**4.1 Etiopathogenesis of monovision**

*Current Cataract Surgical Techniques*

**3.2 Eye exercises**

least contraction.

the opportunity to adjust eye control.

image of the ipslateral hand, **Figure 1c2**.

Then, each cerebral hemisphere receives ipsilateral hearing and the projected image on the temporal retina of the ipsilateral eye, and, if it exists, includes the image of the contralateral hand, **Figure 1c1**, in addition to receiving the image projected on the nasal retina of the contralateral eye, and, if it exists, it includes the

Each cerebral hemisphere controls, the contralateral superior oblique muscle, **Figure 1c2** and all other ipsilateral eye muscles (the rectus, inferior oblique, ciliary, iris, superior eyelid lift), control the movements of the contralateral hand and the

The same interpretation of the oculomotor action of writing covering a calligraphic text, exposed through the diagram shown in **Figure 1**, is used in the analysis of the focus of a person's gaze, at the lateral limit of his binocular vision, the tip of the finger of his hand, very near to the nasal root, **Figure 2**, as children do in their initial oculomotor development. In **Figure 2a**, the right eye is diagrammed, positioning its visual axis tangent to the nasal root and intercepting the visual axis of the contralateral eye at a focus point common to both eyes, on the middle finger, of the contralateral hand, and on the **Figure 2b**, the left eye is diagrammed, positioning its visual axis tangent to the nasal root and intercepting the visual axis of the contralateral eye at a focus point common to both eyes, on the middle finger, of the contralateral hand. So:

• Ocular dominance, whether natural or pathological, fuses the images and alternates the dominant eye. As strabismus refers to eye misalignment [6], there can be no fusion of images or alternation in eye dominance, but surgical correction of strabismus is performed to restore or reconstruct normal eye alignment, to obtain normal visual acuity in each eye and be able to improve image fusion

[6], then the patient can recover the alternating ocular dominance.

• The natural ocular dominance of the right eye, **Figure 2a**, and the left eye, **Figure 2b**, have their motor control image projected on the contralateral eye nasal retina, because in their ipsilateral temporal retina no image is projected. Thus, the contralateral cerebral hemisphere adjusts the greatest contraction of its superior oblique muscle, just as it adjusts the greatest contraction of the non-dominant eye natural lens, with its superior oblique muscle having the

• By protecting newborns' nails with gloves to prevent injury these children miss

• In the positions shown in **Figure 2**, the contraction of the twelve oculomotor muscles is constant, for any distance of focus, therefore, it is an extremely important position to adjust the refractive power of the non-dominant eye natural lens.

*Diagram showing the lateral limits of the binocular visual field. (a) left binocular limit, (b) right binocular* 

rotating movement of the head in the contralateral direction **Figure 1c1**.

**78**

*limit.*

**Figure 2.**

As [7] in monovision one eye (usually the dominant eye) is corrected for distance and the other eye is corrected for reading and according to [8] a lens set to far distances is implanted in your dominant eye, while a lens set to near distances is implanted in your non-dominant eye. It works because your brain automatically adjusts your visual system to achieve clear vision when you are focusing on near and distant objects [8].

This surgical technique uses pathological ocular dominance to maintain it and does not encourage its correction. In [2] it was demonstrated that in natural binocular vision, ocular dominance is alternated between the two eyes. But in [9] it says "If a strong degree of dominance is not apparent in a dominant eye test, it's more likely a person has mixed ocular dominance (*also called alternating ocular dominance*), where one eye is dominant for certain functions or tasks, and the other eye is dominant at different times", in addition to citing two criteria to determine ocular dominance, but under the hypothesis of alternating ocular dominance, that is, it identifies the natural ocular dominance acting alternately in both eyes.

In the work development, in the research group, it was found that in a simple frontal photo, a selfie, it is possible to perceive the result of pathological ocular dominance, but it is necessary to be sure that the photo is really frontal [10], see photo of **Figure 3**, because vicious ocular dominance can cause slight ocular deviation. Another way is to focus on the pencil tip that moves slowly to the nose root. The eye that keeps focusing on the pencil tip is the the dominant eye and the contralateral eye moves away quickly in its temporal direction, losing the focus point is the nondominant eye, because who has natural binocular vision keeps both eyes focused on the pencil tip until it reaches the root of the nose effortlessly. The pathological ocular dominance is known as ocular dominance and in this chapter it is addressed only in its connections in planning and sequelae related to monovision surgery.

If a person, with one eye, sees the nearby objects well and with the contralateral eye sees the distant objects well, this situation was built through the convenience and personal habits, that is why, in this chapter, it is called ocular dominance, which is constructed involving eye shape and movement, in addition to the construction of neural communication, therefore, its surgical reproduction is impossible without the possibility of binocular vision. In this chapter, ocular dominance after monovision surgery is called dichotomous ocular dominance. Considering scientific knowledge, two surgical options are presented only for comparison with monovision surgery:


#### **Figure 3.**

*The four rectangles are equal to two. Dominant left eye, greater nasal distance [10].*

It is very important to point out that the eye projections are conical consequently the visual field perimeter for near focusing is much smaller than the visual field perimeter for distant focusing, therefore the cylindrical diopter due to the images fusion is greater for near focusing, as was verified in [11]. It should be noted that the opposite reactions in 5 cases mentioned can be explained by the probable differences in the distribution of accumulated metabolic residue as presented in [12]. It is important to consider this diopter variation when calculating the lens power for focusing at near distances. This dioptric variation is important for the forced convection mechanism in the cornea and retina, in addition to moving the trabecular meshwork, thus it is an important option to be chosen.

After monovision cataract surgery there is no balance state because it is impossible to fuse images at near or distant focusing distances, causing a complete dichotomy difficult to overcome.

#### **4.2 Case report**

A 69 years old female patient in Recife, Brazil, who underwent, in June 2019, cataract surgery in the left eye with implantation of the LW 625A lens power + 24.00 [13], with near focus. **Table 1** shows the corrective lenses used by the patient who, despite having a lens prescribed before the surgery, but that patient did not need corrective lenses to renew the national driver's license three months before the surgery and the **Figure 4** shows the chronology of the examinations performed. In November 2020 the situation came to a stable discomfort. There is no solution, through the patient's health plan, because all the professionals who examine her report that the surgeon's work was very good, there was good healing and the lens very well positioned, it seems to be describing a work of art, but at the being asked about headaches, the health plan ophthalmologists, inform that there is nothing to do with the surgery and that the patient must have another problem and should seek another specialist, such as a neurologist, to know the source of the pain, because the surgery is perfect.

**Preoperative**: The patient can choose between a national or imported prosthesis, for an additional fee, but did not inform the origin of the lens. The patient filled out a form informing social life and answering about the lifestyle after surgery, without any explanation of the result of the choice:


Based on the patient's response, the surgeon defines the solution without informing the patient of the result found.

It is devoid of logic for someone to seek the help of a professional to obtain a lower quality of life. On the other hand, when there are several alternatives for cataract surgery with an IOL implant, the choice of treatment must be given to the patient, given that it is the patient who will live with the consequences of the surgery.

**81**

**Figure 4.**

**Figure 4** shows the chronology of the surgery and exams, in addition to simulated keratometry of the corneas before, **Figure 4a**, and after, **Figure 4b**, surgery. The anterior corneal surface of the left eye, after surgery, is more regular

*History of exams performed by the patient. (a) before surgery, (b) after surgery.*

*Visual Impairment Caused by Monovision Surgical Design*

**Note Rx. Spherical Cylindrical Axis**

Before surgery D.V. +0.75 +1.50 −0.75 −0.25 123° 170°

After surgery D.V. 0.00 −2.25 −0.25 −1.50 41° 118°

Currently D.V. −0.75 −3.00 — —

N.V. +3.00 add —

N.V. +3.00 add —

N.V. +3.00 add —

**O.D. O.S. O.D. O.S. O.D. O.S.**

*DOI: http://dx.doi.org/10.5772/intechopen.95770*

**Table 1.**

*Lenses prescribed by doctors.*

*Visual Impairment Caused by Monovision Surgical Design DOI: http://dx.doi.org/10.5772/intechopen.95770*


#### **Table 1.**

*Current Cataract Surgical Techniques*

dichotomy difficult to overcome.

**4.2 Case report**

**Figure 3.**

It is very important to point out that the eye projections are conical consequently

After monovision cataract surgery there is no balance state because it is impos-

A 69 years old female patient in Recife, Brazil, who underwent, in June 2019, cataract surgery in the left eye with implantation of the LW 625A lens power + 24.00 [13], with near focus. **Table 1** shows the corrective lenses used by the patient who, despite having a lens prescribed before the surgery, but that patient did not need corrective lenses to renew the national driver's license three months before the surgery and the **Figure 4** shows the chronology of the examinations performed. In November 2020 the situation came to a stable discomfort. There is no solution, through the patient's health plan, because all the professionals who examine her report that the surgeon's work was very good, there was good healing and the lens very well positioned, it seems to be describing a work of art, but at the being asked about headaches, the health plan ophthalmologists, inform that there is nothing to do with the surgery and that the patient must have another problem and should seek another specialist, such as a neurologist, to know the source of the pain, because the surgery is perfect.

**Preoperative**: The patient can choose between a national or imported prosthesis, for an additional fee, but did not inform the origin of the lens. The patient filled out a form informing social life and answering about the lifestyle after surgery,

Based on the patient's response, the surgeon defines the solution without

quality of life. On the other hand, when there are several alternatives for cataract surgery with an IOL implant, the choice of treatment must be given to the patient, given that it is the patient who will live with the consequences of the surgery.

It is devoid of logic for someone to seek the help of a professional to obtain a lower

sible to fuse images at near or distant focusing distances, causing a complete

the visual field perimeter for near focusing is much smaller than the visual field perimeter for distant focusing, therefore the cylindrical diopter due to the images fusion is greater for near focusing, as was verified in [11]. It should be noted that the opposite reactions in 5 cases mentioned can be explained by the probable differences in the distribution of accumulated metabolic residue as presented in [12]. It is important to consider this diopter variation when calculating the lens power for focusing at near distances. This dioptric variation is important for the forced convection mechanism in the cornea and retina, in addition to moving the trabecu-

lar meshwork, thus it is an important option to be chosen.

*The four rectangles are equal to two. Dominant left eye, greater nasal distance [10].*

without any explanation of the result of the choice:

2.Do not wear glasses neither far nor near (patient's choice).

3.It does not matter whether or not to wear glasses.

1.Do not wear glasses near.

4.Do not wear glasses away.

informing the patient of the result found.

**80**

*Lenses prescribed by doctors.*

**Figure 4.** *History of exams performed by the patient. (a) before surgery, (b) after surgery.*

**Figure 4** shows the chronology of the surgery and exams, in addition to simulated keratometry of the corneas before, **Figure 4a**, and after, **Figure 4b**, surgery. The anterior corneal surface of the left eye, after surgery, is more regular

#### **Figure 5.** *Biometry before and after surgery.*

than before the surgery and also in relation to the contralateral eye. The anterior surface of the cornea became more regular, As already explained in several studies [12, 14–16], the intraocular metabolic residue is dehydrated and stored, making a volume with high viscosity. To eliminate this viscous volume, it is necessary, first, to rehydrate it in order to reduce the viscosity and homogenize its concentration in the mobile mass, however, the only intraocular natural rehydration process available is the agitation performed through corneal flexion [14] using images fusion. In the 69-year-old patient case, the surgery made impossible for her to fuse the images, so there is no way to eliminate the metabolic residues from the cornea significantly. **Figure 5** shows the ocular biometry before and after surgery and **Figure 6** shows the specular microscopy before and after surgery, to better understand the patient's before and after operative conditions.
