One of the challenges in all of medicine is to accurately determine the structure and function of any organ and tissue. When an organ like the heart, brain or retina, for example, are healthy then by definition the structure and function are correlated with each other. In other words, if you can measure the structure or the function you can infer the other.
However, if the retina has a particular disease like macular degeneration (AMD) or diabetic retinopathy ( two of the more common disorders) then structure and function are not correlated with each other.
As a result, it’s even more important to have diagnostic tests that can independently measure structure and function. When you go to an ophthalmologist, the staff will check your vision on the acuity chart. Although all of us in ophthalmology and optometry do this test, it doesn’t really measure vision. This is because there are at least 8 different neural pathways from the eye to the back of head, the occipital lobe of the brain. The visual acuity test only measures only one of those pathways. So a patient may record a vision of 20/40 or 20/30 and report their vision is not normal. This is entirely possible for exactly the reason that is mentioned above.
So, what are the methods to measure structure and function of the retina? Over the last two to three decades there has been a remarkable advancement of diagnostic testing.
As to structure, one of the tests that we use is multimodal imaging. This includes: 1) Color photos of the retina. Often, we use wide angle imaging so that the far edges of the retina can be seen; 2) Autofluorescence imaging allows us as retina specialist to observe the debris deposits underneath the retina as well as determine the areas of the retina where the nourishing cells (RPE cells) may have died; 3) Optical coherence tomography (OCT) provides high resolution imaging of the 9 microscopic layers of the retina, the RPE and also the largest blood supply per unit weight in the entire body called the choroid. This is found under the retina.
We can measure function by two different methods: 1) Like the EKG of the heart, the electrical response of the retina, optic nerve and RPE can be recorded. This electrophysiological testing is extremely valuable to determine the actual objective function of these structures; 2) Microperimetry is another functional test that actually allows us to map out the sensitivity of the regions of the retina, particularly the macula, the area of central high acuity vision.
Thus, by measuring the structure and function of the retina we, as retina specialists, have really refined our diagnostic and prognostic abilities. This of course helps to catch and treat diseases much earlier than we ever have done in the past.
Dr. Shalesh Kaushal, MD, PhD is considered one of the foremost authorities on retinal disease, Dr. Kaushal offers advanced diagnostics and a unique approach to uncover the core of why certain retina conditions exist, as well as the most optimal way to treat them. Dr. Shalesh Kaushal is an The Villages, FL based board-certified ophthalmologist specializing in the area of vitreoretinal disease and serving patients in the Ocala, FL area. Considered one of the foremost authorities on retinal disease, Dr. Kaushal offers advanced diagnostics and a unique approach to uncover the core of why certain retina conditions exist, as well as the most optimal way to treat them. In 2009, Dr. Kaushal was recruited to the University of Massachusetts as the chairman to build a new eye center, which at the time was the first, new academic Department of Ophthalmology in the United States in over 25 years.
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