USHER SYNDROME IN EDUCATIONAL SETTINGS:INDIGENOUS IDENTIFICATION STRATEGIES DEVELOPED IN INDIA

Abstract

most teachers of hearing and visually impaired children in India have to leam more about the prevalence and characteristics of Usher Syndrome. Keeping in mind the need to address this neglected population, the present study was designed and executed in South India. the goals of the study were to identify students with Usher Syndrome in educational settings using indigenous techniques, and to develop and describe a protocol for identifying these students. seven hundred hearing impaired students studying in residential and inclusive schools in four districts of the State Tamil Nadu were screened using tools which included screening for distance and near vision, field of vision, dark adaptation, glare and contrast sensitivity. ten students between the age of 14- 20 were found to be at risk of having Usher Syndrome. Finally, 6 subjects who had a diagnosis of retinitis pigmentosa were clinically identified with Usher Syndrome. these identification strategies will assist special education and rehabilitation professionals in recognizing symptoms of Usher Syndrome so that they will be able to refer these children for diagnostic and supportive services. [PUBLICATION ABSTRACT]

Headnote

Abstract

Introduction: most teachers of hearing and visually impaired children in India have to leam more about the prevalence and characteristics of Usher Syndrome. Keeping in mind the need to address this neglected population, the present study was designed and executed in South India.

Goals: the goals of the study were to identify students with Usher Syndrome in educational settings using indigenous techniques, and to develop and describe a protocol for identifying these students.

Methodology: seven hundred hearing impaired students studying in residential and inclusive schools in four districts of the State Tamil Nadu were screened using tools which included screening for distance and near vision, field of vision, dark adaptation, glare and contrast sensitivity.

Results: ten students between the age of 14- 20 were found to be at risk of having Usher Syndrome. Finally, 6 subjects who had a diagnosis of retinitis pigmentosa were clinically identified with Usher Syndrome.

Conclusion: these identification strategies will assist special education and rehabilitation professionals in recognizing symptoms of Usher Syndrome so that they will be able to refer these children for diagnostic and supportive services.

Keywords: Usher Syndrome, Retinitis Pigmento- sa, Deaf-hlindness, Genetic Disorder.

(ProQuest: ... denotes non-US-ASCII text omitted.)

Introduction

People who are congenitally deaf or hard of hearing may experience gradual loss of their sight in late childhood, and the combination of these two losses results in one of the most challenging disabilities for individuals: a condition called Usher Syndrome, which is the most common cause for deaf-blindness in adults (1-3).

Usher Syndrome is a genetic disorder involving both hearing loss, and retinitis pigmentosa (RP), a progressive degenerative eye disease (4-6). The loss of the ability to hear and retinitis pigmentosa are the two major criteria that characterize Usher Syndrome. Retinitis pigmentosa is an inherited disorder that results in gradual deterioration of the light receptor cells (rods) in the retina (5-7, 8). The peripheral retina is affected first. The periphe- ral retina contains the greatest concentration of rod cells (150 million), which allows a person to see in dim light. The rods are responsible for night vision, and they detect outer movement (9-18). Once the rods are affected, a person may have spotty or patchy vision (scotoma: blind spot), a ring of missing information (ring scotoma). The person may have a tunnel vision effect (outer, lower, and upper fields are decreased). The affected per- son feels as if he is seeing through a gun. Thus, retinitis pigmentosa causes night blind- ness usually with the loss of peripheral vision (19-24).

The prevalence of RP overall is about 1:4000 with the simplex subtype being the most common (25-30). While only approximately 4 in 100,000 people are diagnosed with Usher Syndrome, it is estimated that 3 to 6 percent of people who have a hereditary hearing loss have the syndrome. In developed countries such as the United States, about 4 babies in every 100,000 births have Usher Syndrome (31,32).

Signs of Usher syndrome

Although many students with Usher Syndrome may be unaware that they have a visual loss, they do realize that they have difficulties with vision that other persons do not seem to have. A common first sign of Usher Syndrome is the inability to see clearly at night. The second sign is the inability to see peripherally (above, below, and to the side) under any lighting conditions. A student with Usher Syndrome may not notice another student waving hello from the side, and obstacle on the floor etc. Another sign is difficulty in adjusting to changes in lighting: entering or leaving a building on a bright sunny day or entering / leaving a darkened room. Additional signs are problems in maintaining balance and sensitivity to glare (4-6).

Therefore, screening is only the first step in identifying Usher Syndrome. Screening is important because early identification impacts medical decisions, education decisions / services, and social implications for the student as well as the family members (33). Vision screening for retinitis pigments is not performed in a school setting in many de- veloping countries, which may result in an under-identification of students with Usher Syndrome.

Most of the teachers of the hearing and the visually impaired children in India don't have enough knowledge about the prevalence and implications of Usher Syndrome. The medical professionals have little knowledge of this disorder. There is hardly any clinical diagnosis available in the country for identification of Usher Syndrome. Keeping these factors in mind the study was planned with the following objectives:

* To identify students with Usher Syndrome in an educational setting using indigenous techniques and locally developed strategies;

* To refer at risk students for clinical assessment for diagnosis;

* To develop and describe a protocol for their identification.

Method

Area

The study was conducted in the Residential School for the deaf, the Residential School for the blind and the Inclusive Schools in Coimbatore and Salem districts of Tamil Nadu. The study sample included 5 Residential schools for the deaf, 2 Residential schools for the blind and 21 inclusive education programs for the disabled.

Sample

A total of 793 students were screened, out of which 695 students were from residential settings, and 98 from the inclusive education program. Prior to formal screening, an interview was conducted involving the class- room teachers, caretakers and peers (those who are closer to the students) to find out whether any student had any visual problem by appearance or behavior or complaints using the vision screening checklist. This type of mass screening was conducted to eliminate those with normal vision. In the Inclusive Education for the disabled, the investigators identified 12 RP students from the secondary medical data available in the school and none of them had hearing defect.

Written permission for implementation of the study was obtained from the Chief Education Officer of Coimbatore and Salem districts, and from District Disabled Welfare Officer of Coimbatore and Salem districts.

Screening tools:

Persons with Usher Syndrome experience reduced visual acuity, field restriction (34,35), lack of dark light adaptation (36-39), glare (40) and contrast sensitivity (41-42) and balance problems (43). In order to identify these major difficulties in hearing impaired children, indigenous devices and techniques have been developed in the study, as well as simple screening devices for assessment of distance and near vision and field of vision which were already tested. The screening was done to identify those individuals who were at risk for Usher Syndrome.

L Distance vision and near vision

A Tumbling E card was used to assess distance vision. Only specific levels were tested, as this was a pass/fail test for each level. Keffee (44) developed the assessment kit for measuring distance vision and field of vision for developing countries, and these tests were used in the study.

In the fraction 6/18 denoted on the card, the first number (numerator) is the distance used for testing. Usually this is 6 or 3 meters. The second number (denominator) is the size of the symbol read. The larger the second number, the larger the size of the symbol thus the worse the vision.

The size 60 and 18 are the distances in meters that the shapes can be read by a person with normal vision. The test is started with the middle level (6/18), to ensure that at least 3 out of 4 figures are correctly identified. If not, the larger letter size (6/60) is used.

If the acuity is 6/18 or better, the vision is considered within normal range. If acuity is 6/60 or 3/60, the person is categorized as having low vision. If the largest symbol cannot be recognized at 3 meters, acuity is recorded as less than 3/60 and the participant is regarded as blind according to the WHO (1992) definition (59). This test card was used to measure distan- ce vision.

A near vision chart prepared by the authors had sentences with varying print sizes. The top of the chart had larger print sizes, which was gradually reduced to the bottom of the chart. The print ranged from 20 to 6 point sizes. The near vision test is measuring the ability to read and see close up objects.

The test is administered with the person holding the chart about 35 cm (14") away. It is then noted how far down the chart he/she can read. If he/she has perfect near vision he/she can read the bottom line from arm's length and all the way, approximately 15 cm from the eyes. Those who read only 14 font sizes and above are considered as having poor near visual acuity. This near vision test is important because visual field construction affects reading rate. Reading requires visual scanning and tracking and these are affected by visual field constriction.

Near vision card

My name is Rama

My father is a carpenter

We live a village called Palayam

I go to school with my brother

My teacher is Miss Vani

There are 30 students in my class

All students wear uniform everyday

We play together during physical education session.

II. Visual field

The confrontation test was used to assess the restricted or reduced peripheral visual field of an individual. The field loss associated with retinitis pigmentosa is a progressive condition which develops slowly. The person being tested stands at 0.5 meters away from the evaluator. This simple visual field test can be done by having the student look straight ahead, watching the evaluator's eyes and asking the person to raise his/her hand when he/she sees the fingers or some bright objects like a disc in the evaluator's hand moving from the side.

If the subject fails to glance at another person's hand waving from the side, that individual is considered to have a visual field loss. The amount of the visual field loss is described as being slight, moderate or significant in right or left, upper or lower positions from the eyes. If the visual field is not intact at the periphery, students are considered at risk because the implication of RP is peripheral vision loss. If the peripheral vision is severely restricted, it is described as a significant vision loss, and if it is minimally restricted, it is considered as slight. In the test, 10 students were identified as having a peripheral vision loss and they were further assessed for their dark adaptation, glare and contrast sensitivity.

III. Dark adaptation

Retinitis pigmentosa usually begins to manifest itself as an inability to see well in dim lighting. Therefore, a dark adaptation screening is crucial.

This dark adaptation screening test was used to estimate how well the student was able to see in dim lighting. The screening was done in a dimly illuminated room. A few items were placed around the room such as chairs, table, book rack etc. The individual was asked to sit in the room for about 6 minutes to allow his/her eyes to adjust to the darkness. Then, the participant was asked to walk around the room. Observations were made if s/he bumped or stumbled into objects while walking or lost balance easily in the dark. At the same time, the students were asked to do some activities such as walking across the room and conversing with friends sitting on his/her sides or opposite him/her.

A limited light source placed in the dark room was used to observe whether the subject needed more brightness compared to normal. The dark adaptation screening included whether the individual had difficulty seeing when coming in from bright sunlight, whether he/she tripped over things when the light changed, stayed near the light in a dark room or had difficulty seeing persons sitting in the room. If the student failed in two thirds of tests, he/she failed this level of the screening. This is a simple test which does not necessarily identify that the individual has retinitis pigmentosa, but would indicate that the individual is at risk for retinitis pigmentosa.

IV. Glare sensitivity

The test was conducted to discover whether the participants had a problem in adjusting their vision when coming from bright sunlight to a darkened place. If participants exhibited clumsiness while facing a bright light, this may be interpreted as an indication of glare sensitivity. This test indicates whether they have difficulty adjusting their vision.

V. Contrast sensitivity

The contrast sensitivity was assessed by two tests

1. Low contrast letters and ditto copying - the students were asked to join/copy a low contrast dotted line to make the shape or picture and read the low contrast letter card.

If they failed to join or copy the low contrast line and needed a higher contrast line in order to be successful, this would be an indicator of the possibility for RP for which high contrast and good illumination are required.

2. Pouring liquids into a bottle with or without spilling.

The participants were seated in a dimly illuminated room to perform these tasks. The water bottle is colorless like the water. There is no distinction between these two and hence, they are considered as low contrast items. Being unable to perform the task with less contrast would be considered to be indicative of the possibility for retinitis pigmentosa. The activity was done in high illumination and dim lighting and the performances were compared in terms of spilling and quality of performing, e.g. holding of the cup, and visual behavior such as how close the eyes were to the object.

VI. Sense of balance

Balance problems were tested by asking the subject to sit in a dark place. The familiar place was modified with the placement of some furniture, things and people around him/her to find out whether s/he showed anxiety to move in the new environment. The investigators observed the student in bright and dark situations, and then observed whether he/she lost his/her balance in a dark place. Losing balance was considered as a criterion for failing.

Functional vision assessment

Functional visual skills of the students were assessed to determine how much they could use their vision for day to day activities. The assessment did not specifically screen for RP; it assessed how much individuals used their vision for visual tasks. The following areas were assessed using Keffee's (44) functional vision assessment procedure.

a. Visual tracking

The students were asked to follow a moving big object and then a small object. Then, they were asked to follow the light in a horizontal and vertical direction, and finally, to follow it in a circular pattern. The investigator was obser- ving the subject's visual behavior simu- ltaneously while rolling the ball. The criterion for failing was considered to be the subject's loss of visual contact with the moving ball. When the ball starts moving, the student may fix his/her vision on it, but once the ball is rolling, they may lose contact with it.

b. Visual scanning

The participant was asked to search for an object/picture in a group of objects using three / two dimensional objects/materials. This started with larger objects/pictures. The participant was asked to search for and describe the details of the objects/ pictures. The size of the ob- jects/pictures was gradually reduced while s/he performed the same activity.

c. Visual motor

This test was conducted to determine the student's ability to walk in a coordinated way using vision and motor inputs. The investigator asked him/her to move in a free environment, then to move in an environment with obstacles and then to move on a restricted area, e.g on bricks or on a circle.

Observations were made whether the person demonstrated visual motor coordination to maintain balance. While moving in an environ- ment, peripheral vision is used for scanning and tracking what is in the environment, enabling a coordinated gait. If the subject was unable to move in a coordinated fashion in this en- vironment, he/she were considered to have failed this assessment, and to be at risk of ha- ving RP.

Results

Result 1:

Adopted identification strategies

Figure 10 shows describes the screening for students at risk of having Usher Syndrome. This shows the stage by stage elimination of participants and at the last subjects to risk of having Usher Syndrome.

Twenty six hearing impaired students were identified with a visual disorder either with reduced visual acuity or narrowed visual field. Those 26 students were further assessed for identification of night blindness, balance problems, glare and contrast sensitivity using the developed tools.

The parents of those 26 hearing impaired students with reduced visual field and low vision were contacted in person or over the phone to give consent for the screening and assessment of their children. Comprehensive indigenous tests were administered to all the 26 students and among them, 10 students were identified to be at risk of having Usher Syndrome and they were referred for an ophthalmic evaluation for retinitis pigmentosa by the research team. From this subgroup, six students were clinically diagnosed as having Usher Syndrome.

Result 2: Consanguineous marriage between parents

JOURNAL OF SPECIAL EDUCATION AND REHABILITATION 2013; 14(3-4): 115-132

Usher Syndrome is inherited, passing from parents to their children through genes. The present study presents evidence that 90% of the students who were at risk of having Usher Syndrome had parents who were closely related. All of these parents had normal hearing and vision but, did not know if they were carriers of an Usher Syndrome gene mutation.

Result 3: Visual field

The persons with Usher Syndrome have visual problems. These children usually begin to develop vision problems by the age of ten. A number of studies using this method have determined that the half-life of visual field contraction (the time over which half of the remaining field area is lost) appears to remain remarkably constant across all types of RP at about five to eight years (44-45). Visual problems most often begin with difficulty seeing at night and tend to progress rapidly until the individual becomes completely blind. An analysis of the field restriction of 10 special cases found that 80% of them had field restriction.

Result 4: Visual acuity

Visual acuity was significantly reduced in the subjects and 50% of them were classified as 6/18, 40% as 6/36 - 6/40 in Snellen. But, the acuity and the rate vary between individuals.

Result 5: Dark adaptation

Sixty percent (6 subjects) had problems with dark adaptation. During their screening test, the participants were bumping into objects and losing their balance while walking. While the participants were asked to converse with friends sitting on their sides, some students avoided conversation in the darkened room, indicating night blindness and a risk of having retinitis pigmentosa.

Result 6: Glare sensitivity

Problems with glare are associated with retinal degenerative disease. Disappearing contours and contrast make it difficult to recognize the surroundings. In the present study, 70% of the subjects (7 cases) exhibited difficulty by squinting their eyes or shading their eyes when coming in from bright light.

Result 7: Contrast sensitivity

Contrast sensitivity functions cannot be predicted by means of other clinical measurements and hence, it was included in the screening of visual impairment due to retinitis pigmentosa. In the study, 80% of them failed the two contrast tests: 'ditto copying' and 'identification of low contrasted letters' and pouring the water in a dimly lit room.

Result 8:

Visual functional skills

In the present study, 70% showed functional difficulties in visual scanning, visual tracking and visual motor coordination. The visual contact was lost when a ball was rolled in front of the participant or when a light was shown horizontally, vertically and then in a circular pattem. In a simple visual scanning test, the participants failed to localize the objects at the periphery of the eye and they also failed to localize small objects. Sixty percent of them showed mobility difficulties when they were asked to move in a dimly lit room with obstacles, and when walking on bricks.

Ten special subjects did not pass the functional vision tests administered with the indigenous techniques and devices. At this point, the investigating team considered referring them on for medical diagnosis evaluation for retinitis pigmentosa.

Discussion

This study demonstrated that children with Usher Syndrome may be unidentified in educational settings. The authors identified six cases with Usher Syndrome in the educational setting using simple techniques.

The findings of the present study are comparable with the findings of a previous study conducted in educational and clinical settings. Besson (32) reported a loss of visual acuity between 1.0 and 8.6 percent per year in groups of people with retinitis pigmentosa. However, individual cases can vary widely. Grover & Fishman found that 52 to 55 percent of people with retinitis pigmentosa had a visual acuity of 6/12, and 20 to 25 percent of them had visual acuity of 6/60 or worse (46-48). This finding corresponds to the present finding that 50 % of subjects with retinitis pigmentosa had visual acuity of 6/18 and 40% had an acuity of 6/36 - 6/60 in Snellen.

Holopigian reported that the mean rate for loss of the visual field in retinitis pigmentosa has been estimated at between 46 percent and 13.5 percent per year (35). The rate of peripheral visual field loss is faster than that of visual acuity (34-35, 45). The present study is in line with the finding that 80% of the subjects had a restricted visual field, indicating risks of having Usher Syndrome.

Night blindness is one of the key symptoms of retinitis pigmentosa, and an expression of the loss of rod function in the peripheral retina resulting in difficulty for light and dark adaptation (36-39,46). This research reflected the finding that 60 percent of the subjects had symptoms of night blindness, had problems with light and dark adaptation and thus, placed them at risk for having Usher Syndrome.

Persons with retinitis pigmentosa have difficulty adapting to even small changes of light level. Walking from a bright sunlight into a shaded room can result in complete functional blindness. Alexandar, Fishman, Derlacki sta- ted that glare discomfort is an uncomfortable effect that occurs when a person suddenly experiences a higher level of light than the level to which the retina is adapted (45, 47). Disability glare occurs when the retinal images lose their contrast through physical factors such as reflection from shiny papers, inappropriately placed light, or intraocular light (48, 49). The present study revealed that 7 participants exhibited squinting of their eyes when coming from bright light and 80 percent failed the contrast sensitivity tests such as ditto copying and identification of low contrast letters.

This study is just a beginning. It describes a protocol for identifying children with Usher Syndrome with indigenous strategies. In developing countries like India, clinical studies are rarely carried out to identify this neglected population. We would therefore, hope that these simple locally available devices and techniques will be of help to the special educational and rehabilitation professional in recognizing cases of Usher Syndrome. It is hoped that this study will aid the future development of services for these children and the further research in educational and clinical settings.

Conflict of interests

Author declare no conflict of interest.

Acknowledgement

We would like to express our gratitude to the Chief Educational Officer of Coimbatore and Salem districts of Tamil Nadu for their permission to conduct the study in the inclusive education programmes and the District Disabled Welfare Officer of Coimbatore and Salem districts for permission for the Residential School for the Deaf and the Residential School for the Blind. We would like to thank the authorities, heads, teachers and caretakers of special schools for facilitating the conduct of this study. We gratefully acknow- ledge Dr. Srinivasan G. Rao, Consultant Ophthalmologist, Vasan Eye Care Hospital, Coimbatore for the medical diagnosis for retinitis pigmentosa. Finally many thanks to the members of the various families for their patience and persistent cooperation in this research.

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