Which of the following is a method to assess the function of the retina?

The method that directly assesses the function of the retina is Frequency Doubling Technology (FDT) perimetry. This test is particularly designed to evaluate the visual fields and can help detect various types of visual field loss, which may be indicative of retinal dysfunction or disease. By utilizing a patterned stimulus that alternates between lighter and darker shades, FDT can selectively engage certain retinal pathways and help in assessing the functionality of the retina itself in relation to visual perception.

On the other hand, tonometry is primarily focused on measuring intraocular pressure and does not directly assess retinal function. A slit lamp examination is used for detailed observation of the anterior segment of the eye but does not evaluate the retina's functioning capabilities. Fundus photography captures images of the retina and is valuable for diagnostic purposes, yet it primarily focuses on structural aspects rather than assessing retinal function. Thus, FDT emerges as the optimal choice for evaluating how well the retina is functioning in terms of visual field integrity and overall performance.