Influence of presbyopic corrections on driving-related eye and head movements

Purpose: To investigate whether wearing different presbyopic vision corrections alters the pattern of eye and head movements when viewing and responding to driving-related traffic scenes. Methods: Participants included 20 presbyopes (mean age: 56.1 ± 5.7 years) who had no experience of wearing presbyopic vision corrections, apart from single vision (SV) reading spectacles. Each participant wore five different vision corrections: distance SV lenses, progressive addition spectacle lenses (PAL), bifocal spectacle lenses (BIF), monovision (MV) and multifocal contact lenses (MTF CL). For each visual condition, participants were required to view videotape recordings of traffic scenes, track a reference vehicle, and identify a series of peripherally presented targets. Digital numerical display panels were also included as near visual stimuli (simulating the visual displays of a vehicle speedometer and radio). Eye and head movements were measured, and the accuracy of target recognition was also recorded. Results: The path length of eye movements while viewing and responding to driving-related traffic scenes was significantly longer when wearing BIF and PAL than MV and MTF CL (both p ≤ 0.013). The path length of head movements was greater with SV, BIF, and PAL than MV and MTF CL (all p < 0.001). Target recognition and brake response times were not significantly affected by vision correction, whereas target recognition was less accurate when the near stimulus was located at eccentricities inferiorly and to the left, rather than directly below the primary position of gaze (p = 0.008), regardless of vision correction. Conclusions: Different presbyopic vision corrections alter eye and head movement patterns. The longer path length of eye and head movements and greater number of saccades associated with the spectacle presbyopic corrections may affect some aspects of driving performance.

'Homophobia' in the university classroom : law and justice students' conceptualizations of queer identity

Heteronormative discourses provide the most common lens through which sexuality is understood within university curricula. This means that sexuality is discussed in terms of categories of identity, with heterosexuality accorded primacy and all ‘others’ indeed ‘othered.’ This paper reports on research carried out by the authors in a core first year university justice class, in which students of law and/or justice were required to engage with, discuss, and reflect on discourses on sexuality. It uses a poststructural framework to identify how students understand non-heterosexualities and how they personally relate to queer identities, in the sense that it asks questions about gender and sexual identity, and the discourses surrounding them. It was found that strongly negative attitudes to non-heterosexualities are quite resistant to challenge, and that some students express being confronted with queerness as a deep-seated fear of being drawn into otherness against their will. The result was that, while many students were able to unpack their attitudes towards queerness and engage in critical reflection and re-evaluation of their attitudes, students with strongly negative views towards non-heterosexualities conversely refused to engage at all, typically perceiving even the engagement itself as a threat to their core heterosexual identity. However, the authors caution against relying on the idea that students are simply “homophobic” to explain this reluctance, as this term does not necessarily account for the complexity of the discourses that inform students’ reactions in this context. This “homophobia” may simply be related to a way of performing gender and sexual identity as opposed to overt discrimination and fear.

A comparison of international occupational therapy competencies : implications for Australian standards in the new millennium

Background/aim: A timely evaluation of the Australian Competency Standards for Entry-Level Occupational Therapists© (1994) was conducted. This thorough investigation comprised a literature review exploring the concept of competence and the applications of competency standards; systematic benchmarking of the Australian Occupational Therapy Competency Standards (OT AUSTRALIA, 1994) against other national and international competency standards and other affiliated documents, from occupational therapy and other cognate disciplines; and extensive nationwide consultation with the professional community. This paper explores and examines the similarities and disparities between occupational therapy competency standards documents available in English from Australia and other countries.----- Methods: An online search for national occupational therapy competency standards located 10 documents, including the Australian competencies.----- Results: Four 'frameworks' were created to categorise the documents according to their conceptual underpinnings: Technical-Prescriptive, Enabling, Educational and Meta-Cognitive. Other characteristics that appeared to impact the design, content and implementation of competency standards, including definitions of key concepts, authorship, national and cultural priorities, scope of services, intended use and review mechanisms, were revealed.----- Conclusion: The proposed 'frameworks' and identification of influential characteristics provided a 'lens' through which to understand and evaluate competency standards. While consistent application of and attention to some of these characteristics appear to consolidate and affirm the authority of competency standards, it is suggested that the national context should be a critical determinant of the design and content of the final document. The Australian Occupational Therapy Competency Standards (OT AUSTRALIA, 1994) are critiqued accordingly, and preliminary recommendations for revision are proposed.

Effect of presbyopic vision corrections on perceptions of driving difficulty

Objectives: As the population ages, more people will be wearing presbyopic vision corrections when driving. However, little is known about the impact of these vision corrections on driving performance. This study aimed to determine the subjective driving difficulties experienced when wearing a range of common presbyopic contact lens and spectacle corrections.----- Methods: A questionnaire was developed and piloted that included a series of items regarding difficulties experienced while driving under daytime and night-time conditions (rated on five-point and seven-point Likert scales). Participants included 255 presbyopic patients recruited through local optometry practices. Participants were categorized into five age-matched groups; including those wearing no vision correction for driving (n = 50), bifocal spectacles (n = 54), progressive spectacles (n = 50), monovision contact lenses (n = 53), and multifocal contact lenses (n = 48).----- Results: Overall, ratings of satisfaction during daytime driving were relatively high for all correction types. However, multifocal contact lens wearers were significantly less satisfied with aspects of their vision during night-time than daytime driving, particularly regarding disturbances from glare and haloes. Progressive spectacle lens wearers noticed more distortion of peripheral vision, whereas bifocal spectacle wearers reported more difficulties with tasks requiring changes of focus and those who wore no optical correction for driving reported problems with intermediate and near tasks. Overall, satisfaction was significantly higher for progressive spectacles than bifocal spectacles for driving.----- Conclusions: Subjective visual experiences of different presbyopic vision corrections when driving vary depending on the vision tasks and lighting level. Eye-care practitioners should be aware of the driving-related difficulties experienced with each vision correction type and the need to select corrective types that match the driving needs of their patients.

The phenomenology of utopia : reimagining the political

This thesis argues that the end of Soviet Marxism and a bipolar global political imaginary at the dissolution of the short Twentieth Century poses an obstacle for anti-systemic political action. Such a blockage of alternate political imaginaries can be discerned by reading the work of Francis Fukuyama and "Endism" as performative invocations of the closure of political alternatives, and thus as an ideological proclamation which enables and constrains forms of social action. It is contended that the search through dialectical thought for a competing universal to posit against "liberal democracy" is a fruitless one, because it reinscribes the terms of teleological theories of history which work to effect closure. Rather, constructing a phenomenological analytic of the political conjuncture, the thesis suggests that the figure of messianism without a Messiah is central to a deconstructive reframing of the possibilities of political action - a reframing attentive to the rhetorical tone of texts. The project of recovering the political is viewed through a phenomenological lens. An agonistic political distinction must be made so as to memorialise the remainders and ghosts of progress, and thus to gesture towards an indeconstructible justice which would serve as a horizon for the articulation of an empty universal. This project is furthered by a return to a certain phenomenology inspired by Cornelius Castoriadis, Claude Lefort, Maurice Merleau-Ponty and Ernesto Laclau. The thesis provides a reading of Jacques Derrida and Walter Benjamin as thinkers of a minor universalism, a non-prescriptive utopia, and places their work in the context of new understandings of religion and the political as quasi-transcendentals which can be utilised to think through the aporias of political time in order to grasp shards of meaning. Derrida and Chantal Mouffe's deconstructive critique and supplement to Carl Schmitt's concept of the political is read as suggestive of a reframing of political thought which would leave the political question open and thus enable the articulation of social imaginary significations able to inscribe meaning in the field of political action. Thus, the thesis gestures towards a form of thought which enables rather than constrains action under the sign of justice.

Learning in the third space : a sociocultural perspective on learning with analogies

Research on analogies in science education has focussed on student interpretation of teacher and textbook analogies, psychological aspects of learning with analogies and structured approaches for teaching with analogies. Few studies have investigated how analogies might be pivotal in students’ growing participation in chemical discourse. To study analogies in this way requires a sociocultural perspective on learning that focuses on ways in which language, signs, symbols and practices mediate participation in chemical discourse. This study reports research findings from a teacher-research study of two analogy-writing activities in a chemistry class. The study began with a theoretical model, Third Space, which informed analyses and interpretation of data. Third Space was operationalized into two sub-constructs called Dialogical Interactions and Hybrid Discourses. The aims of this study were to investigate sociocultural aspects of learning chemistry with analogies in order to identify classroom activities where students generate Dialogical Interactions and Hybrid Discourses, and to refine the operationalization of Third Space. These aims were addressed through three research questions. The research questions were studied through an instrumental case study design. The study was conducted in my Year 11 chemistry class at City State High School for the duration of one Semester. Data were generated through a range of data collection methods and analysed through discourse analysis using the Dialogical Interactions and Hybrid Discourse sub-constructs as coding categories. Results indicated that student interactions differed between analogical activities and mathematical problem-solving activities. Specifically, students drew on discourses other than school chemical discourse to construct analogies and their growing participation in chemical discourse was tracked using the Third Space model as an interpretive lens. Results of this study led to modification of the theoretical model adopted at the beginning of the study to a new model called Merged Discourse. Merged Discourse represents the mutual relationship that formed during analogical activities between the Analog Discourse and the Target Discourse. This model can be used for interpreting and analysing classroom discourse centred on analogical activities from sociocultural perspectives. That is, it can be used to code classroom discourse to reveal students’ growing participation with chemical (or scientific) discourse consistent with sociocultural perspectives on learning.

Corneal topography with Scheimpflug imaging and videokeratography : comparative study of normal eyes

PURPOSE: To compare the repeatability within anterior corneal topography measurements and agreement between measurements with the Pentacam HR rotating Scheimpflug camera and with a previously validated Placido disk–based videokeratoscope (Medmont E300). ------ SETTING: Contact Lens and Visual Optics Laboratory, School of Optometry, Queensland University of Technology, Brisbane, Queensland, Australia. ----- METHODS: Normal eyes in 101 young adult subjects had corneal topography measured using the Scheimpflug camera (6 repeated measurements) and videokeratoscope (4 repeated measurements). The best-fitting axial power corneal spherocylinder was calculated and converted into power vectors. Corneal higher-order aberrations (HOAs) (up to the 8th Zernike order) were calculated using the corneal elevation data from each instrument. ----- RESULTS: Both instruments showed excellent repeatability for axial power spherocylinder measurements (repeatability coefficients <0.25 diopter; intraclass correlation coefficients >0.9) and good agreement for all power vectors. Agreement between the 2 instruments was closest when the mean of multiple measurements was used in analysis. For corneal HOAs, both instruments showed reasonable repeatability for most aberration terms and good correlation and agreement for many aberrations (eg, spherical aberration, coma, higher-order root mean square). For other aberrations (eg, trefoil and tetrafoil), the 2 instruments showed relatively poor agreement. ----- CONCLUSIONS: For normal corneas, the Scheimpflug system showed excellent repeatability and reasonable agreement with a previously validated videokeratoscope for the anterior corneal axial curvature best-fitting spherocylinder and several corneal HOAs. However, for certain aberrations with higher azimuthal frequencies, the Scheimpflug system had poor agreement with the videokeratoscope; thus, caution should be used when interpreting these corneal aberrations with the Scheimpflug system.

Tear film surface quality with soft contact lenses using dynamic-area high-speed videokeratoscopy

Objectives. To evaluate the performance of the dynamic-area high-speed videokeratoscopy technique in the assessment of tear film surface quality with and without the presence of soft contact lenses on eye. Methods. Retrospective data from a tear film study using basic high-speed videokeratoscopy, captured at 25 frames per second, (Kopf et al., 2008, J Optom) were used. Eleven subjects had tear film analysis conducted in the morning, midday and evening on the first and seventh day of one week of no lens wear. Five of the eleven subjects then completed an extra week of hydrogel lens wear followed by a week of silicone hydrogel lens wear. Analysis was performed on a 6 second period of the inter-blink recording. The dynamic-area high-speed videokeratoscopy technique uses the maximum available area of Placido ring pattern reflected from the tear interface and eliminates regions of disturbance due to shadows from the eyelashes. A value of tear film surface quality was derived using image rocessing techniques, based on the quality of the reflected ring pattern orientation. Results. The group mean tear film surface quality and the standard deviations for each of the conditions (bare eye, hydrogel lens, and silicone hydrogel lens) showed a much lower coefficient of variation than previous methods (average reduction of about 92%). Bare eye measurements from the right and left eyes of eleven individuals showed high correlation values (Pearson’s correlation r = 0.73, p < 0.05). Repeated measures ANOVA across the 6 second period of measurement in the normal inter-blink period for the bare eye condition showed no statistically significant changes. However, across the 6 second inter-blink period with both contact lenses, statistically significant changes were observed (p < 0.001) for both types of contact lens material. Overall, wearing hydrogel and silicone hydrogel lenses caused the tear film surface quality to worsen compared with the bare eye condition (repeated measures ANOVA, p < 0.0001 for both hydrogel and silicone hydrogel). Conclusions. The results suggest that the dynamic-area method of high-speed videokeratoscopy was able to distinguish and quantify the subtle, but systematic worsening of tear film surface quality in the inter-blink interval in contact lens wear. It was also able to clearly show a difference between bare eye and contact lens wearing conditions.

Assessment of tear film surface quality using dynamic-area high-speed videokeratoscopy

A new method for noninvasive assessment of tear film surface quality (TFSQ) is proposed. The method is based on high-speed videokeratoscopy in which the corneal area for the analysis is dynamically estimated in a manner that removes videokeratoscopy interference from the shadows of eyelashes but not that related to the poor quality of the precorneal tear film that is of interest. The separation between the two types of seemingly similar videokeratoscopy interference is achieved by region-based classification in which the overall noise is first separated from the useful signal (unaltered videokeratoscopy pattern), followed by a dedicated interference classification algorithm that distinguishes between the two considered interferences. The proposed technique provides a much wider corneal area for the analysis of TFSQ than the previously reported techniques. A preliminary study with the proposed technique, carried out for a range of anterior eye conditions, showed an effective behavior in terms of noise to signal separation, interference classification, as well as consistent TFSQ results. Subsequently, the method proved to be able to not only discriminate between the bare eye and the lens on eye conditions but also to have the potential to discriminate between the two types of contact lenses.

An historical analysis of the development of thinking in the principal writings of Malcolm Knowles

Malcolm Shepherd Knowles was a key writer and theorist in the field of adult education in the United States. He died in 1997 and left a large legacy of books and journal articles. This thesis traced the development of his thinking over the 46-year period from 1950 to 1995. It examined the 25 works authored, co-authored, edited, reissued and revised by him during that period. The writings were scrutinised using a literature research methodology to expose the theoretical content, and a history of thought lens to identify and account for the development of major ideas. The methodology enabled a gradual unfolding of the history. A broadly-consistent and sequential pattern of thought focusing on the notion of andragogy emerged. The study revealed that after the initial phases of exploratory thinking, Knowles developed a practical-theoretical framework he believed could function as a comprehensive theory of adult learning. As his thinking progressed, his theory developed into a unified framework for human resource development and, later, into a model for the development of self-directed lifelong learners. The study traced the development of Knowles’ thinking through the phases of thought, identified the writings that belonged within each phase and produced a series of diagrammatic representations showing the evolution of his conceptual framework. The production of a history of the development of Knowles’ thought is the major outcome of the study. In addition to plotting the narrative sequence of thought-events, the history helps to explicate the factors and conditions that influenced Knowles’ thinking and to show the interrelationships between ideas. The study should help practitioners in their use and appreciation of Knowles’ works.

In vivo confocal microscopy of the bulbar conjunctiva

Background: The aim of this work is to develop a more complete qualitative and quantitative understanding of the in vivo histology of the human bulbar conjunctiva. Methods: Laser scanning confocal microscopy (LSCM) was used to observe and measure morphological characteristics of the bulbar conjunctiva of 11 healthy human volunteer subjects. Results: The superficial epithelial layer of the bulbar conjunctiva is seen as a mass of small cell nuclei. Cell borders are sometimes visible. The light grey borders of basal epithelial cells are clearly visible, but nuclei can not be seen. The conjunctival stroma is comprised of a dense meshwork of white fibres, through which traverse blood vessels containing cellular elements. Orifices at the epithelial surface may represent goblet cells that have opened and expelled their contents. Goblet cells are also observed in the deeper epithelial layers, as well as conjunctival microcysts and mature forms of Langerhans cells. The bulbar conjunctiva has a mean thickness of 32.9 1.1 mm, and a superficial and basal epithelial cell density of 2212 782 and 2368 741 cells/ mm2, respectively. Overall goblet and mature Langerhans cell densities are 111 58 and 23 25 cells/mm2, respectively. Conclusions: LSCM is a powerful technique for studying the human bulbar conjunctiva in vivo and quantifying key aspects of cell morphology. The observations presented here may serve as a useful marker against which changes in conjunctival morphology due to disease, surgery, drug therapy or contact lens wear can be assessed.

Peripheral ocular monochromatic aberrations

Aberrations affect image quality of the eye away from the line of sight as well as along it. High amounts of lower order aberrations are found in the peripheral visual field and higher order aberrations change away from the centre of the visual field. Peripheral resolution is poorer than that in central vision, but peripheral vision is important for movement and detection tasks (for example driving) which are adversely affected by poor peripheral image quality. Any physiological process or intervention that affects axial image quality will affect peripheral image quality as well. The aim of this study was to investigate the effects of accommodation, myopia, age, and refractive interventions of orthokeratology, laser in situ keratomileusis and intraocular lens implantation on the peripheral aberrations of the eye. This is the first systematic investigation of peripheral aberrations in a variety of subject groups. Peripheral aberrations can be measured either by rotating a measuring instrument relative to the eye or rotating the eye relative to the instrument. I used the latter as it is much easier to do. To rule out effects of eye rotation on peripheral aberrations, I investigated the effects of eye rotation on axial and peripheral cycloplegic refraction using an open field autorefractor. For axial refraction, the subjects fixated at a target straight ahead, while their heads were rotated by ±30º with a compensatory eye rotation to view the target. For peripheral refraction, the subjects rotated their eyes to fixate on targets out to ±34° along the horizontal visual field, followed by measurements in which they rotated their heads such that the eyes stayed in the primary position relative to the head while fixating at the peripheral targets. Oblique viewing did not affect axial or peripheral refraction. Therefore it is not critical, within the range of viewing angles studied, if axial and peripheral refractions are measured with rotation of the eye relative to the instrument or rotation of the instrument relative to the eye. Peripheral aberrations were measured using a commercial Hartmann-Shack aberrometer. A number of hardware and software changes were made. The 1.4 mm range limiting aperture was replaced by a larger aperture (2.5 mm) to ensure all the light from peripheral parts of the pupil reached the instrument detector even when aberrations were high such as those occur in peripheral vision. The power of the super luminescent diode source was increased to improve detection of spots passing through the peripheral pupil. A beam splitter was placed between the subjects and the aberrometer, through which they viewed an array of targets on a wall or projected on a screen in a 6 row x 7 column matrix of points covering a visual field of 42 x 32. In peripheral vision, the pupil of the eye appears elliptical rather than circular; data were analysed off-line using custom software to determine peripheral aberrations. All analyses in the study were conducted for 5.0 mm pupils. Influence of accommodation on peripheral aberrations was investigated in young emmetropic subjects by presenting fixation targets at 25 cm and 3 m (4.0 D and 0.3 D accommodative demands, respectively). Increase in accommodation did not affect the patterns of any aberrations across the field, but there was overall negative shift in spherical aberration across the visual field of 0.10 ± 0.01m. Subsequent studies were conducted with the targets at a 1.2 m distance. Young emmetropes, young myopes and older emmetropes exhibited similar patterns of astigmatism and coma across the visual field. However, the rate of change of coma across the field was higher in young myopes than young emmetropes and was highest in older emmetropes amongst the three groups. Spherical aberration showed an overall decrease in myopes and increase in older emmetropes across the field, as compared to young emmetropes. Orthokeratology, spherical IOL implantation and LASIK altered peripheral higher order aberrations considerably, especially spherical aberration. Spherical IOL implantation resulted in an overall increase in spherical aberration across the field. Orthokeratology and LASIK reversed the direction of change in coma across the field. Orthokeratology corrected peripheral relative hypermetropia through correcting myopia in the central visual field. Theoretical ray tracing demonstrated that changes in aberrations due to orthokeratology and LASIK can be explained by the induced changes in radius of curvature and asphericity of the cornea. This investigation has shown that peripheral aberrations can be measured with reasonable accuracy with eye rotation relative to the instrument. Peripheral aberrations are affected by accommodation, myopia, age, orthokeratology, spherical intraocular lens implantation and laser in situ keratomileusis. These factors affect the magnitudes and patterns of most aberrations considerably (especially coma and spherical aberration) across the studied visual field. The changes in aberrations across the field may influence peripheral detection and motion perception. However, further research is required to investigate how the changes in aberrations influence peripheral detection and motion perception and consequently peripheral vision task performance.

Change in colour appearance of small defocused lights

Small long wavelength lights (≤ 1’ arc) change colour appearance with positive defocus, appearing yellow or white. I investigated influences of longitudinal chromatic aberration and monochromatic aberrations on colour appearance of small narrow band lights. Seven cyclopleged participants viewed a small light (1’ arc diameter, λmax range 510 - 628 nm) centred within a 4.6’ black annulus and surrounded by a uniform white field under photopic light levels. An optical trombone varied focus. Participants were required to vary the focus by moving the optical trombone in either positive or negative direction and report when they noticed a change in appearance of the defocused narrow band light. Longitudinal chromatic aberration was controlled using a Powell achromatizing lens and its doublet and triplet components that neutralized, doubled and reversed the eye’s chromatic aberration, respectively. Changes in colour appearance for a 628 nm light occurred without any lens at +0.5 ± 0.2D defocus and with the doublet at +0.6 ± 0.2 D. The achromatizing lens did not affect appearance and the phenomenon was evident with the triplet for negative defocus (-0.5 ± 0.3 D). Adaptive optics correction of astigmatism and higher order monochromatic aberration did not affect magnitude significantly. Colour changes occurred despite a range of participant L/M cone ratios. Direction of change in colour appearance was reversed for short compared to long wavelengths. We conclude that longitudinal chromatic aberrations, but not monochromatic aberrations, are involved in changing appearance of small lights with defocus. Additional neuronal mechanisms that may contribute to the colour changes are considered.

Eyelid pressure and contact with the ocular surface

Purpose To investigate static upper eyelid pressure and contact with the ocular surface in a group of young adult subjects. Methods Static upper eyelid pressure was measured for 11 subjects using a piezoresistive pressure sensor attached to a rigid contact lens. Measures of eyelid pressure were derived from an active pressure cell (1.14 mm square) beneath the central upper eyelid margin. To investigate the contact region between the upper eyelid and ocular surface, we used pressure sensitive paper and the lissamine-green staining of Marx’s line. These measures combined with the pressure sensor readings were used to derive estimates of eyelid pressure. Results The mean contact width between the eyelids and ocular surface estimated using pressure sensitive paper was 0.60 ± 0.16 mm, while the mean width of Marx’s line was 0.09 ± 0.02 mm. The mean central upper eyelid pressure was calculated to be 3.8 ± 0.7 mmHg (assuming that the whole pressure cell was loaded), 8.0 ± 3.4 mmHg (derived using the pressure sensitive paper imprint widths) and 55 ± 26 mmHg (based on contact widths equivalent to Marx’s line). Conclusions The pressure sensitive paper measurements suggest that a band of the eyelid margin, significantly larger than the anatomical zone of the eyelid margin known as Marx’s line, has primary contact with the ocular surface. Using these measurements as the contact between the eyelid margin and ocular surface, we believe that the mean pressure of 8.0 ± 3.4 mmHg is the most reliable estimate of static upper eyelid pressure.

Describing ocular aberrations with wavefront vergence maps

A common optometric problem is to specify the eye’s ocular aberrations in terms of Zernike coefficients and to reduce that specification to a prescription for the optimum sphero-cylindrical correcting lens. The typical approach is first to reconstruct wavefront phase errors from measurements of wavefront slopes obtained by a wavefront aberrometer. This paper applies a new method to this clinical problem that does not require wavefront reconstruction. Instead, we base our analysis of axial wavefront vergence as inferred directly from wavefront slopes. The result is a wavefront vergence map that is similar to the axial power maps in corneal topography and hence has a potential to be favoured by clinicians. We use our new set of orthogonal Zernike slope polynomials to systematically analyse details of the vergence map analogous to Zernike analysis of wavefront maps. The result is a vector of slope coefficients that describe fundamental aberration components. Three different methods for reducing slope coefficients to a spherocylindrical prescription in power vector forms are compared and contrasted. When the original wavefront contains only second order aberrations, the vergence map is a function of meridian only and the power vectors from all three methods are identical. The differences in the methods begin to appear as we include higher order aberrations, in which case the wavefront vergence map is more complicated. Finally, we discuss the advantages and limitations of vergence map representation of ocular aberrations.