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Title: An evaluation of the place of Nd:YAG laser iridotomy in the treatment of angle closure glaucoma
Author: Fleck, Brian William
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1992
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A series of clinical studies evaluating the role of Nd:YAG laser iridotomy in the management of angle closure glaucoma has been undertaken. Baseline data on the outcome of peripheral iridectomy or drainage surgery in 137 consecutive patients presenting with acute angle closure glaucoma during the period 1980 to 1985 was obtained. A prospective, randomised comparison of Ng:YAG laser iridotomy and peripheral iridectomy was performed in 52 fellow eyes, with a mean follow up period of 11.8 months. There was no significant change in endothelial cell count 6 months after treatment in either group. There were no significant differences in the visual acuity or glaucoma outcome of the two groups. One laser patient developed acute angle closure glaucoma. A non randomised prospective comparison of Nd:YAG laser iridotomy, peripheral iridectomy and trabeculectomy was performed in 54 eyes with acute angle closure glaucoma. The mean total Nd:YAG laser energy needed to create an iridotomy was greater in acute angle closure glaucoma eyes than in fellow eyes. Serial ultrasound pachymetry was used to measure the resolution of corneal oedema in 4 patients, in order to assess the optimal timing of Nd:YAG laser iridotomy. Two patients with a small patent Nd:YAG laser iridotomy developed acute angle closure glaucoma during the follow up period and this problem was investigated further. A mathematical model of the minimum area of iris opening needed to prevent angle closure glaucoma was developed. Photometric measurements of Nd:YAG laser iridotomy size before and after pupil dilation were made in 16 eyes. Pilocarpine/phenylephrine provocation tests were performed in 47 eyes with a laser iridotomy, and 36 eyes with a peripheral iridectomy. These investigations suggested that the minimum 'safe' iridotomy size is 150-200μ diameter. A prospective study of Nd:YAG laser iridotomy in 16 patients with chronic angle closure glaucoma showed improved glaucoma control in 7 patients. The technique of argon laser pretreatment followed by Nd:YAG laser iridotomy 4-6 weeks later was assessed in 10 patients. Argon laser pretreatment was performed in the right eye, and primary Nd:YAG laser iridotomy in the left eye. The mean total Nd:YAG laser energy needed to produce a patent iridotomy was significantly greater in pretreated eyes, and considerable pigment dispersion occurred at the time of Nd:YAG laser iridotomy in pretreated eyes. A comparison of argon laser iridotomy and Nd:YAG laser iridotomy was made in a group of 33 Chinese patients in Singapore and 25 Caucasian patients in Edinburgh. Qualitative differences in iris tissue responses to laser energy were noted.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (M.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available