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Year : 1983  |  Volume : 31  |  Issue : 3  |  Page : 115-118

Investigative procedures in heredomacular degeneration


Dr. Rajendra Prasad Centre for Ophthalmic Sciences, A.I.I M.S., New Delhi, India

Correspondence Address:
P K Khosla
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, A.I.I M.S., New Delhi
India
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Source of Support: None, Conflict of Interest: None


PMID: 6676193

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How to cite this article:
Khosla P K, Gahlot D K, Tewari H K. Investigative procedures in heredomacular degeneration. Indian J Ophthalmol 1983;31:115-8

How to cite this URL:
Khosla P K, Gahlot D K, Tewari H K. Investigative procedures in heredomacular degeneration. Indian J Ophthalmol [serial online] 1983 [cited 2024 Mar 29];31:115-8. Available from: https://journals.lww.com/ijo/pages/default.aspx/text.asp?1983/31/3/115/29762

Diagnostic investigations in a disease pro­cess become extremely important particularly when therapy does not lead to relief. Heredo­macular degenerations fall into such a category. These are bilaterally symmetrical degenerations of macula with varied clinical course and here­ditary predisposition. These usually manifest coinciding with ages of physiological stress hence fall into categories like infantile, juvenile, adult, presenile and senile.

Macular degeneration or maculopathy is a "Waste basket" diagnosis given in cases of diminution of vision with or without the pre­sence of objective macular findings. Fluorescein angiography and electrodiagnostic parameters like electroretinography (E.R.G.) and electro­oculography (E.O.G.) help in differential diagnosis.

This study reports fiuorescein angiography in cases of macular degeneration (ostensibly heredomacular) and electrodiagnostic para­meters of cases showing pigment epithelium "window defect" indicative of atrophy of pig­ment epithelium.


  Methods and Materials Top


Patients diagnosed as macular degeneration, attend­ing the Retina Clinic of Dr. Rajendra Prasad Centre for Ophthalmic Sciences were taken up. The clinical picture included progressive painless diminution of vision (usually below 6/24 in better eye) of several year dura­tion, clear media and macula showing pigment mottling with occasional metallic sheen and dull foveal reflex. Complaint of defective dark adaptation was noted. Cases with good vision (6/12 or 6/18) but not improving with glasses or pinhole were also included. Cases with classical picture of central choroiditis or having other pathology in the fundus were excluded.

Fluorescein angiography was done using Zeise fundus camera after injection of 3 cc of 20% fluores­cein sodium in the antecubital vein.

E.R.G. was done simultaneously in both eyes using contact lens electrodes on Grass PS 22 pnotostimulator and Mingograph 800 both in light and dark adaptation essentially according to Karpe's method. Electrooculo­graphy was done by the method of Gahlot and Hansen (1974) and LP/DT ratio of 175 or less was considered abnormal.


  Results Top


[Table 1] shows the age and sex distribution of cases undergoing either fluorescein angio­graphy alone or electrodiagnostic tests alone or both.

Results of fluorescein angiography show that 5 cases (2.6%) turned out to be healed choroiditis. 28 cases (14.7%) showed normal angiograms and were designated as either post central serous retinopathy degeneration if vision was grossly disturbed or idiopatic macu­lar pigmentation if vision was grossly disturbed or idiopathic macular pigmentation if vision was not grossly disturbed. 7 cases (3.6%) show­ed even leakage indicative of central serous retinopathy but the macular oedema was mini­mal to misdiagnose it as macular degeneration. 22 cases (19.5%) were designated as colloid degeneration if the hyperfluorescent areas were discreet and vision was not grossly disturbed. Only 128 cases (67.3%) showed "window defect" and were diagnosed as heredomacular degene­ration of various types.

Out of 130 cases, E.R.G. and E.O.G. could be done in 81 cases while in rest either E.R.G. was possible alone (18 cases) or E.O.G. alone (31 cases). In 17 cases due to various reasons E.O.G. and E.R.G. was abnormal. 14 cases showed E.O.G. abnormality but no change in E.R.G. 2 cases showed abnormal E.R.G. but normal E.O.G. Abnormal E.R.G. was seen in 30 out of 99 (30.3%) while E.O.G. was abnor­mal in 43 out of 112 cases (38.3%). In 45 cases both E.R.G. & E.O.G. were normal.


  Discussion Top


Macular degeneration is a "Waste basket" diagnosis since this may be caused either by factors affecting the macula alone or as a part of generalised retinal degeneration. Hence sophisticated investigative procedures are need­ed for its differential diagnosis. Heredomacular degenerations fall into the former category and are the basis of our study.

Fluorescein angiography has emerged as a very useful diagnostic tool. Densely packed pigment in pigment epithelium in the macular area blocks choroidal fluorescence hence its visibility is inversely proportional to pigment concentration. "Window defect" which shows up in prearterial phase coincidental with filling of choroid is a transmitted fluorescence. It re­aches peak in arteriovenous phase and then dis­appears as dye disappears from choroid. It does not show change in its size or shape and does not appear late in the angiogram. It is, there­fore, accentuation in the visibility of choroidal fluorescence due to absence of pigment in pig­ment epithelium, either due to congenital reduction or atrophy.

Bilaterally symmetrical presence of "window defect" diagnostic of heredomacular degene­was seen in 128 cases which was either round (45 cases) or oval (72 cases) and well circum­scribed with advanced stage of disease. In some (11 cases) there were multiple areas of atrophy which might become confluent after a period of time. Large choroidal vessels were seen in 8 cases and were due to loss of pigment epith­elium and choriocapillaris.

22 cases showed hyperfluorescent spots simulating "Window defect" but not corres­ponding exactly to the dye in the choroid. The hyperfluorescence remained for a longer time although it did not increase in intensity or extent. The vision was within normal limits. Clinically these showed colloids in the corres­ponding area hence were diagnosed colloid macular degeneration with consequent good prognosis.

28 cases showed normal angiography find­ings although clinically pigment mottling was seen. Out of these 8 cases showed gross dimi­nution of vision with a previous history sugges­tive of macular oedema and were labelled as post central serous retinopathy. 8 cases showed vision 619 or better. Electrodiagnostic investi­gations were done in these cases to rule out generalised retinal dystrophy. In absence of any disturbed parameter, these were labelled as idiopatic macular pigmentation. 12 cases were however put as retinitis pigmentosa on basis of abnormol electrophysiological parameters.

7 cases were diagnosed as macular degene­ration (without any oedema) but turned out to be early stage of central serous retinopathy with leakage.

5 cases turned out to be old heald choroi­ditis showing a central hyperfluorescent area bordered by pigmentation. Clinically pigment­ation was present but the central atrophic area was not clearly demarcated. It is our conten­tion that some cases of macular oedema which are passed off as central serous retinopathy were really central choroiditis which healed spontaneously or by treatment. Investigations in these cases may identify an aetiological factor which may be treated to save the other eye. Visual prognosis, however, is poor in these cases.

Application of eiectrodiagnostic techniques is helpful for objective determination of func­tion. It is likely to be more useful either in (i) small children where psychophysical tests are not reliable or in (ii) cases where there is discrepency between anatomical findings and psychophysical functions, and probably can safely predict prognosis in various retinal dis­orders. E.R.G. is said to reflect the activity of nervous retina while E.O.G. mainly shows up the pigment epithelium damage, so it is better to carry out both as one may compliment the other and as such in primary hereditary pig­ment dystrophies electrophysiology may be more disturbed than psychophysical function tests. Both are, however, mass responses of the entire retina and may not show any abnor­mality if only a small area of retina as macula alone is involved. Hence its value will mostly be corroborative in macular lesions.

In 17 cases, both E.O.G. and E.R.G. were grossly abnormal. These cases were diagnosed as cases of retinitis pigmentosa inversus as these complained of defective dark adaptaion also. Hence it is suggested that cases with defective dark adaptation and even dubious macular findings must be subjected to electro diagnostic tests to rule out primary retinal dystrophies. Some of the cases were those in­cluded in our previous study which on follow up have developed more fundus changes com­mensurate with retinitis pigmentosa.

However, some authors believe that Star­gardt's disease may present as reduced E.O.G. and Scotopic E.R.G. with typical macular findings but with changes in periphery. We however feel that these cases should be put under primary retinal atrophies like retinitis pigmentosa.

No case of sex linked cystoid foveal dys­trophy was seen where E.O.G. as well as receptor potential in E.R.G. (a wave) is said to be normal but post receptor potential (b wave) is lowered.

In 14 cases E.R.G. was normal and only E.0 G. was disturbed. These were classically put under the category of heredomacular degeneration although only 2 cases were dia­gnosed as a typical vitelliform dystrophy as disturbances of deep retinal layers lower the E.O.G. while E.R.G. remains normal.

In 45 cases both E.R.G. and E.O.G. were normal. These cases showed either colloid degeneration of macula or idiopathic macular pigmentation with minimal diminution of vision with probably a better prognosis. Some of these may well later turn out to be cases of Star­gardt's disease as there is no real typical picture and E.O.G. and E.R.G. may not be affected in early cases. 7 cases fall in the category of senile macular degeneration with E.R.G. and E.O.G. normal. It confirms the contention that electro­diagnostic tests may not provide additional information for diagnosis and as such a normal E.R.G. in cases with media opacities may not exclude a macular degeneration.

A combination of abnormol E.R.G. and normal E.O.G. is not usual & was seen only in 2 cases which indicates that E.O.G. probably is affected first. E.O.G. was affected in 47 cases (42%) while E.R.G. was only affected in 30 cases (30%) indicating that E.O.G. may be a better parameter for evaluation of heredo­macular degeneration.


  Summary Top


It is indicated that fluorescein angiography helps to sift other pathologies from degene­rative pathology of macula while electrodia­gnostic procedures help in giving the prognosis worse where E.R.G. alone or along with E.O.G. is grossly abnormal guarded, where E.O.G. only is disturbed and good where both E.R.G. and E.O.G. are normal.




 

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