Crossed and Uncrossed Diplopia

UNCROSSED diplopia:

 In convergent squint, the eyeball is rotated inward. Instead of falling on the fovea, the light from the object falls on the nasal side of the retina. Nasal side of the retina is is supposed to receive light from the temporal side of the visual field. So the image formed on the nasal side of the retina will be perceived by the brain as being on the temporal side of the visual field. So in convergent squint, instead of seeing a single image, 2 images will be seen in the temporal fields of each eye. The left eye sees the image on the left and the right eye sees the image on the right – This is UNCROSSED diplopia.

 CROSSED diplopia:

 In divergent squint, The eyeball being rotated outward, the image falls on the temporal side of the retina. Images formed on the temporal side of the retina is perceived as being from the nasal field by the brain. So the image seen by the left eye will be perceived as being on the right side and that seen by the right eye will be perceived as being on the left side – CROSSED diplopia.

 This video will make things more clear:

Credit: PGBLAZER

Comments

Post a Comment

Popular posts from this blog

Chronic Mercury Poisoning Mnemonic

Image
  " TABLE " T - Tremor (Intentional, coarse, affecting arms, hands, tongue and later legs, also called hatter's shake/glass blower's shake/danbury tremors) A - Acrodynia (Pink disease, characterised by pain, paraesthesia, pinkish discolouration of hands and feets) B - Blue-Black line on gums L - Lentis (Mercuria lentis, deposition of brown pigment on anterior lens capsule without affecting visual acuity) E - Erethism (Psychological disturbancecharacterised by shyness, timidness, loss of memory,depression, insomnia)
Read more

Localisation of Brainstem lesions : Rule of Four

Image
Ugh got destroyed by another brainstem lesion question on Qbank? Having hard time with neurology? then you are at right place.. a simplified method for answering the question ‘Where is the lesion?’   Below I have summarized RULE OF 4.  In the rule of 4 there are 4 rules: There are 4 structures in the ‘midline‘ beginning with M There are 4 structures to the ‘side‘ (lateral) beginning with S There are 4 cranial nerves below the pons, 4 in the pons and 4 above the pons. The 4 motor nuclei that are in the mid line are those that divide equally into 12 except for 1 and 2, that is 3, 4, 6 and 12 (5, 7, 9 and 11 are in the lateral brainstem).   The 4  Medial structures and the associated deficits are: M otor pathway (or corticospinal tract): CL weakness of the arm and leg   M edial Lemniscus: CL loss of vibration and proprioception in the arm and leg   M LF: IPSI inter-nuclear ophthalmoplegia (failure of adduction of the IPSI eye +nystagmus in the opposite eye as it lo
Read more

Custom Medical Dictionary for MS Office for Free

Frustrated that Microsoft Word marks difficult medical terms as mispelled? I was, but this is a simple solution I created that works well.         You get frustrated adding such underlined words every time to the inbuilt custom dictionary of Microsoft Word by right clicking and adding. To avoid such repeated annoyance, the more permanent solution would be installing a medical spell checker itself which works in the background. So here is the Solution:  "MedSpellChecker"  - a custom dictionary for medical transcription with a collection of medical words that could work in tandem with Microsoft Word. Download  "MedSpellChecker" Medical Dictionary for Microsoft Word  and follow instructions to get it working :) Windows To Add a Dictionary: 1.      Download and save the Medical Dictionary File to your desktop. o    In IE, right click on the link and click “ Save Target As ” to save the file. o    In Firefox and Chrome, right click on the link and cl
Read more