Depth-of-Focus of the Human Eye: Theory and Clinical Implications

Wang, Bin; Ciuffreda, Kenneth J.

doi:10.1016/j.survophthal.2005.11.003

Cited by 183 publications

(170 citation statements)

References 59 publications

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“…As retinal eccentricity increases so does the depth of focus which suggests an increase in blur tolerance 39 . When viewing a distant object the retinal image will fall within the distal boundary of the depth of focus while the retinal image will fall within the anterior boundary of the depth of focus while viewing a near target 40 . As the image falls within these boundaries the accommodative response will react in the form of a lag or a lead 40 .…”

Section: Depth Of Focusmentioning

confidence: 99%

“…When viewing a distant object the retinal image will fall within the distal boundary of the depth of focus while the retinal image will fall within the anterior boundary of the depth of focus while viewing a near target 40 . As the image falls within these boundaries the accommodative response will react in the form of a lag or a lead 40 . At the dark focus the accommodative demand and response are equal 40 .…”

Section: Depth Of Focusmentioning

confidence: 99%

“…As the image falls within these boundaries the accommodative response will react in the form of a lag or a lead 40 . At the dark focus the accommodative demand and response are equal 40 .…”

Section: Depth Of Focusmentioning

confidence: 99%

“…An increased depth of focus is due to low contrast, shorter wavelengths, retinal eccentricity, increased accommodative error and increased age, while a smaller depth of focus is found with a better visual acuity which suggests more accurate accommodation. More accurate accommodation can also be achieved by enhancing the depth of focus with visual therapy 40 . Depth of focus varies with direction of gaze and thus the accommodative response varies as well 41 .…”

Section: Depth Of Focusmentioning

confidence: 99%

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The near triad and associated visual problems

Emslie

Sachs²,

Claassens

et al. 2007

African Vision and Eye Health

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When a person changes fixation from one target, at a given fixation distance, to another target, at an alternate fixation distance, a number of ocular systems need to be altered in order to maintain clear single binocular vision. One such system is that of accommodation, involving either positive or negative accommodation 1 . When viewing an object at six meters, a distance known optometrically as optical infinity, it is assumed that parallel light rays enter the eye. For an emmetrope this results in zero accommodative demand and therefore zero accommodation. When viewing an object closer than 6 meters positive accommodation is required. This involves intraocular lens changes which ultimately increase the refractive power of the eye, allowing the rays to form a point focus on the retina. The opposite process, negative accommodation, occurs when an object is fixated further away from some near fixation point. Accommodation can therefore be thought of as the process by which the refractive power of the eye is altered to ensure a clear retinal image 1 .It should also be noted that a change in the position of the visual axes must also take place 1 . This occurs to ensure that a single image of the target is seen. The change in relative position of the visual axis is called convergence when the angle formed by the visual axes increases, and divergence when this angle decreases 1 .When a person fixates a near target an additional process takes place, that is, pupillary constriction. This occurs together with accommodation and convergence, and alters the depth of focus 1 . These three sub-systems work together as a synkinesis known as the near triad 1, 2 .One should not forget the fact that the processes mentioned above are very complex and involve numerous pathways, the details of which are little known. As a result it is easy to understand that many problems can occur in each process, resulting in visual problems. This paper serves to address some of those visual problems. AccommodationThe amplitude of accommodation represents the closest near focusing response that can be produced with maximal voluntary effort in the fully corrected eye 2 . From around five years of age to around 52 years of age, the accommodative amplitude progressively decreases at a rate of approximately 0.30 D per year 2 . Various theorists attribute the loss of accommodation to changes in the elastic properties of the lens, changes in the action of the ciliary muscle, or both 3 . The anterior chamber depth, shape of the lens, refractive index and position of the lens surfaces change with age, affecting the accommodative process 4 . This leads to the development of presbyopia. The amplitude of accommodation inevitably decreases from 11 D or more at age 10 to nearly 0 D by age 70 years. This means that an emmetropic child can focus an object as close as 10 cm, while an older adult must move objects at least a metre or more away to see them clearly 3 . †

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Section: Depth Of Focusmentioning

confidence: 99%

Section: Depth Of Focusmentioning

confidence: 99%

“…As the image falls within these boundaries the accommodative response will react in the form of a lag or a lead 40 . At the dark focus the accommodative demand and response are equal 40 .…”

Section: Depth Of Focusmentioning

confidence: 99%

Section: Depth Of Focusmentioning

confidence: 99%

See 2 more Smart Citations

The near triad and associated visual problems

Emslie

Sachs²,

Claassens

et al. 2007

African Vision and Eye Health

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show abstract

“…[2][3][4] Among these, the Stiles-Crawford effect (SCE) is one of the most important retinal factor. This is a consequen-ce of the directional sensitivity of the foveal photoreceptors whereby they elicit a visual response more efficiently when the incoming pencil of light lies close to the optical axis (from centre of the pupil) rather than when it enters obliquely.…”

Section: Introductionmentioning

confidence: 99%

Depth-of-Focus and its Association with the Spherical Aberration Sign. A Ray-Tracing Analysis

Bakaraju

Ehrmann

Papas

et al. 2010

Journal of Optometry

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PURPOSE: To investigate the relationship between the sign of spherical aberration (SA) and the corresponding depth-of-focus (DoF) values around best focus, at three different spatial frequencies (SF). Additionally, to study the influence of the Stiles-Crawford effect (SCE) on DoF. METHODS: We modeled schematic eyes having a range of SA values, C (4, 0), from -0.20 to 0.20 μm, at 6 mm pupil, in a ray-tracing software (Zemax). The through-focus optical performance was obtained via Modulation Transfer Function (MTF) calculations using thin paraxial lenses in-front of the model eye, from -2.00 to+2.00 D in 0.05D steps. Through-focus full-width (defocus) occurring at the half maximum of MTF value was considered as DoF, in diopters. RESULTS: For the low-SF configuration, +SA and -SA results were close to being mirror symmetries of one another. However, for midand high-SF targets, in the SA range spanning from -0.15 to 0.15 μm, models of equal SA magnitude but opposite sign produced similar DoF measures, but those with SA more negative than -0.15 μm showed marginally higher DoF than their positive counterparts. The SCE improved DoF for low SF (10 cycles/mm), while for mid and higher SF (>30 cycles/mm) mixed results were observed. CONCLUSIONS: As regards presbyopic-correction strategies that use deliberately induced aberrations to increase the depth of focus, the current study suggests that both positive and negative SA have equal potential. However, practical considerations will probably limit the useful DoF achievable through the utilization of SCE in presbyopes. for reference to a contemporary record detailing refractive history. RESUMEN OBJETIVO:Investigar, para tres frecuencias espaciales (FE) distintas, la relación entre el signo de la aberración esférica (AE) y la correspondiente profundidad de foco (PdF) alrededor del mejor foco. Además, se estudiará cómo afecta el efecto Stiles-Crawford (ESC) a la PdF. MÉTODOS: Hemos utilizado un modelo de ojo esquemático con distintos valores de aberración esférica (AE) (C (4, 0) comprendido entre 0.20 y 0.20 μm, para un diámetro de pupila de 6 mm) para investigar la relación que existe entre el signo de la AE y la correspondiente profundidad de foco (PdF) alrededor del mejor foco para tres frecuencias espaciales (FE) distintas. También se estudió la influencia del efecto Stiles-Crawford (ESC). RESULTADOS: Para FE bajas, los resultados correspondientes a +AE y AE presentan simetría especular. Sin embargo, para FE medias y altas, y en el intervalo de AE comprendido entre 0.15 y 0.15 μm, modelos de igual AE (en módulo) pero distinto signo da lugar a valores de PdF similares, pero para valores de AE más negativos que 0.15 μm se obtuvieron PdF ligeramente más altas que para un valor positivo equivalente de AE. El ESC hace que aumente la PdF para FE bajas (10 ciclos/mm), mientras que para FE medias y altas (>30 ciclos/mm) se observan resultados variados. CONCLUSIONES: En lo que respecta a las estrategias de corrección de la presbicia basadas en la inducción deliberada de ...

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The Physiology of 3D Perception

Lüeder

2011

3D Displays

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Depth-of-Focus of the Human Eye: Theory and Clinical Implications

Cited by 183 publications

References 59 publications

The near triad and associated visual problems

The near triad and associated visual problems

Depth-of-Focus and its Association with the Spherical Aberration Sign. A Ray-Tracing Analysis

The Physiology of 3D Perception

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