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PubMed2002

Racemization of aspartic acid in human proteins.

Aspartic acid racemization (AAR) represents one of the major types of non-enzymatic covalent modification that leads to an age-dependent accumulation of abnormal protein in numerous human tissues. In vivo racemization is an autonomic process during the "natural" ageing of proteins, and correlates with the age of long-lived proteins. Consequently AAR can be used as molecular indicator of protein ageing as well as for the identification of permanent proteins that age with the human organism. Although long-living, structural proteins are mainly affected, AAR may be significant on a time scale also relevant to enzymes and signaling proteins. It may result in a loss of protein function due to proteolysis or due to changes in the molecular structure. In vivo racemization may also increase in pathological conditions. AAR has already been discussed as a relevant pathophysiological factor in the pathogenesis of diseases of old age such as atherosclerosis, lung emphysema, presbyopia, cataract, degenerative diseases of cartilage and cerebral age-related dysfunctions. Although the details of the biological consequences of AAR have to be further elucidated, it is evident that AAR plays a role in the molecular biology of ageing.

Aging↗
PubMed2006

Laser eye surgery for refractive errors.

Several laser and non-laser refractive surgical procedures have been used to modify the shape of the cornea and correct myopia, hyperopia, astigmatism, and presbyopia. Introduction of the excimer laser to reshape the cornea has resulted in remarkable developments in the correction of these refractive errors. Combined with other advanced ophthalmological instruments, laser refractive eye surgery has resulted in a substantial rise in the safety, efficacy, and predictability of surgical outcomes. Despite these advances, certain limitations and complications persist. In this review, we describe the history, preoperative assessment, surgical techniques, outcomes, and complications of laser refractive surgery.

Astigmatism↗
PubMed2000

One-year results of laser vision correction for low to moderate hyperopia.

OBJECTIVE: To assess the efficacy and safety of hyperopic laser vision correction using a refined ablation architecture and the VISX STAR Excimer Laser. DESIGN: Prospective noncomparative case series. PARTICIPANTS: Fifty-two eyes with hyperopia from +1 to +6 diopters (D) spherical equivalent (SE) with or without cylinder < or =1.5 D based on cycloplegic refraction. Hyperopia was primary or caused by prior overcorrection of myopia. INTERVENTION: Hyperopic laser vision correction using a 9 mm/5 mm ablation profile and a pulse rate of 10 Hz. We prescribed ciprofloxacin and fluorometholone four times a day for 1 week. MAIN OUTCOME MEASURES: SE; uncorrected visual acuity (UCVA); predictability within +/- 0.5 D, +/- 1.0 D, and +/- 2.0 D of target refraction (emmetropia); loss of best-corrected visual acuity (BCVA); haze, and all complications at 1, 3, 6, and 12 months. RESULTS: We treated 52 eyes (mean preoperative SE; +3.03 D). Forty-one eyes (78.8%) had primary hyperopia. At 3, 6, and 12 months, 66%, 67%, and 79% of all eyes had refraction within +/-0.5 D of emmetropia. At these same intervals, 83%, 88%, and 79% were within +/-1.0 D of emmetropia. At 12 months, all eyes were within +/-2.0 D. At 3 months, 85.4% of eyes had UCVA of 20/40 or better, with 95.3% achieving 20/40 or better at 6 months. At 1 year, all eyes (n = 19) had gained from 1 to 8 Snellen lines of UCVA, with most (n = 16) gaining between 3 and 7 lines. At 12 months, all eyes maintained preoperative BCVA or gained 1 to 4 lines. There was some early, transient haze < or = grade 1.5. There were no corneal infiltrates, decentered ablations, or infections. CONCLUSIONS: These data suggest that the 9 mm/5 mm hyperopic ablation profile of the VISX STAR can produce accurate corrections without significant, progressive regression. Refractive stability was achieved 3 months after surgery. We did not observe any differences in outcomes between eyes treated for primary hyperopia and eyes treated for prior myopic overcorrections. We believe the quicker ablation time (10 Hz pulse rate) helped patients maintain fixation and reduced the risk of decentration. There was a high degree of satisfaction among all patients, especially those with presbyopia.

Adult↗
PubMed1999

The mechanism of accommodation in primates.

OBJECTIVE: To study the accommodative mechanism in primates using monkeys, in light of a recently proposed novel accommodative mechanism in primates and a concomitant controversial surgical procedure for the reversal of presbyopia, DESIGN: Experimental study. METHODS: Accommodation was induced by stimulation of an electrode surgically implanted in the midbrain and by topical ocular application of muscarinic agonists. Pharmacologic disaccommodation was achieved by topical application of a muscarinic antagonist. Movements of the lens equator and the ciliary body were imaged during accommodation and disaccommodation using ultrasound biomicroscopy and goniovideography, and the images were analyzed to determine the direction and the extent of the movements. RESULTS: Despite the systematic eye movements occurring with electrical stimulation and the nonsystematic eye movements occurring with pharmacologic stimulation, in all instances the ciliary body and the lens equator moved away from the sclera during accommodation. CONCLUSIONS: Movement of the accommodative structures is consistent with the classic mechanism of accommodation described by Helmholtz, and contrary to that recently proposed by Schachar.

Accommodation, Ocular↗
PubMed2000

Dysphotopsia in phakic and pseudophakic patients: incidence and relation to intraocular lens type(2).

PURPOSE: To determine the relationship between various intraocular lens (IOL) types and the incidence of unwanted light images. SETTING: The Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. METHODS: A telephone questionnaire was administered to 302 postoperative patients who had received 1 of 6 commonly used IOLs between January and September 1998. Patients were included only if they had uneventful cataract surgery, no additional ocular pathology, and a postoperative best corrected visual acuity of 20/25 or better. A control group of 50 patients with the diagnosis of presbyopia only also participated in the questionnaire. Patients reported on incidence of glare, light sensitivity, and unwanted images. The data were analyzed for statistically significant relationships between incidence of photopsias and IOL type. RESULTS: The AcrySof 5.5 mm, AcrySof 6.0 mm, and SI-40 groups reported significantly more unwanted images than the control group (P =.0014). The 2 AcrySof groups also reported a greater incidence of light to the side causing a central flash, and the SI-40 group, a higher incidence of glare. The control group was more likely to experience symptoms of glare than any pseudophakic group. Overall, a mean of 49% of patients reported some light-related phenomenon postoperatively. The majority in all groups reported being satisfied with their eyesight despite the light-related problems. CONCLUSIONS: A significant number of pseudophakic patients reported symptoms of dysphotopsia. Patients who received an acrylic IOL with flattened edges were at increased risk of experiencing images associated with edge reflections. The SI-40 lens group, although less than the AcrySof groups, reported a higher incidence of glare than the non-AcrySof groups; however, it also had the highest number of patients still driving at night. The phakic population commonly experienced glare reported as more severe than several of the IOL groups.

Aged↗
PubMed2003

Comparison of myopes and hyperopes after laser in situ keratomileusis monovision.

PURPOSE: To compare the results of laser in situ keratomileusis (LASIK) monovision in myopes and hyperopes. SETTING: Private practice, Little Silver, New Jersey, USA. METHODS: In this retrospective study, 391 consecutive patients older than 40 years who had LASIK between December 1999 and June 2001 were examined. All patients were asked to complete a questionnaire, and study results are based on the analysis of data from patient charts correlated with questionnaire responses. RESULTS: Visual results were excellent in both groups, with all monovision patients achieving 20/30 acuity or better in the distance eye and J2 or better acuity in the near eye. Satisfaction scores were high in all groups. Statistical analysis indicated that visual results for distance were better in myopes than in hyperopes (P =.043), enhancements were higher in monovision (P =.04) and in hyperopia (P =.08), and satisfaction was higher among myopes (P =.012) and full distance patients (P =.002). Monovision hyperopes had the most difficulty with 6 side effects (P =.00). CONCLUSION: Hyperopic monovision was a viable but more problematic solution to correcting presbyopia than myopic monovision.

Adult↗
PubMed2003

Disposable and frequent replacement contact lenses.

Disposable and frequent replacement contact lenses dominate the marketplace. They are available in a wide variety of parameters for use in refractive errors, including myopia, hyperopia, astigmatism, and presbyopia. They are convenient and affordable and lend themselves to most wearing modalities, including daily wear, flexible wear, and extended wear for up to 30 days. In addition, they have been shown to be the most trouble-free contact lens wear modality for daily wear or extended wear. They are an appropriate choice for patients who desire occasional contact lens wear and have gained wide acceptance as therapeutic bandage contact lenses. Disposable and frequent replacement lenses will remain important modalities for some time to come as the variety of contact lenses and contact lens parameters that are offered continue to expand. New contact lens varieties, such as the high-Dk silicone hydrogel lenses, will further expand the role of these contact lenses in vision correction.

Contact Lenses↗
PubMed2003

Verification of the vertex powers of varifocal rigid contact lenses.

INTRODUCTION: Increasingly aspherical optics are used in contact lens designs to produce a varifocal effect to correct presbyopia. Whilst no current ISO standard describes a method to verify these products, the vertex power needs to be verified by the manufacturer and optometrist. Visionix claim that the VC2001 instrument is able to resolve the vertex power of complex contact lenses and that it has been adopted by contact lens manufacturers as their "gold standard" method of measure. Practitioners rely on the focimeter for contact lens verification and accept that it has poorer resolution. This raises the question of whether practitioners can verify the vertex powers of varifocal contact lenses to a sufficient sensitivity. The purpose of this study is to determine whether a focimeter can differentiate between various vertex powers incorporating differing degrees of asphericity that are used in contact lens designs. METHODS: A range of varifocal contact lenses were used with single vision contact lenses as controls. Three types of focimeters were used: a manual focimeter, a projector focimeter and a computerised focimeter (standard and contact lens modes). The VC2001 assessed the vertex powers over the optical zone and was used as a reference for the focimeters. The measures from the VC2001 and the focimeters were analysed by discrepancy analysis. RESULTS: All discrepancy measures fell outside two standard deviations for either the varifocal contact lenses or the single vision contact lenses when the focimeters were compared to the VC2001. This raises the issue of whether the focimeters are measuring the same parameter as the VC2001. Only the analysis of the repeated measurements from the manual focimeter for single vision contact lenses demonstrated an acceptable measure of precision (+/-0.21, 2S.D.) with a very small degree of bias (mean difference -0.024, +/-0.02 [2S.E.]). CONCLUSION: These results suggest that the manual focimeter can measure the vertex powers for single vision contact lenses to an acceptable degree of precision. The vertex powers of varifocal lenses cannot be verified using standard practice equipment. The VC2001 has poor precision for power measurements and may not be measuring the same parameter as the focimeters and therefore questions the validity of the VC2001 as the "gold standard" for vertex power measurement.

Journal Article↗
PubMed2005

The IOL horizon: accommodative intraocular lenses.

BACKGROUND: For more than half a century, intraocular lenses have been used effectively to correct vision after cataract extraction. New developments in intraocular lens design have led to the creation of lenses that may have a significant role in the restoration of accommodation as well. PURPOSE: Accommodative lens technology is constantly evolving. Many different lens designs are currently under development. It is important for optometrists to be familiar with this technology and the various lenses being developed, as accommodative intraocular lenses stand to become the mainstay for cataract surgery, as well as for the surgical treatment of presbyopia. METHOD: The literature is reviewed in order to summarize the developments in accommodative lens technology.

Accommodation, Ocular↗
PubMed1987

Smoking and drinking discordance and health condition: Japanese identical twins reared apart and together.

A total of 543 like-sex pairs of twins (407 MZ, 136 DZ) were sent mailed questionnaires on cigarette smoking, alcohol drinking and health conditions. The observed concordance rate for alcohol drinking was significantly higher than expected in both MZ and DZ pairs. The observed concordance rate for cigarette smoking was significantly higher than expected in the MZ, but not the DZ pairs. The observed rate of intrapair concordance for drinking was significantly higher than expected even in MZ pairs reared apart from infancy or very early childhood. Higher life satisfaction was observed more often in the higher alcohol consumers than in the lower consumers among MZ pairs discordant for alcohol drinking, while earlier onset of presbyopia was observed more often in the lower consumers. Physical symptoms, especially pains in the upper extremities, were reported more often by higher alcohol consumers than by lower consumers in the MZ pairs discordant for drinking.

Aged↗
PubMed1998

Ocular problems of young adults in rural Nigeria.

OBJECTIVES: To determine the common eye diseases as well as the prevalence and causes of blindness and visual impairment in young adult residents of rural areas of Anambra State, Nigeria. MATERIALS AND METHODS: Three rural villages in Anambra State, Nigeria were selected by simple random sampling. A structured questionnaire on demographic characteristics, symptoms and attitude to eye diseases was administered to residents aged 18-49 years. Ocular examination included visual acuity estimation, colour vision test, tonometry, refraction and ophthalmoscopy. Skin-snip was examined for microfilaria. RESULTS: The common ocular problems in the 510 young adults examined were presbyopia (33.3%), refractive errors (41.1%), allergic conjunctivitis (8.2%), pterygium (8.2%), pingueculum (5.9%) and colour vision defect (2.4%). Bilateral blindness occurred in 1.2%, uniocular blindness in 0.8% and 1.7% had visual impairment in their better eyes. Glaucoma and sequelae of congenital cataract caused bilateral blindness while visual impairment was due to refractive errors, cataract, corneal opacities and uveitis. Trauma predisposed to uniocular blindness and visual impairment. CONCLUSIONS: Eyeglasses alone would alleviate visual impairment and ensure good near vision in more than 47% of the subjects. The prevalence of blindness could be reduced through early detection of glaucoma, congenital cataract and ocular trauma.

Adult↗
PubMed1989

Pupil dilatation with tropicamide. The effects on acuity, accommodation and refraction.

The effect of pupil dilatation with tropicamide 1% on visual acuity and accommodation was assessed in 100 eyes of 52 consecutive patients attending the general ophthalmic outpatient clinic. Snellen visual acuity remained unchanged in 55 eyes and deteriorated by one line in 41 eyes. The remaining four eyes deteriorated by two lines. Tropicamide gave rise to a reduction in the amplitude of accommodation which tended to vary inversely with the age of the patient. However, all patients who wore reading glasses for presbyopia were still able to read when their pupils had been dilated.

Accommodation, Ocular↗
PubMed1993

Is cortical spoke cataract due to lens fibre breaks? The relationship between fibre folds, fibre breaks, waterclefts and spoke cataract.

Fibre folds, previously called lamellar separation of the lens, have been found by electron microscopy to be associated with fibre breaks, which are seen in vivo as the circular shades of Obazawa. This led to the present study to determine the relationship between fibre folds, fibre breaks, waterclefts and spoke cataract. All lenses with fibre folds were found to have circular shades. A few instances of circular shades without fibre folds were found, suggesting that the fibre break may be the primary pathology. It was found that circular shades occurred in association with spoke cataract only when fibre folds were also present. Thus there is no essential causal relationship between fibre breaks and spoke cataract. The occurrence of waterclefts was unrelated to the presence of the other features. The lower nasal quadrant of the lens was the most common site for the four features. The depth of spoke cataracts was found to be unrelated to the age of the patient, which makes it unlikely that accommodational stress at the time of onset of presbyopia is causative.

Age of Onset↗
PubMed2001

Changes in the static accommodation response with age.

A transverse study of the monocular, steady-state accommodation response/stimulus curves for 49 normal subjects with ages between 17 and 49 years shows that the slope of the curve reduces only slowly with age up to about 40 years and then declines rapidly as complete presbyopia is approached. Such behaviour appears to result from the accommodation system changing its characteristics with age to make optimal use of the available objective amplitude of accommodation and the depth-of-focus of the eye.

Accommodation, Ocular↗
PubMed1998

Self-assessment of the quality of vision: association of questionnaire score with objective clinical tests.

PURPOSE: To investigate the association of a quality of life-visual function questionnaire with an objective clinical test of visual function. METHODS: We have developed a questionnaire to assess self-reported visual satisfaction in ophthalmic patients suffering from chronic eye conditions causing visual impairment. The questionnaire was administered to 120 patients suffering from age-related cataract, chronic open angle glaucoma, age-related macular degeneration, branch retinal vein occlusion, and presbyopia or minor refractive defects. All the participants also underwent determination of visual acuity, contrast sensitivity, glare, and visual field. RESULTS: The questionnaire has a good reproducibility, a high internal consistency, and is able to discriminate between the different groups of patients. The total questionnaire score is significantly associated with the results of all visual function tests with the exception of glare. When entered into a multiple linear regression model, near visual acuity and contrast sensitivity are still considerably associated with the total questionnaire score. The psychological attitude of the patient towards his/her health problem is also associated with the total average score. CONCLUSIONS: Overall, the model explains 49% of the variance in the average questionnaire score.

Adult↗
PubMedDate not supplied

Enhancing information acquisition for over-the-counter medications by making better use of container surface space.

Most over-the-counter (OTC) pharmaceutical container labels are printed in very small type. Consequently, people with visual impairments (e.g., presbyopia in older adults) have difficult reading the material. Some OTC drugs are packaged in containers with easy-open caps. This design increases the surface area that could be used to enhance the labeling. In Experiment 1, older adults (M = 75.1 years, SD = 8.1) evaluated six container label variants for an actual OTC product. Besides having a multipanel main label, four containers had labels attached to the cap that displayed the most important information in large print but differed in color. Two control containers lacked a cap label; one had only a four-panel main label, and the other had only the front label. Participants ranked the containers on six dimensions (e.g., label noticeability, willingness to read). Results showed greater preference for containers with the cap labels. Experiment 2 again examined preferences but also measured information-acquisition performance after participants (M = 79 years, SD = 5.8) were briefly exposed to a realistic-appearing, but fictitious, OTC medication. Results showed greater knowledge and preference for containers with the cap labels. Experiment 2 showed that one of the cap colors (yellow) that was different from the main label was preferred over the white and orange (the same colors as on the main label), but color distinctiveness as an explanation was not fully supported because the green cap was not significantly different from the other cap labels. Implications for communicating information about OTC drugs using expanded labels are discussed.

Aged↗
PubMed2004

Prevalence of non-vision-impairing conditions in a village in Chakwal district, Punjab, Pakistan.

PURPOSE: To determine the prevalence of non-vision-impairing ocular conditions (NVIC) and estimate the number of primary eye care treatments per 1000 population per month. METHODS: A cross-sectional study in a random sample of 1670 people was done to determine the load of NVIC in a village in Chakwal district. RESULTS: The prevalence of NVIC was 30.6% (306 per 1000 population). NVIC with the exclusion of presbyopia accounted for 14.6%. The main NVIC were allergic conjunctivitis (3.7%), bacterial conjunctivitis (3.5%), pterygium/pinguicula (2.6%) and acute/chronic dacryocystitis (1%). The average Complaint Frequency (CF) per month/1000 population was 55, excluding complaints of near vision and watery eyes. CONCLUSIONS: The foundation of a comprehensive district eye care strategy in the light of VISION 2020 - the Right to Sight - remains an effective primary eye care service whose elements are treatment of NVIC, detection and referral of cataracts and refractive errors, and promotion of eye health.

Adolescent↗
PubMed2000

Mechanisms of homocysteine toxicity on connective tissues: implications for the morbidity of aging.

It is proposed that chronic moderate hyperhomocysteinemia has a causal role in a number of common diseases of late life, including occlusive vascular disease, cognitive decline, senile osteoporosis and presbyopia. These diseases are seen as clinical counterparts of the main manifestations of homocystinuria (vascular occlusions of arteries and veins, mental retardation, osteoporosis and ectopia lentis, respectively) that develop only after many years of exposure to moderately elevated homocysteine (Hcy) levels. The multisystem toxicity of Hcy is attributed to its spontaneous chemical reaction with many biologically important molecules, primarily proteins. The formation of these Hcy-adducts is dependent on time and Hcy concentration and leads to loss or diminution of function of the derivatized molecules. Irreversible homocysteinylation of long-lived proteins should lead to cumulative damage and progressive clinical manifestations. Fibrillin 1 is seen as the paradigm of extracellular connective tissue proteins that are specially susceptible to Hcy (and presumably Hcy thiolactone) attack. The prominent presence of epidermal growth factor (EGF)-like domains in fibrillin and in many other extracellular proteins of the coagulation, anticoagulation, and lipoprotein transport pathways, all of which malfunction in hyperhomocysteinemia, suggests that EGF-like domains may be preferential sites of homocysteinylation.

Aging↗