|Year : 1982 | Volume
| Issue : 4 | Page : 319-321
Orbital mycosis an attempt to evolve an experimental model
Y Dayal, VM Mahajan
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, New Delhi, India
V M Mahajan
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, A.I.I.M.S. New Delhi-29
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Dayal Y, Mahajan V M. Orbital mycosis an attempt to evolve an experimental model. Indian J Ophthalmol 1982;30:319-21
|How to cite this URL:|
Dayal Y, Mahajan V M. Orbital mycosis an attempt to evolve an experimental model. Indian J Ophthalmol [serial online] 1982 [cited 2020 Jun 1];30:319-21. Available from: http://www.ijo.in/text.asp?1982/30/4/319/29462
Fungal lesions of the orbit occur chiefly as orbital aspergillosis or orbital phycomycosis. Phycomycosis is invariably fatal following an extensive damage to the brain while aspergillus is not always so. This is an endeavour to evolve experimental models for these two entities.
| Materials and methods|| |
Experimental procedure (Aspergillosis)
Thirteen Indian rhesus monkeys were inoculated into the maxillary sinus by Caldwell Luc procedure as follows : (i) Four animals, each received 0.5ml of a suspension (12%106 spores per ml) of A flavus, (ii) Four received 0.5 ml of suspension of A. flavus and 0,5ml of S. aureus., (iii) Five animals received a suspension of A. flavus (0.5m1 each) and 24 hours after 0.2ml of Betnesol (Glaxo) containing 4 m,-,m of b2tamethasone per ml was administered intramuscularly.
(i) Sixteen rabbits weighing about 2 Kg were inoculated in the right orbit with 0.1 ml of spore suspension (10 6 spores per ml) through the rubber conjunctiva (ii) Four of them were given decadron (0.4mg/kg weight) intramuscularly daily, on 2 days prior to inoculation of Rhizopus oryzae and for 5 days afterwards, (iii) Another 4 animals were injected with spores, soon after diabetes was produced by a single injection of alloxan monohydrate (150mg/kg body weight), (iv) Six animals were made acidotic before inoculating the fungus3, (v) Two more were given no further treatment following spore inoculation.
| Observations and discussion|| |
Aspergillus flavus was especially chosen for this study because it is the fongus in a majority of the clinical cases. Our study has shown that the spores remained viable in the maxillary sinus for as long as 75 days, but were nonpathogenic. The fact that both cocci and fungus remained viable for over 60 days implies that the fungus could not establish itself even on the inflammed mucosa of the sinus.
In five animals, steroids were given but it is possible that the brevity of their administration resulted in their inability to impair the resistance adequately to allow the establishment of the fungus. We succeeded in introducing fungal spores in the orbit of some animals. Though they remained viable for 30 days, they did not produce any pathological changes. It is possible that the prolonged use of steroids or cytotoxic drugs or the employment of other means of lowering local or general body resistance will be successful.
Direct implantation of Rhizopus spores into the orbit was resorted to because of the short life of diabetic acidotic rabbits though this is not the usual mode of entry for the fungus, in clinical cases.
In this study spores failed to survive for 60 days in the orbit of healthy rabbits. On diabetic rabbits, fungus proliferated in retroocular tissues [Figure - 1][Figure - 2] but it was more invasive in acidotic animals and involved sclera, choroid and episclera. [Figure - 3] It also surrounded the blood ?vessels, possibly in an attempt to invade them. Retro-ocular mass could be formed only in diabetics. This mass showed areas of necrosis and formation of a fungal granuloma. In acidotic animals, neither the mass, nor clinical manifestations of orbital phycomycosis appeared due to early deaths. If attempts are made to prolong the life span of such animals, or if fungus is inoculated before making rabbits diabetic and acidotic, orbital lesions and their further spread to adjacent tissues can possibly be better studied. Further studies should be carried out.
We gave steroids for 7 days and interestingly, we found that despite absence of an appreciable retro-ocular mass, proliferation of fungi in orbital tissue was evident. [Figure - 4] Cultures were also positive. This is in clear contrast with observations on healthy rabbits showiug negative cultures at the end of 2 months. Steroids have atleast permitted establishment& germination of Rhizopus spores. The results would be revealing if steroids are continued for several more days. There have been some clinical reports emphasising the potential of steroids. In ophthalmic practice, it is therefore urged that steroids should be administered only when candidly indicated. Also, proptosed eyeball under similar conditions should arouse a suspicion of orbital mycosis.
| Summary|| |
Orbital lesions were not produced with Aspergillus flavus alone or with Staphylococcus aureus introduced into the maxillary sinus of monkeys. Steroids did not affect the negative results. Systemic steroids however, helped establishing anfection with Rhizopus which remained sub-clinical. There developed a mass in diabetic rabbits showing proliferating fungus, areas of necrosis and a granulomatous reaction. Fungus was more invasive in animals in state of acidosis. In both iris groups, the infection remained clinically unmanifested.
| References|| |
Schwartz, J.N., Donnelly, E.H. and Klintworth. G.K., 1977, Surv. Ophthalmol: 22:3.
Mahajan, V.M., Dayal, Y. Patra, C.P. and Bhatia. I.M. 1978, Sahouraudia, 16:199.
Mahajan. V.M. Amar D. and Dayal, Y 1981 Mkyosen, 24:47.
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5]