MONOCHROMATIC VISION 187 



Grunert^ has collected all the recorded cases up to the date of his 

 paper, adding four others. Cases have since been recorded by Bj errum^, 

 Ronne^, Hessberg^, Kollner^, Juler^, and Gertz'^. 



The total of published cases is 84 (Nettleship, 1909). Refractive 

 errors are common, generally moderate myopia ; correction produces 

 little improvement of vision. One case recorded by v. Hippel and 

 Uhthoff^ could see Rontgen rays, but this observation has not been 

 confirmed and was negatived in Ronne's case. The only case with 

 good central vision was Frau Prof. R., examined by Raehlmann^, 

 but this case is peculiar in other respects. Obj ective causes for defective 

 central vision have been found occasionally : — macular changes^", 

 pallor of the discs^^, moderate albinism^^, and corneal nebulae^^. 

 In the majority of cases the ophthalmoscopic appearances are quite 

 normal. In Konig's experiments^* on the influence of intensity of 

 illumination on visual acuity, as the intensity rises the curve shows a 

 well-marked angle where the intensity changes from scotopic to pho- 

 topic. In the wholly colour-blind Konig found that this angle was 

 absent, the scotopic part of the curve being continued in the same 

 direction without interruption until an intensity was reached which 

 caused dazzling and diminished visual acuity. In monochromatic 

 vision moreover the usual diminution in acuity in the parafoveal region 

 is not noticed. 



Photophobia and nystagmus are almost always present. The 

 former increases with the intensity of the light and is absent with low 

 illuminations. Bright light causes an unpleasant sensation of a luminous 

 cloud before the eyes. Central vision is also slightly improved by 



1 Arch.f. Ophth. LVi. 1, 132, 1903. ^ Hospiialstidende, 1145, 1904. 



3 Ibid. 1230, 1906 ; Klin. Monatshl. f. Augenhlk. xliv. Beilageheft, 193, 1906. 



* Klin. Monatshl. f. Augenhlk. xl\ti. 2, 129, 1909. 



^ Ztsch. f. Sinnesphysiol. xlhi. 409, 1909. 



« OpJithal. Rev. 65, 1910. ' Arch.f. Augenhlk. Lxx. 202, 228, 1911. 



» Bericht. d. Ophth. Gesellschft. Heidelberg, 150, 158, 1898. 



^ Wochenschr. f. Therapieu. Hygiene d. Auges, ii. 165, 1899 ; Ztsch. f. Augenhlk. ii. 315, 

 403, 1900. 



" Nettleship, St Thomas's Hosp. Rep. x. 37, 1880; Uhthoff, Ztsch. f. Psychol, u. Physiol, 

 d. Sinnesorg. xx. 326, 1899; Nagel, Arch. f. Augenhlk. xliv. 153, 1901; Hess, Ztsch. f. 

 Psychol, u. Physiol, d. Sinnesorg. xxix. 99, 1902 ; and Grunert, loc. cit. 



" Landolt, Arch. d'Opht. iv. 211, 1893 and Grunert, loc. cit. 



12 Uhthoff, op. cit, xxn. 1, 200 and Konig and Dieterici, the same case as Uhthoff's, 

 Sitz. d. Akad. d. Wiss. 805, 1886. 



" Raehlmann, Arch.f. Ophth. xxn. 29, 1879. 



1* Sitz. d. Akad. d. Wiss. Berlin, 559, 1897 ; see also Parsons, Roy. Loud. Ophth. Hosp. 

 Rep. XIX. 2, 283, 1914. 



