Third, fourth and sixth nerve palsies can cause debilitating diplopia. Strokes, lesions, car accidents, and systemic diseases such as diabetes and thyroid conditions can cause partial or total nerve palsies. Once the main cause of the palsy has been addressed, our goal is to help improve quality of life. If the nerve palsy has affected convergence, the patient can see well in the distance but struggle with reading.
Gary is a patient of mine struck down by a severe stroke, leaving him unable to walk, weaker RHS, slurred in speech and diplopia, which was worse for reading. He would follow an object one eye at a time temporally but was unable to reach straight ahead (especially with his RE) initially, but after a month of trying, he managed to be able to follow either eye across his midline, just. This meant he no longer had diplopia in the distance.
However, Gary is 69 years old and loves to read and with no accommodation stimulus left, he really struggled with the diplopia for near work. Short of covering one eye, he found relief with 2BI each eye for reading. The difficulty was that he did not tolerate any BI prism at distance. Two pairs in the nursing home is just too easily lost (or ‘borrowed’ by another person).