Restoring accommodation to the presbyopic eye: How do we measure success?

Incidence and factors for pseudoaccommodation after monofocal lens implantation: the Monofocal Extended Range of Vision study

PURPOSE

To screen patients with a monofocal intraocular lens (IOL) for incidence of unaided 20/40 and 0.3 LogMAR for distance and near (pseudoaccommodation) and to find factors for pseudoaccommodation.

SETTINGS

University Hospitals Sussex NHS Foundation Trust, Brighton, United Kingdom.

DESIGN

Prospective study.

METHODS

This was a single-eye study ( ClinicalTrials.gov : NCT04011696). At 3 to 9 months, refraction, uncorrected and corrected distance and uncorrected near visual acuity (logMAR), spherical equivalent (SEQ), mesopic pupil size (PS), total eye spherical (Z 40 ), vertical coma (Z 3-1 ) aberrations, reading speed and smallest print size were assessed. Refractive astigmatism (RA) was classified as against-the-rule, with-the-rule, oblique and no astigmatism. Data on preoperative axial length (AL) and anterior chamber depth (ACD) were collected.

RESULTS

29 patients (9.6%, 95% CI, 6.5-13.5) had pseudoaccommodation. In cases vs controls, median SEQ, PS, total Z 40 , Z 3-1 , reading speed, smallest print size, preoperative ACD, preoperative AL were: -0.39 vs 0.0 diopters; 3.62 vs 4.10 mm; 0.01 vs 0.02 μm; 0.018 vs 0.022 μm; 106 vs 133 words per minute; 0.30 vs 0.50 logMAR; 2.94 vs 3.13 mm, 23.4 vs 23.7 mm, respectively. RA was not different between the groups. Univariate analysis revealed preoperative ACD (odds ratio [OR], 0.38, 95% CI, 0.16-0.94, P = .04), SEQ (OR, 0.61, 95% CI, 0.42-0.88, P = .01), total Z 40 (OR, 0.0003, 95% CI, 0.00-0.39, P = .03) and PS (OR, 0.39, 95% CI, 0.22-0.69, P < .041) to be significant. Whereas multivariable logistic regression identified: preoperative AL (OR, 0.62, 95% CI, 0.42-0.91, P = .02), SEQ (OR, 0.49, 95% CI, 0.31-0.78, P = .01), Z 40 (OR, 0.00, 95% CI, 0.0-0.01, P = .01) and PS (OR, 0.41, 95% CI, 0.23-0.75, P = .01) to be significant.

CONCLUSIONS

A combination of low myopic SEQ, lower Z 40 , shorter preoperative AL, and smaller PS increases the chances of pseudoaccommodation.

Rest-activity and light exposure patterns in the home setting: a methodological case study

BACKGROUND

This methodological case study describes light exposure and rest-activity patterns in an older adult with dementia and his caregiver spouse.

METHODS

Two devices were used to measure rest-activity and light exposure data: a wrist-worn actigraph with a light sensor to record full spectrum light exposure data and an eye-level wavelength-sensitive light meter (Daysimeter). The wife wore both devices simultaneously; the husband wore only the actigraph.

RESULTS

There were minimal feasibility issues in using the devices in the home setting. The wife's light exposure was considerably better than her husband's, but she spent little time in bright lighting. Her circadian stimulus (CS) and rest-activity values suggest a high level of circadian disruption.

CONCLUSION

This case study provides beginning support for the use of the Daysimeter in the home setting while also highlighting unrecognized circadian disturbances and very low light levels in an older couple's home.

[Techniques for measuring phakic and pseudophakic accommodation. Methodology for distinguishing between neurological and mechanical accommodative insufficiency]

The methods available for studying accommodation are evaluated: Donder's "push-up" method, dynamic retinoscopy, infrared optometry using the Scheiner principle, and wavefront analysis are each discussed with their inherent advantages and limitations. Based on the methodology described, one can also distinguish between causes of accommodative insufficiency. Dioptric insufficiency (accommodative lag) that remains equal at various testing distances from the subject indicates a sensory/neurologic (afferent), defect, whereas accommodative insufficiency changing with distance indicates a mechanical/restrictive (efferent) defect, such as in presbyopia. Determining accommodative insufficiency and the cause can be particularly useful when examining patients with a variety of diseases associated with reduced accommodative ability (e.g., Down syndrome and cerebral palsy) as well as in evaluating the effectiveness of various potentially accommodating intraocular lens designs.

Phacoemulsification and Implantation of an Accommodating IOL After PRK

PURPOSE

To present a case of phacoemulsification and implantation of an accommodating intraocular lens (IOL) in a patient with cataract formation after previous refractive surgery.

METHODS

A 50-year-old man, who initially had photorefractive keratectomy to correct moderate myopia, developed a cataract in one eye. He subsequently underwent phacoemulsification and implantation of a 1CU accommodating IOL, as he wished to remain spectacle independent.

RESULTS

The patient's distance vision was fully restored. However, accommodative function, which was assessed using subjective and novice objective techniques, was only partially restored.

CONCLUSIONS

Although the accommodating IOL fully restored the patient's distance vision, accommodative function was only partially restored.

Accommodation as a function of age and the linearity of the response dynamics

The changes with age in the accommodation responses to dynamic stimuli can reveal useful information on the factors underlying presbyopia development. Analysis of the monocular accommodation responses of 19 normal observers (ages 18-49 years) to stimuli whose vergence varied sinusoidally with time at different temporal frequencies (peak-to-peak stimulus 1.33-2.38 D, at 0.05-1.00 Hz) showed that at all ages both the gain and phase of the response were essentially linear functions of the temporal frequency. Extrapolation of least-squares, regression line fits to the gain data for each subject gave the gain at zero frequency, G0, and the cut-off frequency, fc, at which the gain fell to zero. G0 reduced with age but fc remained essentially constant at about 1.7 Hz, up to at least the age of about 40. The magnitude of the response to step stimuli covering the same stimulus range was well correlated with the value of G0. The linear changes in phase lag with temporal frequency corresponded to simple time delays td. The time lag varied from close to zero for the youngest subjects to about 0.5 s for the subjects in their late forties. There was substantial variation between the responses of subjects of similar age: those subjects with high values of G0 also tended to have low values of td, both effects probably being due to the superior ability of some individuals to predict the sinusoidal changes in the accommodation stimulus. Comparison of theoretical step responses, derived by applying linear theory to the parameters obtained from the results for the sinusoidal stimuli, with the actual responses to unpredictable steps for the same subjects supports the view that prediction effects and other possible factors make linear theory inapplicable to this type of data. The results are discussed in the context of current ideas on the development of presbyopia: it is suggested that the constancy of fc with age is the result of the ciliary body maintaining its efficiency, whereas the fall in G0 and increase in td result from increases in lens rigidity.