between objective accommodation and changes of pupil size for both stimuli.

CONCLUSION

Age seems to play a role in objective accommodation among relatively young pseudophakic patients.

Clinical application of accommodating intraocular lens

The present review describes recent advances in application of accommodating intraocular lenses (AIOLs). Standard monofocal intraocular lenses (MIOLs) only correct distance vision, while AIOLs are designed to allow both good distance vision and near vision, which is achieved through the contraction and relaxation of ciliary muscles by providing transformation of the axial movement or curvature of the lens. Thus, AIOLs may be a better choice for those patients who demand a higher level of visual performance. Since techniques to analyze the performance of AIOLs have not been standardized, and there is a variety of both subjective and objective methods, it is hard to measure the performance of these intraocular lenses. By evaluating advantages and disadvantages of various AIOLs, and introducing techniques for measurement the performance postoperative, this paper can provide some relative information on choosing the type of AIOLs in the clinic.

Developments in the correction of presbyopia II: surgical approaches

PURPOSE

To discuss the various static and dynamic surgical approaches which attempt to give presbyopes good vision at far, intermediate and near viewing distances.

CONTENT

Static methods broadly adopt the same optical techniques as those used in presbyopic contact lens correction and aim to satisfy the needs of the presbyope by increasing binocular depth-of-focus, often using monovision as well as simultaneous-imagery. Dynamic methods generally attempt to make use of at least some of the still-active elements of the accommodation system. They include procedures which are supposed to modify the relative geometry of the ciliary muscle and lens, or which reduce the stiffness of the presbyopic lens either by replacing it with other natural or man-made material or by subjecting it to femtosecond laser treatment. Alternatively the natural lens may be replaced by some form of intraocular lens which changes power as a result of forces derived from the still-active ciliary muscle, zonule and capsule, or other sources.

CONCLUSIONS

At present, multifocal intraocular lenses appear to offer the most consistent and reliable surgical approach to surgical presbyopic correction. They have obvious advantages in convenience and stability over optically-similar, simultaneous-image presbyopic contact lenses but this must be balanced against their relative inflexibility in cases of patient dissatisfaction. Dynamic methods remain largely experimental. Although some approaches show promise, as yet no method has demonstrated a reliable, long-term ability to correct distance refractive error and to appropriately change ocular power in response to changes in viewing distance over the normal range of interest.