Amblyopia

 

AMBLYOPIA

The failure of experiments on cats and monkeys

 

Some of the most high profile animal research in this area has been by Colin Blakemore, a high profile defender of animal testing.  Blakemore’s research has been into amblyopia and strabismus.  Amblyopia is decrease in function of one or both eyes, or impairment in the way in which the eyes interact, for which no cause can be detected in the eyes.  Strabismus is misalignment of the eyes, and can take the form of a squint.


Treatments and how they were discovered

In the 1800s Claud Worth identified that is was the deficiency in eye function which caused the misalignment, or squint.[3] George Louis Leclerc Comte de Buffon also proved this; who did his research in the 1700s.[4]

 

The recognised pioneer in amblyopia treatment is Claude Worth, who retired 50 years before Blakemore started his experiments. [5]


Species differences

 “Human amblyopia involves primarily foveal vision rather than peripheral vision...".[7] (von Noorden)

 The neuroanatomy of the cat and human are different, highlighted by the lack of references in clinical research literature to neuroanatomical research in the cat.[8]

Animal experimenter Jampolsky has also noted that common forms of strabismus in humans are rarely, if ever, found naturally in monkeys.  Aspects of the human condition include exotropia, accommodative esotropia, A and V patterns, dissociated vertical deviation and latent nystagmus. These are not features of induced and occurring money strabismus. [10]



Inducing the fake condition

In humans born with amblyopia, there are often complications caused by other abnormalities, which doesn’t apply to animals.  The animal work revolves around taking recordings from single cells, yet in humans vision has a high psychological element – a problem animal experimenters have admitted.[12] Cell recordings don’t tell us what animals can see, or whether they see at all. 

 

Sewing the eyelid shut differs from human blindness such as that caused by cataracts in the amount and quality of light reaching the retina. 

 

Primate experimenters have concluded that the artificial way of inducing the condition is a cause of differing results.[13]


Misleading

“There has been considerable concern expressed by vision scientists other than just myself that the experimental work is either not relevant or may be misleading with respect to the human condition and its treatment.”[14] 

 

Primate experiments have misled us over the critical time at which amblyopia develops.[15]

 

A researcher expressed his hesitance to accept animal results, concluding “the morphologic and functional organization of the visual system in cats is substantially different from that in man.” [16]

 

Monkey experiments suggested that children wearing eye patches might be harmful. Studies on children showed this was not the case.  A researcher involved described this as a “surprise” and suggested that we should ask whether to believe animal results.[18]

 
A similar conclusion came from cat experiments.


Instead of vivisection

Technology now enables us to gain information by using non-invasive imaging technologies on patients.

All advances have come from clinical study.

For example, modern magnetic resonance imaging technologies can assess visual cortex function with a resolution of 1.4 mm. [20]

CAT scans, PET scans, and autopsy studies enable a more complete picture to be built up.  The findings will be based on human neurology, as opposed to the very different neurology of an animal.

Resources available to study these proven and emerging, reliable techniques will be increased once the unscientific pre-occupation with animal experiments is abandoned. 


Other illnesses have been the subject of high profile claims in favour of animal testing.  Read the reality here.

References

 

1 Colin Blakemore "A reply to criticism of experiments involving visual deprivation," September 1987.

2 Colin Blakemore "A reply to criticism of experiments involving visual deprivation," September 1987.

3 Abraham, S.V.: A tribute to Claud Worth. Ann. Ophthalmol. 4: 171-175, 1972.

4 Marg, E.: Prentice Memorial Lecture: Is the animal model for stimulus deprivation amblyopia in children valid or useful? Am. J. Optometry Physiol. Optics 59: 451-464, 1982.

5 Abraham, S.V.: A tribute to Claud Worth. An n. Ophthalmol. 4: 171-175, 1972.

6 von Noorden, G .K.: Application of basic research data to clinical amblyopia. Ophthalmology 85: 496-504, 1978.

7 von Noorden, G .K.: Application of basic research data to clinical amblyopia. Ophthalmology 85: 496-504, 1978.

8 “AMBLYOPIA” Nedim C. Buyukmihci, V.M.D.a, http://avar.org/

9 Raviola E, Wiesel TN. An animal model of myopia. New England Journal of Medicine 1985;312: 1609-1615.

10 Jampolsky A. Unequal visual inputs and strabismus management: a comparison of human and animal strabismus, in Transactions of the New Orleans Academy of Ophthalmology, Symposium on Strabismus. St. Louis, CV Mosby, 1978, p 358-492

11 Robinson CJ. Somatopographic organization in the second somatosensory area of M. fascicularis. Journal of Neumphysiology 1980; 192:43-67.

12 Blakemore, C . and Vital-Durance, F.: Development of the neural basis of visual acuity in monkeys: Speculation on the origin of deprivation amblyopia. Trans. Ophthalmol. Soc. U.K. 99: 363-368, 1979.

13 O'Dell CD, Gammon JA, Fernandes A, Wilson JR, Booth RG. Development of acuity in a primate model of human infant unilateral aphakia. Investigative Ophthalmology and Visual Science l989;30:2068-2074. Wilson JR, Tigges M, Booth RG, Tigges J, Gammon JA. Effects of aphakia on the geniculostriate system of infant rhesus monkeys. Acta Anatomica 1991; 142:193-203.

14  “AMBLYOPIA” Nedim C. Buyukmihci, V.M.D.a, http://avar.org/

15 Vaegan TD. Critical period for deprivation amblyopia in children. Transaction of the Ophthalmological Society of the United Kingdom 1979;99:432-439

16 von Noorden, G .K. and Maumenee, A .E.: Clinic al observations on stimulus- deprivation amblyopia (amblyopia ex anopsia). Am. J. Ophthalmol. 65: 220-224, 1968.

17 Boothe RG, Quick MW, Joosse MV, Abbas MA, Anderson DC. Accessory lateral rectus orbital geometry in normal and naturally strabismic monkeys. Investigative Ophthalmology and Visual Science 1990;31:1168-1174.

18 Marg, E.: Prentice Memorial Lecture: Is the animal model for stimulus deprivation amblyopia in children valid or useful? Am. J. Optometry Physiol. Optics 59: 451-464, 1982. Hoyt, C.S .: The long- term visual effects of short-term binocular occlusion of at-risk neonates. Arch . Ophthalmol. 98: 1967-1970, 1980.

19 Metz, Henry S.: To the editor. Invest. Ophthalmol. Vis . Sci. 26: 249, 1985

20 Engel SE, Rumelhart DE, Wandell BA, et al. fMRI of human visual cortex. Nature 1994:369;525,