Pearls for Cataract Surgery: Anterior Chamber Depth Differences

By Anne Dwyer, COMT

An anterior chamber depth can provide valuable information prior to cataract surgery. Technicians are trained to take accurate “A’s and K’s”—axial length and keratometry readings. These two measurements are the basis for calculating intraocular lens power for cataract surgery. While these two measurements are critical, the anterior chamber depth can often alert the physician to potential intraoperative challenges.

A shallow anterior chamber depth reading can be due to technician error, particularly if using contact A-scan ultrasonography. However, the use of optical coherence biometry and immersion A-scan technology has significantly reduced this error.

The anterior chamber depths of each eye should be evaluated carefully prior to cataract surgery. Longer axial length eyes typically have deeper anterior chamber depths, while shorter eyes have shallower chambers. Significant shallowing of an anterior chamber depth, especially in a normal or long eye, can indicate challenges ahead. In particular, an eye with pseudoexfoliation and a shallow anterior chamber can be indicative of phacodonesis. A cataract that has become intumescent will often cause a significant shallowing of the anterior chamber depth. An unusually deep anterior chamber depth in one eye may be indicative of past trauma. This history may not have been elicited during the physician examination.

A more significant sign is often an anterior chamber depth difference between the two eyes. A difference of .5 mm or more may be suggestive of lens instability in one eye. The technician performing the A-scan should alert the ophthalmologist to any unusual anterior chamber depth readings discovered during the scan. This will give the physician the opportunity to further counsel the patient if necessary and prepare an appropriate surgical plan.