Clinical Low Vision EvaluationBy: Carmen Willings
teachingvisuallyimpaired.com Updated May 25, 2019 The results of the Functional Vision Evaluation may indicate there is a need for a Clinical Low Vision Evaluation. The Clinical Low Vision Evaluation differs from the medical examination from an optometrist or ophthalmologist in that it provides functional, usable information about the visual abilities of an individual who has low vision. The evaluation focuses on verifying the student's visual acuity and on finding ways to enhance the students visual functioning. A combination of the Functional Vision Evaluation and Reading Media Assessment will determine if the student’s primary mode is print. A low vision evaluation will further determine if optical aids will provide the student with low vision devices to access print. If devices are recommended, the TVI will need to instruct the student in the use of low vision devices.
Although there are certain components in all low vision evaluations, the focus will depend upon the concerns of the student, family and teachers. The individual who conducts the evaluation is the Low Vision Specialist but others may be involved in the entire visit. The Low Vision specialist will seek to identify optical and non-optical tools that will increase the student's ease of completing near and distance tasks. The evaluation can provide information that is critical to the kind of educational programming that is needed by students who have low vision. The information from the Clinical Low Vision Evaluation paired with the Functional Vision Evaluation and the Reading/Learning Media Assessment will provide the team with information that can assist in the students overall literacy program. The following are the areas and procedures carried out during the evaluation. Case History
The Specialist will want to know the students medical history and information from the most recent ophthalmological exam. The family will be asked about the onset of the visual impairment, eye surgeries and dates, current treatments and medications and about the students general health. The specialist will also ask about the student's independent functioning at home, in the school and in the community. Ocular Health The specialist will assess the general condition of the structures of the eyes in order to determine the nature and extent of the visual diagnosis. The specialist may be able to better explain the visual impairment to the family. Visual Acuity The specialist will assess the students visual acuities both with and without correction. Each eye will be assessed separately and then together. Both distance and near visual acuities will be assessed. Visual Fields The specialist will assess the central and peripheral visual fields. There are a variety of tools to assess the students fields. These tests can also be used to assist in diagnosing the disease process in some visual impairments. Color Vision The students color vision will be assessed. This will provide useful information regarding the student's contrast abilities. Refraction & Conventional Lenses The specialist will test for refraction to determine if correction can be further corrected. Contact lenses may be recommended as they can sometimes improve the acuities of some students with irregular cornea surfaces or with high refractive errors. Binocular Vision & Oculomotor Skills The specialist can determine the potential for sustaining binocularity (use of both eyes). The results will have an impact on the prescription of the low vision device and training. Fixation, scanning and tracking may also be assessed as well as their head position and visual motor abilities. Contrast Sensitivity, Light Sensitivity, and Illumination Needs Assessment of contrast sensitivity will provide information on the degree of loss of the ability to detect materials when they are presented on low contrasting backgrounds. If the student performs poorly, more attention will be given to issues of lighting, contrast and glare. Possible Questions to AskIf you are unsure of any of the following, be sure to ask the low vision specialists:
RecommendationsAt the completion of the visit, recommendations for low vision devices are typically made. Some clinics may provide low vision devices for the students to borrow. The students will typically be encouraged to use the devices for a period of time and return for a follow-up appointment where the results can be reviewed.
Low Vision Devices The specialist will select possible low vision devices for a student based on the goals of the student along with the acuity outcomes. The specialist may prescribe devices for near, intermediate, and distance activities. |
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Guide to Selecting Optical Aids by the New York Lighthouse
Each symbol used in its Code relates the visual acuity range to the number of Diopters needed to read average print (8pt to 12pt)
Vision |
Lighthouse Code |
Diopters |
Magnification |
Focal Length |
20/40-20/60 |
A |
3-6 D |
Up to 1.5X |
12-6 inches |
20/70- 20/100 |
B |
7-10 D |
1.75X - 2.50X |
6-4 inches |
20/100- 20/200 |
C |
10-20 D |
2.5X - 4X |
4 - 2.5 inches |
20/200- 20/400 |
D |
20-40 D |
5X - 8X |
2.5 - 1 inches |
below 20/400 |
E |
40-80 D |
10X - 20X |
0.5 inch or less |
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