Effects of Diagnostic Mydriasis with Tropicamide and Phenylephrine on Intraocular Pressure

Abstract

Purpose: To determine the effects of diagnostic mydriasis using 1% tropicamide and 2.5% phenylephrine on the intraocular pressure of patients attending the Eye Clinic of University of Port Harcourt Teaching Hospital. Methods: This was an interventional 'within-patient' comparative hospital-based study conducted over 3 months, in which the right eyes of 137 subjects requiring diagnostic mydriasis received 1% tropicamide and 2.5% phenylephrine. The left eyes served as control. Results: There were 137 study participants: 86 males (62.8%) and 51 females (37.2%). The mean age of participants was 44.87±15.94 years. The baseline IOPs were 12.34±3mmHg for the Right Eye (RE) and 12.09±2.64mmHg for the Left Eye (LE). The mean post dilatation IOP at 30, 45, 60, 90 and 120 minutes in the RE were higher than baseline. The maximum mean post dilatation IOP in the RE was 13.75±2.99mmHg and this occurred at 45 minutes. In the control undilated LE, the mean post dilatation IOPs were lower than base-line at all the follow up periods except at 45 minutes where it was slightly higher (12.11±2.87mmHg). These differences in mean IOP change were statistically significant (p<0.05). At all the follow-up periods, 8.8%-14.6% of participant's right eyes had large IOP elevations (>5mmHg but <10mmHg). Multiple linear regression analysis showed that pre dilatation IOPs were positively correlated to post dilatation IOPs. Conclusion: There is need to recheck IOP post dilatation preferably at 45 minutes in all patients who have had diagnostic mydriasis to prevent damage to the optic nerve. Diagnostic mydriasis could safely be done using small concentrations of tropicamide and phenylephrine.

The effect of 1% tropicamide on central corneal thickness and intraocular pressure

“…However, 1% tropicamide might alter the IOP by obstructing the iridocorneal angle or decreasing traction on the trabecular meshwork, decreasing aqueous outflow drainage. 8,9,34 Also, the repeated application of eyedrops during the procedure may increase the CCT because of epithelial oedema, resulting in the possible over-measurement of IOP. 18 Measuring CCT and IOP takes about a minute to obtain readings and establish a treatment plan appropriate to delay the development of high IOP.…”

“…The relationship between central corneal thickness (CCT) and intraocular pressure (IOP) is integral in managing elevated IOP, 1,2,3,4,5 a pressure exerted by the aqueous humour. 6,7,8,9 The CCT can affect the IOP measurement, where a thick or thin cornea yields overestimation and underestimation of IOP, respectively. 10,11,12 This implication may hinder selecting a proper management regimen and lead to the mismanagement of patients with elevated IOP, which, when untreated, will cause damage to the optic nerve and lead to irreversible vision loss.…”

“…During such an examination, a diagnostic mydriatic agent (tropicamide) is routinely used for pupillary dilation to evaluate the fundus optimally. 8,15 In an ocular evaluation of an eye, 1% tropicamide may act as a mydriatic agent to dilate the eye in adults 9,14 The effect of these topical mydriatic eye drops typically subsides after 4 h of instillation, and this drug may affect CCT. 10,11,16,17 Furthermore, tropicamide may increase IOP by obstructing the iridocorneal angle, decreasing trabecular meshwork traction, and aqueous outflow drainage because of ciliary muscle paralysis.…”

“…10,11,16,17 Furthermore, tropicamide may increase IOP by obstructing the iridocorneal angle, decreasing trabecular meshwork traction, and aqueous outflow drainage because of ciliary muscle paralysis. 8,13,18 For every 0.32 mmHg increase in IOP, there is a possibility that CCT could increase by 10 µm. 19 The broad distribution of CCT ranges from 519 µm to 550 µm in Ethiopians and South Africans, respectively.…”

“…27,28,29 Diagnostic mydriatic agents are routinely used in most eye clinics; however, they can potentially increase IOP. 8,14,30 Furthermore, there is a paucity of similar studies in South Africa, including where there is measurement of CCT. Therefore, this study sought to understand the effect of 1% tropicamide as a mydriatic ocular solution in a clinical South African context on the CCT and IOP post mydriasis in three different intervals, namely 20 min, 30 min, and 45 min.…”