Abstract
Abstract: :
Purpose:1) To define the change in anterior chamber depth "ACD" and intraocular pressure "IOP" after phacoemulsification and posterior chamber lens "PCIOL" insertion. 2) To examine if these changes are related to preoperative ACD or IOP values. Methods:Patients were examined preoperatively at their routine preoperative visit and 8 weeks postoperatively by the same observer. The ACD was measured by the same Ultrasound–A–scanner and IOP was measured with the same Goldmann tonometer. Data were analysed using Microsoft EXCEL (2002) software and a P –value of < 0.05 was considered significant. Values were expressed as the mean. Results:78 patients were recruited. ACD increased by 1.14mm from 2.93mm preoperatively to 4.07mm postoperatively (P < 0.0001). There was a significant inverse relationship between preoperative–ACD and change in ACD (r = –0.74). There was a significant drop in IOP by 2.9mmHg from 15.4mmHg preoperatively 12.7mmHg postoperatively (P < 0.0001). There was a significant inverse relationship between initial IOP preoperatively and the amount of IOP drop postoperatively(r = –0.75). So we generated a new ratio. A ratio = preoperative–IOP/ preoperative–ACD. We called it the PD–ratio (i.e. Pressure to Depth ratio). Patients with a PD–Ratio < 5, had a mean drop in IOP of 1.65mmHg. However, patients with a PD–Ratio > 5, had a mean drop in IOP of 4.11 (P < 0.001). From the regression line equation (drawn through scatter values between the PD–ratio and IOP drop), we can predict the expected IOP–drop following surgery: IOP drop = 1.7716 – 0.8965*(PD–Ratio) Conclusions:Our data showed significant increase in ACD following phacoemulsification and PCIOL insertion, consistent with previous studies (e.g. Hayashi et al, 2000). We showed that a higher PD–Ratio was associated with a greater drop in IOP postoperatively. This new Ratio may be a novel index for selecting phacoemulsification and PCIOL insertion as a treatment option for patients with narrow angle glaucoma as they have a high PD–Ratio (i.e. shallow AC and high IOP). Furthermore, the PD–Ratio could, potentially, also be used as a guide in the management of primary open angle glaucoma (POAG). In other words, in selected POAG patients with a high PD–Ratio, phacoemulsification and PCIOL implantation may be preferable to traditional filtration surgery with all of its inherent risks (when only a moderate IOP drop is required). Finally, should we consider discontinuing anti–glaucoma treatment in glaucoma patients, who have a high PD–Ratio, after cataract surgery?
Keywords: anterior chamber • cataract • intraocular pressure