Photochromic lenses ... should not be worn for lookout duties at night

[Nikolay Angelov]

An maritime accident with the yacht Ouzo (in which all three crew members died) prompted an investigation by the United Kingdom's Marine Accident Investigation Branch.

After the investigation concluded this marine guidance note was circulated:

MGN 357 (M+ F): NIGHT-TIME LOOKOUT – PHOTOCHROMIC LENSES AND DARK ADAPTATION
http://www.dft.gov.uk/mca/357_a.pdf

3. Photochromic lenses

3.1 Photochromic lenses, even after being in the dark for an extended period and in their most translucent state, can reduce night vision significantly. They should not be worn for lookout duties at night.

3.2 The MCA’s approved doctors have also been asked to issue this advice to any seafarers they examine who wear glasses with photochromic lenses.

Here is the report on the investigation of the Ouzo:
http://www.maib.gov.uk/cms_resources...ile=/Ouzo_.pdf

It has a lot more information of the photochromic lenses and night adaptation.

The glasses (from the investigation) were sent to the Institute of Ophthalmology, UCL, London where an expert investigation was done.

Here are the reports submitted as Annex 1 and 2 in this PDF file:
http://www.maib.gov.uk/cms_resources...zo_Annexes.pdf

Report from the Institute of Ophthalmology, UCL, London:
"Spectral and temporal characterisation of Photochromic eyewear"

Report from the Institute of Ophthalmology, UCL, London:
"Report on the potential reduction in visual acuity resulting from photochromic glasses"



On a related note the Federal Aviation Administration has made this pilot safety brochure:

Sunglasses for Pilots: Beyond the IMAGE
http://www.faa.gov/pilots/safety/pil...sunglasses.pdf

PHOTOCHROMIC
... In addition, the faded state of photochromic glass lenses may not be clear enough to be
useful when flying in cloud cover or at night.

I hope someone finds the information useful.

PS: It would be interesting to translate these findings in other critical night vision activities such as driving.

Best regards,
Nikolay Angelov