Retinitis Pigmentosa – Challenging Visual Rehabilitation

Kirti Kumari, B. Optom

Optometrist, Dr. Shroff Charity Eye Hospital, New Delhi, India

 

Retinitis Pigmentosa (RP) is an inherited degenerative eye disease that causes severe vision impairment. Symptoms often begin in childhood, including decreased vision at night or in low light and loss of peripheral vision (tunnel vision). RP is a group of diseases including Leber’s Congenital Amaurosis, Centro-peripheral Dystrophy, Usher’s syndrome.⁽¹⁾ Usually, rods and cones convert light into electrical signals that the brain interprets as vision. It is mostly diagnosed in young adulthood, but the age of onset may range from early childhood.

Figure 1:  Fundus picture of a patient with retinitis pigmentosa.
(Image courtesy : Hamel, C. (2006). Retinitis pigmentosa. Orphanet journal of rare diseases, 1(1), 1-12.)

Prevalence:

RP usually affects both eyes symmetrically. There are several forms of RP with different inheritance patterns, clinical signs, and visual symptoms. RP has a worldwide

prevalence of 1 in 4000 individuals in a diverse group of progressive retinal degenerative diseases. Most patients are inherited genetically. ⁽²⁾ Most genes causing autosomal recessive RP(AR-RP) are rare, causing 1% of all cases. Genes such as PDE6 (PDE6A, PDE6B, PDE6G), RP25, and RPE65, have higher prevalence, causing RP in approximately 2-5% of all cases. Overall, autosomal recessive RP leads to 15-20% of all cases of RP. ⁽³⁾

Challenges faced:

People with RP feel difficulty in viewing objects and performing daily living tasks such as reading, driving, walking without assistance, recognizing faces etc. due to constriction of their visual fields. People with RP have trouble in seeing lights, difficulty in perceiving colours and photophobia which leads to impaired mobility mostly during night-time. ⁽⁴⁾

Figure 2: Image illustrating tunnel vision caused by RP
(Image courtesy : https://neoretina.com/blog/retinitis-pigmentosa-symptoms-causes-and-treatment/)

Visual Rehabilitation:

Patients suffering from RP can be guided by offering low vision services, to create environmental modification according to their requirements . Low vision glasses are prescribed to enhance their residual vision. ⁽⁵⁾ To reduce glare, filters play a vital role in ornamental contrast and help patients to have clarity of surroundings. The visual discrimination is increased by various filters because of short wavelength light. ⁽⁶⁾

Low Vision Devices:

Low vision Devices are useful for RP patients by enhancing their vision and visual efficiency with the help of various devices such as:

1. Optical devices (Hand-held Magnifiers, Prismatic Spectacle Magnifiers that Increase Magnification for near tasks) 
2. Non optical devices – Reading stands and Mobility canes help patients to do Writing and reading work & travel more Safely and confidently. 
3. Electronic devices – Smart Vision glasses, Portable Video Magnifier for reading and writing difficulties. ⁽⁷⁾

Figure 3: Optical devicesFigure 4: Non optical devices

Figure 5: Electronic deviceFigure 6: Noir filters

Assistive technology:

Assistive technology enables people with RP and severe visually challenged to access technology. They are screen readers, Braille displays, speech recognition software etc.

Screen reader is a program that analyses the layout and content of a website and provides a text to speech translation. Built-in-Apple’s iOS Voiceover, Android Talkback and Kindle Text-To-Speech screen readers in Software in the form of Microsoft Narrator JAWS (Job Access With Speech) & NVDA (Non-Visual Desktop Access) are also available. Smartphones have opened new possibilities to blind users. There are many applications that help blind /severely visually challenged to recognize money, identify colours, scan barcodes, read product information, and help them navigate in new cities. ⁽⁸⁾

Conclusion:

Vision rehabilitation services allow individuals to gain greater control of their environment to those who are visually impaired, which leads to greater self-assurance, lowered risk of depression and anxiety, and an improved quality of life. Studies have demonstrated the positive effects of maximising visual function through low vision rehabilitation for patients and families dealing with vision difficulties. ⁽⁸⁾ 

Thus, being an eye care professional, optometrists should be aware of the visual rehabilitation available for patients with RP and refer to them appropriately. 

 

References:

1.  Hamel, C. (2006). Retinitis pigmentosa. Orphanet journal of rare diseases, 1(1), 1-12.
2. Verbakel, S. K., van Huet, R. A., Boon, C. J., den Hollander, A. I., Collin, R. W., Klaver, C. C., … & Klevering, B. J. (2018). Non-syndromic retinitis pigmentosa. Progress in retinal and eye research, 66, 157-186.
3. Retinitis Pigmentosa (Non-syndromic) Affiliations expand PMID: 30578498 DOI: 10.1007/978-    3-319-95046-4_25
4. Vezinaw, C. M., Fishman, G. A., & McAnany, J. J. (2020). Visual impairment in retinitis pigmentosa. Retina, 40⁽⁸⁾, 1630-1633. 
5. Weiss, N. J. (1991). Low vision management of retinitis pigmentosa. Journal of the American Optometric Association, 62(1), 42-52. 
6. Wetzel, C., Auffarth, G. U., Krastel, H., Blankenagel, A., & Alexandridis, E. (1996). Improving contrast sensitivity by cut-off filters in high adaptation luminance levels in retinitis pigmentosa. Der Ophthalmologe: Zeitschrift der Deutschen Ophthalmologischen Gesellschaft, 93(4), 456-462. 
7. Castro, C. T. M. D., Berezovsky, A., Castro, D. D. M. D., & Salomão, S. R. (2006). Visual rehabilitation in patients with retinitis pigmentosa. Arquivos Brasileiros de Oftalmologia, 69, 687-690. 
8. Irvine, D., Zemke, A., Pusateri, G., Gerlach, L., Chun, R., & Jay, W. M. (2014). Tablet and smartphone accessibility features in the low vision rehabilitation. Neuro-ophthalmology, 38(2), 53-59.