The health insurance open season presents special problems for the nearly 2 million federal retirees. Some, lucky enough to be offered early retirement, are as young as age 43. Others are past 100. Pensions range from the very comfortable to near-poverty levels. Some run marathons while others are bedridden.

Workers and retirees have until Dec. 10 to pick their 1991 health plan. If they don't switch they will be kept in their current plan for another year.

In earlier columns we've passed on recommendations of health insurance experts for single workers (Nov. 13); families (Nov. 14); special groups of workers, such as congressional employees, Foreign Service officers and law enforcement personnel (Nov. 20) and for people seeking the best dental coverage (Nov. 27). Today, with the help of insurance expert Gordon F. Brown, the ratings are for retirees.

Brown headed the federal health program at the Office of Personnel Management. Now he reports on health matters for the National Association of Retired Federal Employees. He has also written the 126-page "Open Season Guide" which is available at newstands, or by calling 202-546-3394.

Brown generally rates fee-for-service plans (as opposed to health maintenance organizations) as among best buys for retirees. His ratings include the total likely cost to an individual and retiree for the year, including premiums and out-of-pocket costs.

For retirees without Medicare Part B who need single coverage he suggests National Association of Letter Carriers, American Postal Workers Union, GEHA, National Treasury Employees Union, Blue Cross standard, Mail Handlers high option, Mail Handlers standard option, Blue Cross high option and Alliance high option. For retirees needing family coverage he suggests GEHA, APWU, NTEU, Blue Cross standard, NALC, Postmasters standard, Alliance standard, Mail Handlers high option, Postmasters high option, Blue Cross high option, Mail Handlers standard option and Alliance high option.

For retirees with Medicare Part B seeking single coverage Brown advises them to look at Mail Handlers standard, Blue Cross standard, Alliance standard, NTEU, GEHA, APWU, Postmasters standard, NALC, Postmasters high option. For family coverage he recommends checking out Mail Handlers standard, Mail Hanlders high option, Blue Cross standard, APWU, GEHA, Alliance standard, NTEU, NALC, Postmasters standard and high option, Blue Cross high option and Alliance high option.

Brown cautions that the otherwise excellent and low-cost Mail Handlers plan has "relatively poor prescription benefits." He also notes that both the Mail Handlers options and Postmaster standard option pay physician-care benefits based on a fee schedule rather than as a percentage of the reasonable-and-customary system.

Health Plan Hotline

Tomorrow at noon on WNTR radio (1050 AM), representatives of fee-for-service, union and an HMO health plan will talk about what they offer federal workers and retirees, and will answer questions from callers about premiums, benefits and service.