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PubMed1986

Forced vergence fixation disparity curves in presbyopia.

Forced vergence fixation disparity curves were measured at distance and near on an asymptomatic presbyopic adult population (average age 62.7 +/- 7.0 years, range 51 to 79). Approximately 42% of the 62-subject sample had the same curve types at distance and near (type I-38.4%; type II-3.5%). Different curve types were found in 58.1% of the sample. Detailed breakdown of the curve types is provided. The results are compared with findings published previously on an asymptomatic prepresbyopic sample of the same size. The necessity to establish normative data for fixation disparity curves at distance and near for different vergence states, age groups, and symptomatic subjects is stressed.

Aged↗
PubMed1989

Correction of presbyopia with contact lenses: comparative success rates with three systems.

In a study designed to compare subjective success rates of three presbyopic contact lens systems, 200 presbyopes were fitted with monovision (MV), a pair of concentric center-near lenses (CN pair), or a combination of center-near/center-distance concentric lenses (CNCD). Overall, 112 subjects (56% of those fitted) successfully wore at least one lens system for a minimum of 3 months. MV was the most successful system (67% success); disrupted stereopsis was not a significant reason for failure with this system. The lower success rates with the two concentric bifocal systems (CN pair 42%, CNCD 37%) could be attributed to the greater visual compromise required with these lenses.

Adult↗
PubMed1996

Validity of surveys reporting myopia, astigmatism, and presbyopia.

Validation of surveys is an important step in establishing the usefulness of questionnaires for gathering information in clinical studies. Often in large studies of refractive error, it is not possible to examine and refract all subjects and their relatives. Therefore, we used 3 methods to evaluate 112 consecutive clinic patients' abilities to report myopia through a survey: (1) The Lay Terms Method asks: "are you nearsighted?"; (2) The Direct Method asks: "are you myopic?"; and (3) The Indirect Method uses a series of questions about the use of eyeglasses and age at first dispensing. Patient responses to the survey before examination were compared to subjective refraction findings at the completion of the eye examination. The Lay Terms Method had the highest sensitivity (0.98) but poor specificity (0.48), and the Direct Method yielded the highest specificity (0.83) but poor sensitivity (0.54). The rate of nonresponse ("don't know") was high (25.9 and 46.4% for the Lay Term and Direct Methods, respectively). The Indirect Method gave both high sensitivity and specificity (0.76 and 0.74, respectively), and only an 8.9% don't know response rate. The survey method that reports the presence or absence of myopia with the best balance of sensitivity and specificity and fewest don't know responses is the Indirect Method, suggesting it is the most suitable of our three approaches for use in clinical studies.

Adolescent↗
PubMed2004

Treatment of presbyopia with conductive keratoplasty: six-month results of the 1-year United States FDA clinical trial.

PURPOSE: To provide 6-month results of a 1-year clinical trial evaluating conductive keratoplasty (CK) for the treatment of presbyopic symptoms in emmetropic and hyperopic eyes. METHODS: A total of 143 patients with presbyopic symptoms were enrolled in this 1-year United States FDA clinical trial and treated to improve near vision in 1 eye (unilateral treatment). In addition, 33 fellow eyes were treated to improve distance vision (bilateral treatment). For near vision correction, the target refraction was up to -2.0 D in the nondominant eye, and for distance vision correction, 0.0 D. Enrolled patients had a preoperative spherical equivalent of plano to +2.00 D, no more than 0.75 D of refractive astigmatism, and were 40 years of age or older. No retreatments were performed. RESULTS: Of the eyes treated for near, 77% had uncorrected near vision of J3 or better at 6 months postoperatively. A total of 85% of all patients had binocular distance UCVA of 20/25 or better along with J3 or better near, a combination that represents functional acuity for a presbyope. Sixty-six percent of eyes treated for near had a manifest refractive spherical equivalent (MRSE) within +/- 0.50 D of intended at 6 months. In 89% of eyes, the MRSE changed 0.05 D or less between 3 and 6 months postoperatively. After month 1, the incidence of variables associated with safety was 1% or lower. Seventy-six percent were very satisfied or satisfied with their procedure. CONCLUSIONS: CK appears to be very safe and effective in producing functional visual acuity in presbyopic eyes up to 6 months following the procedure. Patient satisfaction with the procedure is similar to that of monovision LASIK.

Accommodation, Ocular↗
PubMed2006

Potential effect on the retinoscopic reflex of scleral expansion surgery for presbyopia.

PURPOSE: In this initial study, we model the impact of crystalline lens movement and tilt, which we postulate are a potential consequence of scleral expansion surgery (SES). We demonstrate the possibility that these lead to an improvement in near vision with no concurrent restoration of lens accommodative function. With the implantation of scleral expansion bands (SEB), Schachar predicts an increase in the amplitude of accommodation not observed objectively. We postulate that the SEB implants cause the crystalline lens to be shifted forward and become misaligned. Using mathematical models of the optics of the human eye, we assess the effects of our postulate on the power of the eye, the depth of field, optical aberrations, and the appearance of the horizontal retinoscopic reflex. METHODS: Using anatomically based models of the human eye, the postulated effects of SES are theoretically modeled and optically analyzed in Code V for unintentional lens anterior movement, tilts, and decentrations of up to 1 mm, +/- 3 degrees , and +/- 0.3mm, respectively. The transverse aberrations are calculated before and after SES. Because it has been reported that the appearance of the retinoscopic reflex is consistent with the presence of excess aberrations, we also predict the appearance of the one-dimensional retinoscopic reflex for our models. The change in refractive error is also determined. RESULTS.: Unintentional lens shift, tilt, and decentration, as might occur as a result of SES surgery, would result in an increase in the total power of the eye along with an increase in asymmetric aberrations and little change in symmetric aberrations. The calculated appearances of the retinoscopic reflexes pre- and postsurgery are consistent with observations in the literature. CONCLUSIONS: Scleral expansion surgery could produce an improvement in near vision through an unintentional anterior displacement of the crystalline lens in combination with excess tilts and decentrations rather than as a result of a restoration of lens accommodation. There is a need for measurements and further analysis of the optical and visual properties of SES patients postsurgery.

Accommodation, Ocular↗
PubMed1973

Presbyopia and the changes with age in the human crystalline lens.

1. A method of determining the distribution of capsular moulding pressure is described. This includes:(a) measuring the decrease in polar depth of the lens from photographed lens profiles before and after the capsule has been cut around the entire equator of the lens,(b) measuring the elastic properties of the lens substance by subjecting the lens to known centrifugal forces and photographing the polar strain so produced.2. A method of determining the relationship between capsular and lenticular strain is described. This includes (a) measuring the elastic properties of the capsule (b) measuring the elastic properties of the lens substance and (c) measuring the profiles of the photographed lens. The ratio of the strain of lens substance to capsule is expressed as a dimensionless parameter, the lens number.3. The decrease in the amplitude of accommodation with increasing age is proportional to the lens number divided by the square of the radius of the accommodated lens, assuming that the movement of the capsulozonular attachments of the lens remains unimpaired in the ageing eye.4. Ageing changes in the human crystalline lens are sufficient to account for a total loss of accommodation by the age of 61 years.

Accommodation, Ocular↗
PubMed1973

Presbyopia and the water content of the human crystalline lens.

1. The water content of the human crystallaline lens nucleus is 63.4% S.D. +/- 2.9%, and cortex 68.6% S.D. +/- 4.3%.2. Neither the total water content of the cortex, nor that of the nucleus show any significant changes with age, so ;sclerosis' of the lens due to loss of water is not a cause of presbyopia.3. The initial loss of water from the nucleus of the lens substance obtained by drying in vacuo at 20 degrees C for 2 hr is related to age (P = 0.05) and deformability (0.02 > P > 0.01).4. The lens fibres of the ageing nucleus have an increased resistance to deformation associated with a decrease in initial water loss. These characteristics can be explained by a common physical property of the fibres, namely increased adhesion to each other as the lens nucleus ages. The newly formed cortical fibres do not appear to show these changes.

Adolescent↗
PubMed1991

Prandial presbyopia: the muffin man.

Transient blurring of near vision can be due to a variety of causes. We report the case of a 35-year-old man with a 10-year history of blurring of near vision that begins 30 to 45 seconds after he starts to eat and that lasts until 10 to 15 minutes after he stops eating. Magnetic resonance imaging and computed tomography of the brain and orbits did not reveal any abnormality, and stimulation of individual cranial nerves did not result in a loss of near vision. Retinoscopic refraction revealed the loss of 1.5 dioptres of accommodative power in each eye one minute after he began to eat. To the best of our knowledge such blurring of vision at near, immediately after initiating a meal, has not been previously reported. The neuroanatomy of the accommodation and of the gustatory pathways are discussed, as they may relate to this patient's visual complaint.

Accommodation, Ocular↗
PubMedDate not supplied

[Correction of presbyopia in pseudophakic patients under 60 years of age].

Objective of the study was to show the mean values of correction for near vision and to discuss the presbyopic correction in pseudophakic patients. Setting was the Eye department where authors work. Inclusion criteria for 55 patients were native or corrected distant vision of 0.8-1.0 on Snellen's chart; 0,6 on Jagger's chart for near vision; round pupil and good position of the implant. Biometry of the anterior chamber depth with Alcon biophysics during distant and near vision was performed in our study. "Hi square" test was carried out and it was concluded that patients younger than 59 years (41 eyes) had median correction of +2.0 dsph, while patients older than 60 years (36 eyes) had correction of +3.0 dsph, but it was not statistically significant. There was no statistically significant difference of the correction between pseudophakic (41) and phakic (19) eyes in patients younger than 59 years. The anterior movement of the IOL was 0.18 mm in the younger group and 0.15 mm in the older group. With good IOL movement and new materials which could have changeable refractive power, the problem of pseudophakic correction for near vision might be solved.

Accommodation, Ocular↗