Laser correction of hyperopia and presbyopia.
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Cornea↗
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An objective and subjective comparative analysis of diffractive and front surface aspheric contact lens designs used to correct presbyopia.
As bifocal contact lenses have evolved, increasing emphasis has been placed on producing designs that are less dependent on such variables as pupil size and lens centration and movement. We evaluated these and other variables in 25 presbyopic patients who underwent consecutive 1-week trials, wearing two different contact lens types: a diffractive lens and a front surface aspheric lens. Distance and near visual acuities were not significantly reduced by either lens type, and both exhibited binocular summation. With each lens design, visual acuity remained relatively independent of pupil size and small degrees of lens decentration. Contact lens movement with the aspheric design was associated with subjective fluctuations in vision to a greater extent than with the diffractive design. Contrast sensitivity was also measured and found to be reduced with the diffractive lens but not significantly altered by the aspheric lens. Overall, only two patients could not be successfully fit with either lens type. After 6 months, 21 patients (84%) reported successful lens wear with their chosen lens type.
Adult↗
Varifocal contact lenses for the correction of presbyopia.
A Nissel +1.75 D PS45 lens' label power seems to be made up of about +0.75 D distance and +0.75 D near addition. There are individual variations which will depend on pupil size, corneal shape, lens position and ocular aberrations. When a +0.75 Bausch & Lomb U3 lens was used as a control, there was also a significant increase in 'accommodation' measured (+0.75 D), but this could not be explained. When two other lenses with an aspheric surface were studied, they also showed a near addition effect. In this supplementary study the changes were explained by changes in spectacle accommodation. A lens with two spherical surfaces did not show the expected increase in spectacle accommodation. Astigmatism, as a general rule, was not corrected by the PS45 lens, although the very occasional case did show some reduction. Visual acuity and contrast sensitivity at 8 cpd and 3 cpd were not significantly affected when compared to the control lens.
Accommodation, Ocular↗
[Optical correction for presbyopia patients using computer terminals].
The study of the ergonomic conditions of office work with a computer screen, the study of the workstation, the nature of the tasks carried out and the knowledge of the visual possibilities of the user allow various optical corrections to be envisaged for this activity. Indications for monofocal, bifocal, trifocal and progressive lenses are envisaged. Optical corrections designed only for work with a screen are described.
Accommodation, Ocular↗
[Anisometropia and presbyopia: prescription of progressive lenses, a new approach].
OBJECTIVE OF THE STUDY: To show that anisometropia does not absolutely preclude the prescription of progressive lenses. MATERIALS AND METHODS: Forty-one anisometropes and presbyopes were selected for a prolonged trial of visual correction using progressive lenses. The congenital or acquired type of their anisometropia and its particular form were also studied. Each patient was submitted to a protocol comprising of a series of ophthalmologic and orthoptic tests so as to evaluate the patient's subjective far and near refraction, with measurement of phorias and of horizontal and vertical ductions, visual acuity, and the quality of binocular vision while looking in different directions. A preliminary trial of correction in actual situation was done in order to check fusion in near vision. The entire range of tests was repeated two months after the patient was provided with the lenses. The tolerance for progressive lenses during the different activities of daily life was evaluated after the second and the sixth months. RESULTS: Seven patients presenting an associated strabismus were not provided with the lenses because the initial pre-lens trial revealed a total inability to read within the near-vision zone. Among the 34 patients provided with the lenses, 21 constantly wore their progressive lenses and said that they were satisfied, 6 wore their progressive lenses during daily activities but preferred to use their unifocal lenses for prolonged reading, and 7 abandoned their progressive lenses because they could not tolerate them. Association with a strabismus is not synonymous with an initial impossibility or with abandonment because of the 27 patients who constantly wore their progressive lenses 9 were strabismic. The best results were obtained in the age range of 45 to 52 years old, for visual acuity for > 20/40, and in cases of congenital anisometropia with intermittent or permanent unilateral neutralization. On the other hand, patients presenting an acquired anisometropia, particularly postoperative, proved to be poor candidates. CONCLUSION: Weak and strong anisometropia does not absolutely preclude the prescription of progressive lenses except for certain strabismic subjects with an abnormal lateral-oriented posture.
Activities of Daily Living↗
Evaluation of two new soft contact lenses for correction of presbyopia: the Focus Progressives multifocal and the Acuvue Bifocal.
The clinical performance of Focus Progressives multifocal contact lenses and Acuvue Bifocal contact lenses was evaluated in a group of 42 presbyopes, with equal numbers of individuals having low, medium, and high spectacle add requirements. Following visual performance assessment with an optimal sphero-cylinder spectacle refractive correction, each individual wore each of the two types of contact lenses in successive random order. Each type of lens was used in a daily-wear mode for a period of 7 to 12 days, with follow-up and/or refitting visits occurring after 2 to 5 days, and again after 4 to 7 days of attempted wear. Testing for all three forms of refractive correction encompassed Snellen acuities at distance and near, Bailey-Lovie acuities under high and/or low ambient illumination conditions at near, intermediate, and far viewing distances, stereoacuity, a timed visuomotor task (needle threading), apparent glare/flare, and the nearwork range of subjectively clear binocular vision. The contact lenses also were evaluated for handling, comfort, distance and near ghosting, subjective visual quality, acceptability for common tasks (e.g., using a phone directory), and personal preferences.As might be expected, distance and near acuity, stereoacuity, and visuomotor task performance were somewhat better with sphero-cylinder spectacle correction than with either of the two types of contact lenses. However, several performance differences between the multifocal and bifocal lenses were noted. The Focus Progressives lenses provided significantly better distance acuity under both high and low illumination conditions, and received significantly higher ratings for visual quality (overall and at distance), comfort, and handling. The Focus Progressives lenses were preferred 5:1 over the Acuvue Bifocal lenses. No differences existed between the lenses with respect to near visual acuities, the perceived quality of the near vision, the nearpoint binocular range, stereoacuity, or the acceptability of vision for common nearwork tasks. The results suggest that although both types of lenses afford presbyopes a viable alternative to spectacles, the Focus Progressives lens is superior in many ways to the Acuvue Bifocal lens.
Journal Article↗
Changes in Refraction with Presbyopia.
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Journal Article↗
New intraocular lens technology.
PURPOSE: To review the current status of phakic intraocular lenses (IOLs), intraocular treatment of presbyopia, and IOLs that filter some blue light. DESIGN: Review of current information on the subject from numerous sources. METHODS: Medline search and Internet search engines on the topics of phakic IOLs, presbyopia or multifocal IOLs, and blue light and macular degeneration. RESULTS: An iris fixated phakic IOLs is now approved in the United States (US). There are concerns for corneal endothelial stability and late dislocation. Other approaches include anterior chamber fixation with concerns of corneal endothelial stability and pupil elongation, and posterior chamber fixation with concerns of cataract formation, IOL dislocation, and pigment dispersion. Intraocular treatment of presbyopia includes monovision, multifocal, and accommodative IOLs. Which approach is superior today is still not clear. There are IOLs designed to block some blue light to potentially lessen the risk of age-related macular degeneration (ARMD). While there is presumptive evidence of this, no definitive study shows such a correlation. Color perception issues are unlikely to be a problem. While decreased scotopic vision has been proposed, there is no study that proves this is an issue of clinical significance. CONCLUSIONS: The IOL field is dynamic with many new choices. Phakic IOLs and treatment of presbyopia will be an increasingly important part of ophthalmology; however, there are important unresolved issues. With better evidence that blue light is an important variable in ARMD, such an approach could rapidly become the standard.
Biomedical Technology↗
Does sunlight cause premature aging of the crystalline lens?
Premature onset of presbyopia may be an early sign of cataractous lenticular changes. For many years ultraviolet radiation (UVR) has been suspected as a major factor in the degradation of the crystalline lens. Controlled laboratory studies have demonstrated that UVR does cause opacities that closely resemble those naturally occurring in the aging process. Is it true that environmental UVR is also the prime contributor in the deleterious lenticular changes that may begin with premature presbyopia, as has been postulated? This review examines the evidence supporting this and other suggested causes of early presbyopia, including genetics, nutrition, toxins, and environmental temperature. Of all factors reported to affect the onset of presbyopia, UVR has the most scientific support, but further research is necessary to conclusively establish this link.
Aging↗
[PresbyLASIK: treatment approaches with the excimer laser].
Presbyopia represents the most common refractive error. There is currently no surgical treatment for presbyopia, which is effective, reliable, and safe. Excimer laser surgery has become a routine procedure for the correction of myopia, hyperopia, and astigmatism for years. Various treatment strategies for presbyopia have been brought forward using the excimer lasers. Besides monovision, creation of a multifocal cornea represents an attractive option. This procedure is also called "PresbyLASIK." Different ablation profiles to form a multifocal cornea are reviewed here and first clinical results are summarized."PresbyLASIK" is a new, interesting treatment strategy, with a huge potential for the future. At the present it should be used in controlled studies only because of some unsolved questions.
Humans↗
Age-dependent changes in visual acuity and retinal morphology in pigeons.
The visual acuities of 17 pigeons that ranged in age from 2 to 17 years were tested with high-contrast, square-wave gratings. A systematic decline in visual acuity was observed that was well described by a logarithmic function. Pupillary diameter also declined with age, which decreased retinal illumination, but increased depth of focus. A small amount of presbyopia also was observed. Both the decrease in retinal illumination and the presbyopia accounted for only a trivial proportion of the acuity loss. No relationship between corneal or lenticular density and age was observed. Ophthalmoscopic examination of the optic media revealed no abnormalities associated with age. Microscopic examination of the area dorsalis of the retina (the high-density region specialized for frontal vision) revealed age-related losses of up to 33% of photoreceptors and 23% of cells in the ganglion-cell layer. A study of the photoreceptor layer within area dorsalis indicated that single-cone densities were unaffected by aging whereas the double-cone densities, which are the predominant photoreceptor type in the area dorsalis, were reduced in number by about one third. Calculation of the Nyquist limit both for photoreceptors and ganglion cells suggested that the decreased retinal density together with the decreased retinal illumination and presbyopia could not account for all of the observed acuity loss.
Aging↗
Age-related changes in the accommodation mechanism.
Presbyopia is caused by changes in the visco-elastic properties of the lens or the choroid or both. Far-to-near (FN) accommodation dynamics are dominated by the properties of the lens, whereas near-to-far (NF) accommodation dynamics depend on the properties of the lens as well as the choroid. The aim of this study was to gain more insight into the cause of presbyopia by analyzing how FN and NF accommodation dynamics change as a function of age. Changes in axial lens thickness during accommodation were measured in vivo using continuous ultrasonographic biometry. The measurements were analyzed with the use of a biomechanical model of the mechanism of accommodation. Fitting the model to the responses yields time constants of FN and NF accommodation. The time constants FN and NF increase with age at an approximately equal rate: 7 ms/year (+/- 1.8 SEM) and 6 ms/year (+/- 1.6 SEM), respectively. This result supports a lenticular cause of presbyopia. In addition, estimations of the lens damping coefficients at different ages are given for the first time: the damping coefficient of the lens increases 20-fold between 15 and 55 years of age.
Accommodation, Ocular↗
Polymer refilling of presbyopic human lenses in vitro restores the ability to undergo accommodative changes.
PURPOSE: Because presbyopia is thought to be accompanied by increased lens sclerosis this study was conducted to investigate whether refilling the capsule of the presbyopic human lens with a soft polymer would restore the ability of the lens to undergo accommodative changes. METHODS: Accommodative forces were applied to natural and refilled lenses by circumferential stretching through the ciliary body and zonular complex. Nine natural lenses and 10 refilled lenses from donors ranging in age from 17 to 60 years were studied. Two refill polymers with a different Young's modulus were used. The lens power was measured by a scanning laser ray-tracing technique, and lens diameter and lens thickness were measured simultaneously while the tension on the zonules was increased stepwise by outward pull on the ciliary body. RESULTS: In the natural lenses the older lenses were not able to undergo power changes with stretching of the ciliary body, whereas in the refilled lenses, all lenses showed power changes comparable to young, natural lenses. The refilled human lenses had a higher lens power than the age-matched natural lenses. The Young's modulus of the polymers influenced the lens power change when measured with the ciliary body diameter increased by 4 mm. CONCLUSIONS: Refilling presbyopic lenses with a soft polymer enabled restoration of lens power changes with mechanical stretching. Because sclerosis of the lens is an important factor in human presbyopia, refilling the lens during lens surgery for cataract could enable restoration of clear vision and accommodation in human presbyopia.
Accommodation, Ocular↗
[Prevalence of near vision deficiency and related factors: a population-based study].
The objective of this article was to estimate the prevalence of presbyopia in adults > or = 30 years and explore associated characteristics such as demographic, socioeconomic, and individual variables. A cross-sectional, population-based study was performed with 3,007 adults > or = 30 years in Pelotas, Rio Grande do Sul, Brazil. Near vision acuity was evaluated using the Jaeger table, and other variables were investigated using standardized, pre-coded questionnaires. Prevalence of presbyopia was 54.7%. When visual acuity was measured using visual corrective means, prevalence was 29.34%. Age and female gender were associated with the outcome variable after controlling for confounding. Some 42.4% of the sample reported not requiring near vision for routine daily tasks. The conclusion was that presbyopia displays a high prevalence in the adult population and is directly related to increasing age, especially 45 years of age and appearing earlier in women. In some 30% of individuals who already use visual corrective means, the latter are ineffective for near vision.
Adult↗
Visual performance of a multi-zone bifocal and a progressive multifocal contact lens.
PURPOSE: This study measured the relative visual performance of two planned-replacement soft contact lenses for presbyopic correction: a multi-zone bifocal (ACUVUE, Johnson & Johnson Vision Care, Jacksonville, FL) contact lens and a progressive multifocal (Focus Progressives, CIBA Vision, Duluth, GA) contact lens. METHODS: This was a randomized, double-masked, non-dispensing cross-over study. Visual performance was evaluated by log of minimal angle of resolution (LogMAR) measurement of visual acuity (VA) under a representative range of luminances (distance 250 candela[cd]/m2 and 2.5 cd/m2, near 250 cd/m2 and 50 cd/m2) and contrasts (90% and 10%). The 45 presbyopic subjects were equally distributed in three subgroups according to spectacle addition: low presbyopia (+0.75D to +1.25D); medium presbyopia (+ 1.50D to + 1.75D); and high presbyopia (+2.00 to +2.50D). RESULTS: Statistically significant differences were found in overall distance VA (P<0.001; average of four luminance-contrast combinations) and low-luminance distance VA (P=0.004), which, in both cases, favored the multi-zone bifocal lens design. For low presbyopes, the multi-zone bifocal design produced a significantly better visual performance (P=0.004) than did the progressive multifocal. Overall near VA was also significantly better (P<0.001) with the multi-zone bifocal lens. Differences in near VA were particularly marked in high-luminance conditions (high and low contrasts combined) and were statistically significant for all three presbyopic subgroups. CONCLUSIONS: Visual acuity performance with the multi-zone bifocal was superior overall to that achieved with the progressive multifocal design. This study suggests that having only one addition is detrimental to performance with the progressive multifocal lens, particularly for low presbyopes.
Adult↗
Simple spectacles for adult refugees on the Thailand-Burma border.
PURPOSE: This article describes the development of, and outputs from, a program in which trained refugee health workers provided spherical lenses to adult refugees along the Thailand-Burma border. METHODS: Between 1998 and 2001, the International Rescue Committee trained 48 refugee health workers in basic refraction courses. Once trained, these health workers conduct weekly eye clinics in several refugee camps and one migrant community covering a total population of 142,000. We supplied spherical lenses in 11 powers from +1.00 to +4.00 in 0.50-D steps and from -1.00 to -2.50 in 0.50-D steps. We collected output data from these clinics for the year 2001. RESULTS: In 2001, these clinics provided a total of 7219 eyeglasses. Approximately 84% of all lenses given were for presbyopia, approximately 10% for myopia, and approximately 6% for hyperopia. Our spectacle provision rates per 100,000 persons were 4284 for presbyopia, 482 for myopia, and 317 for hyperopia. Our target provision rates, which would allow the average wearer to get a new pair every 3 to 4 years, was met for presbyopia, but not met for myopia or hyperopia. Few corrections for high errors were needed and only 92 people were found to need powers higher than we provided. In 2001, the cost per eyeglass recipient was approximately $7.00. CONCLUSIONS: Training refugee health workers has allowed for sustainable, low-cost spectacle provision to a large population over an extensive geographic area in a challenging environment.
Adult↗
Diode laser thermal keratoplasty to correct hyperopia.
PURPOSE: We investigated long-term efficacy, predictability, stability, and safety of diode laser thermal keratoplasty (DTK) to correct hyperopia. METHODS: DTK was performed on 24 eyes (18 patients). Eight eyes with high hyperopia (mean +4.75 +/- 0.63 D; range +3.50 to +5.50 D) received 12 pairs of coagulation spots at 6-mm and 7-mm treatment zone diameters; eight eyes with low hyperopia (mean +2.25 +/- 0.40 D; range +1.50 to +2.75 D) received eight coagulation spots at 8 mm, and eight eyes with low hyperopia (mean +1.50 +/- 0.46 D; range +1.25 to +2.25 D) were treated to induce mild myopia (-1.50 D) in the non-dominant eye for monovision using eight pairs of spots at 7 and 8-mm diameters. Minimum follow-up was 18 months. RESULTS: Mean decrease in cycloplegic refraction at 18 months was 5.00 +/- 0.38 D in the high hyperopia group, 1.75 +/- 0.19 D in the low hyperopia group, and 3.25 +/- 0.27 D in the presbyopia group. Mean increase in uncorrected visual acuity (UCVA) at 18 months was 8.125 +/- 2.1 Snellen lines in the high hyperopia group, 6.625 +/- 0.744 lines for low hyperopia; decrease of 1.00 +/- 1.85 line occurred in the presbyopia group. Near UCVA in the presbyopia group improved by 3.875 +/- 0.83 Jaeger lines. Best spectacle-corrected visual acuity (BSCVA) was restored by 3 months in all eyes. CONCLUSION: DTK was an effective and fairly safe procedure, with reasonable predictability and stability. Nomograms for laser energy level, treatment zone diameter, and number of spots need improvement.
Adult↗