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PubMed1986

The development of visual acuity in normal fullterm and preterm infants.

The development of visual acuity during the first year of life was assessed in 91 normal fullterm infants and 36 preterm infants with minimal perinatal complications, using the forced-choice preferential looking technique. Acuity in the preterm infants lagged behind that of the fullterm infants up to the age of 6-8 months if age was calculated from birth, and then reached equal levels. When age was corrected for prematurity, acuities in the two groups were very similar at all ages, but mean preterm acuity was consistently slightly higher than in the fullterm infants. The results suggest that early visual experience of preterm infants in the period up to the expected date of term may lead to a slight acceleration of the development of behavioural visual acuity. This is discussed in relation to electrophysiological studies which report a greater effect of prematurity on acuity development.

Aging↗

PubMed1983

Visual acuity in the young infant is highest in a small retinal area.

Visual potentials (VEP) evoked by alternating gratings were recorded daily in one infant between 10 and 13 weeks of age and at 20 weeks of age. The VEP amplitude was measured for a stimulus field of increasing area at low and high spatial frequencies. At low spatial frequencies the VEP amplitude increases with increasing stimulus area, while at high spatial frequencies (near visual acuity) the VEP amplitude remains constant for stimulus field sizes beyond 2 deg. These findings parallel those obtained in the adult, and indicate that visual acuity of the infant is not uniform across the retina but is highest in a small region, as in the adult.

Adult↗

PubMed2000

Corneal thickness and visual acuity after phacoemulsification with 3 viscoelastic materials.

PURPOSE: To determine whether differences exist in visual acuity and corneal thickness after phacoemulsification using various viscoelastic substances. SETTING: Phillips Eye Institute, Minneapolis, Minnesota, USA. METHODS: Fifty patients having routine phacoemulsification cataract extraction and intraocular lens implantation by a single surgeon using the same technique were randomly assigned to receive intraoperative administration of 1 of 3 viscoelastic substances: Amvisc Plus(R) (sodium hyaluronate 1.6%), OcuCoat(R) (hydroxypropyl methylcellulose 2%), or Viscoat(R) (chondroitin sulfate 4%-sodium hyaluronate 3%). Visual acuity and corneal thickness on the first postoperative day were compared between groups. RESULTS: Patients with a best corrected visual acuity (BCVA) of 20/40 or better 1 day postoperatively had significantly thinner corneas (596 microm) than those with a BCVA worse than 20/40 (639 microm). There were no differences in postoperative BCVA or percentage increase in central corneal pachymetry among the 3 viscoelastic groups. CONCLUSION: Viscoat, Amvisc Plus, and OcuCoat were comparable in their ability to produce clear corneas and good vision after routine phacoemulsification.

Chondroitin↗

PubMed2000

Comparison of topographic indices that correlate with visual acuity in videokeratography.

OBJECTIVE: To evaluate the relationship between the best spectacle-corrected visual acuity (BSCVA) and two quantitative indices of the anterior corneal surface obtained by videokeratography. DESIGN: Prospective, single center, comparative, observational study. PARTICIPANTS: Eighty-nine normal eyes and 52 eyes with keratoconus with contact lens-corrected visual acuity of 20/20 or better. INTERVENTION: Videokeratography was performed with the TMS-2 and the CAS system 2000. MAIN OUTCOME MEASURES: The relationship between the BSCVA recorded in log minimal angle of resolution (logMAR) units, the surface regularity index (SRI), and the predicted corneal acuity (PCA) were assessed by linear regression analysis. RESULTS: The BSCVAs for all eyes ranged from 0.82 to -0.30 logMAR units. BSCVA was highly correlated with the SRI (r = 0.70, P < 0.0001) and the PCA (r = -0.61, P < 0.0001). There was no statistical difference in the regression slopes and the intercepts for the estimated BSCVA using the SRI and measured BSCVA, and the estimated BSCVA using PCA and measured BSCVA. CONCLUSIONS: Two quantitative topographic indices, SRI and PCA, are useful for estimating the effect of irregular astigmatism on visual acuity even though both indices quantify different aspects of the anterior surface of the cornea.

Adolescent↗

PubMed2005

Combined pars plana vitrectomy and phacoemulsification to restore visual acuity in patients with chronic uveitis.

PURPOSE: To report the outcomes of combined phacoemulsification and pars plana vitrectomy (PPV) to restore visual acuity in patients with cataract and posterior segment involvement secondary to chronic uveitis. SETTING: Ocular Immunology and Uveitis Service, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA. METHODS: This study comprised 34 patients (20 women, 14 men; 36 eyes) with posterior segment involvement secondary to chronic uveitis who had combined phacoemulsification and PPV from 1998 to 2002. The main outcome measures were visual acuity, intraocular pressure, and cystoid macular edema. RESULTS: The mean patient age was 45 years +/- 16.09 (SD). The mean duration of uveitis before surgery was 56 +/- 44.17 months. In 24 eyes (66.7%), an intraocular lens (IOL) was implanted during surgery; 12 eyes (33.3%) were left aphakic. Five eyes (13.8%) received an intraocular steroid injection intraoperatively. Visual acuity improved in 26 eyes (72.2%), deteriorated in 5 (13.9%), and was unchanged in 5 (13.9%). The main reason for decreased visual acuity was refractory macular edema. During the follow-up, 2 IOLs were explanted secondary to lens intolerance. One IOL was repositioned because of iris capture by the haptics, and 1 dislocated inferiorly, causing monocular diplopia. The mean follow-up was 23.4 +/- 16.7 months. CONCLUSIONS: Results indicate that combined phacoemulsification and PPV is a feasible technique for the removal of cataract and pathologic vitreous in eyes with chronic uveitis. Although the exact role of vitrectomy in patients with uveitis remains to be determined, the combined surgery successfully restored useful vision in most cases.

Adolescent↗

PubMed1979

Reflectance of visual acuity screens.

The luminance of the background and of the target (visual acuity letter) was measured for five commonly used visual acuity screen materials. Most materials were found to be highly nonlambertian. A greater than threefold difference in reflectance normal to the surface was found for the respective screens tested. The percent polarization maintained by each screen material, using American Optical Vectograph systems, was measured. The relative illuminations generated by eight projector systems were compared. A discussion of the factors and recommendations for improvements related to projected chart visibility are made.

Field Dependence-Independence↗

PubMed1997

[Laser interferometry in preoperative evaluation of visual acuity in children].

PURPOSE: To study the possibility of using laser interferometry in prediction of visual acuity in children after cataract surgery. Until now this method has been used only in adults. In the literature no papers were found about prediction of visual acuity in children. MATERIAL AND METHODS: Laser interferometry was performed before surgery in 27 eyes of children aged 6-15 and the results were compared with visual acuity after cataract extraction with IOL implantation. RESULTS: Laser interferometry is of limited value in pediatric patients.

Adolescent↗

PubMed1982

Visual acuity in color contrast on cathode ray tubes: role of luminance, hue, and saturation contrasts.

Three experiments were conducted on 90 flying personnel to determine the role of luminance, hue, and saturation contrasts on angular visual acuity measured on a CRT system. A Snellen E test object was displayed under various visual acuity conditions on a TV screen, in color contrast, using red, yellow, green, cyan, blue, purple, white, and black. The response system gives response times and quality. The three photocolorimetric parameters are classified through data processing. All other things being equal, the best visual acuity is obtained under a luminance contrast. Two groups of colors can be differentiated under a hue contrast. The first group (red, blue, purple) is better perceived than the second (green, cyan, yellow, white) whatever the other color in simultaneous contrast may be. Higher saturation enhances visual acuity. A curve of mean response time vs. test object sizes is established for the various color couples. The obtained results are of interest for aerospace ergonomics.

Adult↗

PubMed2006

Functional characterisation and serial imaging of abnormal fundus autofluorescence in patients with retinitis pigmentosa and normal visual acuity.

AIM: To characterise and monitor abnormal fundus autofluorescence (AF) in patients with retinitis pigmentosa (RP) who have good visual acuity. METHODS: 21 patients with a clinical diagnosis of RP were examined. All had rod-cone dystrophy (ISCEV standard electroretinograms (ERGs)), visual acuity of 6/9 or better, and manifested a parafoveal ring of high density fundus AF. Repeat AF imaging was performed after periods of between 2 years and 5 years in 12 patients. Pattern ERG (PERG) and multifocal ERG (mfERG) were performed in 20 cases. Visual fields (VF), photopic and scotopic fine matrix mapping and small field PERGs were performed in representative cases. RESULTS: The rings of high density AF varied in size between patients (from 4 degrees -16 degrees diameter). MfERGs showed relative preservation over the central macular area, correlating with the size of AF ring and with PERG and psychophysical data. Progressive constriction of the AF ring was demonstrated at follow up in three patients. Serial PERG, mfERG, and VFs, performed in one of these cases, showed evidence of deterioration concordant with ring constriction. CONCLUSIONS: High density rings of AF, seen in some patients with RP with good visual acuity, demarcate areas of preserved central photopic function. MfERGs correlate with the area encircled by high density AF and the PERG data. The size of the ring of AF can show progressive constriction accompanied by increasing macular dysfunction.

Adolescent↗

PubMed1993

Improvement of visual acuity after surgery for nystagmus.

PURPOSE: The authors compared the preoperative and postoperative binocular visual acuities and eye movement recordings of patients who underwent eye muscle surgery consisting of the Anderson-Kestenbaum procedure or the artificial divergence procedure modeled after Cüppers, or a combination of both procedures, for the treatment of infantile nystagmus with head turn. METHODS: Binocular visual acuities and eye movement recordings by electro-oculography (EOG) were compared preoperatively with those done within 3 weeks postoperatively. Shifting and broadening of the minimal intensity zone and foveation time and changing of the waveform were measured. The treatment of 6 of 18 patients was based on the artificial divergence principle; for 7 patients, treatment was in accordance with the Anderson-Kestenbaum principle; and 5 patients had combined procedures. RESULTS: The improvement in binocular visual acuities was two Snellen lines or more in one of six patients in the artificial divergence group and four of five patients in the combined treatment group. The EOG recordings showed shifting of the minimal intensity zone toward the primary position in all three groups. A broadening of the minimal intensity zone occurred mostly in the artificial divergence and combined groups. Increases in foveation time and changes in waveforms from jerk to jerk with foveation were found in three of six patients in the artificial divergence group and in two of five patients in the combined group. CONCLUSION: With less muscle surgery, the artificial divergence and combined operations gave better vision improvement than the Anderson-Kestenbaum operation.

Adolescent↗

PubMed1996

Changes in visual acuity in a population. The Beaver Dam Eye Study.

PURPOSE: To describe the change in visual acuity over a 5-year period in persons participating in a large population-based study. METHODS: Best-corrected visual acuity was measured, after refraction, with logMAR charts using a modification of the Early Treatment Diabetic Retinopathy Study protocol in 3684 persons living in Beaver Dam, Wisconsin, who ranged in age from 43 to 86 years at the time of a baseline examination from 1988 to 1990, and at a follow-up examination from 1993 to 1995. RESULTS: The change in the number of letters read correctly over the 5-year period varied from 0.4 +/- 4.9 (mean +/- standard deviation) in people between 43 and 54 years of age to -5.2 +/- 15.4 in people 75 years of age or older at baseline. Over the 5-year period, vision became impaired (20/40 or worse in the better eye) in 2.9% of the population and severely impaired (20/200 or worse in the better eye) in 0.3%. The visual angle doubled in 1.7% of the population, and 2.4% had improved vision. People 75 years of age or older at baseline were 12.5 times (95% confidence interval [Cl], 8.6-18.2; P < 0.001) more likely to have impaired vision, 9.7 times (95% Cl, 5.9-16.0; P < 0.001) more likely to have doubling of the visual angle, and 78 times more likely (95% Cl, 9.9-614.1; P < 0.001) to have severe visual impairment than people younger than 75 years of age at baseline. People 75 years of age or older who were living in nursing homes or group homes were 3.8 times more likely to have impaired vision, 3.3 times more likely to have severely impaired vision, and 5.7 times more likely to have a doubling of the visual angle than those not residing in a nursing home or a group home. CONCLUSION: These data provide precise population-based estimates of incidence of visual loss over a wide spectrum of ages and show that decreased visual acuity in people 75 years of age is a common finding, especially in those who are in nursing homes or group homes.

Adult↗

PubMed1999

Cystoid macular edema after phacoemulsification: relationship to blood-aqueous barrier damage and visual acuity.

PURPOSE: To ascertain the incidence of cystoid macular edema (CME) after phacoemulsification and its relationship to blood-aqueous barrier damage and visual acuity. SETTING: A British teaching hospital. METHODS: A prospective trial was performed to document the incidence of CME after routine phacoemulsification with continuous curvilinear capsulorhexis. LogMAR visual acuity and laser flare were measured using the KOWA FC 1000 laser cell-flare meter preoperatively and 1, 14, 30, and 60 days postoperatively. At day 60, a standardized fluorescein angiogram was performed and graded by masked observers. RESULTS: The rate of angiographic CME on day 60 was 19%. Visual acuity at each visit was significantly worse in the CME group (P < .05). The flare and cell values at days 14, 30, and 60 were higher in the CME group at day 60; however, the difference was not statistically significance (P > .05). CONCLUSIONS: The incidence of CME after routine phacoemulsification was 19%. Patients with CME at day 60 had significantly worse visual acuity than those who did not from the first postoperative day throughout the follow-up. There was a trend for patients who had CME at day 60 to have more postoperative inflammation.

Aged↗

PubMed1997

[The impact of different incisions on visual acuity and corneal refractivity in cataract surgery].

OBJECTIVE: To research the impact of different incisions of cataract surgery on post-operative visual acuity and corneal refractivity. METHODS: The visual acuity and corneal refractivity in 243 eyes having undergone extracapsular cataract extraction and phacoemulsification with 5 mm tunnel incision or 7 mm frown-shaped incision were examined and compared at three post-operative periods. RESULTS: The mean increase in corneal refractivity in phacoemulsification group was significantly less (P < 0.05) and the corrected visual acuity was much better (P < 0.05) than that in conventional extracapsular cataract extraction (ECCE) group at post-operative 1/2 month, 3 months and 6 months (P < 0.05). In the phacoemuisification group, the increase of the post-operative refractivity in 7 mm frown-shaped incision group was less than that in 5 mm tunnel incision group at 1/2 month and 3 months (P < 0.05). CONCLUSION: 7 mm frown-shaped incision of phacoemulsification is the most effective method to control the post-operative corneal astigmatism in cataract surgery.

Adolescent↗

PubMed2002

Optokinetic stimuli: motion sickness, visual acuity, and eye movements.

BACKGROUND: It is commonly assumed that motion sickness caused by moving visual scenes arises from the illusion of self-motion (i.e., vection). HYPOTHESES: Both studies reported here investigated whether sickness and vection were correlated. The first study compared sickness and vection created by real and virtual visual displays. The second study investigated whether visual fixation to suppress eye movements affected motion sickness or vection. METHOD: In the first experiment subjects viewed an optokinetic drum and a virtual simulation of the optokinetic drum. The second experiment investigated two conditions on a virtual display: a) moving black and white stripes; and b) moving black and white stripes with a stationary cross on which subjects fixated to reduce eye movements. RESULTS: In the first study, ratings of motion sickness were correlated between the conditions (real and the virtual drum), as were ratings of vection. With both conditions, subjects with poor visual acuity experienced greater sickness. There was no correlation between ratings of vection and ratings of sickness in either condition. In the second study, fixation reduced motion sickness but had no affect on vection. Motion sickness was correlated with visual acuity without fixation, but not with fixation. Again, there was no correlation between vection and motion sickness. CONCLUSIONS: Vection is not the primary cause of sickness with optokinetic stimuli. Vection appears to be influenced by peripheral vision whereas motion sickness is influenced by central vision. When the eyes are free to track moving stimuli, there is an association between visual acuity and motion sickness. Virtual displays can create vection and may be used to investigate visually induced motion sickness.

Adult↗

PubMed1979

A new test of visual acuity using a holographic phase grating and a laser.

A new visual acuity testing device is able to determine a specific visual acuity of the retina even in the presence of opacities of the ocular media, such as a cataract. This is achieved by forming two spatially coherent, quasimonochromatic point sources near the nodal point of the eye. The two spherical waves that emanate from the point sources interact to produce a pattern of stripes on the retina. The intensity of the pattern is easily varied. More importantly, the pattern can be projected over different-sized retinal areas corresponding to visual fields of 0.5 to 15 degrees in diameter. The device may be useful for vision research and preoperative assessments of visual potential.

Holography↗

PubMed2006

Longitudinal changes in visual acuity in keratoconus.

PURPOSE: The present investigation aimed to identify factors that predict reduced visual acuity in keratoconus from a prospective, longitudinal study. METHODS: This report from the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study used 7 years of follow-up data from 953 CLEK subjects who did not have penetrating keratoplasty in either eye at baseline and who provided enough data to compute the slope of the change over time in high- or low-contrast best-corrected visual acuity (BCVA). Outcome measures included these slopes and whether the number of letters correctly read decreased by 10 letters or more in at least one eye in 7 years. RESULTS: Mean age of the subjects at the first follow-up visit was 40.2 +/- 11.0 years (mean +/- SD). Overall, 44.4% were female, and 71.9% were white. The slope of the change in high- and low-contrast BCVA (-0.29 +/- 1.5 and -0.58 +/- 1.7 letters correct/year, respectively) translated into expected 7-year decreases of 2.03 high- and 4.06 low-contrast letters correct. High- and low-contrast visual acuity decreases of 10 or more letters correct occurred in 19.0% and 30.8% of subjects, respectively. Independent predictors of reduced high- and low-contrast BCVA included better baseline acuity, steeper first definite apical clearance lens (FDACL), and fundus abnormalities. Each diopter of steeper baseline FDACL predicted an increased deterioration of 0.49 high- and 0.63 low-contrast letters correct. CONCLUSIONS: CLEK Study subjects with keratoconus exhibited a slow but clear decrease in BCVA during follow-up, with low-contrast acuity deteriorating more rapidly than high-contrast. Better baseline BCVA, steeper FDACL, and fundus abnormalities were predictive of greater acuity loss with time.

Adult↗

PubMed2006

Cystoid macular edema after phacoemulsification: risk factors and effect on visual acuity.

BACKGROUND: To determine the incidence and risk factors for cystoid macular edema (CME) after phacoemulsification surgery and its effect on visual acuity. METHODS: This prospective study evaluated 98 eyes of 98 patients (43 women) with a mean (SD) age of 61.8 (11.3) years. Phacoemulsification was performed with temporal clear corneal incision and implantation of foldable hydrophilic acrylic intraocular lens in the bag. Postoperative visits were on day 1, week 1, and at 1, 3, and 6 months. In addition, at week 10 all patients had fundus fluorescein angiography, and presence of CME was determined. Age, sex, iris colour, pseudoexfoliation, type of cataract, phaco time, status of the posterior vitreous, iris trauma, severity of anterior chamber reaction, and visual acuities were evaluated. RESULTS: No major intraoperative complications occurred. Twenty-five (25.5%) eyes were CME(+), and 73 (74.4%) eyes were CME(-). CME occurred in 70% of patients with iris trauma and 20.5% of patients with no iris trauma. CME was more common in patients who had postoperative anterior chamber inflammation of 2+ or more than in patients with less inflammation (43.2% vs. 11.5%). Complete posterior vitreous detachment had some apparent protective effect against CME development. The mean visual acuities of CME(+) patients were lower than those of CME(-) patients in all postoperative periods. The difference was significant in the third month (p < 0.05). INTERPRETATION: CME after phacoemulsification was associated with iris trauma and severe postoperative inflammation. Complete posterior vitreous detachment had some apparent protective effect against CME development. CME may be associated with decreased visual acuity.

Aged↗

PubMed1998

Visual acuity versus letter contrast sensitivity in early cataract.

Large and small letter contrast sensitivity and visual acuity were assessed in 37 elderly eyes (mean VA -0.01 logMAR, Snellen 6/6) and their lens opacities were categorised and graded using the LOCS III system. Large letter contrast sensitivity was often not reduced in cataract from age-matched normal values and provided limited information. Small letter contrast sensitivity was shown to be a more sensitive measure of early cataract than visual acuity and large letter contrast sensitivity. Its usefulness may be limited by its strong correlation with visual acuity (r2 = 0.70), which is the standard and traditional measure of vision in cataract.

Aged↗