Visual CDs are not a disease of exclusion, rather it is a condition that must be proved not to be caused by organic disease. The ages involved range from 6–16, with 10 being the most common age of presentation. The condition is rare in those younger than six and affects genders equally up until 10 years of age, when it then moves rapidly to a fale:male ratio of 3:1.A family history of illness or eye disease such as RP is possible, but the symptoms reported have a gradual onset. Subsequent examinations show varying levels of VA and visual field loss.Significantly, although the condition is usually bilateral and worsens over time, it is rare that the child becomes blind bilaterally. Also, even though both fields and VA are affected in children, any adult case is more likely to be monosymptomatic. While tunnel vision is common, a central scotoma is rare.The most common complaint is, “I’m just not seeing”, or “My vision is blurred/distorted/things look small”. Occasionally, other manifestations occur, such as spasm of near reflex, headaches, voluntary nystagmus, tics of eye movents, eye deviations, and paralysis of accommodation.Tellingly, cases often have equal difficulty with both large and small letters, and tend to read down the chart slowly. Often, near charts are read excruciatingly slowly, far slower than their performance on a distance chart would suggest.It is worth exploring the backgrounds of the home and the family unit, paying particular attention to evidence of conflict, rivalry, marriage stability, sexual abuse, overcrowding, or harassment by relatives, neighbours, or other children.{{quote-A:R-W:450-Q: As treatment is best achieved with parental help, they should be told explicitly about possible underlying issues. }}It is equally important to seek information relating to school and whether or not the child is being over or under stretched relative to their ability, has aggressive or unsympathetic teachers, is being teased or bullied, suffering from sexual or non-sexual harassment, or if there is evidence of abuse.As treatment is best achieved with parental help, they should be told explicitly about possible underlying issues. It is known that some children develop somatic probls in response to depression. While no ocular disease is expt, misdiagnosis with macular disease and hereditary optic atrophy are more likely.Bilateral total blindness is easiest to disprove by using a tethered ball thrown straight at the patient’s face, or a poking or punching action directed to their face (without disturbing the air excessively).If they blink, some vision has to be assumed. Other blindness tests include superimposing a prism (BI or BO) and watching for compensating eye movent – which implies an attpt to avoid diplopia – and optico-kinetic nystagmus induction.If unilateral blindness is reported, use of a trial frame or refractor head to occlude the ‘blind’ eye will usually suffice. A Worth 4-dot test, a polarised random-dot stereogram, or a pupil reflex assessment might also be able to donstrate vision function beyond that claimed.When VA varies greatly despite subtending similar angles at different distance, the likelihood of a visual CD is high. In unilateral cases, pupil reactions are rarely useful and it is difficult to inter-relate VA and stereo acuity.In children, peripheral vision/visual field defects are uncommon in isolation. If tunnel vision is reported, it is usually of a gross nature bearing a few degrees from the fixation point. Tellingly, the apparent size varies little with screen distance.Hifield defects are reported rarely. Often the field size becomes smaller with successive testing and if the target is moved around an imaginary clock face, a contracting spiral effect is found. However, as that is also possible in organic disease, some caution was advised.Unfortunately for the examiner, it is possible to over-investigate and make a diagnosis too late to the extent that the child can become stressed further, thereby reinforcing the underlying probl. That is when electrophysiology comes into its own and also helps diagnose the most common missed condition, i.e. Stargardt’s disease.CT scans or MRI imaging are not risk-free, especially if an anaesthetic is required, and are only appropriate if neurophysiological tests are abnormal or all other avenues have been exhausted and doubt still rains in the practitioner’s mind.If a cause is identified, appropriate and sensitive modifications of th will usually abolish the symptoms. Jones advised strongly that both the child and parents be involved in a full discussion about the condition in a language and at a level appropriate to both.Most cases only require the ophthalmologist and generally, the fewer professionals involved the better. At no time should a sense of having ‘wasted the doctor’s time’ be conveyed to any party. The prognosis in such cases is good and strong reassurance with minimal follow-up is usually indicated, but an underlying psychiatric disorder requires a referral to a psychiatrist.Instead of calling the patient a liar or similar, comments like, “My results are really inconsistent, there is something going on here” is preferred. Jones’ parting comment was to offer the patient ‘an honourable way out’ so that they can save face.
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Dr Mike Jones is the Head of the Department of Ophthalmology at the Children’s Hospital at Westmead, consultant in the Strabismus Unit at the Sydney Eye Hospital and a Senior Clinical Lecturer with the University of Sydney. He has a keen interest in teaching and research, and completed his PhD in mitochondrial DNA and age-related maculopathy at the University of Sydney. |
