|Year : 1981 | Volume
| Issue : 3 | Page : 137-145
Department of Ophthalmology, S.N. Medical College, Agra, India
Department of Ophthalmology, S.N. Medical College, Agra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Avasthi P. Adenwala oration. Indian J Ophthalmol 1981;29:137-45
| Introduction|| |
It is a great honour that the Ophthalmological Society has given me this opportunity to deliver this memorable and great oration for for which I am highly thankful to the society. Till now it was being presented by the most eminent ophthalmologists of the country. The first receipent was Dr. S.K. Sen, next was Dr. Bhaduri, two giants in the Ophthalmic world. The medal has been offered by a parsi business man, Cawasji Adenwalla in the memory of his 22 years old son Dinshawa Adenwalla who lost his life in saving a drowning man, a great sacrifice. He was a friend of late Dr. B.A. Banaji who initiated this award. He was a opthalmologist of great repute of the country. I feel very humble and lost when I realise this great honour has been given to me.
This work was conducted for four years in S.N. Medical Collage, Agra just to find if there is any test which can diagnose preglaucomatous condition. It has been observed that most of the time provocative test failed to diagnose early cases of chronic simple glaucoma. The need of early diagnosis is of great importance because most of the people get blind from this treacherous disease glaucoma.
We usually see many cases without any symptom and suspect them glaucomatous even after so many diagnostic tests, the diagnosis is not clinched. Deep and big optic cups are often seen in normal eyes, there is no objective method of deciding whether such a cup has got any pathological significance. It is also not known whether the incidence of glaucoma is different amongst individuals with wide physiological cup and carry a poor prognosis. A study has been conducted to diagnose early glaucoma by artificially raising I.O.P. or lowering of I.O.P. Its effort on the various size of optic cup in normal, suspected glaucoma, and glucoma cases and its influence on visual fields and I.O.P. has been studied.
The exact aetiology of glaucoma is still disputed. Three important clinical features are accepted.
- Raised Intra-ocular pressure.
- Changes in Optic Nerve head.
- Visual field changes.
It is a well known fact that I.O.P. and fundus examination is often of little help. There are many eyes where field defects occur without the knowledge of the patient because the acuity of vision is maintained for a long time. Changes in the disc may take a longtime. There are cases where the I.O.P. may be very high without changes in the optic nerve or vice versa. The cause of visual field defects in primary chronic simple glaucoma is still a point of controversy.
Pickard, Syndacker classified optic cup in various ways. Armaly 8 also compared the cup disc ratio and classified in his own way. However the Pickard classification of cup disc ratio carries more information than other classifications.
This study has been conducted to assess, if the size of the optic cup has got any influence in diagnosing pre-glaucomatous condition so that early treatment can be carried out. The size of the cup was determined according Pickard X, X/4, X/3, X/2, X-2/3, X-3/4 (.3,.4, .5, .7, .8) The denomination will show the relation of the cup in horizontal width of the optic nerve.
The optic disc was examined as follows :
- The size of the cup.
- Neuro retinal element.
- Difference between the two cups.
- Neuro retinal rim.
- Lamina cribrosa.
- Presence of haemorrhage over the optic nerve.
One has got to keep in mind the blood supply of the optic nerve, in order to understand the changes in the visual field. The lamina cribrosa is supplied by the centrepetal branches of the short posterior ciliary arteries. The retro lamina] optic nerve is supplied by the centrepetal branches from the pial vessels. The posterior central artery has got a segmental distribution, nasal or temporal half or the superior or the inferior half of the choroid and optic nerve head. The changes in the optic nerve may be produced by a ischaemic factor or by the hinderance in the axoplasmic flow which may be due- to mechanical or the ischaemic causes. The raised I.O.P. or lower I.O.P. may lead to both the factors.
If the excessive pressure is applied over the eye the conduction of the nerve fibres in particular area of the retina is partially or completely obliterated depending on the severity of the compression. The arrangement of the nerve fibres at the optic disc is responsible for the development of field defects in glaucoma. Normally at the temporal parts of the disc the nerve fibres from superior and from inferior temporal parts of the retina are displaced supero temporally and infero-temporally by the inter position of the papillo macular bundle of nerve fibres, due to this arrangement the nerve fibres are affected by increased intraocular pressure sooner than the other fibres of the disc.
The object of increasing I.O.P. is to reduce the blood supply either by spasm or by mechanical means, of the optic nerve head, leading to changes in the visual field. The papillo macular bundle which produces crowding of nerve fibres superior temporally and inferior temporally gets affected by this mechanism. The main cause of field changes is due to partial obliteration of blood supply and defect in axoplasmic flow, thus leading to white and coloured field defects.
| Materials and methods|| |
Sixty eight eyes were examined in which 18 were of control group and 50 as study group. These patients were over 30 years of age and were examined in the Glaucoma clinic of S.N. Hospital, Agra.
The I.O.P, visual field of tlhese patients were plotted before the experiment. The suction cup designed on the principle of Rosegreen was applied over these eyes to raise the intra-ocular pressure and the occulopressure was applied to reduce the pressure which has been devised by us in 1968. The instrument acts as follows :
The occulo-pressure is applied over the eyes by rubber bulbs the Intraocular pressure is reduced by forcing out the aqueous under increased pressure and also the pressure causes expulsion of blood from the ciliary bed and thus reduction in the intraocular pressure. A 50 mm Hg. of pressure is maintained for 15 mts.
Raising the intraocular pressure and the lowering of intraocular pressure was conducted after an interval of one week by this time eye has returned to its original level. The intraocular tension and fields were recorded of these eyes at the interval of 5 minutes till intraocular tension and fields returned to normal.
The size of the disc and cup was measured before subjecting these patients to the study.
The gauge has get squares and area of each square is 0.1 mm. By counting the square one can measure the vertical and horizontal size of the disc and cup. Thus the cup disc ratio can beestimated by the classification according to Pickard X, X/4, X/3, X/2, X-2/2, X-3/4. The denominator will show the extent of the cup in relation to horizontal width of optic disc.
The difference of the refractive error was not more than 3 D.
| Observations|| |
A total number of 68 eyes were studied. Eighteen eyes were control of normal intraocular pressure, normal funds, normal field of vision, provocative test were negative and no family history of glaucoma. Study group consists of fifty eyes as shown. The group was divided into
Sub group A :- 10 eyes were of glaucoma suspected. They had normal anterior chamber, normal pupillary reaction and normal I.O.P. The central field were normal with 1/1000 white isopter. The disc appearance was doubtful.
Sub group B :- 10 eyes were normal and ether eye was suspected glaucoma. In the suspected cases the pupillary reaction was normal with doubtful provocative test.
Sub group C:- Includes those cases where one eye was glaucomatous but other eye showing no signs or symptoms of glaucoma. All the examinations for chronic simple
glaucoma including provocative test proved to be normal. Four eyes were studied in two patients.
Sub group D :- 12 eye were examined. One eye had frank glaucoma and other has suspicion of glaucoma without any positive tests for glaucoma but the intraocular pressure was
Sub group E:- 14 eyes were well established cases of glaucoma with raised I.O.P. and field changes.
Control group :- Consists of 11 eyes, 9 eyes were subjected to suction cup and other 9 eyes were applied occulo-pressure to raise and reduce I.O.P.
In the eyes which were subjected to the suction cup application, the maximum rise of tension was 20 mm Hg' and it was in cup discratio of X3/4 (.8). In X2/3 (.7) it was 18.5 mm. The minimum rise of tension was 17 mm. Hg. which was recorded in cup X/2 (4), X/4 (3). The minimum time taken in .3 cup was 16 mins. In cup of .7 and .5 it took 20 mins. and 18 mins. respectively to come to initial level. This indicate that bigger the cup, greater the rise of 1.0 P. and more time it takes to come to initial level.
Field Chages : 1. In X3/4 (.8) cup 7° constriction on temporal side, 7-9° on nasal side with enlargement of blind spot.
2. In X2/ (7) cup 5-8° constriction on temporal side 8-10 on nasal side. One case enlarge ment of the B.S.
3. In X/2 (.5) cup no field changes was recorded.
4. In X/4 (4) cup 5-6° constriction all round the visual field.
In no cup there was no field change. The field changes reveal that greater reduction of field occurs in bigger cup and takes more time to cane to initial level than the eyes with smaller cup.
In next group of 9 eyes in which occulopressure was applied, max. fall of I.O.P. was 14 mm Hg. the minimum fall was 8 mm Hg. It was noted that fall of I.O.P. was minimum in .8 cup and max. fall with no cup X, X/4 (3) cup. Time taken to come to initial level, max. was 40 mts and minimum was 30 mts X, .3, .5, took 40 mts to come to initial level. .7, .8 took 38 mins and 28 mains respectively to come to initial level.
Field Changes :- 1. No field change in X cup.
2. In .3 the field constriction ranged from 3-8 on temporal side.
3. In .5 in one case the constriction was 6-7° on temporal side and 9° on nasal side.
4. In X2/3-5-9° constriction on temporal side and 8-10 on nasal side.
5. In .8-0-10° constriction on temporal side and 10° constriction on nasal side with enlargement of blind spot.
This study also indicates that the greater the cup, lesser is the fall of I.O.P. and more time taken to come to initial level and greater constriction of visual fields.
Study group A :- It consists of 10 eyes of suspected glaucoma 1.0. tension was between 20 mm Hg. to 22 mm Hg. After the suction cup application the max. rise of tension was 26.2 mm Hg. and minimum rise was 10 mm Hg.
1. In .3, rise ranged from 10 mm Hg. to 16.5 mm Hg.
2. In .5, rise was 16.5 mm Hg. to 21 mm Hg.
3. In .7, rise was 18 mm Hg. to 22 mm Hg.
4. In .8, rise was 26.2 mm Hg.
Time taken to come to initial level in .3 cup was maximum 26 nits. and .8 cup was 30 nits.
Field Changes' : 1. In .3 cup it ranged from 2-4° constriction on temporal side 2-7° on nasal side. One case has enlargement of blind spat.
2. In .5 cup temporal constriction varied from 2-15° and nasal constriction varied from 2-12° on case had enlargement of blind spot and other cases there was baring of the blind spot. In one case there was no field change.
3. In .7 cup one eye showed sickle shaped enlargement of blind spot in rest temporal constriction was 2-7° on nasal side.
4. In .8 cup one case showed baring of the blind spot. temporal constriction was 12-13° and nasal temporal constriction was 12-14°. In all the cases field returned to normal alongwith I.O.P. except in 2 cases which took 10-11 nits. more than the tension to come to its initial level later they showed glaucomatous changes.
The occulo-pressure study in 10 cases the max. fall of I.O.P. was 14 mm of Hg. and min fall was 1 mm of Hg. In .3 average fall 11.7 mm of Hg., .5,-11.5 mm of Hg.. 79.8 mm of Hg. and .8-10 mm of Hg. respectively. The fall is minimum in the ratio of .7, .8 and max. was in .3 and .5. Time taken to come to normal was 40 mts. and 25 rats. .3 took on average 25 rms. one case took 35 nits. with sickle shaped in enlargement of blind spot.
Field Changes :- In .3-two cases no field changes. In another case there was enlargement of blind spot, in another there was baring of blind spot, and in rest the field constriction was 2-4° on both nasal and temporal side.
In X/2 (.5)-Field construction varied from 1-10° in temporal side.
In X2/3 (7)-in two cases the constriction was 10-10° on tempo side and 11-15° on nasal side, there was baring of the blind spot.
In X3/4 (8) there was a constriction of field 9-13 on temporal side 11-13° on nasal side.
Group B :- 10 eyes were studied, (5 suspected eyes). In 5 normal eyes the suction cup was applied and the max. rise of tension was in X3/4 (.8) i.e. 18 mm Hg. In X/4 (.3) it was 12 mm Hg. More time was taken by the greater cup to conic to initial level it was 30 rots. and smaller cup took 15 mts. to come to initial I.O.P. Field Changes:- In two casess there was
no field changes. In one case there was enlargement of blind spot with sickle shaped changes. In two cases there was baring of the blind spot. Cases with X3/4 (.8) the field constriction was 7-13° on temporal side and 7-12° on nasal side, baring of the blind spot in both the case.
Suspected Cases :- 5 eyes were examined After suction cup the max. rise of I.O.P. was 17.5 mm Hg. and min. was 10 mm of Hg. It was observed that max. rise was in X3/4 (.8) and X2/3 (7) Time taken to come to initial level by X3/4 (3) it was 22 nits.
Field Changes :- In one case with X2/3 (7) there was no field changes. In X3/4 (.8) the field constriction was 1-11° on temporal side and 2-13 on nasal side with baring of blind spot. In two cases one of .4 and other .3 there was enlargement of blind spot and one case there was baring of the blind spot. Field returned to normal in all cases except in 2 eyes which took 4-6 rots more than the I.O.P. These eyes belonged to X 3/4 (8) and .7 cup later on in these eyes registered rise of I.O.P. with glaucomatous changes.
After application of occulo pressure in normal cases the fall of I.O.P. was 13 mm of Hg. Max. fall was in X/4 (.3) cup and minimum fall was .8 cup and .8 cup took 30 ants to come to initial level. Field Changes :- In X/4 (8) cup was 5-9 on temp. side and 7-9 on nasal side and in the rest X12 (.5),-enlargement of blind spot and X/4 (3)-the baring of the blind spot the field changes E.B.S. The field returned to normal with I.O.P.
In suspected cases after O.P. the fall was 13-9 mm of Hg. the max. fall was in smaller cup and minimum fall was in large cup. The larger cup took 40 nits and smaller cup took 25 mts to come to initial level. No field changes in one case of X/3 (4) group noted. In X3/4 (8) and X/3 (7) the field constriction varied from 9-13° on temp. side and 10-15 on nasal side with baring of blind spot and enlargement of the blind spot.
Sub Group C:- Four cases were examined, two were normal and two were glaucomatous.
Two normal eyes :- After suction cup application max. rise of I.O.P. was 20.5 mm Hg. and minimum rise was 17.5 mm Hg. The max. rise was in X3/4 (8) and minimum was in X/2 (8) and X3/4 (.8) took 29 mm to come to initial level and X/2 took 17 mins to come to initial level of I.O.P. The constriction of field was 5-8° on temp. side and 7-10° on nasal side. Greater constriction was present in X/4.
In 2 glaucomatous eyes, after suction cup, rise was 34.4 mm Hg. and 19 mm Hg. It took 25 mins to 20 mins respectively to come to initial level of I.O.P.
Field Changes :- In one case there was enlargement of blind spot and in 2nd case constriction of field was 6-7° and baring of the blind spot.
After O.P. pressure, in the normal eyes max. fall was 11 mm in Hg. X/2 cup, and 9 mm Hg. fall was in X3/4 cup. Time taken to come to normal level was 30-32 mts. respectively. In X/2 there was no field changes, In X3/4 the field constriction was 2-5° in all sides.
In glaucomatous cases, the fall was 6 mm Hg. to 4 mm Hg. both the cases. Time taken to come to normal was 18-16 mts. respectively constriction of field was 2-4° with enlargement of blind spot and other was normal.
Group D :- Twelve cases were examined in in consists of glaucomatous and suspected glaucoma cases.
After suction cup application in glaucoma cases max. rise was 35 mm .Hg. and minimum rise was 10 mm Hg. The max. rise in X3/4 (.8) suction cup application was not tolerated by these patients on an average more that 12 nits. time taken to come to initial level was 32 mts. In all glaucomatous cases, field constriction was present on nasal side with baring of the blind spot. In one case with cup X3/4 (8) there was no field changes.
In X/2 cup 5° constriction present with baring of blind spot. X2/3 (.7) 6-9° constriction present with baring of blind spot. X2/3 (7) 6-9° constriction was present with baring of blind spot. In X3/4-5-9° constrictoin was present. In all cases there was barring of the blind spot after the application of the suction cup.
In suspected 6 cases the max. rise was 35.5 mm Hg. and minimum rise was 22.5 mm Hg. These patients could tolerate suction cup application on average 14.3 ruts. Time taken to come to normal 40.5 mts. and 24 nits. Maximum time taken was by X3/5 (.8) cup and minimum was by X12 (.5) cup.
Field Changes:- In X/2 was 2-4°, in X2/32-5°, X3/4 it was 2-7° there was greater constriction of field in bigger cup, field returned to normal in all cases. except in 2 cases which took 5 and 10 mins more than the initial I.O.P. These patients belongs to .8 cup later they became frank glaucomatous cases,
After oculo-pressure application in glaucomatous cases, max. fall of I.O.P. was 10 mm Hg. minimum fall was 4 mm Hg. Minimum fall was in X3/4 (-8) and max. fall was in X/2 (.5) Time taken to come to normal was 17 mts. and 15 ruts. respectively. In X3/4 (8) all cases, baring of the blind spot developed after the application of O.P.
In X2/3 (7) baring of blind spot and construction of field was 5-6°.In X/2 (.5) constriction of field was 4-9° on temporal side 3-6° on nasal side and baring of blind spot was present.
In suspected eyes the fall of I.O.P. was 12 mm Hg. and 9 mm Hg. The max. fall was in X2/3 (7) X/2 (.5). Minimum was in X/2 (.5) X3/4 (8) cup and took 35 mins. to come to initial level. X/2 (5) took 25 mins. to cone to initial level.
Field Changes :- In X/2 (5) constriction was 6-9° one case there was enlargement of the blind spot., X2/3 (7) constriction was 6-9°, X2/3 (7) there was enlargement of blind spot in one case and in another case the constriction of the field was 6-7° but field returned to initial level with I.O.P.
Sub Group E:- Consists of 14 eyes were all established glaucoma. After suction UP application max. rise o I.O.P. was 35.5 rnm Hg. and minimum rise was 27 mm Hg. In one case of X3/4 there was no rise of I.O.P. probably due to wrong application of the suction cup otherwise max. rise in X3/4 (8) cup and minimum rise was in 27.5 mm Hg. and X/4 (3) and X3/4 (.8) cup took 30 to 40 mins. to come to initial I.O.P. X/4 (.3) and X/2 (5) took 28 to 30 mins. to come to initial level.
Field Changes :- In X there was enlargement of blind spot. in X/4 the constriction of field was 8-10° from its initial level. In two cases there was enlargement of blind spot. In one case there was sickle shaped enlargement of blind spot. In X/2 the constriction was 1-10° on temporal side and 3-10° on nasal side from the initial level with baring of blind spot. in one case.
In X3/4, in one case there was no rise of tension and there was constriction of field 2-4°. In cases there was enlargement of blind spot. The field constriction varied from 2-8° on temp. side and 3-6° on nasal side from its its initial level.
After occulo-pressure the max. fall was 12 mm Hg. and minimum fall was 4 mins, the max. fail was observed in X cup and minimum fall was in X3/4 (8) the I.O.P. returned to initial level in no cup took 21.7 mins. .3 cup 16.5 mins, 5 cup took 15 mins and 0.8 cup took 20 mins. respectively. The fall of I.O.P. was less in greater cup and took more time to come to initial level.
Field Changes:- The field constriction was present in all cases baring of blind spot developed in all cases.
| Discussion|| |
The object of increasing or reducing I.O.P. is to reduce the blood supply either by spasm or by mechanical means, of the optic nerve head or expelling out aqueous through the angle of filteration, thus affecting the Intraocular pressure leading to changes in the visual fields. The papillo macular bundle, which produces crowding of nerve fibres superioro temporally and inferioro temporally get affected by this mechanism. One main cause of the field changes is due to partial obliteration of blood supply and defect in axo-plasmic flow, leading to white colour field defect. The steepness of the ages of the scotoma indicates that one bundle is eliminated before the next is effected. The group of fibres in the neighbourhood of vascular trunks are usually first involvei. It is angioscotoma which involves into Bjerrum scotoma.
Moreover the field defects are pathogenomic of glaucoma but also are mimicked by a wide variety of vascular lesions, particularly of obliterative nature affecting the visual path ways anterior to the lateral geniculate body. The initial glaucomatous effects are thus due to vascular insufficiency and axo-plasmic defects and may be reversible. If ischaemia persists, degeneration of nerve fibres leads to the development of permanent defects. In our cases, we produce the sudden rise and fall of I.O.P. leading to vascular in sufficiency which may be the cause of field defects in these eyes or due to the hindrance in axo-plasmic flow.
The suction cup raised I.O.P. it was applied for 15 mts. and the pressure maintained at 50 mm Hg. Some patients failed to tolerate the application of suction cup for 15 mints and in some the pressure shot up more quickly than the others. The I.O.P. was reduced by the O.P. which was designed by us This was also applied for 15 mts machanism of the field defect in the same.
After the application of suction cup :- In control group the rise of I.O.P. was 20 mm Hg. in bigger cups, and minimum rise was 17 mm Hg. smaller cups. The bigger cup took 32 mts to come to initial I.O.P. in smaller cup it come in 17 mts to initial level. The optic disc which had no cup had no field changes. After application of O.P. there was no field change in the eye which had no cup, less field changes in smaller cups but in bigger cup the constriction was in the range of 9-10°. The fall of I.O.P. was minimum in bigger cup and maximum in smaller cups. Larger cup took more time for the I.O.P. to come to initial level in comparison to smaller cup.
In suspected cases of glaucoma in .5 cup the field was markedly constriction and after 1 year of follow up it turned out to be glaucomatous. In 2 cases of .7 cup there was sickel chapped enlargement of blind spot. It too turned out to be glaucomatous later on. In rest of the cases of bigger cup there was a marked constriction of field due to rise of I.O.P. The bigger cup in these series showed the rise of I.O.P. i.e. 22.2 mm Hg. While 3 cases in the group could not tolerate suction cup for the 15 mins. In 2 cases out of these field of vision took 10-11 mts more than the I.O.P. to come to its initial level. All these cases turned out to be glaucomatous later on. After the application of O.P. the findings were almost the same as with suction cup but in reverse way.
In B group cases, 5 suspected cases, again the max. rise of I.O.P. was in larger cups and minimum was in smaller cups. Larger cup took 29 mins to come to its initial level while smaller cup took 20 mins to come to its initial level. In all cases deld returned normal with I.O.P. except 2 cases which took 4-6 mins more than the initial I.O.P.
Both they could not tolerate suction cup for 15 mins. These eyes later on turned out to be glaucomatous. After application of O.P. findings were almost the same as that of suction cup.
In Group C, 2 eyes were glaucomatous and 2 were normal. In glaucomatous eyes the max. rise of I.O.P. was 34.5 mm Hg. and minimum was 28 mm Hg. and took 20-25 mts to come to its initial and there was also marked field changes in both the eyes while in normal eyes the max. rise was 22.5 mm Hg. and minimum was 17.5 mm Hg. and took 17 mts to come to its initial level. Constriction of field was less than glaucomatous cases. This shows that the changes in glaucomatous eyes becomes more prominent after rising or reducing I.O.P.
In Group D, one eye was glaucomatous and another was suspected glaucoma. In glaumatoes cases, suction cup could not be tolerated for more than 12 mins and all of them showed marked field changes while in suspected cases the patient could tolerate suction cup for 14.3 mts. Glaucomatous cases took much less time for I.O.P. to come to its initial level than suspected cases e.g. glaucomatous casestook mts and suspected cases took 40.5 mts.
The suspected cases which could not telerate suction up also turned out to the glaucomatous later on. Amongst suspected eyes in one eye there was change of blind spot without any constriction of field. In rest of the eyes field construction was as that of control group. The observation by O.P. was also the same.
In Group E, of cases of glaucoma 14 eyes did not tolerate suction cup application for 15 mts.
In 4 eyes field became tubular. In one case there was sickle shapped enlargement of blind spot. Max. rise of I.O.P. was noticed in .8 cup time taken to come to its initial level was more in bigger cup. After O.P. application 13 eyes showed changes in blind spot. In 5 eyes field become tubular and there was uniform constriction of field in all cases and more marked in .8 cup. minimum fall of I.O.P. was in larger cup.
| Summary and conclusions|| |
In the effect of artificially raising and lowering intra-ocular pressure on visual field was observed. For raising the intra-ocular pressure perilimbal suction and for lowering tension, occulo pressure was used. The study was carried out on 68 human eyes, including 18 normal eyes acting, as control group. The remaining 50 eyes were of glaucomatous and glaucoma suspects.
The artificially raising intraocular pressure causes constriction of central field, even in control group.
The constriction of field in almost all the control eyes, was never extensive so at to cause baring of the blind spot in suction cup. The field constriction bccomes more as the cup disc ratio increases.
In pre-glaucomatous eyes, the raised intraocular tension lead to extensive temporary field defects which were otherwise not detectable.
The field changes were due to anoxaemia produced by raised intraocular tension.
In pre-glaucomatous eyes the rate of rise of tension was rapid and fall of tension was slow as compared to control eyes.
The principle of action in occulo-pressure was same as that of suction cup that is ischaemia and anoxia. The field constriction in cases of normal, suspected and glaucomatous are same as that of suction cup, but otherwise, the fall of tension, recovery period in normal, suspected and glaucomatous eyes are reverse as that of suction cup and also in cup disc ratio.
This study concludes that the pre-glaucomatous conditions can be diagnosed much earlier than by any other provocative test.
- If the field constriction after application of suction cup or the O.P. reduction is more than 10° and changes in the blind spot and the reversal of visual field take more time than I.O.P. are more prone to glaucoma.
- Another interesting point which this study has revealed that if the size of the physiological cup is more than 0.6 of the optic disc, the disc is vulnerable for pathological changes. Greater the cup greater the patho logical changes of optic nerve and visual fields if the 1.0. tension is raised.
It has also been observed that eyes which do not allow the suction cup for 15 mins due to severe pain, they are pre-glaucomatous even if the fields and I.O.P. is normal.
Eyes where field does not return to normal with I.O.P. are potenially pre-glaucomatous. It is concluded that eyes with larger cup should be kept under observation for raised I.O.P. as these eyes shall not be able to stand the raised pressure for long without the pathological changes in the optic nerve and loss of visual fields.
| References|| |
Pickard, C., 1948, Brit. J. Ophthalmol., 32: 355.
Snydack, F., 1964, Amex. J. Ophthalmol., 58: 958.
Armaly, M.F., 1967, Arch. Ophthalmol., 78: 35.