Central Field Loss Research Articles

Objective Analysis of Performance of Activities of Daily Living in People With Central Field Loss

People with central visual field loss (CFL) adopt various strategies to complete activities of daily living (ADL). Using objective movement analysis, we compared how three ADLs were completed by people with CFL compared with age-matched, visually healthy individuals. Fourteen participants with CFL (age 81 ± 10 years) and 10 age-matched, visually healthy (age 75 ± 5 years) participated. Three ADLs were assessed: pick up food from a plate, pour liquid from a bottle, and insert a key in a lock. Participants with CFL completed each ADL habitually (as they would in their home). Data were compared with visually healthy participants who were asked to complete the tasks as they would normally, but under specified experimental conditions. Movement kinematics were compared using three-dimension motion analysis (Vicon). Visual functions (distance and near acuities, contrast sensitivity, visual fields) were recorded. All CFL participants were able to complete each ADL. However, participants with CFL demonstrated significantly (P < 0.05) longer overall movement times, shorter minimum viewing distance, and, for two of the three ADL tasks, needed more online corrections in the latter part of the movement. Results indicate that, despite the adoption of various habitual strategies, participants with CFL still do not perform common daily living tasks as efficiently as healthy subjects. Although indices suggesting feed-forward planning are similar, they made more movement corrections and increased time for the latter portion of the action, indicating a more cautious/uncertain approach. Various kinematic indices correlated significantly to visual function parameters including visual acuity and midperipheral visual field loss.

A Portable Platform for Evaluation of Visual Performance in Glaucoma Patients.

PurposeTo propose a new tablet-enabled test for evaluation of visual performance in glaucoma, the PERformance CEntered Portable Test (PERCEPT), and to evaluate its ability to predict history of falls and motor vehicle crashes.DesignCross-sectional study.MethodsThe study involved 71 patients with glaucomatous visual field defects on standard automated perimetry (SAP) and 59 control subjects. The PERCEPT was based on the concept of increasing visual task difficulty to improve detection of central visual field losses in glaucoma patients. Subjects had to perform a foveal 8-alternative-forced-choice orientation discrimination task, while detecting a simultaneously presented peripheral stimulus within a limited presentation time. Subjects also underwent testing with the Useful Field of View (UFOV) divided attention test. The ability to predict history of motor vehicle crashes and falls was investigated by odds ratios and incident-rate ratios, respectively.ResultsWhen adjusted for age, only the PERCEPT processing speed parameter showed significantly larger values in glaucoma compared to controls (difference: 243ms; P<0.001). PERCEPT results had a stronger association with history of motor vehicle crashes and falls than UFOV. Each 1 standard deviation increase in PERCEPT processing speed was associated with an odds ratio of 2.69 (P = 0.003) for predicting history of motor vehicle crashes and with an incident-rate ratio of 1.95 (P = 0.003) for predicting history of falls.ConclusionA portable platform for testing visual function was able to detect functional deficits in glaucoma, and its results were significantly associated with history of involvement in motor vehicle crashes and history of falls.

Driving with Central Visual Field Loss II: How Scotomas above or below the Preferred Retinal Locus (PRL) Affect Hazard Detection in a Driving Simulator.

We determined whether binocular central scotomas above or below the preferred retinal locus affect detection of hazards (pedestrians) approaching from the side. Seven participants with central field loss (CFL), and seven age-and sex-matched controls with normal vision (NV), each completed two sessions of 5 test drives (each approximately 10 minutes long) in a driving simulator. Participants pressed the horn when detecting pedestrians that appeared at one of four eccentricities (-14°, -4°, left, 4°, or 14°, right, relative to car heading). Pedestrians walked or ran towards the travel lane on a collision course with the participant’s vehicle, thus remaining in the same area of the visual field, assuming participant's steady forward gaze down the travel lane. Detection rates were nearly 100% for all participants. CFL participant reaction times were longer (median 2.27s, 95% CI 2.13 to 2.47) than NVs (median 1.17s, 95%CI 1.10 to 2.13; difference p<0.01), and CFL participants would have been unable to stop for 21% of pedestrians, compared with 3% for NV, p<0.001. Although the scotomas were not expected to obscure pedestrian hazards, gaze tracking revealed that scotomas did sometimes interfere with detection; late reactions usually occurred when pedestrians were entirely or partially obscured by the scotoma (time obscured correlated with reaction times, r = 0.57, p<0.001). We previously showed that scotomas lateral to the preferred retinal locus delay reaction times to a greater extent; however, taken together, the results of our studies suggest that any binocular CFL might negatively impact timely hazard detection while driving and should be a consideration when evaluating vision for driving.

A computational account on the development of a preferred retinal locus

A saccade brings a retinal locus to a target in the visual field. For normally sighted individuals, this retinal locus is the fovea. Central field loss (CFL) caused by macular degeneration often leads to the adoption of a preferred retinal locus (PRL) in the peripheral retina for saccades and fixation. Factors underlying the development of a PRL are not known. Here we show that a conceptually simple computational model can account for the formation of a PRL and its idiosyncrasies. We assume that the visual system always intends to aim the retinal locus with the highest expected post-saccade acuity at the saccade target. The expected post-saccade acuity of a retinal locus is a function of the physiological acuity at and around the locus and the expected saccade error. The expected saccade error is a combination of motor error that is proportional to the saccade amplitude (vector error) and the spatial uncertainties associated with the retinal locus and the saccade target (endpoint errors). We assume that the motor error does not improve, but the spatial uncertainties associated with the neural representation of the endpoints are optimally re-estimated after each saccade from the observed saccade error. A generic forgetting function is assumed to prevent spatial uncertainty from vanishing. Simulations showed that immediately after CFL, the utilized retinal loci are close to the edge of the scotoma on the side nearest to saccade targets. After each saccade, spatial uncertainties associated with the pre-saccade target and utilized retinal locus decrease. Decrease in spatial uncertainty increases the expected post-saccade acuity of the retinal locus. The net effect is that a previously selected retinal locus is more likely to be selected for a future saccade, further reducing its spatial uncertainty, and forming the PRL. Idiosyncrasies at the early stages of CFL strongly influence PRL formation. Meeting abstract presented at VSS 2015. Language: en

Optic neuropathy in late-onset neurodegenerative Chédiak–Higashi syndrome

BackgroundThe classic form of Chédiak–Higashi syndrome (CHS), an autosomal recessive disorder of lysosomal trafficking with childhood onset caused by mutations in LYST, is typified ophthalmologically by ocular albinism with vision...

Similar Sensitivity to Ladder Contours in Macular Degeneration Patients and Controls.

PurposeTo determine whether people with central field loss (CFL) from macular degeneration have improved ability to recognize a particularly difficult spatial configuration embedded in noise, the peripherally-viewed ‘ladder contour’. The visibility of these configuration has been linked to general contour integration ability and crowding limitations in peripheral vision.MethodsWe used a trial-based yes-no task. CFL patients and normally-sighted controls performed the task, looking for ladder contours embedded in a field of randomly oriented Gabor patches, at a range of stimulus presentation times (varying stimulus difficulty). Viewing eccentricity in CFL patients was set by their preferred retinal loci (PRLs) and matched artificially in the control group. The contours were presented so as to be tangent to the CFL region, given a patient’s PRL location.ResultsCFL and normally-sighted groups performed similarly on the task. The only significant determinant of performance was the viewing eccentricity.ConclusionsCFL patients do not seem to develop any improved ability to recognize ladder contours with their parafoveal retina, which suggests that there is no underlying improvement in contour integration or reduction in crowding limitations in the region of the PRL despite extended daily use.

Repeatability of Nidek MP-1 Fixation Measurements in Patients With Bilateral Central Field Loss.

Visual performance in patients with bilateral central field loss is related to fixation stability. This study evaluated the repeatability of visual-fixation parameters in patients with bilateral central field loss, measured with the MP-1 microperimeter for fixation durations on the order of 15 to 30 seconds. Bivariate contour ellipse area (BCEA), and the eccentricity and meridian of the preferred retinal locus (PRL) were determined in 56 eyes of 56 patients, sampled at two investigational sites. Repeatability and agreement were assessed by estimating 95% limits of agreement for each parameter from two fixation examinations conducted on the same day. The 95% confidence intervals (CI) for log BCEA and for PRL eccentricity and meridian were ±0.67 log deg2, ±2.0°, and ±65.9°, respectively. Each CI decreased substantially if a small number of outlying data points were excluded. For all parameters, the mean difference between the two fixation examinations was close to zero. For most patients with bilateral central field loss, the repeatability of estimated BCEA and PRL eccentricity and meridian is good. When repeated estimates of fixation parameters do not agree, the absence of a well-developed PRL or the use of multiple PRLs may be suspected.

Do not lose sight of syphilis

Ocular manifestations of syphilis are uncommon and typically occur during the secondary stage of the disease, causing significant sequelae if left untreated. This is an unusual presentation of syphilis in a 36-year-old man. He was referred by his optometrist to an ophthalmologist with a five day history of central and para-central bilateral visual field loss preceded by two days of photopsia. There were no other accompanying symptoms, including headache, nausea, ocular pain, nor other focal neurological deficits. However, he had experienced a Jarisch-Herxheimer reaction after receiving cefazolin prophylaxis prior. On examination, he had greatly reduced vision in both eyes, markedly on the left eye with acuity of 6/60 and bilateral optic discs swelling. He had negative HIV, hepatitis B and C serology, but syphilis serology had positive RPR, EIA and TPHA. MRI examination of the brain and orbits was unremarkable except for inflammatory changes in the mastoids. A diagnosis of bilateral treponemal optic neuritis was made, and he was commenced on oral prednisone for 3 days and intravenous penicillin G for 2 weeks and his visual acuity improved markedly.

Comparison of risk factors for initial central scotoma versus initial peripheral scotoma in normal-tension glaucoma.

PurposeTo investigate the risk factors for initial central scotoma (ICS) compared with initial peripheral scotoma (IPS) in normal-tension glaucoma (NTG).MethodsFifty-six NTG patients (56 eyes) with an ICS and 103 NTG patients (103 eyes) with an IPS were included. Retrospectively, the differences were assessed between the two groups for baseline characteristics, ocular factors, systemic factors, and lifestyle factors. Also, the mean deviation of visual field was compared between the two groups.ResultsPatients from both ICS and IPS groups were of similar age, gender, family history of glaucoma, and follow-up periods. Frequency of disc hemorrhage was significantly higher among patients with ICS than in patients with IPS. Moreover, systemic risk factors such as hypotension, migraine, Raynaud's phenomenon, and snoring were more prevalent in the ICS group than in the IPS group. There were no statistical differences in lifestyle risk factors such as smoking or body mass index. Pattern standard deviation was significantly greater in the ICS group than in the IPS group, but the mean deviation was similar between the two groups.ConclusionsNTG Patients with ICS and IPS have different profiles of risk factors and clinical characteristics. This suggests that the pattern of initial visual field loss may be useful to identify patients at higher risk of central field loss.

Gas tamponade combined with laser photocoagulation therapy for congenital optic disc pit maculopathy.

To evaluate the long-term clinical efficacy and safety of gas tamponade combined with laser photocoagulation for optic disc pit maculopathy. Seven consecutive patients with unilateral maculopathy associated with optic disc pit and one patient with bilateral optic disc pit maculopathy were given octafluoropropane (C3F8) tamponade combined with focal laser photocoagulation treatment. Patients were followed up for 21-62 months after treatment. Main outcomes were determined by optical coherence tomography (OCT) and best-corrected visual acuity (BCVA). Treatment with C3F8 tamponade followed by laser photocoagulation in ODP maculopathy patients resulted in resolution of sub-retinal and/or intra-retinal fluid in six out of eight patients. The remaining two patients had significant reduction in fluid, as determined by OCT, and funduscopy, as well as an improvement in anatomical architecture. Visual acuity improved obviously in seven eyes and remained stable in two eyes. Central visual field loss after photocoagulation was not clinically appreciable by visual field examination. No post-operative complications of maculopathy occurred during the follow-up period. Although repeated treatment was needed in some patients, C3F8 tamponade combined with laser photocoagulation is still a simple, effective, minimally invasive, and economic therapy for optic disc pit maculopathy.

Risk factors for an initial central scotoma compared with an initial peripheral scotoma

AbstractPurpose To investigate the risk factors for an initial central scotoma (ICS) compared with an initial peripheral scotoma (IPS) in normal tension glaucoma (NTG).Methods Sixty NTG patients (60 eyes) with an ICS and 106 NTG patients (106 eyes) with an IPS were included. Retrospectively, the differences were assessed with baseline characteristics, ocular factors, systemic factors, and life style factors between two groups. Also, the parameters of visual field were compared between two groups. Clinical characteristics and various systemic factors were analyzed between the 2 groups.Results Patients from both ICS and IPS groups were of similar age, gender, family history of glaucoma, and follow‐up periods. Frequency of disc hemorrhage was significantly higher among patients with an ICS than in patients with an IPS (p&lt;0.001). Moreover, systemic risk factors such as hypotension, migraine, Raynaud’s phenomenon, and snoring were more prevalent in the ICS group than in the IPS group (p&lt;0.001, p=0.002, p= 0.007, p= 0.009, respectively). There were no statistically differences in lifestyle risk factor such as smoking or body mass index. Pattern standard deviation was significantly greater in the ICS group than in the IPS group (p=0.005), but the mean deviation was similar between the 2 groups (p=0.096).Conclusion NTG patients with ICS and IPS have different profiles of risk factors and clinical characteristics. This suggests that the pattern of initial VF loss may be useful to identify patients at higher risk of central field loss.

A cohort study of duplex Doppler examinations of the carotid artery in primary open angle glaucoma.

ObjectivesTo explore the possibility of pathological change in the common carotid artery at the bifurcation and in the internal carotid artery beyond the bifurcation which could contribute to a reduced diastolic pressure as observed in primary open angle glaucoma.DesignDuplex ultrasonic examinations of carotid bifurcations were conducted on 80 patients. Carotid artery defects were allocated into three types: no demonstrable flow defects, internal carotid artery abnormalities and disease in the carotid bulb.SettingBristol Royal Infirmary Vascular Laboratory.ParticipantsEighty patients (mean age 69.6 years) providing a total of 160 sides to the analysis.Main outcome measuresAn estimated central retinal artery pressure, intraocular pressure and field loss were recorded for each side measured.ResultsDoppler investigations revealed significant levels of pathological change in the internal carotid distinct from changes at the carotid bulb. The disease revealed in the internal carotid artery was significantly associated with intraocular pressure (p = 0.032), with an effect small to medium in magnitude. The Q2 measure, derived from mean arterial pressure and intraocular pressure, was also substantively associated with disease in the internal carotid artery. Both intraocular pressure and the Q2 measure effectively discriminated between groups, with field loss providing rather less discriminating capability. There was a strong trend towards a higher intraocular pressures and a greater visual field loss with internal carotid artery disease.ConclusionsPathological changes in the extra cranial carotid artery in primary open angle glaucoma exceed those in the arteries classified as normal. The presence of disease specifically in the internal carotid artery emphasised the need for a mechanism for the evaluation of the internal carotid apart from the carotid bulb. A basis for clarifying the presence of an ischaemic zone is proposed.

Difference in the posterior pole profiles associated with the initial location of visual field defect in early-stage normal tension glaucoma.

To identify the differences in posterior pole profiles between early normal tension glaucoma (NTG) patients with an initial central visual field (VF) loss and those with a peripheral VF loss. Normal tension glaucoma patients with parafoveal scotoma (PFS; within a central 10° of fixation; superior, n=47; inferior, n=24) and peripheral nasal step (PNS; VF defect in the nasal meridian outside 10° of fixation; superior, n=27; inferior, n=32) in either hemifield were enrolled, if their mean deviation was greater than -10 decibels (dB). Disc tilt (tilt ratio), disc torsion, area of peripapillary atrophy and disc-foveal angle (angle between a horizontal line through the disc centre and the line connecting the fovea and the disc centre) were analysed from red-free fundus photographs. The mean disc-foveal angles (shortest diameter) in PNS and PFS groups were 6.2±4.5 and 7.7±4.0°, respectively. In multivariate analysis, eyes with PFS were associated with a greater disc-foveal angle, compared with PNS (p=0.042). In subgroup analysis, superior PFS group showed greater disc-foveal angle compared with inferior PFS group (p=0.018). In the PNS group, the direction of disc torsion was associated with superior and inferior hemifield defects (p=0.004). The posterior pole profiles were different in NTG patients according to their location of damage. Disc-foveal angle was the major determinant of the VF location in patients with VF loss at the central region and disc torsion in patients with loss at the peripheral region.

Eye movements and reading speed in macular disease: the shrinking perceptual span hypothesis requires and is supported by a mediation analysis.

Reading speed of patients with central field loss (CFL) correlates with the size of saccades (measured in letters per forward saccade [L/FS]). We assessed whether this effect is mediated by the total number of fixations, by the average fixation duration, or by a mixture of both. We measured eye movements (with a video eye tracker) of 35 AMD and 4 Stargardt patients (better eye decimal acuity from 0.08-0.3) while they monocularly read single-line French sentences continuously displayed on a screen. All patients had a dense scotoma covering the fovea, as assessed with MP1 microperimetry, and therefore used eccentric viewing. Results were analyzed with regression-based mediation analysis, a modeling framework that informs on the underlying factors by which an independent variable affects a dependent variable. Reading speed and average fixation duration are negatively correlated, a result that was not observed in prior studies with CFL patients. This effect of fixation duration on reading speed is still significant when partialling out the effect of the total number of fixations (slope: -0.75, P < 0.001). Despite this large effect of fixation duration, mediation analysis shows that the effect of L/FS on reading speed is fully mediated by the total number of fixations (effect size: 0.96; CI [0.82, 1.12]) and not by fixation duration (effect size: 0.02; CI [-0.11, 0.14]). Results are consistent with the shrinking perceptual span hypothesis: reading speed decreases with the average number of letters traversed on each forward saccade, an effect fully mediated by the total number of fixations.

Fixation Locus in Patients with Bilateral Central Scotomas for Targets that Perceptually Fill In

In this experiment, we investigated whether target type affects the retinal fixation location and stability in patients with bilateral central scotomas and, specifically, whether targets expected to perceptually fill in are imaged at or near the vestigial fovea. The retinal location and stability of fixation were measured using the Nidek MP-1 microperimeter in 12 patients with bilateral central scotomas for six types of fixation target, three expected to fill in and three that included letters. The approximate position of the vestigial fovea was delineated in 10 of the patients either by using residual retinal landmarks or by locating the residual foveal pit in a dense macular scan obtained with a Spectralis optical coherence tomographer. Fixation location and stability were compared for the different target types and referenced to the position of the vestigial fovea. All of the subjects except one fixated consistently on targets that included a letter using peripheral retinal locations outside of the central scotoma. Eleven of the 12 subjects used a retinal location closer to the vestigial fovea to fixate targets expected to fill in compared with letters. Although four of the subjects imaged the filled-in targets at or within a half degree of the vestigial fovea, six other subjects imaged the filled-in targets at a retinal locus removed from the vestigial fovea. Target type produced no overall significant difference in fixation stability, specified in terms of bivariate contour ellipse area. However, in some individual subjects, fixation tended to be more stable on letter targets than on filled-in targets. In patients with central field loss, letter targets generate more consistent fixation behavior than filled-in targets and should be used for eccentric viewing training and perimetry.

Visual Attention Measures Predict Pedestrian Detection in Central Field Loss: A Pilot Study

PurposeThe ability of visually impaired people to deploy attention effectively to maximize use of their residual vision in dynamic situations is fundamental to safe mobility. We conducted a pilot study to evaluate whether tests of dynamic attention (multiple object tracking; MOT) and static attention (Useful Field of View; UFOV) were predictive of the ability of people with central field loss (CFL) to detect pedestrian hazards in simulated driving.Methods11 people with bilateral CFL (visual acuity 20/30-20/200) and 11 age-similar normally-sighted drivers participated. Dynamic and static attention were evaluated with brief, computer-based MOT and UFOV tasks, respectively. Dependent variables were the log speed threshold for 60% correct identification of targets (MOT) and the increase in the presentation duration for 75% correct identification of a central target when a concurrent peripheral task was added (UFOV divided and selective attention subtests). Participants drove in a simulator and pressed the horn whenever they detected pedestrians that walked or ran toward the road. The dependent variable was the proportion of timely reactions (could have stopped in time to avoid a collision).ResultsUFOV and MOT performance of CFL participants was poorer than that of controls, and the proportion of timely reactions was also lower (worse) (84% and 97%, respectively; p = 0.001). For CFL participants, higher proportions of timely reactions correlated significantly with higher (better) MOT speed thresholds (r = 0.73, p = 0.01), with better performance on the UFOV divided and selective attention subtests (r = −0.66 and −0.62, respectively, p<0.04), with better contrast sensitivity scores (r = 0.54, p = 0.08) and smaller scotomas (r = −0.60, p = 0.05).ConclusionsOur results suggest that brief laboratory-based tests of visual attention may provide useful measures of functional visual ability of individuals with CFL relevant to more complex mobility tasks.

Characterization of Field Loss Based on Microperimetry Is Predictive of Face Recognition Difficulties

To determine how visual field loss as assessed by microperimetry is correlated with deficits in face recognition. Twelve patients (age range, 26-70 years) with impaired visual sensitivity in the central visual field caused by a variety of pathologies and 12 normally sighted controls (control subject [CS] group; age range, 20-68 years) performed a face recognition task for blurred and unblurred faces. For patients, we assessed central visual field loss using microperimetry, fixation stability, Pelli-Robson contrast sensitivity, and letter acuity. Patients were divided into two groups by microperimetry: a low vision (LV) group (n = 8) had impaired sensitivity at the anatomical fovea and/or poor fixation stability, whereas a low vision that excluded the fovea (LV:F) group (n = 4) was characterized by at least some residual foveal sensitivity but insensitivity in other retinal regions. The LV group performed worse than the other groups at all blur levels, whereas the performance of the LV:F group was not credibly different from that of the CS group. The performance of the CS and LV:F groups deteriorated as blur increased, whereas the LV group showed consistently poor performance regardless of blur. Visual acuity and fixation stability were correlated with face recognition performance. Persons diagnosed as having disease affecting the central visual field can recognize faces as well as persons with no visual disease provided that they have residual sensitivity in the anatomical fovea and show stable fixation patterns. Performance in this task is limited by the upper resolution of nonfoveal vision or image blur, whichever is worse.

Spatial Changes of Central Field Loss in Diabetic Retinopathy After Laser

To explore the spatial distribution of central visual field loss in untreated proliferative diabetic retinopathy (PDR) and to quantify the effect of medium-pulse Optos-guided 20-millisecond Pascal laser treatment on the central field. Visual field data (Swedish Interactive Threshold Algorithm 24-2) from 99 eyes (66 patients) with treatment-naive PDR were used to train a self-organizing map (SOM) that classified the defects into nine patterns. Twenty-eight eyes of 23 patients treated with 20-millisecond Pascal retinal laser photocoagulation underwent Optos widefield fundus fluorescein angiography (WF-FFA) at baseline and 3 months after treatment. Postlaser changes in SOM patterns and global indices were analyzed. Visual field defect changes (Total Deviation [TD]) with eccentricity and extent of initial loss were analyzed. Grading of WF-FFA after laser was undertaken by two masked retina specialists. At baseline, 44.4% of PDR eyes showed early visual field loss patterns (1 to 3), with 23.2% classified into the advanced patterns (7 to 9). Mild SOM patterns had more superior hemifield field defects, whereas advanced patterns involved both superior and inferior hemifield field loss. After laser, a significant shift to early SOM patterns were observed (p = 0.02), as well as improvement of Mean Deviation and Pattern Standard Deviation (p = 0.003 and p = 0.06, respectively). Improvement of TD was commonly observed in test locations of 0 to 10, 10 to 20, and 20 to 30 degrees. Greater improvement was observed with deeper baseline TD (p < 0.001). Masked WF-FFA image grading showed 78.6% PDR regression. The SOM method is a promising technique to classify and monitor over time PDR-associated visual field defects. Medium-pulse Optos-guided 20-millisecond Pascal laser treatment improved the spatial patterns and global parameters of central field defects.

Objectively determined refraction improves peripheral vision.

The purpose of this study was twofold: to verify a fast, clinically applicable method for determining off-axis refraction and to assess the impact of objectively obtained off-axis refractive correction on peripheral low-contrast visual acuity. We measured peripheral low-contrast resolution acuity with Gabor patches both with and without off-axis correction at 20 degrees in the nasal visual field of 10 emmetropic subjects; the correction was obtained using a commercial open-field Hartmann-Shack wavefront sensor, the COAS-HD VR aberrometer. Off-axis refractive errors were calculated for a 5-mm circular pupil inscribed within the elliptical wavefront by COAS using the instruments' inbuilt "Seidel sphere" method. Most of the subjects had simple myopic astigmatism, at 20 degrees in the nasal visual field ranging from -1.00 to -2.00 DC, with axis orientations generally near 90 degrees. The mean uncorrected and corrected low-contrast resolution acuities for all subjects were 0.92 and 0.86 logMAR, respectively (an improvement of 0.06 logMAR). For subjects with a scalar power refractive error of 1.00 diopters or more, the average improvement was 0.1 logMAR. The observed changes in low-contrast resolution acuity were strongly correlated with off-axis astigmatism (Pearson r = 0.95; p < 0.0001), the J180 cross-cylinder component (Pearson r = 0.82; p = 0.0034), and power scalar (Pearson r = -0.75; p = 0.0126). The results suggest that there are definite benefits in correcting even moderate amounts of off-axis refractive errors; in this study, as little as -1.50 DC of off-axis astigmatism gave improvements of up to a line in visual acuity. It may be even more pertinent for people who rely on optimal peripheral visual function, specifically those with central visual field loss; the use of open-field aberrometers could be clinically useful in rapidly determining off-axis refractive errors specifically for this patient group who are generally more challenging to refract.

Kinematic analysis of step ascent among patients with central visual field loss

Vision is of paramount importance in regulating adaptive gait. Using three-dimensional motion analysis, the current study investigated how central visual field loss (CFL) affects step ascent. Ten patients with chronic CFL (77±10 years) and 13 visual normal participants (72±6 years) walked up to and ascended a single step (of varying height). Movement kinematics assessed the period immediately prior to and during step ascent. Compared to visual normal participants, patients with CFL exhibited a lower lead foot horizontal crossing velocity, increased lead limb swing time and increased head flexion (looking down at more immediate areas of the ground/step). They also took longer to initiate the step up, transfer weight to the lead foot upon landing on the upper level and increased trail limb swing time when negotiating the medium and high step height. Increased variability was also shown in a number of dependant measures. Data indicate that during step ascent, patients with CFL exhibit a cautious stepping strategy when compared to visual normal participants. This cautious strategy becomes increasingly evident when negotiating higher step heights, as shown by an increased planning time prior to entering the relatively unstable period of single support during the step up. The increased variability among CFL patients increases their likelihood of experiencing dynamic instability and falling during step ascent.