New Italian version of the Wilkins Rate of Reading Test: Materials for repeated-measure designs in optometry and neuropsychological research.

PURPOSE: To develop a series of equivalent passages of text in Italian, according to the principles of the Wilkins Rate of Reading Test (WRRT), suitable for both clinical examination and scientific research when equivalent stimuli are needed to compare performance in repeated-measure designs. METHOD: Fifteen high-frequency Italian words (matched for grammatical class and length to the English WRRT) were used to generate 15 different 10-line meaningless passages, according to the design principles of the English WRRT. Thirty-two healthy Italian-speaking higher education students read the passages aloud according to a fixed randomisation schedule. Performance was recorded digitally to measure reading speed and accuracy offline. Equivalence between the passages and the practice and fatigue effects for both reading speed and accuracy were examined as well as test-retest reliability. RESULTS: No significant difference in reading speed and accuracy was found between the passages. There was a significant practice effect on reading speed but not accuracy, with the first presented passage read significantly slower than the others. There was no evidence of a fatigue effect. Reading speed, the reference metric for the WRRT, showed good test-retest reliability. CONCLUSIONS: The passages of the Italian version of the WRRT were equivalent to each other. The practice effect suggests that familiarisation with the test (i.e., reading at least one matrix of words) should be carried out before consecutive/repeated reading of different passages for experimental or clinical purposes.

Worsening vision at age 4-5 in England post-COVID: Evidence from a large database of vision screening data.

PURPOSE: Myopia prevalence has increased in the UK at age 10-16y, but little is known about younger children. We hypothesise that if the 'myopia epidemic' is affecting young children, then there will be increasing rates of bilateral reduced unaided vision (V) at vision screenings of children 4-5 years of age. METHODS: Retrospective anonymised data from computerised vision screening at age 4-5 years were analysed from serial cross-sectional data. Refractive error is not assessed in UK vision screening, so vision was investigated. Data were only included from schools that screened every year from 2015/16 to 2021/22. The criterion used was unaided monocular logMAR (automated letter-by-letter scoring) vision >0.20 in both the right and left eyes, so as to maximise the chances of detecting bilateral, moderate myopia rather than amblyopia. RESULTS: Anonymised raw data were obtained for 359,634 screening episodes from 2075 schools. Once schools were excluded where data were not available for every year and data were cleaned, the final database comprised 110,076 episodes. The proportion (percentage and 95% CI) failing the criterion from 2015/16 to 2021/22 were 7.6 (7.2-8.0), 8.5 (8.1-8.9), 7.5 (7.1-7.9), 7.8 (7.4-8.2), 8.7 (8.1-9.2), 8.5 (7.9-9.0) and 9.3 (8.8-9.7), respectively. The slope of the regression line showed a trend for increasing rates of reduced bilateral unaided vision, consistent with increasing frequency of myopia (p = 0.06). A decreasing linear trendline was noted for children 'Under Professional Care'. CONCLUSIONS: For children 4-5 years of age, there were signs of reduced vision over the last 7 years in England. Consideration of the most likely causes support the hypothesis of increasing myopia. The increase in screening failures highlights the importance of eye care in this young population.

Randomised controlled trial of an accommodative support lens designed for computer users.

PURPOSE: Accommodative support (AS) lenses are a low add progressive addition spectacle lens designed to ease symptoms in computer vision syndrome (CVS). The study aims to investigate if (1) AS lenses improve CVS symptoms; (2) binocular/accommodative functions predict a benefit from AS lenses and (3) wearing AS lenses for six months impacts on binocular/accommodative functions. METHODS: Pre-presbyopic adults with symptoms of CVS (Computer Vision Syndrome Questionnaire, CVS-Q© , score ≥ 6) were randomly allocated to wear AS lenses or control single vision (SV) lenses. The CVS-Q© and a battery of optometric tests were applied at baseline and after three and six months. Participants and researchers were masked to participant group. After six months, the SV group were unmasked and changed to AS lenses and one week later asked to choose which they preferred. RESULTS: The change in CVS-Q© scores from baseline to six months did not differ significantly in the two groups. At the end of the one week period, when the control group wore the AS lenses, control group participants were significantly more likely to prefer AS lenses to SV lenses. No optometric functions correlated with the benefit from AS lenses. AS lenses did not have any adverse effects on binocular or accommodative function. CONCLUSIONS: In pre-presbyopic adults, there was no greater improvement in CVS-Q© scores in the group wearing AS lenses than in the control group. No adverse effects on optometric function (including accommodation) are associated with wearing AS lenses.

Referrals from community optometrists to the hospital eye service in Scotland and England.

OBJECTIVES: This audit assesses communication between community optometrists (COs) and hospital eye service (HES) in Scotland and England. METHODS: Optometric referrals and replies were extracted from six practices in Scotland and England. If no reply was found, replies/records were copied from HES records. De-identified referrals, replies and records were audited against established standards, evaluating whether referrals were necessary, accurate and directed to the appropriate professional. The referral rate (RR) and referral reply rate (RRR) were calculated. RESULTS: From 905 de-identified referrals, RR ranged from 2.6 to 8.7%. From COs' perspective, the proportion of referrals for which they received replies ranged from 37 to 84% (Scotland) and 26 to 49% (England). A total of 88-96% of referrals (Scotland) and 63-76% (England) were seen in the HES. Adjusting for cases when it is reasonable to expect replies, RRR becomes 45-92% (Scotland) and 38-62% (England) with RRR significantly greater in Scotland (P = 0.015). Replies were copied to patients in 0-21% of cases. Referrals were to the appropriate service and judged necessary in ≥90% of cases in both jurisdictions. Accuracy of referral ranged from 89 to 97% (Scotland) and 81 to 98% (England). The reply addressed the reason for referral in 94-100% of cases (Scotland) and 93-97% (England) and was meaningful in 95-100% (Scotland) and 94-99% (England). CONCLUSIONS: Despite the interdisciplinary joint statement on sharing patient information, this audit highlights variable standard of referrals and deficits in replies to the referring COs, with one exception in Scotland. Replies from HES to COs are important for patient care, benefitting patients and clinicians and minimising unnecessary HES appointments.

Design and use of vignettes to investigate referral decision-making by optometrists

Purpose: This study describes the design and application of a range of online clinical vignettes for measuring the impact of Continuing Education and Training (CET) and identifying unwarranted variation in optometric decision-making concerning referrals to secondary care.MethodsTwenty computerised vignettes were developed to assess clinical and referral management decisions taken in primary care optometry. The online system was specifically designed to present vignettes (ten pre-CET and ten post-CET) that avoided prompting correct answers. The main study group was qualified optometrists (N = 31) who chose any CET options available to United Kingdom optometrists over six months. Participants submitted a record of the CET undertaken, which was compared with an anonymised General Optical Council (GOC) reference sample. The vignettes were also completed by newly-qualified (N = 18) and pre-registration (N = 11) groups.ResultsCET had no significant correlation (p = 0.37) with improvement in optometric clinical decision-making and referral practice (qualified group). Selection bias affected this group who had more CET points (p = 0.008) and peer discussion points (p = 0.003) than the GOC reference sample. Results were indicative due to small sample sizes. Newly-qualified practitioners were significantly more likely to refer than the qualified group (p = 0.004). Number of referrals decreased with time since qualification (p = 0.006). (AU)

Is reading rate in digital eyestrain influenced by binocular and accommodative anomalies?

Introduction: Symptoms experienced when using digital devices are known as digital eyestrain (DES) or computer vision syndrome. They can be categorised as either external (associated with dry eye) or internal (related to refractive, accommodative or binocular vision anomalies). In a large cohort of adults with DES, we investigate the prevalence of binocular and accommodative anomalies, contrasting different diagnostic approaches, to evaluate potential mechanisms for the benefit from +0.75D addition lens that has been previously reported. Methods: Participants (20−40y) were selected using the Computer Vision Syndrome Questionnaire (CVS-Q) tool as suffering with DES. A comprehensive eye examination was given to each participant, and this paper concentrates on “internal factors”, detected with a refraction and comprehensive testing of binocular and accommodative functions. The effects of low-powered addition lenses (+0.50D, +0.75D, +1.25D; and plano controls) were assessed by double-masked testing with the Wilkins Rate of Reading Test (WRRT) and by subjective preference. Results: As previously reported, most participants showed a subjective preference for one of the three convex lenses we used, with +0.75D chosen most frequently. Performance at the WRRT was significantly improved with +0.50D and +0.75D, but not +1.25D. Using a variety of diagnostic criteria, there were no strong associations between WRRT results or CVS-Q scores and any binocular or accommodation functions. The one finding of significance is that a disproportionate number of participants who benefited from adds had an eso-fixation disparity on the near Mallett unit, although this only affected 5% of the population. Conclusions: DES is a collection of diverse symptoms that have a multifactorial aetiology. In the sample described here, binocular and accommodative anomalies do not seem to be a major cause of DES. (AU)

Design and use of vignettes to investigate referral decision-making by optometrists.

PURPOSE: This study describes the design and application of a range of online clinical vignettes for measuring the impact of Continuing Education and Training (CET) and identifying unwarranted variation in optometric decision-making concerning referrals to secondary care. METHODS: Twenty computerised vignettes were developed to assess clinical and referral management decisions taken in primary care optometry. The online system was specifically designed to present vignettes (ten pre-CET and ten post-CET) that avoided prompting correct answers. The main study group was qualified optometrists (N = 31) who chose any CET options available to United Kingdom optometrists over six months. Participants submitted a record of the CET undertaken, which was compared with an anonymised General Optical Council (GOC) reference sample. The vignettes were also completed by newly-qualified (N = 18) and pre-registration (N = 11) groups. RESULTS: CET had no significant correlation (p = 0.37) with improvement in optometric clinical decision-making and referral practice (qualified group). Selection bias affected this group who had more CET points (p = 0.008) and peer discussion points (p = 0.003) than the GOC reference sample. Results were indicative due to small sample sizes. Newly-qualified practitioners were significantly more likely to refer than the qualified group (p = 0.004). Number of referrals decreased with time since qualification (p = 0.006). CONCLUSION: Computerised vignettes are a useful tool for comparing referral decisions between groups. Recruiting clinicians for time-consuming vignette studies is challenging. Strategies to reduce unwarranted variation in optometry, including support for newly-qualified optometrists, require further investigation.

Investigation of the efficacy of an online tool for improving the diagnosis of macular lesions imaged by optical coherence tomography

Purpose: Optical coherence tomography (OCT) is a non-invasive method for diagnosis and monitoring of retinal (typically, macular) conditions. The unfamiliar nature of OCT images can present considerable challenges for some community optometrists.The purpose of this research is to develop and assess the efficacy of a novel internet resource designed to assist optometrists in using OCT for diagnosis of macular disease and patient management.MethodsAn online tool (OCTAID) has been designed to assist practitioners in the diagnosis of macular lesions detected by OCT. The effectiveness of OCTAID was evaluated in a randomised controlled trial comparing two groups of practitioners who underwent an online assessment (using clinical vignettes) based on OCT images, before (exam 1) and after (exam 2) an educational intervention. Participants’ answers were validated against experts’ classifications (the reference standard). OCTAID was randomly allocated as the educational intervention for one group with the control group receiving an intervention of standard OCT educational material. The participants were community optometrists.ResultsRandom allocation resulted in 53 optometrists receiving OCTAID and 65 receiving the control intervention. Both groups performed similarly at baseline with no significant difference in mean exam 1 scores (p = 0.21). The primary outcome measure was mean improvement in exam score between the two exam modules. Participants who received OCTAID improved their exam score significantly more than those who received conventional educational materials (p = 0.005).ConclusionUse of OCTAID is associated with an improvement in the combined skill of OCT scan recognition and patient management decisions. (AU)

Is reading rate in digital eyestrain influenced by binocular and accommodative anomalies?

INTRODUCTION: Symptoms experienced when using digital devices are known as digital eyestrain (DES) or computer vision syndrome. They can be categorised as either external (associated with dry eye) or internal (related to refractive, accommodative or binocular vision anomalies). In a large cohort of adults with DES, we investigate the prevalence of binocular and accommodative anomalies, contrasting different diagnostic approaches, to evaluate potential mechanisms for the benefit from +0.75D addition lens that has been previously reported. METHODS: Participants (20-40y) were selected using the Computer Vision Syndrome Questionnaire (CVS-Q) tool as suffering with DES. A comprehensive eye examination was given to each participant, and this paper concentrates on "internal factors", detected with a refraction and comprehensive testing of binocular and accommodative functions. The effects of low-powered addition lenses (+0.50D, +0.75D, +1.25D; and plano controls) were assessed by double-masked testing with the Wilkins Rate of Reading Test (WRRT) and by subjective preference. RESULTS: As previously reported, most participants showed a subjective preference for one of the three convex lenses we used, with +0.75D chosen most frequently. Performance at the WRRT was significantly improved with +0.50D and +0.75D, but not +1.25D. Using a variety of diagnostic criteria, there were no strong associations between WRRT results or CVS-Q scores and any binocular or accommodation functions. The one finding of significance is that a disproportionate number of participants who benefited from adds had an eso-fixation disparity on the near Mallett unit, although this only affected 5% of the population. CONCLUSIONS: DES is a collection of diverse symptoms that have a multifactorial aetiology. In the sample described here, binocular and accommodative anomalies do not seem to be a major cause of DES. Nevertheless, in view of the multifactorial aetiology it is recommended that patients with the symptoms of DES are assessed with a comprehensive eye examination. Patients with an esophoric fixation disparity on the near Mallett unit are particularly likely to benefit from near additions.

Referrals from community optometrists to the hospital eye service in England.

PURPOSE: In the UK, most referrals to the hospital eye service (HES) originate from community optometrists (CO). This audit investigates the quality of referrals, replies, and communication between CO and the HES. METHODS: Optometric referrals and replies were extracted from three practices in England. If no reply letter was found, the records were searched at each local HES unit, and additional replies or records copied. De-identified referrals, replies and records were audited by a panel against established standards to evaluate whether the referrals were necessary, accurate and directed to the appropriate professional. The referral rate (RR) and referral reply rate (RRR) were calculated. RESULTS: A total of 459 de-identified referrals were extracted. The RR ranged from 3.6%-8.7%. The proportion of referred patients who were seen in the HES unit was 63%-76%. From the CO perspective, the proportion of referrals for which they received replies ranged from 26%-49%. Adjusting the number of referrals for cases when it would be reasonable to expect an HES reply, RRR becomes 38%-62%. Patients received a copy of the reply in 3%-21% of cases. Referrals were made to the appropriate service in over 95% of cases, were judged necessary in 93%-97% and were accurate in 81%-98% of cases. The referral reply addressed the reason for the referral in 93%-97% and was meaningful in 94%-99% of cases. The most common conditions referred were glaucoma, cataract, anterior segment lesions, and neurological/ocular motor anomalies. The CO/HES dyad (pairing) in the area with the lowest average household income had the highest RR. CONCLUSIONS: In contrast with the Royal College of Ophthalmologists/College of Optometrists joint statement on sharing patient information, CO referrals often do not elicit a reply to the referring CO. Replies from the HES to COs are important for patient care, benefitting patients and clinicians, and minimising unnecessary HES appointments.

Investigation of the efficacy of an online tool for improving the diagnosis of macular lesions imaged by optical coherence tomography.

PURPOSE: Optical coherence tomography (OCT) is a non-invasive method for diagnosis and monitoring of retinal (typically, macular) conditions. The unfamiliar nature of OCT images can present considerable challenges for some community optometrists. The purpose of this research is to develop and assess the efficacy of a novel internet resource designed to assist optometrists in using OCT for diagnosis of macular disease and patient management. METHODS: An online tool (OCTAID) has been designed to assist practitioners in the diagnosis of macular lesions detected by OCT. The effectiveness of OCTAID was evaluated in a randomised controlled trial comparing two groups of practitioners who underwent an online assessment (using clinical vignettes) based on OCT images, before (exam 1) and after (exam 2) an educational intervention. Participants' answers were validated against experts' classifications (the reference standard). OCTAID was randomly allocated as the educational intervention for one group with the control group receiving an intervention of standard OCT educational material. The participants were community optometrists. RESULTS: Random allocation resulted in 53 optometrists receiving OCTAID and 65 receiving the control intervention. Both groups performed similarly at baseline with no significant difference in mean exam 1 scores (p = 0.21). The primary outcome measure was mean improvement in exam score between the two exam modules. Participants who received OCTAID improved their exam score significantly more than those who received conventional educational materials (p = 0.005). CONCLUSION: Use of OCTAID is associated with an improvement in the combined skill of OCT scan recognition and patient management decisions.

Randomised controlled trial of corneal vs. scleral rigid gas permeable contact lenses for keratoconus and other ectatic corneal disorders.

PURPOSE: To compare the comfort and visual performance of corneal rigid gas permeable contact lenses (CoL) and scleral rigid gas permeable contact lenses (SL) in participants with corneal ectasia, successfully wearing "habitual" CoL. METHODS: In a randomised controlled trial (RCT) with a 2 × 2 crossover, 34 participants were recruited and randomised into two groups. Group 1 (sequence AB), were fitted in period 1, with new CoL and after a 4-week washout period, in which habitual CoL were worn, were fitted with and crossed-over to SL, period 2. Group 2 (sequence BA), were first fitted with SL in period 1 and after a washout period of 4 weeks, crossed-over to new CoL, period 2. The median lengths in weeks of Periods 1 and 2 were: 17.5 (IQR 12.4) and 14.5 (IQR 6.2) respectively. The outcome measures for visual performance were best corrected visual acuity and the contrast sensitivity function. Vision related quality of life (Qol) was assessed using the National Eye Institute Visual Function Questioannaire-25 and reported subjective perception of vision (SPV) and reported subjective perception of comfort (SPC) scores, recorded on a scale from 1-10. The final outcome measure was the selection of the preferred lens type at the completion of the RCT. RESULTS: For the 30 who completed the trial, significantly higher SPC scores were found for SL compared to CoL (p = 0.002). Significantly higher SPC scores for CoL were found in participants who selected CoL as their preferred lens for future use, compared to those who selected SL (p = 0.009). All other outcomes exhibited no significant difference between the experimental lenses. There was no significant difference (p=0.86) in the proportion preferring CoL (53%) and SL (47%). CONCLUSION: Significantly better comfort was reported for SL compared with CoL. Significantly higher comfort in CoL was found in those who preferred CoL, than those who preferred SL. Successful CoL wearers whose SPC in CoL is <7 are likely to achieve better comfort with SL. On average, successful CoL wearers found SL more comfortable and there are unlikely to be any significant visual or visual Qol advantage or disadvantage in refitting successful CoL wearers with keratoconus and other corneal ectasia disorders, with SL and vice versa.

Sources of error in clinical measurement of the amplitude of accommodation.

Measurement of the amplitude of accommodation is established as a procedure in a routine optometric eye examination. However, clinical methods of measurement of this basic optical function have several sources of error. They are numerous and diverse, and include depth of focus, reaction time, instrument design, specification of the measurement end-point, specification of the reference point of measurement, measurement conditions, consideration of refractive error, and psychological factors. Several of these sources of inaccuracy are composed of multiple sub-sources, and many of the sub-sources influence the common methods of measurement of amplitude of accommodation. Consideration of these sources of measurement error casts doubt on the reliability of the results of measurement, on the validity of established normative values that have been produced using these methods, and on the value of reports of the results of surgery designed to restore accommodation. Clinicians can reduce the effects of some of the sources of error by modifying techniques of measurement with existing methods, but a new method may further improve accuracy.

Does an iPad fixation disparity test give equivalent results to the Mallett near fixation disparity test?

BACKGROUND: Various instruments have been developed to measure aligning prism, the prism that eliminates a fixation disparity (associated heterophoria). This includes the established Mallett near vision unit and recently developed Thomson Vision Toolbox on the iPad. With no previous research investigating the agreement between these instruments, practitioners may question if they can be used interchangeably. METHODS: 80 participants underwent near vision testing with the Mallett unit and iPad fixation disparity test. Data were analysed in four ways to investigate the agreement of the two instruments. RESULTS: Many participants reported no fixation disparity (horizontally 46.25%, vertically 82.5%), or non-significant aligning prism (horizontally 70%, vertically 97.5%), on both instruments. The iPad revealed a larger range of aligning prism results horizontally, 6Δ base out to 15Δ base in; the Mallett unit produced a larger range of results vertically, 1Δ base up to 3.5Δ base down. More participants required a significant aligning prism on the Mallett unit horizontally and vertically. Wilcoxon signed rank analysis found that the difference in aligning prism was not statistically significant (p=0.357 horizontally, p=0.236 vertically), but 95% limits of agreement revealed clinically significant differences between the instruments. CONCLUSION: Although the measured differences between the instruments are not significant in a Wilcoxon analysis, a Bland & Altman approach shows them to be in some cases clinically unacceptable, therefore the instruments should not be used interchangeably. Previous research indicates that the Mallett unit performs reasonably well at detecting symptomatic individuals and determining a prismatic correction that is likely to be helpful. Further research is required to determine the performance of the iPad test in these functions and to assess the reproducibility of both instruments.

The relationship between unwarranted variation in optometric referrals and time since qualification.

PURPOSE: To investigate variation in optometric referral decision-making and the influence of experience and continuing education and training (CET). METHODS: To gain insight into unwarranted variation in referral activity in the United Kingdom (UK): (1) triage data were audited to investigate source of referral, provisional diagnosis, and outcome; (2) an online system was developed to present two sets of 10 vignettes, designed to avoid prompting answers. Participating optometrists completed 10 pre-CET vignettes, recording their tests and management decisions. The main group of participants chose whatever CET they wished over a 6-month period and then completed another 10 post-CET vignettes. A second group of newly-qualified optometrists completed the vignettes before and after a CET course intervention, followed by a third group of pre-registered optometrists with an intervention of 6-months experience of their pre-registration year. RESULTS: The audit identified 1951 optometric referrals and 158 optometrists (211 referrals were from general medical practitioners), with 122 of the 158 optometrists making fewer than ten referrals. Two newly-qualified optometrists generated 12.5% of the total referrals in the audit (N = 2162). Many suspect glaucoma referrals were based on a single suspect measurement resulting in a high discharge rate after community review, as did referrals for certain fundus-related appearances for which no treatment was indicated. The intervention of gaining CET points appeared to have no significant impact (p = 0.37) on referral decision-making, although this part of the study was underpowered. Self-selection bias was confirmed in the main group. When the main group and newly-qualified practitioners were compared, the number of referrals was negatively associated with time since qualification (p = 0.005). When all 20 referral decisions were compared, all optometrists referring more than 10 vignette patients came from a group of newly-qualified practitioners up to 2 years post-qualification. Pre-registered optometrists generally referred more appropriately than newly-qualified. Upon qualification, there was a significant increase in the number of sight tests undertaken per day (p = <0.0005). CONCLUSIONS: Gaining CET points alone is unlikely to significantly improve referral decision-making. Mentoring and targeted CET for the newly-qualified up to 2 years post-qualification should be considered. Ophthalmology replies to the referring newly-qualified optometrist are vital for moderating future referrals and developing clinical confidence.

The impact of orthokeratology lens wear on binocular vision and accommodation: A short-term prospective study.

PURPOSE: To investigate the effects of short-term orthokeratology (OK) on accommodation and binocular visual function in young adults. METHODS: Twenty-four myopes (18 to 38 years) were fitted with OK lenses in both eyes. Best corrected distance visual acuity (VA), subjective and objective refractions, corneal topography and a series of binocular vision tests were measured at baseline (BL) before lens wear and then repeated after 28 nights of OK. Data from 15 subjects who demonstrated successful OK lens fit are reported. RESULTS: Corneal flattening and hyperopic shifts in spherical equivalent refractive error (all p < 0.001) after 28 nights of OK indicated myopic correction. Improvement in best corrected distance VA was measured after OK (right eye p = 0.021; left eye p = 0.014). Although there was no significant change in mean distance and near phorias and stereoacuity scores after OK compared to BL, there was a significant reduction in standard deviation (SD) and range of data (distance p = 0.01; near p = 0.02; stereoacuity p < 0.001). While there appeared to be an improvement in distance accommodative facility after OK, this failed to reach statistical significance (p = 0.053). Furthermore, there was no change in AC/A gradients with ±1 D and ±2 D lenses after OK compared to BL. CONCLUSIONS: Binocular vision remained unchanged after OK, although variability of phoria and stereoacuity measures reduced. This suggests that OK improves or maintains accommodative and binocular vision function in young adult myopes who achieve good vision with OK. Myopes with phorias outside normal ranges and/or poor distance accommodative facility may benefit most with OK, in binocular and accommodative function.

A Review of Depth of Focus in Measurement of the Amplitude of Accommodation.

The aim of this review is to investigate the role of depth of focus (DoF) as a potential confounding variable in the measurement of the amplitude of accommodation (AoA). The role of DoF in human vision is briefly summarised, and it is noted that the prevalent method of measuring AoA is the push-up method. Factors influencing the effect of DoF on the push-up and other methods of measuring AoA are reviewed in detail. DoF is shown to add substantial measurement error in the routine assessment of accommodation when the AoA is measured by methods involving subjective judgement of an object's clarity. Reliable compensation for this source of error is not realistically possible because of the complexity of the aetiology of DoF, and its inter-individual and intra-individual variation. The method of measurement also influences the extent of the error. It is concluded that methods of measurement of AoA that exclude DoF should be preferred.