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PubMed1995

[Experience with excimer laser photorefractive keratectomy].

UNLABELLED: The correction of refractive errors based on superficial ablation of the cornea has a couple of years long history. Authors performed photorefractive laser surgery with the Aesculap Meditec MEL 60 ArF excimer laser in 221 eyes of 147 patients. The follow-up time varied between 2-24 months, average 8 months. They have treated the following groups: 1. group: 0-6.0 D; 2. group: -6.5-9.0 D; 3. group: eyes with refractive error above -9.5 D; 4. group: hypermetropic eyes; 5. group: eyes with astigmatism. RESULTS: In the 1. group the average -4.58 +/- 1.25 D refractive error decreased to -0.19 +/- 0.53 D in the follow-up time; 2. group: from -7.46 +/- 1.22 D to -0.45 +/- 0.83 D; 3. group: -13.76 +/- 5.46 D to -1.52 +/- 1.74; 4. group: +428 +/- 1.6 D to +0.91 +/- 2.41 D; 5. group; from -6.74 +/- 2.81 D sph -2.3 +/- 1.54 cyl to -0.51 +/- 1.3 D sph -0.54 +/- 1.06 D cyl. According to their experiences they conclude: the best results have been achieved in the first two groups and in eyes with astigmatism (1., 2., 5. groups). In severe myopia cases postoperative correction is usually needed, which is significantly smaller than the preoperative spherical correction. The method is able to change the refractive power of the cornea and provides an efficient alternative to the spectacles and contact lenses.

Adult↗
PubMedDate not supplied

A mathematical model for laser in situ keratomileusis and photorefractive keratectomy.

PURPOSE: The purpose of ablation refractive surgery is to remove the refractive error from the inherently asymmetric aspheric cornea. Although the technique is gaining wide acceptance and popularity, some patients are left with irregular corneas. Our objective was to develop a methodology to analyze corneal shape, reduce the shape to arcs, modify the local arc value to the desired new arc value, and render a new continuous Euclidean surface without discontinuity. METHODS: The method to reconstruct the corneal surface consists of importing scanner output elevation data points into a computer-aided design (CAD) application to form the surface model. The corneal arc measurements are derived at 5 degrees increments and centered about the Gauss point of symmetry. Each arc is manipulated to adjust the corresponding arc on the proposed corneal surface to reflect the new arc value, correcting for the refractive error. The method determines the amount of corneal tilt and ablation depth at a given diameter required for the refractive error with a smooth transition zone to the base cornea. RESULTS: The case example is a patient who began with a spherical refraction of -8.75 D and after LASIK was emmetropic, but had irregular astigmatism and 20/30 best spectacle-corrected Snellen visual acuity. The proposed mathematical model compares the achieved surface shape to the mathematically planned surface contour. An enhancement procedure to remove the LASIK-induced corneal irregularity was designed. CONCLUSION: A mathematical technique to plan myopic ablative surgery to make the corneal surface regular and symmetric is proposed.

Adult↗
PubMed2006

Change of refractive state and eye size in children of birth weight less than 1701 g.

AIMS: To determine the refractive status and ocular dimensions of a cohort of children at age 10-12 years with birth weight below 1701 g, and also the relation between the neonatal ophthalmic findings and subsequent refractive state. METHODS: 293 low birthweight children who had been examined in the neonatal period were assessed at 10-12 years of age. The examination consisted of autorefraction, keratometry, and A-scan. Results of right eyes were compared with published normative data. RESULTS: 293 of the birth cohort of 572 children consented to participate. The average mean spherical equivalent (MSE) in the low birthweight cohort was +0.691 dioptre, significantly higher than the control data (+0.30D, p = 0.02). The average change in MSE over the 10-12 year period was -1.00 dioptre (n = 256), but only 62.1% of cases showed a shift in refractive error of the appropriate magnitude and direction. The presence of any retinopathy of prematurity (ROP) increases the risk of developing anisometropia sixfold. CONCLUSIONS: Low birth weight and ROP both significantly impact the refractive state in the long term. At age 10-12 years children born preterm have an increased prevalence of all refractive errors. In low birthweight children refractive state is relatively stable over the first decade of life with a shift towards myopia of 1 dioptre.

Birth Weight↗
PubMed2002

Risk factors for self-reported visual symptoms with Intacs inserts for myopia.

OBJECTIVE: Potential risk factors and visual performance measures were evaluated for relationship to self-report of clinical visual symptoms after the refractive procedure for placement of Intacs microthin prescription inserts for myopia. DESIGN: Retrospective nonrandomized comparative study. PARTICIPANTS/INTERVENTION: Patients were participants in the U.S. Food and Drug Administration phase III KeraVision prospective clinical trials. MAIN OUTCOME MEASURES: Study participants (n = 263) were retrospectively classified into one of three outcome groups on the basis of postoperative self-reported visual symptoms and/or request for Intacs inserts removal through month 24. Differences between outcome groups in visual acuity, refractive error, corneal geometry, corneal topography, type of preoperative corrective lens wear, and demographic variables were evaluated with multivariate logistic regression. RESULTS: Clinical trial participants who had preoperative mean keratometry >45 diopters (D) (adjusted odds ratio [OR], 0.43; 95% confidence interval [CI], 0.21, 0.85, P = 0.02), manifest refractive astigmatism of 0.75 D or 1.00 D (adjusted OR, 0.52; 95% CI, 0.25, 1.08, P = 0.08), measured uncorrected visual acuity > or =2 lines better than that predicted by their respective cycloplegic refractive error (adjusted OR, 0.39; 95% CI, 0.14, 1.12, P = 0.08) and/or had worn soft contact lenses (adjusted OR, 0.58; 95% CI, 0.32, 1.04, P = 0.07) tended to be less likely to report postoperative clinical visual symptoms with Intacs inserts. Risk of clinical visual symptoms and request for Intacs inserts removal approximately doubled for each 0.50 D of additional postoperative defocus equivalent (crude OR, 1.86; 95% CI, 1.39, 2.48, P = 0.00). Controlling for postoperative defocus and important preoperative risk factors, subjects who reported significant clinical visual symptoms were more likely to have had preoperative uncorrected visual acuity that was worse than that predicted by their respective cycloplegic refractive error (adjusted OR, 1.84; 95% CI, 0.98, 3.42, P = 0.06). Risk of reporting clinical visual symptoms was increased with mesopic pupil diameter > or =6.5 mm (adjusted OR, 1.76; 95% CI, 0.96, 3.24, P = 0.07). Within the group of patients who reported postoperative clinical visual symptoms, 71 of 122 (58%) had ceased reporting them by month 24. CONCLUSIONS: Adjusting for important risk factors simultaneously, this study suggested that certain preoperative characteristics may increase or decrease the likelihood, depending on the characteristic, of refractive surgery candidates to report significant clinical visual symptoms with Intacs inserts.

Adult↗
PubMed2004

The prevalence and causes of visual impairment in Tehran: the Tehran Eye Study.

AIMS: To determine the prevalence and causes of visual impairment in Tehran, Iran, through a population based study. METHODS: In a population based, cross sectional study, 6497 Tehran citizens were sampled from 160 clusters using a stratified, random, cluster sampling strategy. The eligible people were enumerated through a door to door household survey in the selected clusters and were invited. All participants were transferred to a clinic for an extensive eye examination and interview. Visual impairment was determined using presenting and best corrected visual acuity (low vision: visual acuity of less than 6/18 to 3/60 in the better eye; blindness: visual acuity of less than 3/60 in the better eye). RESULTS: Of those sampled, 4565 (70.3%) people participated in the study. The age and sex standardised prevalences of visual impairment on the basis of best corrected and presenting visual acuity were 1.39% (95% confidence interval (CI), 1.07 to 1.71) and 2.52% (95% CI, 2.07 to 2.97), respectively. 15 people (0.28%; 95% CI, 0.14 to 0.42) were blind with corrected vision while 22 (0.39%; 95% CI, 0.23 to 0.56) were blind with presenting vision. Using the corrected and presenting vision, the prevalence of low visual impairment was 1.11% (95% CI, 0.84 to 1.39) and 2.13% (95% CI, 1.71 to 2.55), respectively. The causes of visual impairment according to the best corrected vision were cataract (36.0%), macular degeneration (20.0%), and amblyopia (10.7%). However, according to the presenting vision, uncorrected refractive errors were the most frequent primary cause (33.6%) and cataract (25.4%), macular degeneration (12.7%), and amblyopia (8.2%) were the other main causes of visual impairment in the study sample. The prevalence of visual impairment was associated with advancing age and lower education. CONCLUSION: The results indicate that the burden of visual impairment is important and, although easily preventable, uncorrected refractive errors and cataract have a major role as causes of visual impairment in this population. Results also highlight the need for visual impairment prevention programmes, with emphasis on treatment of refractive errors and cataract.

Adolescent↗
PubMed1987

Visual acuity of human infants at scotopic, mesopic and photopic luminances.

Visual acuity of 2-month-old infants and adults was measured between -2.6 and +2.7 log10 cd/m2 using standard psychophysical techniques. The acuity-vs-luminance curve was similar for infants and adults: acuity improved with increasing luminance until 0.0 log cd/m2, and was constant above that luminance. However, the infant curve was slightly shallower than the adult curve, and infant acuity was over 3.5 octaves poorer than adult acuity at all luminances. The infant acuity-vs-luminance curve was compared with adult curves measured 21 degrees and 51 degrees from fixation, and at 21 degrees with +8, +/- 3.25 and 0.0 D of experimental refractive error. The results indicated that infants' poor acuity cannot be fully explained by: refractive error, foveal immaturity, scotopic detection of stimuli, functional similarity between infant vision and adult vision in the periphery, or by an overall reduction in visual sensitivity.

Adult↗
PubMed2005

Transepithelial phototherapeutic keratectomy/photorefractive keratectomy with adjunctive mitomycin-C for complicated LASIK flaps.

PURPOSE: To evaluate the efficacy of transepithelial phototherapeutic keratectomy/photorefractive keratectomy (PTK/PRK) with prophylactic mitomycin-C for the treatment of refractive errors and maintenance of corneal clarity following flap complications in laser in situ keratomileusis (LASIK). SETTING: Outpatient tertiary care center, Chicago, Illinois, USA. METHODS: Ten eyes of 10 patients with LASIK flap complications had transepithelial PTK/PRK for correction of ametropia. Mitomycin-C 0.02% was applied to the stroma for 2 minutes following laser ablation. Postoperative uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refractions, and slitlamp examinations were obtained. RESULTS: Preoperatively, the mean UCVA was 20/400 (range 20/40 to counting fingers), the mean BSCVA was 20/28.5, and the spherical equivalent refractive errors ranged from +4.00 to -10.75 diopters (D). After the procedure, the mean UCVA was 20/28, the mean BSCVA was 20/21, and the spherical equivalent refractive errors ranged from +0.37 to -1.00 D. The mean follow-up ranged from 8 to 28 months. No patient experienced delayed reepithelialization, haze, or other signs of toxicity. CONCLUSION: Mitomycin-C can be a useful adjunctive therapy for the prevention of haze when applying surface excimer laser therapy to a cornea following LASIK flap complications.

Adult↗
PubMed2003

Risk factors for hypotony maculopathy.

PURPOSE: To determine the risk factors for hypotony maculopathy. DESIGN: Retrospective case control study. PARTICIPANTS: Two hundred twenty-eight eyes of 228 patients with hypotony from one medical center. METHODS: Chart review of patients with hypotony from January 1988 to April 2001. Hypotony was defined as intraocular pressure of 5 mmHg or less. Cases of hypotony maculopathy had retinal or choroidal folds or both within the arcades. Controls had hypotony alone. Risk factors were evaluated using multiple logistic regression analysis. MAIN OUTCOME MEASURES: Risk factors for hypotony maculopathy, including age, gender, race, refractive error, systemic illness, intraocular pressure, primary filtering surgery, use of antifibrotic agents, and presence of choroidal effusion. RESULTS: Eighty-one case eyes with hypotony maculopathy and 147 control eyes with hypotony alone were identified. The mean age of patients with hypotony maculopathy was 50.5 years +/- 18.7 compared with 70.6 years +/- 12.7 for the control patients (P < 0.001). More patients with hypotony maculopathy were male, 54.3% (44 of 81), than controls, 33.6% (49 of 147) (P = 0.004). The refractive error was -3.02 +/- 3.67 diopters (D) for phakic eyes with hypotony maculopathy (n = 31), whereas the phakic control eyes' (n = 30) refractive error was -0.61 D +/- 2.00 (P = 0.003). Choroidal effusion was found in 21% (17 of 81) of the case eyes at diagnosis and 52.4% (77 of 147) of the control eyes (P < 0.001). Race distribution and use of antifibrotics was similar for both groups. In multivariate analyses, young age, male gender, no history of diabetes, and absence of choroidal effusion predicted the development of hypotony maculopathy; in phakic eyes myopia was also a risk factor for hypotony maculopathy. CONCLUSIONS: Young age, male gender, and myopia are significant risk factors for hypotony maculopathy. A history of diabetes and the presence of choroidal effusion are associated with a decreased risk for hypotony maculopathy.

Age Factors↗
PubMed2001

Intraocular lens power calculation for lens exchange.

PURPOSE: To examine patients who had intraocular lens (IOL) exchange for large postoperative refractive errors and determine the factors that contributed to the error in IOL power calculation. SETTING: Thirteen affiliated hospitals in Japan. METHODS: This study comprised 34 cases that required IOL exchange because of large refractive errors after primary lens implantation. Patients with intraoperative complications were excluded from the study. The potential contribution of axial length, corneal refractive power, IOL manufacturer, and IOL fixation to errors in the predicted power was examined retrospectively. Axial length was calculated by the SRK/T and Holladay formulas using refraction after primary IOL implantation. RESULTS: There was no statistical difference between the corneal refractive power before and after cataract surgery. The axial lengths calculated using the SRK/T and Holladay formulas were longer than the ultrasonic axial lengths in 24 and 23 cases, respectively. Using IOLs from the same manufacturer for both primary implantation and exchange reduced the error in predicted refraction. CONCLUSION: Axial length and IOL manufacturer were important factors in predicting refraction power in eyes requiring IOL exchange.

Aged↗
PubMed1976

The refractive status of Zuni Indian children.

American Indians show a high incidence of various ocular abnormalities. In the present study, refractive error and corneal curvature were measured in 420 Zuni school children. The mean spherical refractive error varied from +0.87 D in the lower grades to -0.62 D in the upper grades. The mean corneal astigmatism was 2.21 D was varied as function of grade. corneal and refractive astigmatism were highly correlated.

Adolescent↗
PubMed2000

[Strabismus and binocular vision disorders in premature infants with retinopathy treated with cryotherapy].

PURPOSE: To assess frequency of refraction errors, abnormal eye position and binocular vision disorders in children with retinopathy treated with cryotherapy. MATERIAL AND METHODS: Subjects of the study were 67 children, aged 2-7, treated with cryotherapy for active phase retinopathy. RESULTS: The largest group consisted of children with good visual acuity (48%). Refraction error was found in 94% of the examined eyes. Hypermetropia was more common (54%) than myopia (40%). Majority of the examined children had squint, and esotropia was much more frequent (52%). The deviation in 37% of children was over 10 degrees. In the group with birth weight under 1000 grams as well as in those with birth weight 1000-1500 grams the squint occurred in 48%, and in children weighing over 1500 grams in 4.0%. Only 54% of the studied children had normal binocular vision. CONCLUSIONS: Retinopathy of prematurity is a risk factor for development of refraction errors, strabismus and amblyopia. In infants with retinopathy of prematurity treated with cryotherapy it is necessary to have vision check-ups during their early childhood years.

Child↗
PubMed1995

Choroidal and scleral mechanisms of compensation for spectacle lenses in chicks.

It is known that when hyperopic or myopic defocus is imposed on chick eyes by spectacle lenses, they rapidly compensate, becoming myopic or hyperopic respectively, by altering the depth of their vitreous chamber. Changes in two components--ocular length and choroidal thickness--underlie this rapid compensation. With monocular lens treatment, hyperopic defocus imposed by negative lenses resulted in substantially increased ocular elongation and a slight thinning of the choroid, both changes resulting in myopia; myopic defocus imposed by positive lenses resulted a dramatic increase in choroidal thickness, which pushed the retina forward toward the image plane, and a slight decrease in ocular elongation, both changes resulting in hyperopia. The refractive error after 5 days of lens wear correlated well with vitreous chamber depth, which reflected the changes in both choroidal thickness and ocular length. The degree of compensation for lenses was not affected by whether the fellow eye was covered or open. Both form-deprivation myopia and lens-induced myopia declined with age in parallel, but wearing a -15 D lens produced more myopia than did form deprivation. The spectacle lenses affected the refractive error not only of the lens-wearing eye, but also, to a much lesser degree, of the untreated fellow eye. At lens removal refractive errors were opposite in sign to the lense worn, and the subsequent changes in choroidal thickness and ocular length were also opposite to those that occurred when the lenses were in place. In this situation as well, effects of the spectacle lenses on the fellow eyes were observed. Eyes with no functional afferent connection to the brain because of either prior optic nerve section or intraocular tetrodotoxin injections showed compensatory changes to imposed defocus, but these were limited to compensation for imposed myopic defocus, at least for the eyes with optic nerve section. In addition, optic nerve section, but not tetrodotoxin treatment, moved the set-point of the visual compensatory mechanism toward hyperopia. Optic nerve section prevents myopia in response to negative lenses but not to diffusers, suggesting that compensation for hyperopia requires the central nervous system.

Animals↗
PubMed1992

Negative predictive value of a population-based preschool vision screening program.

BACKGROUND: The Enhanced Vision Screening Program is a population-based vision screening program that has, at present, examined 59,782 children. Its main goal is to detect amblyopia, strabismus, and high refractive errors. An average of 11,910 4 1/2- to 5 1/2-year-old children are screened yearly. The current study determines the negative predictive value of the screening program: For a subject having passed the vision screening test, what is the probability of not having amblyopia, strabismus, or high refractive errors? METHODS: Of the 11,734 subjects who passed the vision screening, 200 were randomly chosen to undergo a strictly defined gold standard examination by an orthoptist and an ophthalmologist. RESULTS: Of the 200 randomly chosen subjects, 157 underwent the gold standard evaluation. The negative predictive value of the Enhanced Vision Screening Program was 97.6% for any potentially vision-threatening ocular condition. It was 98.7% if we considered only the visually significant ocular problems that the test was designed to detect. CONCLUSION: Because the negative predictive value of the Enhanced Vision Screening Program is not 100%, some children with amblyopia, strabismus, or refractive errors are missed. Occasionally, a rare, potentially vision-threatening condition may go undetected. Parents should be made aware of this when they receive the results of the vision screening.

Child↗
PubMed2006

High myopia and glaucoma susceptibility the Beijing Eye Study.

OBJECTIVE: To evaluate whether marked myopia, compared with moderate myopia and low myopia, is associated with a higher prevalence of glaucomatous optic nerve damage. DESIGN: Population-based cross-sectional study. PARTICIPANTS: Four thousand four hundred thirty-nine of 5324 subjects 40 years or older were invited to participate (response rate, 83.4%). The group was stratified according to refractive error into high myopia (myopia > -8 diopters [D]), marked myopia (<-6 to -8 D), moderate myopia (<-3 to -6 D), low myopia (<-0.5 to -3 D), emmetropia (-0.5 to + <2 D), and hyperopia (>+ 2 D) subgroups. METHODS: Morphologic assessment of optic disc monoscopic photographs. MAIN OUTCOME MEASURES: Morphologic optic disc parameters and intraocular pressure (IOP). RESULTS: For 4319 (97.3%) subjects (8484 eyes), optic disc photographs were evaluated. Prevalence of glaucomatous optic nerve atrophy as defined by the glaucomatous optic nerve head appearance did not vary significantly (P = 0.77; odds ratio [OR], 1.2; 95% confidence interval [CI], 0.38-3.81) between the highly myopic group and the group with marked myopia. In both refractive groups combined, glaucoma frequency seemed to be higher (P = 0.075; OR, 2.28; 95% CI, 0.99-5.25) higher than in the group with moderate myopia; it was significantly (P = 0.001; OR, 3.5; 95% CI, 1.71-7.25) higher than in the group with low myopia; significantly (P<0.001; OR, 7.56; 95% CI, 3.98-14.35) higher than in the group with emmetropia; and significantly (P = 0.005; OR, 4.23; 95% CI, 1.57-11.45) higher than in the group with hyperopia. Glaucoma frequency did not vary significantly between the hyperopic group and the emmetropic group (P = 0.17), the group with low myopia (P = 0.83), and the group with moderate myopia (P = 0.32). Intraocular pressure did not vary significantly (P>0.10) between any of the subgroups. Similar results were obtained for the frequency of glaucoma defined as glaucomatous optic disc appearance and visual field defects. In binary logistic regression analysis, presence of glaucoma was significantly associated with the myopic refractive error (P<0.001), age (P<0.001), and IOP (P<0.001). CONCLUSIONS: Marked to high myopia with a myopic refractive error exceeding -6 D may be a risk factor associated with glaucomatous optic neuropathy.

Adult↗
PubMed2001

Refractive stabilization after temporal phacoemulsification with foldable acrylic intraocular lens implantation.

PURPOSE: To determine the rate of stabilization of refractive error after temporal small incision phacoemulsification with insertion of an acrylic foldable intraocular lens (IOL) (AcrySof MA30). SETTING: A university hospital anterior segment referral practice. METHODS: The records of 100 consecutive patients with good visual potential having phacoemulsification with acrylic IOL implantation who had good visual acuity on the first postoperative day were reviewed. Refractive data at 1 day, 1 week, and 1 and 4 months were compared. RESULTS: The mean spherical equivalent refraction was +0.31 diopter (D), -0.33 D, -0.51 D, and -0.35 D at 1 day, 1 week, 1 month, and 4 months, respectively. Cylinder by refraction was 1.17 D, 1.09 D, 0.96 D, and 0.99 D, respectively. From 1 week on, the cylinder power and axis did not differ significantly from that at 4 months. At 1 week, the spherical equivalent was within +/-0.50 D of the 4-month refraction in 66.1% of eyes and the cylinder was within +/-0.50 D in 72.9%. At 1 month, the corresponding values were 87.1% and 85.7%. CONCLUSION: The refractive error stabilized rapidly after temporal phacoemulsification with acrylic IOL implantation.

Acrylic Resins↗
PubMed1997

Vision profile of the athletes of the 1995 Special Olympics World Summer Games.

BACKGROUND: Special Olympics were organized in 1968 by Eunice Shriver as a program of physical fitness for individuals with mental handicaps. Numerous epidemiologic studies report an increase in visual problems in this population. METHODS: A comprehensive vision screening was conducted at the 1995 Special Olympic World Summer Games to identify the prevalence of visual anomalies in this select group. Testing included visual acuity, refractive error, ocular motor skills, stereopsis, color vision, contrast sensitivity, eye-hand coordination, eye-foot coordination, and an ocular health evaluation. RESULTS: Nine hundred five special athletes, ranging in age from 8 to 58 years, participated in the screening. More than 65% of the participants had not received eye care for more than 3 years. The most commonly reported symptom was difficulty in seeing. Other ocular health problems included refractive errors, poor distance monocular acuity, and strabismus. CONCLUSION: The results of the study indicate that Special Olympians have a high prevalence of vision anomalies that may go undetected. This population demonstrates a high prevalence of refractive errors, decreased visual acuity, ocular health problems, and strabismus. In addition, based on the number of individuals who have not received eye care within the last year, there is a need to increase the availability of vision care to these and other people with mental retardation.

Adolescent↗
PubMed2000

Developmental compensation of imposed astigmatism is not initiated by astigmatic accommodation in chickens.

PURPOSE: It is not clear whether emmetropization is confined to spherical refractive errors, or whether astiqmatic errors are also corrected via visual feedback. Experimental results from the animal model of the chicken are equivocal since compensation of imposed astimatic defocus was found in some but not all studies. Astigmatism could only be compensated by changes in the geometry of the cornea or lens. One has tested whether astigmatic spectacle lenses induce astigmatic accommodation as a possible first step of long-lasting compensation. METHODS: Thirty-five chickens were treated with cylinder lenses (+3/0D or -3/0D) for 5 h. Refractions were determined at 1.38 m distance without cycloplegia in hand-held chicks before attaching the lenses, with the lenses on (0 h), and after 3 and 5 h, and after removal of the lenses. Spheres (S), cylinders (C) and axes (A) were determined using infrared photoretinocopy in three axes (the 'PowerRefractor', equipped with a 135 mm lens). RESULTS: (1) The performance of the 'PowerRefractor' was tested in the chickens with trial lenses and gave correct refractions. (2) Astigmatic trial lenses induced refractive errors as expected from their powers in the case of +3/0D lenses: (S) +3.26 +/- 0.93D, (C) -3.45 +/- 0.87D). In the case of -3/0D lenses, slightly more hyperopic spheres were induced (refractions (S) +4.5 +/- 0.48D) but the cylinders were still as expected (-3.25 +/- 0.49D). The axes of astigmatism were correctly reproduced, since rotating the lenses changed the axes of the induced cylinders as expected. (3) Neither after 3 nor after 5 h of lens wear were there significant changes in the axes or the magnitude of astigmatism. Directly after removal of the lens, the refractions did not differ from their start-up values (with +3/0D lenses: (S) +3.31 +/- 1.05D vs. +3.22 +/- 0.76D, (C) -1.19 +/- 1.77D vs. -0.65 +/- 0.94D, (A) 96 +/- 49 vs. 113 +/- 45 deg; with -3/0D lenses: (S) 2.63 +/- 1.12D vs. 2.97 +/- 0.94D, (C) -1.11 +/- 1.15D vs. -0.53 +/- 0.56D, (A) 78 +/- 24 vs. 131 +/- 35 deg). CONCLUSIONS: The most intuitive mechanism for compensation of astigmatic refractive errors, astigmatic accommodation, could not be demonstrated in chickens. In light of this finding, it seems unlikely that a visually controlled mechanism is operating during development to reduced astigmatism by changing corneal or lenticular growth.

Accommodation, Ocular↗
PubMed2001

Patient outcomes of refractive surgery. The refractive status and vision profile.

PURPOSE: To evaluate the performance of a questionnaire, the Refractive Status and Vision Profile (RSVP), in the assessment of patient outcomes following refractive surgery. SETTING: Patients recruited from 5 refractive surgery practices. METHODS: The RSVP was self-administered by patients before and 2 to 6 months after bilateral refractive surgery. Information on uncorrected visual acuity (UCVA), refractive error, and self-reported satisfaction with vision was also collected. Changes in total RSVP scores and in the scores of RSVP subscales (concern, functioning, driving, symptoms, optical problems, glare, and trouble with corrective lenses) were assessed. The relationship between change in the RSVP and subscale scores was assessed in relation to change in traditional clinical measures. The responsiveness of the RSVP to clinically meaningful changes in patients' vision was measured by calculating its effect size. RESULTS: One hundred seventy-six patients completed baseline and postoperative RSVPs and had bilateral refractive surgery. Postoperatively, 92.0% of patients had a UCVA of 20/40 or better in at least 1 eye. Fifteen percent had some worsening in the total RSVP score, and there was substantial variation in the proportion of patients who had worsening in particular subscale scores, ranging from 7.0% who reported worsening in trouble with corrective lenses to 41.5% who reported worsening in driving. Change in satisfaction with vision following surgery was correlated with change in the overall RSVP and subscale scores but not with change in refractive error. A significant worsening in 3 or more RSVP subscales was independently associated with an almost 6-fold (odds ratio 5.84, 95% confidence interval: 1.88,18.13) likelihood of patient report of dissatisfaction with vision, after adjusting for age, sex, preoperative refractive error, and postoperative UCVA. Low scores (ie, minimal dysfunction) on 2 of the RSVP subscales (physical functioning and optical problems) at baseline were predictive of poor postoperative patient outcomes. The RSVP was very sensitive to the intervention of refractive surgery (effect size of 1.2 to 1.4). CONCLUSIONS: The RSVP was able to detect clinically relevant changes in functional status and quality of life after refractive surgery. Change in the RSVP score was correlated with change in patient report of satisfaction and was predictive of postoperative patient satisfaction. The RSVP provides a valuable new metric to assess outcomes of refractive surgery.

Activities of Daily Living↗