What does vision loss look like in Bardet-Biedl syndrome?

Rod-cone dystrophy, from night blindness to a small island of sight. In the words of people who live with it, with the frames from our simulator and the sources behind every statement.

Medically reviewed by Stephen Johnston, MD. Reviewed 2026-10-23.

The short answer

Rod-cone dystrophy is the pattern behind retinitis pigmentosa and the eye disease of Bardet-Biedl syndrome: the rods fail first, so the dark and the sides go, then the cones follow, so the center blurs and colors fade. To the child it looks like this in order: a normal daytime world and a difficult night; then things that are not there at the sides, without any sense of a missing piece; then a small, clear island that slowly becomes smaller and softer. Even at the end, most people still see light. Where the pattern comes from a syndrome, it tends to move faster.

What the person is experiencing

Night blindness comes first, usually bringing a child to medical attention in the first decade of life, followed by progressive loss of side vision, fading color discrimination and then loss of sharpness. In Bardet-Biedl syndrome retinal dystrophy affects 94% of people, and many are legally blind by the second to third decade. In non-syndromic RP the timeline is usually slower: many people keep good central vision into their 40s or 50s. Even at the end stage, total loss of vision is uncommon; most people retain some light perception.

The ring of blind spots in the mid-periphery, 20 to 25 degrees out, widens outward and inward over time; islands of vision may persist for years in the far periphery, and "long after the entire peripheral field is gone, a small oval of intact central field typically remains". Because side-vision loss is "rarely recognized by the affected individual", children may be thought clumsy before anyone measures the field.

In their words

The accounts on our RP page apply here, because the pattern is the same. Laura Lawson Visconti, with about 24 degrees of field: "I scan a lot and my brain fills in the information that my eyes miss"; the lost periphery is not black, "I simply do not see anything". Dave Steele on what the tunnel feels like: "It's like a tunnel closing inwards, then you start to lose your central". Hannah, whose cone-rod dystrophy later took her sides, on the brain's cover-up: "your brain does a really great thing where it like makes up everything you can't see".

For the late stage, Hannah describes her field now as "about a pinhole of vision in my left eye" and the loss as "mostly dark. It was mostly like nothing". Helene Lonborg-Moller describes the course of her Usher syndrome as "gradual, changing and progressive. What I could do one year, I could not do the next, loss followed upon loss".

"It's like a tunnel closing inwards, then you start to lose your central." Dave Steele on what the tunnel feels like, Hadley.

Why it moves faster in a syndrome

In Bardet-Biedl syndrome the retinal disease is one part of a condition that also involves weight, kidneys, hormones and development, and it tends to reach legal blindness in the teens or twenties rather than in middle age. This is why early educational planning is recommended: braille, mobility training, adaptive living skills and computer skills including voice recognition, while making the most of large print while vision remains.

What our simulation shows

For the earlier stages, see the RP frames, which share the same model.

Late: A small central island of about 12 degrees with reduced sharpness and color, surrounded by a dim, featureless absence rather than black, and a faint crescent flash of the kind 93% of people with RP report.

End stage: The last stage: a tiny, blurred island in a dark field, with light still perceived but almost no detail.

Signs you might notice in a child

Fear or hesitation at dusk, asking for lights, reverting to crawling after dark.

Bumping into things, missing balls, tripping over low objects, being called clumsy.

Later, holding things close, sitting near the board, and difficulty with colors as the cones become involved.

In Bardet-Biedl syndrome, the eye signs usually arrive alongside the other features of the syndrome, and the ERG is more likely to show significant findings after age five.

Common questions

Will he be totally blind?

Complete blindness is uncommon; most people keep light perception, and in a large study of adults with RP or Usher syndrome aged 45 and over, only 0.5% were completely blind in both eyes.

Is the lost area black?

Usually described as absence, not darkness; some people do say black, particularly when they discover a lost area for the first time.

What helps right now?

Lighting, clear floors, sunglasses and a hat, early low-vision and mobility support, and in syndromic forms coordinated care across specialists. A confirmed genetic diagnosis connects the family to trials relevant to their gene.

References

Sources were read on Oct 22-23, 2026.

1. Forsyth RL, Gunay-Aygun M. Bardet-Biedl Syndrome Overview. In: GeneReviews [Internet]. University of Washington, Seattle; 2003, updated 2023. https://www.ncbi.nlm.nih.gov/books/NBK1363/

2. O'Neal TB, Tripathy K, Luther EE. Retinitis Pigmentosa. In: StatPearls [Internet]. StatPearls Publishing; 2024. https://www.ncbi.nlm.nih.gov/books/NBK519518/

3. GeneReviews [Internet]. Nonsyndromic Retinitis Pigmentosa Overview. University of Washington, Seattle. https://www.ncbi.nlm.nih.gov/books/NBK1417/

4. Lawson Visconti L. Going blind in a sighted world (personal blog; first-person account of retinitis pigmentosa). http://lauralawsonvisconti.com/blog/rp

5. Hadley. Hadley Presents: The Blind Poet, Dave Steele (podcast transcript; Dave Steele describing retinitis pigmentosa). https://hadleyhelps.org/podcasts/hadley-presents/blind-poet-dave-steele

6. Pediatric Retinal Research Foundation. Living with Cone Dystrophy: Hannah's Therapeutic Humor (podcast transcript; first-person account). https://prrf.org/living-with-cone-dystrophy/

7. Living with Usher Syndrome: Patient and Physician Perspectives (commentary co-authored by patient Helene Lonborg-Moller with ophthalmologists Yousif Subhi and Line Kessel). 2020. PMC7406578. https://pmc.ncbi.nlm.nih.gov/articles/PMC7406578/

8. A Race Against Blindness. How our vision simulations were built: research basis and rendering conventions (Education Hub, Oct 2026). https://araceagainstblindness.org/education/vision-simulations/methodology

9. Bittner AK, Diener-West M, Dagnelie G. A survey of photopsias in self-reported retinitis pigmentosa: location of photopsias is related to disease severity. Retina. 2009;29(10):1513-1521. doi:10.1097/IAE.0b013e3181af0d57 https://pmc.ncbi.nlm.nih.gov/articles/PMC2783747/

10. Hesperian Health Guides. Disabled Village Children: Causes of Loss of Vision. https://en.hesperian.org/hhg/Disabled_Village_Children:Causes_of_Blindness

11. Nemours KidsHealth. Retinitis Pigmentosa (for Parents). https://kidshealth.org/en/parents/retinitis-pigmentosa.html

12. Raising Children Network (Australia). Low vision and blindness: babies, children and teenagers. https://raisingchildren.net.au/disability/guide-to-disabilities/assessment-diagnosis/low-vision-blindness-babies-children-teens

13. American Academy of Ophthalmology, EyeWiki. Retinitis Pigmentosa. https://eyewiki.aao.org/Retinitis_Pigmentosa

14. Gene Vision (UK). Retinitis pigmentosa: for patients. https://gene.vision/knowledge-base/retinitis-pigmentosa-for-patients/