ISSN:1040-5488    

出版商:OVID    

年代:2003

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:2003

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:2003

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Background.Choroidal neovascularization (CNV) occurs in association with a variety of retinochoroidal disorders. However, it is not normally known to form after an untreated macular hole.Case Report.A 75-year-old black male presented with a 12-month history of visual loss in his right eye. Funduscopy showed a full-thickness macular hole in the right eye. No treatment was recommended because the decrease in vision appeared to be long standing. Fourteen months later, the patient was noted to have a subretinal hemorrhage superior to the macular hole. Fluorescein angiography revealed an adjacent choroidal neovascular membrane, and focal krypton laser photocoagulation was performed. Recurrent CNV was noted 6 months later, and additional photocoagulation was performed.Discussion.This case represents the 10th case reported of CNV with a full-thickness macular hole and only the second of a patient with an untreated macular hole and no other risk factors for CNV.

ISSN:1040-5488    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Purpose.To determine the refractive state of tree shrew eyes using visual evoked potentials (VEP’s) recorded from primary visual cortex and compare the values with those obtained with streak retinoscopy and with an autorefractor.Methods.VEP’s were recorded in seven normal tree shrews and three animals in which ∼5 D of myopia (relative to control eye) was induced by monocular −5 D lens wear. While the animals were awake, refractive correction was measured with an autorefractor before and after cycloplegia (1% atropine and 2.5% phenylepherine). When anesthetized, cycloplegic refractive correction was measured with streak retinoscopy. Then VEP’s were produced with square-wave counterphased (1 Hz) high-contrast checkerboard patterns near the animals’ high spatial frequency cutoff. Spherical lenses (2 D steps) were placed before the eye, and the VEP (average of 128 sweeps) was measured to determine the lens that produced the largest first positive peak (P1).Results.VEP’s were obtained over a broad range of trial lenses. Tuning was narrower when check sizes were small. In normal and control eyes, the P1 amplitude was largest, on average, for a trial lens of (mean ± SD) −0.6 ± 1.6 D (corrected for working distance but not vertex distance). The mean streak retinoscopy value (spherical equivalent at the corneal plane) was 7.0 ± 0.8 D, and mean autorefractor values were 4.0 ± 1.1 D (cycloplegic) and 3.7 ± 1.2 D (noncycloplegic). In the eyes that compensated for a −5 D lens, the largest P1 values occurred with lenses with a power of −6.3 ± 3.2 D. Thus, the VEP measure showed a similar treated vs. control eye difference as did streak retinoscopy (treated eyes, 4.7 ± 0.4 D myopic) and the autorefractor (treated eyes, 4.8 ± 0.5 D myopic).Conclusions.Normal tree shrew eyes are approximately emmetropic. The hyperopic values obtained with streak retinoscopy and the autorefractor are consistent with the presence of a “small-eye artifact” in tree shrews. Eyes that have compensated for a −5 D lens are myopic by approximately the value of the lens.

ISSN:1040-5488    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Background.Tear ascorbate is important for corneal health. A rapid and simple method for measurement of ascorbate in tears is needed, and adequate knowledge of physiological variation of tear ascorbate is important to facilitate comparative studies of the effect of, for example, contact lens wear and environmental conditions and stresses. However, there are currently no data on physiological variation of tear ascorbate. This study validated a simple and speedy method for tear ascorbate and investigated between-eye and between-day variation in tear ascorbate in healthy young adults.Methods.Yawn-induced reflex tears were collected from 32 healthy Hong Kong Chinese subjects and measured by both high-performance liquid chromatography (HPLC) and by an enzyme-linked colorimetric method known as FRASC (total ferric reducing (antioxidant) activity and ascorbate concentration measurement). For between-eye variation, yawn reflex tears were collected from each eye of the same 32 healthy subjects, and ascorbate was measured using HPLC; in a separate experiment for between-day variation, tears were collected on two separate days from 14 subjects, and ascorbate was measured by FRASC.Results.Both HPLC and FRASC showed high precision, and results obtained using FRASC were not statistically different from those using HPLC; mean ± SD were, respectively, 18.5 ± 4.4 &mgr;M and 18.5 ± 4.8 &mgr;M for HPLC and FRASC methods (p = 0.943). No significant between-eye difference in tear ascorbate was found (p = 0.386), and no significant between-day variation was found overall: mean ± SD ascorbate was 20.0 ± 6.2 &mgr;M on day 1 and 19.3 ± 6.8 &mgr;M on day 2 (p = 0.772). However, between-day variation was large in seven of 14 subjects.Conclusion.FRASC is an acceptable alternative to HPLC for measurement of tear ascorbate. Tears for ascorbate investigation can be collected from either eye or, if necessary, from both eyes and pooled. However, tear ascorbate may vary widely from day to day in the same individual. The reasons for this variation require further study but may relate to differences in ascorbate supply or demand within the precorneal tear layer.

ISSN:1040-5488    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Purpose.Outstanding improvements in vision can theoretically be expected using contact lenses that correct monochromatic aberrations of the eye. Imperfections in such correction inherent to contact lenses are lens flexure, translation, rotation, and tear layer effects. The effects of pupil size and accommodation on ocular aberration may cause further difficulties. The purpose of this study was to evaluate whether nonaxisymmetric soft contact lenses could efficiently compensate for higher-order aberrations induced by keratoconus and to what extent rotation and translation of the lens would degrade this perfect correction..Methods.Height topography data of nine moderate to severe keratoconus corneas were obtained using the Maastricht Shape Topographer. Three-dimensional ray tracing was applied to each elevation topography to calculate aberrations in the form of a phase error mapping. The effect of a nonaxisymmetric soft contact lens tailored to the corneal aberrations was simulated by adding an opposite phase error mapping that would theoretically compensate all corneal-induced optical aberrations of the keratoconus eyes. Translation (0.25, 0.5, 0.75, and 1.0 mm) and rotation (2.5°, 5.0°, 7.5°, and 10°) mismatches were introduced. The modulation transfer function (MTF) of each eye with each displaced correction and with various pupil sizes (3, 5, and 7 mm) was deduced from the residual phase error mapping. A single performance criterion (mtfA) was calculated as the area under the MTF over a limited spatial frequency range (5 to 15 periods per degree). Finally, the ratio (RmtfA) of corrected mtfA over uncorrected mtfA provided an estimate of the global enhancement in contrast sensitivity with the customized lens.Results.The contrast improvement ratios RmtfA with perfectly located lenses were for an average pupil size of 4.5 mm between 6.5 and 200. For small translation errors (0.25 mm), RmtfA ranged between 2 and 7. The largest lens translation tested (1 mm) often resulted in poorer performance than without correction (RmtfA <1). More than threefold improvements were achieved with any of the angular errors experimented. RmtfA values showed significant variations for pupil diameters between 3 and 7 mm..Conclusions.Three-dimensional aberration-customized soft contact lenses may drastically improve visual performance in patients with keratoconus. However, such lenses should be well positioned on the cornea. In particular, translation errors should not exceed 0.5 mm. Angular errors appeared to be less critical. It is further questioned whether the visual system is able to adapt to variations in optical performance of the correctionin situdue to lens positioning and pupil size.

ISSN:1040-5488    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Purpose.To report the clinical course for patients with intermittent exotropia.Methods.The clinical records of patients diagnosed with intermittent exotropia from 1983 to 1991 who had at least 4 years of follow-up were reviewed. All patients with neurological or medical abnormalities, developmental delays, ocular disease, or having strabismus surgery during the follow-up period were excluded.Results.Of the 468 records reviewed, 73 met the inclusion criteria. Forty-four patients were female, and 29 were male. Fifty-two patients had basic intermittent exotropia, 11 patients had divergence excess intermittent exotropia, and 10 patients had convergence insufficiency intermittent exotropia. The mean age at initial visit was 20 years (range, 1 to 63 years). The mean follow-up was 10 years (range, 4 to 23 years). Four patients had amblyopia of 20/30 or worse, nine patients had a vertical deviation in the primary position, and 10 patients had undergone extraocular muscle surgery before coming to our clinic. Sixty patients received some form of treatment during follow-up. The mean stereoacuity at the initial and final visits were 59 and 70 s arc, respectively. The initial mean spherical equivalent refraction was −0.48 D and increased to −1.15 D at the end of the study. The mean exodeviation changed from 17.2 &Dgr; at distance and 17.6 &Dgr; at near at the initial visit to 13.7 &Dgr; at distance and 13.5 &Dgr; at near at the final visit. At the initial visit, 63 patients were exotropic and 10 patients were either heterophoric or orthophoric at distance, whereas, 60 patients were exotropic and 13 patients were either heterophoric or orthophoric at near. At the final visit, 37 patients were exotropic and 36 patients were either heterophoric or orthophoric at distance whereas 33 patients were exotropic and 39 were either heterophoric or orthophoric at near. One patient was esotropic at near at the last visit. Changes in the size and quality of the exodeviation, although statistically significant (p < 0.001), were not associated with any specific treatment regimen or with longer periods of follow-up. Measurements exhibited a regression toward the mean.Conclusions.Intermittent exotropia improved for many patients quantitatively and qualitatively over time. That the improvement was unrelated to any treatment and length of follow-up suggests that the changes at least quantitatively are not associated with any physiologic process and may be due, in part, to regression toward the mean.

ISSN:1040-5488    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

Purpose.To compare visual acuity results obtained using the Lea Symbols chart with visual acuity results obtained with the Bailey-Lovie chart in school-aged children and adults using a within-subjects comparison of monocular acuity results.Methods.Subjects were 62 individuals between 4.5 and 60 years of age, recruited from patients seen in five optometry clinics. Each subject had acuity of the right eye and the left eye tested with the Lea Symbols chart and the Bailey-Lovie chart, with order of testing varied across subjects. Outcome measures were monocular logarithm of the minimum angle of resolution (logMAR) visual acuity and inter-eye acuity difference in logMAR units for each test.Results.Correlation between acuity results obtained with the two charts was high. There was no difference in absolute inter-eye acuity difference measured with the two acuity charts. However, on average, Lea Symbols acuity scores were one logMAR line better than Bailey-Lovie acuity scores, and this difference increased with worse visual acuity.Conclusions.The Lea Symbols chart provides a measure of inter-eye difference that is similar to that obtained with the Bailey-Lovie chart. However, the monocular acuity results obtained with the Lea Symbols chart differ from those obtained with the Bailey-Lovie chart, and the difference is dependent on the individual’s absolute level of visual acuity.

ISSN:1040-5488    

出版商:OVID    

年代:2003

数据来源: OVID