12-month outcomes of ab interno excisional goniotomy combined with cataract surgery in primary open-angle glaucoma and normal tension glaucoma.

PURPOSE: To evaluate the efficacy and safety of excisional goniotomy performed with the Kahook Dual Blade (KDB) combined with cataract surgery in patients with pimary open angle glaucoma (POAG) and Normal Tension Glaucoma (NTG) under topical therapy. Further sub-analysis was performed to compare between 90 and 120 degrees goniotomy. METHODS: This was a prospective case series of 69 eyes from 69 adults (age 78 ± 5.9 years; male = 27, female = 42). Indications for surgery included insufficient IOP control with topical medication, glaucomatous damage progression under topical therapy and reduction of medication burden. Complete success was defined as IOP lowering below 21 mmHg without the need for topical medication. For NTG patients, complete success was defined as IOP lowering below 17 mmHg without the need for topical medication. RESULTS: IOP was significantly lowered from 19.7 ± 4.7 to 15.1 ± 2.7 at 2 months, 15.8 ± 2.3 at 6 months and 16.1 ± 3.2 at 12 months (p < 0.05) for POAG and 15.1 ± 2.5 to 14.1 ± 2.4 at 2 months, 14.1 ± 3.1 at 6 months and 13.6 ± 1.8 at 12 months (p > 0.08) for NTG, respectively. Complete success was achieved in 64% of the patients. IOP lowering under 17 mmHg without the need for topical medication was achieved in 60% of the patients at 12 months. In NTG patients (14 eyes) IOP lowering under 17 mmHg without the need for topical medication was achieved in 71%. No significant difference was recorded in terms of IOP lowering at 12 months in-between 90° and 120° of treated trabecular meshwork (p > 0.7). No severe adverse reactions were recorded in this study. CONCLUSION: One-year results show that KDB combined with cataract surgery is an effective treatment option for glaucoma patients. IOP lowering was successfully achieved in NTG patients with complete success in 70% of the patients. In our study, no significant differences were recorded in-between 90° and 120° of treated trabecular meshwork.

Predicting the development of normal tension glaucoma and related risk factors in normal tension glaucoma suspects.

This study investigated the predicted risk factors for the development of normal-tension glaucoma (NTG) in NTG suspects. A total of 684 eyes of 379 NTG suspects who were followed-up for at least 5 years were included in the study. NTG suspects were those having (1) intraocular pressure within normal range, (2) suspicious optic disc (neuroretinal rim thinning) or enlarged cup-to-disc ratio (≥ 0.6), but without definite localized retinal nerve fiber layer (RNFL) defects on red-free disc/fundus photographs, and (3) normal visual field (VF). Demographic, systemic, and ocular characteristics were determined at the time of the first visit via detailed history-taking and examination of past medical records. Various ocular parameters were assess using spectral-domain optical coherence tomography and Heidelberg retinal tomography. Conversion to NTG was defined either by the presence of a new localized RNFL defect at the superotemporal or inferotemporal region on disc/fundus red-free photographs, or presence of a glaucomatous VF defect on pattern standard deviation plots on two consecutive tests. Hazard ratios were calculated with the Cox proportional hazard model. In total, 86 (12.6%) of the 684 NTG suspects converted to NTG during the follow-up period of 69.39 ± 7.77 months. Significant (P < 0.05, Cox regression) risk factors included medication for systemic hypertension, longer axial length, worse baseline VF parameters, thinner baseline peripapillary RNFL, greater disc torsion, and lamina cribrosa (LC) thickness < 180.5 µm (using a cut-off value obtained by regression analysis). Significant (P < 0.05, Cox regression) risk factors in the non-myopic NTG suspects included medication for systemic hypertension and a LC thinner than the cut-off value. Significant (P < 0.05, Cox regression) risk factors in the myopic NTG suspects included greater disc torsion. The results indicated that 12.6% of NTG suspects converted to NTG during the 5-6-year follow-up period. NTG suspects taking medication for systemic hypertension, disc torsion of the optic disc in the inferotemporal direction, and thinner LC of the optic nerve head at baseline were at greater risk of NTG conversion. Related baseline risk factors were different between myopic and non-myopic NTG suspects.

The role of pattern electroretinograms and optical coherence tomography angiography in the diagnosis of normal-tension glaucoma.

In this study, we investigated the correlation between pattern electroretinogram (PERG) and optical coherence tomography angiography (OCTA) parameters for diagnosis in patients with normal-tension glaucoma (NTG). Forty-nine normal individuals (49 eyes) and 60 patients with NTG (60 eyes) were enrolled. OCTA and PERG parameters, such as macular vessel density (VD) and the amplitude of N35-P50 and P50-N95, were measured. Correlation analyses were performed between the parameters, and the area under the curve (AUC) was used to identify their diagnostic ability for NTG. Macular VD and the amplitude of N35-P50 and P50-N95 showed significant differences between the normal individuals and patients with NTG. Correlation between P50 and N95 amplitude and macular VD was significant in the normal and early glaucoma groups. Macular VD showed a higher AUC value (0.730) than that of P50-N95 amplitude (0.645) in the early glaucoma group. In the moderate to severe glaucoma group, the AUC value of the amplitude of P50-N95 (0.907) was higher than that of macular VD (0.876). The results indicate that PERG and OCTA parameters may identify glaucoma in its early stage, based on the severity of glaucomatous damage in patients with NTG.

Results of Neuroimaging in Patients with Atypical Normal-Tension Glaucoma.

AIM: The aim of the study was to determine the frequency of pathologies which can mimic normal-tension glaucoma (NTG), observed in neuroimaging of NTG patients, and to evaluate the frequency of pathologies in determined additional indications for neuroimaging. Material and Methods. The studied group consisted of 126 NTG patients who met at least one of the following criteria: unilateral NTG, damage in the visual field (VF) inconsistent with optic disc appearance, fast VF progression, worsening of visual acuity, predominant optic disc pallor rather than optic disc excavation, diagnosis under the age of 50, and scotoma in VF restricted by a vertical line. The patients included in the research underwent MRI scans of the brain and both orbits. RESULTS: After neuroimaging, the results of 29 (23%) patients were qualified as positive; 18 (14.2%) of the identified pathologies were found to clinically affect the visual pathway. The most frequent brain pathology was intracranial meningiomas, observed in 4 patients (3.1%), followed by optic nerve sheath meningiomas diagnosed in 3 cases (2.4%), and brain glioma in 1 patient (0.8%). Pituitary gland adenomas were described in 6 patients (4.5%); 3 of the tumours were in contact with the optic chiasm. 53 (40%) patients had minimal ischemic changes in different regions of the brain. In the case of worsening BCVA or fast VF progression, the frequency of positive results was the highest (50% and 40%), whereas in the case of diagnosis at a young age and unilateral involvement, neuropathology was the rarest (0% and 6.9%). CONCLUSIONS: In the case of NTG, the decision to perform neuroimaging should be made after a detailed assessment of clinical status, rather in the event of finding the signs of possible compressive optic neuropathy than as an obligatory procedure for every patient.

What is glaucomatous optic neuropathy?

Glaucomatous optic neuropathy (GON) is the pathohistological feature of glaucoma in the optic nerve. The pathogenesis of GON has been hypothesized, to either originate from compromised mechanical conditions at the lamina cribrosa or as associated with pathological vascular involvement. From a historical perspective, glaucoma is the degeneration of retinal ganglion cells (RGC) due to the elevation of intraocular pressure (IOP). The consensus of glaucoma treatment is generally accepted as sufficient IOP reduction. Is there an additional option to treat GON from the perspective of the vascular theory? In this section, two distinguished leaders in glaucoma research advance their views and discuss the current opinions surrounding the two theories regarding the causes of GON in primary open angle glaucoma (POAG) and normal tension glaucoma (NTG).

Is "normal tension glaucoma" glaucoma?

Primary open angle glaucoma (POAG) represents a distinct disease entity with elevated intraocular pressure (IOP) as the main risk factor, even though the reasons for why the IOP is elevated remains to be elucidated. It is considered that normal tension glaucoma (NTG) is a subtype of POAG, comprising a special form of glaucomatous neurodegeneration or glaucomatous optic neuropathy (GON) almost exactly the same as that seen in POAG, but the IOP, as named, remains in the statistically normal range. Actually the disease entity of NTG has been a profound confusion and it is difficult to be accurately conceptualized. One of the reasons is that the IOP is closely linked to the occurrence of GON in POAG but not in NTG, and for the latter, it seems that GON is secondary to a number of local or systemic disorders. In recent years, increasing evidences suggest that NTG or IOP independent GON is a non-glaucomatous disease with different disease entities from POAG and with more diverse and complex etiologies. Here we hypothesized that NTG, at least for those with recognizable primary diseases, is not a glaucomatous disease; instead, it represents a group of disorders with GON as a characteristic clinical feature or phenotype.

Choroidal hypoperfusion: an indicator of low tension neovascular glaucoma.

PURPOSE: To report a case of low tension neovascular glaucoma in ocular ischemic syndrome. METHODS: An elderly man presenting with vision loss after an episode of hemiparesis was investigated to look for the cause of vision loss and treated. RESULTS: Fluorescein angiography demonstrated poor uveal perfusion and treatment with panretinal photocoagulation led to rapid closure of the angle. CONCLUSION: This case highlights the typical ophthalmic features of ocular ischemic syndrome and emphasizes the necessity of patient education and prognostication.

A Case of Glaucoma in Hereditary Spherocytosis.

PURPOSE: To report a case of glaucoma and the inherited red cell membranopathy hereditary spherocytosis diagnosed simultaneously in 2 individuals in a family. PATIENT: A 66-year-old man with normal pressure glaucoma and hereditary spherocytosis. RESULTS: This patient presented with a branch retinal vein occlusion, and normal tension glaucoma that was incidentally detected. Further history revealed that the patient's maternal grandmother also had hereditary spherocytosis and glaucoma. CONCLUSIONS: We hypothesize that glaucoma and hereditary spherocytosis may be associated. Hereditary spherocytosis may be a potential risk factor for glaucoma by causing impaired blood supply to the optic nerve.

[The Keyrole of Multiomics in the Predictive, Preventive and Personalised Medical Approach towards Glaucoma Management]. / Die Schlüsselrolle der Multiomics in Prädiktion, Prävention und personalisierter Behandlung vom Glaukom.

Glaucoma is the second leading cause of blindness, with altogether about 70 million patients registered worldwide. These facts prompt us to reconsider currently applied concepts in overall glaucoma management. Innovative strategies of predictive, preventive and personalised medicine (PPPM) are expected to considerably improve disease prevention and personalised treatment. The comprehensive PPPM measures include the application of individualised patient profiles, "phenotyping", molecular characterisation of the pre-lesions and disease stages, innovative screening programs, patient stratification, early and predictive diagnosis, targeted prevention, and the creation of personalised treatment algorithms. The main stakeholders are glaucoma-dedicated researchers, ophthalmologists, general practitioners, groups at risk, specialised medical units, affected patients and their family members, insurances, policy makers, and the diagnostic and pharmaceutical industries. Potential beneficiaries include these groups as well as society as a whole, due to financial savings in the healthcare expected.

Glaucoma in patients with shunt-treated normal pressure hydrocephalus.

OBJECTIVE: Changes in the pressure gradient between intraocular and intracranial compartments at the lamina cribrosa level are a possible explanation of normal tension glaucoma (NTG). Shunt-treated normal pressure hydrocephalus (NPH) is a model for testing whether the increase (time from disease onset to CSF shunt placement, i.e., "protection period") and decrease (time from shunt placement to observation, i.e., "exposure period") in intracranial pressure (ICP) are glaucoma protective or risk factors, respectively. The authors estimated the prevalence of NTG in patients with shunt-treated NPH and calculated the extent of optic nerve exposure to changes in the trans-lamina cribrosa gradient. METHODS: Data obtained in patients with NPH who had undergone ventriculoperitoneal (VP) shunt placement were analyzed. Patients with more than 6 months' follow-up, no pathologies associated with ICP changes or CSF dynamics disturbances, and no surgical or valve-related complications were scheduled for ophthalmic evaluation. RESULTS: Nine of 22 patients had NTG, which is about a 40-fold increase in rate compared with the rate in the general elderly population without hydrocephalus (p < 0.001). The median protection period was 12.0 months in patients with NTG and 18.0 months in those without NTG (p = 0.033). The median ICP decrease multiplied by duration of exposure in months was 76.0 mm Hg × months in the NTG group and 24.1 mm Hg × months in the no-NTG group (p = 0.048). The patients' median adjusted age (adjusted for "protection" and "exposure" times) was 85.1 years in the NTG group and 78.8 years in the no-NTG group (p = 0.001). CONCLUSIONS: A crucial risk factor for development of NTG in patients with shunt-treated NPH is the duration of optic nerve exposure to the lowering of ICP. Patients with NPH who are candidates for CSF shunting should be informed of the risk of incurring glaucoma. Longitudinal studies could provide estimates of tolerated times for a given ICP decrease.

Management of Blood Pressure in Patients with Glaucoma.

PURPOSE OF REVIEW: Ocular perfusion pressure (OPP) is defined as the difference between BP and intraocular pressure (IOP). With low BP comes low OPP and resultant ischemic damage to the optic nerve, leading to glaucoma progression. The purpose of this article is to review the literature on BP as it relates to glaucoma and to create a forum of discussion between ophthalmologists and internal medicine specialists. RECENT FINDINGS: Both high and low BP has been linked glaucoma. Low BP is particularly associated with glaucoma progression in normal-tension glaucoma (NTG) patients. Patients who have low nighttime BP readings are at highest risk of progression of their glaucoma. Internal medicine specialists and ophthalmologists should consider the relationship between BP and glaucoma when treating patients with concomitant disease. Too-low nighttime BP should be avoided. Ambulatory blood pressure monitoring is a useful tool to identify patients at greatest risk for progression.

Clinical Features of Japanese Patients with Central Retinal Vein Occlusion Complicated by Normal-Tension Glaucoma: A Retrospective Study.

PURPOSE: The association of central retinal vein occlusion (CRVO) with primary open-angle glaucoma (POAG) or ocular hypertension has been reported, and lowering intraocular pressure (IOP) helps to improve the retinal circulation in eyes with CRVO. However, the clinical features of CRVOs with normal-tension glaucoma (NTG) are not well known. Therefore, we investigated Japanese CRVO patients with NTG. METHODS: We retrospectively investigated 234 CRVO patients over 5 years, with follow-ups of more than 12 months, and evaluated the prevalence of glaucoma. RESULTS: Of the 234 CRVO patients, 18 (7.7%) were diagnosed with NTGs (n = 10) or POAGs (n = 8). Seven POAG (87.5%) and 3 NTG (30%) patients had systemic hypertension. At the initial CRVO evaluation, 6 NTGs showed a significantly increased IOP; mean IOP was 13.3 mm Hg before CRVO, 16.2 mm Hg at CRVO, and 13.5 mm Hg at the final visit. CONCLUSIONS: The proportion of NTGs with systemic hypertension was low. IOP of NTG patients was significantly elevated at the initial CRVO evaluation, even in the presence of anti-glaucoma drugs.

Retinal nerve fiber and optic disc morphology using spectral-domain optical coherence tomography in scleroderma patients.

PURPOSE: To evaluate the optic nerve head parameters and peripapillary retinal nerve fiber layer using spectral-domain optical coherence tomography (SD-OCT) in a systemic sclerosis (SSc) cohort and age-matched controls to determine whether SSc patients have an increased risk of normal-tension glaucoma (NTG). METHODS: We examined 30 patients (3 male, 27 female) with SSc and 28 age- and sex-matched controls. Retinal nerve fiber and optic disc morphology were evaluated using Cirrus SD-OCT. RESULTS: Optic disc morphology measurements including disc area, rim area, average and vertical cup/disc (C/D) ratio, and cup volume were not significantly different between the study groups. The average and 4-quadrant retinal nerve fiber layer (RNFL) measurements of the C/D >0.3 subgroups were not significantly different in the patients and controls. These values were also similar for the C/D >0.5 subgroups except that the average inferior quadrant RNFL thickness of the right eyes in the patient subgroup was significantly thinner than in the control subgroup (p<0.05). CONCLUSIONS: Our SSc cohort had relatively shorter disease duration but increased prevalence of early glaucomatous damage signs. Our findings indicate that SSc is a risk factor for developing normal-tension glaucoma. Further studies combined with visual field evaluation are necessary to identify the long-term glaucomatous effects of SSc.

Juvenile-onset Normal Tension Glaucoma From Chronic, Recurrent Low Cerebrospinal Fluid Pressure.

INTRODUCTION: The evidence for low cerebrospinal fluid pressure (CSFP) as a key parameter in the pathogenesis of glaucoma is increasing. Primate models have demonstrated the onset normal tension glaucoma (NTG) from experimentally induced chronic intrathecal hypotension; an approach not possible in human subjects. CASE PRESENTATION: A 27-year-old man presented with a central scotoma in his left eye. He had undergone 8 CSF shunt revision procedures over a 25-year period secondary to recurrent low CSFP following surgical excision of a pinealoblastoma, aged 2. A focal nerve fiber layer defect was detected in the left eye associated with reduced retinal sensitivity on microperimetry. Three adjacent optic disc hemorrhages had been documented in the same position over an 18-month period. A diagnosis of left-sided NTG was made; the patient was started on Latanoprost 0.005%. A new generation CSF shunting device (ProGAV)-which neutralizes CSFP fluctuations analogously to trabeculectomy surgery for intraocular pressure-was considered necessary in this patient to alleviate persistent headaches and reduce the risk of progressive glaucomatous visual loss. CONCLUSIONS: This exceptional case illustrates how premature onset NTG may occur as a result of chronic, recurrent intrathecal hypotension-a "pure" human model. We describe an original management approach of implanting an adjustable, programmable CSF shunt valve (ProGAV) to reduce fluctuations in the translaminar cribrosa pressure difference, and reduce the risk of glaucomatous visual loss.

Update on the Prevalence, Etiology, Diagnosis, and Monitoring of Normal-Tension Glaucoma.

Glaucoma is a leading cause of blindness worldwide. Normal-tension glaucoma (NTG) is a type of open-angle glaucoma with intraocular pressure measurements always 21 mm Hg or less. A controversy surrounding NTG is the question of whether it should be regarded as a disease within the spectrum of primary open-angle glaucoma or as a distinctive disease entity. Nonetheless, NTG does have distinctive features compared with primary open-angle glaucoma: intraocular pressure-independent risk factors for development of NTG, characteristic patterns of structural and functional damage, and a unique disease course. This review provides an overview and update on the current issues surrounding the prevalence, etiology, diagnosis, and monitoring of NTG.

Progression of Normal-Tension Glaucoma After Ventriculoperitoneal Shunt to Decrease Cerebrospinal Fluid Pressure.

PURPOSE: To report a case of worsening normal-tension glaucoma immediately following ventriculoperitoneal (VP) shunt placement to lower cerebrospinal fluid pressure (CSFP). METHODS: The clinical records of the patient were reviewed retrospectively. Observations were made and collated as the case progressed. RESULTS: A 93-year-old white woman previously diagnosed with normal-tension glaucoma underwent placement of a VP shunt with a Codman-Hakim programmable valve for normal pressure hydrocephalus. Shortly after the procedure, progressive visual field loss was noted in both eyes and new optic disc hemorrhages were seen in the patient's right eye. The hemorrhages resolved, but the patient had recurrent complaints of poor gait, memory, and mentation. The CSFP was lowered by reprogramming the Codman-Hakim valve. The patient's visual fields again worsened in both eyes and a new disc hemorrhage was seen in the right eye. A year later, a new disc hemorrhage was seen in the patient's left eye. The CSFP was raised by reprogramming the VP shunt. Before the placement of the VP shunt, no optic disc hemorrhages had been observed. CONCLUSION: This case suggests that relatively low CSFP is a contributor to worsening normal-tension glaucoma, probably by increasing translaminar pressure gradient of the optic nerve.

''The association of normal tension glaucoma with Buerger's disease: a case report''.

BACKGROUND: To report a case of a 48-year-old man with Buerger's disease who presented with bilateral normal-tension glaucoma (NTG). CASE PRESENTATION: A 48-year-old man who had been diagnosed with Buerger's disease 12 years ago, and received bilateral below-the-knee amputations for ischemic ulcers of the lower limbs, presented at our clinic due to a sudden loss of visual acuity in the left eye. A fundus exam revealed a cup-to-disc ratio of 0.5 for the right eye and 0.8 for the left eye, arteriolar constriction in both eyes, retinal edema in the inferopapillary area, and splinter hemorrhages and soft exudate in the left eye. We diagnosed the patient as having acute nasal branch retinal artery occlusion in the left eye and bilateral NTG, as a result of the ophthalmologic examination and the other findings. CONCLUSION: Although the pathomechanism of NTG is still unknown, previous studies have suggested that patients with NTG show a higher prevalence of vasospastic disorders. We present the second report of NTG associated with Buerger's disease to be described in the literature.

Metabolic syndrome as a risk factor in normal-tension glaucoma.

PURPOSE: To determine whether normal-tension glaucoma (NTG) is associated with metabolic syndrome and to evaluate which components of metabolic syndrome are related to NTG. METHODS: This study included 18240 participants who underwent health check-ups including fundus photography and intraocular pressure measurements. For NTG diagnosis, all participants with findings suggestive of glaucoma completed a further glaucoma evaluation, including applanation tonometry, gonioscopy and standard automated perimetry. The National Cholesterol Education Program Adult Treatment Panel III guideline was used to characterize metabolic syndrome. RESULTS: Of the 18240 participants, 3635 (19.9%) had metabolic syndrome and 300 (1.6%) were diagnosed with NTG. The prevalence of NTG was 1.5% in subjects without metabolic syndrome and 2.1% in subjects with metabolic syndrome. The presence of metabolic syndrome was not significantly associated with NTG (p = 0.067). There were significant associations of NTG with hypertension and impaired glucose tolerance (IGT) among the individual components of metabolic syndrome (OR, 1.53; 95% CI, 1.20-1.94; p = 0.001 and OR, 1.47; 95% CI, 1.12-1.94; p = 0.006). NTG was positively associated with the number of metabolic syndrome components (OR, 1.10; p = 0.040). Multivariable analysis showed the prevalence of NTG to be significantly higher in participants aged between 50 and 70 years relative to those aged 40 to 50 years, male gender, participants with higher baseline intraocular pressure, hypertension and IGT. CONCLUSIONS: Of the metabolic syndrome components, hypertension and IGT contributed to an increased risk of NTG. These findings suggest that metabolic syndrome components may play a role in the pathogenesis of NTG.

Normal-tension glaucoma and obstructive sleep apnea syndrome: a prospective study.

BACKGROUND: Today, identified risk factors for normal-tension glaucoma (NTG) include abnormal ocular blood flow, abnormal blood coagulation, systemic hypotension, ischemic vascular disorders, and autoimmune diseases. However, pathogenesis of the condition remains unclear. On the other hand, there are also a few studies suggesting that the obstructive sleep apnea syndrome (OSAS) may compromise optic nerve head perfusion and cause glaucomatous optic neuropathy by creating transient hypoxemia and increasing vascular resistance. In this study, we evaluated the possible association between OSAS and NTG. METHODS: We recruited 24 patients with NTG and 24 age and sex matched controls who were also similar for systemic risk factors such as diabetes mellitus (DM), hypertension (HT) and hypercholesterolemia. All patients and controls underwent over-night polysomnography (PSG) for the diagnosis of OSAS and calculation of Apnea-Hypopnea Index (AHI). RESULTS: Patients and controls were statistically similar in terms of age, sex, gender, smoking, systemic risk factors, neck circumference and body mass index. The subjects with AHI ≥ 20 were accepted as OSAS. Ten (41.7%) of 24 patients with NTG and 3 (12.5%) of 24 controls had OSAS (p < 0.05). CONCLUSIONS: The prevalence of OSAS was higher in patients with NTG and the difference between patient and control groups was statistically significant (p < 0.05).

Measurement of subfoveal choroidal thickness in normal-tension glaucoma in Korean patients.

PURPOSE: To evaluate subfoveal choroidal thickness (CT) in eyes with normal-tension glaucoma (NTG) in patients who were visualized by enhanced depth imaging optical coherence tomography. METHODS: In this observational, comparative case series, subfoveal CT was measured with enhanced depth imaging optical coherence tomography in 35 eyes of normal individuals and 32 eyes of patients with NTG. Subfoveal CT in each eye was analyzed by measuring the vertical distance from Bruch membrane to the innermost sclera layer. RESULTS: The mean subfoveal CT in the normal individual group and the NTG patient group were 300.0±52.7 and 289.5±100.4 µm, respectively. There was no difference in subfoveal CT in the 2 groups (P=0.60). The mean subfoveal CT in all subjects was significantly correlated negatively with age only (P=0.03). CONCLUSIONS: The subfoveal CT does not differ between the eyes of the normal individual group and the eyes in the NTG patient group, suggesting that CT may not play a role in the pathogenesis of NTG.