Glaucoma Mimickers: A major review of causes, diagnostic evaluation, and recommendations.

Background: Glaucoma is characterized by chronic progressive optic neuropathy with corresponding visual field changes, with or without raised intraocular pressure (IOP). When diagnosing glaucoma or monitoring its progression, the examiner has to rely on the appearance of the optic disc, characteristic retinal nerve fiber layer defects, and corresponding visual field defects. However, similar changes and symptoms may be observed in several other disorders of the optic nerve and retina that may mimic glaucoma, often leading to misdiagnosis. Methods and result: The consequences of misdiagnosis not only result in improper treatment that may impact vision but also would negatively affect the overall health, psychological well-being of the patient, and may have considerable economic implications.Conclusion: The current review describes various conditions that mimic glaucoma and the features that help differentiate these conditions from glaucoma.

Effect of Intravenous Dexmedetomidine on Intraocular Pressure in Patients Undergoing Glaucoma Surgery Under Local Anesthesia: A Pilot Study.

PRECIS: Preoperative intravenous (IV) dexmedetomidine produced a 33% reduction in intraocular pressure (IOP) within 15 minutes of administration in patients with glaucoma. PURPOSE: To evaluate the effect of preoperative IV dexmedetomidine on IOP in adult patients undergoing glaucoma surgery under local anesthesia. METHODS: In a prospective interventional case series, 12 patients with uncontrolled IOP (IOP>24 mm Hg in both the eyes) with the systemic status of American Society of Anesthesiologists (ASA) classification I-II, received IV dexmedetomidine 0.6 µg/kg 30 minutes preoperatively. The IOP of the nonsurgical eye (measured with Perkins tonometer), the heart rate (HR), and blood pressure (BP) were recorded 5 minutes prior, 15 minutes and 2 hours after IV dexmedetomidine administration, and were compared using analysis of variance and Tukey honestly significant difference tests. RESULTS: There were 4 women and 8 men with a mean age (±SD) of 60.6±10.4 years. The mean number of antiglaucoma medications was 4.3±1.3. The mean pre-dexmedetomidine IOP was 31.5±5.6 mm Hg. At 15 minutes post-dexmedetomidine administration, the mean and percentage drop in IOP were 10.2±3.2 mm Hg (P=0.001) and 33%±11%, respectively. The mean and percentage drop in systolic BP were 18±20 mm Hg (P=0.01) and 12%±14%, and drop in diastolic BP were 6.5±10 mm Hg (P=0.05) and 7%±11%, respectively. The mean and percentage drop in HR were 2±0.6 bpm (P=0.48) and 2%±13%, respectively. None of the subjects experienced any medication-related adverse effects. At 2 hours, the mean and percentage drop in IOP were 5.3±3 mm Hg and 17%±11%, respectively. CONCLUSION: In the small sample of (ASA I-II) patients studied, preoperative dexmedetomidine produced a significant drop in IOP (33%) within 15 minutes of IV administration in patients with glaucoma that was reversing at 2 hours, with a good safety profile.

Role of visual field reliability indices in ruling out glaucoma.

IMPORTANCE: Standard automated perimetry is the current criterion standard for assessment of visual field (VF) loss in glaucoma. The 3 commonly used reliability indices to judge the quality of standard automated perimetry results are fixation losses (FLs) and false-positive (FP) and false-negative (FN) response rates. However, the influence of reliability indices, when within the manufacturer-recommended limits, on VF classification has been sparsely studied. OBJECTIVE: To evaluate the role of VF reliability indices in ruling out glaucoma. DESIGN, SETTING, AND PARTICIPANTS: A cross-sectional study of 291 eyes of 291 participants referred to a tertiary eye care facility by general ophthalmologists. The participants were suspected to have glaucoma based on optic disc appearance, but the eyes were judged to be normal with physiological cupping by glaucoma experts on masked evaluation of optic disc photographs. All participants underwent VF testing with the Swedish interactive threshold algorithm standard 24-2 program. MAIN OUTCOMES AND MEASURES: Logistic regression models were used to evaluate the associations between reliability indices and FP classifications on VF testing (glaucoma hemifield test as outside normal limits and pattern standard deviation with P < .05). RESULTS: Median FL, FP, and FN response rates were 7%, 1%, and 2%, respectively. Among the 241 participants with reliable VF results (FL <20% and FP response rate <15%), the VF classification was normal in 188 (78.0%) and glaucoma (FP) in 53 (22.0%). Probability of FP VF classification was associated with FN response rates (odds ratio [OR], 1.36; 95% CI, 1.25-1.48, P < .001) but did not appear to be associated with FLs (OR, 0.96; 95% CI, 0.90-1.03, P = .30) or FP response rates (OR, 0.96; 95% CI, 0.83-1.12, P = .64). Predicted probability of FP VF classification was 9% (95% CI, 6%-14%), 40% (32%-49%), and 82% (68%-91%) at FN response rates of 0%, 8%, and 16%, respectively. CONCLUSIONS AND RELEVANCE: This study suggests that FN response rates have an effect on the ability of automated VF assessments to rule out glaucoma. Since FN response rates are ignored by the manufacturer while flagging a test as unreliable, clinicians and researchers may benefit by realizing that FN response rates can lead to FP VF classification, even when their frequencies are small.

Ability of different scanning protocols of spectral domain optical coherence tomography to diagnose preperimetric glaucoma.

PURPOSE: To evaluate the ability of the optic nerve head (ONH), retinal nerve fiber layer (RNFL), and ganglion cell complex (GCC) parameters of spectral domain optical coherence tomograph (SDOCT) in detecting preperimetric glaucoma. METHODS: In a cross-sectional study, 34 preperimetric glaucoma eyes (34 patients) and 72 control eyes (72 subjects) with large physiologic optic disc cupping underwent ONH, RNFL, and GCC imaging with SDOCT. Preperimetric glaucoma was diagnosed in the presence of glaucomatous optic neuropathy on masked evaluation of optic disc photographs by two glaucoma experts and normal visual fields. The ability of SDOCT parameters to discriminate preperimetric glaucoma eyes from eyes with large physiologic cups was evaluated by areas under the receiver operating characteristic curves (AUC), sensitivities at fixed specificities, and likelihood ratios (LR). RESULTS: All SDOCT parameters were significantly different (P < 0.05) between the two groups. The ONH, RNFL, and GCC parameters with best AUCs to differentiate preperimetric glaucoma from eyes with large physiologic cups were vertical cup to disc ratio (0.76), inferior quadrant RNFL thickness (0.76), and inferior quadrant GCC thickness (0.75), respectively. Sensitivities at 95% specificity of SDOCT parameters ranged between 15% and 29%. Likelihood ratios of outside normal limits category of parameters ranged between 3 and 11, and within normal limits category between 0.5 and 0.8. CONCLUSIONS: Diagnostic abilities of ONH, RNFL, and GCC parameters of SDOCT to differentiate preperimetric glaucoma eyes from control eyes with large physiologic cupping were only moderate.