Metrics of retinal image quality predict visual performance in eyes with 20/17 or better visual acuity.

PURPOSE: The purpose of this study is to determine the ability of single-value metrics of retinal image quality of the eye to predict visual performance as measured by high (HC) and low (LC) -contrast acuity at photopic (P) and mesopic (M) light levels in eyes with 20/17 and better visual acuity. METHODS: Forty-nine normal subjects in good health ranging in age from 21.8 to 62.6 with 20/17 or better monocular high-contrast logarithm of the minimum angle of resolution (logMAR) acuity served as subjects. Wavefront error through the 10th Zernike radial order over a 7-mm pupil was measured on each test eye using a custom-built Shack/Hartmann wavefront sensor. For each eye, 31 different single-value retinal image quality metrics were calculated. Visual acuity was measured using HC (95%) and LC (11%) logMAR at photopic (270 cd/m) and mesopic (0.75 cd/m) light levels. To determine the ability of each metric of retinal image quality to predict each type of logMAR acuity (P HC, P LC, M HC, and M LC), each acuity measure was regressed against each optical quality metric. RESULTS: The ability of the metrics of retinal image quality to predict logMAR acuity improved as luminance and/or contrast is lowered. The best retinal image quality metric (logPFSc) accounted for 2.6%, 15.1%, 27.6%, and 40.0% of the variance in P HC, P LC, M HC, and M LC logMAR acuity, respectively. CONCLUSIONS: In eyes with 20/17 and better P HC acuity, P HC logMAR acuity is insensitive to variations in retinal image quality compared with M LC logMAR acuity. Retinal image quality becomes increasingly predictive of logMAR acuity as contrast and/or luminance is decreased. Everyday life requires individuals to function over a large range of contrast and luminance levels. Clinically, the impact of retinal image quality as a function of luminance and contrast is readily measurable in a time-efficient manner with M LC logMAR acuity charts.     

Evolution of the visual prognosis of prematures in the last 20 years

Opthalmoscopic examinations were performed on 5678 prematures, born between 1964 and 1984, by the same investigator in the same neonatal care unit. Three periods can be differentiated. In the first period (1964-1970) retinal disorders were frequent (20%), a quarter of them severe (stages 3–5). The inspiratory fraction of oxygen was the only oxymetric factor that was monitored. In the second period (1970-1977), less severe forms were observed, but still 4.5% of stage 1 and 8.7% of stage 2 (mild forms) were assessed. During this period, oxygen partial pressure was measured every 6 h in arterial blood whenever the inspiratory fraction of oxygen exceeded 0.3. In the last period (1977-1984), no severe forms were observed and mild forms amounted to only 0.9%. In this period, oxygen partial pressure was continuously monitored transcutaneously, whenever the inspiratory fraction of oxygen exceeded 0.21. Such data show that there is an association between better oxygen monitoring and the dramatically reduced incidence of retinopathy in prematures (RP).Presented at the 1984 meeting of the Club Jules Gonin in Lausanne, Switzerland     

Laceration and partial dislocation of LASIK flaps 7 and 4 years postoperatively with 20/20 visual acuity after repair

PURPOSE: To report two cases of late ocular trauma resulting in laceration of corneal flaps 7 and 4 years (cases 1 and 2, respectively) after LASIK. METHODS: A 49-year-old man sustained laceration of the flap and interface foreign body debris from construction material in the right eye 7 years after uneventful LASIK (case 1). A 33-year-old man had partial dislocation of the flap 4 years after LASIK in the left eye (case 2) due to a penetrating wood chip accident. Surgical procedures were performed to remove the foreign bodies and reposition the flaps. RESULTS: In case 1, postoperative uncorrected visual acuity (UCVA) was 20/25 with manifest refraction of -0.50 -0.50 x 110 corrected to 20/20. In case 2, UCVA was 20/20 with piano refraction after LASIK retreatment. CONCLUSIONS: Corneal LASIK flaps are susceptible to penetrating trauma, which can occur >7 years after the procedure. Proper everamanage ment of the trauma and LASIK flap can restore excellent visual acuity.     

脑外伤致视功能损伤20例临床分析

目的分析脑外伤致视功能损伤的原因、临床表现，为临床诊治提供参考。方法回顾性分析5年来因脑外伤致视功能损伤患者的致伤原因、临床表现及诊断要点。结果20例视功能损伤患者中，男15例、女5例；年龄5～70岁。其中青壮年16例。致伤原因：交通事故12例、跌落伤4例、打架斗殴伤3例、脑外科手术后1例。13例有外伤后意识丧失。视功能损伤包括：视力下降或丧失16例（20眼）、视野损伤7例（8眼）、复视3例。结论脑外伤特别是有意识丧失的患者，应及时进行眼科检查，以得到及时诊断和治疗。     

Comparison of visual function after epiretinal membrane removal by 20-gauge and 25-gauge vitrectomy

PURPOSE: To compare the efficacy and safety of 25-gauge vitrectomy with 20-gauge vitrectomy for macular pucker. DESIGN: Randomized clinical study. METHODS: Sixty-seven eyes (67 patients) with macular pucker were prospectively and randomly assigned to undergo 20-gauge vitrectomy or 25-gauge vitrectomy as a control group. Main outcome measurements consisted of best-corrected visual acuity (BCVA), mean induced astigmatism, total operation time, and postoperative complications. RESULTS: The mean BCVA at baseline and at one month and six months after surgery was 20/78, 20/62, and 20/42, respectively, in the 20-gauge group, and 20/85, 20/45, and 20/40 in the 25-gauge group. A significant difference in change in the logarithm of the minimal angle of resolution of BCVA between 20-gauge and 25-gauge was found at one month (-0.10 vs -0.269, P < .001), but not at six months (-0.327 vs -0.276, P > .01). CONCLUSIONS: If faster visual improvement is desired, 25-gauge vitrectomy may be preferable to 20-gauge vitrectomy for macular pucker.     

Prediction of visual field defects on standard automated perimetry by screening C-20-1 frequency doubling technology perimetry

PURPOSE: To determine if perimetric defects, initially seen with C-20-1 frequency doubling technology (FDT) in eyes with normal standard automated perimetry (SAP), will subsequently develop on standard automated perimetry. METHODS: Review of patients considered high-risk glaucoma suspects (GS) or with ocular hypertension (OHT), who underwent one C-20-1 FDT in 1997 or 1998. An abnormal frequency doubling technology was defined in two ways, as having either at least one, or at least two abnormal locations. An abnormal standard automated perimetry was defined as fulfilling two of three modified Anderson criteria for abnormality on two consecutive tests and at final standard automated perimetry. RESULTS: Of 63 eyes (50 patients), 18 (28.6%) had >or=1 FDT defects, and 12 (19.0%) had >or=2 defects. After follow-up of 62 +/- 26 months, an abnormal standard automated perimetry developed in 5 eyes (28%) with frequency doubling technology defects at 22 +/- 13 months (28% of eyes with >or=1 defect and 42% of eyes with >or=2 FDT defects), and in 4 of 45 eyes (9%) with normal frequency doubling technology at 32 +/- 30 months. Kaplan-Meier survival analysis revealed the risk of an abnormal standard automated perimetry at 5 years with or=1 defects, and >or=2 defects, was 10.3%, 11.8%, 30.6%, and 46.4% respectively (P = 0.060 for >or=1 defects compared with no defects; P = 0.002 for >or=2 defects compared with 相似文献   

Evaluating the visual experience: visual acuity and the visual analogue scale

PURPOSE: To attempt a comparison of the visual experience [assessed using a visual analogue scale (VAS)] with visual acuity in a group of normally-sighted adult optometric patients. METHODS: A single-item 100 mm paper VAS was administered to a sequence of 142 normally-sighted pre-presbyopic patients. Each individual was invited to indicate their recent subjective distance visual experience between the extremes of 'dreadful' (0 mm) and 'perfect' (100 mm). Each patient's binocular visual acuity was then determined at 6 m using a high-contrast logMAR chart under usual consulting room conditions. RESULTS: A weak association was revealed between the subjective indication of recent visual experience and the actual level of binocular acuity recorded in this normally-sighted group of subjects. On the basis of group responses a statistically significant discontinuity in the scores recorded with the VAS was demonstrated between patients who attained a clinical acuity better or worse than 0.10 logMAR units (6/7.5). Patient gender, age, and whether spectacles were habitually worn for distance viewing, were each revealed to be not statistically significant features. CONCLUSIONS: For normally-sighted optometric patients the subjective criterion of visual satisfaction would appear to be only loosely associated with the contemporaneous record of clinical acuity.     

Increases in the prevalence of reduced visual acuity and myopia in Chinese children in Guangzhou over the past 20 years

Background/aims

To estimate the prevalence of myopia based on reduced unaided visual acuity (VA) in Chinese school children over the past 20 years.

Methods

Guangzhou school health authorities have measured VA on Grade 1–12 students from 1988 to 2007 annually, using a LogMAR tumbling E chart. VA is reported as Snellen categories: normal (VA≥6/6), mildly reduced (6/9<VA<6/6), moderately reduced (6/18<VA≤6/9), and severely reduced VA (VA≤6/18).

Results

In 1988, over 80% of children in Grade 1 (age 6 years) and about 30% in Grade 12 (age 17 years) had normal unaided VA. By 2007, this dropped to only 60% in Grade 1 and about 10% in Grade 12. Conversely, the prevalence of moderately and severely reduced unaided VA increased from 6.2% in Grade 1 and 62.5% in Grade 12 in 1988 to 14.5% in Grade 1 and 84.11% in Grade 12 in 2007. This rate was unchanged from 2003 to 2007 at both the Grade 1 and Grade 12 levels.

Conclusions

In Guangzhou, the prevalence of reduced unaided VA has increased markedly in the past 20 years, but has stabilized in the past few years. This increase may result from environmental changes, such as increased schooling intensity and urbanization.     

The role of early visual cortex in visual short-term memory and visual attention

We measured cortical activity with functional magnetic resonance imaging to probe the involvement of early visual cortex in visual short-term memory and visual attention. In four experimental tasks, human subjects viewed two visual stimuli separated by a variable delay period. The tasks placed differential demands on short-term memory and attention, but the stimuli were visually identical until after the delay period. Early visual cortex exhibited sustained responses throughout the delay when subjects performed attention-demanding tasks, but delay-period activity was not distinguishable from zero when subjects performed a task that required short-term memory. This dissociation reveals different computational mechanisms underlying the two processes.     

Pattern visual evoked potentials visual acuity--the evaluation of visual acuity of less than 0.1

PURPOSE: We previously developed a new method for estimating objective visual acuity by means of pattern visual evoked potentials (PVEP). In this study, this method was applied to the evaluation of visual acuity of 0.05 and 0.01. METHODS: Ten subjects with visual acuity of 0.05 and ten normal subjects with visual acuity of 0.01 were examined. The visual acuity of the subjects was decreased step by step by means of plus spherical lenses of increasing power. In the PVEP study, the stimulus consisted of black and white checkerboards with a visual angle of 8 degrees (central stimulus) and a global field with a 5 degrees central circular scotoma (peripheral stimulus), contrast level of 15%, and a frequency of 0.7 Hz. One hundred PVEP responses were averaged per session. We reported that there was a linear relation between log subjective visual acuity of 0.1-1.0 and log check size of the patterns with PVEP. In reference to that, the check sizes of the patterns were estimated at 66' with visual acuity of 0.05, and 107' with visual acuity of 0.01. Each visual acuity was then used with other check sizes of three patterns. RESULTS: With central stimulus the P100 components of O1, O2, and Oz were recorded with 66' and 82' patterns at visual acuity of 0.05(central stimulus). The P100 components of O1, O2, and Oz were 107', 137' and 161' at visual acuity of 0.01(central stimulus). There was no P100 component at visual acuity of 0.05 and 0.01(peripheral stimulus). CONCLUSION: This method of PVEP is a useful tool as an objective estimation of visual acuity less than 0.1 and is presumed to stimulate preferentially the X retinal ganglion cell to parvocellular pathway.