Secondary open-angle glaucoma following YAG-laser vitreolysis

Abstract

We report a case of a man in his 50s who developed open-angle glaucoma following neodymium-doped yttrium aluminium garnet (YAG) laser vitreolysis. Despite attempts to control the pressure with topical medication and selective laser trabeculoplasty (SLT), surgical intervention using a Baerveldt glaucoma valve (BGV) was needed after which the intraocular pressure was controlled successfully. This rare but serious complication highlights the fact that in certain cases long-term monitoring of intraocular pressure is necessary following laser vitreolysis.

Background

Yttrium aluminium garnet (YAG) vitreolysis is one of two possible treatment modalities for vitreous floaters, the other being definitive removal of the vitreous via pars plana vitrectomy (PPV).¹ Laser vitreolysis seems to be generally well tolerated² yet there have been reports of complications such as cataract formation, posterior capsule rupture, retinal detachment and elevated intraocular pressure.³ We would like to present an unusual complication of difficult to treat open angle glaucoma following laser vitreolysis as well as the management thereof.

Case presentation

A man in his 50s was referred to our hospital from an ophthalmology clinic specialising in laser vitreolysis. Initially, the patient suffered from a prominent floater, morphologically resembling a bottlebrush, which gave debilitating entoptic symptoms (video 1). There was no posterior vitreous detachment present and the eye was treated with two sessions of YAG laser vitreolysis. During the first treatment, the patient received 753 pulses of 1.6 mJ of energy, administered in bursts of 3–5 pulses. The second treatment followed 10 days later, where he received 515 pulses of 1.9 mJ of energy per pulse, again in bursts of 3–5 pulses.

Video 1.

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bcr-2022-248937supp001.mp4 ^{(668.9KB, mp4)}

DOI: 10.1136/bcr-2022-248937.video01

Prior to treatment the non-contact ocular pressures were 13 and 15 mm Hg for the right and left eye, respectively. Before the second treatment the non-contact ocular pressure of the right eye increased to 19 mm Hg, while the left eye remained stable. Goldmann applanation tonometry of the right eye was 21 mm Hg. The floaters responded well to the treatment, and the patient reported a subjective improvement in symptoms.

One week after the second laser treatment the ocular pressures for the right (OD) and left (OS) eyes were 22 and 10 mm Hg, respectively. Four weeks later the pressure had increased to 38/15 mm Hg and the patient was started on topical timolol/dorzolamide two times per day, and a short course of oral acetazolamide to promptly normalise the ocular pressure. Over the following 17 months, ocular pressures below 21 mm Hg were achieved with two sessions of selective laser trabeculoplasty as well as topical dorzolamide/timolol and latanoprost. Attempts to taper topical therapy by stopping either latanoprost or dorzolamide/timolol were unsuccessful.

Unfortunately, there was a 4 month delay in follow-up following COVID-19 crisis, and the patient presented hereafter with an ocular pressure of 36 mm Hg, new thinning of the neuroretinal rim, and a superior nasal step on visual field examination. Topical therapy consisting of bimatoprost, brimonidine, dorzolamide/timolol and oral acetazolamide was able to reduce the ocular pressure to 22 mm Hg, and the patient was referred to our academic hospital for further treatment.

The patient had a negative history of risk factors for primary open-angle glaucoma such as diabetes, hypertension and hypotension, ocular traumas, steroid use and obstructive sleep apnoea. Family history for blindness, glaucoma or other ocular disorders was negative. At presentation to our hospital the patient had asymmetrical optic nerves with unilateral glaucomatous cupping of the disc and a cup/disc ratio of 0.4 in the right eye and 0.1 in the left eye. Snellen visual acuity was 20/20 in the right eye and 20/16 in the left eye. There were no signs of pseudoexfoliation or pigment dispersion. Gonioscopy showed bilateral open anterior chamber angles (40°), flat iris curvature, iris insertion at the ciliary body band, normal pigmentation and no presence of peripheral anterior synechiae.

Corneal pachymetry was 510 µm for the right eye and 520 µm for the left eye. Visual field examination OD showed a superior arcuate scotoma and inferior nasal step (figure 1) while OS was unremarkable. Optical coherence tomography (OCT) showed damage to the ganglion cell layer (GCL), superotemporal and inferotemporal thinning of the retinal nerve fibre layer (RNFL) (figure 2). The left eye showed no signs of glaucomatous damage.

Figure 1.

Humphrey 24–2 SITA-fast greyscale visual field of OD (right) and OS (left). A dense superior arcuate scotoma as well as decreased sensitivity in the inferonasal quadrant is seen in the right eye, while the left eye is normal.

Figure 2.

Fundus photography of OD (above) and OS (below), with corresponding OCT of the GCL and RNFL. OD shows neuroretinal rim thinning characteristics in glaucoma, as well as thinning of the GCL and RNFL when compared with OS. GCL, ganglion cell layer; OCT, optical coherence tomography; RNFL, retinal nerve fibre layer.

Differential diagnosis

Our initial differential diagnosis included primary glaucoma and other causes of secondary glaucoma besides vitreolysis-induced glaucoma. The patient history, however, was negative for alternative risk factors and there were no signs to suggest glaucoma of a secondary nature such as pseudoexfoliation material, ocular inflammation or pigment depositions on the corneal endothelium. Primary open-angle glaucoma was unlikely because the high ocular pressure was strictly unilateral and there was a strong chronological relationship between the treatment with the YAG laser and the start of increased ocular pressure. To date, there have been no signs of glaucoma in the fellow untreated eye suggesting a strong causal relationship between the vitreolysis and subsequent glaucoma.

Treatment

To control the ocular pressure, the patient underwent a Baerveldt glaucoma implant. Unfortunately, 1 day after the operation the ocular pressure was measured to be 50 mm Hg due to postoperative hyphema and obstruction of the tube due to bloodcoagulation. Aqueous paracentesis was attempted several times; however, refractory increases in ocular pressure ensued. Surgical revision of the Baerveldt and washout of the blood obstructing the drainage tube was performed and the ocular pressure stabilised around 15 mm Hg with adjunctive use of dorzolamide two times per day, timolol two times per day, and bimatoprost four times a day.

Outcome and follow-up

Unfortunately, the complications associated with the Baerveldt procedure caused further glaucomatous damage and increased cupping of the optic disc, thinning of the retinal nerve fibre layer and increased corresponding visual field defect were seen. During the 6 month follow-up period, following the revision of the Baerveldt, the ocular pressure remained between 14 and 15 mm Hg and the glaucomatous damage remained stable. The target pressure was set at ≤15 mm Hg and the patient returned to a peripheral ophthalmology clinic for further controls.

Discussion

Entoptic phenomena associated with vitreous floaters have been shown to be distressing and have a large negative impact on health-related quality of life in a subset of individuals.^{4 5} YAG laser vitreolysis offers a relatively inexpensive and non-invasive therapeutic option for the treatment of floaters when compared with pars plana vitrectomy. Still, large-scale studies investigating the efficacy and safety profile of laser vitreolysis are lacking.

To the best of our knowledge, this is the second report detailing secondary open-angle glaucoma following YAG laser vitreolysis, following a case series of three eyes by Cowan et al.⁶ The patients in the report by Cowan et al were treated primarily with SLT and trabeculectomy. We opted for a Baerveldt implant because of the advanced stage of the disease and the secondary nature of the glaucoma.

Earlier reported complications following YAG laser vitreolysis include cataract formation, retinal detachment and temporary high ocular pressure.⁷ Still, Brasse et al concluded that the risk of serious complications such as retinal detachment and cataract formation development appear to be much lower when compared with conventional methods such as pars plana vitrectomy.⁸ Retrospective cohort studies seem to suggest a favourable safety profile of YAG laser vitreolysis^{9 10}; however, randomised controlled trials (RCTs) are needed to make more definitive statements regarding treatment safety.

To date, there has been only one RCT, published by Shah et al, in which 36 eyes with Weiss-ring floaters were treated with YAG vitreolysis, and the control group of patients received a sham treatment.² In this study, no serious complications were reported. A follow-up study was published recently in which the same patients were examined at an average of 2.3 years following treatment.¹¹ In this study, 3 eyes were seen to develop retinal tears not described earlier; however, there were no incidences of increased ocular pressure. This suggests that the phenomenon of chronic increased ocular pressure, and as a consequence glaucoma, may be relatively uncommon.

The risk of developing high ocular pressures may be related to the type of floater being treated. In the study by Shah et al only Weiss-ring floaters were treated, while the present case followed the treatment of a bottlebrush floater, a vitreous opacity characterised visually as diffuse brush-like strands attached to a cylindrical stem. The biochemical makeup of these floaters may be such that dispersion via YAG laser releases a large amount of protein particles which may impede the proper functioning of the trabecular meshwork. Additionally, bottlebrush floaters tend to be large in size, and necessitate higher cumulative amounts of energy until the floater is rendered optically inactive. The higher energy use may present an increased risk of developing glaucoma following vitreolysis.

This report adds to the evidence that in select cases YAG laser vitreolysis can lead to the development of chronic increased ocular pressure. Patients should be fully informed of this risk before undergoing treatment to ensure shared decision making. Seeing as there is a paucity of RCTs and long-term follow-up data available to completely elucidate treatment safety, we recommend regular ophthalmological controls, including measurements of ocular pressure, following YAG laser vitreolysis, especially if the decision is made to treat floaters other than Weiss ring type floaters.

Learning points.

• Yttrium aluminium garnet laser vitreolysis can potentially cause serious secondary open-angle glaucoma in select cases.

• We encourage monitoring of ocular pressure postintervention to allow for prompt treatment should increased ocular pressure occur.

• Topical treatment or selective laser trabeculoplasty may not be sufficient to control ocular pressure, in which case operative measures may be necessary.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).