**2. Nomenclature, function, and analysis**

*Visual field*: Visual spatial array produces or reflects the visual rays of the image transmitted to the brain.

*Right visual field (RVF)*: Visual spatial array that produces or reflects the visual rays of the image transmitted to the brain's left hemisphere.

*Left visual field (LVF)*: Visual spatial array that produces or reflects the visual rays of the image transmitted to the brain's right hemisphere.

*Central fixation point (P)*: The visual field point that is projected into the fovea centralis in both eyes.

*Binocular visual field*: The space region producing the projection visual rays image in the temporal retina.

*Peripheral visual field*: The space region producing the projection visual rays image in the nasal retina.

*Visual axis*: Imaginary straight line passing through the central fixation point and the fovea centralis or intersection of visual plane with vertical meridian plane.

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*Intraocular Forced Convection Mechanism Defect as Probable Cause of Normal-Tension…*

*Horizontal meridian plane*: The ocular bulb intersection plane, in the horizontal

*Rectus muscles*: These maintain the central fixation point projection in the fovea

*Superior oblique muscle*: This controls the corneal accommodation to adjust the projected image on the nasal fovea horizontal meridian perimeter line to the image projected on the contralateral temporal fovea horizontal meridian perimeter line, admitted as fixed. It commands the forced convection system extrinsic muscle

*Inferior oblique muscle*: This has an excyclotorsive physical effort and is antagonistic to the superior oblique muscle physical effort, to avoid the pathological

*Ciliary muscle*: This controls lens accommodation to obtain the best-projected

*Corneal accommodation*: The cornea curvature adaptation to compensate for the deformations of the conical projections through two distinct foci using image

*Optic disc (OD)*: Oval region of the eye nasal retina without cones and rods. *Blind spot (BS)*: A visual field oval region that is projected onto the optical disc

*Optical disc neural correspondent (NC)*: A visual field oval region, this is projected on the phototransducers, of the contralateral eye temporal retina, which has its periphery as the neural correlates of the phototransducers neural from optic disc

*Forced convection mechanism*: The eye has two independent systems of forced convection: one under the extrinsic muscle action and the other under the intrinsic muscle action. The extrinsic muscles move the mobile mass in the cornea, trabecular meshwork, and retina, and the intrinsic muscles move the mobile mass in the

*Iris*: Main functions. Reduces the light diffusion in the projected image in the retina and prevents aqueous humor return when the pressure in the anterior chamber is greater than in the posterior one during the cornea accommodation process [2, 3]. After cataract surgery, there may be reflux of aqueous humor from the anterior chamber to the posterior chamber during the period of adaptation to the artificial lens, and metabolic residue contaminates the artificial intraocular lens

**Figure 1** shows a components schematic diagram necessary for image formation, image transmission to the brain, and how image fusion occurs. At the top of the diagram is shown the visual field. From this region, light rays are emitted or reflected to be projected into the retina. The projected image inversion projected onto the retina is a physical form of the selection of light rays that form the image of an object or body situated in the visual field. The physical principle can be best verified by a pinhole camera. The central fixation point "P" divides the visual field into the right (RVF) and left (LVF) visual fields, which are transmitted to the contralateral brain hemispheres. The visual field can also be divided into the binocular visual field, the region seen by both eyes, and the peripheral visual field, the region seen by one eye. Then, on the temporal retina, the image produced in the contralateral

*Vertical meridian plane*: The plane of intersection of the ocular bulb, in the

*DOI: http://dx.doi.org/10.5772/intechopen.89934*

meridian perimeter line.

incyclotorsive movement.

centralis.

fusion.

of ipsilateral eye.

lens and Schlemm's canal [4].

causing posterior capsular opacification.

**2.1 Main vision characteristics**

perimeter line vertical meridian.

*Visual plane*: Defined by the two visual axes.

action. Its action includes an incyclotorsion physical effort.

periphery of the ipsilateral eye to the visual field.

image on the temporal fovea and view objects at varying distances.

*Intraocular Forced Convection Mechanism Defect as Probable Cause of Normal-Tension… DOI: http://dx.doi.org/10.5772/intechopen.89934*

*Visual plane*: Defined by the two visual axes.

*Horizontal meridian plane*: The ocular bulb intersection plane, in the horizontal meridian perimeter line.

*Vertical meridian plane*: The plane of intersection of the ocular bulb, in the perimeter line vertical meridian.

*Rectus muscles*: These maintain the central fixation point projection in the fovea centralis.

*Superior oblique muscle*: This controls the corneal accommodation to adjust the projected image on the nasal fovea horizontal meridian perimeter line to the image projected on the contralateral temporal fovea horizontal meridian perimeter line, admitted as fixed. It commands the forced convection system extrinsic muscle action. Its action includes an incyclotorsion physical effort.

*Inferior oblique muscle*: This has an excyclotorsive physical effort and is antagonistic to the superior oblique muscle physical effort, to avoid the pathological incyclotorsive movement.

*Ciliary muscle*: This controls lens accommodation to obtain the best-projected image on the temporal fovea and view objects at varying distances.

*Corneal accommodation*: The cornea curvature adaptation to compensate for the deformations of the conical projections through two distinct foci using image fusion.

*Optic disc (OD)*: Oval region of the eye nasal retina without cones and rods. *Blind spot (BS)*: A visual field oval region that is projected onto the optical disc of ipsilateral eye.

*Optical disc neural correspondent (NC)*: A visual field oval region, this is projected on the phototransducers, of the contralateral eye temporal retina, which has its periphery as the neural correlates of the phototransducers neural from optic disc periphery of the ipsilateral eye to the visual field.

*Forced convection mechanism*: The eye has two independent systems of forced convection: one under the extrinsic muscle action and the other under the intrinsic muscle action. The extrinsic muscles move the mobile mass in the cornea, trabecular meshwork, and retina, and the intrinsic muscles move the mobile mass in the lens and Schlemm's canal [4].

*Iris*: Main functions. Reduces the light diffusion in the projected image in the retina and prevents aqueous humor return when the pressure in the anterior chamber is greater than in the posterior one during the cornea accommodation process [2, 3]. After cataract surgery, there may be reflux of aqueous humor from the anterior chamber to the posterior chamber during the period of adaptation to the artificial lens, and metabolic residue contaminates the artificial intraocular lens causing posterior capsular opacification.

#### **2.1 Main vision characteristics**

**Figure 1** shows a components schematic diagram necessary for image formation, image transmission to the brain, and how image fusion occurs. At the top of the diagram is shown the visual field. From this region, light rays are emitted or reflected to be projected into the retina. The projected image inversion projected onto the retina is a physical form of the selection of light rays that form the image of an object or body situated in the visual field. The physical principle can be best verified by a pinhole camera. The central fixation point "P" divides the visual field into the right (RVF) and left (LVF) visual fields, which are transmitted to the contralateral brain hemispheres. The visual field can also be divided into the binocular visual field, the region seen by both eyes, and the peripheral visual field, the region seen by one eye. Then, on the temporal retina, the image produced in the contralateral

#### **Figure 1.**

*Main vision characteristics.*

visual field (eye nasal visual field) is projected, and on the nasal retina, the image produced in the ipsilateral visual field (eye temporal visual field) is projected. The projected image to an optical disc region without photoreceptors cannot be transmitted to the contralateral cerebral hemisphere. The projected image in the temporal retina is transmitted to the brain's ipsilateral hemisphere, and the projected image in the nasal retina is transmitted to the brain's contralateral hemisphere.

#### **2.2 Binocular vision physiology**

In the summary, below, as shown in **Figure 1**, the binocular vision main controls are described. The projected image in the temporal retina is transmitted to the cerebral ipsilateral hemisphere, which controls the rectus muscles movement, to improve eyeball position fixation and controls the ciliary muscle movement to accommodate the lens and improve focusing. The image projected on the nasal retina is transmitted to the contralateral cerebral hemisphere, which controls the superior oblique muscle movement, changing the cornea curvature to adjust the projected image size in the nasal retina to the projected image in the contralateral temporal retina.

**Figure 2** shows the fusion process of the retinal nasal image with the contralateral eye temporal image. Of course, a single movement by the oculomotor muscle reflects the movement of all the other muscles and consequently causes changes in these images. These changes, however, have not been taken into consideration here,

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**Figure 2.**

*Image fusions (superior oblique muscle action).*

admitted as a genetic or acquired deficiency.

*Intraocular Forced Convection Mechanism Defect as Probable Cause of Normal-Tension…*

as to emphasize the action of the superior oblique muscle action on the nasal images received by the brain. In binocular vision, the "NC" and "BS" regions are coincident and have identical perimeter images. For example, if we take the written title of a work in the binocular visual field, three regions can be seen: the "P" fixation point, the "BS" regions that are projected in the ipsilateral eyes nasal retinas, and the "NC" regions that are projected in the contralateral eye temporal retinas (when the binocular visual gaze is in the lateral limit the nose profile protrudes through the ipsilateral dashed line). **Figure 2** shows how these images are transmitted to the brain. The image transmitted by the temporal retina is the reference image in the fusion of images, so it does not have primary changes related to the fusion of images. The image transmitted by the nasal retina is presented with an increase of 10% for the right eye and a 10% reduction for the left eye. In the brain, the neural region related to the optic disc (OD) region of the retina corresponds to the "BS" region of the visual field and is the corresponding neural region "NC." Note that the variation of 10% causes in the visual field the displacement of the "BS" regions to the left, so the two regions are not in the location shown in **Figure 2**. In the fusion of images, the brain commands the superior oblique muscle of the contralateral eye so as to adjust the projected image in the nasal retina to the projected image in the temporal retina of the ipsilateral eye. **Figure 2** shows the merger performed in two steps. Any change in the temporal image corresponds to a displacement of the "NC" region in the visual field. The image projected in the temporal retina is the main one because, in addition to being a reference in the fusion of the images, it is transmitted to the ipsilateral hemisphere to control the contralateral limbs and the movement of the ipsilateral eye. Given this, the reason for lateral dominance may be

Lens accommodation and of the cornea are the two independent intraocular mass transfer movements, by forced convection. To eliminate metabolic residues without storing them, it is necessary to maintain the concentration of metabolic compounds uniform throughout the mobile mass, so that the simple draining of the mobile mass removes the metabolic residues without leaving accumulations. In order to standardize the concentration of metabolic residue produced, it is

*DOI: http://dx.doi.org/10.5772/intechopen.89934*

*Intraocular Forced Convection Mechanism Defect as Probable Cause of Normal-Tension… DOI: http://dx.doi.org/10.5772/intechopen.89934*

#### **Figure 2.**

*Image fusions (superior oblique muscle action).*

as to emphasize the action of the superior oblique muscle action on the nasal images received by the brain. In binocular vision, the "NC" and "BS" regions are coincident and have identical perimeter images. For example, if we take the written title of a work in the binocular visual field, three regions can be seen: the "P" fixation point, the "BS" regions that are projected in the ipsilateral eyes nasal retinas, and the "NC" regions that are projected in the contralateral eye temporal retinas (when the binocular visual gaze is in the lateral limit the nose profile protrudes through the ipsilateral dashed line). **Figure 2** shows how these images are transmitted to the brain. The image transmitted by the temporal retina is the reference image in the fusion of images, so it does not have primary changes related to the fusion of images. The image transmitted by the nasal retina is presented with an increase of 10% for the right eye and a 10% reduction for the left eye. In the brain, the neural region related to the optic disc (OD) region of the retina corresponds to the "BS" region of the visual field and is the corresponding neural region "NC." Note that the variation of 10% causes in the visual field the displacement of the "BS" regions to the left, so the two regions are not in the location shown in **Figure 2**. In the fusion of images, the brain commands the superior oblique muscle of the contralateral eye so as to adjust the projected image in the nasal retina to the projected image in the temporal retina of the ipsilateral eye. **Figure 2** shows the merger performed in two steps. Any change in the temporal image corresponds to a displacement of the "NC" region in the visual field. The image projected in the temporal retina is the main one because, in addition to being a reference in the fusion of the images, it is transmitted to the ipsilateral hemisphere to control the contralateral limbs and the movement of the ipsilateral eye. Given this, the reason for lateral dominance may be admitted as a genetic or acquired deficiency.

Lens accommodation and of the cornea are the two independent intraocular mass transfer movements, by forced convection. To eliminate metabolic residues without storing them, it is necessary to maintain the concentration of metabolic compounds uniform throughout the mobile mass, so that the simple draining of the mobile mass removes the metabolic residues without leaving accumulations. In order to standardize the concentration of metabolic residue produced, it is

necessary to equalize the mobile mass movement in all intraocular regions. Over many years, these accumulated residues are agglutinated and form droplets that grow with the adjacent droplets to modify image projections on the retina and consequently modify the dimensions and position of the eyeballs as well as the ocular movements. Because of these ocular changes, the patient begins to suffer and to present the symptoms and signs of various ocular pathologies. As a result, the elimination of agglutinated residues through the anterior chamber can become lodged in the trabecular meshwork and increase the aqueous humor passage resistance, resulting in increased intraocular pressure.

#### **2.3 Focusing, fixation, and fusion**

Binocular vision is based on fixation by the eyes on an object of the visual field (rectus muscle action). To fix the eyes on an object, it is necessary that the eyes are able to focus the object (ciliary muscle action), so this action must be faster than the fixing action. When focusing and fixing on an object it, is necessary to adjust the binocular images to compensate, between them, for the distortions produced by the conical projections due to the horizontal distance between the eyes (superior oblique muscle action). Thus, action must be slower than the fixation action. In the appendix, a first-order linear model is used to analyze, by comparison, the rapidity effects among the changed muscular actions of state in the focalization, fixation, and fusion of the images, for binocular vision. Here, 0% is the initial state and 100% is the final state. The analytical equation that establishes the transition between the equilibrium states (initial and final) depends on the parameter τ (time constant). Thus, three time constants are required: τC (ciliary muscle), τR (rectus muscles), and τS (superior oblique muscle). For this, the relation among the time constants is given by Eq. (1).

$$
\mathsf{T}\_{\mathsf{C}} < \mathsf{T}\_{\mathsf{R}} < \mathsf{T}\_{\mathsf{S}} \tag{1}
$$

**65**

*Intraocular Forced Convection Mechanism Defect as Probable Cause of Normal-Tension…*

an visual field surface imaginary line, when the eyes travel the smallest angular

When the ocular direction shifts from point "F" to point "I," point "M," the contralateral eye visual axis intersection with the surface of the visual field (initially coincides with point "F"), is shifted to point "I." The "M" point moves across an imaginary line on the surface of the lateral visual field with the smallest angular displacement of the axial axis of the contralateral eye. In this trajectory, the contralateral eye maintains its focus at the "M" point because the ciliary accommodation time constant, τC, is much less than the ocular displacement time constant, τR (rectus muscles). Therefore, relative to the visual field laterality, the image projected on the contralateral ocular temporal retina is the primary image because it is the image used by the brain to control eye movement. The image projected on the nasal retina of the ipsilateral eye is the secondary image, because it is the image used by the brain to control the cornea accommodation movement, a slower movement, due to the time constant of the cornea accommodation, τS (superior oblique muscle), which is much longer than the ocular displacement time constant, τR (rectus muscles). Therefore, in this eye movement, the dominant eye is contralateral to the laterality of the "I" point visual field, and the auxiliary eye is ipsilateral because its movement depends on the

fusion of the images to keep the projection onto its fovea, the "M" point.

anterior trajectory, so eye dominance is circumstantial.

of dehydrated metabolic secretions.

On the return trajectory, **Figure 3b**, the current fixation point "F" is the previous "I" point, and the current interest point "I" is the previous "F" point; hence the current movable fixation point "M" will have an ipsilateral trajectory to the anterior trajectory of "M." Then, the dominant and auxiliary eyes will be contralateral in the

*Refraction error*: Eyesight adaptation to dark is the common pathological symptom that precedes refractive error (see [3]). In 1619 Scheiner, *apud* [12], proved in his experiments, made with holes in a card, that an object is seen in each direction at a different distance. You can reproduce the effects perceived by Scheiner, by fixing the gaze on a distant object, through a pinhole in a paper pressed against the eyelid. When you move the paper without removing it from the eyelid, you can perceive the image of the object jumping from one position to another or moving its shape. The jump indicates the same pathology observed by Scheiner, and the change in form is another presentation of the same pathology [2]. This pathology can be acquired by the dehydrated accumulation of intraocular metabolic residues agglutinated in the form of drops. These drops form lenses that can produce overlapping images (causing blurred vision, floaters, monocular polyopia, and photopsia with and without photochromatic dispersion) and, depending on their transparency, make light transmission difficult. In the postoperative period of cataract surgery, patients report having a clearer view through the operated eye (greater light transmission in the artificial lens). Patients may report blurred vision and secretions released from the anterior surface of the cornea (corneal accommodation variation) and floaters (the metabolic mass stored in the lens prevented their viewing). In Ref. [2] the different symptoms of myopia, hypermetropia, astigmatism, and presbyopia are shown as visual disturbances of the same origin, the intraocular accumulation

*Ocular hypertension*: This can be caused by an imbalance in the production, concentration, and drainage of eye movable mass. Increased mass transfer resistance across the trabecular meshwork is an important impediment to aqueous humor drainage. Corneal accommodation movement failure hinders its mass transfer movement, thus being the major factor in the metabolic residue storage in the cornea [5]. The cornea stored metabolic residue elimination process consists in the movement of its curvature, in order to recover its healthy accommodation. In this process, the residues leave the two surfaces and are eliminated by dilution or suspension. On the anterior

*DOI: http://dx.doi.org/10.5772/intechopen.89934*

displacement between the "F" and "I" points.
