*4.3.1 Galilean telescope*

It is made of a positive lens in the objective and with a negative lens in the eyepiece. It is an afocal optic system with visual field angle of 24° (**Figure 34**).

*Low-Vision Rehabilitation in Maculopathy DOI: http://dx.doi.org/10.5772/intechopen.92358*

**Figure 29.** *Magnifying glass neck-tight.*

**Figure 30.** *CCTV.*

**Figure 31.** *Portable CCTV.*

The use of CCTV restores reading ability and improves quality of life reducing

It is made of a positive lens in the objective and with a negative lens in the eyepiece.

It is an afocal optic system with visual field angle of 24° (**Figure 34**).

depression in low-vision patients (**Figures 30**–**33**).

**4.3 Aids for far vision: telescopes**

*4.3.1 Galilean telescope*

**Figure 26.**

**Figure 27.** *Pin-see.*

**Figure 28.** *Telemicroscope.*

**338**

*Bifocal system (writing and reading).*

*Visual Impairment and Blindness - What We Know and What We Have to Know*

**Figure 32.** *Writing with CCTV.*

**Figure 35.**

**Figure 36.**

**Figure 37.**

**341**

*Pelli-Robson contrast sensitivity test.*

*Hand Keplerian telescope.*

*Binocular Keplerian telescope.*

*Low-Vision Rehabilitation in Maculopathy DOI: http://dx.doi.org/10.5772/intechopen.92358*

**Figure 33.** *Electronic magnifier with personal computer.*

**Figure 34.** *Galilean telescope.*

*Low-Vision Rehabilitation in Maculopathy DOI: http://dx.doi.org/10.5772/intechopen.92358*

**Figure 35.** *Binocular Keplerian telescope.*

**Figure 32.** *Writing with CCTV.*

**Figure 33.**

**Figure 34.** *Galilean telescope.*

**340**

*Electronic magnifier with personal computer.*

*Visual Impairment and Blindness - What We Know and What We Have to Know*

**Figure 36.** *Hand Keplerian telescope.*


**Figure 37.** *Pelli-Robson contrast sensitivity test.*

#### *4.3.2 Keplerian telescope*

It allows greater far magnification. It is composed of two positive lenses spaced from a distance equal to the sum of the two focal lengths (**Figures 35** and **36**).

**Figure 38.** *Transmittance curves of 540–550-580 nm filter lens.*

*4.3.3 Filter lens*

**Figure 41.** *Filter lenses test.*

reflected (**Figure 38**).

**5. Conclusions**

**343**

the wavelength that passes through them.

*Low-Vision Rehabilitation in Maculopathy DOI: http://dx.doi.org/10.5772/intechopen.92358*

Low-vision patients in the most part of cases have dazzle, photophobia and a decrease in contrast sensitivity, so it is very important to evaluate the contrast sensitivity with Pelli-Robson test (**Figure 37**) and try out the filter lens starting

Transmittance is a specific and fundamental feature of a filter lens and refers to the percentage of radiation that can pass through the lens related to the wavelength: a 100% of transmittance means that all the incident radiation on the lens passes through, while a 0% transmittance means that all the radiation is absorbed or

A red-colored lens lets the red wavelength get through. Lenses have the color of

For example, a 450-nm yellow lens blocks the wavelengths below 450 nm like the UV (phototoxic) and the Blu Light (diffusion and dazzling) (**Figures 39**–**41**).

Visual rehabilitation of low vision, with its various techniques, being able to recover visual disabilities, is likely to activate neuronal plasticity, which is the ability of neurons to undergo lasting changes in the efficiency of their synaptic transmission, a concept that is owed to Donald Hebb [25] who had the intuition that if two neurons are activated at the same time, the synapses between them are

In patients with central visual field scotoma, a large part of visual cortex is not adequately stimulated and the low-vision patients must use a new eccentric fixation area on intact peripheral retina: preferred retinal locus (PRL) that functions as a pseudofovea. Functional magnetic resonance imaging (fMRI) has been used to examine whether stimulating this pseudofovea leads to increased activation or altered activation patterns in visual cortex in comparison to stimulating a comparable peripheral area in the opposite hemifield (opposite PRL) [26]. The PRL and OppPRL were stimulated with flickering checkerboard stimuli and object pictures during fMRI measurement and the result shows that stimulation with pictures of everyday objects led to overall larger BOLD (blood oxygen level dependent) responses in V1 visual cortex compared to that evoked by stimulation with

from 400 nm with different grade of polarization [22–24].

strengthened: "Neurons that fire together wire together."

Filter lenses stop some wavelengths and some other get through.

**Figure 39.** *511-nm filter lenses.*

**Figure 40.** *550-nm filter lenses.*

*Low-Vision Rehabilitation in Maculopathy DOI: http://dx.doi.org/10.5772/intechopen.92358*

**Figure 41.** *Filter lenses test.*

*4.3.2 Keplerian telescope*

**Figure 38.**

**Figure 39.** *511-nm filter lenses.*

**Figure 40.** *550-nm filter lenses.*

**342**

*Transmittance curves of 540–550-580 nm filter lens.*

It allows greater far magnification. It is composed of two positive lenses spaced

from a distance equal to the sum of the two focal lengths (**Figures 35** and **36**).

*Visual Impairment and Blindness - What We Know and What We Have to Know*

#### *4.3.3 Filter lens*

Low-vision patients in the most part of cases have dazzle, photophobia and a decrease in contrast sensitivity, so it is very important to evaluate the contrast sensitivity with Pelli-Robson test (**Figure 37**) and try out the filter lens starting from 400 nm with different grade of polarization [22–24].

Transmittance is a specific and fundamental feature of a filter lens and refers to the percentage of radiation that can pass through the lens related to the wavelength: a 100% of transmittance means that all the incident radiation on the lens passes through, while a 0% transmittance means that all the radiation is absorbed or reflected (**Figure 38**).

Filter lenses stop some wavelengths and some other get through.

A red-colored lens lets the red wavelength get through. Lenses have the color of the wavelength that passes through them.

For example, a 450-nm yellow lens blocks the wavelengths below 450 nm like the UV (phototoxic) and the Blu Light (diffusion and dazzling) (**Figures 39**–**41**).

#### **5. Conclusions**

Visual rehabilitation of low vision, with its various techniques, being able to recover visual disabilities, is likely to activate neuronal plasticity, which is the ability of neurons to undergo lasting changes in the efficiency of their synaptic transmission, a concept that is owed to Donald Hebb [25] who had the intuition that if two neurons are activated at the same time, the synapses between them are strengthened: "Neurons that fire together wire together."

In patients with central visual field scotoma, a large part of visual cortex is not adequately stimulated and the low-vision patients must use a new eccentric fixation area on intact peripheral retina: preferred retinal locus (PRL) that functions as a pseudofovea. Functional magnetic resonance imaging (fMRI) has been used to examine whether stimulating this pseudofovea leads to increased activation or altered activation patterns in visual cortex in comparison to stimulating a comparable peripheral area in the opposite hemifield (opposite PRL) [26]. The PRL and OppPRL were stimulated with flickering checkerboard stimuli and object pictures during fMRI measurement and the result shows that stimulation with pictures of everyday objects led to overall larger BOLD (blood oxygen level dependent) responses in V1 visual cortex compared to that evoked by stimulation with

flickering checkerboards. BOLD responses to stimulation of the PRL with object pictures were significantly enhanced in comparison to stimulation of the OppPRL area, and a stable eccentric fixation with the PRL was associated with a higher BOLD signal in visual cortex.

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*Low-Vision Rehabilitation in Maculopathy DOI: http://dx.doi.org/10.5772/intechopen.92358*

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The first step in low-vision rehabilitation in maculopathy is to find the preferential retinal locus (PRL) with microperimetry, stabilize the PRL and, if necessary, shift PRL to a better area useful in reading, using audiobiofeedback. Then, with neurovision training (NVT) and perceptual learning, we can increase the neuronal wire and further improve the visual quality, the contrast sensitivity and the VA.

After these neurovisual rehabilitations, we must consider visual aids for all the visual activity requests from the patient: reading, writing, watching TV, walking, the possibility of orientation and movement, manual work, daily activity like cooking and moving in the house.

The low-vision patient is a person and we must consider all his appearances: visual, physical, psychological and social life [27–30].

## **Author details**

Giovanni Sato\* and Roberta Rizzo Low Vision Rehabilitation Center, Padova, Italy

\*Address all correspondence to: giovanni.sato@aopd.veneto.it

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Low-Vision Rehabilitation in Maculopathy DOI: http://dx.doi.org/10.5772/intechopen.92358*
