In the clinical examination, the anterior chamber should be examined for: cells and flare  foreign bodies (Molteno's tube and silicone oil and less commonly heavy liquid) depth of the anterior chamber if you suspect the anterior chamber is shallow especially if there were signs of previous acute angle closure glaucoma  (the angle is assessed by the van Herick's method and the depth of the  anterior chamber is measured using the method described in the section on  common examination techniques)  Cells and flare Molteno's tube silicone oil  Return to the main page

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

van Herick's technique (depth of peripheral anterior chamber (PAC) compared to the adjacent   corneal thickness (CT) at temporal corneal limbus at 60° angle) The technique uses the following set-up: optical section 60° between observation and illumination  full slit length  magnification approximately x 15  low to medium illumination  place optical section just inside limbus.  Assuming the corneal thickness = 1 unit, assess the width of the  "aqueous gap" or peripheral anterior chamber from corneal  endothelium to iris     Grade  Ratio of aqueous gap/cornea clinical interpretation 4 > 1/2 : 1 closure impossible 3 = 1/2 - 1/4 : 1 closure impossible 2 = 1/4 : 1 closure possible 1 < 1/4:1 closure likely with full dilatation 0 nil closed   Return to the top

 
 
 
 
 
 
 
 
 
 
 

Cells and flare in the anterior chamber
 

Mutton fat keratic precipitates Fine stellate keratic precipitates in  Fuch's heterochromic cyclitis Koeppe nodules at the pupil margin Busacca nodule

. Cells and flare are common signs in uveitis. You need to look for other associated signs which may point to the type  of inflammation. Most candidates should have not problems spotting mutton fat precipitates but stellate precipitates may be easily missed if they were small and sparse. The other signs which may be missed are granulomas on the iris. The Koeppe nodules are found at the pupil margin  and tend to be smaller and more common than Busacca nodules. Both conditions are indicative of granulamatous  inflammation.     Return to the top .

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Molteno's tube
 

.  Molteno's tube can usually be easily spotted. However, if the tube is short, it may not be apparent unless you  get the patient to look down.  Molteno's tube is usually associated with the following signs: previous trabeculectomy (very often there are more than one trabeculectomy with several iridectomies)  neovascular glaucoma  iridocorneal endothelial syndrome advanced glaucomatous disc. Return to the top

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Silicone oil and heavy liquid
 

Emulsified silicone oil in the anterior chamber (hyperoleon) Globules of heavy liquid in inferior anterior chamber

. With the advance of vitreoretinal surgery, the above physical signs are becoming more common in the clinical examination.  Always ask to examine the posterior segment for the presence of previous retinal detachment, proliferative vitreoretinopathy  and advanced proliferative diabetic retinopathy.  Silicone oil in the anterior chamber The superior anterior chamber contains fine suspension of silicone oil. The oil may appear milky owing to emulsification (so-called inverted hypopyon). Look for: complications associated with the oil (ie. band keratopathy and cataract) presence of Anton's iridotomy (this is iridectomy performed at 6 O'clock in aphakic patient to prevent  pupillary block) previous retinal detachment Heavy liquid in the anterior chamber There are globules of liquid in the inferior part of the anterior chamber.  Look for: previous retinal detachment operation  .

Questions:

1. What are the uses of silicone oil?

Answer
Internal tamponade in giant retinal tears, complex or traumatic retinal detachments
Closure of breaks which are complicated by proliferative diabetic retinopathy or proliferative vitreoretinopathy
Dissection of epiretinal membranes and flattening of the retina

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