Ординатура / Офтальмология / Английские материалы / Electrodiagnosis of Retinal Disease_Miyake_2005

References

1.Stargardt K (1909) Über familiare, progressive Degeneration in der Maculagegend des Auges. Graefes Arch Ophthalmol 71:534–550

2.Franceschetti A (1965) A special form of tapetoretinal degeneration: fundus flavimaculatus. Trans Am Acad Ophthalmol Otolaryngol 69:1048–1953

3.Noble KG, Carr RE (1979) Stargardt disease and fundus flavimaculatus. Arch Ophthalmol 97:1281– 1285

4.Allikmets R, Singh N, Sun H, Shroyer NF, Hutchinson A, Chidambaram A, et al. (1997) A photoreceptor cell-specific ATP-binding transporter gene (ABCR) is mutated in recessive Stargardt macular dystrophy. Nat Genet 15:236–246

5.Fish G, Grey R, Sehmi KS, Bird AC (1981) The dark choroid in posterior retinal dystrophies. Br J Ophthalmol 65:359–363

6.Steinmetz RL, Garner A, Maguire JI, Bird AC (1991) Histopathology of incipient fundus flavimaculatus. Ophthalmology 98:953–956

7.Gass JDM (1997) Stargardt’s disease (fundus flavimaculatus). In: Stereoscopic atlas of macular diseases: diagnosis and treatment. Vol 1. Mosby, St. Louis, pp 326–333

8.Miyake Y (1988) Study on local macular ERG. Acta Soc Ophthalmol Jpn 92:1419–1449

9.Martinez-Mir A, Paloma E, Allikmets R, Ayuso C, del Rio T, Dean M, et al. (1998) Retinitis pigmentosa caused by a homozygous mutation in the Stargardt disease gene ABCR. Nat Genet 18:11–12

10.Fukui T, Yamamoto S, Nakano K, Tsujikawa M, Morimura H, Nishida K, et al. (2002) ABCA4 gene mutations in Japanese patients with Stargardt disease and retinitis pigmentosa. Invest Ophthalmol Vis Sci 43:2819–2824

11.Maugeri A, Klevering BJ, Rohrschneider K, Blankenagel A, Brunner HG, Deutman AF, et al. (2000) Mutations in the ABCA4 (ABCR) gene are the major cause of autosomal recessive cone-rod dystrophy. Am J Hum Genet 67:960–966

Best’s disease (vitelliform macular dystrophy) is an autosomal dominant, pleomorphic, progressive disease of the RPE with an onset early in life [1]. The unique fundus appearance (Fig. 2.143) is used to classify the stages: previtelliform, vitelliform, pseudohypopyon, vitelliruptive, and atrophic [2]. The OCT images show a solid substance underneath the RPE in the macula (Fig. 2.143). The visual prognosis is relatively good, and most patients retain reading vision in at least one eye throughout life. The progression of the visual acuity reduction is slow and begins for the most part after the age of 40 years [3].

The full-field ERGs are normal at all stages [4], but as shown in Fig. 2.144, the focal macular ERGs are slightly to moderately reduced, indicating that only the macula is affected. However, as shown in Fig. 2.145, the EOG is markedly abnormal, with the light-to-dark ratio usually less than 1.50 [5]. The EOG ratios of the carriers of the disease are also usually subnormal [5]. In 1998 a mutation of the VMD2 gene was identified as causing Best’s vitelliform macular dystrophy [6].

Adult-onset foveomacular vitelliform dystrophy [7] may show similar ophthalmoscopic findings in the macula. The lesion is symmetri-

cal, solitary, usually one-third to one disk diameter in size, round or oval, slightly elevated, yellowish, and subretinal. There is often a central pigmented spot in each eye (Fig. 2.146). The patients may be visually asymptomatic or have mild visual blurring and metamorphopsia in

one or both eyes, usually with an onset between ages 30 and 50 years. The full-field ERGs and EOGs are essentially normal. The normal EOG is a key differential point between Best disease and adult-onset foveomacular vitelliform dystrophy.

References

1.Best F (1905) Uber eine hereditare Maculaaffection: Beitrag zur Vererbungslehre. Z Augenheilkd 13: 199–212

2.Gass JDM (1977) Stereoscopic atlas of macular diseases; diagnosis and treatment, 2nd edn. Mosby, St. Louis, p 162

3.Fishman GA, Baca W, Alexander KR (1993) Visual acuity in patients with Best vitelliform macular dystrophy. Ophthalmology 100:1665–1670

4.Kondo M, Kondo N, Tanikawa A, Horiguchi M, Miyake Y, Awaya S (1997) Clin Rev Ophthalmol Jpn 91:313–317

5.Deutman AF (1969) Electro-oculogram in families with vitelliform dystrophy of the fovea: detection of the carrier state. Arch Ophthalmol 81:305–311

6.Marquardt A (1998) Mutations in a novel gene, VMD2, encoding a protein of unknown properties cause juvenile-onset vitelliform macular dystrophy (Best disease). Hum Mol Genet 7:1517–1525

7.Bloom LH, Swanson DE, Bird AC (1981) Adult vitelliform macular degeneration. Br J Ophthalmol 65:800–801

Diabetes mellitus is a heterogeneous disorder of carbohydrate metabolism with multiple etiological factors that ultimately lead to hyperglycemia. Diabetic retinopathy is a disease of the retinal blood vessels that develops in the complex metabolic milieu of systemic diabetes mellitus. Because of the multiple factors, the electrophysiological abnormalities are complex, and the changes are often difficult to interpret.

In early studies, the oscillating potentials (OPs) of the electroretinograms (ERGs) were

found to have reduced amplitude [1] and delayed timing during the early stage of the disease (Fig. 3.1). Reduced b-wave amplitudes were reported only in eyes with fairly advanced retinopathy.

In this chapter, three relatively new studies on diabetic retinopathy are examined: ERGs after panretinal photocoagulation, ERG evaluation of vitrectomy candidates with diabetic retinopathy, and analysis of diabetic maculopathy using focal macular ERGs and OCT.

Panretinal photocoagulation (PRP) is often applied to diabetic eyes at the preproliferative or proliferative diabetic retinopathy stage (Fig. 3.2). Although the mechanism for improving retinal function after PRP has not been conclusively determined, its efficacy has been thoroughly documented in randomized clinical trials. The rationale initially proposed for the regression of new vessels following PRP was that the ischemic retina, which was postulated to be producing a vasoformative factor, was destroyed. Another explanation was that the retinal pigment epithelium (RPE) cells that were producing a vessel-inhibiting factor were destroyed. It has also been proposed that PRP

may improve oxygenation of the ischemic inner retinal layers by destroying some of the metabolically highly active photoreceptor cells to allow the oxygen normally diffusing from the choriocapillaris to the photoreceptors to continue into the inner retina.

In any case, the amplitudes of the full-field ERGs are reduced after PRP in eyes with diabetic retinopathy. The degree of reduction of the ERGs after PRP relative to that before PRP is shown in Fig. 3.3. In our study [2] the means of the a-waves and b-waves are reduced by 44% and 41%, respectively. The b-wave/a-wave (a/b) ratio is slightly increased after PRP, but the increase is not significant. The OPs are

markedly reduced or not present before PRP in most patients. However, if they are present, they become undetectable after PRP.

The macula is spared from photocoagulation during PRP (Fig. 3.2), but the question arises whether PRP affects macular physiology. Decreased consumption of oxygen in the extensively coagulated retina may lead to increased oxygen supply to the noncoagulated areas of the macula. On the other hand, some patients suffer from macular edema following PRP. Fullfield ERGs and focal macular ERGs before and after PRP are compared in Fig. 3.4, with special emphasis on the OPs [2, 3]. Following PRP, the OPs of the full-field ERGs are reduced in amplitude to nearly undetectable levels. However, the OPs of the focal macular ERGs, elicited by three differently sized stimuli, were not reduced. The amplitudes of the b-waves of the focal macular ERGs elicited by a 15° spot in a large series of

patients before and after PRP are compared in Fig. 3.5 [3]. The amplitude of the b-wave after PRP is expressed as a percentage of that before PRP. To determine the variations in the focal macular ERGs in normal control subjects, the amplitude of the b-wave of the focal macular ERGs of normal subjects from two recordings at different times were compared. The variation in the focal macular ERGs in normal subjects was small. On the other hand, the interindividual variations in the amplitudes of the focal macular ERGs after PRP were large, with some showing a decrease and others an increase. The decrease and increase (average of amplitudes) were not statistically significant.

These results suggest that PRP alters the macula of eyes with diabetic retinopathy in various ways, and it may either improve or worsen macular function.