(D) Antibiotic drops # INJURIES BY CAUSTICS such as lime usually occur from fresh mortar or whitewash entering the eye or from laboratory alkalis.> These may cause considerable damage to the eye because they penetrate and cause necrosis of the surface epithelium in a few seconds with occlusion of the limbal vasculature.> This leads to a diminished vascularity of the anterior segment, corneal opacification and melting, cataract and symblepharcn.> Ammonia and sodium hydroxide are particularly harmful, as they cause necrosis of the cornea.> Immediately after the accident there is intense conjunctivitis and chemosis, but the cornea often looks clear, and it is therefore difficult to ascertain the severity of the injury.> A drop of fluorescein solution will reveal the extent of the denuded area of epithelium.> Circumferential limbal ischaemia and the degree of corneal clarity provide some indication of the final visual status of the patient.> Limbal ischaemia leads to severe damage of the limbal stem cells. This causes persistent corneal epithelial defects and conjunctivization of the corneal epithelium.> Treatment In injury caused by caustics the excess of deleterious material must be removed at the earliest by a copious and immediate irrigation with normal saline. An intra venous infusion line is useful in directing a steady, con trolled flow of saline onto the ocular surface. All fornices should be washed and irrigation continued till the pH returns to normal or for a minimum of 30 minutes. There should be no delay in instituting therapy and, if saline is not immediately available, the eye should be copiously irrigated at once with water. Particles of lime must be perseveringly picked out with forceps after instillation of a local anaesthetic. An antibiotic ointment or drops and cycloplegics should be instilled. Corticosteroids are potent agents in reducing the inflammatory reaction and prevent the formation of excessive granulation tissue, which determines the development of symblepharon. They can be used topically as drops or ointment for the first 10 days, together with acetazolamide tablets to lower the intraocular pressure. Thereafter, steroids are stopped as they impair healing and may precipitate corneal melting.> Ascorbic acid and tetracyclines are given topically and systemically to enhance collagen formation.> To inhibit collagenolysis and stromal damage, 10% sodium citrate, 5% N-acetylcysteine or 1% medroxyprogesterone eye drops are useful adjuncts.> Symblepharon may be prevented by sweeping a glass rod well coated with a lubricant round the upper and lower fornices, so that they are well packed with ointment.> This procedure should be repeated several times a day, depending upon the severity of the case.> The fitting of a contact lens separates the two mucosal surfaces and prevents their adhesion.> Revascularization of the limbus and re-epithelialization of the ocular surface can be stimulated by a limbal cell transplant or amniotic membrane graft.