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PubMed2004

Secondary procedures after presbyopic lens exchange.

PURPOSE: To assess the indications, incidence, and outcome of secondary procedures after presbyopic lens exchange (PRELEX). SETTING: Private practice, Siena, Italy. METHODS: This prospective nonrandomized single-surgeon study comprised 52 patients having PRELEX by phacoemulsification and multifocal intraocular lens (IOL) implantation. The preoperative mean spherical equivalent (SE) was +2.50 diopters (D) +/- 1.38 (SD) (range 0 to +6.0 D). RESULTS: Monocular PRELEX was performed in 8 patients who canceled the fellow-eye surgery because of halos; in this group, the residual refractive error was corrected by photorefractive keratectomy (PRK) in 4 eyes, but this did not alleviate halos and IOL exchange was ultimately needed in 7 eyes. Binocular PRELEX was completed in 44 patients; in this group, 14 eyes (8 patients) had PRK for a residual error. The postoperative mean absolute SE in the 18 PRK-treated eyes was 0.33 D (95% confidence interval [CI] of improvement, 0.57-1.32) and the mean uncorrected visual acuity, 0.8 (95% CI of improvement, 0.32-0.45). The final SE was within +/-0.5 D in 15 eyes (83.0%) and within +/-1.0 D in 18 eyes. Halos after PRK were unchanged in 6 patients, slightly improved in 4, and improved in 2. Photorefractive keratectomy or IOL exchange was needed in eyes with a preoperative SE between plano and +1.75 D (15/40 eyes, 38%) and not needed in eyes with a preoperative SE greater than +1.75 D (0%) (95% CI of difference, 23%-53%). CONCLUSIONS: Presbyopic lens exchange in eyes with emmetropia and low hyperopia was associated with a significantly higher percentage of secondary procedures. Photorefractive keratectomy enhancement can improve distance vision but has a limited effect on halos.

Accommodation, Ocular↗
PubMed2004

Accommodation measurements in a prepresbyopic and presbyopic population.

PURPOSE: To study the efficacy of several subjective and objective methods of accommodation measurement in normal prepresbyopic and presbyopic populations to identify appropriate methods for measuring the outcome of accommodative restorative procedures. SETTING: University of Houston, College of Optometry, Houston, Texas, USA. METHODS: Thirty-one normal subjects with a mean age of 43.7 years (range 31 to 53 years) participated. Accommodation was measured monocularly using 3 subjective approaches--the push-up test, minus lenses to blur, and a focometer--and 2 approaches measured with a Hartinger coincidence refractometer, in which accommodation was stimulated with minus lenses to blur and topical pilocarpine 6%. RESULTS: The push-up method overestimated accommodative amplitude relative to objective measures in 28 subjects. Two subjective methods, minus lenses to blur and the focometer, produced comparable results, but with lower amplitudes in younger subjects and higher amplitudes in older subjects compared with objective methods. Comparable results were obtained when accommodation was stimulated in 1 of 2 ways and measured with the Hartinger. Pilocarpine elicited stronger accommodative responses than distance blur for subjects with low accommodative amplitudes. Pilocarpine 6% produced stronger responses in subjects with light irides than in those with dark irides. CONCLUSIONS: Hartinger-measured accommodation provides more realistic measurement of accommodative amplitude than the subjective methods tested, especially in the presbyopic population. In presbyopic subjects, the subjective tests resulted in accommodative amplitudes up to 4.0 diopters greater than those measured with objective tests. Measurements of accommodative amplitude are best achieved with objective methods to stimulate and measure accommodation.

Accommodation, Ocular↗
PubMed2004

Evaluation of a satisfied bilateral scleral expansion band patient.

PURPOSE: To measure accommodation subjectively and objectively in a satisfied bilateral scleral expansion band patient. SETTING: University of Houston, College of Optometry, Houston, Texas, USA. METHODS: One bilateral scleral expansion patient (age 50 years), 9 age-matched normal presbyopic control subjects (age range 48 to 52 years), and 1 normal control subject (age 27 years) participated. The scleral expansion patient had a complete eye examination, corneal topography, and wavefront measurements 19 months postoperatively. Accommodation was measured subjectively with the push-up technique, minus to blur, and dioptric range of clear vision. Accommodation was determined objectively by measuring the accommodative responses to negative lenses and pilocarpine 6% with a Hartinger coincidence refractometer and to real targets with a dynamic infrared optometer. RESULTS: Distance and near acuity of 20/20 was achieved with +1.00 diopter (D) in the left eye, +0.50 D in the right eye, and a near add of +2.25 D. Corneal topography and ocular aberration measurements revealed no suggestion of optical multifocality. Subjective measurements resulted in accommodative amplitudes of 1.50 to 4.00 D, and objective measurements resulted in amplitudes of 0.25 to 1.33 D. The PowerRefractor showed an accommodative response of 0.50 D to stimuli of 1.00 to 4.00 D and strong pupillary constriction with accommodative effort compared with the control. CONCLUSIONS: No increase in accommodative amplitude above normal age-matched controls was found. Patient satisfaction may have come from the high expectations this patient had for a positive surgery outcome.

Accommodation, Ocular↗
PubMed2004

Near vision restoration with refractive lens exchange and pseudoaccommodating and multifocal refractive and diffractive intraocular lenses: comparative clinical study.

PURPOSE: To evaluate near visual performance after implantation of a pseudoaccommodating intraocular lens (IOL) (Crystalens AT-45, eyeonics) or a multifocal IOL (refractive model, AMO Array; diffractive model, AcriTec TwinSet) after lens surgery. SETTINGS: Instituto Oftalmologico de Alicante, Miguel Hernandez University, Alicante, Spain. METHODS: Forty patients were included in this prospective clinical comparative study. The patients were divided into 3 groups according to the type of IOL implanted. Group 1 included 24 eyes (12 patients) implanted with the Crystalens IOL; Group 2, 32 eyes (16 patients) with the Array IOL, and Group 3, 24 eyes (12 patients) with the TwinSet IOL. Bilateral phacoemulsification and IOL implantation were performed in all patients, and the follow-up was 1 year. The postoperative main visual outcome evaluations were uncorrected and best corrected distance and near visual acuities, mean add for near, and best distance-corrected near acuity. RESULTS: In Group 1, the mean uncorrected near acuity was 20/40 preoperatively and 20/25 after 1 year. The mean preoperative best distance-corrected near acuity was 20/32 and 20/25 after 1 year. In Group 2, the mean uncorrected near acuity was 20/40 and 20/25, respectively. The mean preoperative best distance-corrected near acuity was 20/32 and 20/25 after 1 year. In Group 3, the mean uncorrected near acuity was 20/63 preoperatively; after 1 year, it was approximately 20/25. The mean best distance-corrected near acuity was 20/50 and 20/25, respectively. A neodymium:YAG laser capsulotomy was performed for posterior capsule opacification when required, with no change in the refractive outcome. CONCLUSIONS: Implantation of multifocal and pseudoaccommodating IOLs provides adequate near vision restoration. The TwinSet IOL provided faster recovery of near vision than the other 2 IOLs. The Crystalens IOL provided less postoperative visual phenomena with favorable near vision. The Array IOL achieved the most comfortable distance and near vision.

Accommodation, Ocular↗
PubMed2006

The NuLens accommodating intraocular lens.

The NuLens intraocular lens (IOL) uses a new optomechanical concept to generate a wide range of dioptric power from minimal movements of the ciliary apparatus during accommodative effort. Basic study of the concept of optomechanics in the primate eye led to successful construction and implantation of functioning IOL prototypes.

Accommodation, Ocular↗
PubMed2006

Single optic accommodative intraocular lenses.

Currently, two single optic accommodative intraocular lenses are available for implantation. Both designs rely on the interaction of the ciliary muscle with the zonule and capsule to induce axial movement of the optic. This article reviews the historical development, laboratory data, and clinical findings relating to these interesting devices.

Accommodation, Ocular↗
PubMed2006

Sarfarazi dual optic accommodative intraocular lens.

The Sarfarazi accommodative intraocular lens, currently in clinical studies, is a single continuous silicon accommodative lens with dual optics and three haptics that mimic the action of the natural lens by using the contraction and relaxation of ciliary muscles. The lenses have been implanted in the eyes of patients. There have been no surgical or patient complications related to the lens, and its safety has been clearly demonstrated. Patient acceptance of the lens is excellent. Clinical enrollment will continue to expand.

Accommodation, Ocular↗
PubMed2005

The optics of occupational progressive lenses.

BACKGROUND: Occupational progressive lenses (OPLs) utilize progressive power optics and are designed primarily to meet near and intermediate viewing needs such as working at a computer workstation for presbyopic patients. OPLs are fabricated to have the prescribed near power in the lower part of the lens and the power in the upper portion of the lens is determined by the amount of power "degression" (decrease in plus power) relative to the near power. Independent measurements of the optical characteristics of these lenses have not been reported previously. METHODS: Manufacturers of 7 different OPL designs provided sample lenses for a patient with +2.50 D add that were measured with a Rotlex Class Plus lens analyzer (Rotlex Inc., Israel). Power measurements were normalized to the location specified by the manufacturer, and the vertical location of each lens was normalized to pupil center based on manufacturer fitting guidelines. RESULTS: Large optical differences exist among the OPL designs. The results show clear differences between the designs in terms of the add powers, their vertical location, and zone width. The size and location of the near, near-intermediate, far-intermediate, and far viewing zones were determined. CONCLUSIONS: The literature and clinical experience support that OPLs are successful at meeting the computer, general office, and other intermediate viewing distance needs of many patients. However, because of the large differences in the several OPL designs, patient success can likely be enhanced by selecting the design that best suits his or her viewing needs.

Computer Terminals↗
PubMed2005

Visual illusions? Beliefs and behaviours of presbyope clients in optometric practice.

Many clients in optometry practice have reported that they do not receive sufficient information from practitioners to make informed purchasing decisions for corrective spectacles. The aim of this study was to identify participants' attitudes and beliefs towards visiting an optician and purchasing spectacles, to compare clients' and practitioners' perceptions of purchasing decisions, and to examine clients' preferences for information and decision making. One hundred and fifty-eight presbyopes completed a questionnaire to examine attitudes and behaviours regarding visiting an optician. Thirty-four practitioners completed a questionnaire examining the purchasing recommendations they make to clients, and their perceptions of clients' purchasing decisions and information needs. Participants reported positive attitudes towards visiting an optician but required more information about their eyesight and about purchasing options. A discrepancy was found between client and practitioner perceptions of purchasing decisions and of involvement in the decision making process. Practitioners overestimated the importance of price to clients and underestimated the importance of their own recommendations on purchasing decisions. The findings of this study could be used to guide practitioners in their provision of information to clients.

Attitude of Health Personnel↗
PubMed2005

Change in shape of the aging human crystalline lens with accommodation.

The objective was to measure the change in shape of the aging human crystalline eye lens in vivo during accommodation. Scheimpflug images were made of 65 subjects between 16 and 51 years of age, who were able to accommodate at least 1D. The Scheimpflug images were corrected for distortion due to the geometry of the camera and the refraction of the cornea and anterior lens surface, which is necessary to determine the real shape of the lens. To ensure accurate correction for the refraction of the anterior lens surface, the refractive index of the crystalline lens must be determined. Therefore, axial length was also measured, which made it possible to calculate the equivalent refractive index of the lens and possible changes in this index during accommodation. The results show that during accommodation there is a decrease in both the anterior and the posterior radius of the lens, although the change in mm per diopter of the latter is much smaller. The increase in lens thickness with accommodation is higher than the decrease in the anterior chamber depth, indicating that the posterior lens surface moves backwards with accommodation. During accommodation the anterior lens surface becomes more hyperbolic. Furthermore, an increase in the equivalent refractive index during accommodation was determined.

Accommodation, Ocular↗
PubMed2004

A pulse-step model of accommodation dynamics in the aging eye.

We have developed a dynamic model of accommodation that combines independent phasic-velocity and tonic-position neural signals to control position, velocity and acceleration properties of accommodative step responses. Phasic and tonic signals were obtained from neural integration of a fixed-height acceleration-pulse and variable-height velocity-step respectively to control independent acceleration and velocity properties of the step response. Duration and amplitude of the acceleration-pulse are increased with age to compensate for age-related increases of visco-elastic properties of the lens to maintain youthful velocity. The model illustrates a neural control strategy that is similar to the classical neural control model of step changes by the saccadic and vergence systems.

Accommodation, Ocular↗