Epidemiology of myopia in a United Kingdom urban child population

The Aston Eye Study (AES) was instigated in October 2005 to determine the distribution of refractive error and associated ocular biometry in a sample of UK urban school children. The AES is the first study to compare outcome measures separately in White, South Asian and Black children. Children were selected from two age groups (Year 2 children aged 6/7 years, Year8 children aged 12/13 years of age) using random cluster sampling of schools in Birmingham, West Midlands UK. To date, the AES has examined 598 children (302 Year 2,296 Year 8). Using open-field cycloplegic autorefraction, the overall prevalence of myopia (=-0.50D SER in either eye) determined was 19.6%, with a higher prevalence in older (29.4%) compared to younger (9.9%) children (p<0.001). Using multiple logistic regression models, the risk of myopia was higher in Year 8 South Asian compared to White children and higher in children attending grammar schools relative to comprehensive schools. In addition, the prevalence of uncorrected ametropia was found to be high (Year 8: 12.84%, Year 2: 15.23%), which will be of concern to bodies responsible for the implementation of school vision screening strategies. Biometric data using non-contact partial coherence interferometry revealed a contributory effect of axial length (AL) and central corneal radius (CR) on myopic refraction, resulting in a strong coefficient of determination of the AL/CR ratio on refractive error. Ocular biometric measures did not vary significantly as a function of ethnicity, suggesting a greater miscorrelation of components in susceptible ethnic groups to account for their higher myopia prevalence. Corneal radius was found to be steeper in myopes in both age groups, but was found to flatten with increasing axial length. Due to the inextricable link between myopia and axial elongation, the paradoxical finding of the cornea demands further longitudinal investigation, particularly in relation to myopia onset. Questionnaire analysis revealed a history of myopia in parents and siblings to be significantly associated with myopia in Year 8 children, with a dose-dependent rise in the odds ratio of myopia evident with increasing number of myopic parents. By classifying socioeconomic status (SES) using Index of Multiple Deprivation values, it was found that Year 8 children from moderately deprived backgrounds were more at risk of myopia compared with children located at both extremities of the deprivation spectrum. However, the main effect of SES weakened following multivariate analysis, with South Asian ethnicity and grammar schooling remaining associated with Year 8 myopia after adjustment.

Contact lenses and sport

Contact lenses seem to be the ideal method of vision correction for ametropic people who participate in sporting activities. This thesis sets out to evaluate the viewpoint of the optometric professional and that of the patient on the use of contact lenses in sport and to establish if education is needed within this area. It also aims to provide some scientific evidence on the effect of exercise on the physiology of the cornea with and without contact lenses. Silicone hydrogel contact lenses have previously been suggested to impede heat dissipation from the cornea compared to mid water hydrogels. This was further demonstrated with exercise. The physiological integrity of the cornea is dependant on the amount of oxygen available to its surfaces. Contact lenses can disrupt the diffusion of oxygen to the cornea. Previous methods of measuring the oxygen consumption of the cornea have been limited by their invasive nature and assessment of only a small surface area of the cornea. They are not suitable to measure corneal oxygen consumption during exercise with and without contact lenses. A new method needed to be established. This was achieved by designing a novel method by the use of an oxygen sensor inside an airtight goggle using dynamic quenching of luminescence method. This established a non-contact way of measuring the effect oxygen uptake with and without contact lenses in vivo, allowing the contact lens to be undisturbed in their natural environment. The new method differentiated between the closed-eye and the open-eye condition with a good within-visit repeatability. It also illustrated that the cornea utilises oxygen at a faster rate during controlled aerobic exercise at moderate intensity. New contact lenses are available specifically for sport, these claim to reduce glare and increase contrast for daylight outdoor sports. However, visual benefits of these types of contact lenses cannot be measured easily in an indoor clinical environment, such as the optometric practice. To demonstrate any potential benefits of these lenses emulation of them should be conducted outdoors.

Accommodation and intraocular pressure

The relationship between accommodation and intraocular pressure (lOP) has not been addressed as a research question for over 20 years, when measurement of both of these parameters was less advanced than today. Hence the central aim of this thesis was to evaluate the effects of accommodation on lOP. The instrument of choice throughout this thesis was the Pulsair EasyEye non-contact tonometer (NCT) due principally to its slim-line design which allowed the measurement of lOP in one eye and simultaneous stimulation of accommodation in the other eye. A second reason for using the Pulsair EasyEye NCT was that through collaboration with the manufacturers (Keeler, UK) the instrument's operational technology was made accessible. Hence, the principle components underpinning non-contact lOP measures of 0.1mmHg resolution (an order of magnitude greater than other methods) were made available. The relationship between the pressure-output and corneal response has been termed the pressure-response relationship, aspects of which have been shown to be related to ocular biometric parameters. Further, analysis of the components of the pressure-response relationship together with high-speed photography of the cornea during tonometry has enhanced our understanding of the derivation of an lOP measure with the Pulsair EasyEye NCT. The NCT samples the corneal response to the pressure pulse over a 19 ms cycle photoelectronically, but computes the subject's lOP using the data collected in the first 2.34 ms. The relatively instantaneous nature of the lOP measurement renders the measures susceptible to variations in the steady-state lOP caused by the respiratory and cardiac cycles. As such, the variance associated with these cycles was minimised by synchronising the lOP measures with the cardiac trace and maintaining a constant pace respiratory cycle at 15 breathes/minute. It is apparent that synchronising the lOP measures with the peak, middle or trough of the cardiac trace significantly reduced the spread of consecutive measures. Of the 3 locations investigated, synchronisation with the middle location demonstrated the least variance (coeflicient of variation = 9.1%) and a strong correlation (r = 0.90, p = <0.001) with lOP values obtained with Goldmann contact tonometry (n = 50). Accordingly lOP measures synchronised with the middle location of the cardiac cycle were taken in the RE while the LE fixated low (L; zero D), intermediate (I; 1.50 D) and high (H; 4 D) accommodation targets, Quasi-continuous measures of accommodation responses were obtained during the lOP measurement period using the portable infrared Grand Seiko FR-5000 autorefractor. The lOP reduced between L and I accommodative levels by approximately 0.61 mmHg (p <0.00 I). No significant reduction in IOP between L and H accommodation levels was elicited (p = 0.65) (n = 40). The relationship between accommodation and lOP was characterised by substantial inter-subject variations. Myopes demonstrated a tendency to show a reduction in IOP with accommodation which was significant only with I accommodation levels when measured with the NCT (r = 0.50, p = 0.01). However, the relationship between myopia and lOP change with accommodation reached significance for both I (r = 0.61, p= 0.003) and H (r = 0.531, p= 0.0 1) accommodation levels when measured with the Ocular blood Flow Analyser (OBFA). Investigation of the effects of accommodation on the parameters measured by the OBFA demonstrated that with H accommodation levels the pulse amplitude (PA) and pulse rate (PR) responses differed between myopes and emmetropes (PA: p = 0.03; PR: p = 0.004). As thc axial length increased there was a tendency for the pulsatile ocular blood flow (POBF) to reduce with accommodation, which was significant only with H accommodation levels (r = 0.38, p = 0.02). It is proposed that emmetropes arc able to regulate the POBF responses to changes in ocular perfusion pressure caused by changes in lOP with I (r = 0.77, p <0.001) and H (r = 0.73, p = 0.001) accommodation levels. However, thc relationship between lOP and POBF changes in the myopes was not correlated for both I (r = 0.33, p = 0.20) and H (r = 0.05, p = 0.85) accommodation levels. The thesis presents new data on the relationships between accommodation, lOP and parameters of the OBFA,: and provides evidence for possible lOP and choroidal blood flow regulatory mechanisms. Further the data highlight possible deficits in the vascular regulation of the myopic eye during accommodation, which may play a putative role in the aetiology of myopia development.

Ocular changes and other factors relating to two forms of contact lenses:a comparative study

The work utilising a new material for contact lenses has fallen into three parts: Physioloeical considerations: Since the cornea is devoid of blood vessels, its oxygen is derived from the atmosphere. Early hydrophilic gel contact lenses interrupted the flow of oxygen and corneal insult resulted. Three techniques of fenestration were tried to overcome this problem. High speed drilling with 0.1 mm diameter twist drills. was found to be mechanically successful, but under clinical conditions mucous blockage of the fenestrations occurred. An investigation was made into the amount of oxygen arriving at the corneal interface; related to gel lens thickness. The results indicated an improvement in corneal oxygen as lens thickness was reduced. The mechanism is thought to be a form of mechanical pump. A series of clinical studies con:firmed the experimental work; the use of thin lenses removing the symptoms of corneal hypoxia. Design: The parameters of lens back curvature. lens thickness and lens diameter have been isolated and related to three criteria of vision (a) Visual acuity. (b) Visual stability and (c) Induced astigmatism. From the results achieved a revised and basically successful design of lens has been developed. Comparative study: The developed form of lens was compared with traditional lenses in a controlled survey. Twelve factors were assessed over a twenty week period of wear using a total of eighty four patients. The results of this study indicate that whilst the expected changes were noted with the traditional lens wearers, gel lens wearers showed no discernible change in any of the factors measured. ldth the exception of' one parameter. In addition to a description of' the completed l'iork. further investigations are ·sug~ested l'lhich. it is hoped. l'iould further improve the optical performance of gel lenses.

Role of contact lenses in relieving ocular allergy

Purpose: To examine the potential barrier and lubricating effects of modern daily disposable contact lenses (DD) against airborne antigens. Methods: Ten patients with skin prick and ocular conjunctival provocation confirmed allergic sensitivity to grass pollen were recruited (average age 27.4±7.7 years). Each had their ocular symptoms (on a 0 none to 5 extreme scale) and appearance of bulbar and limbal conjunctival redness, palpebral conjunctival redness and roughness, and corneal and conjunctival fluorescein staining (CCLRU scale) graded before and five minutes after exposure to 400 grains grass pollen/m3 for 2 minutes in a purpose-designed exposure chamber to simulate the conditions of a ‘very high’ pollen-count day. This was repeated on three occasions separated by >72 hours wearing etafilcon A (sDD), nelfilcon A with enhanced lubricating agents (ELDD) and no contact lenses in random order out of the pollen season. Each sign and symptom was compared to baseline for each condition. The duration of the symptoms was also recorded. www.clinicaltrials.gov NCT01125540 Results: Only symptoms of burning and stinging were significantly reduced in severity by ELDD (Chi-Sq=7.6, p=0.02), but overall symptoms were significantly reduced in duration (F=3.60, p=0.05). Bulbar hyperaemia, corneal and conjunctival staining, and palpebral conjunctival roughness were significantly reduced by DD wear (p<0.01), with limbal and palpebral conjunctival redness further reduced in ELDD (p<0.05). Conclusion: Daily disposable contact lenses offer a barrier to airborne antigen which is enhanced by modern lenses with enhanced lubricating agents.

Rotational and centration stability of an aspheric intraocular lens with a simulated toric design

Purpose: To assess the stability of the Akreos AO intraocular lens (IOL) platform with a simulated toric design using objective image analysis. Setting: Six hospital eye clinics across Europe. Methods: After implantation in 1 eye of patients, IOLs with orientation marks were imaged at 1 to 2 days, 7 to 14 days, 30 to 60 days, and 120 to 180 days. The axis of rotation and IOL centration were objectively assessed using validated image analysis. Results: The study enrolled 107 patients with a mean age of 69.9 years ± 7.7 (SD). The image quality was sufficient for IOL rotation analysis in 91% of eyes. The mean rotation between the first day postoperatively and 120 to 180 days was 1.93 ± 2.33 degrees, with 96% of IOLs rotating fewer than 5 degrees and 99% rotating fewer than 10 degrees. There was no significant rotation between visits and no clear bias in the direction of rotation. In 71% of eyes, the dilation and image quality was sufficient for image analysis of centration. The mean change in centration between 1 day and 120 to 180 days was 0.21 ± 0.11 mm, with all IOLs decentering less than 0.5 mm. There was no significant decentration between visits and no clear bias in the direction of the decentration. Conclusion: Objective analysis of digital retroillumination images taken at different postoperative periods shows the aspheric IOL platform was stable in the eye and is therefore suitable for the application of a toric surface to correct corneal astigmatism.

Theoretical and empirical evaluation of phakic and pseudophakic accomodation

The binding theme of this thesis is the examination of both phakic and pseudophakic accommodation by means of theoretical modelling and the application of a new biometric measuring technique. Anterior Segment Optical Coherence Tomography (AS-OCT) was used to assess phakic accommodative changes in 30 young subjects (19.4 2.0 years; range, 18 to 25 years). A new method of assessing curvature change with this technique was employed with limited success. Changes in axial accommodative spacing, however, proved to be very similar to those of the Scheimpflug-based data. A unique biphasic trend in the position of the posterior crystalline lens surface during accommodation was discovered, which has not been alluded to in the literature. All axial changes with accommodation were statistically significant (p < 0.01) with the exception of corneal thickness (p = 0.81). A two-year follow-up study was undertaken for a cohort of subjects previously implanted with a new accommodating intraocular lens (AIOL) (Lenstec Tetraflex KH3500). All measures of best corrected distance visual acuity (BCDVA; +0.04 0.24 logMAR), distance corrected near visual acuity (DCNVA; +0.61 0.17 logMAR) and contrast sensitivity (+1.35 0.21 log units) were good. The subjective accommodation response quantified with the push-up technique (1.53 0.64 D) and defocus curves (0.77 0.29 D) was greater than the objective stimulus response (0.21 0.19 D). AS-OCT measures with accommodation stimulus revealed a small mean posterior movement of the AIOLs (0.02 0.03 mm for a 4.0 D stimulus); this is contrary to proposed mechanism of the anterior focus-shift principle.

Accuracy of Goldmann, ocular response analyser, Pascal and TonoPen XL tonometry in keratoconic and normal eyes

Aim: The aim of this study was to evaluate the practicality and accuracy of tonometers used in routine clinical practice for established keratoconus (KC). Methods: This was a prospective study of 118 normal and 76 keratoconic eyes where intraocular pressure (IOP) was measured in random order using the Goldman applanation tonometer (GAT), Pascal dynamic contour tonometer (DCT), Reichert ocular response analyser (ORA) and TonoPen XL tonometer. Corneal hysteresis (CH) and corneal resistance factor (CRF), as calculated by the ORA, were recorded. Central corneal thickness (CCT) was measured using an ultrasound pachymeter. Results: The difference in IOP values between instruments was highly significant in both study groups (p<0.001). All other IOP measures were significantly higher than those for GAT, except for the Goldmann-correlated IOP (average of the two applanation pressure points) (IOPg) as measured by ORA in the control group and the CH-corrected IOP (corneal-compensated IOP value) (IOPcc) measures in the KC group. CCT, CH and CRF were significantly less in the KC group (p<0.001). Apart from the DCT, all techniques tended to measure IOP higher in eyes with thicker corneas. Conclusion: The DCT and the ORA are currently the most appropriate tonometers to use in KC for the measurement of IOPcc. Corneal factors such as CH and CRT may be of more importance than CCT in causing inaccuracies in applanation tonometry techniques.

Towards a synthetic osteo-odonto-keratoprosthesis

Osteo-odonto-keratoprostheses (OOKP) is a unique form of keratoprosthesis involving surgical removal of a tooth root and surrounding bone from the patient which are then used to construct an osteo-odonto lamina into which an optical cylinder is cemented. The OOKP procedure is successful and capable of withstanding the very hostile ocular environments found in severe Stevens–Johnson syndrome, pemphigoid, chemical burns, trachoma and multiple corneal graft failure. The existing procedure is complex and time consuming in terms of operative time, and additionally involves sacrifice of the oral structures. This paper discusses the rational search for a “synthetic” analogue of the dental lamina, capable of mimicking those features of the natural system that are responsible for the success of OOKP. In this study the degradation of selected commercial and natural bioceramics was tested in vitro using a purpose-designed resorption assay. Degradation rate was compared with tooth and bone, which are currently used in OOKP lamina. At normal physiological pH the degradation of bioceramics was equivalent to tooth and bone; however, at pH 6.5–5.0, associated with infectious and inflamed tissues, the bioceramics degrade more rapidly. At lower pH the degradation rate decreased in the following order: calcium carbonate corals > biphasic calcium phosphates > hydroxyapatite. Porosity did not significantly influence these degradation rates. Such degradation is likely to compromise the stability and viability of the synthetic OOKP. Consequently more chemically stable materials are required that are optimized for the surrounding ocular environment.

Myopia control with orthokeratology contact lenses in Spain (MCOS):refractive and biometric changes

PURPOSE. To compare axial length growth between white children with myopia wearing orthokeratology contact lenses (OK) and distance single-vision spectacles (SV) over a 2-year period. METHODS. Subjects 6 to 12 years of age with myopia -0.75 to -4.00 diopters of sphere (DS) and astigmatism ≤1.00 diopters of cylinder (DC) were prospectively allocated OK or SV correction. Measurements of axial length (Zeiss IOLMaster), corneal topography, and cycloplegic refraction were taken at 6-month intervals. RESULTS. Thirty-one children were fitted with OK and 30 with SV. Following 24 months, axial length increased significantly over time for both the OK group (0.47 mm) and SV group (0.69 mm; P < 0.001), with a significant interaction between time and group (P = 0.05) reflecting a greater increase in the SV group. Significant differences in refraction were found over time, between groups and for the interaction between time and group for spherical (all P < 0.001) but not cylindrical components of refraction (all P > 0.05). Significantly greater corneal flattening was evident in the OK group for the flatter and steeper corneal powers and for corneal shape factor (all P ≤0.05). CONCLUSIONS. Orthokeratology contact lens wear reduces axial elongation in comparison to distance single-vision spectacles in children. © 2012 The Association for Research in Vision and Ophthalmology, Inc.

Proteoglycan analogues for ophthalmic and orthopaedic applications

The successful development of biomaterials is increasingly influenced by biomimesis essentially the use of biological structures as design templates. This approach has been used here in the design of injectable systems for the nucleus of the intervertebral disc, corneal inlays and intraocular lenses (IOLs). The strategy is based on the use of C-linked sulphonates to mimic the O-linked sulphate groups that are the hydration drivers in proteoglycans. The elastic modulus of the materials can be tailored for specific applications.

The effect of care solutions on the bulk and surface properties of soft contact lenses

Purpose: Soft contact lenses for continuous wear require the use of cleaning regimes which utilise hydrogen peroxide systems or multipurpose cleaning solutions (MPS). The compositions of MPS are becoming increasingly complex and often include disinfectants, cleaning agents, preservatives, wetting agents, demulcents, chelating and buffering agents. Recent research on solution–lens interactions has focused on specific ocular parameters such as corneal staining. However the effect of a solution on the lens, particularly silicone hydrogel lenses, itself has received less attention. The purpose of this work was to establish and understand the effects that care solutions have on selected bulk and surface material properties. Methods: Selected bulk and surface properties of each material (etafilcon A, vifilcon A, balafilcon A, senofilcon A, lotrafilcon A and lotrafilcon B, galyfilcon A) were measured after a 24 h soak in a variety of care solutions. Additionally the lenses were soaked for 24 h in hyperosmolar (680 mOsm L-1) and hyposmolar (170 mOsm L-1) PBS. A bulk property parameter the total diameter (TD) was measured using an Optimec contact lens analyser. The surface property related CoF of soaked lenses was measured on a nano-tribometer with conditions of load 30 mN, at a distance of 20 mm and speed 30 mm/min. Results: In terms of bulk properties, change is related to the EWC of the lens, the higher the EWC of the lens the greater the TD changes. Silicone hydrogel lenses have EWCs of <47% and little or no TD changes were observed; lotrafilcon A exhibited no change irrespective of the cleaning solution. Conventional contact lenses have higher EWCs (58% for etafilcon A and 55% for vifilcon A) and the TD was seen to change to a greater extent, for example the etafilcon A material in ReNu MPS had an increase to 14.45± 0.07 mm from the cited 14.2 mm. Other lenses increased or decreased in TD depending on the solution used. The osmolarity of the solution although important is not the only factor governing change in the TD, for example soaking senofilcon A in hyperosmolar PBS (680 mOsm L-1) for 24 h increased the TD of the lens (+0.25 ± 0.07 mm), however when the same lens type was soaked for 24 h in a MPS with a lower osmolarity there was a similar effect. Biotribology measurements demonstrated that some solution–lens combinations can reduce the CoF by 55%, when compared with biotribology with the native packing solution. An increase in the CoF was observed for other solution–lens combinations. Conclusions: There is a dramatic difference in bulk and surface performance of specific lens materials with particular care solutions. Individual components of the care solutions have effects on the bulk and surface properties of contact lenses. The affects are not as great with the silicone hydrogel as compared with conventional hydrogels.

Clinical outcomes after implantation of a new hydrophobic acrylic toric IOL during routine cataract surgery

PURPOSE: To assess the clinical outcomes after implantation of a new hydrophobic acrylic toric intraocular lens (IOL) to correct preexisting corneal astigmatism in patients having routine cataract surgery. SETTING: Four hospital eye clinics throughout Europe. DESIGN: Cohort study. METHODS: This study included eyes with at least 0.75 diopter (D) of preexisting corneal astigmatism having routine cataract surgery. Phacoemulsification was performed followed by insertion and alignment of a Tecnis toric IOL. Patients were examined 4 to 8 weeks postoperatively; uncorrected distance visual acuity (UDVA), corrected distance visual acuity, manifest refraction, and keratometry were measured. Individual patient satisfaction with uncorrected vision and the surgeon’s assessment of ease of handling and performance of the IOL were also documented. The cylinder axis of the toric IOL was determined by dilated slitlamp examination. RESULTS: The study enrolled 67 eyes of 60 patients. Four to 8 weeks postoperatively, the mean UDVA was 0.15 logMAR G 0.17 (SD) and the UDVA was 20/40 or better in 88% of eyes. The mean refractive cylinder decreased significantly postoperatively, from -1.91 +/- 1.07 D to -0.67 +/- 0.54 D. No significant change in keratometric cylinder was observed. The mean absolute IOL misalignment from the intended axis was 3.4 degrees (range 0 to 12 degrees). The good UDVA resulted in high levels of patient satisfaction. CONCLUSION: Implantation of the new toric IOL was an effective, safe, and predictable method to manage corneal astigmatism in patients having routine cataract surgery.

Clinical evaluation of the Oculus Keratograph

AIM: To determine the validity and reliability of the measurement of corneal curvature and non-invasive tear break-up time (NITBUT) measures using the Oculus Keratograph. METHOD: One hundred eyes of 100 patients had their corneal curvature assessed with the Keratograph and the Nidek ARKT TonorefII. NITBUT was then measured objectively with the Keratograph with Tear Film Scan software and subjectively with the Keeler Tearscope. The Keratograph measurements of corneal curvature and NITBUT were repeated to test reliability. The ocular sensitivity disease index questionnaire was completed to quantify ocular comfort. RESULTS: The Keratograph consistently measured significantly flatter corneal curvatures than the ARKT (MSE difference: +1.83±0.44D), but was repeatable (p>0.05). Keratograph NITBUT measurements were significantly lower than observation using the Tearscope (by 12.35±7.45s; pp < 0.001) and decreased on subsequent measurement (by -1.64 ± 6.03s; p < 0.01). The Keratograph measures the first time the tears break up anywhere on the cornea with 63% of subjects having NI-TBUT's <5s and a further 22% having readings between 5 and 10s. The Tearscope results were found to correlate better with the patients symptoms (r = -0.32) compared to the Keratograph (r = -0.19). Conclusions: The Keratograph requires a calibration off-set to be comparable to other keratometry devices. Its current software detects very early tear film changes, recording significantly lower NITBUT values than conventional subjective assessment. Adjustments to instrumentation software have the potential to enhance the value of Keratograph objective measures in clinical practice.

Design and validity of a miniaturized open-field aberrometer

PURPOSE: To validate a new miniaturised, open-field wavefront device which has been developed with the capacity to be attached to an ophthalmic surgical microscope or slit-lamp. SETTING: Solihull Hospital and Aston University, Birmingham, UK DESIGN: Comparative non-interventional study. METHODS: The dynamic range of the Aston Aberrometer was assessed using a calibrated model eye. The validity of the Aston Aberrometer was compared to a conventional desk mounted Shack-Hartmann aberrometer (Topcon KR1W) by measuring the refractive error and higher order aberrations of 75 dilated eyes with both instruments in random order. The Aston Aberrometer measurements were repeated five times to assess intra-session repeatability. Data was converted to vector form for analysis. RESULTS: The Aston Aberrometer had a large dynamic range of at least +21.0 D to -25.0 D. It gave similar measurements to a conventional aberrometer for mean spherical equivalent (mean difference ± 95% confidence interval: 0.02 ± 0.49D; correlation: r=0.995, p<0.001), astigmatic components (J0: 0.02 ± 0.15D; r=0.977, p<0.001; J45: 0.03 ± 0.28; r=0.666, p<0.001) and higher order aberrations RMS (0.02 ± 0.20D; r=0.620, p<0.001). Intraclass correlation coefficient assessments of intra-sessional repeatability for the Aston Aberrometer were excellent (spherical equivalent =1.000, p<0.001; astigmatic components J0 =0.998, p<0.001, J45=0.980, p<0.01; higher order aberrations RMS =0.961, p<0.001). CONCLUSIONS: The Aston Aberrometer gives valid and repeatable measures of refractive error and higher order aberrations over a large range. As it is able to measure continuously, it can provide direct feedback to surgeons during intraocular lens implantations and corneal surgery as to the optical status of the visual system.