Talk:Accommodation (vertebrate eye)

message: I have taught this material to medical stduents for 30 years and I think this article will only confuse the lay person who most needs a simple, clear explanation of accommodation. Put simply, in humans, contraction of the ciliary muscle REDUCES tension on the margins of the lens allowing it to relax into a more biconvex shape changing the focal length of the lens allowing the image of the close-up object to be in focus at the level of the neural retina.  —Preceding unsigned comment added by 128.143.61.114 (talk) 21:13, 26 October 2007 (UTC)
thread_title: Simplicity is better than confusion

message: Accommodation (eye) previously redirected to Accommodation reflex. There is sufficient evidence to indicate that this article deserves to stand-alone, or even be the recipient of the redirect. First of all, given that various google searchs of "accommodation" with "lens" or "eye" reveal hits in the neighborhood of 1,200,000 to 4,250,000 whereas "accommodation reflex" gets a bit over 9,000, common usage dictates "notability" for it having its own article. Secondly, accommodation can be a voluntary process and not a reflex action. AED 08:39, 7 December 2005 (UTC)
thread_title: Recreation of this article

message: The section for Schachar seems quite biased, it reads like Schachar defending his own, questionable, hypothesis. Refer to the following papers for some decent numerical studies severely calling into question the model that Schachar based his initial claims upon:
Burd (1999): Mechanics of Accommodation of the Human Eye
Judge (2002): Modelling the Mechanics of Accommodation and Presbyopia
Burd (2002): Numerical Modelling of the Accommodating Lens.
EDIT: Sorry about the 'unsigned' just an undergraduate (not an expert) doing some related reading, seems like pretty clear bias even without expert level knowledge of the topic though.  —Preceding unsigned comment added by 58.172.106.11 (talk) 10:41, 17 May 2010 (UTC)
replies: text: +1, Schachar's content is mostly his own and from my non-expert reading seems to be a very minority view that isn't well cited.  Yes, it needs to be covered but in my view this level of detail is WP:UNDUE.   PS, 58.172.106.11, remember to add the ~~~~ :-) TerryE (talk) 01:37, 18 May 2010 (UTC)
replies: text: I have decided to remove some of the content that Schachar added: claims of falsifying the mainstream Helmholtz theory, clear self-promotion, content already covered in the presbyopia article and references to an unapproved and no widely accepted surgical procedure.  It's detail is still WP:UNDUE IMHO, but I am not sufficiently expert to précis further. -- TerryE (talk) 00:44, 20 April 2011 (UTC)

text: This 1994 article  and Schachar's book  contain accessible descriptions of Schachar's Accommodation Hypothesis.  Both include critiques of several papers supporting the Helmholtz Theory.  To date, I have been unable to find articles supporting the Helmholtz Theory that explicitly address Schachar's criticisms.  Personally, the Schachar Hypothesis seems to do a better job explaining eye strain, though I have yet to find references either pro or con.  Rcunning (talk) 02:06, 26 October 2011 (UTC)
replies: text:  I don't dispute your view, but it is just that a POV isn't it? - TerryE (talk) 17:52, 2 October 2012 (UTC)
thread_title:  Biased towards Schachar Claim 

message: (taken from the article namespace in Oct. 2015) Strasburger (talk) 17:28, 8 October 2015 (UTC)
thread_title:  Schachar's Theory 

message: The article would be greatly improved by a (possibly small) section describing the Visceromotor Nerves that innervate the Ciliary Body and effect contraction/relaxation.  While the theoretical explanations are highly valuable, the well understood Nervous aspects of Accommodation should be included (e.g. The parasympathetic nervous system innervates the ciliary body via the short ciliary fibers that arise from the ciliary ganglion and are derived from parasympathetic neurons traveling with Cranial Nerve III.)
--TwinSteel (talk) 03:23, 8 October 2010 (UTC)
thread_title:  No Mention of Nervous System 

message: I'm a layperson with respect to the scientific understanding of accommodation but wanted to note that I believe the article is of great importance (addressing the categorization of Unknown Importance - Biology). The reason is that accommodation is one of the few remaining problems to be solved in creating practical head-mounted displays. When these devices become mainstream they will have a huge impact on our society.
:I believe the problem is typically solved by using a Fresnel lens in the display. Strasburger (talk) 16:30, 8 October 2015 (UTC)
thread_title:  This article is important 

message: Convergence -- this does not help focus the image on the retina as stated in the article, it helps to center the image over the macula and fovea, the center (densest part) of the retina.  Accomodation is what focuses the image on the retina.  Convergence controls the position of the image, accomodation the focus. -- I am a practicing board certified ophthalmologist in the USA. Relopez3 (talk) 03:11, 21 September 2011 (UTC)
replies: text: You are correct, there are three main points where the rays are bent, and none of those is the one shown. However, there is a simplified model of the eye's optics known as the simplified Gullstrand eye model. In that model the three points are collapsed into one for simplicity. I forgot, though, where that point is. Strasburger (talk) 12:47, 15 January 2017 (UTC)
thread_title:  Proper role of convergence 

message: This article seems to focus on accommodation in the human eye.  However, other animals have different strategies for accommodation.  For instance, some fish accommodate by adjusting the position of the lens relative to the retina, rather than changing the lens shape.  Animals with compound eyes do not accommodate at all, as far as I know.  The article should probably touch on this sort of thing somewhere. 138.16.21.199 (talk) 20:59, 12 December 2012 (UTC)
thread_title:  Accommodation in non-human animals 

message: I'm curious about the following:
"The young human eye can change focus from distance (infinity) to 7 cm from the eye in 350 milliseconds. This dramatic change in focal power of the eye of approximately 13 diopters (diopter is the reciprocal of focal length in meters) occurs as a consequence of a reduction in zonular tension induced by ciliary muscle contraction."
How is that 13 diopters calculated? Since 7 cm is equal to .07 meters and 1/.07 = 14.3 it seems to me that the change in focal power is just over 14 diopters, and the "13" in the quoted sentence ought to be "14". Is my reasoning correct or am I missing something?
John Link (talk) 08:04, 9 February 2013 (UTC)
replies: text: Reference 3 (Chen et al., 2000, Fig. 5) reports 15 dpt, which converts to 6.7 dpt. I have put these two numbers in. Strasburger (talk) 08:08, 5 May 2015 (UTC)
thread_title:  Does changing focal distance from infinity to 7 cm imply a 13 diopter change in focal power? 

message: You can cause double vision using eyeglasses, broken ones (with temples or earpieces off) would be best for this. Put the glasses before your eyes and look at some object. If you have good vision and the lenses are +2 or +3 dioptres, the object has to be quite near for good focus. Now move one lens up and the other down by, say, 3 mm each. One image will go up and the other down. After a second your vision will align the images back. 
Now question: Is the adjustment made on "software" or "hardware" level?
--Stankot (talk) 10:39, 15 March 2016 (UTC)
thread_title:  Simple experiment