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At least 1,693 records · Page 94Linked to original sources
PubMed1992

Shape of the myopic eye as seen with high-resolution magnetic resonance imaging.

We have obtained multislice magnetic resonance (MR) images of the eye and calculated ocular dimensions along the three cardinal axes: antero-posterior (A-P), equatorial, and vertical. We found no difference in the shape of hyperopic (average refractive error: +3.72 D) and emmetropic eyes, both of which had an equatorial diameter longer than the A-P and vertical diameters. Myopic eyes (average refractive error: -6.54 D) were larger than hyperopic eyes, and most had the same spheroelliptical shape as that of the emmetropic and hyperopic eyes. The results suggest that during myopic progression an overall enlargement or a radial volume expansion has occurred.

Adult↗
PubMed1992

To use or not to use the refractive correction along with hand-held magnifiers.

Equivalent viewing power (EVP), field of view, and working distance (WD) were calculated for 4 different magnifier equivalent powers, four magnifier-to-eye distances, and for uncorrected spherical ametropias varying from +20.00 to -20.00 D in 0.25 D steps. Results show that the various viewing conditions which arise (depending on whether or not the refractive correction is worn) can differ considerably. The uncorrected unaccommodating myope has a greater EVP than the equivalent power of the magnifier if he chooses a magnifier-to-eye distance shorter than the focal length of the magnifier. In this situation, field of view is also enhanced. The uncorrected unaccommodating hyperope using a magnifier-to-eye distance longer than the focal length of the magnifier achieves a stronger EVP than the equivalent power of the magnifier. However, field of view is then reduced. For the uncorrected unaccommodating spherical ametrope, the use of a magnifier-to-eye distance corresponding to the focal length of the magnifier seems to be a good compromise between EVP, field of view, and working distance.

Eyeglasses↗
PubMed1997

Optometric findings in velocardiofacial syndrome.

Velocardiofacial syndrome (VCFS) is a congenital genetically determined condition with skeletal, heart, and facial anomalies. Almost all children have learning problems, despite an often normal or above average IQ. We have examined 10 children with a prior diagnosis of VCFS. All were mildly to moderately hyperopic. Most had poor accommodation, and convergence was clinically poor. About 30% had tortuous retinal vessels. VCFS may be detected in the optometry clinic, and optometric management may ameliorate the learning problems in some cases.

Abnormalities, Multiple↗
PubMed1998

Contrast sensitivity with soft contact lenses compensated for spherical aberration in high ametropia.

BACKGROUND: In optical systems, it is usual to compensate for longitudinal spherical aberration. In order to increase image quality, lens surfaces can be made aspheric to bring all object light rays into focus at the image plane. Theoretically, soft contact lenses with high power and spherical surfaces show significant amounts of spherical aberration. The use of spherical aberration-free soft contact lenses could therefore improve retinal image quality in the case of high ametropia. However, because of ocular aberration, accommodation effects, pupil dynamics, contact lens flexure, and positioning, the computation of the spherical aberration induced when a contact lens is placed on the eye is complicated. METHODS: In this study, the spatial contrast sensitivity (CS) of 61 high ametropes wearing soft contact lenses with, and without, in-air spherical aberration compensation is measured. RESULTS: A slightly better overall performance was found with the standard lenses. There was no significant influence by the type of ametropia, age, and gender. If individual results are considered, clinically significant differences between the two lens groups are observed in approximately 30% of the cases. CONCLUSIONS: It seems that correcting in-air soft contact lens spherical aberration systematically is of no clinical interest. However, selective manipulation of spherical aberration could, in high power soft contact lenses, significantly improve CS in individuals.

Adolescent↗
PubMed2000

A method for using relay lenses with display monitors for vision testing at far and near.

Resolution limitations preclude the use of display monitors for near testing of acuity and contrast sensitivity. Relay lenses can form minified aerial images of the display at any given near viewing distance, but the image will differ in spatial frequency from the display. Equations are presented that can be used to specify the far- and near-viewing distances and the necessary focal length of a lens so that the display and its near aerial image have identical spatial frequencies when viewed by a subject at a fixed location. Modulation transfer function (MTF) calculations show that achromatic doublets will not degrade the resolution across a 300-mm wide display, thereby providing the versatility of display monitors for near vision testing.

Computer Terminals↗
PubMed2000

Spasm of the near reflex mimicking deteriorating accommodative esotropia.

PURPOSE: To describe a patient with accommodative esotropia who developed spasm of the near reflex. CASE REPORT: A 6-year-old girl with a history of successfully treated refractive, accommodative esotropia suddenly developed spasm of the near reflex after the death of a relative. The condition resolved after 2 months. CONCLUSION: Spasm of the near reflex should be considered in children with accommodative esotropia who seem to deteriorate and become esotropic once again while wearing their hyperopic glasses.

Accommodation, Ocular↗
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↗
PubMed2004

The prevalence of astigmatism in Taiwan schoolchildren.

PURPOSE: To understand the prevalence and distribution of astigmatism in schoolchildren in Taiwan, we analyzed and compared the nationwide survey data in 1995 and 2000. METHODS: A total of 11,175 students were enrolled in 1995, and 10,878 students were enrolled in 2000. The refractive status of each student was measured with an autorefractor during cycloplegia and rechecked with retinoscopy. RESULTS: About half of schoolchildren (57.5% in 1995 and 49.0% in 2000) had no astigmatism (<0.5 D). About one third of schoolchildren's astigmatism was <1 D (27.9% vs. 32.6%). Eleven percent of schoolchildren in 1995 and 13% in 2000 had astigmatism between 1.0 and 2.0 D. Less than 2% of students had astigmatism >3.0 D (1.3% in 1995 and 1.8% in 2000). Most astigmatism was with-the-rule: 83.3% in 1995 and 89.9% in 2000. Only 16.6% of children in 1995 and 9.7% in 2000 had against-the-rule astigmatism. Very little astigmatism was oblique (0.1% in 1995 and 0.4% in 2000). The rate of myopic astigmatism increased with age. In contrast, the rate of hyperopic and mixed astigmatism decreased with age. In addition, the rate of with-the-rule astigmatism increased and the rate of against-the-rule decreased with respect to age, but oblique astigmatism was rather stable with age. CONCLUSIONS: Most schoolchildren had little or no astigmatism. In Taiwan, most astigmatism is <1 D and is myopic with-the-rule astigmatism. There was more myopic astigmatism and with-the-rule astigmatism in 2000 than in 1995.

Adolescent↗
PubMed2004

Oculometric characteristics of extreme hypermetropia in two faroese families.

PURPOSE: To describe and analyze the oculometric features of small eyes with high hypermetropia in two Faroese families, with emphasis on refractive components. METHODS: Members of the two families (N=40; age, 1 to 77 years), including 15 cases of extreme hypermetropia (+7.5 to +19.25 D), had an ophthalmic evaluation including refractometry, keratometry, and axial ocular measurements using A-scan ultrasound. Eye-wall thickness was assessed using B-scan. Nonparametric statistics were used, mainly the Mann-Whitney U test. RESULTS: In the two families, there were six and nine probands, respectively, with hypermetropia more than +7 D and short eyes as defined by axial eye lengths <21 mm. The median corrected visual acuity was 0.4 (range, 0.2 to 0.9). Gross fundus abnormalities were not observed. All 15 had a short posterior segment with a thick eye wall and a relatively thick lens. Furthermore, steep and rather small corneas were present. In one of the families, 70% of the affected had a corneal curvature radius of < or =7.0 mm. Five probands from family 2 were labeled as possibly affected because of hypermetropia and borderline axial length findings (21 to 22 mm). The remaining 20 subjects had visual acuity and oculometric findings within physiologic limits. CONCLUSIONS: The axial measurement features in our series of highly hypermetropic eyes mainly presented as an extension downward from the hypermetropic bottom line of the normal distribution. The axial shortness of the eyes was primarily the result of a short posterior eye segment ("posterior microphthalmos"). A steep cornea was a feature in most small eyes in our series, particularly in one family branch.

Adolescent↗
PubMedDate not supplied

Refractive changes in silicone oil-filled pseudophakic eyes.

PURPOSE: We examined the refractive changes in pseudophakic eyes of patients with idiopathic macular hole treated with silicone oil injection. METHODS: Twenty consecutive eyes of 19 patients with idiopathic macular hole who had undergone successful pars plana vitrectomy using silicone oil tamponade were studied retrospectively. Lensectomy with intraocular lens (IOL) implantation was performed on each patient before vitreous surgery. Five biconvex type IOL models were used. After pars plana vitrectomy and fluid-air exchange, silicone oil was injected to replace the air completely. Macular hole closure was confirmed by optical coherence tomography, and silicone oil removal was performed. Manifest refractions before silicone oil filling, with silicone oil filling, and after silicone oil removal were determined. RESULTS: A mean hyperopic shift +/- SD in spherical equivalents of +5.69 +/- 1.71 diopters (P < 0.0001) was observed with silicone oil instillation. In contrast, a mean myopic shift +/- SD of -5.63 +/- 1.33 diopters was observed after silicone oil removal (P < 0.0001). The absolute value of the refractive shift showed a strong correlation with the posterior radius of the IOL (r = 0.699, P < 0.0001). CONCLUSION: IOL models with steeper posterior convex curvature result in larger refractive deviations in patients scheduled for silicone oil instillation.

Aged↗
PubMed1976

Management of intermittent esotropia.

Management of patients with intermittent esotropia having either normal or high accommodative convergence to accomodation (AC:A) ratios is discussed. Treatment should be based on liberal use of miotics to build up fusional reserves and use of hyperopic corrections or bifocals or both whenever specifically indicated. Divergent fusional reserve training is time-consuming and the cost/benefit ratio so low that most patients and doctors prefer the former treatment.

Accommodation, Ocular↗
PubMed2003

Loss of vision after laser in situ keratomileusis.

PURPOSE: To research the incidence of visual loss after laser in situ keratomileusis (LASIK). METHODS: We reviewed an extensive review of the literature published by The Ophthalmic Technology Assessment Committee of the American Academy of Ophthalmology regarding the safety and efficacy of LASIK. We also reviewed other recent literature. RESULTS: For low to moderate myopia and astigmatism, LASIK is efficient, safe, and predictable with few eyes losing two or more lines of best-corrected visual acuity (BCVA). For moderate to high myopia, the results are more variable and more eyes lost two or more lines BCVA. In both cases, this BCVA occurred in studies published on or before 1999. CONCLUSION: Serious adverse complications leading to significant visual loss are probably rare. Continued development of microkeratomes and laser technology are continuing to reduce the rare complications that do occur and improve functional outcomes and patient satisfaction.

Humans↗
PubMed2004

Hyperopic photorefractive keratectomy with adjunctive topical mitomycin C for refractive error after penetrating keratoplasty for keratoconus.

OBJECTIVE: To present a case of photorefractive keratectomy (PRK) with adjunctive topical mitomycin C (MMC) in an anisometropic hyperopic patient after penetrating keratoplasty (PKP) for keratoconus. METHODS: Interventional case report, chart review, and literature review. RESULTS: A 43-year-old man with a refraction of +7.00 -4.75 x 125 in the right eye underwent PRK 10 months after PKP for keratoconus. The patient had sutures removed for 3 months and was intolerant of contact lenses. After photoablation, 0.02% MMC was applied to the corneal stromal bed. The patient was followed up daily until the epithelium closed and at 1 week, 1 month, 3 months, and 6 months postoperatively. CONCLUSIONS: To our knowledge, this represents the first reported case of the use of MMC to prevent postoperative haze after PRK for PKP in an eye with keratoconus. MMC (0.02%) applied topically to the cornea immediately after PRK is safe and effective to treat a hyperopic refractive error after PKP and prevent postoperative corneal haze formation without the risks of performing a lamellar flap into an ectatic corneal bed.

Administration, Topical↗