History of Potential Vision
Why measure Potential Vision in eyes with cataract?
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To identify eyes with POOR vision prognosis.
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To identify eyes with GOOD vision prognosis that appear abnormal on examination.
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Don't need to if there is no history of retinal disease, the retinal is clearly visible and appears normal. Ophthalmology (100:150S-177S), 1993)
Potential vision testing is the only proven method that predicts the vision outcome in eyes with cataract and comorbidity. Examination of the eye cannot predict the potential visual outcome in eyes with comorbidity. Published expert opinions are “All clinicians know that the appearance of the macula can be misleading: one that looks highly irregular may have excellent visual potential.” Samuel Masket, MD (6) and “The anatomic appearance of the macula on biomicroscopy or OCT does not always correlate well with macular function.” Jay S. Pepose, MD. PhD.(6). This is echoed in the Preferred Practice Plan of the American Academy of Ophthalmology, “Biomicroscopy and the ophthalmoscopic examination of the macular region do not necessarily predict macular function when the macular is abnormal.”
Vision Forecasting Evolution in 2023
A review board(1) of the Academy of Ophthalmology in 1993 concluded that it has not been proven that potential vision test can predict poor outcomes. In that review, it was concluded that the utility of potential vision tests was limited to cases in which the cataract was not dense.
Since 1993, 31 articles have been published where at least some of the of the patients had comorbidity. The first article to prove that potential vision testing can predict good and bad outcomes in eyes undergoing cataract surgery was in 1998 when Hofeldt and Weiss(2) used the Illuminated Near Card (INC) to predict to within 2 lines of letter in eyes with and without comorbidity in 95% of eye. The INC was renamed RAM® because it meters retinal acuity and combines Illuminated Near Card technology of brightly illuminated eye chart, correct visual angle, corrective refractive error, and multiperforated 1.0 mm pinhole aperture into a small hand-held portable instrument.
The RAM is the only potential vision test that consistently predicts good and bad outcomes by all investigators and is clinically proven. Studies using noncommercial devices(3,4) have shown acceptable predictions in eyes with comorbidity utilizing the pinhole and brightly illuminated charts. These experimental devices omitted the use of corrective lenses, corrective lenses have been shown to improve prediction.
In the presence of comorbidity, the pre-operative exam and OCT cannot predict vision outcomes. Pre-operative RAM test has prevented the incorrect operations (see reviews) by detecting preexisting disease not diagnosable by the physical exam, such as, cone dystrophy and amblyopia and correctly determining that cataract and not epiretinal membrane was the main cause of vision loss......changing the procedure from membrane peeling to cataract surgery.
The Power of Forecasting
Forecasting attempts to reduce the uncertainty of what is to come and this has turned man to religion and science for direction. In the realm of science, it was gambling that provided the impetus that lead to the development of the probability theory, which was fueled by the desire to increase the odds of winning. The probability theory forms the basis of statistics and is widely applied in all fields of science. The development and the implementation of the probability theory can be traced to great scholars, such as, Blaise Pascal (1623 –1662), Pierre de Fermat (1601 [or 1607] –1665), Christian Huygens (1629 –1695), Jacob Bernoulli (1654-1705), Abraham de Moivre (1667-1754), Pierre de Laplace (1749-1827, A. Kolmogorov (1903 – 1987), Peter L Bernstein (1919 – 2009), and others.
Peter L. Bernstein said, “When you think about risk, it essentially says we don’t know what is going to happen.” Relating this concept to cataract surgery, if you know what the vision outcome is going to be, risk of a poor outcome is reduced. In large part, the unpleasant surprise of poor vision following surgery due to undiagnosed conditions can now be avoided by potential vision testing with the Retinal Acuity Meter (RAM), the only potential vision test found consistently accurate in eyes withcomorbidity.
References
1. Appendix F. Literature Review: Potential vision Testing. Ophthalmology (100:150S-177S), 1993).
2. Hofeldt AJ, Weiss MJ. The illuminated near card assessment of acuity in eyes with cataract. Ophthalmology 105:1531-6,1998.
3. del Romo GB, Douthwaite WA, Elliott DB. Critical Flicker Frequency as a Potential Vision Technique in the Presence of Cataracts. Investigative Ophthalmology & Visual Science 46:1107-1112, 2005.
4. Vianya-Estopà M, Douthwaite WA, Noble BA, Elliott DB. Capabilities of potential vision test measurements Clinical evaluation in the presence of cataract or macular disease. Journal of Cataract & Refractive Surgery 32(7):1151-1160, 2006.