Visual Fields
Visual Fields is a scholarly work, published in 2001 in ''British Journal of Ophthalmology''. The main subjects of the publication include optometry, medicine, and ophthalmology. Cataract lens extraction and posterior chamber lens implantation in Korean subjectsEDITOR,-We read with interest the article by Kee and Moon 1 who provided interesting data on the eVect of cataract removal on outflow facility and intraocular pressure (IOP).We have been interested for some time in the eVect of ocular surgery upon measured IOP. 2 Previous studies have shown a reduction in IOP after cataract surgery 3 4 and have suggested implications for combined cataract and filtering surgery.To assess change in outflow facility Kee and Moon utilised pneumotonometry.However, this technique has been shown to give low reproducibility 5 as a tonography method.Indeed, Shiotz tonography may have been more accurate. 5The investigators may have had technical reasons for their choice of instrument; however, no justification was provided, nor was diurnal variation in IOP accounted for in this study.The authors' extrapolated ciliary muscle response to pilocarpine from measurements of the outflow facility before and 1 hour after 2% pilocarpine instillation.To specifically investigate the eVect of the lens on ciliary muscle contractility the authors repeated the measurement 2 months after phacoemulsification surgery.Interestingly, these latter assessments may not have allowed suYcient time for IOP and outflow facility to stabilise and the hypertensive eVect of topical corticosteroids to wane.In general, published 1 year follow up studies demonstrate mixed results in relation to IOP reduction and altered outflow facility. 3 4 6 We have carried out a prospective observational study of phacoemusification (phaco) surgery performed at a major teaching hospital.In 393 consecutive small incision (3.2 mm) phaco procedures performed over a 5 month period authors also demonstrated a significant (Student's t test p<0.001) drop of measured IOP comparing preoperative and 4 weeks post-phaco IOP (1.28 (SD 3.10) mm Hg).Furthermore, analysis of the data revealed the drop in IOP was significant for both clear corneal incision (n=318) and scleral tunnel incision (n=75) phaco techniques, being 1.5 (3.16) mm Hg (p<0.001) and 0.9 (2.9) mm Hg (p=0.015),respectively.However, when those with a history of glaucoma (n=39) were analysed separately, a non-significant (p=0.28)reduction of IOP (0.69 (3.47) mm Hg) was demonstrated.We believe to adequately define the eVects of cataract surgery on IOP in a glaucomatous population, a larger group prospectively studied over a period longer than 2 months and preferably more than 1 year is required and a reproducible accurate assessment of outflow facility would be of added value.