|Year : 2019 | Volume
| Issue : 2 | Page : 132-138
Coexistent cataract and glaucoma – Causes and management
Seshadri J Saikumar, Manju Anup, Abhilash Nair, Namitha R Mathew
Department of Cataract and Glaucoma, Giridhar Eye Institute, Kochi, Kerala, India
|Date of Web Publication||10-Sep-2019|
Dr. Seshadri J Saikumar
Department of Cataract and Glaucoma, Giridhar Eye Institute, Kadavanthra, Kochi, Kerala
Source of Support: None, Conflict of Interest: None
The optimal management of a glaucoma patient with cataract has always been a vexing issue. The prime concern has been to adequately control glaucoma while providing visual improvement and decreasing complications due to surgery. Advances in microsurgery techniques have improved surgical outcomes in recent years. However, numerous options exist and the management of an individual patient need to be personalized based on patient needs and surgical proficiency. This article aims to enlighten the reader regarding apt options in dealing with such individuals.
Keywords: Cataract, combined surgery, glaucoma
|How to cite this article:|
Saikumar SJ, Anup M, Nair A, Mathew NR. Coexistent cataract and glaucoma – Causes and management. TNOA J Ophthalmic Sci Res 2019;57:132-8
|How to cite this URL:|
Saikumar SJ, Anup M, Nair A, Mathew NR. Coexistent cataract and glaucoma – Causes and management. TNOA J Ophthalmic Sci Res [serial online] 2019 [cited 2020 May 27];57:132-8. Available from: http://www.tnoajosr.com/text.asp?2019/57/2/132/266403
| Introduction|| |
Cataract is the leading cause of blindness in India, accounting for more than half of all blindness. It is estimated that 7.63 million Indians will become blind from cataract by the year 2020, despite cataract surgery being the second-most common surgical procedure conducted. Prevalence of cataract varies from region to region and country to country. Studies from rural India have estimated the prevalence of unoperated cataract at 58% in North India and 53% in South India, among population >60 years of age. The prevalence of unoperated cataract was found to increase with age and to be higher in women. Among population above the age of 40 years, the prevalence was noted to be 47.5% with an age-adjusted prevalence of 61.9%.
As far as glaucoma is concerned, it is the second-most common cause of blindness. Estimates in 2010 indicate 11.2 million Indians aged over 40 years to be affected by glaucoma. Primary open-angle glaucoma affects 6.48 million and primary angle closure glaucoma 2.54 million. Primary angle closure disease spectrum could affect 27.6 million. Prevalence of the disease varies from study to study, but the WHO recognizes a prevalence of 2.6%, with around 1.2 million blind. Around 90% remains undiagnosed and prevalence also increases with age.,,,
The management of cataract or glaucoma independently is rather straight forward. Cataract surgery is performed widely, with surgeons having personal criteria. Preferred practice patterns are followed for glaucoma surgery also. The variety of glaucoma surgery available has increased manifold, and many advocate newer minimally invasive surgical procedures in the place of traditional trabeculectomy.
However, the optimal management of a glaucoma patient with cataract is challenging. This is mainly due to numerous newer surgical techniques being pioneered for both cataract and glaucoma. Laying down specific guidelines are difficult as management would depend not only on surgeon expertise and experience but also on factors related to patients.
In this article, we shall discuss the factors that should be considered in managing a glaucoma patient who also has cataract.
| Demographic Status of the Patient|| |
According to the 2011 census, 68.84% of Indians live in villages. In numerical terms, this amounts to 833 million citizens. There exists a glaring gap between the populations in terms of access to health-care facilities. The educational status of individuals and awareness levels about a disease like glaucoma are also abysmal in rural India. While the awareness level in the urban population was estimated to be 13.5%, it was only about 0.32% among rural counterparts. Often glaucoma is detected during the course of cataract screening camps. In such situations, treatment with topical medications may not be the optimal choice, due to the lack of follow-up facilities as well as difficulty in procuring refills. Adherence and persistence to eye drops can be expected to be low in such conditions. Therefore, it is prudent to opt for a combined cataract with glaucoma procedure for the patient, even if the stage of glaucoma may not warrant a surgical procedure.
| Where Glaucoma Is Caused by the Lens|| |
Lens-induced glaucomas are a group of disorders where the crystalline lens itself causes intraocular pressure rise. Conventionally, four different entities are included in this group of secondary glaucomas. The management of all forms is immediate control of inflammation and intraocular pressure, using topical and systemic medications, followed by lens extraction.
This condition occurs when high-molecular-weight lens proteins escape through fine defects in the lens capsule into the aqueous. It is typically seen in hypermature or Morgagnian cataracts. The presentation is with severe pain, redness, and decreased vision, somewhat akin to acute angle closure glaucoma. The patient is likely to have had poor vision for quite some time before the acute presentation. Intraocular pressure is very high, cornea edematous and anterior chamber are deep. Refractile lens proteins may be seen floating in the anterior chamber.
Lens particle glaucoma
This entity is also a form of secondary open-angle glaucoma where intraocular pressure elevation is caused due to obstruction of aqueous outflow by lens particles. It occurs in a setting of trauma, either surgical or accidental.
This is a very rare type of glaucoma and difficult to diagnose in vivo. The postulated mechanism is an immune-mediated reaction against lens proteins following surgery or trauma. Signs are similar to above but intensity of uveitis is severe. There is usually a latent period of 1–2 weeks before inflammation sets in and patient presents with symptoms. Presence of vitreous flare, synechiae, and mutton-fat keratic precipitates helps us to differentiate this entity from phacolytic glaucoma.
The cataractous lens increases in thickness as age increases. Consequently, pupillary block due to iridolenticular apposition causes increased intraocular pressure and symptoms suggestive of an acute attack of primary angle closure glaucoma. Signs also mirror those of acute primary angle closure glaucoma apart from uniformly shallow anterior chamber and a large intumescent lens.
Other forms of lens-induced glaucoma include those associated with nanophthalmos and microspherophakia.
Nanophthalmos is a condition characterized by a small eye without any other malformations. Glaucoma in nanophthalmos is primarily of angle closure variety and is managed initially by YAG peripheral iridotomy or iridoplasty. In the presence of peripheral anterior synechiae and raised intraocular pressure trabeculectomy is the preferred choice of treatment. Usually, glaucoma precedes cataract formation and combined surgery is not required. A recent review article has advocated cataract surgery as a viable option in the management of angle closure in nanophthalmos. Cataract surgery in these patients is fraught with risks and requires an experienced hand to manage intra-operative and post-operative complications.
Microspherophakia refers to a small crystalline lens. It is usually bilateral and is associated with movements of lens with changes in posture. Glaucoma occurs due to acute pupillary block due to forward movement of the lens. Peripheral anterior synechiae can develop if the pupillary block is unrelieved. Management is with YAG iridotomy followed by clear lens extraction. Filtering surgery is done if the above do not succeed.
| Angle Closure Disease and the Lens|| |
The role of crystalline lens in pathogenesis of angle closure disease has always been controversial. Lowe, in as early as 1972, showed that eyes with angle closure have significantly thicker lenses, which were anteriorly positioned and had steeper curvatures. Evidence, in the form of ultrasound biomicroscopy measurements, shows that removal of the lens increases the anterior chamber depth by nearly double. The EAGLE study compared efficacy of clear lens extraction to laser peripheral iridotomy and argued that clear lens extraction was more efficacious and cost effective as first line of treatment in angle closure disease. However, in the Indian scenario, where there is already a huge backlog of blinding cataract, advocating a surgical procedure instead of an outpatient procedure like iridotomy needs due consideration. We shall discuss various scenarios within the spectrum of angle closure disease and try to work out how an individual patient may be treated.
Medically uncontrolled angle closure glaucoma
In this group of patients, there are three options that can be considered. Phacoemulsification alone, trabeculectomy alone, or a combined procedure. Salmon demonstrated that long-term pressure control can be attained in such patients with trabeculectomy alone. Moreover, most eyes did not require additional medications for pressure control. However, one-third of the eyes required a further procedure, either cataract surgery or a repeat trabeculectomy. Sihota et al. also established that cataract formation is a complication of trabeculectomy, more so in angle closure patients than open angle glaucoma. Combined cataract surgery with trabeculectomy shows promise in the management of angle closure glaucoma as trabeculectomy alone hastens cataract formation and many patients will require cataract extraction in future. Phacoemulsification alone has also been shown to decrease pressures in this group of patients. However, reduction in intra ocular pressure as well as the number of antiglaucoma medications is less compared to combined procedure. Complications of surgery are lesser with cataract extraction alone, but the success of pressure control will depend on status of angle structures, for example, the presence of peripheral anterior synechia. Taking the above evidence into consideration, it is better to opt for combined phacoemulsification with trabeculectomy in patients with angle closure glaucoma uncontrolled with medications and peripheral iridotomy. The pressure reduction as well as reduction in number of drops is superior with the combined group.
Medically controlled angle closure glaucoma
Angle closure glaucoma patients who are controlled on medicines will, in due course of time, develop cataract. In this group, trabeculectomy alone serves no logical purpose, cataract removal is essential. The question is whether to do trabeculectomy in addition. Comparison studies show better pressure control with combined procedure. However, postoperative complications and as a consequence, additional surgical procedures were manifold higher among patients who underwent combined procedure. Hence, cataract extraction alone should suffice, with additional benefit of improved pressure control.
Acute primary angle closure glaucoma
Initial management of acute angle closure glaucoma is definitely medical. However, the role of early lens extraction instead of laser peripheral iridotomy has been studied. Pressure reduction at 18 months has been shown to be better with phacoemulsification rather than with laser iridotomy. Numbers of glaucoma medications used were also lower. However, the timing of early surgery remains controversial, waiting for 4 weeks is recommended. Early surgery is challenging due to inflammation, corneal edema, atrophic iris, poor pupillary dilatation, and also shallow anterior chamber. Phacoemulsification will require premedication with mannitol, guarded entry, tight wounds, and the use of appropriate viscoelastics. Taking into consideration, the risks involved in surgery, it is probably prudent to follow a conservative approach in dealing with acute angle closure attacks.
| Cataract in Open Angle Glaucoma|| |
While cataract surgery in angle closure disease definitely improves aqueous drainage facility, the same is not true in patients who already have open angles. Although both cataract and glaucoma are common conditions in the aged, there is a lack of consensus in management when they coexist. While modern cataract surgery is a safe and highly predictable procedure, filtering surgeries are still associated with both intra-operative and post-operative complications. Improvement of vision is taken for granted following cataract surgery, while it is anything but perfect following glaucoma procedures. Due to the above reasons, glaucoma surgeons usually consider cases on an individual basis and treat as they feel appropriate. However, a few factors can be taken into consideration.
Intraocular pressure and cataract surgery
One of the positive effects of cataract surgery in healthy eyes is the reduction in intraocular pressure. However, this may not be evident in eyes with glaucoma which are already on medications. Few studies have been done on glaucoma patients undergoing cataract surgery and have shown decrease in number of medications needed postsurgery.,, However, all the studies are retrospective in nature and unmasked. Most studies used a single pressure recording as baseline. Mansberger et al performed a subgroup analysis, of ocular hypertensives who were not on medications, from patients enrolled in the Ocular Hypertension Treatment Study. He found that a pressure reduction of about 4 mm was achieved by cataract surgery alone and this persisted for at least 3 years. One of the predictors of higher pressure reduction was higher preoperative intraocular pressure.
However, extrapolating these findings to glaucoma patients undergoing cataract surgery is not proper. Anecdotal evidence shows pressure reduction by around 20% for about a year, after which medications were required to maintain target intraocular pressure. It has also been found that pressure drop is less likely on patients with multiple drugs compared with those on monotherapy.
Patients on relatively mild glaucoma or ocular hypertensives on treatment may be offered a drug holiday after cataract extraction. Regular pressure monitoring is required and if target pressure level is breached, glaucoma medicines are restarted. Drug holiday on patients having more advanced glaucoma and on those who are using multiple medications is riskier and requires more frequent monitoring.
Cataract surgery alone may suffice in pseudoexfoliation
Shingleton et al., in a single surgeon case series, demonstrated that intraocular pressure reduction was possible in both pseudoexfoliation patients as well as pseudoexfoliation glaucoma patients. Only 3.7% of glaucoma patients required further laser or glaucoma surgery. He also concluded that the pressure reduction was proportional to preoperative pressure and that glaucoma progression was low over a period of 7 years.
Trabeculectomy following cataract surgery
Previous conjunctival incisional surgery decreases the efficacy of future trabeculectomy procedure due to increased scarring and chance of failure of trabeculectomy bleb. However, in the era of clear corneal phacoemulsification, conjunctiva is untouched and surgical success rates are good., The need for peripheral iridotomy in pseudophakic eyes is also debatable and may not be required due to increased depth of the anterior chamber.
Cataract surgery in eyes with trabeculectomy bleb
Eyes with preexisting blebs that undergo cataract surgery show decreased pressure control and failure of filtration.,,, This is more so in eyes with conjunctival incision cataract surgery and less pronounced in eyes with clear corneal phacoemulsification. An average increase in intraocular pressure of 2 mmHg can be expected. This may necessitate increased use of anti-glaucoma medications or additional glaucoma procedures. Few other factors also need consideration. The shorter the time interval between trabeculectomy and cataract surgery greater the chance of failure. A delay of 1–2 years has been suggested. Lower preoperative intraocular pressures, temporal clear corneal phacoemulsification, lesser intraoperative complications, and the use of nonsteroidal anti-inflammatory drugs following cataract surgery have all been associated with better postoperative bleb function.
One of the main side effects of trabeculectomy is cataract genesis. Almost half of all patients who undergo trabeculectomy require cataract surgery within 5 years. Furthermore, cataract surgery definitely decreases the functional status of the bleb. In such a situation, it is probably better to do a combined procedure, even if the patient has only early cataract. Another situation to consider is a glaucoma patient with visually significant cataract. Because combined surgery is associated with more complications, unless the glaucoma is progressing or requires ≥2 medications, cataract surgery alone should suffice. The situation can be discussed with the informed patient and decision modified accordingly.
Single site approach
The preferred site for trabeculectomy procedure is superior. The advantage is that the incision, bleb, and sutures stay under cover of the superior lid and is hence not exposed to the outside environment. Fornix-based conjunctival flaps are the preferred choice due to diffuse, posterior bleb formation as well as avoiding late encircling fibrosis. Cataract surgeons prefer temporal approach for phacoemulsification. However, many surgeons, while combining phacoemulsification with trabeculectomy, use a single incision for both procedures [Figure 1].
The surgery is done under peribulbar anesthesia. A superior rectus bridle suture is used to rotate the globe downward, ensuring adequate exposure of superior bulbar conjunctiva. The conjunctiva is incised from the limbus and reflected backward. Light cautery is done to avoid postoperative hemorrhagic bleb. Some surgeons dissect the Tenon's capsule separately and excise excess capsular tissue if it is too thick. A partial thickness scleral flap is created and lamellar dissection is done to extend the flap toward the limbus. The size and shape of the flap and its thickness are surgeon preferences. The reflected conjunctiva is also undermined all around the flap so as to allow aqueous to percolate into the subconjunctival space easily. Mitomycin C can be applied at this step [Figure 2]. Usually, Weck-cell sponge bits are soaked in 0.2–0.4 mg/ml solution and applied subconjunctivaly. Care is taken to avoid contact of sponges with the edges of the conjunctival flap. Usually, the sponge bits are kept for a period of 2–4 min. The area of contact is then copiously washed with saline solution to remove any traces of mitomycin. It should be ensured that no mitomycin enters into the anterior chamber. Usually, a guarded side port entry is made first. Viscosurgical device is injected into the anterior chamber to prevent sudden shallowing of the anterior chamber when making the trabeculectomy incision. In the single site procedure, the surgeon does not change the surgical approach, instead uses the trabeculectomy incision for introducing the phacoemulsification probe. Cataract surgery is completed and intraocular lens inserted. Conventionally, pilocarpine is next instilled to constrict the pupil and to facilitate peripheral iridectomy. Trabeculectomy is then done either using a Kelly's Trabeculo-Descemet'spunch or a block of trabecular tissue is dissected and excised. Adequate outflow through the ostium is ensured and the scleral flap and conjunctiva are sutured in layers. Bleb formation and the absence of leak are ensured and eye padded after subconjunctival antibiotic and dexamethasone injection.
Two site approach
The essential steps of surgery are similar. The difference is that after scleral dissection and mitomycin wash out, the surgeon shifts to a temporal position for phacoemulsification [Figure 3]. The advantage is that this location is more familiar for cataract surgeons compared to a superior approach. A temporal approach is also more convenient in patients with deep orbits or thick eyebrows. After lens implantation, the main wound is sutured so as to ensure water tight closure. Side ports need not be sutured, but their location should not overlie the trabeculectomy site.
Pressure control between patients who underwent trabeculectomy alone versus those who underwent combined procedure showed similar long-term results. Another study also showed similar pressure reduction, but the two-site group required lesser postoperative medicines and had lesser astigmatism. Operating time was found to be more in the two-site group as compared to the single-site group. Visual improvement and complication rates were similar between the two groups in all the studies. The need for peripheral iridectomy in phacotrabeculectomy is debatable and studies have found similar pressure decrease. Inflammation, by clinical grading, was found to be higher in the iridectomy group. Another aspect investigated was the extent of endothelial cell loss. Studies have proved that endothelial cell loss was more in eyes undergoing two-site procedures., Hence, it may be sensible to do single-site procedure in eyes with compromised corneas.
Mechanism of pressure reduction
The mechanism of pressure reduction postcataract surgery in angle closure disease is opening up of the mechanically blocked anterior chamber angle. However, in open-angle glaucoma patients undergoing cataract surgery, the pressure lowering mechanism is more ambiguous. Numerous mechanisms have been suggested, including reduction in deposition of glycosaminoglycans in the trabecular meshwork. It has also been proposed that the inflammatory mediators released during cataract surgery cause modulation of the extracellular matrix of the trabecular meshwork. Somewhat similar to the effect of laser trabeculoplasty. Alterations in blood aqueous barrier and remodeling of trabecular endothelium in response to ultrasonic vibrations are other possible means., Studies using anterior segment-optical coherence tomography (OCT), optical biometry, and ultrasound biomicroscopy demonstrate changes in anterior chamber architecture, which are also probable causes of reduced intraocular pressure in open-angle glaucoma patients.
Apart from pressure reduction, another advantage of cataract surgery is the enhanced ability for the treating clinician in follow-up of glaucoma patients. Improvement in visual acuity enhances reliability of field tests and improves mean deviation. Optic disc biomicroscopy and measurements on OCT are also enhanced.
Moreover, stereo photos are found to be more accurate post cataract surgery.
| Newer Directions in Glaucoma Surgery|| |
Conventionally, glaucoma surgery is synonymous with trabeculectomy. Although the procedure is ≥50-year-old, it is still considered the gold standard. It is also the most extensively studied procedure and widely done in India for uncontrolled glaucoma and by far, the most affordable. However, this might change soon with the advent of a new group of surgeries termed microinvasive glaucoma surgeries. The common feature of these procedures is that they are all intraoperative procedures that spare the conjunctiva. There is less inflammation, less complications, and less refractive change. They have lesser impact on the patient's quality of life. However, apart from endocyclophotocoagulation, all the others require open angles; which makes it unsuitable for much of the Indian population. Their efficacies are considered lesser than trabeculectomy and are advocated for mild and moderate glaucoma. Long-term studies in Indian population are also not available. Combination of these surgeries with phacoemulsification is an exciting prospect and could provide safer options in future.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]