Minimal chronic glaucoma risk after laser iridoplasty, demonstrated by tonography
Authors: Ruiz Pedro Grimaldos , Roko Victoria 
Published: June 2023

PURPOSE: To demonstrate that the risk of developing chronic pigmentary glaucoma following photoablative cosmetic iridoplasty (PCI) is minimal. To achieve this we employ the Grimaldos-Honan tonography.
DESIGN: Prospective and comparative clinical study on intraocular pressures, before and after PCI.
METHOD: A total of 560 patients were included in this study, consisting of healthy individuals over the age of 18. The patient population included cases of heterochromia, including congenital (7%), acquired (1%), trauma-related (0.5%), surgical (0.25%), nevus-related (0.25%), and cosmetic cases (91%). In our study, we employed the Tomey FT 1000 non-contact air tonometer to measure intraocular pressure (IOP) before and after the Grimaldos-Honan test. The procedure involves applying controlled pressure to the right eye using a Honan balloon for a duration of two minutes, while the left eye serves as a control. After removing the balloon, IOP is measured again within five minutes using the same tonometer in both eyes. This allows us to compare the pressure changes between the eye where the balloon was applied and the control eye.
RESULTS: When comparing the right eye pressure before and after the Grimaldos-Honan test, Wilcoxon test showed a statistically significant difference, with a p-value <2.2e-16 and a mean decrease of 1.749. In contrast, the tests comparing the pressure in the left eye before and after the Grimaldos-Honan test did not yield significant values. Both the Wilcoxon test and T-test showed p-values of 0.8589 and 0.5405, respectively, suggesting minimal differences and no significant effect on the pressure values in the eye without balloon application (mean decrease of -0.036). Furthermore, we compared the percentage decrease in right eye pressure (13.38) with the percentage decrease in left eye pressure (-1.01). Both the T-test and Wilcoxon test demonstrated statistically significant results, with p-values < 2.2e-16 and a mean difference of 14.39%. Investigating potential influences, we examined the impact of initial pigmentary degree and treatment phase number on the pressure differences between the right and left eyes. The Kruskal-Wallis test revealed no statistically significant differences in the percentage decrease in right eye pressure among patients with different pigmentary degrees (2 - 5) p-value of 0.2569 or treatment phases (1 - 5) p-value 0.3115, indicating that these factors did not affect the pressure reduction rate. For patients undergoing laser treatment, we analyzed the intraocular pressures of the right and left eyes before and after one full phase of laser treatment. No significant differences were found in the pressures of either eye before and after laser treatment, suggesting that the procedure did not significantly affect intraocular pressure (p-values > 0.5731).
CONCLUSION: Pigmentary glaucoma occurs when pigment from the iris is released and deposited onto the trabecular meshwork, leading to obstruction of the outflow pathway and increased resistance to aqueous humor drainage. This results in elevated intraocular pressure (IOP) levels, which can cause irreversible damage to the optic nerve. To prevent blockage of flow and maintain appropriate pressures, post-laser care is crucial. Patients are advised to maintain an upright posture after the procedure to allow residual pigment to settle in the inferior quadrant through gravity. This helps prevent further migration of pigment into the anterior chamber and promotes localized deposition. The recruitment of macrophages and phagocytes also plays a role in eliminating deposited pigment. Gonioscopy, particularly 360-degree imaging, provides insights into the distribution of pigment deposition, which aligns with the postural treatment approach. Additionally, a waiting period of 4 to 6 months is recommended before initiating subsequent laser interventions to allow for iris stromal homeostasis and healing processes. The Grimaldos-Honan tonography method is utilized to evaluate changes in IOP before and after laser treatment, providing valuable data for monitoring the effectiveness and safety of the procedure. This comprehensive approach, including clinical history assessment, regular IOP monitoring, tonography, and gonioscopy, contributes to personalized management of pigmentary glaucoma and improved treatment outcomes.