Dr. Fawaz Al-Sarayreh and Dr. Khalil Al-Salem’s lecture is a targeted lecture for medical students. To understand strabismus and amblyopia easier than ever, we request only a few squint problems to know, commonly seen in the ophthalmology clinic.
Strabismus by Dr. Fawaz Al-Sarayreh
Comments on strabismus by Khalil Al-Salem M.D FRCS, FICO
Strabismus is a problem seen in 5% of the eye clinic patients. Because of the high frequency, careful assessment and good knowledge of the caregiver is mandatory.
Important definitions before coming to the ophthalmology clinic:
- Comitant squint: a squint with an equal amount of deviation while doing cover uncover test. Ex. when covering the right eye, you discover a 20 prism diopter of esodeviation. Suppose you repeat the test while covering the left eye. Both angles will be equal.
- non-comitant squint: a squint with an unequal amount of deviation when measuring the deviation using cover uncover test. Example Covering the right eye (20 PD ) and covering the left eye 40 PD.
- tropia: manifest squint
- Phoria: hidden squint
- Esotropia /esophoria: towards the nose. the eyes are going inside.
- Exodeviation: away from the nose
- hypertropia: the eye is deviating upwards
How to examine a patient with strabismus:
Examples of common types of squint:
- Intermittent exotropia: This type of squint usually starts late in life, after 4 or 6 years. Both eyes have normal vision or slightly myopic. Most of the time, the patient is not complaining of any problem. The parents usually are not happy about a momentary eye movement to the outside. That is frequently corrected when the patient is asked to concentrate.
- the patient can be classified as having
- good control: rarely the patient has exo-deviation (seen in visual inattention periods or when the patient is tired or sick
- Fair control: when the patient has the problem being manifested 2-5 times a day.
- Poor control: The patients’ eyes are seen most of the day outwards.
When to treat:
- Usually patients with good control are given corrective glasses or slightly myopic correction like an extra -1.0 D on glasses to give more control over the exotropia.
- patients with fair and poor control, are best managed by recess or resect (strabismus surgery)
There are two types that are very important to recognize in comitant esotropia:
Congenital esotropia, this type is characterized by :
- Large angle esodeviation, the patient is born with a 40-50 PD or even larger angle.
- The patient has esodeviation before the age of 6 months.
- Usually, the patient has very mild hypermetropia +1 to +3 D, not more, or the patient might be emmetropic or myopic.
- The patient has full ductions, and he does not have any motility restriction. It is essential to R/o congenital 6th nerve palsy, which is very rare.
- Treatment of the condition is surgical. It is advised to perform surgery as early as possible to prevent amblyopia and muscle contracture, which can happen as time goes by.
A high refractive error causes this type of strabismus in the patient’s early life (2- 3 years), like high hypermetropia +6.0 and above or high astigmatism. The high refractive error will force the child to accommodate to clear up the image. In turn, this will activate both convergence and myosis along with the ciliary body contraction. From our prospect, what we see is in a squint.
- Treatment is aimed to relax the natural synchinatic relationship already built-in. We need to correct the child’s refractive error, either making him emmetrope or slight myopia.
- This type is more likely to get amblyopia than any other kind because most of the time, there will be ocular preference very early in life ( the child will prefer one eye, neglecting the other one). That is why the prompt correction of refraction with or without monocular occlusion therapy is needed to regain normal vision in these children.
Cover/ uncover test for patients with vertical strabismus
Amblyopia a quick definition and review:
Non- comitant strabismus:
- third nerve palsy