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As a consequence of a new understanding of the mechanism of accommodation, a unique surgical procedure has been developed which can reverse presbyopia. The basic pathophysiology involved in the development of presbyopia may have implications in the etiology and treatment of ocular hypertension and primary open angle glaucoma.
PURPOSE: To characterize changes in the sagittal dimensions of the human crystalline lens and anterior segment as a function of accommodation, to determine the potential age dependence of these changes, and to evaluate these changes in relation to the development of presbyopia. METHODS: Scheimpflug slit-lamp photography, as well as a variety of standard ophthalmologic methods, was used to collect information about lens and anterior segment sagital dimensions in a population of 82 adults with refractive error < or = magnitude of 2.0 diopters and at least 0.25 diopter of accommodation for subjects 18 to 70 years of age. Data were analyzed statistically for dependence on accommodation, age, and age dependence of accommodative rate. RESULTS: The rate of change per diopter of accommodation for each measured variable within the lens is independent of age for the entire adult age range. With increasing accommodation, the lens becomes thicker and the anterior chamber shallower along the polar axis. This increase in sagittal lens thickness is entirely because of an increase in the thickness of the lens nucleus. Because the anterior and posterior halves of the nucleus increase in thickness at approximately the same rate with accommodation, the increase in lens thickness results from equal changes in the lengths of the anterior and posterior portions. CONCLUSIONS: Because changes along the sagittal axis of the anterior segment with accommodation are independent of age, any explanation of presbyopia that relies on simple changes in the rates of lens thickening and anterior chamber shallowing with age does not hold. In light of other age-related changes in the anterior segment and lens (e.g., increased sharpness of lens curvature, increased lens sagittal thickness, decreased anterior chamber depth), it appears that compensatory mechanisms to preserve far vision with age also preserve the rate of change per diopter of sagittal spacings.
The crystalline lens changes both optically and mechanically with age: it becomes less transparent and more difficult to deform. Using a new ultrasound technique, Continuous Ultrasonographic Biometry (CUB), we were able to demonstrate that presbyopia is caused by increased stiffness of the lens due to changes in lens fibre membranes and cytoskeleton. These results are important for further research on the ageing processes that lead to cataract and presbyopia, and the treatment of these conditions.
The aim of this study was to examine the extent to which the age-related variations of properties of the human lens may be able to account for presbyopia. Dimensionless linear regressions were calculated for age-related biological functions with special reference to ocular and lenticular ones. Their intercepts on the x-(age-)axis are compared, and their distribution is analyzed. An analysis was made of the effect of the growth of the lens on the relation between its shape and the proximal zonular anchorages on the one hand and the age-related variation of the angle between the zonule and the equatorial plane of the lens. The lens is not unusual in seeming to have evolved in support of a life-span of about 120 years. Presbyopia, however, fails to fit into the general picture and this is hypothesized to result from lenticular growth and a combination of factors which are not all governed by senescence. The potential involvement of the root of the iris throws an interesting light on the apparently worldwide variation of the condition.
Presbyopia is age-related reduction in amplitude of accommodation and the loss of the ability to change the eye's focus from far to near. It is the one of the most common age-related ailment. Traditional methods such as spectacle glasses or contact lenses are still the most widely used for correction of the problem. This article is an attempt to review the surgical options available for presbyopia.
By means of a fine conical probe and a miniature dynamometer, the resistance to penetration of different lens layers was measured. In clear human lenses the power of resistance of the lens nucleus increases with age, mostly due to the "hardening" of the nucleus. A distinct hardening of the nucleus as opposed to the cortex has been found to occur in lenses as young as 20 years of age. This "firmness" of the lens nucleus, occurring between the ages of 20 and 60 years, coincides with the decrease in accommodation range and the onset of presbyopia.
BACKGROUND: Ultrashort (femtosecond) laser pulses can generate precise cuts in biological tissue without damaging the surface. The application of femtosecond laser technology at the lens was evaluated with respect to a possible treatment of presbyopia. MATERIALS AND METHODS: Femtosecond laser lentotomy was performed on 150 pig lenses in vitro. Cutting geometry and laser settings were optimized to generate smooth cuts with a minimum of produced gas bubbles. Four rabbit lenses were treated afterwards in vivo and were controlled for 3 months post-treatment. The lenses were then extracted and evaluated. RESULTS: With suitable laser settings, light scattering due to residual gas bubbles could be almost completely avoided in pig lenses. A pulse energy of less than 1.2 microJ and a cutting geometry with spot separations of more than 5 microm are important. The rabbit lenses stayed macroscopically clear for 3 months in vivo. Only the cell structures directly adjacent to the laser focus were cut; structures 5-10 microm away appeared to be intact. No cataract formation occurred during this time. CONCLUSION: Femtosecond laser application allows precise and smooth cuts inside pig and rabbit lenses without damage to adjacent tissue.
A new technique, the scleral expansion band procedure, has been developed for the surgical reversal of presbyopia. An understanding of demonstrable clinical effects of the scleral expansion band procedure, based on Schachar's theory, requires a revision of historically held views concerning the mechanism of accommodation.
A 57-year-old woman was treated for mild presbyopia with implantation of scleral expansion bands (SEB). Although near vision was temporarily restored, the effect dissipated after 1 year. Slitlamp-adapted optical coherence tomography (OCT) at 1310 nm allowed precise cross-sectional visualization of the hyporeflective intrascleral segments. The OCT method provided precise images of the segment depth and thickness, the scleral thickness at the scleral spur, the anterior chamber angle, and the angle-opening distance. Intrascleral tilting of 1 segment was seen; this required removal of the SEB because of marked foreign-body sensation. Noncontact, slitlamp-adapted OCT can be used to evaluate scleral changes after SEB implantation.
The authors present their detailed technique for the correction of presbyopia with pseudoaccommodative cornea laser in situ keratomileusis. A detailed commentary of the procedure is presented along with the authors' views about the present state and future of multifocal corneal surgery. Sample cases with suggested nomogram calculations are presented.
There has been no comprehensive study involving each of the primary dynamic components of accommodation in the same cohort as related to age and presbyopic onset; furthermore, the current findings are equivocal. Dynamic monocular components of accommodation (latency, time constant, peak velocity/amplitude relationship, and microfluctuations) were assessed objectively using an infrared optometer within the linear region of accommodation in 30 visually-normal human subjects aged 21-50 years. The time constant and the peak velocity/amplitude relationship did not change with age. However, latency progressively increased, and microfluctuation amplitude and frequency progressively decreased, with increasing age. The invariance in time constant suggests that the gross biomechanical aspects of the lens and related structures in the remaining linear region are relatively unaffected by age. In contrast, the decrease in microfluctuation activity with age suggests more subtle alterations in the biomechanical aspects of the lens to these very small perturbations, such as a response amplitude non-linearity. With respect to neurologic control, the progressive latency increase suggests a processing delay of the blur input, and this is consistent with age-related changes in reaction time measures. The lack of any age-related changes in the peak velocity/amplitude relationship implies normalcy of central and peripheral neuromotor control, as well as grossly normal first-order lens biomechanics, in this linear response region. The results are consistent with the Hess-Gullstrand theory of presbyopia.
PURPOSE: To report a patient who developed complications from an experimental technique using scleral expansion to treat presbyopia. METHODS: Case report of a 46-year-old woman who underwent scleral expansion surgery on her right eye. Postoperatively, the patient developed chronic pain and swelling that necessitated removal of the scleral expanders. RESULTS: After removal of the scleral expanders, the patient demonstrated a -1.4 diopter myopic shift in the right eye relative to her preoperative refraction. Axial length of the right eye was 1.15 mm longer than of the left, whereas preoperative axial lengths were equal. CONCLUSION: This patient developed scleral thinning with resultant axial lengthening and myopic shift, akin to the phenomenon observed with scleral buckles used to treat retinal detachments. We believe this was responsible for improved near vision in her right eye, rather than any increased accommodative potential purported to result from this operation.
PURPOSE: To assess the effects of scleral expansion band (SEB) segments on accommodative amplitude (primary measure), along with near and distance vision, refraction, pupil size and function, keratometry, axial length, intraocular pressure, contrast sensitivity, stereopsis, and other parameters (secondary measures) in a cohort of 29 emmetropic, presbyopic patients. DESIGN: Multicenter, prospective, nonrandomized, unmasked clinical trial in which the nonoperated eye served as the control. METHODS: Four polymethylmethacrylate segments were surgically implanted in quadrantic scleral pockets created in the dominant eye of 29 emmetropic patients who were between the ages of 51 and 60 (mean age 54). Patients were examined preoperatively and up to 6 months postoperatively. The aforementioned tests were performed on the operated and control eye of each patient. Data were analyzed using two-sided rank tests. Medians, means, and standard deviations are provided for all measurements. RESULTS: Accommodative amplitude was measured monocularly using a near-point "push" technique from both a 70-cm and 30-cm starting point. An increase in accommodative amplitude of surgical eyes by +1.7 +/- 1.5 diopters and +1.5 +/- 1.2 diopters, at these two testing distances, respectively, was noted at 6 months postoperatively (P <.0001). A smaller increase was also seen in control eyes (+1.2 +/- 1.1 diopters and +1.3 +/- 1.2 diopters, respectively). There was notable intercenter variation in gains in accommodation, with three of seven centers showing significant improvement in near-point accommodative amplitudes relative to the others (P =.0003). There was a median improvement of uncorrected near acuity in surgical eyes by 0.3 logarithm of the minimal angle of resolution (logMAR) at 30 and 40 cm and by 4 lines at 20 cm, with the difference in near acuity improvement at 6 months between SEB eyes and control eyes statistically significant at 20 cm (P <.030). Changes in spherical equivalence, axial length, and central keratometry readings were not statistically significant. There were no reports of anterior segment ischemia or malignant glaucoma. Adverse effects were limited to a transient elevation of intraocular pressure in one patient and misalignment of individual SEB segments, due to inadequate scleral pocket formation, in three patients. Only one SEB segment in one eye was replaced. It appears that the thickness and uniformity of the scleral belt loop is critical to the proper positioning and efficacy of the SEB segments. CONCLUSION: While the safety profile of SEB segments for the treatment of presbyopia was high, a modest improvement in near vision was noted in approximately half the patients using subjective methods of testing. The mechanisms that underlie improvement in near vision in the nonoperated eye await explanation. This may be due to a centrally controlled consensual response, potentiated convergence generating increased intravitreal pressure and hydraulic lift of the vitreo-zonular-lens diaphragm, or artifact from current testing techniques. Future studies of the SEB procedure should address the issue of intercenter variation by further standardizing and automating specific aspects of the surgical technique, as well as incorporating objective testing methods into the study design.
Limitations in existing studies of the epidemiological aspects of refraction are attributed to both technical and statistical procedures. Early influences of ocular parameters on refraction are identified accordingly as prematurity and may or may not be involved. Attention is paid to familial and genetic influences, and infants and toddlers are examined as a group separate from schoolchildren and teenagers, who are likely to have experienced significant periods of near work. The effects of sex and geographical distribution are considered both for younger and older age ranges. Special attention is paid to anisometropia, which is shown-apparently for the first time-to increase appreciably among presbyopes. The connection between refractive errors and ocular pathologies is reviewed, and possible means of preventing early onset myopia are examined. Presbyopia is addressed with reference to its geographical distribution and hypothetical links to accommodation insufficiency.
Lenses from 27 human eyes ranging in age from 10 to 87 years were used to determine how accommodation and age affect the optical properties of the lens. A scanning laser technique was used to measure focal length and spherical aberration of the lenses, while the lenses were subjected to stretching forces applied through the ciliary body/zonular complex. The focal length of all unstretched lenses increased linearly with increasing age. Younger lenses were able to undergo significant changes in focal length with stretching, whereas lenses older than 60 years of age showed no changes in focal length with stretching. These data provide additional evidence for predominantly lens-based theories of presbyopia. Further, these results show that there are substantial optical changes in the human lens with increasing age and during accommodation, since both the magnitude and the sign of the spherical aberration change with age and stretching. These results show that the optical properties of the older presbyopic lens are quite different from the younger, accommodated lens.
OBJECTIVE: To demonstrate a plausible explanation of aging changes and to reduce the controversy relative to accommodation by using a mechanical model of the catenary theory of lens change. MECHANICAL MODELING: A mechanical model was used to simulate a human lens in both the accommodated and unaccommodated state to demonstrate changes in the mechanism of accommodation with age. METHODS: Fluid-filled latex balloons were supported by a plastic wrap hammock to form a catenary that models the human lens. Increasing volumes were used to simulate that of the aging lens, and variations in curvature were measured. MAIN OUTCOME MEASURES: The degree of curvature of a simulated anterior lens surface was measured and compared with mathematical modeling of its optical surface based on the catenary hydraulic suspension theory. RESULTS: The measurements showed that accommodative loss and other features such as mass displacement, reproducible lens surfaces, and zonule support are consistent with the catenary theory of accommodation and an increasing lens volume with age. CONCLUSIONS: The catenary theory of accommodation provides a basis for evaluating age changes of the human lens. Variable results with surgical procedures for presbyopia are also predictable with the model. These results can be used to provide a basis for intraocular lens design.
OBJECTIVE: To determine the efficacy of scleral expansion surgery in the treatment of human presbyopia. DESIGN: Experimental study. PARTICIPANTS: Three preoperative presbyopic subjects, three postoperative presbyopic subjects, and three young control subjects. METHODS: Accommodative responses were recorded by an infrared dynamic optometer while subjects viewed an accommodative stimulus that stepped from 0 to 4 diopters in 1-diopter steps. MAIN OUTCOME MEASURES: Dynamic infrared optometer recordings of accommodation. RESULTS: Presbyopic patients showed no evidence of accommodation after scleral expansion surgery. CONCLUSIONS: If presbyopic patients read smaller letters at near after scleral expansion surgery than they were able to read prior to the surgery, then an explanation other than the restoration of accommodation needs to be found.
INTRODUCTION: Presbyopic surgery is considered as the new frontier in refractive surgery. Different solutions are proposed: myopization of one eye, insertion of an accommodative crystalline lens, scleral surgery, the effects of which are still unknown, and finally multifocal phakic implants. We therefore decided to undertake a prospective study under the Huriet law to determine its efficacy and specify the conditions required for an anterior chamber multifocal phakic implant. MATERIAL AND METHOD: Fifty-five eyes of 33 patients received an anterior chamber foldable multifocal phakic implant. Twenty-one females and 12 males underwent surgery. Initial refraction was between -5D and +5D. The implant's single addition was +2.50. Recuperating a distant uncorrected visual acuity of 0.6 or better and near uncorrected vision of Parinaud 3 or better can be considered a very good postoperative result. RESULTS: Average follow-up was 42.6+/-18 weeks. Mean postoperative refraction was -0.12+/-0.51 D. Mean postoperative uncorrected visual acuity was 0.78+/-0.20. Postoperative uncorrected visual acuity was Parinaud 2.3+/-0.6. Eighty-four percent of eyes operated on recuperated 0.6 or better without correction and Parinaud 3 or better without correction. Lenses in four eyes were explanted for different reasons, essentially optical, and no severe anatomical complications were observed. CONCLUSIONS: Placing an anterior chamber multifocal phakic implant to correct presbyopia is an effective technique with good predictability and has the advantage of being reversible in case of intolerance, optical parasite effects or undesired complications. Considering the particularity of this surgery, it is imperative to respect very strict inclusion criteria: anterior chamber depth equal to or above 3.1 mm, open angle, endothelial cell count equal to or above 2000 cells/mm2, absence of an incipient cataract or the slightest evidence of macular alteration.