At the very minimum, the following three tests should be performed on patients taking antimalarial drugs:

• BVA
• Dilated fundus exam: Be sure to perform DFE within the first year of antimalarial drug use.¹
• Central threshold visual fields, preferably (10-2)

Visual Fields:

Early toxicity can cause bilateral relative paracentral scotomas.⁴ Defects can be present BEFORE definitive signs are seen on fundus examination. Some experts suggest using a red stimulus or blue-yellow perimetry for early detection of retinopathy.⁵

Color Vision:

Not all experts believe that color vision testing is necessary on these patients every time they come in for follow-up. It is wise to perform color vision testing on all males during initial visit to detect any underlying congenital color deficiencies.¹ Color vision can be abnormal in early toxicity with Plaquenil and Aralen.

In general with antimalarial drugs:

• Blue/yellow defects occur in early toxicity.^5,6
• Red/green defects occur in late toxicity.⁶

Studies do show, however, that mixed color defects (meaning both red/green and blue/yellow) can occur in early toxicity.⁷ So, to maximize sensitivity for toxicity, experts recommend testing for both red/green and blue/yellow defects.⁷ My recommendation is to use the Ishihara plates to test for red/green defects and the Richmond HHR plates for blue/yellow defects.

Amsler Grid:

The Amsler grid is excellent for home monitoring. The red Amsler grid may be more effective at detecting early paracentral scotomas because the red target functions as a dim, white target. High false positive rates occur with red Amsler grids.⁸

Fundus Photography:

Fundus photography is optional only when macular tissues are completely normal.

Specialized Tests

Fluorescein Angiography:

Fluorescein angiography is done to ensure that macular tissues are healthy and to help distinguish antimalarial drug toxicity from other types of acquired maculopathies.^{1, 4}

Electrodiagnostic Testing:

• Full Field ERG/EOG measures the entire retina as one unit. It is not sensitive to early toxic changes;² it only shows abnormalities in late chloroquine or hydrochloroquine toxicity.¹ These tests help judge how severe or widespread the damage is once toxicity has been established.¹
• Multifocal ERG (mfERG) generates an array of local ERG responses that corresponds to the central 40 degrees. mfERG is better than full field ERG at detecting local changes in the retina. It can vary 10% to 30% from session to session, and to find definitive changes, a series of mfERG recordings need to be performed.^{9, 10} An mfERG can help confirm the absence of retinal toxicity when perimetry or other tests detect abnormalities.¹¹. Keep in mind that significant cataracts can affect the outcome of the mfERG.¹²

  In studies, 20% to 60% of patients receiving Plaquenil were found to have mfERG abnormalities; however, clinically significant hydroxychloroquine toxicity is quite rare.² It remains uncertain whether mfERG abnormalities are significant enough to warrant discontinuation of Plaquenil.² Some experts question whether mfERGs are any more sensitive at detecting early toxicity than 10-2 visual fields.⁹ More clinical studies are needed in this area.

	URL: http://www.opt.indiana.edu/ce/plaq/testing.htm Revised: May 7, 2007
	IU Optometry home page: http://www.opt.indiana.edu/ Comments (content): Dr. Julie Torbit at jtorbit@indiana.edu Comments: Web Administrator Page design and coding: Terri Greene Copyright © 2007, The Trustees of Indiana University