Comparison of Objective and Subjective Changes Induced by Multiple-Pinhole Glasses and Single-Pinhole Glasses

Effects of Miosis on the Visual Acuity Space under Varying Conditions of Contrast and Ambient Luminance in Presbyopia

Background: Presbyopia is an age-related ocular condition, typically affecting individuals aged over 40 years, characterized by a gradual and irreversible decline in the eye's ability to focus on nearby objects. Correction methods for presbyopia encompass the use of corrective lenses, surgical interventions (corneal or lens based), and, more recently, the FDA-approved topical administration of 1.25% pilocarpine. While prior research has demonstrated the efficacy of daily pilocarpine eye drop application in enhancing near visual acuity by increasing the depth of focus leveraging the pinhole effect, limited knowledge exists regarding its influence on visual acuity under varying conditions of contrast and ambient luminance. Methods: This study aims to investigate the impact of these variables on visual acuity, employing the VA-CAL test, among 11 emmetropic and 11 presbyopic volunteers who reported subjective difficulties with near vision. This study includes evaluations under natural conditions with a pinhole occluder (diameter of 2 mm), and subsequent administration of 1% pilocarpine (Pilomann, Bausch + Lomb, Laval, Canada). Results: The VA-CAL results demonstrate the expected, statistically significant effects of contrast and ambient luminance on visual acuity in both emmetropic and presbyopic volunteers. Furthermore, in emmetropic individuals, the application of pilocarpine resulted in a statistically significant reduction in visual acuity. In contrast, presbyopes did not exhibit statistically significant differences in the visual acuity space under either the pinhole or pilocarpine conditions when compared to natural conditions. Conclusions: The pharmacological treatment of presbyopia with pilocarpine eye drops, intended to enhance near vision, does not adversely affect visual acuity in presbyopes. This suggests that pilocarpine may offer a viable alternative for individuals averse to wearing corrective eyewear.

Applications of the pinhole effect in clinical vision science

The pinhole effect is commonly used to discriminate uncorrected refractive error from ocular diseases. A small aperture limits the width of light beams entering the eye, thus increasing the depth of focus. The pinhole effect has also been used in spectacles, contact lenses, corneal inlays, and intraocular lenses (IOLs) to improve reading by compensating for loss of accommodative function. Pinhole spectacles improve near visual acuity, but reduce reading speed, increase interblink interval, and decrease tear break-up time. For contact lenses and IOLs, pinhole devices are usually used in the nondominant eye, which allow compensation of various refractive errors and decrease spectacle dependence. Pinhole corneal inlays are implanted during laser in situ keratomileusis or as a separate procedure. Pinhole IOLs are gaining popularity, particularly as they do not bring a risk of a local inflammatory reaction as corneal inlays do. Disadvantages of using the pinhole effect include high susceptibility to decentration, decrease in retinal luminance levels, and difficulties in performing fundus examinations or surgery in eyes with implanted devices. There are also concerns regarding perceptive issues with different retinal illuminances in the 2 eyes (the Pulfrich effect).

Correction of presbyopia: old problems with old (and new) solutions

We live in a three-dimensional world and the human eye can focus images from a wide range of distances by adjusting the power of the eye's lens (accommodation). Progressive senescent changes in the lens ultimately lead to a complete loss of this ability by about age 50, which then requires alternative strategies to generate high-quality retinal images for far and close viewing distances. This review paper highlights the biomimetic properties and underlying optical mechanisms of induced anisometropia, small apertures, dynamic lenses, and multi-optic lenses in ameliorating the visual consequences of presbyopia. Specifically, the advantages and consequences of non-liner neural summation leveraged in monovision treatments are reviewed. Additionally, the value of a small pupil is quantified, and the impact of pinhole pupil location and their effects on neural sensitivity are examined. Different strategies of generating multifocal optics are also examined, and specifically the interaction between ocular and contact or intraocular lens aberrations and their effect on resulting image quality are simulated. Interestingly, most of the novel strategies for aiding presbyopic and pseudophakic eyes (for example, monovision, multifocality, pinhole pupils) have emerged naturally via evolution in a range of species.

Clinical feasibility of pinhole glasses in presbyopia

PURPOSE:

To investigate the ocular physiologic changes and subjective symptoms of wearing multiple-pinhole glasses in subjects with presbyopia.

METHODS:

This prospective study included 32 eligible subjects with presbyopia. Objective ocular functions and a survey of ocular discomfort were performed at baseline. All participants underwent the same examinations after reading while wearing the pinhole glasses and not wearing these glasses at a 1-week interval in random order.

RESULTS:

The pinhole glasses improved uncorrected distance and near visual acuity in presbyopia. These glasses also required 15% less accommodative power over the near stimulus of 25 cm than did eyes without pinholes. Compared to reading without pinhole glasses, reading with pinhole glasses led to the following changes: increase in monocular near point of accommodation from 4.39 ± 0.78 diopter (D) to 5.19 ± 1.12 D, increase in depth of focus from 1.42 ± 0.44 D to 2.00 ± 0.33 D, and increase in amplitude of fusional convergence from 13.38 ± 6.88 prism D to 21.62 ± 10.00 prism D. In contrast, the reading speed decreased, inter-blink interval increased, tear break-up time shortened, and subjective ophthalmic symptoms worsened with pinhole glasses compared to without.

CONCLUSION:

In presbyopia, pinhole glasses improve visual acuity and accommodation-related parameters by pseudo-accommodation and the pinhole effect. However, the low legibility, increased inter-blink interval, and shortened break-up time of pinhole glasses cause an uncomfortable feeling and excessive eye fatigue. Pinhole glasses have strengths and limitations that must be considered to provide appropriate guidance in patients with presbyopia. Clinical trial registration was done at www.ClinicalTrials.gov (identifier: NCT02722291).