6 5 measured 3 days after the reinitiation of treatment with zidovudine, but otherwise ophthalmic findings were normal, especially the values for deutan and protan vision. Two weeks later tritan colour contrast sensitivity was RE 3 5, and LE 3 8 and other findings were unchanged. Comment Alterations of colour vision have been reported for numerous drugs.' 12 Acquired alterations of tritan vision are usually related to retinal damage.'3 Therefore, the dyschromatopsia in the two reported cases is expected to be related to retinal damage. Recently, retinal damage has been reported for children treated with 2',3'dideoxyinosine.'4 The authors used electrophysiological methods to measure retinal function, but no tests for colour vision were performed. They suggest that 2',3'-dideoxyinosine, which is also a dideoxynucleoside like zidovudine, causes a diffuse dysfunction of the retinal pigment epithelium. The pathogenesis of colour vision deficits in patients with symptomatic HIV infection or AIDS remains unclear. It was proposed that the HIV-related retinal microangiopathic syndrome plays an important role in the pathogenesis of those colour vision deficits. Our observations suggest that a temporary shift in tritan colour vision is an adverse effect at the beginning of treatment with zidovudine. This shift in tritan vision might be due to a temporary interference of zidovudine with the production of visual pigment, or a temporary alteration of the pigment epithelium. Nevertheless, other factors may underly the changes. It cannot be ruled out that long term application of zidovudine might contribute to the development of colour vision deficits described for patients with HIV disease. Health care professionals involved in the treatment of patients with HIV disease should be aware of any abnormal drug or disease related effects. This study was supported by Bundesministerium fur Forschung und Technologie, and by Bundesministerium fur Gesundheit, Germany, grant FKZ BGA III-002-89/FVP. We wish to thank Mrs Ch Hormann and Mrs cand med H Schmidt-Kittler for their help.

A preliminary study into the use of Vicryl in cataract and squint surgery has already been published (Munton, Phillips, Martin, Bartholomew, and Capperauld, I974). The safety and efficacy of the material were confirmned and it was concluded that the overall handling characteristics of monofilament Vicryl 8-o (dyed purple) were superior to monofilament nylon and equal to virgin silk. The sutures were absorbed with minimal inflammatory reaction on average by the 58th postoperative day. The only abnormalities which were possibly attributable to the new suture were three drainage blebs in cataract sections, two of which disappeared spontaneously.The purpose of this prospective, controlled randomized trial on the use of Vicryl in cataract surgery was to investigate further the possibility of a lack of wound security as a cause of draining blebs-an undesirable and occasionally dangerous complication-and to compare other early and late complications. Material and methodsVicryl (Ethicon) was supplied in lengths of 45-73 cm and diameter of 8-o monofilament and was coloured violet, with one 6 mm curved spatulate needle at each end.Patients with cataracts were taken without preselection from the waiting lists of the surgeons concerned and randomly (by coin tossing) allotted to the Vicryl or control groups. Unfortunately, numbers were limited by availability of suture material.Surgeon A used an ab-externo incision and cryoextraction and 4-5 interrupted I0-0 monofilament nylon or Vicryl sutures (I8 eyes). Surgeon B used an abexterno incision, chymotrypsin and forceps extraction, and 5-7 interrupted virgin silk or Vicryl sutures (22 eyes). Surgeon C used a Graefe section with one interrupted and one continuous suture, either Vicryl or monofilament nylon (five eyes).There had been some difficulty in knot tying during the preliminary study. The initial double throw of Vicryl holds the suture at the required tension, the second (single) throw rucks up the first (double) throw, thereby tightening the knot further. Practice is required Address for reprints: R. S. Bartholomew, Department of Ophthal. mology, the Eye Pavilion, Chalmers Street, Edinburgh EH3 9HA to judge the correct tension needed on the first (double) throw if the final knot is not to be too tight. The third and final (single) throw then locks the knot. Table I and the complications in Table II. Results Details of the patients are shown inEarly complications, defined as shallow anterior chambers, draining blebs, choroidal detachment, and hyphaema, occurring during the first postoperative week-possibly attributable to the difficulty in knot tying and therefore to wound closure were found in four out of 26 (15-4 per cent) of the Vicryl group while there were no complications in the control group of I9 patients. The difference, however, was not significant (X2 = 1-5; o03 > P > 0o2; n = i).Late complications, defined as draining blebs present and persisting two weeks after operationpossibly attributable to the new sutures-were found in five out of 26 (I9z2 per cent) of ...

Hospitals,4; and The Director of Surgical Research, Ethicon Limited,% Sighthill, EdinburghThe main function of a suture is to hold the wound edges in apposition until healing is sufficiently advanced for the wound to be self-supporting. In practice, as an absorbable material is losing tensile strength, the wound is gaining strength and at a particular time, which varies according to the tissue involved, equilibrium will be reached. Ophthalmic surgery presents the ideal situation where sutures implanted during operative procedures can be readily observed with regard to their tissue reactivity, biological acceptability, and loss of tensile strength. Characteristics ofknotting, tissue drag, and knot strength can also be assessed. A clinical trial of VICRYL® Synthetic Absorbable Sutures made by Ethicon was set up in three clinical centres: 27 cataract extractions and thirty squint operations were done to determine the safety and efficacy of this material.VICRYL®, or Polyglactin 9IO, is a synthetic absorbable suture which has been synthesized by the co-polymerization of a mixture of purified lactide and glycolide which are cyclic intermediates derived from lactic and glycolic acids. Glycolide and lactide are converted into a polymer in the form of uniform chips which are dyed violet. These chips are melted, and the polymer extruded to form fine filaments. These filaments are strengthened by stretching to allow molecular alignment. The resulting filaments are braided and the braid undergoes a further stretching process to increase further the tensile strength of the resulting suture. Being violet in colour, the suture is easily seen in the wound. The suture material is attached to an eyeless needle, placed dry into a foil package and sterilized by ethylene oxide. The braided VICRYL® is smaller in diameter than the corresponding size of catgut, although its "knot pull strength" is higher (Table I). Knot pull strength is recorded in pounds and is the tension at which a knotted piece of suture material breaks. This strength is always lower than the straight pull value with no knot in the material. In a comparison of VICRYLO, polyglycolic acid, and MERSILENE® it can be shown that VICRYL0 has a higher knot pull strength than any of the other materials mentioned (Table II).Extensive animal work had been performed by Ethicon with VICRYL® to show its safety and efficacy in vivo before release for clinical trial. This work included toxicity and carcinogenic studies, in-use animal work, and metabolic studies using radioactive labelled suture

Eighty patients were randomised in a single-masked parallel-group study to receive topically either the test drug, a diclofenac and gentamicin combination, or a betamethasone and neomycin combination after routine cataract extraction and intraocular lens implantation. Each group was assessed over a 6 week period for post-operative inflammation. The two drug combinations were equally effective in suppressing inflammation in the early post-operative stages and the diclofenac-gentamicin combination was slightly more effective in the later stages. The test drug was well tolerated and showed no adverse effects. We feel it is an effective and relatively safe drug which has a role as an anti-inflammatory agent after cataract extraction and has potential advantages in certain circumstances.

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