Contrast visual acuities in cataract patients. II. After IOL implantation.

Contrast visual acuities were measured in 100 eyes of 75 patients who attained a best-corrected visual acuity of greater than or equal to 0.8 (20/25) after intraocular lens (IOL) implantation. The variable contrast visual acuity chart (VCVAC), with three contrast levels of 90, 15, and 2.5% and reverse polarity of 90% contrast, was used to measure contrast visual acuities. The follow-up period ranged from 3 to 35 months (mean 7.41). The mean visual acuities measured with the 90, 15, and 2.5% charts were 0.92 (SD = 0.11), 0.59 (SD = 0.13), and 0.33 (SD = 0.14), respectively. The mean visual acuity measured with the 90% reverse polarity chart was 0.97 (SD = 0.11). The decreases in visual acuities compared with the 90% contrast were 0.64 and 1.48 octaves in the 15% and the 2.5% contrast charts, respectively. The pattern of the contrast acuity profile was comparable to normal subjects, but in 28 of 100 (28%) eyes, the visual acuities measured with the reverse polarity chart were slightly better than those measured with the standard 90% contrast chart, suggesting that the glare effect still exists after IOL implantation, though to a lesser degree than in cataractous eyes.     

An automated visual acuity testing computer program using the Apple II system

We developed an automated visual acuity testing program that uses an E optotype with surrounding confusion bars. The computer software program runs on Apple II equipment and a black-and-white monitor with a five-inch screen. The program is available in response box and joystick versions. The test is suitable for children older than 31/2 to 4 years of age and for adults. A t-test on the same floppy disk as the visual acuity programs is used to test the probability that the differences in test results are greater than chance. Visual acuities of 20 normal subjects were reduced by means of plus lenses. Test-retest acuity correlation coefficients were similar for letter charts and computer-generated E optotypes, suggesting approximately equal reliability under the test conditions employed. Visual acuities of 12 amblyopic eyes were obtained by a Ferris-type letter chart and computer-generated E optotypes. The correlation coefficient was +0.93, suggesting similar test results by these two methods.     

The set of variable- contrast visual acuitycharts and its clinical application

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Visual acuity and color sensitivity in retinal detachment]

In patients with unilateral detachment of the retina after successful operation (buckling 3x, cerclage 3x, combined operation 4x), the visual acuity was assessed on Snellen optotypes or Landolt's ring chart. Optotype charts with rings were made according to recommendations of the commission for vision of the American Academy of Sciences. Snellen's visual acuity of healthy and affected eyes was 6/9-6/6. In all patients moreover sensitivity to contrast was examined assessed by means of a VISTESCH testing table. It was revealed that sensitivity for contrast in all operated eyes is significantly lower than in healthy eyes and that the threshold visual acuity and steepness of lines is significantly lower.     

Early visual results with the rollable ThinOptX intraocular lens

PURPOSE: To prospectively assess the clinical and visual outcomes of phacoemulsification and implantation of a rollable intraocular lens (IOL) with a thin optic and compare the results with those of implantation of a foldable acrylic IOL. SETTING: Department of Ophthalmology, Tokyo Dental College, Ichikawa General Hospital, Ichikawa, Chiba, Japan. METHODS: Sixteen consecutive eyes of 8 patients (4 women, 4 men) with corticonuclear cataract had small-incision clear corneal phacoemulsification with implantation of a rollable ThinOptX IOL (ThinOptX Inc.) in the capsular bag. Twenty eyes of 10 age- and sex-matched patients (5 women, 5 men) with the same diagnosis had phacoemulsification and intracapsular implantation of an AcrySof foldable acrylic IOL (MA60BM, Alcon). The patients' refractive status and uncorrected and best corrected distance visual acuities were assessed preoperatively and 1 week and 1, 3, and 6 months after surgery. The uncorrected and best corrected near acuities were measured before and 6 months after surgery. Contrast visual acuity was measured with variable contrast charts 1, 3, and 6 months after surgery, and the results in the 2 IOL groups were compared. Anterior segment photography, intraocular pressure (IOP) measurement, specular microscopy, and fundoscopy were done before surgery and at 1, 3, and 6 months. RESULTS: The final best corrected distance acuity was better than 20/25 in all eyes with a ThinOptX IOL and 18 eyes (90%) with an AcrySof IOL. The best corrected near acuity was better than 20/40 in 12 eyes (75%) and 14 eyes (70%), respectively. The mean contrast acuity with charts 2 and 3 was significantly higher in the ThinOptX group than in the AcrySof group at all examinations (P<.05). The final mean postoperative induced astigmatism was 0.06 diopter (D) +/- 0.50 (SD) and 0.25 +/- 0.68 D, respectively (P>.05).There were no differences in IOP or corneal endothelial cell density between the 2 groups at any examination. No intraoperative or postoperative complications occurred. CONCLUSIONS: ThinOptX IOL implantation provided best corrected near and distance visual acuities comparable to those provided by the AcrySof IOLs. The significantly higher contrast acuities attained after implantation of the ThinOptX lens may be attributable to its ultrathin properties.     

Measurement of glare sensitivity in cataract patients using low-contrast letter charts*

The Committee on Ophthalmic Procedures Assessment of the American Academy of Ophthalmology suggested using low-contrast visual acuity measured before and after adding a glare source as a test for assessing overall visual disability from immature cataracts. We have developed a test that follows the Committee's three principles of design, and we report that the effect of glare on visual acuity is considerably greater for recognizing low-contrast letters than for recognizing high-contrast letters. The effect of glare on visual acuity increases progressively as letter contrast is reduced in the stages 96%, 50%, 25%, 11% and 4%, The 25% chart (and possibly the 11% chart) gives the most suitable sensitivity for eyes with immature cataracts. Age-related brunescence and aging itself do not necessarily produce high sensitivity to glare. Sensitivity to glare was markedly different in eyes with different kinds of cataract.     

Threshold visual acuity testing of preschool children using the crowded HOTV and Lea Symbols acuity tests

PURPOSE: To compare the testability and threshold acuity levels for very young children on the crowded HOTV logMAR distance visual acuity test presented on the BVAT apparatus and the Lea Symbols logMAR distance visual acuity chart. METHODS: Subjects were 87 Head Start children from age 3 to 3.5 years. Testing consisted of binocular pretraining at near using a lap card as needed, binocular pretraining at 3 m, and threshold testing for each eye. The testing procedure, adapted from the Amblyopia Treatment Study, presented optotypes until the child was unable to correctly name or match three of three or three of four optotypes of a given size. Threshold acuity was the smallest size for which at least three optotypes were correctly identified. RESULTS: Both near and distance pretraining were completed by 71% of children for HOTV and by 75% for Lea Symbols (P =.39). The distribution of threshold acuities differed between the two tests. For the 69 eyes of 53 children who were successfully tested with both optotypes, results from the crowded HOTV acuity test were on average 0.25 logMar (2.5 lines) better than those from the Lea Symbols acuity test (P <.001). CONCLUSIONS: The proportion of children between 3 and 3.5 years of age whose monocular visual acuity could be assessed was high and was similar for the two charts tested. Crowded HOTV acuity results were better on average than results using Lea symbols. The different formats of the two tests may explain the observed differences in threshold acuity level.     

Letter contrast sensitivity in retinitis pigmentosa patients assessed by Regan charts

Regan Contrast Sensitivity Letter Charts were used to assess the effects of reduced contrast and luminance on visual acuity in retinitis pigmentosa (RP) patients. Letter acuity was measured monocularly in 17 RP patients and in 14 age-similar normals using charts of three different contrast levels presented at each of four levels of illumination. Despite visual acuities of 20/40 or better under standard clinical test conditions, an appreciable number of RP patients were unable to identify any letters on the intermediate- and/or low-contrast Regan charts. For example, even at the recommended test luminance, 5 patients could not read any letters on the intermediate (11%) contrast chart, and 9 could not be scored on the low (4%) contrast chart. Consequently, the Regan charts were found to have limited usefulness in quantifying the exact extent of visual impairment in this group of RP patients. Nevertheless, our results document the degree of visual acuity loss that can be experienced by RP patients under conditions of low contrast and luminance.     

A new set of variable-contrast visual acuity charts

Using a computer plotting technique, we designed four variable-contrast visual acuity charts. The contrast of the first 3 is 90, 15, and 2.5%, respectively. The fourth is 90%, but the luminance of the optotypes and background are the reverse of the first chart. The main features of these charts are as follows. Both contrast sensitivity and spatial frequency are in geometric gradation, which observes the laws of Weber and Fechner. The mean average luminance, (Lmax + Lmin)/2, is constant for all four charts, which follows the concept of contrast sensitivity function (CSF). Charts 1 and 4, which have the same contrasts but different glare backgrounds, measure the glare that is related to the transparency of the refractive media of the eye. Because the charts are rotatable, patient memorization and guessing are minimized. Results compared with those of the conventional visual acuity test and are understandable by patients and eye care practitioners. The charts, which are simple, easy, and require little time, are inexpensive and portable.     

The relationship between indoor and outdoor Snellen visual acuity in cataract patients

One hundred six cataractous eyes of 78 patients were evaluated to examine the relationship between indoor and outdoor Snellen visual acuity. While 81 of all cataractous eyes (76.4%) had Snellen visual acuities of 20/40 or better when tested indoors, only 33 eyes (31.2%) had 20/40 or better Snellen visual acuities when tested outdoors facing the sun. When tested indoors, only three eyes (2.8%) had Snellen visual acuities worse than 20/80, while 31 eyes (29.2%) had outdoor Snellen visual acuities worse than 20/80. Ten eyes (9.4%) had outdoor Snellen visual acuities worse than 20/200. Seventy-four eyes (69.8%) had outdoor visual acuities that were at least two Snellen lines worse than those measured indoors and 23 eyes (21.7%) had outdoor visual acuities that were at least five Snellen lines worse. The median difference between indoor and outdoor visual acuity was three Snellen lines. The need for increased precision in the ability to assess outdoor "real world" vision while in the ophthalmologist's examination room is discussed. Clearly, indoor Snellen visual acuity alone is insufficient to evaluate functional visual impairment in cataract patients.     

蓝光滤过型人工晶状体AcrySof Nature的初步临床研究

目的：评估蓝光滤过型人工晶状体AcrySof Nature的安全性、有效性。方法：35例51只眼诊断为老年性白内障的患者随机分为两组，行超声乳化白内障吸除术。其中20例24只眼植入AcrySof Nature人工晶状体，15例27只眼植入AR40e人工晶状体。观察患者术后的远近视力、前房蛋白浓度、对比敏感度及并发症。用调查量表评价患者的蓝视、畏光和眩光等视觉症状。结果：随访3个月，AcrySof Nature组最佳矫正远视力≥0．5者为24只眼(100％)，AR40e组为25只眼(96．3％)，两组的视力、前房蛋白浓度、对比敏感度无显著差异。调查量表显示AcrySof Nature组的蓝视及眩光现象较少。结论：蓝光滤过型人工晶状体AcrySof Nature有良好的生物相容性，术后视力提高满意，且不影响患者的对比敏感度和对颜色的感知，但其对视网膜的保护作用还需进行更长时间及更多样本量的研究。     

Visual performance with night vision goggles after photorefractive keratectomy for myopia

OBJECTIVE: To evaluate visual performance and resolution through night vision goggles (NVG) before and after photorefractive keratectomy (PRK). DESIGN: Nonrandomized, comparative (self-controlled) trial. PARTICIPANTS: Nineteen patients (38 eyes) of active-duty US Army Special Forces soldiers. INTERVENTION: PRK for myopia and astigmatism. MAIN OUTCOME MEASURES: Visual acuity with best optical correction was measured preoperatively and postoperatively (3 months) using acuity charts of various contrast (100%, 10%, 2.5%, 1.25%). Preoperative and postoperative (3 month) uncorrected and best-corrected visual resolutions through NVGs were assessed using a high contrast tribar chart presented at four light levels (3.44 x 10(-3), 1.08 x 10(-3), 1.04 x 10(-4), 1.09 x 10(-5) foot Lamberts) simulating a range of night sky conditions. Subjects were trained before testing. RESULTS: Uncorrected visual acuity at the 3-month postoperative assessment was greater than or equal to 20/20 in 33 of 38 (86.8%) eyes. No eyes lost 2 or more lines of best spectacle-corrected visual acuity. Preoperative and 3-month postoperative best-corrected low-contrast acuity measurements showed no significant differences at all levels of resolution. Preoperative visual resolution through NVGs decreased systematically with decreasing night sky condition. Visual acuities before PRK were reduced without optical correction. Postoperative visual performance with NVGs (without optical correction) equaled or exceeded performance preoperatively with best correction. CONCLUSIONS: This prospective case series provides data on the safety and efficacy of PRK with respect to visual performance under night sky conditions using NVGs. There was no significant loss of visual acuity across a range of contrast levels 3 months postoperatively. There was no change in best-corrected NVG visual resolution postoperatively, whereas uncorrected visual resolution was significantly enhanced compared with preoperative levels. This improvement may translate into better function for soldiers who are unable to or choose not to use optical correction in operational environments.     

Modeling the effect of forward scatter and aberrations on visual acuity after endothelial keratoplasty

Purpose. To evaluate the effects on visual acuity of forward scatter and aberrations typical of those after Descemet stripping endothelial keratoplasty (DSEK). Methods. Twenty normal eyes of 20 subjects (ages 22-57 years) were examined with best spectacle correction. Under photopic conditions, high-contrast visual acuities (HCVAs) were measured by using ETDRS charts. Visual acuity was also measured by using aberrated charts that simulated the typical high-order aberrations at 12 months after DSEK. Forward scatter was induced by viewing the eye charts through a 1-mm-thick layer of scattering solution (Amco Clear, at a concentration of 4000 nephelometric turbidity units) and was measured with a straylight meter. Results. Forward scatter increased from 1.19 ± 0.11 log straylight parameter (log[s]; mean ± SD) without induced scatter to 1.57 ± 0.06 log(s) with induced scatter (P < 0.001). Induced scatter reduced HCVA on the nonaberrated chart by 2.7 Snellen letters, from 20/19 (Snellen equivalent) to 20/21 (P < 0.001) and by 2.1 letters on the aberrated chart, from 20/25 to 20/28 (P = 0.005). Addition of aberrations reduced HCVA by more than twice the number of Snellen letters than did induced scatter, by 6.4 letters with low scatter (P < 0.001), and by 5.8 letters with high scatter (P < 0.001). Conclusions. Under typical clinical testing conditions, increased forward scatter has minimal effect on visual acuity. High-order aberrations are a more likely cause of degraded visual acuity than is forward scatter in eyes with clear corneas after DSEK.     

Measurement of visual acuity with two different charts; a comparison of results and repeatability in patients with cataract

Purpose: To compare two different optotypes to measure visual acuity. Methods: Experiment 1: Fifty patients with moderate cataracts were asked to read a chart consisting of letters of the alphabet (Sloan letters) first and a chart comprising Landolt's broken rings afterwards. Experiment 2: Half of patients were instructed to repeat the reading with a second letter chart, the other half was instructed to read the chart with the broken rings again. Results and conclusions: Experiment 1: It was found that with the letter chart more optotypes (two to four) were recognized than with the broken ring chart. The different result of visual acuity measurement with the two optotypes is irrespective of the visual acuity. Experiment 2: The re-read instruction revealed that the measurements were reproduced equally for both charts.     

Evaluating a new logMAR chart designed to improve visual acuity assessment in population-based surveys

AIMS: This study aimed to evaluate a new chart designed to improve the collection of visual acuity data in population-based surveys. The Reduced logMAR E chart (RLME) employs three letters per line, 'tumbling E' optotypes, and conforms to accepted contemporary design principles. METHODS: The performance of the chart was assessed within a population-based glaucoma survey in Thailand. Performance indices were test-retest variability (TRV) and agreement with acuity data measured using the ETDRS logMAR chart which acted as the 'gold standard'. RESULTS: The 95% confidence limits for TRV of RLME acuity data were +/-0.15 logMAR. This figure is consistent with published data on the TRV of acuities measured using five-letter-per-line logMAR charts. The mean difference between RLME and ETDRS acuity data was 0.00 logMAR (95% confidence intervals of +/-0.05 logMAR) indicating that RLME acuities agreed well with those of the ETDRS chart. The chart and its method of use was readily accepted by the local ancillary staff who required only minimal training before acuity measurement could be delegated to them. CONCLUSIONS: The study demonstrated that the RLME chart is capable of accurate and repeatable acuity measurements. Certain aspects of the design of the RLME chart may be particularly pertinent to the measurement of vision in population-based surveys.     

Primary vitrectomy alone for repair of retinal detachments following cataract surgery

PURPOSE: To report the visual, anatomic, and refractive results of primary vitrectomy alone for the repair of retinal detachments (RD) following cataract surgery. METHODS: Retrospective review of office charts and operative reports of 83 eyes. RESULTS: A minimum of 4 months' follow-up was achieved for 78 pseudophakic or aphakic eyes that underwent primary vitrectomy, internal drainage of subretinal fluid, retinopexy, and intravitreal gas injection for RD repair. Anatomic reattachment was achieved in 93.6% of cases after one procedure and in 96.2% eventually. Median preoperative Snellen acuity was 20/200 and increased to 20/25 at final examination. For the 45 eyes with macula-off detachments, 80% achieved final acuities greater than or equal to 20/40. The average refractive change following surgery was -0.11 diopters. Transient postoperative ocular hypertension was seen in 17.9% and proliferative vitreoretinopathy with recurrent RD in 5.1%. CONCLUSION: Primary pars plana vitrectomy is a highly effective treatment modality for the repair of RD following cataract surgery, and appears to be refractively neutral.     

The component of gaze selection/control in the development of visual acuity in children

Visual acuity was tested for 180 eyes of 90 children in four age groups using three types of test charts. Subjects read the same 10 high-contrast letters in Snellen (line) format, as isolated-letter flash cards, and as repeat-letter flash cards. Group mean line and group mean isolated-letter acuity showed similar progressive improvements with age. A subgroup of 24 of 50 eyes of 4- to 5-year-olds (15 of 25 subjects) and 3 of 50 eyes of 6- to 7-year-old (2 of 25 subjects) had low Snellen acuity. Of this low-acuity subgroup of 27 eyes, 10 scored above average for their age group on the repeat-letter chart. We concluded that abnormal lateral interactions were not the explanation for the immaturity of Snellen acuity in these 10 eyes. We suggest that an important factor in the low acuities of these 10 eyes is delayed development of the selection and/or control of gaze direction. Some eyes with excellent Snellen acuity showed high crowding. For example, there were five such eyes in the oldest group. We suggest that the excellent acuities of at least two of these eyes are limited by minor inaccuracies in gaze selection and/or control rather than by lateral interaction.     

Refractive outcomes after bilateral multifocal intraocular lens implantation

PURPOSE: To evaluate the efficacy and safety of bilateral multifocal intraocular lens (IOL) implantation after cataract surgery. SETTING: Oftalmológico de Valencia-CEOVAL, Valencia, Venezuela. METHODS: This retrospective study evaluated patient charts for the patient selection method, preoperative evaluation, surgical technique, postoperative visual and refractive outcomes, and complications. It included 70 eyes of 35 patients who had lens extraction with bilateral implantation of an Array multifocal IOL. Fourteen eyes of 7 patients had hyperopia with presbyopia, and 56 eyes of 28 patients had cataract. RESULTS: All eyes achieved an uncorrected distance acuity of 20/40 or better and an uncorrected near acuity of J5 or better. Six patients (18%) reported moderate halos, and 22 patients (63%) occasionally wore glasses. CONCLUSION: Bilateral multifocal IOL implantation was effective and safe in cataract and hyperopic patients with presbyopia, providing good uncorrected distance and near acuities.     

Differences in visual acuity between the eyes: determination of normal limits in a clinical population

We determined the difference in visual acuity between the right and left eyes of patients and also determined the maximal level of acuity expected in a group of visually normal individuals. Visual acuity was measured in the right and left eyes of 72 subjects aged from 16 to 67 years using Bailey-Lovie type charts. The chart was read until fewer than three letters were read on a line and acuities were based on each letter correct contributing ?0.02 to the overall score. For 12 of these subjects, visual acuity was measured a further four times. Average visual acuities for right and left eyes were ?0.137 and ?0.126logMAR, respectively. The signed visual acuity difference was normally distributed and had a standard deviation of 0.050logMAR. The mean visual acuity difference for the 12 subjects for whom the measures were repeated was 0.033logMAR (SD of the signed visual acuity difference: 0.049logMAR). We conclude that if a patient has a difference in visual acuity between the two eyes of more than 5 letters on a Bailey-Lovie style chart, further investigation is indicated.     

儿童白内障摘除联合后房型人工晶体植入术后并发症的处理

为了预防儿童白内障术后发生弱视和斜视,自１９９４ 年１ 月至１９９７ 年６ 月,对４０ 例（４８ 只眼）２ ～１４ 岁患儿行白内障现代囊外摘除联合后房型人工晶体植入术,均获得良好的效果。术后主要并发症为葡萄膜炎（ 具体表现瞳孔区有灰色纤维素膜） ,经过治疗获得满意的视力。出院时４８ 只眼中有１８ 只先天性白内障眼术后视力０－２ ～０－６ ,２６ 只外伤性白内障眼术后视力０－４ ～０－８ ,４ 只眼检查视力不合作。出院后追踪观察视力３ 个月至２ 年,均有不同程度提高。