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At least 1,153 records · Page 64Linked to original sources
PubMed2000

Characteristics of the myopic patient population applying for refractive surgery.

PURPOSE: Assessment of the characteristics of the myopic patient population applying for refractive surgery in order to determine the potential market for myopic refractive surgery. METHODS: Records of consecutive patients who responded to an advertisement for refractive surgery to correct myopia were evaluated retrospectively with regards to patient demographics and the amount and distribution of the refractive error. Data were compared to that available from population-based statistics for distribution of myopia in the general population. For statistical analysis, one sample Student's t-test and two tailed Student's t-test were utilized. RESULTS: Two hundred fifty seven patients (140 women and 117 men) responded to an advertisement for refractive surgery during the six month period between January and June 1998. Mean spherical equivalent (SEQ) of the patient population was -4.59+/-2.54 D (min;-0.25 D, max;-15.75 D) right eye (OD) and -4.62+/-2.82 D (min;-0.25 D, max;-15.25 D) left eye (OS). Among the patients who had myopia with an astigmatism of at most 1.00 D (n=165), the distribution of refractive error was statistically significantly different from that obtained from population-based statistics, such that, although most of the myopic population (40%) had an SEQ of -1.00 to -2.25 D, the majority of our patients (54.8%) who applied for myopic refractive surgery had an SEQ of -2.50 to -5.00 D. Another striking difference was that, although patients with an SEQ more than -6.00 D were a minority(2%) in the population study, in our study group, they comprised 16.7% of the patients seeking refractive correction. The difference between the SEQ of the right and left eyes ranged from 0.00 D to 13.0 D (mean, 0.89+/-1.5 D), 47.1 % having a difference of at most +/-0.5 D between the two eyes. The mean cylindrical error in the patient population was 0.69+/-0.93 D (min: 0, max: -4.5) OD and 0.69+/-0.96 D (min: 0, max: -4.5) OS. There were no statistically significant differences between the distribution of SEQ or cylindrical refractive error between males and females. CONCLUSION: Although a population-based study reported that most of the myopic population (40%) had an SEQ of -1.00 to -2.25 D, the majority of our patients (54.8%) who applied for myopic refractive surgery had an SEQ of -2.50 to -5.00 D. On the other hand, while patients with an SEQ of -6.00 D and more constituted only about 2% of the general population, they accounted for 16.7% of our study population. Therefore, the refractive characteristics of the patient population applying for myopic refractive surgery may not necessarily parallel that of general population-based statistics. In order to establish a more effective refractive surgery practice, it is feasible to perform local studies and reevaluate the requirements of your practice accordingly.

Adolescent↗
PubMed2007

Myopia prevalence in Chinese-Canadian children in an optometric practice.

PURPOSE: The high prevalence of myopia in Chinese children living in urban East Asian countries such as Hong Kong, Taiwan, and China has been well documented. However, it is not clear whether the prevalence of myopia would be similarly high for this group of children if they were living in a Western country. This study aims to determine the prevalence and progression of myopia in ethnic Chinese children living in Canada. METHODS: Right eye refraction data of Chinese-Canadian children aged 6 to 12 years were collated from the 2003 clinical records of an optometric practice in Mississauga, Ontario, Canada. Myopia was defined as a spherical equivalent refraction (SER) equal or less than -0.50 D. The prevalence of myopia and refractive error distribution in children of different ages and the magnitude of refractive error shifts over the preceding 8 years were determined. Data were adjusted for potential biases in the clinic sample. A questionnaire was administered to 300 Chinese and 300 Caucasian children randomly selected from the clinic records to study lifestyle issues that may impact on myopia development. RESULTS: Optometric records of 1468 children were analyzed (729 boys and 739 girls). The clinic bias adjusted prevalence of myopia increased from 22.4% at age 6 to 64.1% at age 12 and concurrently the portion of the children that were emmetropic (refraction between -0.25 and +0.75 D) decreased (68.6% at 6 years to 27.2% at 12 years). The highest incidence of myopia for both girls ( approximately 35%) and boys ( approximately 25%) occurred at 9 and 10 years of age. The average annual refractive shift for all children was -0.52+/-0.42 D and -0.90+/-0.40 D for just myopic children. The questionnaire revealed that these Chinese-Canadian children spent a greater amount of time performing near work and less time outdoors than did Caucasian-Canadian children. CONCLUSIONS: Ethnic Chinese children living in Canada develop myopia comparable in prevalence and magnitude to those living in urban East Asian countries. Recent migration of the children and their families to Canada does not appear to lower their myopia risk.

Asian People↗
PubMed1997

Development of refraction and strabismus.

The goal of current research on the development of refraction is not to establish whether refraction is either genetically programmed or environmentally influenced, but to assess how heredity and environment interact in the genesis of refractive error. The continuing problem in strabismus research is one of cause and effect. Do binocular deficiencies induce strabismus, or is it the other way around? The papers highlighted in this article address these critical issues. The new findings have the potential to influence the treatment and clinical care of patients with refractive errors and strabismus.

Animals↗
PubMed2004

[Frequency doubling perimetry in diagnosis of early glaucomatous optic nerve fiber damage].

PURPOSE: The comparative evaluation results of frequency doubling technology (FDT) in healthy subjects, in patients with glaucoma suspected and glaucoma, as well as analysis influences of selected risk factors onset, and progression of glaucoma (age, gender, intraocular pressure, refractive errors, circulation system disease, diabetes mellitus, vasospastic vascular disease) on FDT-parameters. MATERIAL AND METHODS: Sixty four patients (128 eyes), in age between 13-80, with refraction error from -14.5 to +6.5 D sph and average intraocular pressure 19.8 +/- SEM were included in this study. All patients were previously diagnosed towards glaucoma. The visual field testing with help of FDT Visual Field Instrument were made at least triple at all patients, with capitalize on the THR N-30 threshold program. Global indices: mean deviation (MD) and pattern standard deviation (PSD) and numerical value of mean retinal sensitivity for central visual field 5 degree sector (mean sensitivity to central 5 degrees--MS 5 degrees) come in comparative analysis. All data were analyzed by chi2 and Kruskal-Wallis tests. RESULTS: Comparative analysis examined groups of healthy persons, patients with glaucoma suspect and glaucoma, it proves statistically significant difference between MD, PSD and MS 5 degrees. Statistically no significant difference between PSD and MS 5 degrees at groups of healthy and glaucoma suspect patients was detected. In glaucoma group there did not reveal an influence on selected risk factors on FDT parameters. However, in glaucoma suspect group revealed an influence on most risk factors on perimetry parameters. CONCLUSIONS: FDT is useful for detection of glaucomatous nerve fiber damage. There should be taken precautions of interpretation FDT results at glaucoma suspect patients.

Adolescent↗
PubMed2000

Ocular components before and after acquired, nonaccommodative esotropia.

BACKGROUND: Acquired nonaccommodative esotropia describes the sudden onset of a constant, comitant strabismus of idiopathic origin in children >6 months of age. CASE REPORT: We present a case of acquired nonaccommodative esotropia at 20 months of age in a subject participating in the Berkeley Infant Biometry Study, a longitudinal study of emmetropization and ocular component development in infants between 3 months and 3 years of age. Ocular components for this child were normal before the onset of strabismus (within 2 SD's of the mean for orthotropic study participants) for refractive error, corneal power, lens radii, lens power, and ocular axial dimensions. Refractive error postsurgically was significantly more hyperopic and crystalline lens power lower than average at +2.38 D and 37.2 D, respectively. CONCLUSIONS: The lack of abnormal ocular parameters is consistent with the idiopathic etiology of acute onset esotropia. This case suggests that ocular component values may not be useful for assessing the risk of acquired nonaccommodative esotropia.

Accommodation, Ocular↗
PubMed1988

Selected review on genetic factors in myopia.

This article reviews representative literature concerning pedigrees for myopia, heritability studies on refractive error and the ocular components, and other work relating to genetic factors in myopia development. Low myopia most likely reflects the influences of multiple genes. Some types of high myopia may have monogenic inheritance. Refractive error and the ocular refractive components have heritabilities intermediate between zero and one, as complied from several studies, indicating familial resemblance, but also non-genetic variation. It is likely that both heredity and environment have roles in determining refractive status. An understanding of their respective roles awaits the elucidation of the cellular and anatomical mechanisms of myopia development.

Humans↗
PubMed2006

New Zealand cataract and refractive surgery survey 2004.

BACKGROUND: This study examines the current practice and trends for cataract and refractive surgery in New Zealand. METHODS: A confidential postal questionnaire was sent to all consultant ophthalmologists practising in New Zealand in 2004. Most questions were identical to the 2000 New Zealand survey, and were also similar to the 2003 survey of the American Society of Cataract and Refraction Surgeons (ASCRS). RESULTS: From 97 surveys there was a 92% response rate. Of those surveyed, 70 were performing cataract surgery, 17 were performing refractive surgery, subtenons anaesthetic was used for cataract surgery in 60%, clear corneal or anterior limbal incision in 86%, one-piece foldable intraocular lens in 65%. For refractive surgery, use of refractive lens surgery was recommended for high refractive errors. Advice to a 45-year-old +3.00 hypermetrope wanting refractive surgery was to have laser in situ keratomileusis (88%), laser epithelial keratomileusis (6%) or clear lens extraction (6%). Ninety-four per cent of refractive surgeons in New Zealand used a wavefront analyser. Clear lens extraction was practised by 23 ophthalmologists, phakic intraocular lenses by 16 ophthalmologists. DISCUSSION: New Zealand cataract and refractive surgery practice remains comparable to that of the members of the ASCRS. As in previous comparisons, there is a relatively low use of topical anaesthetic (New Zealand 19%vs. USA 61%vs. UK [pilot study] 33.3%). This survey showed a high uptake of wavefront analysis in refractive surgery (New Zealand 94%vs. USA 45%).

Adult↗
PubMed1994

[Research on corneal thickness at multi-points in normal and myopic eyes].

The corneal thickness of the center and other 24 points were measured in 31 normal eyes and 246 myopic eyes. The results show that the mean central corneal thickness of the normal eye is 541 +/- 45.29 microns and that of the myopic eye, 544 +/- 35.01 microns. There are no significant differences in the central corneal thickness in comparisons between the left and right eye, between the male and female, among various age groups, and among various degrees of refractive error. However, with the increase of age and increase of myopic refractive error, the central corneal thickness gradually becomes thinner. There are differences in thickness among various directions, the superior direction being the thickest and the temporal inferior, the thinnest. From the center to the limbus, the thickness of the cornea gradually increases, but the values of the increase of the thickness are various in various directions, that should be paid attention to in radial keratotomy.

Adolescent↗
PubMed1994

[The difference between right and left in vitreous findings of normal eyes].

The vitreous in both normal eyes of 671 normal subjects was studied biomicroscopically. The results obtained were as follows: 1. In 618 cases of a refractive error less than -3D (group A) and 53 cases of refractive error over -3D (group B), the incidence of posterior vitreous detachment (PVD) in both eyes increased with age and the absence of PVD in both eyes decreased with age. The percentage of cases with PVD in one eye and no PVD in the other eye was less than 22% in all age groups. 2. There was no significant difference in the degree of vitreous liquefaction between the right and the left eyes. The degree of vitreous liquefaction was also age-related. 3. In the cases with PVD in one eye and no PVD in the other eye, a higher incidence of mild vitreous liquefaction was found in group A than in group B. 4. PVD without collapsed vitreous (simple PVD) in both eyes was observed only in group A. 5. Our results indicated that the vitreous findings in both eyes of an individual were almost identical, and PVD may occur with less vitreous liquefaction in group A than in group B.

Adolescent↗
PubMed2000

The prevalence of ocular defects and the provision of eye care in adults with learning disabilities living in the community.

Most people with learning disabilities now live in the community rather than in institutions, and community services need to be targeted appropriately. Vision screening was carried out in community Day Care Centres for adults with learning disabilities. One hundred and fifty four subjects took part, and screening was successful in 148 subjects, using retinoscopy and standard acuity tests, including preferential looking. The previously reported high prevalence of refractive errors, strabismus and pathological defects amongst people with learning disabilities was confirmed. Over 60% of subjects had below-normal distance acuity, which in many cases was exacerbated by uncorrected refractive errors. In all, 41% of subjects could have benefited from distance spectacles, and 56% from spectacles for near tasks. The lack of adequate spectacles was particularly high amongst adults with more severe learning disabilities. The study highlights the current lack of adequate eye care for people with learning disabilities, and demonstrates that eye examinations are possible for the majority of individuals. There is a need for greater awareness amongst families/carers and amongst optometrists to address this important issue.

Adult↗
PubMed2003

[Emmetropization at cataract surgery. Looking for the best IOL power calculation formula according to the eye length].

PURPOSE: To determine the predictability of different intraocular lens (IOL) power calculation formulas (SRK-II, Binkhorst-II, Hoffer Q, Holladay y SRK/T) according to the axial length (AL). METHOD: The residual refractive error for each formula was determined in 212 cases of phacoemulsification with IOL implantation and it was compared to the < > result (the ideal result was emmetropia in all cases). RESULTS: The refractive error obtained with all different formulas for the AL group between 22 and 28 mm was not statistically significant. The error between the AL group of <22 mm and the AL group between 22-28 mm was not statistically significant for Binkhorst-II and Hoffer Q formulas. The error between the AL group > 28 mm and the group between 22-28 mm was not statistically significant for SRK/T. CONCLUSION: For small eyes (<22 mm) the Binkhorst-II and Hoffer Q formulas provided the best predictive results, whereas in long eyes (>28 mm) the SRK/T is the most accurate.

Humans↗
PubMed2004

Effects of optically imposed astigmatism on emmetropization in infant monkeys.

PURPOSE: Although astigmatism is prevalent during early infancy, the influence of astigmatism on early refractive development is unclear. This study was undertaken to determine the effects of astigmatism on emmetropization in monkeys. METHODS: Infant rhesus monkeys (n = 39) were exposed to optically simulated astigmatism in one or both eyes from approximately 1 to 4 months of age. With-the-rule, against-the-rule, and oblique astigmatisms were optically simulated by appropriately orienting the principal meridians of the spherocylindrical treatment lenses (+1.50 -3.00 D x 90 degrees, 180 degrees, 45 degrees, or 135 degrees; i.e., +1.50 and -1.50 D powers in the two principal meridians). Refractive development was assessed every 2 to 3 weeks by cycloplegic retinoscopy, keratometry and corneal videotopography, and A-scan ultrasonography. Data from 19 control monkeys, including 3 animals that were reared with binocular plano lenses, were used for comparison purposes. RESULTS: Most of the cylinder-lens-reared monkeys, regardless of the orientation of the imposed astigmatism, showed clear signs of either hyperopic or myopic growth compared with control monkeys. The distributions of refractive error and vitreous chamber depth both showed bimodal patterns that differed from normal by amounts equivalent to the optical powers of the principal meridians of the treatment lenses. More frequently, refractive development was biased toward the eye's least-hyperopic focal plane. The refractive changes were mainly axial. After lens removal, the lens-reared monkeys recovered and as a group exhibited refractive errors and axial dimensions similar to those in control monkeys. CONCLUSIONS: In the presence of significant amounts of astigmatism, emmetropization is directed toward one of the two focal planes associated with the astigmatic principal meridians and not the circle of least confusion. These results suggest that the mechanisms responsible for emmetropization are insensitive to stimulus orientation and the global form of the retinal image. It appears that emmetropization seeks out the image plane that contains the maximum effective contrast integrated across spatial frequency and stimulus orientation.

Animals↗
PubMed2006

Visual acuities and manifest refractions prior to LASIK retreatments.

PURPOSE: To demonstrate that patients undergoing LASIK retreatments generally have good uncorrected vision and small refractive errors prior to retreatment surgery. METHODS: A list was generated of all refractive surgery retreatments performed in our four laser centers from August 2003 to July 2004. From this list, a total of 100 patient charts were randomly chosen. Only eyes that had full distance correction with LASIK as the primary surgery were included. The last uncorrected visual acuity (UCVA) and manifest refraction spherical equivalent (MRSE) prior to retreatment were recorded. RESULTS: For a total of 109 eyes studied, the average UCVA prior to retreatment was 20/36. Eighty-one percent (88/109) of the retreated eyes were already seeing > or = 20/40. The average MRSE prior to retreatment was -0.43 +/- 0.98 D. CONCLUSIONS: The majority of patients receiving LASIK retreatments have relatively good uncorrected vision and minimal refractive errors prior to retreatment.

Adult↗
PubMed1984

Normalization of binocular VERs after early onset visual deprivation in man.

Visually evoked responses (VERs) were elicited by a reversing checkerboard target from a patient who suffered early onset bilateral deprivation of form vision as a result of a high refractive error, large amplitude strabismus, and congenital nystagmus. Monocular and binocular steady-state VERs were abnormal in amplitude and wave form even when a correction for the patient's large refractive error (compound hyperopic astigmatism) was worn. Although monocular VERs could not be normalized, a normal wave form and amplitude were restored to the binocular VER by the addition of horizontal prisms to the patient's ophthalmic prescription. The initially degraded binocular VER gradually acquired a normal morphology and amplitude as the magnitude of compensating base-out prisms in the patient's habitual ophthalmic prescription was systematically increased. The relationship between the binocular VER amplitude and the correcting prisms derived by the method described in this paper was subsequently used to arrive at a practical clinical solution for the patient's unusual and debilitating visual symptoms. This electrophysiological evaluation of binocular function at the cortical level proved to be a very useful diagnostic procedure with prognostic value; standard clinic procedures were ineffective in elaborating the patient's sensory and oculomotor disorders. The theoretical and practical implications of managing patients with a history of early onset visual deprivation are discussed.

Adult↗
PubMed2005

Prevalence of visual deficits among young men in Jordan.

OBJECTIVE: To report the pattern of various causes of decreased visual acuity (VA), within the age group of young (18-25 years) healthy adults in Jordan. METHODS: We carried out this retrospective study on the records of 16,550 candidates examined from June 2004 to June 2005 by the Medical Committee of Employment, Royal Medical Services in Amman, Jordan. All candidates received an ophthalmic examination as well as medical and ENT examination. We divided the candidates with visual acuity of less than 6/12 in either eye into 3 groups. RESULTS: The most important cause of decreased VA in the 18-25 years age group was refractive errors followed by amblyopia, which represents the major ophthalmic cause of employment rejection in a wide range of occupations in adult life. CONCLUSION: This study emphasize the need for early visual screening for refractive errors and anisometropic amblyopia in early primary schools, and every effort must be made to achieve the best possible acuity in young patients with amblyopia.

Adolescent↗
PubMed1993

Testing the FOCOMETER--A new refractometer.

The FOCOMETER, an optometer which measures spherical refractive errors, is intended to provide rural or economically disadvantaged populations spherical prescriptions without the need for complicated protocols, expensive equipment, or electricity. FOCOMETER readings were compared with the spherical equivalent determined from autorefraction and subjective trial lens refractions in children, and with retinoscopy in adults. Over the range of refractive errors tested (-4 to +5 D) reasonably close readings, within one-half a diopter, were found for comparisons with autorefraction and retinoscopy and about one-tenth of a diopter difference was found between subjective refractions and the FOCOMETER.

Adolescent↗
PubMed2005

Random measurement error in visual acuity measurement in clinical settings.

PURPOSE: To estimate the random measurement error in visual acuity (VA) determination in the clinical environment in cataractous, pseudophakic and healthy eyes. METHODS: The VAs of patients referred for cataract surgery or consultation by ophthalmic professionals were re-examined and the VA results for distance using projector acuity charts were compared. Refractive errors were also remeasured. A total of 99 eyes (41 cataractous, 36 pseudophakic and 22 healthy eyes) were examined. The healthy comparison group consisted of hospital staff. Only one eye of each person and eyes with Snellen VAs of 0.3-1.3 (logMAR 0.52 to - 0.11) were included. The mean time interval between the first and second examinations was 45 days. RESULTS: The estimated standard deviation of measurement error (SDME) of repeated VA measurements of all eyes was logMAR 0.06. Eyes with the lowest VA (0.3-0.45) had the largest variability (SDME logMAR 0.09), and eyes with VA > or = 0.7 had the smallest (SDME logMAR 0.04). The variability may be partly explained by the line size progression in lower VAs, partly by the difference in the remeasurement of the refractive error. The difference in the average VA between examinations 1 and 2 (logMAR 0.15 versus 0.12) was considered to be of some interest because it indicates that some learning effect is possible. CONCLUSION: Visual acuity results in clinical settings have a certain degree of inherent variability. In this series variability ranged from SDME logMAR 0.04 (eyes with good vision) to logMAR 0.09 (in the lower vision group) in the Snellen VA range of 0.3-1.3. Changes should be judged with caution, especially in cases of decreased VA.

Adult↗
PubMed2002

Referral rates for a functional vision screening among a large cosmopolitan sample of Australian children.

The aim of this study was to investigate the incidence of functional vision problems in a large unselected cosmopolitan population of primary school-age children and to investigate whether constant clinical criteria for functional vision problems would be implemented by the practitioners involved in the screening. Refractive errors, near point of convergence, stereopsis, strabismus, heterophoria and accommodative facility were assessed for 2697 children (3-12 years) of varying racial backgrounds living in Australia. The spherical component of the refractive error ranged from -7.75 to +9.50 D (mean +0.54 D, +/-0.79) with a distribution skewed towards hypermetropia; astigmatism ranged from 0 to 4.25 D (mean -0.16 D, +/-0.35). There was a trend towards less hypermetropia and slightly more astigmatism with age. Mean near point of convergence was 5.4+/-2.9 cm, heterophoria at far and near was 0.12+/-1.58delta exophoria and 1.05+/-2.53delta exophoria, respectively, 0.55% of children exhibited vertical phoria at near >0.5delta, accommodative facility ranged from 0 to 24 cycles per minute (cpm) (mean 11.2 cpm, +/-3.7), stereopsis varied from 20 to 800 s (") of arc with 50% of children having 40" or better. The prevalence of strabismus was particularly low (0.3%). Twenty percent of the children were referred for further assessment based on criteria of one or more of: stereopsis >70", accommodative facility <8 cpm, near point of convergence (NPC) >9 cm, near exophoria >10delta or near esophoria >5delta, shift in eso or exophoria > or = 4delta between distance and near, astigmatism > or = 1 D, myopia more than -0.75 D, or hyperopia >+1.50 D. Post-hoc analysis of the record cards seeking the reason for further assessment indicates that referrals appear to have been based upon clinical intuition rather than on a set number of borderline or unsatisfactory results.

Accommodation, Ocular↗