[show abstract][hide abstract] ABSTRACT: The effects of glaucoma on binocular visual sensitivity for the detection of various stimulus attributes are investigated at the fovea and in four paracentral retinal regions. The study employed a number of visual stimuli designed to isolate the processing of various stimulus attributes. We measured absolute contrast detection thresholds and functional contrast sensitivity by using Landolt ring stimuli. This psychophysical Landolt C-based contrast test of detection and gap discrimination allowed us to test parafoveally at 6 ° from fixation and foveally by employing interleaved testing locations. First-order motion perception was examined by using moving stimuli embedded in static luminance contrast noise. Red/green (RG) and yellow/blue (YB) colour thresholds were measured with the Colour Assessment and Diagnosis (CAD) test, which utilises random dynamic luminance contrast noise (± 45 %) to ensure that only colour and not luminance signals are available for target detection. Subjects were normal controls (n = 65) and glaucoma patients with binocular visual field defects (n = 15) classified based on their Humphrey Field Analyzer mean deviation (MD) scores. The impairment of visual function varied depending on the stimulus attribute and location tested. Progression of loss was noted for all tests as the degree of glaucoma increased. For subjects with mild glaucoma (MD -0.01 dB to -6.00 dB) significantly more data points fell outside the normal age-representative range for RG colour thresholds than for any other visual test, followed by motion thresholds. This was particularly the case for the parafoveal data compared with the foveal data. Thus, a multifaceted measure of binocular visual performance, incorporating RG colour and motion test at multiple locations, might provide a better index for comparison with quality of life measures in glaucoma.
Cell and Tissue Research 06/2013; · 3.68 Impact Factor
[show abstract][hide abstract] ABSTRACT: Questionnaires are commonly used as a proxy measure of clinical practice; however their application in a variety of healthcare settings has found significant self-reporting bias. The aim of this study is to estimate the validity of self-reporting as a measure of optometrist case-finding practice for glaucoma and the appropriate referral of suspects.
Two complementary approaches were used: (1) a sample of optometrists (N=34) on an ophthalmic list in West London were visited incognito by Standardised Patient (SP) volunteers aged over 54 who were trained to identify the components of a standard Sight Test. Optometrists from the same list were then invited to participate in a structured face-to-face interview regarding their case finding practice for glaucoma. The findings from the two sources were compared. (2) as part of a national glaucoma survey of optometrists, respondents (N=1264) were asked in a free text question for the information that they would include in a referral letter for suspect glaucoma. The responses were compared to the content of a sample of glaucoma referral letters (N=571) obtained from consultant ophthalmologists across the UK. In each case, the degree of correspondence ('match') between reported practice and actual practice was assessed by chi-square analysis.
For the SP study there was incomplete correspondence between the questionnaire and SP reports in several areas e.g. questions relating to a complete history and symptoms, measurement of intra-ocular pressure and visual fields. Complete correspondence was found for questions asking about the routine assessment of ocular health and refraction. For the referral study, correspondence between survey findings and referral letters was obtained for IOP only. No correspondence was found for disc assessment, visual fields or family history of glaucoma.
The overall findings from both studies indicate that self-reported clinical practice questionnaires overestimate routine tests undertaken by optometrists in practice. Although there was a good correspondence for mandatory tests, correspondence was poor for discretionary tests. These findings should be borne in mind in all questionnaire studies that report current practice in glaucoma case-finding.
Ophthalmic and Physiological Optics 02/2012; 32(3):234-41. · 1.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: In the UK, the majority of cases of chronic open angle glaucoma are detected by community optometrists following a routine sight test. However, there is potential for variability in case finding strategies used. The aim of this study was to carry out a national web-based survey to determine current diagnostic tests used by optometrists in glaucoma case finding.
Optometrists on the Association of Optometrists (AOP) electronic database were invited to participate. The survey was open for 16 weeks between April and July 2008.
A total of 1875 optometrists were eligible to enter the survey, of which 1264 answered the questions relating to diagnostic equipment. Respondents were asked to indicate their usual method of examining the optic nerve head. Direct ophthalmoscopy only was used by 25% with the majority (62%) using a combination of direct and slit-lamp binocular indirect methods. The vast majority of optometrists (78%) used non-contact tonometry to measure intraocular pressure, with only 16% routinely using a Goldmann or Perkins applanation tonometer. The perimeter most frequently used was either one of the Henson range of instruments (39%) or the Humphrey Field Analyser (22%). A smaller number of optometrists (<5%) had access to more specialised imaging equipment, such as HRT, GDx or OCT.
The results of the survey demonstrate that UK optometrists are well equipped to carry out case finding for chronic open angle glaucoma, although there is a lack of standardisation with respect to equipment used.
Ophthalmic and Physiological Optics 07/2011; 31(4):353-9. · 1.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: To compare the clinical and financial effectiveness of two optometric-led enhanced glaucoma referral schemes in the Bexley Care Trust area.
Over a 12-month period all suspect glaucoma/Ocular Hypertension (OHT) referrals from optometrists relating to patients registered with Bexley GPs were analysed. All these patients were examined under one of two schemes. One was an enhanced glaucoma repeat measurement (EGRM) scheme in which the referring optometrist conducted the repeated tests him/herself prior to referral or non-referral. The alternative was a refinement pathway (RCAS) using a small team of accredited community optometrists.
During the full year commencing April 2007, repeat measures using the EGRM scheme resulted in 76% of patients not being referred. In 44.5% of all EGRM patients, where raised intraocular pressure (IOP) was found by non-contact tonometry (NCT), repeated measurement by Goldmann/Perkins applanation tonometry resulted in readings that were <22 mmHg, or that had less than a 5 mmHg difference between the two eyes. Financial review demonstrated that the EGRM achieved 62% savings when compared with HES tariff while RCAS resulted in a saving of 3.5%.
Using a primary care repeat measurement scheme to support referral decision-making demonstrated substantial cost benefit while onward referral for refinement by accredited optometrists was essentially cost-neutral compared with HES tariff. Local schemes foster fragmentation and consideration should be given to a service which covers a large population area.
Ophthalmic and Physiological Optics 07/2011; 31(4):343-52. · 1.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: To compare comfort-related outcomes when wearing rigid gas permeable (RGP) contact lenses made of two different materials and using two cleaning regimes.
In a double-masked lens material cross-over study, subjects (n = 28 who completed the study) were refitted with new lenses made from (A) Boston XO material in one eye and made from (B) ONSI-56 material in the other eye. The lenses made from materials A and B were worn on the right eye and the left eye following the pattern AB-BA-AB (or vice versa) during the first, second, and third 5 week trial periods respectively. Miraflow cleaner (1st and 2nd period) was replaced by Boston Advance cleaner in the 3rd period. Comfort-related outcomes were assessed by a numerical rating scale (NRS) after each period. Subjects rated six comfort-related factors: satisfaction, sharpness of vision, end of day comfort, maximum comfortable wearing time, maximum wearing time and foreign body feeling. Additionally we obtained subjects' preferences for type of lens and lens cleaner during an exit interview. The sessile drop method was used to measure static contact angles.
The mean of the contact angle measured for the Boston XO material was 93.3° and for the ONSI-56 material was 75.8 °. Mean 'end of the day comfort', 'satisfaction' and 'lens feeling' scores reached statistical significance (anova periods 1, 2 and 3, p's: 0.005, 0.028, 0.046, n = 23) with marginal differences in favour of those eyes that had worn lenses made of the ONSI-56 material (differences in mean scores on a 1-10 NRS never exceeded 0.7, 0.5 and 0.2 points in periods 1, 2, 3 respectively). At the exit interview 60% of the subjects (n = 17) were not able to express a preference for wearing either of the lenses, while 29% reported some preference for lenses made of the ONSI-56 material (n = 8) and 11% for wearing lenses made of the Boston XO material (n = 3) within one or more periods.
The differences in comfort-related outcomes between contact lenses made from two different materials, with sessile contact angles that differed by 17.5°, were small. Although some observed comfort differences reached statistical significance, none of these differences were sufficiently large to support a clinically significant difference in comfort between the two materials. We recommend that both the sessile drop and the captive bubble contact angles, measured according to current standards, are made available to practitioners.
Ophthalmic and Physiological Optics 03/2011; 31(2):190-9. · 1.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: To compare the effect on optometric variables of reading text presented in 2-D and 3-D on two types of stereoscopic display.
This study measured changes in binocular visual acuity, fixation disparity, aligning prism, heterophoria, horizontal fusional reserves, prism facility and accommodation responses for near of subjects after completing ten consecutive reading tasks of 1 minute each. The tasks consisted of reading words on a polarized two-view (n = 39) and an auto-stereoscopic lenticular nine-view display (n = 19) with the text presented without or with stereoscopic disparity at 3 m. Performance was assessed by measuring reading speed and symptoms were rated by the Convergence Insufficiency Symptom Survey (CISS) questionnaire.
With both types of display, CISS scores at least doubled immediately after subjects viewed the 3-D text image in an extreme stereoscopic condition compared to the 2-D condition (p < 0.001), while the mean reading speed slowed (p < 0.001). Mean changes in optometric test variables were not clinically or statistically significant (p values > 0.05). After the 3-D task one participant showed consistent clinically meaningful decreases in convergent fusional break and recovery points for both displays.
When healthy adult subjects with normal binocular vision viewed text images at 3 m in extreme 3-D display settings for a short period of time there were no clinically significant mean changes in optometric test variables compared with 2-D viewing.
Ophthalmic and Physiological Optics 01/2011; 31(1):33-44. · 1.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: This paper aims to identify the barriers to case-finding for primary open angle glaucoma (POAG) as perceived by community optometrists in the United Kingdom (UK).
An anonymous, online survey to investigate the current mode of optometric practice for the detection of POAG was developed. The survey included a free-text question relating to barriers to case-finding for the disease. Optometrists on the Association of Optometrists (AOP) electronic database were invited to participate. The survey was open for 16 weeks between April and July 2008.
A total of 1680 responses was received to the survey, of which 1293 (77%) answered the free-text question relating to perceived barriers. Eighty-eight per cent of these reported one or more barriers to the detection of glaucoma in the community, most commonly: time constraints limiting the options for repeat testing and lack of financial remuneration to perform the additional tests required. Barriers were less frequently reported in Scotland, with 23.4% of optometrists reporting no barriers compared to only 12% in England, 6% in Northern Ireland and 4% in Wales.
In general, UK optometrists believed that their ability to detect POAG in the community is hampered by time and financial constraints. However, barriers were significantly fewer in Scotland, where optometrists have different contractual terms of service with the NHS than their counterparts in the rest of the UK.
Ophthalmic and Physiological Optics 11/2010; 30(6):847-53. · 1.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: A recent review found standardised patient (SP) methodology to be the gold standard method for evaluating clinical care. Alternative methods include record abstraction and computerised clinical vignettes. SPs were compared to clinical records and to computerised vignettes in order to assess whether record abstraction and vignettes are accurate measures of clinical care provided within optometry.
A total of 111 community optometrists in the south east of the UK consented to be visited by unannounced actors for an eye examination. The SPs received extensive training to enable accurate reporting of the content of the eye examinations using checklists. Clinical records were requested from optometrists who chose to receive feedback following the SP visits. The SP checklists were used as a guide to extract relevant information from the clinical records. An opportunity was made available to all UK qualified optometrists, through publicity in the College of Optometrists' monthly newsletter, the Association of Optometrists' monthly newsletter (Blink) and the UK optometry e-mail discussion list to complete three computerised clinical vignettes by performing a virtual eye examination using an on-line optometric record card. The average differences were calculated between the record abstraction and vignette results compared to the standardised patient encounter findings for different domains of an eye examination. Chi-square analyses were performed on the tests which were of the greatest clinical significance for each scenario.
The average overall difference for information gathered from record abstraction compared to the standardised patient encounter ranged from +2 to -26% (positive values indicate items that were recorded on the clinical records but not reported by the SP). For history and symptoms, the average difference ranged from -9 to -26%; for the proportion of tests performed during the examination this value ranged from +2 to -24% and for management issues the difference ranged from -1 to -4%. The average overall difference for the vignette data compared to the standardised patient encounter ranged from 0 to +26% (positive values indicate items that were not carried out in a clinical setting, as recorded by the SP, but were described by optometrists who completed the vignette as tests they would have carried out). For history and symptoms, the average difference for the vignette data ranged from +2 to +26%; from 0 to +20% for tests performed during the eye examination and from 0 to +11% for management.
Different methods of measuring clinical care capture different elements of clinical practice and are prone to different biases. This three-way comparison indicates that clinical records tend to under-estimate actual care provided, while vignette scores tend to over-estimate clinical performance. Low participation rates mean that the participating optometrists could be described as a 'self-selected sample'. This is a limitation of the research and the conclusions should be considered with this in mind. The significance of these findings for future research and for litigation and disciplinary cases is discussed.
Ophthalmic and Physiological Optics 05/2010; 30(3):209-24. · 1.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: Glaucoma is a progressive eye disease and a leading cause of visual disability. Automated assessment of the visual field determines the different stages in the disease process: it would be desirable to link these measurements taken in the clinic with patient's actual function, or establish if patients compensate for their restricted field of view when performing everyday tasks. Hence, this study investigated eye movements in glaucomatous patients when viewing driving scenes in a hazard perception test (HPT).
The HPT is a component of the UK driving licence test consisting of a series of short film clips of various traffic scenes viewed from the driver's perspective each containing hazardous situations that require the camera car to change direction or slow down. Data from nine glaucomatous patients with binocular visual field defects and ten age-matched control subjects were considered (all experienced drivers). Each subject viewed 26 different films with eye movements simultaneously monitored by an eye tracker. Computer software was purpose written to pre-process the data, co-register it to the film clips and to quantify eye movements and point-of-regard (using a dynamic bivariate contour ellipse analysis). On average, and across all HPT films, patients exhibited different eye movement characteristics to controls making, for example, significantly more saccades (P<0.001; 95% confidence interval for mean increase: 9.2 to 22.4%). Whilst the average region of 'point-of-regard' of the patients did not differ significantly from the controls, there were revealing cases where patients failed to see a hazard in relation to their binocular visual field defect.
Characteristics of eye movement patterns in patients with bilateral glaucoma can differ significantly from age-matched controls when viewing a traffic scene. Further studies of eye movements made by glaucomatous patients could provide useful information about the definition of the visual field component required for fitness to drive.
PLoS ONE 01/2010; 5(3):e9710. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: In a double-masked randomized controlled crossover study we investigated both the retinal responses to straylight, and the effects of lens cleaners on straylight values, in two different RGP contact lens materials.
Thirty patients (20-59 years) wearing RGP lenses were refitted with new lenses made of Boston XO material in one eye and made of Comfort O2 (ONSI-56) material in the other eye. Reported wetting angles for the Boston XO material (103 degrees ) and for the ONSI-56 material (7.2 degrees ) were obtained by sessile drop measurements. After refitting, the study comprised three 5-week trial periods. In Period 1 half of the participants (Group A) wore Boston XO lenses in their right eye and Comfort O2 (ONSI-56) lenses in their left eye, and the other half (Group B) vice versa. In Period 2 Group A wore Comfort O2 (ONSI-56) lenses in their right eye and Boston XO lenses in their left, and Group B vice versa. All participants used Miraflow cleaner during periods 1 and 2. In Period 3, during which all participants used Boston cleaner, Group A wore Boston XO lenses in their right eye and Comfort O2 (ONSI-56) lenses in their left eye and Group B vice versa. Straylight data (log S) were obtained with and without contact lenses using the Oculus C-Quant straylight meter in all three periods. Central corneal thickness (CCT) was measured in the second and third periods.
When not wearing lenses (n = 60 eyes) at the end of the second 5 week trial period straylight was measured twice with averages of 1.07 log S, and the corrected CCT measurements averaged 546 mum. Straylight values with Comfort O2 (ONSI-56) reached 1.15 log S at the end of both the second (n = 25 eyes) and third periods (n = 23 eyes). Straylight values with Boston XO were 1.17 log S (n = 26 eyes) at the end of the second period, and 1.16 log S (n = 25 eyes) at the end of the third period.
Existing RGP lens wearers refitted with new lenses with different contact angles, made of Boston XO and Comfort O2 (ONSI-56) showed, over three 5 week periods, relatively small increases in straylight, which were functionally comparable, irrespective of the type of lens material or lens cleaner used. At every visit, straylight values and CCTs returned to baseline levels after RGP lens removal, confirming that the straylight fluctuations were mainly due to scattering from the RGP lenses; or tear film interaction; or a combination of both.
Ophthalmic and Physiological Optics 10/2009; 29(5):497-508. · 1.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: A recent review found standardised patient (SP) methodology to be the gold standard method for evaluating clinical care. We compared the clinical records describing the content of optometric eye examinations with the actual content, as revealed by SPs.
We recruited 111 community optometrists in the South East of the UK who consented to be visited by unannounced actors for an eye examination. The actors received extensive training to enable accurate reporting of the content of the eye examinations, via an audio recording and a checklist completed for each clinical encounter. Each participating optometrist was visited by three standardised patients. Upon completion of the standardised patient visits, copies of the clinical records were requested. Using the SP findings as the gold standard, the information gathered from the clinical record was classified for each quality criterion as true positive (reported by SP and documented on the record card), false negative (reported by SP but not documented on the record card), false positive (not reported by SP but recorded on the record card) and true negative (not reported by SP and not recorded on the record card).
Compared to the gold standard, false positives were identified during record abstraction in 4% of cases and false negatives in 18% of cases. For symptoms and history, the proportion of false negatives ranged from 15% to 25% and 3 to 4% for false positives. The proportion of false negatives for tests performed during the eye examinations ranged from 12% to 22% and false positives ranged from 2% to 6%. Optometrists give patients more verbal advice than is indicated in their records (false negatives, 11-19%). Five to 15% of practitioners recorded patient management and advice that was not reported by the SPs.
Our findings regarding optometric consultation mirror the findings in other healthcare disciplines: clinical records are an imperfect representation of the content of a clinical consultation. Clinical records are subject to a recording bias leading to both under- and over-estimation of the care provided due to the presence of false negatives and false positives. This study has important implications for clinico-legal cases, where clinical records are a key item of evidence; and our findings indicate that accurate record-keeping should be a priority for optometric continuing education.
Ophthalmic and Physiological Optics 08/2009; 29(4):383-96. · 1.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: Standardised patients (SPs) are the gold standard methodology for evaluating clinical care. This approach was used to investigate the content of optometric eyecare for a presbyopic patient who presented with recent photopsia.
A total of 102 community optometrists consented to be visited by an actor for a recorded eye examination. This actor received extensive training to enable accurate reporting of the content of the eye examinations, via an audio recording and a checklist completed for each clinical encounter. The actor presented unannounced (incognito) as a 59-year-old patient seeking a private eye examination and complaining of recent onset flashing lights. The results of each clinical encounter were recorded on a pre-designed checklist based on evidence-based reviews on photopsia, clinical guidelines and the views of an expert panel.
The presence of the symptom of photopsia was proactively detected in 87% of cases. Although none of the optometrists visited asked all seven gold standard questions relating to the presenting symptoms of flashing lights, 35% asked four of the seven questions. A total of 85% of optometrists asked the patient if he noticed any floaters in his vision and 36% of optometrists asked if he had noticed any shadows in his vision. The proportion of the tests recommended by the expert panel that were carried out varied from 33 to 100% with a mean of 67%. Specifically, 66% recommended dilated fundoscopy to be carried out either by themselves or by another eyecare practitioner, and 29% of optometrists asked the patient to seek a second opinion regarding the photopsia. Of those who referred, 70% asked for the referral to be on the same day or within a week.
SP encounters are an effective way of measuring clinical care within optometry and should be considered for further comparative measurements of quality of care. As in research using SPs in other healthcare disciplines, our study has highlighted substantial differences between different practitioners in the duration and depth of their clinical investigations. This highlights the fact that not all eye examinations are the same but inherently different and that there is no such thing as a 'standard sight test'. Future optometric continuing education could focus on history taking, examination techniques and referral guidelines for patients presenting with symptoms of posterior vitreous detachment, retinal breaks and secondary retinal detachment.
Ophthalmic and Physiological Optics 04/2009; 29(2):105-26. · 1.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: Standardised patient (SP) methodology is the gold standard for evaluating clinical practice. We investigated the content of optometric eyecare for an early presbyopic SP of African racial descent, an "at-risk" patient group for primary open-angle glaucoma (POAG).
A trained actor presented unannounced as a 44-year-old patient of African racial descent, complaining of recent near vision difficulties, to 100 community optometrists for an audio-recorded eye examination. The eye examinations were subsequently assessed via a checklist based on evidence-based POAG reviews, clinical guidelines and expert panel opinion.
Ninety-five per cent of optometrists carried out optic disc assessment and tonometry, which conforms to the UK College of Optometrists' advice that those patients aged >40 years should receive at least two of the following tests: tonometry, optic disc assessment, visual field testing. Thirty-five per cent of optometrists carried out all of these tests and 6% advised the SP of increased POAG risk in those of African racial descent.
SP encounters are an effective measure of optometric clinical practice. As in other healthcare disciplines, there are substantial differences between optometrists in the depth of their clinical investigations, challenging the concept of a "standard sight test". There is a need for continuing professional development (CPD) in glaucoma screening, in which the increased risk of POAG in those of African racial descent should be emphasised.
The British journal of ophthalmology 01/2009; 93(4):492-6. · 2.92 Impact Factor
[show abstract][hide abstract] ABSTRACT: A recent review found standardised patient (SP) methodology to be the gold standard methodology for evaluating clinical care. We used this to investigate the content of optometric eye care for a young myopic patient with headaches suggestive of migraine.
We recruited 100 community optometrists who consented to be visited by an unannounced actor for an eye examination and to have that eye examination recorded. The actor received extensive training to enable accurate reporting of the content of the eye examinations, via an audio recording and a checklist completed for each clinical encounter. The actor presented as a 20-year-old student seeking a private eye examination and complaining of symptoms suggestive of migraine headaches. The results of each clinical encounter were recorded on a pre-designed checklist based on evidence-based reviews on headaches, clinical guidelines and the views of an expert panel of optometrists.
The presence of headache was detected in 98% of cases. Eight standard headache questions were considered to be the gold standard for primary care headache investigation. Although none of the optometrists asked all of these questions, 22% asked at least four of the eight questions. Sixty-nine per cent of practitioners asked the patient to seek a medical opinion regarding the headaches. The proportion of the tests recommended by the expert panel that was carried out varied from 33% to 89% and the durations of the eye examination varied from 5 to 50 min.
SP encounters are an effective way of measuring clinical care within optometry and should be considered for further comparative measurements of quality of care. As in research using SPs in other healthcare disciplines, our study has highlighted substantial differences between different practitioners in the duration and depth of their clinical investigations. This highlights the fact that not all eye examinations are the same and that there is no such thing as a 'standard sight test'. We recommend that future optometric continuing education could usefully focus on migraine diagnosis and assessment.
Ophthalmic and Physiological Optics 10/2008; 28(5):404-21. · 1.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: Macular pigment (MP) is found in diurnal primate species when vision spans a range of ambient illumination and is mediated by cone and rod photoreceptors. The exact role of MP remains to be determined. In this study we investigate two new hypotheses for possible MP functions.
As MP absorption coincides partly with that of rhodopsin, MP may reduce rod signal effectiveness in the mesopic range, thus extend the usefulness of cone-mediated vision into the mesopic range. Forward light scatter in the eye can reduce retinal image contrast. If blue light contributes significantly to intraocular scatter, selective blue light absorption by MP could reduce the effects of scatter.
We investigated 34 subjects from a carotenoid supplementation trial. The measurements included high mesopic contrast acuity thresholds (CATs), macular pigment optical density (MPOD), wavefront aberrations, and scattered light. The measurements were made after 6 months of daily supplementation with zeaxanthin (Z, OPTISHARP), lutein (L), a combination of the two (C), or placebo (P), and again after a further 6 months of doubled supplementation.
The data reveal a trend toward lower CATs in all groups supplemented, with a statistically significant improvement in the lutein group (p = 0.001), although there was no correlation with MPOD. Light scattering in the eye and the root-mean-square wavefront aberrations show decreasing trends as a result of supplementation, but no correlation with MPOD.
The results suggest that supplementation with L or Z increases MPOD at the fovea and at 2.5 degrees , and that supplementation can improve CATs at high mesopic levels and hence visual performance at low illumination.
Ophthalmic and Physiological Optics 08/2006; 26(4):362-71. · 1.74 Impact Factor