Dynamic Visual Acuity test while walking or running on treadmill: Reliability and normative data.

BACKGROUND: This study aimed to report normative reference data for a Dynamic Visual Acuity test while walking on treadmill. The protocol's suitability was assessed by investigating its test-retest reliability and its validity through the drop-out rate and verification of the frequency of head movements. Furthermore, the influence of age on visual acuity loss (VAL) was determined to reveal the need for age-specific reference data. METHODS: Visual acuity was measured in 171 healthy adult participants (age range: 20.0-77.3 years; mean age: 40.1 years) with the head stationary (SVA) and in a dynamic condition (DVA) while walking on treadmill at 3, 4, 6 and 9 km/h. Relative test-retest reliability on SVA and DVA was investigated with intraclass correlation coefficients (ICC). The measurement errors of SVA, DVA and VAL were calculated for absolute reliability. Influence of age on VAL was investigated with regression analysis, followed by an ANOVA to investigate decade-related differences. The drop-out rate during DVA was mapped using a frequency table. Head frequencies were monitored using 3D motion tracking software. RESULTS: Strong consistency (ICC ≥ 0.89) was found for SVA and DVA values. Measurement errors for VAL were less than 0.1 logMAR. Younger participants (decade 3-4) showed less VAL at 3 and 4 km/h. The drop-out rate increased with increasing walking speed (0-18.8%), especially in older adults. Although head frequency increased with increasing speed, the dominant frequency ranged around 2 Hz for all walking speeds. CONCLUSION: This DVA protocol is reliable and normative data have been established. To facilitate its use in clinical practice, further validation of the protocol in patients with bilateral vestibulopathy is needed.

Iris from Iridectomy Used as Spacer underneath the Scleral Flap: The Iridenflip Trabeculectomy Technique.

Purpose. We describe a modified trabeculectomy technique in which the iris is used to prevent fibrosis of the scleral flap. Material and Methods. A retrospective case series of patients with medically uncontrolled open angle glaucoma underwent trabeculectomy. Instead of performing a classical iridectomy, the iris was used as spacer underneath the scleral flap. Postoperative management was identical to classical trabeculectomy, with suture removal and needling if necessary. Five of the patients underwent simultaneous phacoemulsification through a separate temporal corneal incision. Patients should have two-year follow-up. Results. Data of ten patients were analysed, two had a previous failed trabeculectomy, two had LTP, and one had a corneal transplantation. In 3 patients MMC 0,1 mg/mL was used. After one and two years mean IOP was, respectively, 13,1 and 12,1 mmHg. IOP ≤ 16 mmHg was reached in 90% of patients without pressure lowering medication. No major complications were seen; no abnormal inflammatory reaction and no deformation or dislocation of the pupil occurred. Conclusion. By using the iris from the iridectomy as spacer under the scleral flap, fibrosis of the scleral flap is no longer possible. This iridenflip trabeculectomy technique gives an excellent complete success rate (IOP ≤ 16 mmHg) of 90%. A larger study is currently being done.

Retinal straylight before and after implantation of the Bag in the Lens IOL.

PURPOSE: To quantify the changes in retinal straylight that occur after implantation of the Bag in the Lens (BIL) IOL, which by design avoids the formation of posterior capsule opacification or any influence of the posterior lens capsule. METHODS: This prospective study included 81 eyes of 53 cataract patients planned for surgery with the BIL. Preoperatively and 6 months postoperatively their straylight level was determined using the compensation comparison method. RESULTS: After implantation of the BIL straylight significantly improved from 1.59 ± 0.26 preoperatively to 1.19 ± 0.21 log units postoperatively (paired t-test, P < 0.001). Postoperative straylight was within age-normal levels in 56.1% of the eyes and went below age-normal values in 40.2% of the eyes. Average postoperative straylight remained 0.27 log units (or 1.87×) above the age-independent base straylight value of 0.931 + 0.200. Postoperatively straylight was not significantly correlated with age (r(2) = 0.001), but it was significantly correlated with a regression model that combines both age and axial length (r(2) = 0.199). CONCLUSIONS: Retinal straylight after implantation of the BIL is comparable to what has been published for the early follow-up of other IOL types, suggesting that a clear posterior lens capsule does not seem to add to straylight. However, for all IOL types average postoperative straylight remains above the expected base level, possible due to nonlenticular age-related parameters or to the physiological response of the ocular tissues to the surgical act. This should be examined in further detail in future studies.

Influence of cataract morphology on straylight and contrast sensitivity and its relevance to fitness to drive.

AIMS: To evaluate straylight and contrast sensitivity in cataractous eyes of different morphologies, and to determine which type of cataract presents higher impairment of visual function, specifically compared to studies proposing new norms for European drivers. METHODS: Best-corrected visual acuity (BCVA), contrast sensitivity and straylight were measured in 97 cataractous eyes using respectively a Snellen chart, a Pelli-Robson chart and the compensation comparison method (C-Quant Straylight Meter). Cataracts were graded using the Lens Opacities Classification System III (LOCS III) and divided into 4 groups: nuclear, cortical, nuclear-cortical and posterior subcapsular cataract. These results were compared to data from 38 cataract-free control subjects. RESULTS: Contrast sensitivity was reduced and straylight increased in all cataract patients, most notably in posterior subcapsular and nuclear-cortical cataract. Contrast sensitivity and BCVA were correlated (r = 0.44), whereas straylight and BCVA were not. Applying cut-off values as proposed by European drivers studies of 1.25 log contrast sensitivity and 1.4 log straylight as safe margins for driving, 31% would be considered unfit to drive on the basis of contrast sensitivity and 78% on the basis of straylight, although their visual acuity was still above the current European visual acuity requirement for driving. CONCLUSIONS: Straylight and, to a lesser extent, contrast sensitivity are complementary to BCVA and should be taken into account when considering surgery or driving legality.

Prevalence of impairment of visual function in European drivers.

PURPOSE: This study aimed to investigate the prevalence of impairment of visual function amongst European drivers. METHODS: A total of 2422 drivers from five European countries underwent a battery of visual function tests, including tests for visual acuity (VA), visual field (VF), contrast sensitivity, straylight (glare sensitivity) and useful field of view (UFOV). Subjects belonged to the following age categories: 45-54 years; 55-64 years; 65-74 years, and ≥ 75 years. A group of subjects aged 20-30 years served as a reference group. Results were compared with current standards for the visual function of drivers in the EU. RESULTS: Visual acuity in 0.5% of the younger group and 5.3% of the eldest group was below the standard required for driving. Visual acuity after proper refraction adhered to the standard in the majority of cases. Visual field results were below standard or questionable in 2.7% and 2.4%, respectively, of subjects in the eldest group. In this eldest group, impaired contrast sensitivity was present in 6.3%, increased glare sensitivity in 29.5% and impaired UFOV in 21.6% of subjects, but, as there are no standards for these criteria, the exact level of prevalence depends on the definition of impairment. CONCLUSIONS: Prevalences of impairment of visual functions that are not included in current standards (particularly contrast sensitivity and glare sensitivity) are much higher than prevalences of functions that are included (VA and VF).

Cataract and pseudophakia in elderly European drivers.

PURPOSE: To evaluate the prevalence and association of different types and severities of cataract or pseudophakia with visual impairments in older European drivers. METHODS: In this prospective European multicenter study, 2211 active drivers, 45 years of age and older, participated in an ophthalmologic examination, the measurement of visual functions, and were asked to fill in the NEI-VFQ-25 and another questionnaire about driving habits, driving difficulties, and self-reported accidents. RESULTS: Prevalence of moderate and severe forms of cataract in an active driving population is lower than that in the general population, but could be found in both eyes in 20% (95% confidence interval [CI] 16%-25%) and 17% (95% CI:13%-21%) of subjects 75 years of age and older. In addition, there is a strong relationship between severity of cataract and parameters such as age, visual acuity, intraocular straylight, and contrast sensitivity. CONCLUSIONS: Cataract is not as highly prevalent in the elderly active driving population as in the general population, but is frequently present in drivers over 65 years of age. Lower prevalence of severe bilateral cataracts in countries with mandatory tests of visual functions of drivers suggest that this could be a suitable measure to detect and to reduce the number of active drivers with severe bilateral cataracts.

Straylight before and after LASEK in myopia: changes in retinal straylight.

PURPOSE: To quantify the changes in retinal straylight that occur after laser-assisted subepithelial keratectomy (LASEK). METHODS: This prospective study included 86 eyes of 49 patients who were scheduled for LASEK surgery. Patients were divided into groups based on their preoperative contact lens wear habits: rigid lenses (RCL), soft lenses (SCL), spectacles after a period of contact lenses (SaC), and spectacles only (Specs). Retinal straylight was tested before surgery and 6 months after surgery with the compensation comparison method. Straylight was also compared to a normal reference database. The difference with the average straylight increase with age, called base- and age-corrected (BAC) straylight, was also studied. RESULTS: Before surgery, BAC straylight was found to be strongly elevated, with a value of 0.15 +/- 0.14 log units. After LASEK, this decreased to 0.00 +/- 0.14 log units. The reduction was significant (paired t-test, P << 0.01) and correlated with preoperative BAC straylight levels (r(2) = 0.332; P << 0.01). There was no correlation between the straylight change and the spherical equivalent of the laser refractive correction (r(2) = 0.042; P = 0.059). Preoperative wear of soft contact lenses increased the BAC straylight by approximately 0.06 log units, with respect to the spectacles groups (P < 0.05, unpaired t-test), but after surgery, this difference was no longer found (P > 0.05). CONCLUSIONS: Higher than normal preoperative BAC straylight was found to normalize after LASEK refractive surgery. Wearing soft contact lenses causes an additional increase in preoperative BAC straylight that is eliminated after LASEK.

Surgical outcomes of intraocular lens exchange: five-year study.

PURPOSE: To report the indications, surgical complications, and outcomes of intraocular lens (IOL) exchange procedures performed over 5 years and to correlate the incidence of perioperative anterior vitrectomy in eyes previously treated by neodymium:YAG (Nd:YAG) laser capsulotomy. SETTING: Department of Ophthalmology, Antwerp University Hospital, Edegem, Belgium. METHODS: In this prospective study, all IOL exchange procedures performed between October 2002 and December 2007 were included. Surgical outcomes were correlated with indications, IOL position, targeted versus achieved refraction, preoperative Nd:YAG laser capsulotomy, and surgical complications. RESULTS: One hundred twenty-eight eyes (113 patients) had IOL exchange because of IOL opacification (31%), IOL decentration (19%), IOL dislocation (18%), capsule phimosis (14%), corneal endothelial cell decompensation (8%), IOL miscalculation (6%), damaged IOL (2%), or IOL-related chronic uveitis (2%). Before and after IOL exchange, respectively, the IOL was capsule fixated in 82% and 45% of eyes, iris fixated in 4% and 39% of eyes, and sulcus fixated in 7% and 15% of eyes. Iris-fixated IOLs had the lowest predictability of refractive outcome (mean 1.55 diopters). Intraocular lenses implanted using the bag-in-the-lens technique had the highest refractive outcome predictability (mean 0.51 D). CONCLUSIONS: Decentration of pseudoaccommodating IOLs accounted for 14% of all IOL exchanges. Vitreous loss necessitating anterior vitrectomy was strongly correlated with preoperative Nd:YAG laser capsulotomy. Postoperative visual acuity improved in all cases without preoperative ocular comorbidity.

Association of lens opacities, intraocular straylight, contrast sensitivity and visual acuity in European drivers.

PURPOSE: To study the relationship between lens opacity and intraocular straylight, visual acuity and contrast sensitivity. METHODS: We investigated 2422 drivers in five clinics in different European Union (EU) member states aged between 20 and 89 years as part of a European study into the prevalence of visual function disorders in drivers. We measured visual acuity [Early Treatment Diabetic Retinopathy Study (ETDRS) chart], contrast sensitivity (Pelli-Robson chart) and intraocular straylight (computerized straylight meter). Lens opacities were graded with the Lens Opacities Classification System III (LOCS) without pupillary dilation. Participants answered the National Eye Institute Visual Functioning Questionnaire - 25. RESULTS: Intraocular straylight was related more strongly to LOCS score than to both visual acuity and contrast sensitivity. Visual acuity and contrast sensitivity were correlated to each other well, but to intraocular straylight to a much lesser extent. Self-reported visual quality was best related to contrast sensitivity; night driving difficulty was best related to visual acuity. CONCLUSION: Straylight is found to have added value for visual function assessment in drivers, whereas if visual acuity is known contrast sensitivity has limited added value.

Continuous positive airway pressure therapy is associated with an increase in intraocular pressure in obstructive sleep apnea.

PURPOSE: Several reports have demonstrated an association between glaucoma and obstructive sleep apnea (OSA), though the origin of this association remains unknown. In the present study, the influence of OSA and continuous positive airway pressure (CPAP) therapy on intraocular pressure (IOP) and ocular perfusion pressure (OPP) was examined. METHODS: IOP, blood pressure, and pulse rate were measured every 2 hours during 24-hour sessions in 21 patients with newly diagnosed OSA. A first series of measurements was performed before CPAP therapy, and a second series was performed 1 month after the initiation of CPAP therapy. OPP was then calculated. RESULTS: Baseline measurements showed a significant nycththemeral fluctuation in the average IOP, with the highest IOPs at night. After 1 month of CPAP therapy, the average IOP was significantly higher than baseline. The increase in overnight IOP was also significantly higher. A 24-hour IOP fluctuation of > or =8 mm Hg was found in 7 patients at baseline and in 12 patients during CPAP therapy. The mean difference between trough and peak IOP was 6.7 +/- 1.5 mm Hg at baseline and 9.0 +/- 2.0 mm Hg during CPAP therapy. Thirty minutes after CPAP cessation a significant decrease in IOP was recorded. There was a statistically significant decrease in mean OPP during CPAP therapy. CONCLUSIONS: Patients with OSA demonstrated significant 24-hour IOP fluctuations, with the highest values at night. CPAP therapy causes an additional IOP increase, especially at night. Regular screening of visual fields and the optic disc is warranted for all patients with OSA, especially those treated with CPAP.

Straylight effects with aging and lens extraction.

PURPOSE: To assess possible gains and losses in straylight values among the population to consider straylight as added benefit of lens extraction. DESIGN: In this cross-sectional design, data from a multicenter study on visual function in automobile drivers were analyzed. METHODS: On both eyes of 2,422 subjects, visual acuity (logarithm of the minimum angle of resolution [logMAR] in steps of 0.02 log units), straylight on the retina (psychophysical compensation comparison method), and lens opacity (slit-lamp scoring using the Lens Opacities Classification System III [LOCS III] system) were determined. Three groups were defined: 220 pseudophakic eyes, 3,182 noncataractous eyes (average LOCS III score, <1.5), and 134 cataractous eyes (average LOCS III score, >3.0). RESULTS: Noncataractous straylight values increases strongly with age as: log(s) = constant + log(1 + (age / 65)(4)), doubling by the age of 65 years, and tripling by the age of 77 years. Population standard deviation around this age norm was approximately 0.10 log units. The cataract eyes (in this active driver group) had relatively mild straylight increase. In pseudophakia, straylight values may be very good, better even than in the noncataract group. Visual acuity and straylight were found to vary quite independently. CONCLUSIONS: Lens extraction holds promise not only to improve on the condition of the cataract eye, but also to improve on the age-normal eye. Lens extraction potentially reverses the strong age increase in straylight value, quite independently from visual acuity.

Intraocular lens centration and visual outcomes after bag-in-the-lens implantation.

PURPOSE: To examine the centration and visual outcomes after cataract surgery using the bag-in-the-lens (BIL) implantation technique. SETTING: University Hospital Antwerp, Department of Ophthalmology, Edegem, Belgium. METHODS: This study comprised 180 eyes of 125 patients who had cataract surgery with implantation of the BIL intraocular lens (IOL) between March 2002 and September 2005. Postoperative data at 5 weeks, 6 months, and 1 year were evaluated. The geometric center of the IOL, measured on a red reflex slitlamp photograph, was compared with the geometric center of the pupil and the limbus. RESULTS: The mean decentration compared with the limbus was 0.304 mm+/-0.17 (SD) at a mean angle of -24.9+/-113.3 degrees. Compared with the dilated pupil, the mean deviation was 0.256+/-0.15 mm at a mean angle of -5.2+/-119.0 degrees. The amount of decentration was stable during the postoperative follow-up period. There was no correlation between the amount of decentration and the visual outcomes (pupil: r=-0.07, P=.494; limbus: r=0.11, P=.304). CONCLUSIONS: Surgeon-controlled BIL centration was predictable 5 weeks and unchanged 6 months and 1 year postoperatively. It can therefore be concluded that capsular bag healing has no influence on BIL IOL centration over time.

Cumulative neodymium:YAG laser rates after bag-in-the-lens and lens-in-the-bag intraocular lens implantation: comparative study.

PURPOSE: To study the cumulative neodymium:YAG (Nd:YAG) laser rate after bag-in-the-lens implantation (Morcher 89A) and lens-in-the-bag implantation (Morcher 92S) of 2 intraocular lenses (IOLs) of the same biomaterial. SETTING: Department of Ophthalmology, University Hospital of Antwerp, Edegem, Belgium. METHODS: This study comprised 100 eyes of 87 patients who had the bag-in-the-lens IOL implantation between January 2000 and August 2004. The postoperative follow-up ranged between 17 and 72 months. One hundred eyes of 94 patients of the same age and with the same follow-up period received the lens-in-the-bag IOL. The cumulative Nd:YAG laser frequency rates in both groups were calculated, and the cumulative incidence rates were defined by Kaplan-Meier survival analysis. RESULTS: No Nd:YAG laser capsulotomy was performed in eyes having bag-in-the-lens IOL implantation. A laser capsulotomy was performed in 20 eyes having lens-in-the-bag IOL implantation; the cumulative frequency in this group was 2% at 1 year and 20% at 71 months, with a plateau beginning at 42 months. The cumulative incidence rate of Nd:YAG posterior capsulotomy was approximately 2% at 1 year, increasing to approximately 28% at 42 months. CONCLUSIONS: The cumulative Nd:YAG laser rate after bag-in-the-lens implantation was zero. A zero rate has not been reported with lens-in-the-bag implantation of an IOL of the same biomaterial or of other biomaterials, as published in the literature. Thus, it can be concluded that the bag-in-the-lens implantation technique has 100% effectiveness against posterior capsule opacification.

Age-related changes in the functional visual field: further evidence for an inverse Age x Eccentricity effect.

We assessed the performance of younger and older individuals by using the Attended Field of View test, a visual search task in which eye movements were allowed. When adjusting for slower processing in the older age group by log transformation, we observed significant effects of age, eccentricity, and Age x Eccentricity. Contrary to most previous findings, the Age x Eccentricity effect was "inverted" in that the difference between the age groups decreased as a function of eccentricity. The finding that the eccentricity effect of younger individuals was larger than that of older individuals was caused by large age-related differences in sensitivity for centrally located targets, even though differences with regard to foveal resolution were controlled. The results further indicated that, given a brief amount of time, older persons could process a smaller field of view than younger persons. Consequently, older persons were forced to resort to serial scanning for a larger part of the display, whereas younger persons could process a larger area in parallel.

Predicting practical fitness to drive in drivers with visual field defects caused by ocular pathology.

Vision, viewing efficiency, visual attention, and on-road driving performance were assessed in 100 participants with central and/or peripheral visual field defects caused by ocular pathology. Driving was evaluated by the Dutch driving license authority making use of the protocol for investigating practical fitness to drive. A smaller percentage of participants with central visual field defects passed the on-road driving test, in comparison with participants with peripheral or mild field defects. The predictive power of a model based on the current vision requirements for driving significantly increased when taking compensatory viewing efficiency into account. The results of the latter model were comparable to those of a model based on tests of visual attention and contrast sensitivity. Despite the increased explained variance of practical fitness to drive when taking higher-order visual functions into account, sensitivity and specificity remained quite low, limiting the use of these tests in identifying unfit drivers. Actual or potential applications of this research include the development of training programs to improve practical fitness to drive in drivers with visual field defects.

The effect of visual field defects on driving performance: a driving simulator study.

OBJECTIVES: To investigate the effect of visual field defects on driving performance, and to predict practical fitness to drive. METHODS: The driving performance of 87 subjects with visual field defects due to ocular abnormalities was assessed on a driving simulator and during an on-road driving test. OUTCOME MEASURES: The final score on the on-road driving test and simulator indexes, such as driving speed, viewing behavior, lateral position, time-headway, and time to collision. RESULTS: Subjects with visual field defects showed differential performance on measures of driving speed, steering stability, lateral position, time to collision, and time-headway. Effective compensation consisted of reduced driving speed in cases of central visual field defects and increased scanning in cases of peripheral visual field defects. The sensitivity and specificity of models based on vision, visual attention, and compensatory viewing efficiency were increased when the distance at which the subject started to scan was taken into account. CONCLUSIONS: Subjects with visual field defects demonstrated differential performance on several driving simulator indexes. Driving examiners considered reduced speed and increased scanning to be valid compensation for central and peripheral visual field defects, respectively. Predicting practical fitness to drive was improved by taking driving simulator indexes into account.

The effect of visual field defects on eye movements and practical fitness to drive.

Eye movements of subjects with visual field defects due to ocular pathology were monitored while performing a dot counting task and a visual search task. Subjects with peripheral field defects required more fixations, longer search times, made more errors, and had shorter fixation durations than control subjects. Subjects with central field defects performed less well than control subjects although no specific impairment could be pinpointed. In both groups a monotonous relationship was observed between the visual field impairment and eye movement parameters. The use of eye movement parameters to predict viewing behavior in a complex task (e.g. driving) was limited.