A Christmas tree in the eye

Posted: Tuesday, December 21, 2010 | Posted by Debajyoti Datta | Labels: ,

Medicine never ceases to amaze.  I just read a case report published in the BMJ by Ebube E Obi and C Weir about a Christmas tree cataract. I have seen some cases of cataract but I have not seen a Christmas tree cataract. May be sometime in future I will.


They report a case of a 73 year old woman who presented with a Christmas tree cataract of the left eye. The Christmas tree cataract was highly reflective, iridescent and polychromatic. They look like little needles in the eye going in all directions and assume the shape of a Christmas tree. The needles change color when the angle of the incident light is changed. The woman was referred to them for cataract surgery.

A Christmas tree cataract. From BMJ. 
Any opacity in the lens of the eye is called a cataract. Senile cataract is the commonest type though there are many other types. Usually it is accompanied by progressive impairment of vision but in Christmas tree cataract the vision may be 6/6 which is normal. In a Christmas tree cataract, the adjacent areas of the lens remain clear.

GA Shun-Shin et al. had examined the morphological and chemical composition of Christmas tree cataracts. They had examined four Christmas tree cataracts that were extracted and eight Christmas tree cataracts from donor eyes by scanning and transmission electron microscopy. Chemical composition was analyzed by energy dispersive x-ray microanalysis and Raman microspectroscopy.

Electron microscopy showed that Christmas tree cataracts were made up of rectilinear crystal like structures traversing the eye in all directions. The crystalline structures consisted of varying number of plate like elements stacked up together having a periodicity of about 5 nm. It has been suggested that the origin of these structures lie in the reticular meshwork. With increasing age there is degradation of the peptides and amino acids within the lens by endopeptidases. There is an increase in calcium ions and this local increase in calcium ions stimulates the endopeptidases resulting in protein breakdown. The breakdown products are subsequently deposited in the lumen of the reticular meshwork forming the Christmas tree cataract. Radiographic microanalysis showed the presence of sulfur in the crystals of the Christmas tree cataract. Raman microspectroanalysis showed increased CS-SC and S-S vibrations. The crystals are thus taken to be made of cystine (an amino acid). Accumulation of cystine beyond the point of crystallization causes the formation of needles that gives the fascinating appearance of the Christmas tree in the eye.

Reference:

ResearchBlogging.org
Obi, E., & Weir, C. (2010). A Christmas tree cataract BMJ, 341 (dec08 3) DOI: 10.1136/bmj.c6644

ResearchBlogging.org
Shun-Shin GA, Vrensen GF, Brown NP, Willekens B, Smeets MH, & Bron AJ (1993). Morphologic characteristics and chemical composition of Christmas tree cataract. Investigative ophthalmology & visual science, 34 (13), 3489-96 PMID: 8258504

5 comments:

  1. Felix said...
  2. Is this hereditary?
    http://www.herpessymtomsinwomen.net/

  3. Debajyoti Datta said...
  4. A Christmas tree cataract is not hereditary.

  5. Anonymous said...
  6. A Christmas tree Cataract may or may not be hereditary. They may happen idiopathically or associated with myotonic dystrophy

  7. jowdjbrown said...
  8. I have seen some cases of cataract but I have not seen a Christmas tree cataract. May be sometime in future I will.Armodafinil online

  9. Robert F. Crocker said...
  10. Shun-Shin GA, Vrensen GF, Brown NP, Willekens B, Smeets MH, & Bron AJ (1993). Morphologic characteristics and chemical composition of Christmas tree cataract modvigil

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