Br J Ophthalmol: first published as 10.1136/bjo.63.2.90 on 1 February 1979. Downloaded from

British Journal of Ophthalmology, 1979, 63, 90-96

Bilateral symmetry of vision disorders in typical retinitis pigmentosa

ROBERT W. MASSOF, DANIEL FINKELSTEIN, STUART J. STARR, KENNETH R. KENYON, JAY A. FLEISCHMAN, AND IRENE H. MAUMENEE From the Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA

SUMMARY Bilateral symmetry of disorders of vision is examined in 60 typical patients with retinitis pigmentosa. We observed a very high degree of interocular congruence in the patterns of both kinetic visual field defects and threshold profiles and in abnormalities of foveal colour discrimination and visual acuity. Abnormalities of foveal colour vision are highly correlated with the extent of visual field loss.

Typical retinitis pigmentosa (RP) is a clinical velopment (of intraretinal pigmentation) is extremely syndrome of inherited diffuse pigmentary retinal characteristic'. dystrophy characterised by (1) nyctalopia, (2) mid- The present study examines bilaterial symmetry peripheral ring-like scotoma or field contraction, of vision disorders in 60 typical RP patients. We (3) narrowed retinal arterioles, (4) mid-peripheral observed a very high degree of bilateral similarity intraretinal 'bone-spicule' pigmentation, (5) rela- in the pattern of kinetic visual field defects, absolute tively good visual acuity until late in the course of threshold profiles, and abnormalities in foveal the disease, and (6) no known toxic, systemic meta- colour discrimination and visual acuity. Further- bolic, or inflammatory origin of the degeneration. more, the present study finds that the abnormalities The various modes of inheritance of typical RP have of foveal colour vision are highly correlated with the been identified as autosomal dominant, autosomal extent of visual field loss. http://bjo.bmj.com/ recessive, X-linked, and sporadic, usually assumed to be recessive in origin (Jay, 1972). It is a general Patients and methods clinical impression that progression of the disease is bilaterally symmetrical (Pearlman, 1977), although We evaluated 60 patients meeting our 6 criteria of exceptions to this symmetry have been epitomised typical RP (outlined above). Patients ranged in age in cases described as 'unilateral retinitis pigmentosa' from 8 to 70 years. The modes of inheritance were

(Carr and Siegal, 1973). distributed as follows: 330/ autosomal dominant, on October 5, 2021 by guest. Protected copyright. The documentation of bilateral symmetry has 4 X-linked, and 63 % autosomal recessive or received little formal attention. Gonin (1901), in sporadic. Informed consent was obtained from each describing the ring scotoma as a characteristic patient participating in the study. feature of typical RP, concluded from 6 of his own All tests were performed monocularly on each eye cases and a review of 20 other cases that the ring of each patient. After correction of refractive error scotoma was 'bilateral and symmetric'. Zeavin and the visual acuity was determined. Kinetic visual Wald (1956) noted a strong bilateral symmetry in fields were measured with a Goldmann perimeter absolute threshold profiles measured in 6 RP using the V/4 target. Colour discrimination was patients. Biro (1963), briefly summarising observa- measured with the Farnsworth-Munsell 100 hue test tions of fundus pigmentation in over 500 cases, using a Macbeth illuminant. concluded that the 'tendency to symmetrical de- Absolute thresholds were measured at the fovea and at 7 to 11 peripheral positions along each of 4 Address for reprints: Robert W. Massof, PhD, Wilmer semimeridians (nasal, temporal, superior, and Institute, B-34, Johns Hopkins University School of Medicine, inferior) employing the Tubinger perimeter (Sloan, Baltimore, Maryland 21205, USA 1971). Threshold values were obtained for a blue- 90 Br J Ophthalmol: first published as 10.1136/bjo.63.2.90 on 1 February 1979. Downloaded from

Bilateral symmetry of vision disorders in typical retinitis pigmentosa 91 Visual acuity (OD) 20/160 20/100 20170 20/50 20/30 20/20 20/200, 20/120 20/80.20/60. 20/40 . 20/25,

0-2 oz / 20/15 0.1 0*0 . * 20/20 -0-1 * / . * 20/25 Fig. 1 Log decimal visual - 02.220/30/ acuity of right eye is plotted 0 3 20/40 0 against log decimal visual acuity a02/ o ofeft eye for each patient '04 / * 20/50 (points). Snellen notation is also - os / * 20/60 D, indicated on the figure. The / 7 20/70 C dotted lines bound a range of .u<06 * / 7 * 20/80 w ~~~~~~~~~~~~~0° ±03 log units (approximately n - 0.7 ,/ 20/100 :Iline on the visual acuity 0 - 20/120 ehart) 8 -0.9 / / 20/160 i-O.1/0 / / 20/200 - 1-1 ,/ , -1*2 / - 1-3 /' 20/400

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green light ( =max 500 nm), subtending a visual on a dark background angle of 20, and flashed for http://bjo.bmj.com/ 2 7 / 500 milliseconds. The patient was dark-adapted for / * 45 minutes prior to the threshold measurements. 26 * / Absolute thresholds were defined as the mean of / 3 to 5 repetitions of an ascending method of limits 2 5 * / (from below threshold) and were expressed as log relative values (maximum luminance=2-1 fL).

E * on October 5, 2021 by guest. Protected copyright. '23 * Results o VISUAL 22 ACUITY o Visual acuity fractions were converted to log 1 1** decimal acuity.* In Fig. log decimal visual acuity 0 for the right eye is plotted against the log decimal acuity for the left eye for each patient. If 2-0 0 e.>perfect|visual bilateral symmetry were obtained, all the 9 /data points in Fig. 1 would fall on the solid diagonal line, that is, a perfect correlation between the 2 eyes ______/would exist. To determine the extent of correlation 1.9 20 2 1 22 223 2-4 2-5 2'6 27 between the visual acuities of the right and left eye Log colour error sum (OD) a product moment correlation coefficient was cal- Fig. 2 Log colour error sum for the right eye is plotted culated. A high correlation was obtained (r=0 63; against the log colour error sum for the left eye for each *Each line of the visual acuity chart represents approximately patient (points) equal changes in angular subtense on a logarithmic scale. Br J Ophthalmol: first published as 10.1136/bjo.63.2.90 on 1 February 1979. Downloaded from

92 R. W. Massof, D. Finkelstein, S. J. Starr, K. R. Kenyon, J. A. Fleischman, and I. H. Maumenee

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Fig. 3 Representative examples of visual fields from log of the sum of all errors.t In Fig. 2, the error (A) a normal observer and (B-J) retinitis pigmentosa score for the left eye is plotted against the error patients for the right eye (solid line) and left eye score on October 5, 2021 by guest. Protected copyright. (dashed line), employing the V/4 target on the for the right eye. If perfect symmetry were Goldmann perimeter. Visual,fields for both eyes are obtained, all the data points would fall on the plotted with respect to nasal and temporal orientation diagonal line. Calculation of the product moment to compare patterns of,field loss. The lines bound areas correlation yielded a very high coefficient (r=0-88), in which the target can be seen. The percentage of indicating that loss of colour discrimination in the normal visual field area is indicated.for each pair offields right eye parallels the loss in the left eye.

VISUAL FIELDS A qualitative assessment of bilaterial symmetry a perfect correlation is r=1 00), indicating that in the pattern of visual field loss was made by visual acuity in the right eye parallels visual acuity plotting the mirror image of the visual field for the in the left eye. left eye over the visual field for the right eye. Fig. 3 illustrates representative examples of these com- COLOUR DISCRIMINATION parisons. The results of the Farnsworth-Munsell 100 hue test tThe log of the error sums is employed because the variability were converted to a single error score by taking the in the error sums is proportional to the mean error sum. Br J Ophthalmol: first published as 10.1136/bjo.63.2.90 on 1 February 1979. Downloaded from

Bilateral symmetry of vision disorders in typical retinitis pigmentosa 93

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Each visual field was converted to a single number ABSOLUTE THRESHOLD PROFILES by measuring the total area of visual function with a The mirror image of the sensitivity profile forjthe planimeter. The resulting visual field area is ex- left eye was plotted along with the sensitivity profile on October 5, 2021 by guest. Protected copyright. pressed as a percentage of normal by dividing each for the right eye for each patient. As exemplified in value by the area of the average normal visual field. Fig. 5, not only does the loss of sensitivity occur to The numbers beside the visual fields in Fig. 3 indicate about the same degree in each eye, but also the the measured areas of visual function (expressed as shapes of the sensitivity profiles are quite similar. percentage of normal) for each example. These data complement the visual field data plotted The numerical value for visual field area of the in Fig. 3. A comparison of the data from patients right eye is plotted against the numerical value for with RP with normal values (Fig. 5L) demonstrates visual field area of the left eye, for each patient, in a 10 to 2-0 log unit loss in foveal sensitivity for all Fig. 4. If perfect bilateral symmetry were obtained, patients. all the data points would fall on the diagonal line. The calculation of the product moment correlation Discussion yielded a nearly perfect correlation coefficient (r=096). Thus, visual field area loss in the right eye We found a high degree of bilaterial symmetry in parallels to a high degree the visual field area loss loss of visual function in patients meeting the in the left eye. criteria of typical RP, independent of the mode of Br J Ophthalmol: first published as 10.1136/bjo.63.2.90 on 1 February 1979. Downloaded from

94 R. W. Massof, D. Finkelstein, S. J. Starr, K. R. Kenyon, J. A. Fleischman, and L H. Maumenee

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0 10 20 30 40 50 60 70 80 90 100 http://bjo.bmj.com/ INFE RI. Visual field area OD M/ of normal) Figs 3i, 3j inheritance. This statement holds true for visual the presence of disorders of foveal vision at all acuity, colour discrimination, kinetic visual fields, stages of RP progression, as evident in the measures and static absolute threshold profiles. Such bilateral of colour discrimination and absolute foveal on October 5, 2021 by guest. Protected copyright. symmetry, in both the extent and pattern of loss of thresholds. Previous investigators have made similar visual function, complemented by Biro's (1963) observations (Zeavin and Wald, 1956; Sunga and finding of symmetry in fundus pigmentation, suggests Sloan, 1967; Adams et al., 1972), but such foveal a high degree of congruence in the pattern and abnormalities have been overshadowed by the usual natural history of the retinal degeneration. persistence of good visual acuity until late in the The finding of a high degree of symmetry in RP is course of RP. As shown in Fig. 6, we observed a important from the standpoint of evaluating therapy high correlation between the colour error score and which employs one eye as a control (for example, reduction in the area of visual field (r=0-73). These Berson's (1971) total light exclusion trial) and for results indicate that progression in loss of foveal better understanding the natural course of RP. The colour discrimination is parallel to the loss of visual symmetry in the pattern of vision loss (see Figs. 3 field. and 5) suggests that the progression follows morpho- In conclusion, we have found that bilateral logical features yet to be identified. We are at present symmetry in loss of visual function is a characteristic examining this suggestion in more detail. feature of typical RP. Also, from the high degree of A consistent observation in the present study was congruence in visual fields and threshold profiles, Br J Ophthalmol: first published as 10.1136/bjo.63.2.90 on 1 February 1979. Downloaded from

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96 R. W. Massof, D. Finkelstein, S. J. Starr, K. R. Kenyon, J. A. Fleischman, and L H. Maumenee

28 1 RP mechanism that similarly affects both foveal and peripheral visual function. 2-7 t Supported by research grants from the National Institutes 2-6* o of Health (EY-01791) and the National Retinitis Pigmentosa 0 * Foundation. 2-5- X *0a 0 References E 2-4- Adams, A., Aspinall, P., and Hayreh, S. S. (1972). Primary 0-o0 so 0 0 retinal pigmentary degeneration. Transactions of the ° 2-32 o 0 °- 0o? Ophthalmological Societies of the United Kingdom, 92, cr 233-249. 0 0 0 Berson, E. L. (1971). Light deprivation for early retinitis 20 ,Po0* * pigmentosa. Archives of Ophthalmology, 85, 521-529. Biro, I. (1963). Symmetrical development of pigmentation as 91 a specific feature of the fundus pattern in retinitis pig- mentosa. American Journal of Ophthalmology, 55, 1176- 1179. Carr, R. E., and Siegel, I. M. (1973). Unilateral retinitis pigmentosa. Archives of Ophthalmology, 90, 21-26. Gonin, J. (1901). Le scotome annulaire dans la d6g6n6res- 10 20 30 40 50 60 70 80 90 100 Visual field area (% of normal) cence pigmentaire de la retine. Annales d'Oculistique, 125, 101-130. Fig. 6 Log colour error sum is plotted against Jay, B. (1972). Hereditary aspects of pigmentary retinopathy. percentage ofnormal visualfield area for each patient. Transactions ofthe Ophthalmological Societies ofthe United Closed circles represent data fbr the right eye and open Kingdom, 92, 173-178. circles represent data for the left eye. The best-fit Pearlman, J. T. (1977). Retinitis pigmentosa: an improved line from a linear regression analysis is plotted along clinical approach. Documenta Ophthalmologica, Proceed- ings of the 14th ISERG Symposium, 235-238. with the data points Sloan, L. L. (1971). The Tubinger perimeter of Harms and Aulhorn: recommended procedures and supplementary equipment. Archives of Ophthalmology, 86, 612-622. we conclude there is symmetry in the pattern of Sunga, R. N., and Sloan, L. L. (1967). Pigmentary degenera- visual function loss. The high correlation between tion of the retina: early diagnosis and natural history. Investigative Ophthalmology, 6, 309-325. loss of foveal colour discrimination and loss of Zeavin, B. H., and Wald, G. (1956). Rod and cone vision in visual field implies the existence of a bilaterally retinitis pigmentosa. American Journal of Ophthalmology, symmetrical, progressive, diffuse component to the 42, 253-269. http://bjo.bmj.com/ on October 5, 2021 by guest. Protected copyright.