Source: http://www.aoa.org/x4931.xml

Be it either clinical or coding, the Commission on Paraoptometric Certification is your resource for certification.
The development of the CPC examinations begins with a job analysis, which results in identification of the major domains of practice through a survey of the knowledge, skills, and abilities needed for competent performance. The outline of the examinations' contents and specifications are derived from the results of the job analysis, including the relative emphasis or weight for each of the major sections is established.
Experienced practitioners are asked to draft questions for the examinations. These draft questions are reviewed by a panel of experts in the profession, editing as needed for consistency, accuracy, grammatical correctness, and for conciseness of presentation, so that each item is testing for knowledge and application of content and not for reading skills.
A draft of the examinations is drawn from the items which have been reviewed and approved for use by the subject matter experts. The CPC reviews all of the items on the examination one last time to ensure they are written clearly, have one and only one correct response, and are appropriate for the examinations. The CPC also participates in an exercise to determine the passing score each time a new form of the examination is approved.
Modern optometry demands that paraoptometrics accept and provide a key role in the practice. They must receive continual education and training in order to fill this role. Paraoptometrics serve only to enhance the profession of optometry, as well as the individual practices that employ them. Education and recognition is, and always will be, integral to the success of all professionals involved.
Certification is a voluntary process instituted by a nongovernmental agency in which individuals are recognized for advanced knowledge, competence, and skill. Certification requires assessment, testing, and evaluation of one's education and/or experience. A certification organization conducts a program to evaluate the competence of optometric assistants. The competent optometric assistant performs work accurately and interacts with other professionals and patients effectively. Competence must be demonstrated and maintained.
The Certified Paraoptometric examinations are prepared and administered by the Commission on Paraoptometric Certification (CPC) with the assistance of the Professional Testing Corporation. The purpose of this examination is to ensure a level of knowledge to perform the functions of a Certified Paraoptometric. Those who successfully complete an examination will be certified with the CPC and earn the appropriate designation.
The CPC promotes excellence in the field of optometric assisting by:
The Paraoptometric Certification Program can provide a formal declaration of education and skill achievement in the profession of paraoptometry. Increasing your knowledge of paraoptometry will give you the opportunity to improve your job satisfaction and your professional relationships with your doctor, your peers, and the patients you serve.
By becoming a certified paraoptometric, you may obtain the ability to become a part of the clinical team resulting in increased respect from the optometrist. Additionally, this program is designed for and achievable with minimal assistance from the optometrist and a minimal amount of funds.
Paraoptometric certification will instruct your staff to make the most efficient use of time allowing you to operate at your highest level. A Certified Paraoptometric reinforces your professional image, which can only enhance patient satisfaction. This may result in additional referrals of others to your practice.
A Certified Paraoptometric demonstrates a commitment to the profession of paraoptometry, which results in an increased level of competence.