Abstract
Purpose :
Ophthalmic tests, like anything else, can be qualitative or quantitative. Qualitative tests may show you the pattern, but you need quantitation in order to determine progression. In 1862 Donders, who was interested in astigmatic and refraction asked his assistant, Snellen, to come up with a quantitative assessment of visual acuity. This was published 1863. There had been a previous attempt at quantitation in Vienna, but this did not specify the distance at testing and therefore failed to really achieve the goal of defining the visual angle. Albert von Graefe suggested separation of the two eyes using red and green glasses in order to determine motility. He did not act on it further. From 1908-1909, Hess took the same idea and turned it into a practical application, the so called Hess screen which offers major advantages in semi quantitative ocular motility of the two eyes.
Methods :
A 41-year review of previous motility disturbances done at a single university shows the values of the Hess screen.
Results :
Although there have been variations of the Hess screen done subsequently including the Lancaster screen, which includes the ability to determine torsion, the Hess screen is still popular and practical. It is also available now in computerized form.
Conclusions :
1. Hess screen allows immediate separation of primary and secondary deviation.
2. Hess screen does not permit evaluation of etiology. One cannot determine restrictive from paretic, and even from the uncommon primary over action.
3. The Hess screen is particularity useful in determining whether there is change over time, specifically whether there is spontaneous improvement, or improvement related to therapeutic intervention. It also determines when the motility disturbance becomes stable, suggesting the appropriate time to consider intervention.
4. An additional advantage to the Hess screen is that by recognizing over action in secondary deviation, that surgical planning may be better if it deals with the overacting second deviation.
5. The Hess screen is quite suggestive of which muscles need to be dealt with in terms of intervention.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.