SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
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.
PURPOSE: Although a posterior chamber phakic intraocular lens provides effective refractive correction of high myopia and hyperopia, mechanical contact between the implantable contact lens (ICL) and the crystalline lens and inadequate aqueous circulation in the prelenticular space could cause subcapsular opacification. To assess whether and to what extent such mechanical contact occurs, changes in the distance between the STAAR Collamer ICL and the crystalline lens under various conditions were investigated. DESIGN: Open pilot study. PARTICIPANTS: Thirteen eyes of 11 myopic and 2 hyperopic patients with a mean age of 38 years (range, 19-53 years) were examined at least 6 months after ICL implantation. METHODS: A noninvasive, high-resolution biometry technique, partial coherence interferometry, was used to measure distance changes between the ICL and the crystalline lens during subjective accommodation, after instillation of pilocarpine, and under changing light conditions. MAIN OUTCOME MEASURES: Mean distance changes from the posterior corneal surface to the ICL, from the posterior corneal surface to the anterior surface of the crystalline lens, and the distance between the ICL and the crystalline lens. RESULTS: In the nonaccommodated state, the mean distance between the ICL and the crystalline lens was 457 microm (range, 123-924 microm). During subjective accommodation, a significant (P<0.01) decrease and, after topical application of pilocarpine, a nonsignificant (P=0.35) decrease of anterior chamber depth was accompanied by a nonsignificant (P = 0.71) reduction of the ICL-crystalline lens distance. Under photopic conditions, a significant mean reduction (P<0.01) of the ICL-crystalline lens distance of -28 microm (range, -16 to -188 microm) was observed. CONCLUSIONS: Partial coherence interferometry biometry enabled noninvasive high-precision investigation of ICL dynamics. No significant changes between the ICL and the crystalline lens were detected during subjective accommodation and after application of pilocarpine. However, under photopic conditions, with constriction of the pupil, the distance between the ICL and the crystalline lens was significantly reduced. This mechanism might cause inadequate aqueous circulation in the prelenticular space and might be one of the causes of subcapsular opacification in some of the eyes after ICL implantation.
OBJECTIVE: To evaluate the clinical results of implantation of the new 1CU accommodative intraocular lens (IOL) in cataract patients and to compare results with those of conventional IOLs. DESIGN: Nonrandomized comparative trial. PARTICIPANTS: Twenty eyes of 20 patients (mean age = 65.8+/-13.3 years) in the 1CU group and 20 eyes of 20 patients (mean age = 67.4+/-11.6 years) in the control group. METHODS: All patients underwent phacoemulsification and IOL implantation. The 1CU accommodative lens was used in 20 eyes, and conventional IOLs (polymethyl methacrylate, hydrophilic or hydrophobic acrylate) were used in the control group. Patients were observed prospectively, and 6-month data were analyzed. MAIN OUTCOME MEASURES: Accommodative ranges determined by 3 different methods (near point, defocusing, and retinoscopy). Secondary outcome measures were (1) increase of anterior chamber depth after topical application of 1% cyclopentolate eyedrops and (2) distance-corrected near visual acuity with Birkhäuser reading charts at 35 cm. RESULTS: We observed a higher accommodative range with all 3 methods (mean = 1.83+/-0.49 vs. 1.16+/-0.27 diopters [D] [near point], 1.85+/-0.43 vs. 0.64+/-0.21 D [defocusing], and 0.98+/-0.55 vs. 0.17+/-0.22 D [retinoscopy]), a larger increase of anterior chamber depth after cyclopentolate eyedrops (mean = 0.42+/-0.18 vs. 0.11+/-0.06 mm), and better distance-corrected near visual acuity (median = 0.4 vs. 0.2) in the 1CU group relative to the control group. All differences between the 2 groups were statistically highly significant (P<0.001). CONCLUSIONS: In the present study, the 1CU accommodative IOL showed increased accommodative range and better near visual acuity than a control group with conventional IOLs. Further research is necessary to confirm these results in masked, randomized, prospective studies and to confirm further the accommodative power of this group of new IOLs.
PURPOSE: To measure the axial movement of an accommodating intraocular lens (IOL) induced by ciliary muscle contraction after application of pilocarpine. DESIGN: Randomized, controlled, patient- and examiner-masked trial with intrapatient comparison. PARTICIPANTS AND CONTROLS: One hundred ten eyes of 55 patients with age-related bilateral cataract. METHODS: This study was divided into 3 parts. In the first, the accommodating IOL (1CU) was compared with a 3-piece open-loop acrylic IOL that served as the control. In the second, to assess the effect of capsule fibrosis on the potential accommodating performance of the accommodating IOL, extensive polishing of the anterior capsule with a slit cannula was compared with standard surgery. In the third, the effect of a posterior capsulorhexis was compared with that of standard surgery. Anterior chamber depth (ACD) was assessed with partial coherence interferometry, measured before and after topical application of pilocarpine 2%, and near visual acuity (VA) was evaluated 3 months after surgery. MAIN OUTCOME MEASURE: Pilocarpine-induced change in ACD. RESULTS: The accommodating IOL showed a forward movement under pilocarpine with a median amplitude of movement of -314 microm (95% confidence interval [CI]: -148 to -592), compared with the backward movement of 63 microm (95% CI: 161 to -41) for the open-loop control IOL (P = 0.001). Capsule polishing and a posterior capsulorhexis had no effect on IOL movement with the accommodating IOL. The median near VA with distance correction was 20/60. CONCLUSION: Pilocarpine induced a small but significant forward movement of the accommodating IOL. However, the amount of movement was calculated to result in a refractive change of <0.5 diopters (D) in most patients, reaching 1 D or slightly more in only single cases, with a large variability of movement. Neither polishing of the capsule bag nor a posterior capsulorhexis could enhance the accommodative ability.
PURPOSE: To measure the radii of curvature of postmortem, whole, encapsulated human crystalline lenses, free of all zonular attachments, and to calculate their corresponding optical powers. DESIGN: Experimental study. PARTICIPANTS: Thirty human crystalline lenses from donors with a mean age of 33.6+/-14.4 years. METHODS: Intact clear human crystalline lenses were obtained within an average of 21 hours of death. The lenses were removed from the eye by the contributing eye bank and shipped in Optisol-GS, a physiologic preservative storage medium. These lenses, with intact capsules, were freed of all zonular attachments. The lenses were stored at 7 degrees C and were maintained in the same storage medium during the period that they were held for evaluation. Using a portable Keratron Scout corneal topographer (Eyequip, Ponte Vedra Beach, FL) fixed to an optical bench, the radii of curvatures of the anterior and posterior surfaces of the crystalline lens were measured daily for 10 days after receipt of the tissue. The capsules of the crystalline lenses remained intact, and the lenses were clear throughout the study. Measurements were made at room temperature after removing the lens from storage. Eight repetitions of the topography were made from each surface on each day to determine the accuracy and stability of the measurement. Profile photographs were taken daily to establish the central crystalline lens thickness. The corresponding optical power of each physiologically maintained crystalline lens was calculated. MAIN OUTCOME MEASURES: The main outcome measures were the central anterior radius of curvature, the central posterior radius of curvature, the central thickness of each crystalline lens, and the amount of change in these parameters over 10 days. RESULTS: The means +/- standard deviations of the central anterior and posterior radii of curvatures of the 30 adult lenses were 10.5+/-0.6 mm and 7.1+/-1.0 mm, respectively. The mean +/- standard deviation of the central thickness, as measured from profile photographs, was 3.9+/-0.5 mm. These mean measurements remained stable for up to 5 days after receipt of the tissue. The mean and standard deviation of the calculated optical power of these postmortem, physiologically maintained, intact human crystalline lenses from donors with a mean age of 33.6 years was 19.8+/-1.7 diopters. CONCLUSIONS: Lenses free of zonular tension are at an optical power that would be associated with optimal distance acuity.
PURPOSE: Most trials that study the lens movement of accommodative intraocular lens (IOLs) use pilocarpine to stimulate ciliary muscle contraction. The aim of this study is to assess in vivo whether a more physiologic, stimulus-driven accommodation is comparable to pilocarpine-induced IOL movement. DESIGN: Controlled patient- and examiner-masked clinical trial. PARTICIPANTS: The study population included 38 eyes with accommodative IOL implants (1CU) and a control group of 28 eyes with conventional open-loop IOLs. METHODS: A high-precision biometry technique, partial coherence interferometry, was used to measure IOL position. Anterior chamber depth was measured during physiologic (near point) and pharmacological (pilocarpine 2%) stimulation. In a subgroup of 14 1CU eyes, IOL position was determined repeatedly within 90 minutes after pilocarpine administration. A different subgroup was investigated as to the effect of cyclopentolate on IOL position. Best-corrected distance visual acuity (VA), best-corrected near VA, and distance-corrected near VA (DCNVA) were assessed using logarithm of the minimum angle of resolution charts. MAIN OUTCOME MEASURES: Anterior chamber depth change under pilocarpine and near-point-driven accommodation. RESULTS: Near-point accommodation did not induce movement of either the accommodating 1CU or the control IOLs. Pilocarpine induced a 201+/-0.137-mm anterior movement of the 1CU IOL (P<0.001), compared with no movement within the control IOL groups (P>0.05). There was no significant (P>0.05) difference in DCNVA between the accommodative and open-loop IOLs. No correlation between near point- or pilocarpine-stimulated IOL movement and DCNVA was found. Concerning the time course of movement after pilocarpine administration, most of the 1CU IOLs showed some movement 30 minutes after application. Cyclopentolate-induced ciliary muscle relaxation caused a posterior IOL movement, as compared with the relaxed state, when focusing on a distant target. CONCLUSION: Pilocarpine-induced ciliary muscle contraction seems to overestimate IOL movement relative to a monocular near-driven stimulus. Therefore, concerning IOL movement, pilocarpine may act as a superstimulus and may not adequately simulate daily life performance of accommodative IOLs. However, it may be helpful to evaluate the maximum potential of an accommodating IOL.
PURPOSE: To investigate the effect of periocular warming on accommodation amplitude and near vision after prolonged near work in visual display terminal (VDT) workers in an office setting. DESIGN: Prospective interventional observational case series. PARTICIPANTS: Ten healthy Japanese male volunteers (mean age, 39.3+/-2 years [range, 36-43]) with a best distance corrected visual acuity (VA) of >20/20 who performed near work for 7 hours were included in the study. MAIN OUTCOME MEASURES: The differences of subjective and objective accommodations, near acuity, and pupil diameters were compared and studied in 2 experimental settings with and without periocular warming. METHODS: Two experiments were performed on each subject on 2 different days. In one experiment, the subjects wore an eye mask and closed their eyelids for 10 minutes after 7 hours of VDT work (lid closure [LC] group). In the other experiment, the subjects applied warming sheets (WSs) to their eyelids and the periocular region and wore masks for 10 minutes again after 7 hours of VDT work (WS group). Visual display terminal work was performed under the same settings on both days. Subjective and objective accommodations, near vision, and pupil diameters were measured immediately before and immediately after the resting or warming procedure and again 90 minutes after the resting or warming procedures. RESULTS: Fifty percent of eyes had an increase in the accommodation amplitude of at least 0.5 diopters immediately after application of the WSs. Forty percent of eyes still maintained the accommodation amplitude level at 90 minutes. The mean near logarithm of the minimum angle of resolution VA immediately after application of WSs and at 90 minutes significantly improved relative to the near acuity values after simple eyelid closure. CONCLUSION: Periocular warming was found to be associated with increases in subjective and objective accommodations, with a concomitant improvement in near VA. Periocular warming with disposable WSs is a simple and effective method of increasing near work-related ergonomy.
Explore the source record for details and available documents.
PURPOSE: To examine the effects of ametropia (spherocylindrical), corneal curvature, target anterior chamber depth (ACD), misplacement, and some design features on the performance of positional pseudoaccommodative intraocular lenses (PPAIOLs). DESIGN: Theoretical investigation based on computer models to determine the practical limitations of PPAIOLs. METHODS: Using a suitable model eye featuring gradient index optics within the cornea, the PPAIOL curvatures were calculated for axial ametropia ranging from -10 diopters (D) to +10 D, where the IOL was located at an ACD of 4.05 mm. The change in refraction (y) of the hypothetical pseudophakic eye was calculated for each millimeter of forward movement (x) of the PPAIOL up to 1 mm from the pole of the corneal back surface. The computations were repeated for a range of hypothetical PPAIOL refractive indices (1.49-1.70), ACDs, equiconvex and meniscus (back surface radius, -10 mm and -25 mm), corneal astigmatism (-1 D to -5 D), and radii (after corneal refractive surgery). MAIN OUTCOME MEASURES: Diopter/millimeter values represent the gradient of the relationship between x and y. Mathematical models describe the association between the diopter/millimeter gradient and key clinical dependent variables. RESULTS: (1) For a polymethyl methacrylate (refractive index, 1.49) PPAIOL of equiconvex design and 4.05-mm ACD, the predicted diopter/millimeter value is a function of ametropia (a), where diopter/millimeter = 1.666+0.136a+0.0018a2. (2) For 6-mm ACD and a refractive index of 1.7, diopter/millimeter = 1.836+0.159a+0.0027a2. (3) The equiconvex design benefits hyperopic but not myopic eyes. (4) For PPAIOLs correcting >4 D of astigmatism, more than 0.5 D of residual astigmatism is present at near after 1 mm of IOL displacement. (5) In emmetropic cases, the predicted diopter/millimeter value is a function of the corneal radius (r) where diopter/millimeter = 7.376-1.162r+0.0545r2. (6) Positional pseudoaccommodative IOL misplacement does not significantly affect the accommodative ability. CONCLUSIONS: (1) Hyperopic eyes with relatively steep corneas should benefit more from the PPAIOL than myopic eyes with relatively flat corneas. (2) A full, binocular, near refraction should be performed to correct any residual spheroastigmatism in anisometropia and cases in which the PPAIOL is toric.
Explore the source record for details and available documents.
PURPOSE: To evaluate uncorrected near visual acuity (NVA), accommodation, corneal aberrations, and the optical quality of the retinal image in presbyopic eyes after photorefractive keratectomy (PRK). DESIGN: Nonrandomized comparative retrospective study. PARTICIPANTS: Ten post-PRK patients and 10 normal patients. METHODS: Twenty eyes (10 right and 10 left after PRK for myopia, minimum of 10 years after the operation; group A) were compared with 20 eyes (10 right and 10 left age- and gender-matched normal controls; group B). All subjects were over 40 years of age. MAIN OUTCOME MEASURES: With best distance correction, NVA was measured at 40 cm (Jaeger, J series), and the range of accommodation (diopters [D]) was measured subjectively (negative relative amplitude and positive relative amplitude). The modulation transfer function (MTF) and corneal aberrations such as comalike, spherical (SAs), and higher order (HOAs) were measured with a Hartmann-Shack aberrometer. From the MTF curves, the spatial frequencies corresponding to contrast values of 0.1 and 0.5 were noted. RESULTS: Mean ages (+/- standard deviations [SDs]) were 46.3 years (4.7) for group A and 47.6 years (4.9) for group B (P>0.05). Near acuity was J1 or better in 12 of 20 post-PRK and 4 of 20 control eyes. Mean accommodations (+/- SDs) were 3.2 D (1.14) for right group A eyes and 2.1 D (0.94) for right group B eyes (P = 0.0152), and 3.4 D (0.99) for left A eyes and 2.3 D (1.02) for left B eyes (P = 0.0168). Total HOA indexes (+/- SDs) were 1.449 (0.409) for right group A eyes and 0.824 (0.241) for right group B eyes (P = 0.008), and 1.464 (0.388) for left A eyes and 1.067 (0.542) for left B eyes (P = 0.0752). Pooling the data from post-PRK and control eyes, a significant correlation was found between near acuity and SA (right eyes, r = -0.535, P = 0.015; left eyes, r = -0.493, P = 0.027). Significant associations were found between accommodation, near acuity, HOA, and comalike aberration for right eyes only. Mean spatial frequencies (+/- SDs) corresponding to contrast values of 0.1 for right and left eyes were 14.96 (5.71) for right group A eyes and 22.02 (6.85) for right group B eyes (P = 0.074), and 15.11 (7.80) for left A eyes and 21.41 (9.00) for left B eyes (P = 0.271). Mean spatial frequencies (+/- SDs) corresponding to contrast values of 0.5 for right and left eyes were 2.86 (0.63) for right group A eyes and 3.21 (0.35) for right group B eyes (P = 0.596), and 2.76 (0.98) for left A eyes and 3.22 (0.27) for left B eyes (P = 0.194). CONCLUSIONS: Compared with normal eyes, in previously myopic eyes treated with first-generation PRK lasers there is a tendency for (1) the optical quality of the retinal image to be reduced at low contrast, (2) the aberrations attributed to the corneal surface to increase, and (3) both measured subjective accommodation and near acuity to be greater than expected. We postulate that the corneal aberrations induced by PRK for myopia may reduce the quality of the retinal image for distance but enhance near acuity by way of a multifocal effect that can delay the onset of age-related near vision symptoms.
Explore the source record for details and available documents.
BACKGROUND: Accommodative dysfunction and convergence insufficiency (CI) are common pediatric vision problems that have been associated with an increase in frequency and severity of vision-specific symptoms that affect children when doing schoolwork. However, the relationship between accommodative dysfunction and CI and other learning problems, such as attention deficit hyperactivity disorder (ADHD), are not well understood. The purpose of this study was to evaluate the frequency of ADHD behaviors in school-aged children with symptomatic accommodative dysfunction or CI. METHODS: Children 8 to 15 years of age with symptomatic accommodative dysfunction or CI were recruited from the teaching clinic at the Southern California College of Optometry. Children with learning disabilities or ADHD were excluded. One parent of each child completed the Conners Parent Rating Scale-Revised Short Form (CPRS-R:S). The children's scores on the CPRS-R:S were compared with the normative sample. RESULTS: Twenty-four children (9 boys and 15 girls) participated in the study with a mean age of 10.93 years (SD = 1.75). On the CPRS-R:S, cognitive problem/inattention, hyperactivity, and ADHD index were significantly different from normative values (p < or = .001 for all tests). CONCLUSIONS: The results from this preliminary study suggest that school-aged children with symptomatic accommodative dysfunction or CI have a higher frequency of behaviors related to school performance and attention as measured by the CPRS-R:S.
BACKGROUND: The use of a phoropter for measuring phorias and vergences in children is common in the optometric profession. For young children, the use of the phoropter can be confusing, making it difficult to obtain accurate measurements. Free space testing allows for direct observation of the eyes in a natural environment and is easier for children to understand the directions. The normal values for phorias and vergences used with children are derived from testing with a phoropter or free space measurements with mostly adult patients. METHODS: The Benton-IU Project was a large multidisciplinary study of factors affecting school performance conducted by the Indiana University School of Optometry and the Indiana University Department of Speech and Hearing with the cooperation of the Benton Community School Corporation (Benton County, Indiana). This project allowed the authors to obtain data on modified Thorington phorias and prism bar vergences from a nonselected group of first and fourth graders as part of an eye/vision examination. RESULTS: In this report, central tendency and variability statistics for modified Thorington and prism bar vergences are reported based on the data from the Benton-IU Study. CONCLUSION: The data presented in this report can be used by optometrists when deciding if the patient's phorias and vergences are within normal limits for children in the first through fourth grades.
BACKGROUND: Measurement of the stimulus accommodative convergence to accommodation (AC/A) ratio is a standard procedure in clinical optometric practice. Typically, heterophoria is assessed at several accommodative stimulus levels, and the gradient of the vergence to accommodation function computed. A number of procedures are available for the subjective measurement of heterophoria, but it is unclear whether the use of different vergence measurement techniques will alter the obtained AC/A value. Accordingly, the current study compared AC/A ratios measured using 3 clinical subjective heterophoria tests, namely the von Graefe (VG), Maddox Rod (MR), and Modified Thorington (MT) procedures. METHODS: The AC/A ratio was measured in 60 visually normal subjects between 20 and 25 years of age using each of the 3 procedures listed above. The accommodative stimulus was varied by the introduction of +/-1.00 diopter (D) spherical lenses over the distance refractive correction while subjects viewed a target at a viewing distance of 40 cm. To examine the repeatability of each procedure, the AC/A ratio was measured on 2 separate occasions for each measurement technique, with the 2 sessions being separated by at least 24 hours. RESULTS: Mean values of stimulus AC/A ratio measured using the VG, MR, and MT procedures were 3.47, 2.99, and 2.46Delta/D, respectively. These differences were significant (p=0.0001). In addition, the coefficient of repeatability for the 3 techniques was 2.22, 1.99, and 1.20 Delta/D, respectively. CONCLUSIONS: Ratios obtained using the Modified Thorington technique with +/-1.00 D lenses showed the best repeatability, whereas the poorest repeatability was found with the von Graefe technique when only +1.00 D lenses were used to vary the accommodative stimulus. Accordingly, we recommend that that Modified Thorington procedure with +/-1.00 D lenses be used to quantify heterophoria during clinical measurement of the stimulus AC/A ratio.
BACKGROUND: The purpose of this study was to determine if vision training with the EYEPORT system affects vision and reading performance. (Subsequent to this study, the "E.Y.E." has been renamed "EYEPORT") METHODS: College students with normal vision (n = 31) participated in a blind, crossover study to assess within-subject and between-group effects of EYEPORT training. Half the subjects initially underwent training (10 minutes per day, 6 days a week for 3 weeks), and then crossed over to the no-train control condition (3 weeks); the other half underwent the reverse sequence. Vision and reading performance were assessed at baseline, 3 weeks, and 6 weeks. RESULTS: Multivariate analyses (Hotelling's T2) found small improvements in vergence and accommodative facility, reading performance, and stereopsis response time after EYEPORT training (P < 0.025). Enhancements in reading performance and vergence facility were still present 3 weeks after cessation of training (P < 0.001). CONCLUSIONS: The EYEPORT training system shows potential to enhance visual performance and reading ability. Studies are underway to assess its efficacy in symptomatic populations.
Archer fishes (Toxotidae) bring down aerial prey with a squirt of water from their mouth. How they aim, however, is not clear. Measurements of the angle between the squirt and the fish's body axis (the mouth angle) already yielded agreement that pointing the body plays a part in aiming, and it has been suggested that more accurate aiming would occur by means of lips and tongue. In a previous study, however, we found that the mouth angle is an individual property, with a much smaller range than reported by others. Moreover, we found that archer fishes do not possess movable lips, and that their tongue seems too short to direct the squirt. Presently, we found that the tongue cannot even reach the rostral part of the mouth cavity, that affects the squirt's direction, and that the mouth angle is an individual property remaining constant, even across a wide range of target distances. These findings suggest that aiming the body is the only way of aiming the squirt. We also found that during aiming, the body rotates around the eyeballs which remain fixed in space. The position of the eyeballs in the head (eye angle) at the moment of squirting was also found to be an individual property. However, the eye angle is less constant than the mouth angle. The systematic variance of the eye angle probably is related to the refraction effect.
Accommodation in humans refers to the ability of the lens to change shape in order to bring near objects into focus. Accommodative loss begins during childhood, with symptomatic presbyopia, or presbyopia that affects one's day to day activities, striking during midlife. While symptomatic presbyopia has traditionally been treated with reading glasses or contact lenses, a number of surgical interventions and devices are being actively developed in an attempt to restore at least some level of accommodation. This is occurring at a time when the underlying cause of presbyopia remains unknown, and even the mechanism of accommodation is occasionally debated. While Helmholtz' theory regarding the mechanism of accommodation is generally accepted with regard to broad issues, additional details continue to emerge. Age-related changes in anterior segment structures associated with accommodation have been documented, often through in vitro and/or rhesus monkey studies. A review of these findings suggests that presbyopia develops very differently in humans compared to non-human primates. Focusing on non-invasive in vivo human imaging technologies, including Scheimpflug photography and high-resolution magnetic resonance imaging (MRI), the data suggest that the human uveal tract acts as a unit in response to age-related increasing lens thickness and strongly implicates lifelong lens growth as the causal factor in the development of presbyopia.