© Copyright 2018 Orlando Alves da Silva
Ophthalmic signs and symptoms
The ophthalmic signs and symptoms are of great diversity and complexity. The main optic pathways terminate in the occipital cortex; the secondary optic pathways, which are of particular interest to PDS, project to the superior colliculus and further to the mesencephalon. The oculogyric centres responsible for the main ocular movements are multiple and located in the occipital and frontal lobes, and these two structures in turn are far from the nuclei of the oculomotor muscles. It is well known that injuries in the parietal and temporal lobes can affect image perception. These structures are also connected with each other, and their complexity is very high.
Visual scotomas are evidenced through computerised campimetry (Visual Field Test), with areas of relative and absolute scotomas located para-centrally and in the periphery. The distribution of these scotomas does not correspond to any neurological condition, and it can be incorrectly interpreted as low-pressure glaucoma;
Monocular diplopia can occur with one image of the target object centred in the fovea and another image centred in an anomalous fixation point. An error of the proprioceptive information in relation to the exact position of the ocular globe relative to the target leads to a discrepancy between the objective and the subjective gaze object;
Binocular Diplopia due to reduced capacity of near fusion and loss of near ocular convergence;
Convergence insufficiency with symptoms of astenopia;
Oculomotor discoordination with the patient presenting inability to coordinate the eyes in most gaze positions, with symptoms of diplopia and incomitant ocular deviation often associated with nystagmiform movements. This situation is rare;
Near exotropia with exodeviation at near with associated diplopia, with no deviation and with single vision at distance;
Frontal lobe migraine related to convergence insufficiency;
Metatopsia with, for example, patients reporting seeing walls, floors, ceilings and pictures curved or distorted;
Sensation of ocular globe retraction;
Ophthalmic migraine due to visual misperception. This can include micropsia, visual scotomas and photopsis;
Error of spatial localisation presented as straight lines being perceived as curved, a picture hanging straight being perceived as crooked; a vertical wall being perceived as leaning; and whilst reading, lines in a text being perceived as jumping
Errors of egocentric localisation can also be present. These errors vary with the direction of gaze and include the inaccurate perception of the distance between the own body and surrounding objects, which appears to be shorter than what it is in reality, and other people may appear to be taller in relation to the than what they really are.