Dr Alex Ioannidis discusses the positive impact the iStent inject system has had on the management of mild to moderate stable glaucoma and its comorbidities, with evidence from several case studies.
Ocular surface disease (OSD) is a multifactorial disorder of the conjunctival epithelium, cornea, lacrimal, and meibomian glands that results in either deficient or inappropriate tear production. OSD can lead to decreased visual acuity and result in significant ocular discomfort.¹
OSD can occur in conjunction with many other ocular conditions and often co-exists with glaucoma due to the current use of medications used to treat the condition. At present, 11% of the five million Americans over 50 who have dry eye disease also have glaucoma.2
Topical medical therapy is the most common initial treatment for glaucoma, and 49-59% of glaucoma patients on topical anti-glaucomatous medications have some form of OSD.3
OSD in these patients can be a pre-existing condition that is exacerbated by topical therapy or a novel disease that manifests after initiation of topical glaucoma therapy.
Topical glaucoma medications can cause significant morbidity with patients complaining of a burning sensation, irritation, itching, tearing, skin pigmentation and decreases in visual acuity often within three months of medication initiation.4
Furthermore, untreated primary open angle glaucoma (POAG) patients have a higher risk of OSD in part due to a 22% lower basal tear turnover rate in comparison to patients without glaucoma.5
The resulting OSD in patients with glaucoma can lead to poor medication compliance from the associated symptoms. This can lead to cessation of therapy by the patient without informing the physician resulting in elevation of IOP and disease progression.
In addition, OSD is also linked to a higher rate of failure in filtration glaucoma surgery.
Thus, management of OSD in glaucomatous patients is important when trying to reduce further ocular morbidity and to improve the success of glaucoma therapy.
Case 1
A 69-year-old female patient with unilateral POAG presented complaining of chronic conjunctival injection and irritation. Her condition was stable based on serial VF testing and OCT analysis of the optic nerves.
Her IOP was measured at 18 mmHg on GAT. Her glaucoma was being treated with Latanoprost nocte in the left eye. On this last review, she was found to have developed a cataract and was keen to explore her options on reducing the drop burden on her ocular surface – and to become drop free if possible.
Clinical examination revealed significant skin pigmentation and conjunctival injection of the left eye (Fig 1/2).
Cataract surgery was performed in combination with implantation of the iStent inject system in the trabecular meshwork. Her postoperative IOP was 14 mmHg and the latanoprost drops were ceased in the left eye. Within a month there was a marked improvement in the appearance of her conjunctiva with resolution of the symptoms of irritation.
Her forniceal conjunctiva ceased to be injected (Fig 3).
Case 2
The chronic use of medications to lower IOP can have other unintended consequences when it comes to the management of the ocular surface.
The use of prostaglandin analogues has also been associated with local tissue atrophy in the orbit – a type of orbitopathy – reported to occur with a number of prostaglandin analogues in current circulation.6 This can result in deepening of the orbital sulcus due to the loss of adipose and connective tissue in that area (Fig. 4/5).
Case 3
Corneal toxicity secondary to chronic medication use is another area where the iStent inject system can make a significant difference eliminating the gritty and stinging sensation that is associated with drop installation.
The main culprit in these cases with benzalkonium chloride (BAK) which acts as a preservative in glaucoma medications.
BAK has been shown to strongly induce the expression of inflammatory mediators in the lens epithelial cells compared with latanoprost or timolol.
The Blue Mountains Eye Study and Ocular Hypertension Treatment Study both suggested higher rates of cataract formation in those with antiglaucoma therapy. Miyake conducted studies that suggested that BAK preserved drops prior to cataract surgery increased the risk of cystoid macular oedema.
Chronic BAK exposure has been associated with significant ocular surface toxicity, often manifesting as a diffuse punctate keratopathy (Fig 6).
Once iStent inject surgery has been performed – as in this case – and BAK is eliminated from the ocular surface, significant improvement of the overall corneal health is seen with resolution of the signs (Fig 7).
In conclusion, the use of microtrabecular shunts such as the iStent inject system has been revolutionary in the management of mild to moderate stable glaucoma.
We see that the chronic use of drops has a detrimental effect on the ocular surface of these patients resulting in secondary morbidity which can be quite significant but also can result in poor adherence to management protocols.
It is therefore advantageous to offer this cohort of patients access to the iStent inject system reducing or eliminating the drop burden and thus achieving better outcomes and disease management.
About the Author:
Name: Dr Alex Ioannidis
Qualifications: MBBS FRCOPHTH FRANZCO
Affiliations: Vision Eye Institute
Location: Melbourne
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References
1. Ramli N, Supramaniam G, Samsudin A, Juana A, Zahari M, Choo MM. Ocular surface disease in glaucoma: Effect of polypharmacy and preservatives. Optom Vis Sci. 2015; 92(9):e222–6.
2. Quigley HA, Broman AT. The number of people with glaucoma worldwide in 2010 and 2020. Br J Ophthalmol. 2006; 90(3):262–267.
3. Leung EW, Medeiros FA, Weinreb RN. Prevalence of ocular surface disease in glaucoma patients. J Glaucoma. 2008; 17(5):350–355.
4. Rossi GC, Scudeller L, Rolle T, Pasinetti GM, Bianchi PE. From benzalkonium chloride- preserved latanoprost to polyquad-preserved travoprost: A 6-month study on ocular surface safety and tolerability. Expert Opin Drug Saf. 2015; 14(5):619–623.
5. Kuppens EV, van Best JA, Sterk CC, de Keizer RJ. Decreased basal tear turnover in patients with untreated primary open-angle glaucoma. Am J Ophthalmol. 1995; 120(1):41– 46.
6. Inoue K, Shiokawa M, Wakakura M, Tomita G. Deepening of the upper eyelid sulcus
