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PubMed1987

Accommodation of an endocapsular silicone lens (Phaco-Ersatz) in the nonhuman primate.

In owl monkeys, as a model of endocapsular cataract extraction, the lens material was removed through a small hole in the capsule and was replaced with a silicone polymeric gel. The ability of this endocapsular implant (Phaco-Ersatz) to accommodate was documented when pilocarpine produced an increase in the curvature of the lens surface and a decrease in the anterior chamber depth, just as occurs with the untouched natural lens. Refinements of the surgical technique are required to achieve a controlled degree of filling of the capsular bag and inhibit postoperative epithelial proliferation on the inner capsular surface.

Accommodation, Ocular↗
PubMed1997

Penalization versus part-time occlusion and binocular outcome in treatment of strabismic amblyopia.

OBJECTIVE: The purpose of the study is to compare the visual outcome of occlusion versus penalization treatment of strabismic amblyopia, with particular attention to binocularity outcome. DESIGN: The study design was a retrospective study. PARTICIPANTS: Patients with strabismic amblyopia, 75 receiving penalization alone, 87 with a history of occlusion treatment who were later treated by penalization, and 30 treated by means of part-time occlusion (2 to 6 hours/day) participated in this study. MAIN OUTCOME MEASURES: Logarithm of the minimum angle of resolution (logMAR) visual acuity and binocularity index were measured. RESULTS: No statistically significant difference was found between outcomes for the penalization groups with and without a history of occlusion, either by univariate analysis or by multivariate analysis controlling for initial-visit age, acuity, and binocularity status. One marginally significant outcome difference was found between the pure penalization and part-time occlusion groups by univariate analysis, but no significant difference was found in the multivariate analyses controlling for the same three variables at the initial visit. All visual outcome differences between the pure penalization and part-time occlusion groups were less than 1 logMAR line visual acuity or less than a half-unit on the binocularity index. CONCLUSIONS: The study provided no evidence of a difference in visual function outcome between penalization and occlusion, in terms of either statistical or clinical significance, although limitations of the patient samples used preclude these data from showing conclusively that there was no such difference. The lack of any other study adequately comparing these two treatment methods, in combination with the current study's demonstration of the difficulty of making adequate retrospective-based comparison despite a large patient base (n = 1413), suggests that a large prospective, randomized comparative treatment trial is needed. If atropine penalization, with its high acceptability to patients and parents, is found to produce results comparable with those of occlusion in cases of mild-to-moderate amblyopia, as the current and previous smaller studies suggest, then reconsideration of the standard of care for such amblyopia cases is indicated.

Accommodation, Ocular↗
PubMed1997

Full-time atropine, intermittent atropine, and optical penalization and binocular outcome in treatment of strabismic amblyopia.

OBJECTIVE: The purpose of the study is to evaluate the monocular and binocular outcome of three types of "penalization" (blurring of the sound eye) treatment of amblyopia: traditional full-time atropine or optical penalization and a new intermittent atropine regimen involving atropine instillation 1 to 3 days a week. DESIGN: The study design was a retrospective study. PARTICIPANTS: A total of 163 patients with strabismic amblyopia treated by full-time atropine (n = 38), intermittent atropine (n = 73), or optical (n = 52) penalization participated. MAIN OUTCOME MEASURES: Logarithm of the minimum angle of resolution (logMAR) visual acuity, and binocularity index were determined. RESULTS: All three forms of penalization produced statistically significant mean reduction in amblyopia (1.7-2.7 logMAR lines) and mean improvement in binocularity by the end-of-treatment or long-term follow-up visit or both, with minimal mean loss after discontinuation or slight mean improvement on these measures at long-term mean follow-up of 1.9 to 4 years across groups. Few patients achieved high-grade stereoacuity. Compliance was high. Comparable efficacy was found for all three treatment groups after controlling for age, depth of amblyopia, and binocularity at the initial visit. Initial-visit amblyopia depth was strongly and significantly associated with amblyopia depth at both post-treatment visits. Pretreatment and post-treatment binocularity showed a similar strong relationship. Surprisingly, however, there was no consistent or significant association found between depth of amblyopia and binocularity in any visit combination. Post-treatment measures of these two variables also were not associated with initial-visit age or refractive error at any clinically significant level. Mean treatment duration was 1.1 to 2.9 years and was not found to be associated with visual outcome. Amblyopia reversal was found in one (full-time atropine) case at a clinically important level. CONCLUSIONS: The authors confirmed previous reports of penalization's efficacy as a primary treatment of moderate amblyopia (20/100 or better acuity) and, in some cases, relatively severe amblyopia (>20/100) and also confirmed its ability to significantly improve mean binocularity. Amblyopia and binocularity appear to respond to treatment independently and, within the postinfancy age range of the sample studied, the responses appear to be independent of initial-visit age. The high acceptability to patients and parents of atropine penalization, and particularly of the intermittent regimen introduced here, suggests the need for prospective-study-based re-evaluation of the relative merits of penalization and occlusion as the standard of care for mild-to-moderate amblyopia.

Accommodation, Ocular↗
PubMed1998

Anterior shift of zonular insertion onto the anterior surface of human crystalline lens with age.

OBJECTIVE: This study aimed to investigate the age-related changes in the position of zonular insertion onto the anterior lens capsule. DESIGN: The study design was an experimental cadaveric eye study. PARTICIPANTS: Two hundred twenty-three cadaveric eyes (range, 16-100 years old) from eye banks in the United States were studied. INTERVENTION: The zonular insertion onto the anterior capsule was detected using a modified posterior photographic technique. MAIN OUTCOME MEASURES: The distances from the anterior zonular insertion (AZI) to the lens equator and to the ciliary sulcus, size of zonular-free zone, lens diameter, ciliary sulcus diameter, and axial length of the globe were measured. RESULTS: Multiple regression analysis showed that age, lens diameter, and axial length of the globe had significant correlations with AZI (r2 = 0.748), among which age showed the highest relevance with AZI. Multiple regression equation was expressed as AZI = (0.0079 x age) + (0.202 x lens diameter) - (0.041 x axial length of the globe) + 0.0114. The increase in AZI was accompanied by a decrease in the size of zonular-free zone with age (r = -0.206, P < 0.001). CONCLUSION: Aging correlates with an increase in the distance from the anterior zonular insertion to the lens equator and a decrease in zonular-free zone.

Accommodation, Ocular↗
PubMed1999

Scleral expansion surgery does not restore accommodation in human presbyopia.

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.

Accommodation, Ocular↗
PubMed1999

Relationship between apparent accomodation and corneal multifocality in pseudophakic eyes.

OBJECTIVE: To investigate whether any association exists between apparent accommodation in pseudophakic eyes and multifocal corneal effects. DESIGN: A prospective observational case series. PARTICIPANTS: A total of 121 eyes of 98 patients who had undergone phacoemulsification and posterior chamber intraocular lens implantation were studied. METHODS: The amount of apparent accommodation was measured using an accommodometer. The degree of corneal multifocality was determined on the corneal topography by measuring the maximum and minimum corneal refractive powers within the pupillary area. Refractive astigmatism, keratometric astigmatism, pupillary diameter, and age were also analyzed. MAIN OUTCOME MEASURES: Apparent accommodation, corneal multifocality, refractive and keratometric astigmatism, pupillary diameter, and age. RESULTS: Multiple regression analysis revealed that corneal multifocality and pupillary diameter had significant positive correlations with apparent accommodation, whereas other explanatory variables showed no relationship with apparent accommodation. CONCLUSION: Multifocal corneal effects contribute to apparent accommodation in pseudophakic eyes.

Accommodation, Ocular↗
PubMed1992

Development of accommodation and convergence in infancy.

Paraxial photorefraction was used to assess the development of accommodation and convergence in a large sample of infants under 1 year of age. The infants viewed small dolls placed at various distances (200-25 cm). The majority of infants at all ages demonstrated appropriate convergence for target distance, regardless of manifest refractive error. However, accommodation lagged behind convergence in development. Infants under 2 months tended to demonstrate either flat accommodation responses with a fixed plane of focus at around 30 cm, or accommodated appropriately for near targets, but failed to relax their accommodation sufficiently for the more distant targets. Thus, the focussing error increased with increasing target distance. Since the manifest refractive error was estimated by extrapolating the accommodation function to 0 diopters demand, these infants demonstrated spuriously myopic behavior. After 2 months, the majority of infants showing emmetropic behavior had accommodation responses that changed appropriately with target distance. However, infants with myopic or hyperopic manifest refractive errors displayed a variety of accommodative styles.

Accommodation, Ocular↗
PubMed2005

[Refractive phakic IOLs: three different models and contact with the crystalline lens. An AC-OCT study].

Three patients received three different models of phakic implants. With the usual slit-lamp examination method, we were not able to establish whether there was contact between the implants and the natural crystalline lens. Using the anterior chamber optical coherence tomography scanner (AC-OCT), we were able to demonstrate that there was direct contact between the natural crystalline lens and the three different phakic implants. A dynamic study of these contacts was carried out during accommodation. These observations show that examination of the anterior segment with the optical coherence tomography scanner is essential in refractive surgery.

Accommodation, Ocular↗
PubMed2005

[An in vivo OCT study of human natural accommodation in a 19-year-old albino].

Modifications of the anterior segment during accommodation of the eye under examination cannot be studied in a simple and direct way with anterior segment imaging techniques such as Scheimpflug photography, A Scan, B Scan, and UBM. With this equipment, it is necessary to stimulate the fellow eye in order to observe the variations of the analyzed eye. The techniques using ultrasound equipment can only be used with contact systems or with water baths that will modify the anatomical dimensions or the pressure of the anterior segment. With the Scheimpflug photographic technique, geometrical reconstructions are necessary and cannot be used in certain axes. Optical coherence tomography provides the advantage of producing non-contact images of the anterior segment in static and dynamic conditions that are then easy to use. The target of the optical system can be focused and unfocused with negative or positive lenses, thus reproducing the conditions of natural accommodation. With a normal subject, the morphological modifications of the crystalline lens behind the iris screen cannot be studied because the infrared light source used is blocked by the pigment epithelium. The absence of this pigment in an albino subject allowed us to study the modifications of the crystalline lens and the ciliary body during accommodation. In this study, we were able to definitely confirm all the modifications of the anterior segment as described by von Helmholtz in 1855, who, at the time, used very rudimentary optical procedures based on the reflections of a flame on the surface of the crystalline lens.

Accommodation, Ocular↗
PubMed2000

Intraocular lens power calculations in patients with extreme myopia.

PURPOSE: To determine the variables that might contribute to improved intraocular lens (IOL) power calculations preoperatively in cataract patients with extreme myopia. METHODS: This retrospective study included 50 patients with extreme myopia and axial lengths longer than 27.0 mm. All patients had clear corneal phacoemulsification by the same surgeon and implantation of the Domilens SiFlex 1 IOL (power range -6.0 to +5.0 diopters [D]). The performances of the SRK/T, Hoffer Q, Holladay 1, and Holladay 2 formulas in predicting an IOL power that would meet the target refraction of +/-1.00 D were compared. RESULTS: The formulas tended to suggest underpowered IOLs, more severe in eyes with axial lengths greater than 30.00 mm. These eyes accounted for most of the minus-power IOLs implanted. Back calculations of axial lengths in patients with minus-power IOLs showed that, on average, emmetropia could have been predicted by choosing shorter axial lengths (up to 2.72 mm shorter) than those used in the original IOL power calculations. Preoperative B-scan ultrasonography demonstrated the presence of a posterior pole staphyloma temporal to the optic nerve in several patients who required minus-power IOLs, which suggests that axial length measurement problems were a major source of IOL calculation errors in these patients. CONCLUSIONS: In eyes with axial lengths longer than or equal to 27.0 mm, current third- and fourth-generation lens calculation formulas have a tendency to over minus patients between -1.0 and -4.0 D. The formulas appear to perform better for plus-power IOL implantation than for minus-power IOL implantation. The use of B-scan ultrasonography to locate posterior pole staphylomas may improve the accuracy of IOL calculations in eyes with extreme myopia.

Accommodation, Ocular↗
PubMed2002

Nonaccommodative esotropia after cataract extraction in a patient with previous accommodative esotropia.

We report a case of nonaccommodative esotropia developing after bilateral cataract surgery that corrected the preexisting hyperopia in a patient with accommodative esotropia since childhood. The esotropia required surgical correction despite the good visual acuity after the cataract surgery. In patients with preexisting strabismus, there is a possibility of decompensation of adaptive binocular mechanisms after cataract surgery and refractive procedures.

Accommodation, Ocular↗