Gut Microbiota Profiles in Myopes and Nonmyopes.

Purpose: To identify compositional differences in the gut microbiome of nonmyopes (NM) and myopes using 16S ribosomal RNA sequencing and to investigate whether the microbiome may contribute to the onset or progression of the condition. Methods: Faecal samples were collected from 52 adult participants, of whom 23 were NM, 8 were progressive myopes (PM), and 21 were stable myopes (SM). The composition of the gut microbiota in each group was analysed using 16S ribosomal RNA gene sequencing. Results: There were no significant differences in alpha and beta diversity between the three groups (NM, PM, and SM). However, the distributions of Bifidobacterium, Bacteroides, Megamonas, Faecalibacterium, Coprococcus, Dorea, Roseburia, and Blautia were significantly higher in the myopes (SM and PM combined) when compared with emmetropes. The myopes exhibited significantly greater abundance of bacteria that are linked to the regulation of dopaminergic signalling, such as Clostridium, Ruminococcus, Bifidobacterium, and Bacteroides. Individuals with stable myopia were found to have a significantly higher proportion of Prevotella copri than those with progressive myopia. Bifidobacterium adolescentis, a gamma-aminobutyric acid (GABA)-producing bacterium, was significantly higher in all myopes than in NM and, in the comparison between SM and PM, it is significantly higher in SM. B. uniformis and B. fragilis, both GABA-producing Bacteroides, were present in relatively high abundance in all myopes and in SM compared with PM, respectively. Conclusions: The presence of bacteria related to dopamine effect and GABA-producing bacteria in the gut microbiome of myopes may suggest a role of these microorganisms in the onset and progression of myopia.

Experiences of the clinical academic pathway: a qualitative study in Greater Manchester to improve the opportunities of minoritised clinical academics.

OBJECTIVES: The aim of this study was to explore the barriers and facilitators faced by clinical academics (CAs) in the Greater Manchester region, with particular attention to the experiences of minoritised groups. DESIGN: A qualitative study using semistructured interviews and focus groups was conducted. A reflexive thematic analysis was applied to identify key themes. SETTING: University of Manchester and National Health Service Trusts in the Greater Manchester region. PARTICIPANTS: The sample of this study was composed of 43 participants, including CAs, senior stakeholders, clinicians and medical and dental students. RESULTS: Six themes were identified. CAs face several barriers and facilitators, some of which-(1) funding insecurity and (2) high workload between the clinic and academia-are common to all the CAs. Other barriers, including (3) discrimination that translates into struggles with self-worth and feeling of not belonging, (4) being or being perceived as foreign and (5) unequal distribution of care duties, particularly affect people from minoritised groups. In contrast, (6) mentorship was commonly identified as one of the most important facilitators. CONCLUSIONS: Cultural and structural interventions are needed, such as introducing financial support for early career CAs and intercalating healthcare students to promote wider social and cultural change and increase the feelings of belonging and representation across the entire CA pipeline.

UK Optometrists' Professional Learning Needs Toward Engaging with Myopia Control Interventions.

Purpose: This study aimed to explore the support that UK optometrists feel they require to facilitate their engagement with myopia control intervention. Methods: A self-administered online survey was distributed via QualtricsXM to practising optometrists in the UK via email lists and newsletters of local optical committees, social media, and optometric networks. Questions focussed on learning styles, training needs and barriers to learning. Results: Fifty-five respondents completed the survey. Forty-eight respondents answered the question on where they get information about myopia control and learning style, 79.2% indicated that conferences offering Continuing Professional Development (CPD) material were their main source, and 20.8% preferred online learning as the preferred format of delivery. Optometrists would like to receive training in clinical assessments (78.9%), evaluating suitable interventions (76.3%), developing and implementing specific patient intervention plans (76.3%), carrying out chosen myopia control interventions (fitting/prescribing) (73.7%), and the use of pharmacological interventions (94.4%). Of the 40 respondents who answered professional development questions, 97 5% were most interested in finding, identifying and applying evidencebased practice (EBP), followed by clinical decision-making in myopia control (95.0%). When asked about barriers to learning in this field, 29.7% reported limited time to attend training as the greatest barrier. Conclusion: Optometrists felt they need training in various aspects of myopia management, from practical skills to assessing and fitting/prescribing appropriate myopia control interventions. They were also interested in learning more on EBP and clinical decision-making related to myopia control. To improve the uptake of myopia control among optometrists, various learning methods, especially online learning, and providing sufficient time for training are crucial.

Myopia management algorithm. Annexe to the article titled Update and guidance on management of myopia. European Society of Ophthalmology in cooperation with International Myopia Institute.

Myopia is becoming increasingly common in young generations all over the world, and it is predicted to become the most common cause of blindness and visual impairment in later life in the near future. Because myopia can cause serious complications and vision loss, it is critical to create and prescribe effective myopia treatment solutions that can help prevent or delay the onset and progression of myopia. The scientific understanding of myopia's causes, genetic background, environmental conditions, and various management techniques, including therapies to prevent or postpone its development and slow its progression, is rapidly expanding. However, some significant information gaps exist on this subject, making it difficult to develop an effective intervention plan. As with the creation of this present algorithm, a compromise is to work on best practices and reach consensus among a wide number of specialists. The quick rise in information regarding myopia management may be difficult for the busy eye care provider, but it necessitates a continuing need to evaluate new research and implement it into daily practice. To assist eye care providers in developing these strategies, an algorithm has been proposed that covers all aspects of myopia mitigation and management. The algorithm aims to provide practical assistance in choosing and developing an effective myopia management strategy tailored to the individual child. It incorporates the latest research findings and covers a wide range of modalities, from primary, secondary, and tertiary myopia prevention to interventions that reduce the progression of myopia.

Seasonal variations in anterior segment angle parameters in myopes and emmetropes.

CLINICAL RELEVANCE: Seasonal variations are known to occur in a range of ocular parameters and in conditions including refractive error and glaucoma. It is of clinical importance to know if seasonal changes also occur in anterior segment angle parameters, given that they can influence these conditions. BACKGROUND: The study aimed to examine the seasonal variations in anterior segment angle parameters in healthy young adults. METHODS: Twenty-three emmetropic participants with a mean age of 26.17 ± 4.43 years and 22 myopic participants with a mean age of 27.27 ± 4.47 years completed four seasons of data collection. Anterior segment angle parameters were measured using swept-source anterior segment optical coherence tomography. Intraocular pressure (IOP) and objective refraction were also measured. Repeated-measures analysis of variance was used to determine the effect of season and refractive error on the various ocular parameters. RESULTS: A significant main effect of season was found for the majority of anterior segment angle parameters, including the angle opening distance at 500 and 750 µm from the scleral spur (p = 0.02, p = 0.006, respectively), angle recess area at 500 and 750 µm from the scleral spur (both p = 0.002), and trabecular iris space area at 500 and 750 µm from the scleral (p = 0.02, p = 0.008, respectively). However, measures of anterior chamber depth and trabecular iris angle did not exhibit statistically significant seasonal variations (all p > 0.05). A significant main effect of season was also found for the changes in IOP (p = 0.004) and objective refraction (p < 0.001). There was no season by refractive group interaction for any anterior segment angle parameter or IOP (all p > 0.05). CONCLUSION: There is a small but significant seasonal changes in the anterior segment angle parameters, refractive error, and IOP in healthy young adult males, in which the anterior segment angle dimensions are narrower, the IOP is higher, and the refraction is more myopic during winter.

Multiple segment spectacle lenses for myopia control. Part 2: Impact on myopia progression.

PURPOSE: Initial studies have suggested that multiple segment (MS) spectacle lenses can reduce the progression rate of childhood myopia and axial eye growth. This paper aimed to compare the effectiveness of two different available designs of MS lens and to explore the nature of their control effect. METHOD: Published data from the only two clinical trials in which changes in mean spherical equivalent refraction (SER) and axial length (AL) for matched groups of myopic children wearing either MS or single-vision (SV) spectacle corrections, recorded over a period of at least 2 years, were further analysed and compared. Both trials involved Chinese children of similar ages and visual characteristics, but the trials were located in different cities. The two MS lenses examined were MiyoSmart or DIMS (Hoya) and Stellest (Essilor). RESULTS: Absolute changes in SER and AL differed over time during the two trials. However, if the results were expressed in terms of efficacy over successive 6-month periods, then the two MS lenses produced broadly similar results (initial efficacy for the control of myopia progression of about 60%-80%, declining over 2 years to about 35%-55%). Control appears to be absolute rather than proportional. DISCUSSION: Myopia control may be due to either the additional myopic defocus induced by the MS lenses (i.e., asymmetry of the through-focus image changes about the distance focus) or to the general reduction in image contrast that the lenslets create in the peripheral field. CONCLUSION: Multiple segment spectacle lenses offer a valuable new approach to the control of myopia progression in children. Further work is required to clarify their mechanism of action and to optimise their design parameters.

Multiple segment spectacle lenses for myopia control. Part 1: Optics.

PURPOSE: To understand and compare the optics of two multiple segment (MS) spectacle lenses (Hoya MiyoSmart and Essilor Stellest) designed to inhibit myopia progression in children. METHODS: The optics of the two designs are presented, together with geometrical optics-based calculations to understand the impact of the lenses on the optics of the eye. Lenses were evaluated with three techniques: surface images, Twyman-Green interferometry and focimetry. The carrier lens powers and the spatial distribution, powers and forms of the lenslets were measured. RESULTS: MS lenses as manufactured were found to match most of the design specifications provided by their manufacturers, although some apparent small discrepancies were found. The focimeter-measured power of the lenslets was approximately +3.50 D for the MiyoSmart and +4.00 D for the highly aspheric lenslets of the Stellest design. For both lens designs, image contrast would be expected to become modestly reduced in the focal planes of the distance-correcting carrier lenses. Images become much more degraded in the combined carrier-lenslet focal plane, due to the generation of multiple laterally displaced images formed by adjacent lenslets within the effective pupil. The exact effects observed depended on the effective pupil size and its location with respect to the lenslets, as well as the power and arrangement of the lenslets. CONCLUSION: Wearing either of these lenses will produce broadly similar effects on retinal imagery.

Associations between Accommodative Facility, Age, and Refractive Errors in Early, Older Adolescent Myopes and Emmetropes.

Background: Accommodative functions are known to differ between myopes and emmetropes. It is not known whether accommodative facility differs at near between younger adolescent and older adolescent myopes and emmetropes. Aim: To examine whether accommodative facility differs at near between younger and older adolescent myopes and emmetropes. Methods: 119 participants aged between 11-21 years were recruited. Refractive error was measured using cycloplegic retinoscopy. Near monocular accommodative facility was measured for 60 seconds, using a +2.00D/-2.00D handheld flipper and N6 print at 40 cm. Participants were classified into two age groups: (i) younger adolescents (range: 11-14 years) and (ii) older adolescents (range: 15-21 years). The criterion applied to define myopia was spherical equivalent refraction: ≥-0.50D) and spherical equivalent refraction: -0.25D to +0.75D) for emmetropia. Univariate Analysis of Variance was carried out to analyze the interaction of age groups and refractive groups on near accommodative facility. Results: Near monocular accommodative facility was significantly lower (p = 0.003) in younger adolescents (5.87 ± 3.72 cpm) compared to older adolescents (8.11 ± 4.11 cpm), indicating age as a significant main effect (F1,115 = 13.44; p = 0.0001). Younger adolescent emmetropes (4.77 ± 2.05 cpm, p = 0.005) and younger adolescent myopes (6.48 ± 4.12 cpm, p = 0.022) had significantly lower monocular near accommodative facility compared to older adolescent emmetropes (9.52 ± 3.27 cpm), but did not show any difference when compared to older adolescent myopes (p > 0.05). This indicates a significant association linking age and refractive error to near accommodative facility (F1,115 = 4.60; p = 0.03). Conclusion: Younger adolescent myopes and younger adolescent emmetropes had reduced monocular near accommodative facility than older adolescent emmetropes, but not when compared to older adolescent myopes.

Corneal Densitometry to Assess the Corneal Cystine Deposits in Patients With Cystinosis.

PURPOSE: The purpose of this study was to assess the suitability of corneal densitometry measurements obtained with Scheimpflug imaging in estimating the corneal changes caused by cystine deposits in the cornea in patients with cystinosis. METHODS: Scheimpflug imaging (Pentacam) was performed for 14 patients with cystinosis and 16 age-matched controls. Pentacam data were used for analysis of the corneal densitometry at different zones in the cornea for patients with cystinosis and controls. Densitometry measurements were compared with the corneal crystal scores obtained from the slitlamp images for patients with cystinosis. RESULTS: There was no statistically significant difference in keratometry measurements between the 2 groups ( P > 0.05). Corneal thickness was found to be significantly higher in the control group when compared with the cystinosis group ( P = 0.0004). The mean corneal densitometry was significantly higher in patients with cystinosis when compared with controls at most of the corneal layers and zones. The corneal densitometry readings for the right and left eyes showed moderate positive correlation with the corneal crystal score with a ceiling effect being reached at the maximum corneal crystal score of 3. CONCLUSIONS: Corneal densitometry obtained through Pentacam can be used as an objective estimate of the level of cystine crystals present in patients with cystinosis. The clinical estimate of corneal crystal score, although effective at low levels of crystal deposition, does not allow for accurate estimates of change when the level of crystal deposition is high leading to limited utility when assessing treatment effects. Hence, densitometry measurements can potentially be used to assess treatment efficacy of cystinosis treatments in clinical settings.

Corneal biomechanical properties following corneal cross-linking: Does age have an effect?

PURPOSE: To explore the effect of age on corneal biomechanical properties following corneal cross-linking (CXL). METHODS: A total of 12 pairs of human eye-banked corneas (24 corneas, from 14 females and 10 males) were used in the study. The mean donor age was 48.5 years (ranging from 26 to 71 years). Corneas were divided into three age groups: A (26-41 years), B (42-57 years) and C (58-71 years), with four pairs in each group. For each pair, the right corneas were cross-linked using accelerated CXL with UVA (10 mW/cm2) and riboflavin, while the left corneas served as controls and were not exposed to either UVA irradiation or riboflavin. The corneal elastic modulus of the anterior, mid and posterior corneal stroma was measured using nanoindentation. RESULTS: The difference in the corneal elastic modulus following CXL was significant in the anterior (p = 0.00002) and mid stroma (p = 0.001); however, the difference was not significant in the posterior stroma (p = 0.27) when compared to control corneas. The corneal elastic modulus of the anterior stroma increased by 178.44% in Group A, 119.7% in Group B and 50.73% in Group C compared to control corneas. For the mid stroma, the elastic modulus increased by 47.35% in Group A, 25% in Group B and 24.56% in Group C. No differences were observed in the posterior stroma between age groups. CONCLUSIONS: Corneal elasticity showed a greater response to CXL in the younger group compared to older groups. CXL treatment showed effectiveness in enhancing stromal strength, and the effect was concentrated in the anterior and mid stroma with minimal impact on the posterior stroma in all age groups.

Flitcroft's model of refractive development in childhood and the possible identification of children at risk of developing significant myopia.

PURPOSE: To better understand juvenile myopia in the context of overall refractive development during childhood and to suggest more informative ways of analysing relevant data, particularly in relation to early identification of those children who are likely to become markedly myopic and would therefore benefit from myopia control. METHODS: Examples of the frequency distributions of childhood mean spherical refractive errors (MSEs) at different ages, taken from previously-published longitudinal and cross-sectional studies, are analysed in terms of Flitcroft's model of a linear combination of two Gaussian distributions with different means and standard deviations. Flitcroft hypothesises that one, relatively-narrow, Gaussian (Mode 1) represents a "regulated" population which maintains normal emmetropisation and the other, broader, Gaussian (Mode 2) a "dysregulated" population. RESULTS: Analysis confirms that Flitcroft's model successfully describes the major features of the frequency distribution of MSEs in randomly-selected populations of children of the same age. The narrow "regulated" Gaussian typically changes only slightly between the ages of about 6 and 15, whereas the mean of the broader "dysregulated" Gaussian changes with age more rapidly in the myopic direction and its standard deviation increases. These effects vary with the ethnicity, environment and other characteristics of the population involved. At all ages there is considerable overlap between the two Gaussians. This limits the utility of simple refractive cut-off values to identify those children likely to show marked myopic progression. CONCLUSIONS: Analysing the frequency distributions for individual MSEs in terms of bi-Gaussian models can provide useful insights into childhood refractive change. A wider exploration of the methodology and its extension to include individual progression rates is warranted, using a range of populations of children exposed to different ethnic, environmental and other factors.

IMI Accommodation and Binocular Vision in Myopia Development and Progression.

The role of accommodation in myopia development and progression has been debated for decades. More recently, the understanding of the mechanisms involved in accommodation and the consequent alterations in ocular parameters has expanded. This International Myopia Institute white paper reviews the variations in ocular parameters that occur with accommodation and the mechanisms involved in accommodation and myopia development and progression. Convergence is synergistically linked with accommodation and the impact of this on myopia has also been critiqued. Specific topics reviewed included accommodation and myopia, role of spatial frequency, and contrast of the task of objects in the near environment, color cues to accommodation, lag of accommodation, accommodative-convergence ratio, and near phoria status. Aspects of retinal blur from the lag of accommodation, the impact of spatial frequency at near and a short working distance may all be implicated in myopia development and progression. The response of the ciliary body and its links with changes in the choroid remain to be explored. Further research is critical to understanding the factors underlying accommodative and binocular mechanisms for myopia development and its progression and to guide recommendations for targeted interventions to slow myopia progression.

Update and guidance on management of myopia. European Society of Ophthalmology in cooperation with International Myopia Institute.

The prevalence of myopia is increasing extensively worldwide. The number of people with myopia in 2020 is predicted to be 2.6 billion globally, which is expected to rise up to 4.9 billion by 2050, unless preventive actions and interventions are taken. The number of individuals with high myopia is also increasing substantially and pathological myopia is predicted to become the most common cause of irreversible vision impairment and blindness worldwide and also in Europe. These prevalence estimates indicate the importance of reducing the burden of myopia by means of myopia control interventions to prevent myopia onset and to slow down myopia progression. Due to the urgency of the situation, the European Society of Ophthalmology decided to publish this update of the current information and guidance on management of myopia. The pathogenesis and genetics of myopia are also summarized and epidemiology, risk factors, preventive and treatment options are discussed in details.

Effect of Defocus Incorporated Multiple Segments Spectacle Lens Wear on Visual Function in Myopic Chinese Children.

Purpose: To compare visual function of myopic children who had worn either defocus incorporated multiple segment (DIMS) spectacle lenses or single vision (SV) spectacle lenses over two years. Methods: We included 160 Chinese myopic (-1 diopter [D] to -5 D) children aged 8 to 13 years in a randomized clinical trial; they wore either DIMS lenses (DIMS; n = 79) or regular SV spectacles lenses (n = 81) full time for 2 years. Visual function, including high-contrast visual acuity (VA) and low-contrast VA at distance and near, binocular functions, and accommodation, before, during, and after 2 years of spectacle wear were assessed when both groups wore SV corrections. Changes of visual function between the two groups and within groups were compared. Results: There were no statistically significant differences in the 2-year visual function changes between DIMS and SV groups (repeated measures analysis of variance with group as factor; P > 0.05). Statistically significant improvement in the best-corrected distance high-contrast VA (P < 0.001) and stereoacuity score (P < 0.001) were found after DIMS lens wear over 2 years. Similar findings were observed after SV spectacle lens wear. For both the DIMS and SV groups, there were statistically significant decreases in accommodative lag, monocular and binocular amplitude of accommodation after two years (P < 0.01), but not in the changes in distance low-contrast VA, near high-contrast VA, near low-contrast VA, or phoria. Conclusions: Although changes in some visual function were shown during 2 years of DIMS lens wear, similar changes were found with SV lens wear. Wear of DIMS spectacle lenses for 2 years does not adversely affect major visual function when children return to SV corrections. Translational Relevance: DIMS spectacle lenses did not cause any adverse effects on visual function.

Next-Generation Sequencing of the Ocular Surface Microbiome: In Health, Contact Lens Wear, Diabetes, Trachoma, and Dry Eye.

OBJECTIVES: To assess publications examining the occurrence, composition, and clinical significance of a microbiome at the ocular surface. METHODS: MEDLINE, EMBASE, and Google Scholar were searched. Reference lists of included articles were also searched for relevant citations. All publications up to June 1, 2019, were analyzed. RESULTS: Eleven articles and 1 abstract were included, analyzing 661 patients. Articles generally report bacteria to the genus level. The presence of DNA associated with diverse bacterial species was reported including pathogenic species, such as Pseudomonas and Neisseria. Bacterial DNA that makes up the microbiome, such as Acinetobacter, Actinomyces, Aquabacterium, Bradyrhizobium, Corynebacterium, Sphingomonas, Staphylococcus, and Streptococcus, in other parts of the body was found. The putative ocular microbiome is consistent between right and left eyes and is affected by contact lens use (higher Pseudomonas levels) and blepharitis (higher Staphylococcus levels). CONCLUSIONS: There is a significant likelihood that there is at least a transitory ocular surface microbiome, with Acinetobacter, Corynebacterium, Propionibacterium, Staphylococcus, and Streptococcus detected in at least 7 of 11 studies. However, further investigation attempting to control for environmental and methodological contaminants (Aquabacterium and Bradyrhizobium are commonly identified as contaminants in DNA extraction kits) is required. Bacteria, such as Propionibacterium, Staphylococcus, and Streptococcus, capable of causing sight-threatening infections may reside on a healthy ocular surface. With greater understanding, we can establish whether elements of the ocular surface microbiome are harmful or protective (despite their small quantities); furthermore, new therapeutic agents can be identified to treat and prevent ocular surface infection and inflammation.

Factors Influencing Pseudo-Accommodation-The Difference between Subjectively Reported Range of Clear Focus and Objectively Measured Accommodation Range.

The key determinants of the range of clear focus in pre-presbyopes and their relative contributions to the difference between subjective range of focus and objective accommodation assessments have not been previously quantified. Fifty participants (aged 33.0 ± 6.4 years) underwent simultaneous monocular subjective (visual acuity measured with an electronic test-chart) and objective (dynamic accommodation measured with an Aston open-field aberrometer) defocus curve testing for lenses between +2.00 to -10.00 DS in +0.50 DS steps in a randomized order. Pupil diameter and ocular aberrations (converted to visual metrics normalized for pupil size) at each level of blur were measured. The difference between objective range over which the power of the crystalline lens changes and the subjective range of clear focus was quantified and the results modelled using pupil size, refractive error, tolerance to blur, and ocular aberrations. The subjective range of clear focus was principally accounted for by age (46.4%) and pupil size (19.3%). The objectively assessed accommodative range was also principally accounted for by age (27.6%) and pupil size (15.4%). Over one-quarter (26.0%) of the difference between objective accommodation and subjective range of clear focus was accounted for by age (14.0%) and spherical aberration at maximum accommodation (12.0%). There was no significant change in the objective accommodative response (F = 1.426, p = 0.229) or pupil size (F = 0.799, p = 0.554) of participants for levels of defocus above their amplitude of accommodation. Pre-presbyopes benefit from an increased subjective range of clear vision beyond their objective accommodation due in part to neural factors, resulting in a measured depth-of-focus of, on average, 1.0 D.

Accommodation and age-dependent eye model based on in vivo measurements.

PURPOSE: To develop a flexible model of the average eye that incorporates changes with age and accommodation in all optical parameters, including entrance pupil diameter, under photopic, natural, environmental conditions. METHODS: We collated retrospective in vivo measurements of all optical parameters, including entrance pupil diameter. Ray-tracing was used to calculate the wavefront aberrations of the eye model as a function of age, stimulus vergence and pupil diameter. These aberrations were used to calculate objective refraction using paraxial curvature matching. This was also done for several stimulus positions to calculate the accommodation response/stimulus curve. RESULTS: The model predicts a hyperopic change in distance refraction as the eye ages (+0.22D every 10 years) between 20 and 65 years. The slope of the accommodation response/stimulus curve was 0.72 for a 25 years-old subject, with little change between 20 and 45 years. A trend to a more negative value of primary spherical aberration as the eye accommodates is predicted for all ages (20-50 years). When accommodation is relaxed, a slight increase in primary spherical aberration (0.008µm every 10 years) between 20 and 65 years is predicted, for an age-dependent entrance pupil diameter ranging between 3.58mm (20 years) and 3.05mm (65 years). Results match reasonably well with studies performed in real eyes, except that spherical aberration is systematically slightly negative as compared with the practical data. CONCLUSIONS: The proposed eye model is able to predict changes in objective refraction and accommodation response. It has the potential to be a useful design and testing tool for devices (e.g. intraocular lenses or contact lenses) designed to correct the eye's optical errors.

Impact of higher-order aberrations on depth-of-field.

It is well known that depth-of-focus (DOF) is influenced by optical factors (such as pupil size and monochromatic aberrations). However, neural factors such as blur sensitivity and defocus adaptation may play an important role on the extent of DOF. A series of experiments were conducted to study if optical or neural factors are most pertinent in explaining the variability of DOF across subjects. An adaptive optics system with a black and white target, a 3.8-mm artificial pupil, and a subjective criterion (based on objectionable blur) were used to measure depth of field ([DOFi]; DOF computed in the object space) in 11 participants, after at least 6 min of adaptation. This was done under three conditions: (a) with their own higher order aberrations (HOA); (b) after correction of their monochromatic HOA; and (c) after altering the HOA pattern for some participants to reflect the HOA pattern measured for a different participant. Natural DOFi and DOFi after HOA correction were positively correlated (R2 = 0.461), but a significant decrease in DOFi (21% on average) was found after HOA correction (p = 0.042). Effect of HOA on the intersubject variability of DOFi was 3.9 times smaller than the effect of the image neural processing. This study shows that DOFi depends on both optical and neural factors, but the latter seems to play a more important role than the former.