AIIMS November 2011 – MCQ 193

The incidence of hydroxychloroquine retinopathy is low. The condition is closely related to daily dose of medication and duration of treatment. Risk factors for developing retinopathy include doses of chloroquine higher than 3 mg/kg daily and doses of hydroxychloroquine higher than 6.5 mg/kg daily, doses of hydroxychloroquine higher than 400 mg/d, and cumulative doses higher than 500 g. Other factors that increase risk of chloroquine toxicity include using the medication for longer than 5 years, high serum fat level, having renal or liver disease, having concomitant retinal disease, and being older than 60 years. Loss of vision is usually irreversible, even after cessation of the drug. These are in accordance with 2002 guidelines.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1472935/

New 2011 guidelines suggest-
The prior recommendation emphasized dosing by weight. However, most patients are routinely given 400 mg of HCQ daily (or 250 mg CQ). This dose is now considered acceptable, except for individuals of short stature, for whom the dose should be determined on the basis of ideal body weight to avoid overdosage. SCREENING SCHEDULE: A baseline examination is advised for patients starting these drugs to serve as a reference point and to rule out maculopathy, which might be a contraindication to their use. Annual screening should begin after 5 years (or sooner if there are unusual risk factors). SCREENING TESTS: Newer objective tests, such as multifocal electroretinogram (mfERG), spectral domain optical coherence tomography (SD-OCT), and fundus autofluorescence (FAF), can be more sensitive than visual fields.

Keep in mind thses are only talking about doasge of hydroxychloroquine and chloroquine itself.
http://www.ncbi.nlm.nih.gov/pubmed/21292109