In =neuralgia= of the eye, =blepharitis=, =obscure pain=, =conjunctivitis= and often deeper troubles you will find a bad condition of the =nasopharynx=, such as adenoids, vegetations, pus pockets, adhesions in the fossa of Rosenmuller, contraction of the soft palate, disturbed relations of the septum and turbinates, sinus trouble, poor drainage, exostoses and polyps. In eye disease all these things should be discovered if they are present, in order to get best results and in order to make a careful diagnosis. Examination of the Eye by Special Methods The first thing after the family history, personal history, inspection of the eye and the osteopathic examination, is to find out how well the patient can see. To test the acuteness of vision certain test letters are used. Snellen’s Test Letters are good. The normal eye can read 3-8 inch letters at twenty feet. The test letters on the cards usually range in size to be read at 10, 15, 20, 30, 40, 50, 70, 100 and 200 feet. The most desirable distance is 20 feet. If at the distance of twenty feet he reads the 3-8 inch letters his acuteness of vision would be marked 20-20 or normal. Always use the distance between patient and chart as the numerator of the fraction and the number above the letters which he reads as the denominator. If he is twenty feet away, the numerator remains twenty and the denominator changes according to the line of letters seen on the test cards thus: 20-15, 20-30, 20-70, or 20-200 may express the vision. If the patient could not see the 200 feet letters at 20 feet he must be brought nearer, say 10 feet, for him to see the large letters; his vision would be 10-200. These fractions representing the acuteness of vision may be expressed in meters. Some charts have letters numbered that way. If the vision is good enough for small objects to be clear, the near point should be taken. This would show the amount of accommodation of the eye. This is expressed in diopters. A =diopter= is the unit of measurement of the =refractive= power of lenses. =Lenses= are numbered by their refractive power in diopters. A lens that has a curvature that will refract parallel rays of light and bring them to a focus at one meter distance is said to be a one diopter lens. This unit of measurement for the refractive power of lenses was proposed by Nagel in 1866. It soon became quite generally used. The focal distance of a lens decreases as the strength of a lens increases. One diopter lens (written 1 D) has a focus of one meter (1 M) or 100 cm distance. A 2 D lens has a focal distance of ½ M or 50 cm. A 4 D lens has 25 cm focal distance and a ½ D lens has 100 cm ÷ ½ = 200 cm distance or 2 M. Trial cases have in them lenses varying in strength from .12 D or .25 D to 20 D of the spheric form. We will not discuss the trial case here. Accommodation in the Eye