6 Tips to Master 24-2 and 24-2C Visual Field Exams

Visual field (VF) testing plays a pivotal role in modern optometry and ophthalmology, providing critical insights into a patient's visual function and aiding in the diagnosis and management of various ocular and neurological conditions. Among the most widely used VF tests are the 24-2 and 24-2C. The 24-2 exam is derived from the 30-2 protocol and evaluates the central 24 degrees of the retina with fixation centered on the fovea. It has become a standard tool for  detecting defects that could indicate glaucoma or other neuro-ophthalmic conditions. Each test point in the 24-2 examination is separated by 6 degrees, which can lead to small or shallow defects going undetected, particularly in the paracentral area. The 24-2C exam addresses  this problem by incorporating additional test points within the central 10 degrees, enhancing sensitivity in this area which is prone to glaucomatous damage. 

This article will explore the significance of these exams, offering insights into their clinical relevance, technical details, and practical tips for mastering their application in practice.

Understanding 24-2 and 24-2C Visual Field Exams

24-2 Visual Field Exam: The 24-2 VF exam is a standard test widely used in eye care practices to assess the central 24 degrees of a patient’s vision. It involves testing 54 points within this central area, with a particular focus on detecting visual field defects that may indicate the presence of glaucoma or other neuro-ophthalmic conditions. The 24-2 test is known for its efficiency and reliability in providing detailed information, making it a cornerstone in both diagnostic and monitoring processes.

24-2C Visual Field Exam: The 24-2C exam is an enhanced version of the 24-2 test, designed to improve the sensitivity of glaucoma detection, particularly in early stages. It includes 10 additional testing points within the central 10 degrees, which have been strategically placed to detect paracentral scotomas often  missed by the standard 24-2 test and which are indicative of early glaucomatous damage. This expanded coverage makes the 24-2C exam particularly valuable in detecting subtle defects and improving the accuracy of glaucoma diagnosis and management.

Clinical Relevance

Both the 24-2 and 24-2C exams are useful tools in the early detection and ongoing monitoring of visual field impairments. They play a significant role in diagnosing glaucoma, detecting early-stage disease, and monitoring its progression. These tests are also useful in identifying neurological disorders that may present with VF defects, such as optic neuropathies or brain lesions. By providing a comprehensive view of the patient’s visual field, these exams allow eye care professionals to tailor treatment plans effectively and track the efficacy of interventions over time.

Technical Details

The 24-2 and 24-2C exams are administered using automated perimetry, where patients respond to visual stimuli presented at various locations within their visual field. The 24-2 exam is often used for routine monitoring, while the 24-2C is favored in cases where more detailed assessment is required, such as in the early or advanced stages of glaucoma or when subtle defects are suspected. Interpreting the results involves analyzing the pattern of vision loss. In glaucoma, for example, characteristic patterns like nasal steps or arcuate scotomas may be evident.

Applications and Use Cases

The 24-2 and 24-2C visual field exams are essential tools in eye care, particularly for managing glaucoma, assessing neurological conditions, and advancing research.

• Glaucoma Management: As you might have guessed by now, the 24-2 and 24-2C exams are invaluable for glaucoma management. They allow for detailed mapping of the visual field, helping to identify early signs of glaucomatous damage and track progression over time. The newer 24-2C exam, with its additional central test points, provides even greater precision in detecting subtle defects, making it a critical component of comprehensive glaucoma monitoring. 
• Neurological Assessments: These exams are also vital in neurological assessments, where they help identify visual field defects caused by neurological conditions such as strokes or tumors. By detecting specific patterns of vision loss, these exams can assist in localizing the lesion within the brain and guiding further diagnostic evaluations.
• Research Uses: Beyond routine clinical use, the 24-2 and 24-2C exams have significant roles in research and innovative eyecare practices. They contribute to ongoing studies in glaucoma and neurological conditions, offering data that drives advancements in understanding and treatment. 
• Innovative Practices: Some practitioners are exploring innovative uses of these exams, such as integrating them with advanced imaging techniques to provide a more holistic view of the patient’s visual and ocular health, ultimately enhancing patient care.

Fun Fact: Interestingly, the 24-2 exam is the most common visual field test performed on Virtual Field platforms, with a visual field exam being run every 12 seconds globally. This frequency underscores the importance of these exams in daily clinical practice.

Practical Tips for Practitioners

There are several visual field test best practices that practitioners can use to enhance the accuracy and reliability of 24-2 and 24-2C exams, improving overall patient care.

1. Optimize the testing environment.
   Ensuring accurate and reliable results from 24-2 and 24-2C visual fields  begins with meticulous test administration. Best practices include consistently calibrating the visual field analyzer before each test and ensuring proper lighting conditions in the testing room. It’s essential to standardize the positioning of the patient’s head and the alignment of their gaze with the fixation target. Any deviation can lead to false results, compromising the reliability of the test. 

2. Prepare the patient for the exam.
   It’s imperative to familiarize patients with the testing process beforehand to reduce anxiety and increase performance. Explain what they should expect, emphasizing the importance of keeping their gaze fixed on the target while remaining as still as possible. This preparation not only minimizes patient anxiety but also maximizes cooperation, leading to more accurate outcomes.

3. Monitor test reliability indices.
   Interpreting the results of 24-2 and 24-2C visual field tests requires a keen eye for detail and awareness of common pitfalls. One such mistake is overlooking the importance of the test’s reliability indices, such as false positives, false negatives, and fixation losses. These markers indicate whether a test result is trustworthy or if retesting is necessary and should not be ignored. 

4. Develop an advanced, methodical approach to test result interpretation.
   Advanced interpretation involves recognizing subtle patterns that may not immediately suggest significant pathology but could actually indicate early or progressive changes. For instance, small, consistent depressions in sensitivity across multiple points could signal early glaucoma. Developing a methodical approach to interpretation, where each quadrant is analyzed systematically and compared to previous testing, can help in identifying these subtle but clinically significant changes.

5. Strategically use scheduling and software to your advantage.
   Integrating 24-2 and 24-2C exams into your practice requires a streamlined workflow to ensure that these tests are conducted efficiently and do not disrupt the overall patient experience. Performing these exams early in the appointment helps to avoid test fatigue that may lead to poor patient performance and allows sufficient time for interpretation and discussion with the patient. Using electronic health record (EHR) systems that seamlessly incorporate visual field data can also save time and reduce the risk of manual errors. 

6. Effectively communicate results to patients.
   When it comes to communicating results to patients, clarity is key. Avoid technical jargon and instead focus on explaining the implications of the findings in a way that the patient can easily understand. This not only improves patient satisfaction but also enhances compliance with recommended treatments or follow-up tests.

Conclusion

In conclusion, mastering the 24-2 and 24-2C visual field tests is essential for enhancing patient care through the detection and management of glaucoma and other neuro-ophthalmic conditions. By optimizing the testing environment, preparing patients effectively, and maintaining a keen focus on reliability indices, eye care professionals can ensure the accuracy of these critical assessments. 

Advanced interpretation techniques and strategic scheduling further streamline the integration of these exams into clinical practice, ultimately leading to more informed treatment decisions and improved patient outcomes. By clearly communicating results, practitioners can foster better patient understanding and compliance, reinforcing the value of these exams in preserving visual health.