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At least 433 records · Page 24Linked to original sources
PubMed1992

Myopia following penetrating keratoplasty for keratoconus.

The frequent occurrence of spherical myopia after penetrating keratoplasty for keratoconus is partly the result of the excessive dioptric power of the grafted cornea which occurs when the diameter selected for the donor button is greater than the diameter of the host incision. This excessive power could be reduced by eliminating disparity between the diameters of the graft and host. To determine what proportion of the myopia in these eyes would persist as a result of axial myopia the axial lengths of 60 patients grafted for keratoconus and 25 emmetropic controls were compared. A keratometry, objective refraction, and contact probe ultrasonic biometry were performed on all eyes. A comparison of the results with a representational schematic eye indicated that the mean spherical refractive error of the grafted keratoconic eyes (-4.83 dioptres) was the combined effect of steepness of the corneal graft (mean radius of curvature 7.46 mm) and an abnormally great axial length (mean 24.84 mm). The increased axial length was mainly the result of elongation of the posterior segment of the globe with a small contribution from an increased anterior chamber depth. Though axial myopia is common in keratoconus, a further study of 70 keratoconic eyes that had not been grafted showed no statistically significant correlation between the posterior segment length and the severity of corneal ectasia. These data suggest that even if excessive corneal power is eliminated after penetrating keratoplasty for keratoconus the associated axial myopia would still produce a mean spherical refractive error of at least -2.8 dioptres.

Adult↗
PubMed2002

Development of myopia as a hazard for workers in pneumatic caissons.

BACKGROUND/AIM: Pneumatic caisson engineering has been developed for large civil engineering constructions. Because of complaints of blurred vision by personnel working in pneumatic caissons, the development of myopia was suspected. The aim of this study was to determine the cause of the blurred vision and the mechanism underlying the changes. METHODS: 12 caisson workers underwent a complete ophthalmological examination after completing up to 11 weeks of work (4 days/week) in a pneumatic caisson. Six months later, nine of the workers were examined again. RESULTS: Nine subjects were myopic at the initial examination, and seven of these were considered to have developed the myopia after starting to work in the pneumatic caisson. Six months after completion of the work, the mean refractive change was significantly towards hyperopia. CONCLUSIONS: The blurred vision in pneumatic caisson workers was in all likelihood due to the development of myopia. The refractive shift towards hyperopia after completion of work in the pneumatic caisson supports this and demonstrates that the changes were temporary. The myopia is similar to the myopia seen in patients treated by hyperbaric oxygen. Careful monitoring of the refraction of caisson workers should be performed for industrial health control.

Adult↗
PubMed2002

Myopia: attempts to arrest progression.

Previous studies have evaluated the efficacy of several interventions to decrease the progression of myopia. These include devices that alter the perception of the visual environment and pharmacological treatments. There is no conclusive evidence thus far that alteration of the pattern of spectacle wear, bifocals, ocular hypotensives, or contact lenses retards the progression of myopia. Several randomised clinical trials have demonstrated that the rate of progression of myopia is lower in children given atropine eye drops than those given placebo. However, atropine is associated with short term side effects such as photophobia and possible long term adverse events including light induced retinal damage and cataract formation. Other more selective antimuscarinic agents such as pirenzipine are presently being evaluated. Further well conducted randomised clinical trials with large sample sizes and adequate follow up designed to evaluate treatments to retard the progression of myopia should be conducted, since the identification of an effective intervention may have a greater public health impact on the burden and morbidity from myopia than the few treatments currently available.

Accommodation, Ocular↗
PubMed2003

Myopia, genetics, and ambient lighting at night in a UK sample.

BACKGROUND: It has been reported that exposure to artificial lighting at night during the first 2 years of life was very strongly associated with subsequent myopia development. METHODS: The strength of this association was tested in a UK sample for the first time. The study population comprised 122 university students. RESULTS: Myopia occurred with approximately equal frequency in those who slept with and without light exposure at night. In contrast, two largely genetic factors, parental myopia and race, were both significantly associated with myopia development, as has been found previously. CONCLUSION: This study provides further support for the view that night-time light exposure during infancy is not a major risk factor for myopia development in most population groups. In a subset of this cohort for which spectacle prescriptions were available for both parents (49 trios), the heritability of ocular refraction was estimated to be 0.31.

Adult↗
PubMed2003

Unilateral high myopia: optical components, associated factors, and visual outcomes.

AIM: To elucidate the optical basis for unilateral high myopia and to identify the factors associated with its development. METHODS: Medical records of 48 children (aged 4 months to 17 years; mean age 6.8 years) with unilateral high myopia (5 dioptres or more) seen consecutively by the author during a 15 year period were reviewed. 45 (94%) of the 48 patients had unilateral axial myopia. RESULTS: The mean refractive difference between paired eyes was 9.4 (SD 3.6) dioptres and the more myopic eye was on average 3.3 (1.8) mm longer than the less myopic eye. All but three of the patients had an ocular disorder associated with reduced acuity, central nervous system abnormality, or family history of high myopia. CONCLUSION: Clinical conditions associated with unilateral high myopia can be identified in the majority of patients and often account for the associated visual impairment.

Adolescent↗
PubMed1993

Education, reading, and familial tendency as risk factors for myopia in Hong Kong fishermen.

STUDY OBJECTIVE: The aim was to assess the influence of childhood reading on the development of myopia after allowance for familial differences in susceptibility. DESIGN: The study was a cross sectional survey. SETTING: Four fishing harbours in Hong Kong in 1989. SUBJECTS: Participants were 408 men and women aged 15-39 years old from 159 families. MAIN RESULTS: Histories of school attendance and reading habits in childhood were obtained at interview. Myopia was assessed by retinoscopy. Associations between myopia (defined as a refractive error of at least -1.0D in one or both eyes) and indices of reading in childhood were explored. Myopia was more common in subjects who had attended school (odds ratio = 1.7, 95% CI 1.0-3.0), with the highest risks in those who had started school at the earliest ages and who had spent the most time reading and writing while at primary school. Allowance for familial tendency to myopia produced no diminution in the risks associated with reading. CONCLUSIONS: These data support the hypothesis that reading in childhood is a cause of short sight.

Adolescent↗
PubMed2004

Association of ocular dominance and anisometropic myopia.

PURPOSE: To determine the association between ocular dominance and degree of myopia in patients with anisometropia. METHODS: Fifty-five subjects with anisometropic myopia were recruited. None of them had amblyopia. Refractive error and axial length were measured in each subject. Ocular dominance was determined using the hole-in-the-card test and convergence near-point test. RESULTS: There was a threshold level of anisometropia (1.75 D) beyond which the dominant eye was always more myopic than the nondominant eye. Of the 33 subjects with anisometropia of < or =1.75 D, the dominant eye was more myopic in 17 (51.5%) subjects. Dominant eyes, determined by the hole-in-the-card test, had a significantly greater myopic spherical equivalent (-5.27 +/- 2.45 D) than nondominant eyes (-3.94 +/- 3.10 D; P < 0.001). Dominant eyes also had a longer axial length than nondominant eyes (25.15 +/- 0.96 mm vs. 24.69 +/- 1.17 mm, respectively; P < 0.001). The difference was more evident in those subjects with higher anisometropia (>1.75 D), but was not significant in those with lower anisometropia (< or =1.75 D). Similar results were obtained using the convergence near-point test. CONCLUSIONS: The present study shows that the dominant eye has a greater degree of myopia than the nondominant eye in subjects with anisometropic myopia. Taking ocular dominance into account in the design of randomized clinical trails to assess the efficacy of myopia interventions may provide useful information.

Adult↗
PubMed2005

Inducing form-deprivation myopia in fish.

PURPOSE: To induce form deprivation myopia in fish and investigate the role of the lens in the development of refractive error. METHODS: Tilapia (Oreochromis niloticus), approximately 4 months old and from 26 to 63 g, were divided into three groups. Translucent goggles were directly sutured over the right eye for 4 weeks to induce form-deprivation myopia; the left eye served as an untreated contralateral control. The refractive state was measured by retinoscopy. Ocular dimensions were determined from frozen sections and with ultrasound biomicroscopy, and a scanning laser system was used to determine the optical quality of excised lenses. RESULTS: After 4 weeks of form-deprivation treatment, all the deprived fish eyes showed development of significant amounts of myopia ranging from -3.75 to -26.25 D, with the average amounting to -10.27 +/- 1.14 D. Eye dimension measurements show that the vitreous and anterior chambers of the treated eye are significantly longer axially than those of the contralateral eyes. No significant change in optical quality was found between lenses of the myopic and nonmyopic eyes. The fish recovered completely from the myopia 5 days after the goggle was removed. CONCLUSIONS: Although lower vertebrates are capable of lifelong growth, their eyes are susceptible to form-deprivation myopia. Thus, the visual environment is an important factor controlling ocular development in lower vertebrates, as well as in higher ones, and eye development is not strictly genetically determined. This study also indicates that lens growth and optical development are largely independent from the refractive development of the whole eye.

Animals↗
PubMed2006

Accommodative facility in eyes with and without myopia.

PURPOSE: To compare accommodative facility in eyes with myopia to that in eyes with emmetropia or hyperopia and to determine whether accommodative facility can be used to predict an association with myopia. METHODS: In the Sydney Myopia Study, year-1 school children (6.7 +/- 0.4 years) were assessed for accommodative facility at distance (3 m) and near (33 cm) with semiautomated flippers. Spherical equivalent refractive error (RE) was defined as myopia (< or = -0.50 D), emmetropia (> -0.50 D, but < +1.50 D), and hyperopia (> or = +1.50 D) based on postcycloplegia readings. Only right eye data were considered. Differences between groups were analyzed with the Brown-Forsythe F test after adjustment for age and gender. Multiple comparisons were adjusted with the by the Games-Howell METHOD RESULTS: Of the 1328 right eyes assessed, 20 (1.5%) eyes were myopic, 977 (73.6%) were emmetropic, and 331 (24.9%) were hyperopic. At distance, mean facility was less for myopic eyes at 5.5 +/- 2.0 cycles per minute (cpm) in comparison to 6.9 +/- 1.7 cpm for eyes with emmetropia or hyperopia (P = 0.005). Myopic eyes recorded greater positive and negative accommodative response times than did emmetropic or hyperopic eyes (P < 0.05). There were no differences among the groups in near facility. The area under the receiver operating characteristic (ROC) curve for distance facility was 0.692 (P = 0.003, 95% CI, 0.580-0.805). CONCLUSIONS: Myopic eyes have reduced accommodative facility at distance, and accommodative responsiveness to both positive and negative defocus is slow. However, accommodative facility as a test does not have sufficient power to discriminate eyes with myopia from other refractive errors.

Accommodation, Ocular↗
PubMed2006

Myopia, axial length, and OCT characteristics of the macula in Singaporean children.

PURPOSE: The purpose of this study was to evaluate the associations between macular volume and thickness, as assessed by optic coherence tomography (OCT), with refraction and axial length (AL) in children. METHODS: A total of 104 Chinese school children (51 girls and 53 boys) 11 to 12 years of age were randomly selected from one school during the 2005 examination in the Singapore Cohort Study of the Risk Factors for Myopia (SCORM). Cycloplegic autorefraction was performed to obtain refraction (defined as spherical equivalent [SE]) and ultrasound biometry performed to obtain the AL. Macular volume and thickness were then measured (StratusOCT3; Carl Zeiss Meditec, Dublin, CA). RESULTS: Children with moderate myopia (SE at least -3.0 D) tended to have smaller total macular volume and thinner quadrant-specific macular thickness (except in the inferior and superior inner quadrants), followed by children with low myopia (-0.5 -0.5 D). Total macular volume was positively associated with SE (beta=1.58, 95% CI, 0.84 to 2.32, standardized beta=0.14, P<0.001) and negatively associated with AL (beta=-1.20, 95% CI, -1.62 to -0.79, standardized beta=0.45, P<0.001) in multiple linear regression models controlling for age and gender. CONCLUSIONS: In children, increasing axial myopia was associated with reduced macular volume and thickness. These findings suggest that early anatomic changes may be present in the retinas of children with axial myopia.

Anthropometry↗
PubMed2006

Retinal nerve fiber layer measurements in myopia: An optical coherence tomography study.

PURPOSE: To evaluate the relationship between retinal nerve fiber layer (RNFL) thickness measured by optical coherence tomography (OCT) and the axial length/refractive error of the eye. METHODS: A total of 115 eyes of 115 healthy subjects, comprising 75 eyes with high myopia (spherical equivalent [SE] < -6.0 D) and 40 eyes with low to moderate myopia (SE between -6.0 D and -0.5D), were analyzed in this cross-sectional study. Total average and mean clock hour RNFL thicknesses were measured by OCT and compared between the two myopia groups. Associations between RNFL measurements and axial length and spherical equivalent were evaluated by linear regression analysis. RESULTS: The RNFL measurements were significantly lower in the high myopia group compared with those of the low-to-moderate myopia group at 12, 1, and 7 o'clock (right eye orientation). Apart from the temporal clock hours, significant correlations were evident between RNFL measurements and the axial length and spherical equivalent. The average RNFL thickness decreased with increasing axial length (r = -0.314, P = 0.001) and negative refractive power (r = 0.291, P = 0.002). A significant proportion of myopic eyes were classified as outside normal limits, with reference to the normative database. The most frequently abnormal sector was at 2 o'clock, where 16.5% of myopic eyes were outside normal limits. CONCLUSIONS: RNFL measurements vary with the axial length/refractive error of the eye. Analysis of RNFL thickness in the evaluation of glaucoma should always be interpreted with reference to the refractive status. Although the normative database provided by OCT has been helpful in identifying ocular diseases involving the RNFL, it may not be reliable in the analysis of myopic eyes.

Adult↗
PubMed2005

Little evidence for an epidemic of myopia in Australian primary school children over the last 30 years.

BACKGROUND: Recently reported prevalences of myopia in primary school children vary greatly in different regions of the world. This study aimed to estimate the prevalence of refractive errors in an unselected urban population of young primary school children in eastern Sydney, Australia, between 1998 and 2004, for comparison with our previously published data gathered using the same protocols and other Australian studies over the last 30 years. METHODS: Right eye refractive data from non-cycloplegic retinoscopy was analysed for 1,936 children aged 4 to 12 years who underwent a full eye examination whilst on a vision science excursion to the Vision Education Centre Clinic at the University of New South Wales. Myopia was defined as spherical equivalents equal to or less than -0.50 D, and hyperopia as spherical equivalents greater than +0.50 D. RESULTS: The mean spherical equivalent decreased significantly (p < 0.0001) with age from +0.73 +/- 0.1D (SE) at age 4 to +0.21 +/- 0.11D at age 12 years. The proportion of children across all ages with myopia of -0.50D or more was 8.4%, ranging from 2.3% of 4 year olds to 14.7% of 12 year olds. Hyperopia greater than +0.50D was present in 38.4%. A 3-way ANOVA for cohort, age and gender of both the current and our previous data showed a significant main effect for age (p < 0.0001) but not for cohort (p = 0.134) or gender (p = 0.61). CONCLUSIONS: Comparison of our new data with our early 1990s data and that from studies of over 8,000 Australian non-clinical rural and urban children in the 1970's and 1980's provided no evidence for the rapidly increasing prevalence of myopia described elsewhere in the world. In fact, the prevalence of myopia in Australian children continues to be significantly lower than that reported in Asia and North America despite changing demographics. This raises the issue of whether these results are a reflection of Australia's stable educational system and lifestyle over the last 30 years.

Child↗
PubMedDate not supplied

Epikeratoplasty for myopia: 2-year results and a proposed nomogram.

BACKGROUND: Epikeratoplasty for myopia is a relatively safe and reversible surgical technique that can result in large refractive corrections. However, it is also claimed that long-term stability and predictability are not satisfactory due to refractive regression and undercorrection. METHODS: In an effort to improve predictability and stability of epikeratoplasty for myopia, we followed 24 cases for 2 years and isolated factors affecting the postoperative refractive results. RESULTS: We found that better refractive results were achieved at 24 months postoperatively for cases in which the power of preoperative myopia was lower. Our investigations also disclosed no significant correlation between the surgical outcome at 24 months and patients' sex, age, and preoperative keratometric readings. CONCLUSION: On the basis of our observations, we propose a new nomogram where higher powers of minus keratolenses, compared to the traditional prescription chart, should be selected for those with high preoperative myopia to result in improved long-term results with epikeratoplasty for myopia. This nomogram has not yet been clinically tested.

Adult↗
PubMedDate not supplied

Radial keratotomy for myopia from 5.00 to 13.00 diopters two years after surgery.

BACKGROUND: Radial keratotomy for low myopia can produce good results with few side effects. For higher myopia, predictability becomes less accurate and side effects more common. METHODS: A retrospective study of 111 eyes of 76 patients were divided into two groups. Group I had 79 eyes with myopia of -5.00 to -8.00 diopters (D); group II had 32 eyes with myopia -8.25 D to -13.00 D. One hundred eleven eyes were followed for 1 year and 90 eyes were followed for 2 years. RESULTS: Sixty-seven (84.8%) eyes in group I and 12 (37.5%) eyes in group II achieved a refraction within the range of -1.00 D and +1.00 D. Ninety-two percent of group I and 44% of group II achieved an uncorrected visual acuity of 20/40 or better. Three percent lost spectacle-corrected visual acuity. Four eyes developed a hyperopic shift of 1.00 D or more between 2 months and 2 years. Seven other eyes developed a hyperopic shift of 1.00 D or more between 2 months and 5 years. CONCLUSIONS: Eight-incision radial keratotomy is an attractive option for treatment of myopia up to -8.00 D. For levels above -8.00 D, the results are poorer; there may be a variable period before refraction stabilizes.

Adult↗
PubMed1996

Laser in situ keratomileusis (LASIK) for myopia from -7 to -18 diopters.

BACKGROUND: Laser in situ keratomileusis (LASIK) combines a lamellar corneal flap with an excimer laser ablation in the stromal bed to correct a wide range of myopia. We reviewed 43 eyes treated with LASIK to correct -7.00 to -18.50 diopters (D). METHOD: The data from 43 consecutive eyes of 30 patients aged 24 to 46 years were analyzed. Surgery was performed under topical anesthesia using the Chiron Automated Corneal Shaper and Keracor 116 Excimer laser with the multizone mode and our modified nomogram. Manifest and cycloplegic refraction, uncorrected visual acuity, spectacle corrected visual acuity, videokeratography, endothelial cell count, slit-lamp microscopy, fundus examination, and applanation tonometry were recorded preoperatively and at 1 week and 1, 3, and 6 months, postoperatively. RESULTS: We divided the eyes into two groups. The lower myopia group had a mean preoperative spherical equivalent refraction of -9.30 +/- 1.31 D (range: -7.00 D to -12.00 D) and mean postoperative refraction of -0.80 +/- 0.79 (range: -0.25 D to -3.50 D). The mean spectacle corrected visual acuity preoperatively was 0.74 +/- 0.20 and postoperatively was 0.74 +/- 0.18. The higher myopia group had a mean preoperative spherical equivalent refraction of -14.86 +/- 1.87 D (range: -12.25 D to -18.50 D) and a mean postoperative refraction of -1.80 +/- 1.29 D (range -1.00 D to -5.25 D). The mean spectacle corrected visual acuity preoperatively was 0.50 +/- 0.19 and postoperatively was 0.51 +/- 0.18. No overcorrections occurred in either group. One eye of the higher group lost one line of spectacle corrected visual acuity. No eye had visually significant corneal haze. The mean change in spherical equivalent refraction between preoperatively and 6 months postoperatively was 8.50 D for the lower myopia group and 13.06 D for the higher myopia group, in the myopic direction. Visual rehabilitation was rapid after surgery. CONCLUSIONS: In this study, LASIK resulted in insignificant corneal scarring, stable refractive correction over six months, no irregular astigmatism, and excellent visual acuity. Predictability was more accurate up to -12.00 D of intended correction.

Adult↗
PubMed1996

Double zone PRK for high myopia.

INTRODUCTION: Although excimer laser PRK is our operation of choice for treating myopia, the correction of myopia exceeding -8.00 dpt is still a challenge as this procedure requires a deeper keratectomy. Therefore a double zone treatment may be beneficial to reduce ablation depth. METHODS: Twenty-one eyes with myopia between -8.00 dpt and -14.00 dpt were included in this study. Twelve eyes were treated 60% of myopia by 5 mm zone and the remaining 40% in a 4 mm zone in the same session (Group 1). RESULTS: Nine eyes achieved 60% of the desired correction treated with a 4 mm zone whereas 40% correction was achieved in a 5 mm zone (Group 2). No significant difference in postoperative healing, pain, hyperopic shift, myopic regression and haze was observed at the end of the mean follow-up time (10.4 months) but photophobic complaints were less in Group 2. Best corrected visual acuity did not decrease significantly. CONCLUSIONS: Double zone treatment seems to be an interesting method for treating moderate to high myopia.

Adult↗
PubMedDate not supplied

Age-related refractive shifts in simple myopia.

BACKGROUND: An understanding of physiologic age-related shifts in myopic refractive errors is important to the refractive surgeon for the interpretation of long-term results, surgical planning, and patient counseling. This study characterizes the refractive stability of adult simple myopia with a retrospective study of 413 eyes. METHODS: Approximately 74,000 patient records were analyzed to identify 208 adults with -1.00 to -6.00 diopters (D) of myopia who were followed for more than 20 years at the Spokane Eye Clinic. Amounts of myopic shift (increase in myopia) and hyperopic shift (decrease in myopia) were identified and analyzed within the population. The results were compared to long-term studies of radial keratotomy. RESULTS: The mean changes per patient age decade were: 20s, -0.60 D; 30s, -0.39 D; 40s, -0.29 D; 50s, +0.28 D; 60s, +0.41 D. Reanalyzed Prospective Evaluation of Radial Keratotomy (PERK) study 10-year postoperative data demonstrated progressively increasing hyperopic shifts per decade, at least to age 50. CONCLUSION: The normal adult population with simple myopia differs from the general population and consists of a population subgroup that is relatively stable and other subgroups that experience significant refractive shift. The hyperopic shift after radial keratotomy appears to be surgically induced and may be larger than previously thought.

Adult↗
PubMed1997

Laser in situ keratomileusis for myopia of -1 to -3.50 diopters.

BACKGROUND: Laser in situ keratomileusis (LASIK) is the procedure of choice for high myopia. We present a study of 85 eyes undergoing LASIK for myopia between -1.00 and -3.50 diopters (D) and assess the safety and efficacy of the procedure for treatment of low myopia. METHODS: Eighty-five eyes of 47 patients with a mean age of 29 years, (range, 18 to 56 yrs) underwent LASIK using the Chiron microkeratome and the Nidek EC-5000 excimer laser. Mean preoperative myopia was -2.09 D and mean astigmatism was 0.86 D. All other ocular pathology was ruled out before surgery. Mean follow-up was 48 days (range, 1 day to 13 mo). RESULTS: Uncorrected visual acuity of 6/9 or better at 1 week was achieved in 44 eyes (52%); at 1 month in 68 eyes (80%); and at 6 months in 70 eyes (93%). Pain score was minimal with the majority of patients having no postoperative pain. One eye suffered a serious postoperative complication of corneal abscess which resolved with treatment, but left a corneal scar and visual acuity of 6/60. CONCLUSION: LASIK is a safe and effective procedure for low amounts of myopia; it also provides early visual rehabilitation and markedly reduced pain and discomfort to patients undergoing refractive surgery.

Adolescent↗