History of the disease

In 1937, Bietti^4,5 described three patients with retinal degeneration beginning in the third decade of life. All were characterized by glittering crystals in the posterior pole and in the superficial paralimbal cornea. Welch, in 1977, first used the term crystalline retinopathy, which so aptly describes the most characteristic feature of this disease.³⁷ Over 90 cases have been reported worldwide. The disease appears to be more frequent among Asians.^16,21 Although most accepted cases have crystals in both the cornea and the retina, some patients, who are otherwise typical, lack crystals in the cornea.^10,14,28,33 Other patients will show only retinal crystals for years before corneal crystals become evident.¹⁹ As the disease progresses to later stages, the crystals in the retina become less apparent and eventually disappear.^3,35 Heterogeneity probably exists for Bietti's crystalline dystrophy (BCD). Wilson et al.³⁸ have suggested that the electrophysiological findings can differentiate two subtypes of BCD: a diffuse type (figures 63.1 to 63.3), with a profoundly abnormal electroretinogram (ERG),^2,4,38,39 and a regional or localized type (figures 63.4 to 63.6), with a more intact ERG that may be either normal or only mildly abnormal (figure 63.7).^14,34,38,39 Reports have detailed the progressive nature of BCD and have provided long-term follow-up information for 11,³⁸ 16,²¹ 20,² 26,²¹ and 30 years.^19,20 Some reports suggest that patients can progress from the regional to the diffuse phenotype.^3,19,20 Whether these two types represent allelic or genetic homogeneity remains unclear. Interestingly, the patient reported by Jurlies et al.¹⁹ demonstrated at 34 years of age an electronegative scotopic ERG, a feature that was not reported by others with regional expression of the disease, even at age 58 years.³⁸

Figure 63.1.  

Fundus appearance (A) and fluorescein angiogram (B and C) of the right eye of a Japanese woman (patient of Wilson et al.³⁸) with the diffuse form of Bietti's crystalline dystrophy of cornea and retina at 36 years of age. (From Wilson DJ, Weleber RG, Klein ML, Welch RB, Green WR.³⁸ Used by permission.)

Figure 63.2.  

Same patient as in figure 63.1 at 45 years of age (A and B). Note the further loss of pigment epithelium and choriocapillaris over the nine-year interval. (From Wilson DJ, Weleber RG, Klein ML, Welch RB, Green WR.³⁸ Used by permission.)

Figure 63.3.  

Goldmann perimetric visual fields for patient shown in figure 63.1 with the diffuse form of Bietti's dystrophy at 36 (A) and 45 (B) years of age. Her visual acuity decreased from 20/30 J1 OU at 36 years of age to 20/50 J1 OU at 47 years of age. From 47 to 48 years of age, her visual acuity dropped to finger counting at 4 feet OD and at 7 feet OS; she was unable to read any Jaeger type at near distance. (From Wilson DJ, Weleber RG, Klein ML, Welch RB, Green WR.³⁸ Used by permission.)

Figure 63.4.  

Fundus appearance (A) and fluorescein angiogram (B) of the superior border of atrophic lesions in the posterior pole of the right eye of a 52-year-old man with the regional form of Bietti's crystalline dystrophy (patient 2 in Wilson DJ, Weleber RG, Klein ML, Welch RB, Green WR.³⁸). Note that crystals are prominent in the transition zone of disturbed RPE between atrophic retina and normal peripheral retina.

Figure 63.5.  

Goldmann perimetric visual fields of a 49-year-old man with the regional form of Bietti's crystalline dystrophy (patient 2 in Wilson DJ, Weleber RG, Klein ML, Welch RB, Green WR.³⁸). Same patient as shown in figure 63.4. Although his visual acuity was 20/25 in each eye, the patient was greatly bothered by pericentral scotomas.

Figure 63.6.  

Fundus appearance (A) and fluorescein angiogram (B) of the left eye and Goldmann perimetric visual fields (C) of a 61-year-old man with the regional form of Bietti's crystalline dystrophy (patient 3 in Wilson et al.³⁸). The visual fields had not changed over those determined nine years previously, but the visual acuity had decreased from 20/30 J1 to 20/40 J2.

Figure 63.7.  

Ganzfeld ERGs of two patients with the regional form of Bietti's crystalline dystrophy (patients 2 and 3 in Wilson et al.³⁸) as compared with a normal ERG on the left. ERGs from the right and left eyes were averaged to produce the tracings shown for the normal individual and patient 2. The stimulus spikes for the 30-Hz flicker and the photopic and scotopic responses for the normal ERG and patient 2 were set at 50, 50, and 75µV and 75, 75, and 100µV, respectively, to provide a vertical calibration scale. For these tracings, the 100-ms horizontal scale applies. For patient 3, the calibration scale is noted for 40ms and 200µV. The numbers to the left of the normal waveforms preceded by a plus or minus sign indicate the intensity of the white light stimulus in log foot-lambert-seconds. For the red and blue light responses, the numbers indicate the photostimulator intensity settings. (From Wilson DJ, Weleber RG, Klein ML, Welch RB, Green WR.³⁸ Used by permission.)