Secondary glaucoma

Secondary glaucoma has different forms based on the varying underlying ocular conditions. These conditions result in an increase in IOP that manifests as secondary glaucoma. Paediatric congenital cataract associated glaucoma Based on the onset of secondary glaucoma in paediatric patients, it can be classified into early-stage and late-stage glaucoma cases. Early-stage secondary glaucoma, observed as angle-closure glaucoma, results from the blockage and inflammation of the peripheral anterior synechiae structure. In primary IOL, cataract surgery is performed alongside immediate implantation of IOL. However, in secondary IOL implantation, the patient is prescribed aphakic glasses or contact lenses till the implantation of IOL after a varied period of time between a few months or years. Primary IOL implantation is observed to significantly reduce and avoid the occurrence of secondary glaucoma in paediatric patients under the age of two. Schwartz hypothesized iridocyclitis as the cause of elevated intraocular pressure, but Davidorf suggested that the elevated IOP may be due to obstruction of trabecular meshwork by pigmented cells representing photoreceptor outer segments from retinal pigment epithelium that migrate anteriorly within the aqueous humor. Later, Matsuo et al. isolated photoreceptor outer segments and inflammatory cells in aqueous humor and hypothesized that photoreceptor outer segments pass through the retinal break cause aqueous outflow obstruction and elevated IOP. == Epidemiology ==

The overall prevalence of secondary glaucoma across China between 1990 and 2015 was reported to be 0.15%, lower than the overall estimates for East Asia (0.39%). Varying forms of secondary glaucoma Pigmentary glaucoma has lower incidence in Black and Asian populations, due to their characteristically thicker irises that result in a lower likelihood of pigment release, as compared to the White populations. The incidence of pigmentary glaucoma decreases with age while in exfoliation syndrome the incidence increases with age. However, given the derived nature of secondary glaucoma, there may be no significant association between age, ethnicity or gender and the prevalence of the condition. Secondary glaucoma indicated after congenital cataract surgery is found between 6 and 24% of the cases noted, whereas, secondary glaucoma caused by primary IOL implantation was observed as 9.5%. Additionally, for patients with aphakia and secondary IOL implantation, 15.1% of the cases were determined. The incidence risk in primary IOL implantation in children with cataract in both eyes is lower than secondary IOL implantation and aphakic condition. However, this difference is not observed in the general population and populations with cataract in one eye. Due to lack of concrete and specific epidemiological evidence, further research is required to accurately estimate the prevalence of secondary glaucoma and its subtypes. == Risk factors ==

In general, elevated IOP is a major risk factor in the development of secondary glaucoma. However, there are several risk factors contributing to the fluctuation in IOP levels. Uveitis Secondary glaucoma is commonly associated with uveitis. Uveitis is the inflammation of the uvea, a middle layer tissue of the eye consisting of the ciliary body, choroid and iris. Various causes have been identified as potential risk factors contributing to the occurrence of secondary glaucoma. These include viral anterior uveitis due to cytomegalovirus infection, and herpetic anterior uveitis caused by herpes simplex virus. The observed pathophysiology of secondary glaucoma in uveitis is found to be linked to the increase and fluctuation of IOP. Inflammation of eye tissues contributes to the blockage of IOP produced in the ciliary body. This results in the accumulation of aqueous and thus elevated IOP, which is a common risk factor for the progression of secondary glaucoma. Paediatric congenital cataract surgery Paediatric congenital cataract surgery is also identified as a risk factor for the progression of secondary glaucoma. Cataract is an ocular disease, identified by the progressive clouding of the lens. Surgical procedures are often employed to replace the lens and allow for clear vision. However, there is an increased risk of secondary glaucoma development in children due to the secondary IOL implantation procedure. The blockage of vitreous flow due to inflammation in the structures of the trabecular meshwork is also observed in herpetic anterior uveitis patients. In addition to this, angle invasion is a mechanism that is observed to contribute greatly to the development of secondary glaucoma in patients with iris tapioca melanoma, iris lymphoma, choroidal melanoma, and medulloepithelioma. == Treatment and management ==

Pharmacological interventions Miotic drugs are a class of cholinergic drugs that are frequently employed in the treatment and management of all types of glaucoma. These drugs stimulate the contraction of the pupil causing the iris to pull away from the trabecular meshwork. Despite the advantages, the widespread use of miotic drugs is limited by its associated side effects. There is an increased risk of development of posterior synechiae in glaucoma secondary to exfoliation syndrome and ocular trauma. Laser therapy Among different laser therapies, laser peripheral iridotomy and laser trabeculoplasty are the most common procedures for secondary glaucoma. Both methods involve creating new outlets for the aqueous humour to flow out of, effectively reducing the IOP. In peripheral laser iridotomy, the opening is created in the iris tissue while in trabeculoplasty, this opening is made in the trabecular meshwork. Further, there are two types of laser trabeculoplasty: argon laser trabeculoplasty and selective laser trabeculoplasty. Laser peripheral iridotomy has high efficacy in the treatment of pigmentary glaucoma. Argon laser trabeculoplasty is effective in the management of corticosteroid and pigmentary glaucoma. However, this is often contraindicated due to high rates of failure in patients with uveitic glaucoma. For uveitic glaucoma, treatment with selective laser trabeculoplasty is associated with fewer adverse effects and risks of failure. Surgical treatment Surgical procedures are effective in cases where pharmacological management is not successful or suitable. Such methods work by facilitating aqueous outflow through the modification of the obstructing trabecular meshwork using trabeculectomy, goniotomy, non-penetrating deep sclerectomy or canaloplasty. Alternatively, introduction of new drainage pathways may also be achieved by the implantation of glaucoma shunts or glaucoma drainage devices. Trabeculectomy is held as the gold standard for surgical management of glaucoma. Studies indicate that treatment of uveitic glaucoma using trabeculectomy with antimetabolites administration has a high success rate of 62%-81%. Thus, it is also commonly used in the treatment of pigmentary glaucoma. Drainage tube implants are also implicated in treatment of uveitic and inflammatory glaucoma. Minimally invasive glaucoma surgery is performed in order to overcome the risks and adverse effects associated with conventional surgical procedures. However, there are limited studies testing the efficacy of utilising this type of surgery for the treatment of uveitic glaucoma. In addition to the direct reduction of IOP, surgical procedures are used to remove blood, viscoelastic fluid and debris in glaucoma caused by cataract extraction and ocular trauma. They may also be utilized to remove depot steroids in corticosteroid glaucoma and ghost cells from the vitreous humour in ghost-cell glaucoma through a procedure known as vitrectomy. == References ==