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Chapter: Ophthalmology: Lacrimal System

Lacrimal System: Examination Methods

Lacrimal System: Examination Methods
Evaluation of Tear Formation, Evaluation of Tear Drainage

Examination Methods

Evaluation of Tear Formation

Schirmer tear testing: This test (Fig. 3.4) provides information on thequan-tity of watery component in tear secretion.

Test: A strip of litmus paper is inserted into the conjunctival sac of the tem-poral third of the lower eyelid.

Normal: After about five minutes, at least 15 mm of the paper should turnblue due to the alkaline tear fluid.

Abnormal: Values less than 5 mm are abnormal (although they will notnecessarily be associated with clinical symptoms).

The same method is used after application of a topical anesthetic to evaluate normal secretion without irritating the conjunctiva.

Tear break-up time (TBUT): This test evaluates thestability of the tear film.

Test: Fluorescein dye (10µl of a 0.125% fluorescein solution) is added to theprecorneal tear film. The examiner observes the eye under 10 – 20 power magnification with slit lamp and cobalt blue filter and notes when the first signs of drying occur (i) without the patient closing the eye and (ii) with the patient keeping the eye open as he or she would normally.

  Normal: TBUT of at least 10 seconds is normal.

Rose bengal test: Rose bengaldyes dead epithelial cells and mucin.This testhas proven particularly useful in evaluating dry eyes (keratoconjunctivitis sicca) as it reveals conjunctival and corneal symptoms of desiccation.

Impression cytology: A Millipore filter is fastened to a tonometer andpressed against the superior conjunctiva with 20 – 30 mm Hg of pressure for two seconds. The density of goblet cells is estimated under a microscope (normal density is 20 – 45 goblet cells per square millimeter of epithelial sur-face). The number of mucus-producing goblet cells is reduced in various dis-orders such as keratoconjunctivitis sicca, ocular pemphigoid, and xeroph-thalmia.

Evaluation of Tear Drainage

Conjunctival fluorescein dye test: Normaltear drainagecan be demon-strated by having the patient blow his or her nose into a facial tissue following application of a 2% fluorescein sodium solution to the inferior fornix.

Probing and irrigation: These examination methods are used tolocate ste-noses. After application of a topical anesthetic, a conical probe is used todilate the punctum. Then the lower lacrimal system is flushed with a physio-logic saline solution introduced through a blunt cannula (Figs. 3.5 a andb). If the passage is unobstructed, the solution will drain freely into the nose.

Canalicular stenosis will result in reflux through the irrigated punctum. If the stenosis is deeper, reflux will occur through the opposite punctum (Fig. 3.6).

A probe can be used to determine the site of the stricture, and possibly to eliminate obstructions (Fig. 3.7).

Radiographic contrast studies: Radiographic contrast medium is instilled inthe same manner as the saline solution. These studies demonstrate the shape, position, and size of the passage and possible obstructions to drainage.

Digital substraction dacryocystography: These studies demonstrate onlythe contrast medium and image the lower lacrimal system without superim-posed bony structures. They are particularly useful as preoperative diagnostic studies (Fig. 3.8). 

Lacrimal endoscopy: Fine endoscopes now permit direct visualization ofthe mucous membrane of the lower lacrimal system. Until recently, endo-scopic examination of the lower lacrimal system was not a routine procedure.

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