Reduced Accommodation Without Mydriasis After Micropulse Cyclophotocoagulation in a Young Congenital Glaucoma Patient: A Case Report

Introduction

Micropulse cyclophotocoagulation (MPCPC) is a laser-based procedure that targets the ciliary body to lower intraocular pressure (IOP). This innovative technique uses repetitive micropulses of a diode laser, with resting intervals that promote thermal dissipation and reduce collateral tissue damage. Consequently, MPCPC has fewer complications than other cyclodestructive methods [1]. However, patients with thin sclera are at increased risk for complications associated with MPCPC, as their thin sclera permits more energy absorption [2]. Thin sclera occur with myopia, previous ocular surgeries, and systemic diseases such as Marfan syndrome and osteogenesis imperfecta [2]. One of the possible complications is mydriasis, a temporary adverse effect of this procedure, resulting from damage to the short ciliary nerves. This nerve controls the ciliary muscle and pupil sphincter involved in the accommodation reflex [3]. However, reduced accommodation without mydriasis is a rare complication of MPCPC in contrast to the described cases in the literature [4–6]. We report a case of decreased accommodation without pupil dilation after MPCPC in a patient with congenital glaucoma. While such symptoms are typically attributed to nerve damage, the absence of pupillary involvement in our patient raises the possibility of selective, localized injury to the ciliary muscle itself.

Case Report

A 26-year-old woman with a known history of bilateral primary congenital glaucoma was following up at our glaucoma clinic. Her past surgical history included goniotomy as the initial procedure performed at the age of 1 year, followed by trabeculectomy 4 months later, along with peripheral iridectomy in both eyes. Her past medical history was otherwise unremarkable. At the time of presentation, she was taking topical 1% brinzolamide/0.2% brimonidine (Simbrinza) 3 times a day, 0.3% bimatoprost/5% timolol (Ganfort) once daily at bedtime, and acetazolamide (Diamox) 250 mg twice a day. Her best-corrected visual acuity (BCVA) was 20/60 in the right eye and 20/300 in the left eye. The IOP measured by Goldmann applanation tonometry was 24 mmHg in the right eye and 28 mmHg in the left eye. On slit-lamp examination, Haab’s striae were noted in the cornea, and the anterior chamber (AC) was deep and quiet in both eyes. The iris showed a patent peripheral iridectomy in both eyes. The pupils were round, reactive, and symmetric without any abnormality. The lens in the right eye was clear, while the left eye had pigments on the anterior surface of the lens. Dilated fundus examination revealed a cup-to-disc ratio of 0.80 in the right eye and 0.95 in the left eye. Gonioscopy showed open angles with high iris insertion in both eyes. Central corneal thickness (CCT) was 600 μm in the right eye and 672 μm in the left eye. Despite being on maximum medical therapy, the patient’s IOP remained uncontrolled. Therefore, MPCPC was performed in the right eye, and an Ahmed glaucoma valve surgery was performed in the left eye on the same day. The procedure was performed at a power of 2500 mW, a duty cycle of 31.3%, and a duration of 50 seconds at the superonasal quadrant and the inferior hemisphere, avoiding the superotemporal quadrant, specifically the 3 and 9 o’clock positions. One day post-operatively, the IOP was 22 mmHg in the right eye and 16 mmHg in the left eye. Her BCVA was 20/60 in the right eye and 10/125 in the left eye. During the slit-lamp examination, both eyes appeared similar to those in the preoperative assessment. Pupil exams were symmetric bilaterally. The tube and plate were well covered with conjunctive, and the tube was seen patent in the AC of the left eye. The patient was discharged home on a tapering regimen of topical steroids in both eyes. She was also given bimatoprost/timolol maleate (Ganfort) QHS and brinzolamide/brimonidine (Simbrinza)TID in the right eye. At the 2-week follow-up, she reported having blurry vision in the right eye; however, it was not documented whether the blurriness affected near or distance vision. Best-corrected visual acuity (BCVA) was 20/60 in the right eye and 20/200 in the left eye. IOP was 19 mmHg and 23 mmHg. The anterior segment examination was unremarkable, with non-dilated, reactive pupils. Due to stable visual acuity, the patient was not sent for refraction. At the 6-month follow-up, she reported persistent blurry vision. Upon further inquiry, she stated that she has only near vision disturbance in the right eye. The IOP was 19 mmHg in the right eye and 15 mmHg in the left eye. Her BCVA was 20/50 in the right eye and 20/125 in the left eye. Anterior segment examination showed round and reactive pupils equal in size bilaterally (Figure 1). The posterior segment examination result was the same as that of the preoperative examination – the macula was flat, with no striae or choroidal folds observed. The patient was sent to the optometry service for refraction. The refractive error was −5.00 sphere −3.50 cylinder at 30 degrees with a +1.50 diopter add in the right eye, and −8.00 sphere −4.50 cylinder at 15 degrees in the left eye. In comparison, the refraction in 2022 was −4.75 sphere and −4.50 cylinder at 25 degrees in the right eye, and −8.00 sphere and −4.00 cylinder at 15 degrees in the left eye, without any near add. Unfortunately, no formal testing of accommodation, such as amplitude of accommodation, was performed at that time.

The patient was managed with a glasses prescription with a near vision add of +1.5, but she refused to use them.

Discussion

The accommodation reflex is a mechanism that allows the eye to focus on near objects. It is a 3-step process involving convergence, accommodation, and pupil constriction. Accommodation refers to the contraction of the ciliary muscle, resulting in a change in lens thickness and an increase in dioptric power. The parasympathetic fiber of the short ciliary nerve innervates the ciliary muscle and the pupil sphincter. Therefore, damage to these nerves typically presents as both decreased accommodation and pupillary abnormalities. In our case, however, the patient experienced isolated accommodative loss without mydriasis, suggesting a selective insult.

The most common cause of reduced accommodation is age-related (presbyopia), whereby the lens hardens, and ciliary body contraction decreases with age. Another contributing factor in glaucoma patients is the long-term use of prostaglandin receptors agonists. A recent study by Avaki et al showed that glaucoma patients developed presbyopia and started near correction by approximately 5 years earlier than usual [7]. However, their study was conducted on middle-aged patients, and our patient is in her twenties.

Moreover, any damage to the ciliary body or pupil sphincter will result in loss of accommodation and mydriasis [3], such as damage caused by cyclodestructive procedures used in glaucoma management. MPCPC has become increasingly favored for its efficacy and improved safety profile over traditional TSCPC. Its micropulse delivery, as previously described, allows for reduced collateral damage through intermittent energy application [1]. Traditionally, continuous TSCPC has been recommended for patients with refractory advanced glaucoma; however, MPCPC has been broadened to include patients with non-refractory glaucoma who have good vision [8]. In a recent meta-analysis, the mean IOP reduction and success rates after MPCPC were 23% to 31% and 33% to 87.5%, respectively [9]. Clinical and experimental studies indicate that the rest periods in MPCPC can limit the buildup of energy in the tissues adjacent to the pigmented epithelium, reducing collateral damage [1]. Despite its efficacy and safety, complications have been reported, including hypotony, pain, inflammation, decreased visual acuity, corneal infiltrate, pupillary distortion, hyphema, lens subluxation, suprachoroidal hemorrhage, cystoid macular edema, phthisis bulbi, and sympathetic ophthalmia [5,6,10–14].

In a multicenter study by Radhakrishnan et al, of 167 eyes that underwent MPCPC, 18 eyes exhibited mydriasis, and 3 eyes had decreased accommodation that persisted at the last follow-up visit [15]. Similarly, Ling et al reported 3 cases of decreased accommodation and pupillary dilation after MPCPC. They used 2% topical pilocarpine (Zhenrui, Shandong Bausch Lomb, China), and all showed an improvement in near visual acuity [4]. Radhakrishnan et al and Ling et al speculated that diode laser MPCPC could potentially cause thermal damage to the short posterior ciliary nerves, leading to decreased accommodation and pupillary dilation [4,15]. In contrast, the pupil was not affected in our patient, and we hypothesize that MPCPC may have directly injured the ciliary muscles, causing a loss of accommodation only without mydriasis. Our patient had undergone multiple previous ocular surgeries, and it has been reported that scleral thinning is a possible complication following ocular surgeries [16]. This scleral thinning could potentiate energy absorption from the MPCPC, leading to ciliary muscle sectoral damage.

To the best of our knowledge, this is the first reported case of isolated accommodative dysfunction without mydriasis following MPCPC, highlighting a potentially underrecognized complication in young patients with prior ocular surgeries. While further research is warranted, this observation may justify including isolated accommodative dysfuction as a rare but relevant complication during preoperative counseling for selected patients undergoing MPCPC.

Conclusions

This case report presents an unusual complication of MPCPC in which the patient developed isolated accommodative dysfunction without any pupillary involvement. We hypothesize that this may be related to direct localized ciliary muscle damage, possibly potentiated by previous glaucoma surgeries and associated scleral thinning. This highlights the need to consider isolated accommodation loss as a rare but potential complication, and to include it in preoperative discussions with young, phakic patients undergoing MPCPC.