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At least 721 records · Page 40Linked to original sources
PubMed1998

Factors influencing the outcome of hyperopic lamellar keratoplasty.

PURPOSE: To determine which factors affect the refractive outcome of hyperopic lamellar keratoplasty. SETTING: Jules Stein Eye Institute and Department of Ophthalmology, UCLA, Los Angeles, California, USA. METHODS: This retrospective study comprised 38 consecutive eyes of 25 patients with naturally occurring hyperopia who had automated lamellar keratoplasty by one surgeon. Mean attempted correction was 3.80 diopters (D) (range of 1.50 to 6.00 D); 34 eyes were followed for 3 months. The effect of applanation lens diameter, keratometry, age, corneal thickness, absolute flap thickness in microns, thickness of the posterior lamellae in microns, and flap thickness as a percentage of corneal thickness were determined using multivariate linear regression. RESULTS: With current nomograms, mean undercorrection 3 months after hyperopic lamellar keratoplasty was 1.26 D +/- 0.91 (SD); 14 of 34 eyes were within +/- 1.00 D of the attempted correction. The best predictive factors of achieved correction were applanation lens diameter and absolute flap thickness in microns, which accounted for 54% of the variability in outcome. Keratometry, corneal thickness, and flap thickness as a percentage of corneal thickness had no significant additional predictive value. CONCLUSION: The refractive outcome of hyperopic lamellar keratoplasty was primarily determined by applanation lens diameter and absolute flap thickness in microns. Current nomograms suggest that flap thickness as a percentage of corneal thickness is a major determinant of effect, but this factor appears unimportant to the refractive effect of hyperopic lamellar keratoplasty. We hypothesize that it is slight swelling of the anterior corneal stroma rather than the bulging of the posterior cornea that causes the hyperopic correction in hyperopic lamellar keratoplasty.

Adult↗
PubMed1999

Excimer ablation design and elliptical transition zones.

PURPOSE: To describe the rationale behind elliptical and other transition designs used with the excimer laser. SETTING: Casey Eye Institute, Oregon Health Sciences University, Portland, Oregon, USA. METHODS: Ablation zone designs were analyzed for the number of transition points for myopia and hyperopia. The advantages and disadvantages of elliptical transition zones are demonstrated graphically, with an emphasis on smooth ablation zone design to maximize the optics and biologic tolerance by the eye. RESULTS: The use of an individualized elliptical transition maximizes a circular effective optical zone and can enhance the smoothness of the transition zone while minimizing excessive tissue removal. CONCLUSION: Elliptical transition zones may improve the optics and biologic tolerance of excimer laser treatments.

Cornea↗
PubMed1999

Piggyback posterior chamber multifocal intraocular lenses in anisometropia.

A 63-year-old white man with anisometropic hyperopia presented with cataract in both eyes. He had uneventful temporal limbal phacoemulsification with intracapsular placement of a multifocal 3-piece silicone intraocular lens (IOL) in his right eye (model SA-40N, Allergan, Inc.). One week later, 2 intracapsular 3-piece silicone IOLs (1 monofocal backward, Allergan model SI-40NB; 1 multifocal in front, Allergan model SA-40N) were implanted in his left eye. At 8 days postoperatively, uncorrected visual acuity was 20/20 for distance and J1 for near vision in the right eye and 20/30 and J2, respectively, in the left. These values remained constant until the patient was seen 7 months postoperatively. Power calculation and insertion order of the piggyback IOLs were considered.

Anisometropia↗
PubMed2000

Apical nodular subepithelial corneal scar after retreatment in hyperopic photorefractive keratectomy.

PURPOSE: To report a complication, apical nodular subepithelial corneal scar, that can occur after hyperopic photorefractive keratectomy (PRK) retreatment. SETTING: Istanbul University Eye Research Center, Istanbul, Turkey. METHODS: Twelve eyes of 6 patients with apical nodular subepithelial corneal scar were retrospectively studied. Mean age of the 5 men and 1 woman was 30.2 years +/- 5.4 (SD). All eyes had hyperopic PRK retreatment for regression 9.5 +/- 1.44 months after primary hyperopic PRK. Mean spherical equivalent refraction of the residual hyperopia before retreatment was +4.67 +/- 0.81 diopters (D). All patients had a corneal haze grade of less than 1+. Hyperopic PRK retreatment was performed with a 193 nm excimer laser (Chiron Technolas Keracor 116). RESULTS: Apical nodular subepithelial corneal scars developed within the first month of hyperopic PRK retreatment and progressed until the third month in 12 eyes of 6 patients. The lesion was round and symmetrical in both eyes, smaller than 2.0 mm, and centrally located. During the mean 40.66 +/- 2.46 month follow-up, the lesion did not change in size or density. Mean spherical equivalent refraction after retreatment was 2.88 +/- 0.88 D (range +1.50 to +4.00 D) at 1 month and +4.36 +/- 1.83 D at last follow-up. Refraction was unmeasurable in 3 eyes. Five eyes lost 1 line of best spectacle-corrected visual acuity and 7 eyes, 2 or more lines. The surface regularity indexes were higher than 2.00 in all the eyes. CONCLUSION: Hyperopic PRK retreatment may cause the sight-threatening complication of apical nodular subepithelial corneal scar. This complication behaves unlike corneal haze and does not resolve spontaneously over time.

Adult↗
PubMed1999

Continuous-wave diode laser thermokeratoplasty: first clinical experience in blind human eyes.

PURPOSE: To evaluate the safety and stability of laser thermokeratoplasty (LTK) with a continuous-wave diode laser in blind human eyes and to optimize parameters for a study in sighted eyes. SETTING: Department of Ophthalmology, Medical University Lübeck, Germany. METHODS: A continuous-wave diode laser was set to emit radiation with a wavelength of 1.854 microns (Group 1, n = 4) or 1.870 microns (Group 2, n = 4) and 100 to 150 mW power for 10 seconds. A focusing handpiece was coupled with an application mask and fixed by partial vacuum to the conjunctiva or cornea. The radiation was focused into the corneal stroma between 400 and 600 microns in Group 1 and set to 1000 microns in Group 2. Eight (Group 1, single ring) or 16 (Group 2, double ring) coagulations were applied. RESULTS: The refractive change increased with higher laser power and smaller ring diameters. Two rings of coagulations provided higher and more stable refractive changes of up to 5.66 diopters (D) than a single ring. The refractive effect stabilized between 3 and 6 months postoperatively. At 1 year, mean refractive change was +0.99 D +/- 0.39 (SD) in Group 1 and +2.32 +/- 2.24 D in Group 2. Extensive endothelial damage occurred in Group 1 but was minimal in Group 2. CONCLUSIONS: Diode LTK was used to treat hyperopia safely and effectively. Regression occurred mainly in the first 3 postoperative months. With a wavelength of 1.870 microns, corneal endothelial damage was limited.

Adult↗
PubMed1999

Intraocular lens power calculation after decentered photorefractive keratectomy.

A 59-year-old patient who had photorefractive keratectomy (PRK) to correct high unilateral myopia developed a progressive nuclear cataract. Phacoemulsification and intraocular lens (IOL) implantation were performed. However, determination of IOL power using automated keratometry and computerized videokeratography was not successful in this case of high axial myopia because of a decentered ablation zone, resulting in too-steep keratometric readings. Postoperative hyperopia could only be corrected by an IOL exchange. Because it may not be possible to determine the exact keratometric values for IOL calculation after PRK, subtracting the change in refraction induced by PRK from the preoperative keratometric readings might have been more accurate in this patient.

Cataract↗
PubMed2001

Risk factors for open-angle glaucoma: a case-control study.

The objective of this study was to identify possible risk factors associated with open-angle glaucoma (OAG). A case-control study included patients seen at an ophthalmologic clinic. Cases were all consecutive new patients with either unilateral or bilateral OAG detected during the study period. Controls were a random sample of all other patients aged 30 or more, seen in the same department in the same period. Data on demographic, anthropometric and diet habits as well as medical characteristics were collected from 144 patients by medical examination and interview. The study took place at the University Department of Ophthalmology and general private practice of ophthalmology, both in the city of Kinshasa. Forty consecutive patients with OAG and 104 controls were chosen randomly between all consecutive non OAG patients. Odds ratio (OR) are presented for the relation between OAG and age, sex, ethnicity, family history of glaucoma, the length of stay in Kinshasa, body mass index, hypertension, diabetes mellitus, cigarette smoking, alcohol, diet habits. Adjusted odds ratio resulting from stepwise logistic regression was employed. Results indicate: family history of glaucoma (OR, 18; 95% CI, 5.80-59.00; P < 0.001), age (OR, 1.05; 95% CI, 1.01-1.09; P = 0.025), body mass index (OR, 1.09; 95% CI, 1.01-1.18; P = 0.05), hyperopia (OR, 2.9; 95% CI, 1.05-7.08; P = 0.03), Mongo ethnic group (OR, 3.5; 95% CI, 1.11-12.20; P = 0.03) and consumption of rice (OR, 4.6; 95% CI, 1.65-12.20; P = 0.004) conferred a significantly greater risk of OAG. This study seems confirm that Mongo ethnic group is associated with an increased risk of OAG.

Adult↗
PubMed2005

Refractive errors in infancy predict reduced performance on the movement assessment battery for children at 3 1/2 and 5 1/2 years.

We have previously reported that significant hyperopia at 9 months predicts mild deficits on visuocognitive and visuomotor measures between 2 years and 5 years 6 months. Here we compare the motor skills of children who had been hyperopic in infancy (hyperopic group) with those who had been emmetropic (control group), using the Movement Assessment Battery for Children (Movement ABC). Children were tested at 3 years 6 months (hyperopic group: 47 males, 63 females, mean age 3 y 7 mo, SD 1.6 mo; control group: 61 males, 70 females, mean age 3 y 7 mo, SD 1.2 mo) and at 5 years 6 months (hyperopic group: 43 males, 56 females, mean age 5 y 4 mo, SD 1.7 mo; control group: 51 males, 62 females, mean age 5 y 3 mo, SD 1.6 mo). The hyperopic group performed significantly worse at both ages, overall and on at least one test from each category of motor skill (manual dexterity, balance, and ball skills). Distributions of scores showed that these differences were not due to poor performance by a minority but to a widespread mild deficit in the hyperopic group. This study also provides the first normative data on the Movement ABC for children below 4 years of age, and shows that it provides a useful measure of motor development at this young age.

Age Factors↗
PubMed1990

Developing eyes that lack accommodation grow to compensate for imposed defocus.

The eyes of growing chicks adjust to correct for myopia (eye relatively long for the focal length of its optics) or hyperopia (eye relatively short for the focal length of its optics). Eyes made functionally hyperopic with negative spectacle lenses become myopic and long, whereas eyes made functionally myopic with positive spectacle lenses become hyperopic and short. We report here that these compensatory growth adjustments occur not only in normal eyes but also in eyes unable to accommodate (focus) because of lesions to the Edinger-Westphal nuclei. Thus, at least in chicks, accommodation is not necessary for growth that reduces refractive errors during development, and may not be necessary for the normal control of eye growth.

Accommodation, Ocular↗
PubMed2001

Pigmented striae of the anterior lens capsule and age-associated pigment dispersion of variable degree in a group of older African-Americans: an age, race, and gender matched study.

PURPOSE: To investigate pigmented striae of the anterior lens capsule in African-Americans, a potential indicator of significant anterior segment pigment dispersion. METHODS: A group of 40 African-American subjects who exhibited pigmented lens striae (PLS) were identified from a non-referred, primary eye care population in Chicago, IL, USA. These subjects were then compared to an age, race, and gender matched control group relative to refractive error and the presence or absence of diabetes and hypertension. RESULTS: The PLS subjects (mean age = 65.4 +/- 8.8 years, range = 50-87 years) consisted of 36 females and 4 males. PLS were bilateral in 36 (85%) of the 40 subjects. Among the eyes with PLS, 21 (55%) of 38 right eyes and 22 (61%) of 36 left eyes also had significant corneal endothelial pigment dusting, commonly in the shape of a Krukenberg's spindle. Ten (25%) of the PLS subjects had either glaucoma or ocular hypertension (7 bilateral, 3 unilateral). The presence of trabecular meshwork pigment varied from minimal to heavy. The mean +/- SD (range) refractive error of the PLS right eyes was +1.61 +/- 1.43D (-1.50 to +5.00D) and +1.77 +/- 1.37D (-1.00 to +5.00D) for the left eyes. Based on these data, the PLS right eyes were +1.63D (Student's t, p = 0.0001; 95% CI = +0.82 to +2.44D) more hyperopic on average than the control right eyes, and the PLS left eyes were +1.77D (p = 0.0001; 95% CI = +0.92 to +2.63D) more hyperopic on average than the control left eyes. Trend analysis showed a gradually increasing likelihood of PLS with increasing magnitude of hyperopia in both eyes (Mantel-Haenszel chi-square, p = 0.001). Among PLS subjects, 24 (60%) of 40 were hypertensive and 9 (23%) of 40 were diabetic. However, these proportions were not significantly different (two-tailed Fisher's exact test; hypertension: p = 0.30; diabetes: p = 0.70) from the randomly selected controls. CONCLUSIONS: Among our African-American group, which consisted predominately of females >50 years of age, the likelihood of PLS increased with increasing hyperopic refractive error. This finding is consistent with the possibility that PLS may, in some circumstances, indicate a significant pigment dispersal process due to iris-lens rubbing that may be associated with crowding of anterior segment structures. Additional study is warranted to further assess the nature of PLS, their precise relationship with an age-related pigment dispersal process, and their true significance as a risk factor for development of glaucoma.

Adolescent↗
PubMed2002

Ultrasound biomicroscopy of the anterior segment of the enucleated chicken eye during accommodation.

Ultrasound biomicroscopy produces real-time two-dimensional images of ocular structures measured non-invasively. Given recent work which shows that lenses from myopic eyes show shorter focal lengths and reduced accommodative amplitudes compared with controls, this study was undertaken to determine the structural characteristics of the anterior segment of chicken eyes during accommodation using the ultrasound biomicroscope (UBM). Form-deprivation myopia and hyperopia were induced in hatching chicks by the application of either translucent or +15 D defocus goggles. After 7 days, eyes were enucleated and ultrasound biomicrographs of the eye, at rest and during ciliary nerve-stimulated accommodation, were collected. For all eyes, accommodation was associated with a decrease in anterior chamber depth, an increase in lenticular thickness and a steepening of the front lenticular surface curvature. Changes related to refractive error were more difficult to detect. Myopic eyes showed deeper anterior chamber depths and differences in lenticular thicknesses just above the resolution limit for detection. In +15 D lens-treated eyes, anterior chamber differences were opposite but smaller, just at the limit of resolution, while differences in mean lenticular thickness were not resolvable at a pixel or above. The UBM is a good tool for measuring robust changes during accommodation, but is limited in its ability to detect subtle changes associated with experimentally induced ametropias.

Accommodation, Ocular↗
PubMed2002

Differential refractive susceptibility to sustained nearwork.

PURPOSE: A possible role for nearwork-induced transient myopia (NITM) (i.e. transient myopia at distance following sustained nearwork) in the development and/or progression of permanent myopia has been suggested. If certain refractive groups are more susceptible to NITM than others, then measures may be implemented to prevent or retard the occurrence of myopia in these individuals. In a recent study (Ciuffreda and Wallis, 1998), it was found that young-adult late-onset myopes (LOM) and early-onset myopes (EOM) were highly susceptible to this NITM accommodative after-effect, while emmetropes (EMMs) were only moderately susceptible, and hyperopes (HYP) were particularly insusceptible, following short periods (10 min) of sustained nearwork at a very close distance (20 cm, 5 D). In the current study, this was extended to encompass a much longer period of nearwork under more naturalistic conditions. METHODS: Young-adult subjects (n = 16) performed a reading task for a continuous period of 4 h at their habitual working distance under naturalistic conditions, i.e. binocular viewing with blur-related visual feedback present. Distance refractive state (binocular viewing) was assessed objectively using a Canon R-1 autorefractor immediately before (pre-task), every hour during the task, and immediately after (post-task) to assess NITM and its subsequent decay to pre-task refractive levels. Subjects were divided into the four refractive subgroups as above, which were each of equal size (n = 4). RESULTS: The NITM was induced in all subjects, except for the hyperopes in which there was a hyperopic refractive shift. The LOMs (0.12 D) and EOMs (0.13 D) were highly susceptible, while the HYPs were especially insusceptible (0.44 D hyperopia), and the EMMs were only moderately susceptible (0.09 D). CONCLUSIONS: The present study extended our earlier investigation by demonstrating the differential refractive susceptibility over a longer period of sustained nearwork, which may be the result of reduced sympathetic activation. It has been speculated that NITM may be a factor in myopigenesis, with a possible mechanism being time-integrated increased retinal defocus from NITM at both distance and near, in conjunction with the normal lag of accommodation during sustained nearwork, thereby causing axial elongation. Hence, a future longitudinal investigation specifically targeting this retinal defocus hypothesis is warranted.

Accommodation, Ocular↗
PubMed2004

The relationship between intraocular pressure and refractive error adjusting for age and central corneal thickness.

PURPOSE: To investigate the relationship between intraocular pressure (IOP) and refractive errors after adjusting for age, central corneal thickness (CCT), and other related factors. METHODS: IOP, CCT and refractive errors were measured in the right eyes of 1855 subjects, aged 40-82 years, in a cross-sectional study design. Subjects were divided into groups by refractive status: hyperopia, emmetropia, mild myopia, moderate myopia, or high myopia. With adjustments for age, CCT, blood pressure, obesity, education, hypertension, diabetes, and smoking status, IOP was estimated for each refractive status using a general linear model. RESULTS: IOP increased with advancing degrees of myopia, even after adjustment for age, CCT, and other related factors (p = 0.011). Estimated IOP of moderate myopia was significantly higher than that of emmetropia (p = 0.022). CONCLUSIONS: Our results confirm the positive association between IOP and increasing degrees of myopia. This finding would support the hypothesis that the relationship between glaucoma and myopia might be pressure mediated.

Adult↗
PubMed2004

Prevalence of refractive errors in teenage high school students in Singapore.

We aimed to study the prevalence of refractive conditions in Singapore teenagers. Grade 9 and 10 students (n = 946) aged 15-19 years from two secondary schools in Singapore were recruited. The refractive errors of the students' eyes were measured using non-cycloplegic autorefraction. Sociodemographic data and information on risk factors for myopia (such as reading and writing) were also obtained using an interviewer-administered questionnaire. The prevalence of refractive conditions was found to be: myopia [spherical equivalent (SE) at least -0.50 D] - 73.9%, hyperopia (SE at least +0.50 D) - 1.5%, astigmatism (cylinder at least -0.50 D) - 58.7% and anisometropia (SE difference at least 1.00 D) - 11.2%. After adjusting for age and gender, currently doing more than 20.5 h of reading and writing a week was found to be positively associated with myopia [odds ratio 1.12 (95% CI 1.04-1.20, p = 0.003)], as was reading and writing at a close distance and a better educational stream. The prevalence of myopia (73.9%) in Singapore teenagers is high. Current reading and writing habits, reading at close distances and a better educational stream are possible risk factors for myopia.

Adolescent↗
PubMed2002

Headaches associated with refractive errors: myth or reality?

INTRODUCTION: Headache and refractive errors are very common conditions in the general population, and those with headache often attribute their pain to a visual problem. The International Headache Society (IHS) criteria for the classification of headache includes an entity of headache associated with refractive errors (HARE), but indicates that its importance is widely overestimated. OBJECTIVES: To compare overall headache frequency and HARE frequency in healthy subjects with uncorrected or miscorrected refractive errors and a control group. METHODS: We interviewed 105 individuals with uncorrected refractive errors and a control group of 71 subjects (with properly corrected or without refractive errors) regarding their headache history. We compared the occurrence of headache and its diagnosis in both groups and assessed its relation to their habits of visual effort and type of refractive errors. RESULTS: Headache frequency was similar in both subjects and controls. Headache associated with refractive errors was the only headache type significantly more common in subjects with refractive errors than in controls (6.7% versus 0%). It was associated with hyperopia and was unrelated to visual effort or to the severity of visual error. With adequate correction, 72.5% of the subjects with headache and refractive error reported improvement in their headaches, and 38% had complete remission of headache. Regardless of the type of headache present, headache frequency was significantly reduced in these subjects (t = 2.34, P =.02). CONCLUSIONS: Headache associated with refractive errors was rarely identified in individuals with refractive errors. In those with chronic headache, proper correction of refractive errors significantly improved headache complaints and did so primarily by decreasing the frequency of headache episodes.

Adolescent↗
PubMed1987

[Refractive errors in visually handicapped children].

Aside from hereditary juvenile macular dystrophy (Stargardt's disease), the author observed a significant increase in the incidence of spheric and astigmatic refractive errors in a further six hereditary or congenital deformities with poor vision. A shift toward myopia was seen in cases of coloboma, both of the optic nerve head as well as of the macular region, and in cases of macular aplasia and hypoplasia. A shift toward hyperopia was found in complete and ocular albinism, in retinitis pigmentosa and congenital achromatopsia. This hyperopic shift is in contradiction to the hypothesis that myopia can be deprivation-induced. It is assumed that a disturbance of visual stimulation early in life can disrupt emmetropization and thus induce the eye to become either myopic or hyperopic, in combination with a high incidence of astigmatism. This disturbance of visual stimulation may be due to clouding of the dioptric media, though equally to congenital or hereditary defects in the retina or the visual pathways of visual cortex.

Adolescent↗
PubMed2000

Good visual function in posterior microphthalmos.

Posterior microphthalmos is a rare condition in which the anterior segment is normal in size and configuration, but the posterior segment is reduced in size; this results in axial hyperopia and retinal folding. Patients have decreased vision that is caused by posterior segment abnormalities, high refractive error, and amblyopia. We present a case of posterior microphthalmos in which retinal function was relatively intact and visual loss was believed to be primarily caused by refractive error and amblyopia. After treatment, the child's visual acuity and school performance improved. This case emphasizes the need for careful examination, refraction, and follow-up for these children because their visual potential may be reasonably good.

Amblyopia↗
PubMed1998

Hereditary pigmented paravenous chorioretinal atrophy.

Pigmented paravenous chorioretinal atrophy (PPCRA) is a rare disorder which is diagnosed primarily because of the typical fundoscopic appearance of retinal pigment epithelial (RPE) atrophy and clumping in a paravenous distribution. A mildly affected and asymptomatic 54-year-old mother and her mildly affected daughter and severely affected son presented with pigmented paravenous chorioretinal atrophy. The severely affected (proband) 28-year-old man manifested the characteristic paravenous chorioretinal atrophy with pigment clusters in both eyes with macular involvement. Besides the characteristic fundus picture, he also had chronic angle closure glaucoma. His 23-year-old sister presented with unilateral involvement. Her right eye showed focal perivenular retinal pigment epithelial hyperplasia at the 2 o'clock position and dilated, tortuous retinal veins, while her left eye had only dilated and tortuous retinal veins. Both patients were hyperopic. Their mother had an area of chorioretinal atrophy in one eye near a retinal vein. The scotopic ERG responses were markedly abnormal in the male patient, while his sister had a mild decrease in amplitude of both a and b waves in both eyes. One of the children of an unaffected family member was found to have dilated and tortuous retinal veins and hyperopia (III-12). To our knowledge, this is the fourth report of familial occurrence of pigmented paravenous chorioretinal atrophy. The present pedigree is compatible with X-linked recessive or dominant inheritance.

Adult↗