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physiological v anatomical Watch

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    Hi all,

    I need to understand the difference between physiological and anatomical defects of the eye.

    I am presuming that structural defects like overlong eyeballs, or a missing cornea would be anatomical, but as for physiological, I am a bit stuck, as from my point of view, 'how' something works must surely come down eventually to faulty hardware somewhere along the line?

    Would a physiological eye defect be something like the lens getting harder (presbyopia) and then not being able to focus, or cataracts, or am I barking up the wrong tree?

    Is anyone able to help, preferably with examples that demonstrate the difference between the two concepts. I just need to get my head around this.

    Thanks
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    http://rosavisionenglish.blogspot.co...a1-vision.html

    http://www.academicconcepts.net/conc...cal_defect.htm
    Hope these help you
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    Thank you Hajira,

    I took a look at these, but it's not exactly what I need. I have studied eyes and their function, so I am not having problems with this.

    What I am having an issue with, is how to distinguish between something that is a purely anatomical defect, and something that would be called a physiological defect. It is this distinction that I need to get my head around.

    I thought maybe that something like an overlong eyeball, or lack or rods and cones might be 'anatomical', whereas glaucoma, presbyopia, or cataracts might be 'physiological', but I am not 'sure', and I would like to know for certain that I have the right concept.
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    (Original post by primocat)
    Thank you Hajira,

    I took a look at these, but it's not exactly what I need. I have studied eyes and their function, so I am not having problems with this.

    What I am having an issue with, is how to distinguish between something that is a purely anatomical defect, and something that would be called a physiological defect. It is this distinction that I need to get my head around.

    I thought maybe that something like an overlong eyeball, or lack or rods and cones might be 'anatomical', whereas glaucoma, presbyopia, or cataracts might be 'physiological', but I am not 'sure', and I would like to know for certain that I have the right concept.
    Anatomical refers to anything physically wrong with the eye, physiological will refer to anything functionally wrong with the eye. The examples you gave seem pretty decent, but I would say that cataracts is probably an anatomical defect, as it's something to wrong with the lens.

    Sometimes things also get a bit tricky, cranial nerve palsy for example could probably be considered an anatomical and physiological defect
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    Hi primocat,

    In my experience, most ophthalmological or refractory defects of the eye are ones that originate as an anatomical anomaly that often results in a physiological sequela; however, the converse can encompass part of the pathophysiology e.g.

    1. As you state, in myopia (short-sightedness), the eyeball can be too long, so that the image of the object being looked at focuses in front of the retina i.e. the length of the eyeball being too long is an anatomical fault, resulting in the physiological anomaly of myopia.

    However, relative myopia/hypermetropia that fluctuates can also result in e.g. diabetes mellitus, where a biochemical/physiological defect, namely, alterations in the glucose levels in the crystalline lens that alter its refractive index and hence it's converging power, (normally around +60 dioptres), resulting in the image falling in front of the retina arising out of a physiological reason.

    2. An example of an anatomical abnormality resulting from a physiological origin occurs in age-related macular degeneration, where central (foveal) vision is deranged due to oedematous (in wet MD) or degenerative (dry MD) MD. The physiological defect I refer to is the release of vascular endothelial growth factor (VEGF) which causes the anatomical pathological feature of new vessel growth (neovascularization: neo = new - as in neoplasm = new growth = cancer); this development of opaque vessels in the retina causes visual loss as light transmission is interrupted (the anatomical defect of new vessels resulting from the physiological change of production of VEGF, in turn itself causes the physiological anomaly of reduced vision (diagnosed partly with the use of an Amsler grid, a series of parrallel lines that appear distorted to an MD patient).

    3. Glaucoma is broadly classified into acute closed angle glaucoma, and chronic open angle glaucoma, Closed angle glaucoma can be looked upon as being of anatomical aetiology since a narrow "angle" (reduced the drainage area of acqueous humour) leads to accumulation of this fluid and therefore increase in IOP (intra-ocular pressure [normally below about 20]) (a physiological phenomenon); in open angle glaucoma, the pathological factor may be a physiological one e.g. too much acqueous humour being produced due to a rise in pressure in the ciliary arteries resulting in increasing filtration and consequent over-production of acqueous humour, which tends to raise IOP = glaucoma.

    Interestingly, this (physiological) rise in IOP can result in an anatomial change, namely enlargement and deepening of the optic cupm within the optic disc, causing an abnormally large C (cup:disc) ratio, detectable on ophthalmoscopy, a potentially sight-saving diagnostic feature.

    Mukesh (ex-medic)
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    Thank you Aortastudymore and Mukesh,

    It seems there is quite a bit of overlap between physiological and anatomical. But this has helped
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    Could cataracts be considered physiological because of how they occur i.e. protein deposits into the lens as a result of lifestyle or illness (e.g. smoking, overexposure to UV, diabetes), or do you think they would definitely only be considered to be an anatomical defect?
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    (Original post by primocat)
    Could cataracts be considered physiological because of how they occur i.e. protein deposits into the lens as a result of lifestyle or illness (e.g. smoking, overexposure to UV, diabetes), or do you think they would definitely only be considered to be an anatomical defect?
    idk tbh, we've not been taught much about the eye, mukesh probably knows better than I do
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    (Original post by primocat)
    Could cataracts be considered physiological because of how they occur i.e. protein deposits into the lens as a result of lifestyle or illness (e.g. smoking, overexposure to UV, diabetes), or do you think they would definitely only be considered to be an anatomical defect?
    Hi again,

    It is gratifying to hear that an expert on the major vasculature has confidence in my meagre knowledge - in an attempt to live up to that trust, I can provide what are my views on the subject of cataract:-

    I would actually agree with you, primocat, that cataract is, broadly speaking, of physiological aetiology. The chemical changes, as you rightly point out, and which result in opacification of the crystalline lens, are physiological changes. Without making it too complicated, let me just mention that that there are a few types of cataracts, including nuclear sclerosis (where the pathogical process occurs principally in the central part of the lens [the nucleus]), which occurs mostly with increasing age, and posterior capsular cataract (the name being self-explanatory - can be secondary to corticosteroid treatment, but can also be age-related).

    I think you have actually thought of a v good example of a physiologically oriented eye condition, since most causes of cataract can be looked upon as physiological. Two biochemical causes, galactosaemia and hypocalcaemia (low Ca++ levels in the blood - normal 2.25-2.26 mM/l, according to the Guys Hospital lab), are certainly physiological, and so is the opacification associated with age, as well as that secondary to medication.

    Cataract following trauma could have, at least partly, an anatomical basis; however, now I am being pedantic .

    Well done primocat, and best wishes!
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    (Original post by macpatelgh)
    Hi again,

    It is gratifying to hear that an expert on the major vasculature has confidence in my meagre knowledge - in an attempt to live up to that trust, I can provide what are my views on the subject of cataract
    Lol you rate me too highly bro, I'm only a 20 year old medical student, it is I who has the meagre knowledge :P
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    Ooh, thank you Macpatelgh - that was very helpful.
 
 
 
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