Uniocular Primary Open Angle Glaucoma: An Unusual Case Report from Bangladesh

Purpose: To describe the case of a uniocular patient with advanced primary open-angle glaucoma (POAG) and age-related cataract in the right eye and microphthalmic left eye. Methods: A 73-year-old one-eyed man presented with four years of the painless, progressive dimness of vision in the right eye. The vision was 6/18 in the right eye, whereas the left eye had no light perception (NPL). In the left eye, severe ptosis and microphthalmos were detected, while the right eye had age-related cataracts, an open anterior chamber angle, intraocular pressure (IOP) of 30 mmHg, and progressive glaucomatous optic neuropathy. The IOP was dropped to 22 mmHg after a topical Timolol maleate (0.5%), Brimonidine tartrate (0.2%), and Brinzolamide (1%). As the patient had mature cataract, advanced glaucomatous optic nerve damage, target IOP was not reached, and adherence issues with antiglaucoma medications, the decision was made to proceed with cataract extraction combined with augmented trabeculectomy with mitomycin-C (MMC). Results: There were no intraoperative complications. Over one year, the IOP was maintained in the 12 - 14 mmHg range without antiglaucoma drugs (AGM). Conclusion: In advanced glaucoma patients, combined phaco-trabeculectomy operations can considerably lower IOP and drug load or compliance concerns with antiglaucoma drugs. This case represented an e�cient and safe surgical technique for uniocular advanced primary open-angle glaucoma (POAG), particularly in a developing country like Bangladesh.


Introduction
Open-angle glaucoma is a degenerative optic neuropathy characterized by optic nerve head excavation and visual eld abnormalities with an open anterior chamber angle.(Shields, 2008) Mechanical trauma to the optic nerve occurs in primary open-angle glaucoma (POAG) due to high intraocular pressure (IOP), which is recognized to be a major component in the development and progression of glaucoma.(Shields, 2008) The pathophysiology is unknown, however it is likely to incorporate a wide variety of degenerative events that share the nal common route of progressive loss of retinal ganglion cells with axons.(Yanoff & Sassani, 2015) As glaucoma damage is permanent, the best possible care now depends on early diagnosis and treatment to reduce the risk of development and progression of vision impairment.Traditionally, the rstline therapy for glaucoma has been medical care with topical intraocular pressure lowering medications.However, current guidelines, such as those issued by the United Kingdom's National Institute of Clinical Excellence (NICE), suggest that surgery may be an acceptable rst-line therapy for individuals with advanced glaucoma at the time of diagnosis.(Foulsham et al., 2014) Microphthalmos occurs when the eye is smaller than normal by at least two standard deviations (SD) and can be complicated or simple depending on the presence or absence of other ocular anatomical abnormalities.The birth prevalence of microphthalmia has been reported to be 14 per 100,000 people.
Anophthalmia can coexist with microphthalmia in one-third of cases.(Verma & FitzPatrick, 2007) The aetiology of microphthalmia is complicated, involving gestational infections, environmental, monogenic, and chromosomal disorders.Microphthalmia is substantially more common in newborn infants with low birth weights and gestational ages.SOX2 has been recognized as a signi cant cause among monogenic causes.PAX6, OTX2, CHX10, and RAX are additional linked genes.(Faivre et al., 2006) A combination of clinical features, histopathological examination, imaging (ultrasonography and CT/MR scanning), and genetic analysis can be used to make a diagnosis both before and after birth.
McLean's research for orbital cyst with microphthalmos documented the treatment protocol employed at Moor elds Eye Hospital, which is primarily focused on early and intensive use of conformers and eventually replaced by an orbital implant and ocular prosthesis.(McLean, 2003) The purpose of this research is to describe the case of a microphthalmic one-eyed patient with advanced glaucoma and cataract who displayed well-controlled IOP while preserving good vision following phacotrabeculectomy enhanced with MMC without any medication load.

Case Presentation
A 73 year-old male, presented with painless, gradual dimness of vision, in the right eye for the last 4 years.He also gave history of no vision in left eye since birth and no history of trauma or surgery to his left eye, veri ed by his brother, who brought him for eye check-up.There was no history of consanguineous marriage and other sibling was normal, no other chronic medical or systemic illness was present.There were no clinical signs of systemic connections such as facial abnormalities, webbed hands, lid coloboma, preauricular skin tags, cleft lip, hydrocephalus, microcephaly, or convulsions.
On ocular examination, his left eye showed severe ptosis (Figure 1A), best corrected visual acuity in the right eye was 6/36 (with -1.75 DSph) and no perception of light (NPL) in the left eye.Central corneal thickness (CCT: 563 micron) corrected intraocular pressure was 30 mmHg in the right eye by Goldmann applanation tonometry.
On slitlamp examination, right eye showed grade 3 nuclear sclerosis with cortical changes in the lens and a sectoral anterior capsular brosis (Figure 1B).Left eye showed microphthalmia (Figure 1C), but ocular adnexa was in normal condition.Gonioscopy of the right eye showed Grade-4 open anterior chamber angle in all four quadrants with no notable pathological changes (Figure 1D).Dilated fundus examination of the right eye showed advanced glaucomatous optic nerve changes with tigroid fundus (Figure 1E), supported by Humphrey visual eld change (dense superior arcuate scotoma; (Figure 2A) and optical coherence tomography (OCT) of the optic nerve head showed extensive thinning of the retinal nerve ber layer (RNFL) (Figure 2B).B-scan ultrasonogram of the left eye showed dense vitreous opacities with thickened sclera which persisted in both high and low gain and short axial length of 9.77 mm (Figure 2C and 2D).
He was on regular follow-up for the last 1 year, maintaining good vision at distance (BCVA 6/18 with -0.75DCyl@90°) and near (N6 with +2.75DSph) with IOP ranging from 12 -14 mmHg without any topical antiglaucoma drops.Patient was also advised for left eye evisceration followed by prosthetic eye implant, but he refused to do so.

Discussion
At the time of presentation, the patient in this case had advanced glaucomatous damage, as evidenced by the signi cant loss of neural tissue on optic disc examination, the extreme thinning of the RNFL on OCT, and the functional de cit, with a visual acuity of 6/36.A low target pressure is needed to reduce the risk of visual loss in such severe disease at the time of presentation, which indicates a poor prognosis.With no expectation of visual recovery, phaco-trabeculectomy with MMC surgery was offered with the sole objective of preventing vision loss.
We started topical antiglaucoma drugs to preserve vision in the right eye, where the pressure remained high at 22 mmHg after maximal tolerated glaucoma treatment.Although cataract surgery usually lowers IOP, it is inadequate in situations of uncontrolled glaucoma.Furthermore, glaucoma patients undergoing cataract surgery have a higher prevalence of postoperative IOP spikes with IOPs over 30 mmHg, which poses a substantial danger in eyes with pre-existing glaucoma.(Iancu & Corbu, 2014) With or without antiglaucoma medications, combined phaco-trabeculectomy provides superior 24-hour IOP control and protects against postoperative IOP spikes.(Liaska et al., 2014) According to the Otago Glaucoma Surgery Outcome Study, trabeculectomy and simultaneous cataract extraction resulted in improved vision.(Foulsham et al., 2014) For these reasons, we decided to perform phacotrabeculectomy.
In our case, IOP dropped from 30 mmHg preoperatively to 12 mmHg following phaco-trabeculectomy and maintained in the 12 -14 mmHg range for a year without glaucoma drops.This decline in IOP and visual recovery may look spectacular, but it must be noted that the visual prognosis remains poor due to extensive glaucomatous damage in the right eye.
Microphthalmos is one of the most prevalent ocular organogenetic abnormalities, resulting in a failure of overall eye development; several forms have been clinically described.Other ocular abnormalities may complicate it.(Ghose et al., 1991) But this patient did not have any developmental abnormalities other than left microphthalmos.
Elder discovered that microphthalmic eyes with a corneal diameter of 5 mm or less at birth were related with no perception of light in 81% of cases.(Elder, 1994) Our patient had no vision in the left microphthalmic eye.
Simple microphthalmia manifests as a typical small globe with a short axial length and normal signal/density properties of the lens and vitreous in a smaller orbit than usual.(Verma & FitzPatrick, 2007) This patient had shorter axial length of 9.77 mm with vitreous opacities in B-scan ultrasonogram.
Instead of improving sight, therapy aims to improve cosmetic appearance and maximize existing vision, if any.This patient resisted our recommendation to undergo evisceration followed by an orbital implant, and an ocular prosthesis.

Conclusion
To the best of our knowledge, this is the rst case of phaco-trabeculectomy enhanced with MMC in a patient with monocular advanced POAG and age-related cataract in the right eye with left microphthalmos.This phaco-trabeculectomy reduced IOP and medication usage while improving vision without any intraoperative issues.This instance further supports the notion that early surgery be considered in individuals with advanced glaucoma, particularly in developing countries like Bangladesh.The patient's aesthetic appearance would be considerably improved with an orbital implant and ocular prosthesis.
Declarations MII: clinical evaluation, treating surgeon, concept and design, literature review, writing of the article, critical review of manuscript, journal submission.SJK: treating ophthalmologist, took part in drafting, gave nal approval of the version to be published.

Figures
Figures

Figure 1 A
Figure 1

Figure 2 A
Figure 2

Figure 3 At
Figure 3