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PubMed2006

Four corneal presbyopia corrections: simulations of optical consequences on retinal image quality.

PURPOSE: To investigate the possibility of multifocal or aspherical treatment of the cornea with optical ray tracing. SETTING: Institute for Refractive and Ophthalmic Surgery, Zurich, Switzerland. METHODS: The optical consequences of 4 corneal shapes-global optimum (GO) for curvature and asphericity, central steep island (CSI), decentered steep island (DSI), and centered steep annulus (CSA)-for presbyopia correction were analyzed using a modified Liou-Brennan eye model and ray tracing with a commercial optic design software (Zemax, Zemax Development Corp.). The ocular optical configuration for far vision was a point light source at a distance of 5 m, 1 degree up, and a pupil diameter of 5.0 mm and for near vision, 0.4 m distance, 1 degree up, and a pupil diameter of 2.5 mm. The curvature radius (R) of the cornea and its asphericity (Q) were used as operands to optimize (simultaneously for near and far vision) the quality of the retinal image described by means of the minimum spot diameter or the root-mean-square (RMS) wavefront error. RESULTS: Starting from an emmetropic eye optimized for R and Q, the RMS wavefront error in the retina was 0.07 microm (far) and 1.42 microm (near). The GO resulted in a wavefront error of 1.42 microm (far) and 0.52 microm (near); improvement of near vision using reading glasses is possible. The CSI yielded 0.91 microm (far) and 0.13 microm (near); spectacles did not improve far or near vision. The DSI and CSA had significantly worse results for near and far vision. CONCLUSIONS: Of the options studied, GO and CSI seemed the most promising alternatives for corneal presbyopia correction. Although reading glasses can improve near vision in GO, reading glasses did not improve near vision in CSI-treated eyes. The CSI treatment is critically dependent on centration and a reverse treatment is difficult to achieve.

Computer Simulation↗
PubMed2006

Traditional methods for the treatment of presbyopia: spectacles, contact lenses, bifocal contact lenses.

Today, many options are available for the correction of presbyopia. New technology perpetually surfaces to offer better ideas and designs to meet the visual demands of the presbyopic population. This article provides information on various modalities for spectacle and contact lens correction of presbyopia. It is based on current information at the time of publication and is not intended to be a fitting guide.

Contact Lenses↗
PubMed1999

Biometric, optical and physical changes in the isolated human crystalline lens with age in relation to presbyopia.

The biometric, optical and physical properties of 19 pairs of isolated human eye-bank lenses ranging in age from 5 to 96 years were compared. Lens focal length and spherical aberration were measured using a scanning laser apparatus, lens thickness and the lens surface curvatures were measured by digitizing the lens profiles and equivalent refractive indices were calculated for each lens using this data. The second lens from each donor was used to measure resistance to physical deformation by providing a compressive force to the lens. The lens capsule was then removed from each lens and each measurement was repeated to ascertain what role the capsule plays in determining these optical and physical characteristics. Age dependent changes in lens focal length, lens surface curvatures and lens resistance to physical deformation are described. Isolated lens focal length was found to be significantly linearly correlated with both the anterior and posterior surface curvatures. No age dependent change in equivalent refractive index of the isolated lens was found. Although decapsulating human lenses causes similar changes in focal length to that which we have shown to occur when human lenses are mechanically stretched into an unaccommodated state, the effects are due to nonsystematic changes in lens curvatures. These studies reinforce the conclusion that lens hardening must be considered as an important factor in the development of presbyopia, that age changes in the human lens are not limited to the loss of accommodation that characterizes presbyopia but that the lens optical and physical properties change substantially with age in a complex manner.

Adolescent↗
PubMed1987

Presbyopia: an animal model and experimental approaches for the study of the mechanism of accommodation and ocular ageing.

During the last hundred years, observations on normal and a few aniridic human eyes, together with population studies on the age-dependent decline in accommodative amplitude, resulted in the formulation of theories of human accommodation, and led to the concept that presbyopia is an inevitable consequence of ageing. However, such studies failed to substantiate these theories and concepts or to reveal the fundamental mechanisms of accommodation and its age-dependent loss. Detailed understanding of these mechanisms and the environmental, dietary, and behavioural factors that may influence the development of presbyopia will require controlled studies and, in some cases, invasive experimental manipulations that can only be achieved through the use of an animal model. This paper reviews some of the evidence indicating that the rhesus monkey is a highly suitable primary animal model for such studies, as well as for studies on other aspects of ocular ageing, and reviews some of the techniques and experimental approaches that have already been adapted or developed for such studies.

Accommodation, Ocular↗
PubMed2003

A longitudinal study of vergence adaptation in incipient presbyopia.

BACKGROUND: To investigate vergence adaptation during the incipient phase of presbyopia, when the amplitude of accommodation approaches the level where the first reading addition is required. The study aimed to assess the ability of the vergence system to counteract changes in the component contributions to the overall vergence response with the decline in the amplitude of accommodation in presbyopia, although previous reports on the nature of changes in accommodative, tonic and proximal vergence are equivocal. METHODS: Using a 'flashed' Maddox rod technique, an assessment of vergence adaptation to 6delta base-out and 6delta base-in prism was made for 28 subjects (aged 35-45 years at the commencement of the study). The measurements were taken four times over a 2-year period. RESULTS: Using a repeated measures analysis of variance, the results show that with the decline in amplitude of accommodation, there is a statistically significant reduction in the magnitude of vergence adaptation to both base-out (p < 0.05) and base-in prism (p < 0.01). CONCLUSIONS: This study shows that with ageing, there is a decrease in the ability of the slow vergence mechanism to overcome a change in fusional vergence demand and would suggest that either the fast component of fusional vergence must cope with any change in fusional vergence demand or that the sum of the accommodative, tonic and proximal vergence responses are virtually stable with age.

Accommodation, Ocular↗
PubMed2026

Repeated low-level red-light therapy for improving asthenopic symptoms and accommodation in presbyopia.

BACKGROUND: To assess the short-term effectiveness of repeated low-level red light (RLRL) therapy in relieving asthenopia and enhancing accommodation in presbyopia. METHODS: This randomized, parallel-group, double-masked clinical trial enrolled adults with presbyopia and self-reported asthenopia. Participants were allocated using computer-generated randomization and randomly assigned at a 1:1 ratio to RLRL or sham groups. Blinding included participants, examiners, assessors, and statisticians. The primary outcome was the change from baseline in the Computer Vision Syndrome Questionnaire (CVS-Q) score at day 31. Secondary outcomes were the change in accommodative amplitude (AA), Near Activity Visual Questionnaire (NAVQ) score, habitual near visual acuity, near-addition power, accommodative facility, positive and negative relative accommodation, binocular cross-cylinder response, and accommodative convergence-to-accommodation ratio. Continuous outcomes were analyzed using linear mixed-effects models. RESULTS: Sixty-four of 66 randomized participants (aged 41-62&#x2009;years) completed the 1-month trial. At day 31, RLRL showed greater improvement than sham in CVS-Q score (adjusted mean difference, -1.75 points; 95% CI, -3.10 to -0.39), binocular AA (1.09 D; 95% CI, 0.37 to 1.82), and NAVQ score (-8.07 points; 95% CI, -14.17 to -1.97). The effect on AA was most pronounced in a subgroup of eyes with baseline amplitude >2.0&#x2009;D (adjusted mean difference 1.33&#x2009;D; 95% CI 0.32-2.34). Other measures did not differ between groups at each visit. No treatment-related adverse events were reported. Adherence was similar between groups (mean compliance: 98.2% vs 97.5%). CONCLUSIONS: Short-term treatment with RLRL significantly reduced asthenopic symptoms and improved accommodative amplitude in individuals with presbyopia.Trial registration: NCT06745661 (registered December 8, 2024).

Humans↗
PubMed1982

Early onset of presbyopia.

Of the 800 presbyopes studied, 286 (35.75%) entered presbyopia at or before the age of 38 years. About 63% of these patients lived in rural areas and 37% in urban areas. Environmental conditions including high average temperature, much ultraviolet radiation, chronic deficiency of essential amino acids, and exposure to toxic factors, particularly hair dye, may play a significant role in precipitating the early onset of presbyopia.

Adult↗
PubMed1984

Review of ciliary muscle effort in presbyopia.

Fincham's theory of presbyopia would require maximum ciliary muscle contraction to produce maximum accommodative response at all ages. The Hess-Gullstrand theory, however, would allow a maximum accommodative response with a decreasing ciliary muscle contraction as age increases leaving a reserve ability of ciliary muscle to contract with age. If Fincham's theory is correct, a mild parasympatholytic drug would produce a decrease in the amplitude of accommodation, a mild parasympathomimetic drug would produce an increase in the amplitude of accommodation, and the AC/A ratio would increase with age. The results of this study indicate that all three of these do occur and therefore support the Fincham concept of the cause of presbyopia.

Accommodation, Ocular↗
PubMed1986

Questioning our classical understanding of accommodation and presbyopia.

The development of precise instrumentation, electron microscopy, and enhanced analytical capabilities have renewed interest in understanding the mechanisms of accommodation and presbyopia. The properties of the ciliary muscle, the zonule, the lens capsule, and the crystalline lens are being reevaluated, suggesting, for example, that these components' elasticities change significantly with age and that the biochemical properties of the crystalline lens may be altered as the lens ages. The recent findings, mainly during the past decade, are contrasted with or incorporated into our classical understanding of the accommodative mechanism and presbyopia as stated originally by Helmholtz and Fincham.

Accommodation, Ocular↗
PubMed1989

Peripheral visual acuity with monovision and other contact lens corrections for presbyopia.

We have conducted two experiments to investigate the effect of monovision and other contact lens corrections for presbyopia upon peripheral visual acuity. In the first study, we measured binocular peripheral visual acuity using Landolt rings with seven subjects wearing a monovision correction. The Landolt rings were presented at eccentricities of 10, 20, 40, and 70 degrees on each side of the subject, with near additions of +1.50 D, +2.50 D, and no addition. We found no significant effect of monovision correction on peripheral visual acuity. In the second experiment we measured the peripheral visual acuity of 11 presbyopic subjects wearing distance contact lenses with lookover spectacles, soft progressive bifocal contact lenses, soft concentric bifocal contact lenses, monovision contact lenses, modified monovision contact lenses, and hard bifocal contact lenses using Koenig bar targets. There were no significant differences in peripheral visual acuity between any of the contact lens corrections for presbyopia.

Adolescent↗
PubMed2005

Presbyopia compensation with a quartic axicon.

PURPOSE: The purpose of this study was to evaluate the performance of quartic axicons for presbyopia compensation. The working principle relies on profiting the high depth of focus of the axicons to supplement the reduced accommodation amplitude of presbyopes. METHODS: We present the design equations of a particular kind of axicon to compensate a general presbyopia condition using simultaneous vision. A rotationally symmetric polynomial of fourth-order, corresponding to the well-known Seidel spherical aberration term, was chosen as its refractive profile. To validate its performance, we computed the retinal images with Stiles-Crawford apodization for a presbyopic eye compensated with this quartic axicon and compared them with those obtained without compensation or with other available solutions based on the simultaneous vision principle. RESULTS: The quartic axicon provides an important improvement of the image quality for intermediate distance vision in comparison with conventional bifocal and trifocal solutions. The image quality, however, is still not optimum for all distances. CONCLUSIONS: The results show the usefulness of the proposed approach and point out the need for developing further adapted optimizations.

Accommodation, Ocular↗
PubMed1993

Tonic vergence, age and clinical presbyopia.

The relative contribution of tonic vergence to the maximum near vergence response as a function of age and the development of presbyopia has received little attention. Tonic vergence position was measured subjectively in a group of 50 subjects between 20 and 68 years of age. While there was no progressive trend with age, tonic vergence did exhibit a small but consistent convergent increase after 40 years of age. Thus, tonic vergence showed a slight change, possibly of a motor adaptive nature, concurrent with increasing age and the development of clinical presbyopia.

Adult↗
PubMedDate not supplied

Centered vs. inferior off-center ablation to correct hyperopia and presbyopia.

BACKGROUND: We describe a new technique of inferior off-center ablation with laser in situ keratomileusis (LASIK) to correct both hyperopia and presbyopia. METHODS: This prospective clinical study was based on the empirical results obtained with LASIK in 16 hyperopic eyes of 8 patients. All patients had a centered ablation in one eye and an inferior decentered ablation in the other eye. A Schwind excimer laser was used and a planned inferior off-center ablation of 1 mm was performed. Maximum follow-up was 22 months (8 eyes). RESULTS: Patients with hyperopia that underwent inferior decentered ablation were able to read for a prolonged period of time, compared with eyes that had conventional centered excimer laser ablation. Patients with steepened corneas in the inferior and eccentric zone ended up not only with better distance but also better near vision. No loss of spectacle-corrected visual acuity in any eye has been observed to date. CONCLUSION: Planned inferior off-center ablation to correct hyperopia and presbyopia achieved better distance and near visual acuity than centered ablation. As with centered ablation, no significant regression of effect occurred with off-center ablation; reading near vision was better and more stable with inferior off-center ablation.

Cornea↗
PubMed2006

Conductive keratoplasty for presbyopia: 1-year results.

PURPOSE: To assess the safety, efficacy, and stability of conductive keratoplasty (CK) in the treatment of presbyopia. METHODS: Ten near plano presbyopic patients (6 women and 4 men) underwent unilateral CK in the non-dominant eye to improve their near vision. Mean age was 51 +/- 3.1 years (range: 46 to 56 years). The surgeries were the author's first 10 CK procedures performed. The postoperative target for these eyes ranged from -1.25 to -1.75 diopters (D). RESULTS: Preoperative mean manifest refraction spherical equivalent (MRSE) was -0.18 +/- 0.27 D (range: -0.75 to -0.25 D), yielding a mean near uncorrected visual acuity (UCVA) of J10 (range: J12 to J5). Twelve months after CK, the mean near UCVA was J1 (range: J3 to J1) with 90% (9/10) eyes J1 and 100% (10/10) eyes J3 or better. The mean MRSE was -1.31 +/- 0.53 D (range: -2.25 to -0.75 D). Treated eyes lost an average of 2.2 +/- 2 lines (range: 0 to 5) of distance UCVA but gained an average of 8.7 +/- 2 lines (range: 4 to 11) of near UCVA. No eye lost best spectacle-corrected visual acuity or had induced cylinder > or = 0.75 D. Nine (90%) of 10 patients had binocular distance UCVA < or = 20/20 and near UCVA < or = J1 and all 10 (100%) patients had binocular distance UCVA < or = 20/25 and near UCVA < or = J3. CONCLUSIONS: Conductive keratoplasty for the treatment of presbyopia provided safe and effective results 1 year following the initial surgery. Longer follow-up will be needed to describe refractive stability. The mean near and distance UCVA results were better than expected for the amount of refractive change observed during this study.

Corneal Stroma↗
PubMed2002

[Variables related to the first presbyopia correction].

PURPOSE: We carried out a prospective study based on variables related to the age of appearance of presbyopia (AAP): refraction defect, sex, iris color, profession and pupil diameter. METHOD: Our sample population was made up of 179 persons who present consecutively for the first optical correction of presbyopia as sole reason, having a refractive defect equal to 1 diopter or less. RESULTS: In our series the AAP was not influenced by the small refraction defect, neither by sex or iris color. Different professions showed a significant AAP difference later in life (farmers, x = 51.76 D.E. 5.47 years) or earlier (services workers, x = 46.15 D.E. 3.55 years) (p<0.000003, ANOVA), than other professions such as housewife (48.42 D.E. 4.71 years) and construction workers (47.54 D.E. 3.93 years). We found significant differences in AAP among subjects with intense miosis (<2,5 mm, x = 51 D.E. 5.39 years) and without miosis (3 to 7 mm, x = 47.47 D.E. 4.71 years) (p<0.02 t Student). CONCLUSIONS: The variables which determine a significant delay in the AAP are: profession (farmer and housewife) and miosis, a 1 mm pupilar diameter reduction, in near vision, could contribute to a delay of 1.53 years in AAP.

Adult↗
PubMed2003

[Surgical correction of presbyopia].

There are a lot of surgical procedures to correct refractive errors, but the surgical correction of presbyopia is still a problem. In this paper the authors present surgical procedures, which can be used to correct presbyopia. There are three groups of surgery: the corneal, scleral and intrabulbar procedures.

Cornea↗
PubMed1992

Cause and treatment of presbyopia with a method for increasing the amplitude of accommodation.

To understand the mechanism and cause of accommodation and presbyopia, the sclera in the region of the ciliary body of presbyopic patients was expanded. The amplitude of accommodation was increased in all presbyopic patients. A unique hypothesis of accommodation based on increased zonular tension is presented, which when applied clinically, results in a treatment for presbyopia.

Accommodation, Ocular↗
PubMed1982

The development of presbyopia in primates.

Presbyopia, the age-dependent decline in accommodative amplitude, clinically afflicts every individual reaching the age of 40 to 45 years. Various pathophysiologic mechanisms have been proposed, but none is proven, and until now no animal model for their study has existed. Refraction, axial dimensions, and pharmacologically-induced accommodation were determined in caged rhesus monkeys aged 0.5 to 32 years. Accommodative amplitude decline in an age-dependent manner from greater than 40 diopters to 0 diopters. Mean accommodative amplitude in 0.5 to 5-year old animals was 34.4 diopters; in greater than 25-year old animals it was 5 diopters. Considering the relative life expectancy and accommodative amplitude of rhesus and human, the rate of the age-dependent decline in accommodation was remarkably similar in the two species, as were the relationships between resting axial lenticular thickness and age, and between drug-induced accommodative amplitude and change in lenticular thickness. Thus, the rhesus monkey appears to provide the first known animal model for the study of accommodation and presbyopia as they occur in the human.

Accommodation, Ocular↗