Scanning laser polarimetry in patients with acute attack of primary angle closure

Relationship between preoperative high intraocular pressure and retinal nerve fibre layer thinning after glaucoma surgery

Recent reports show varying results regarding peripapillary retinal nerve fibre layer (RNFL) thickness after intraocular pressure (IOP)-lowering glaucoma surgery. We hypothesised that different levels of the preoperative IOP influence RNFL thickness. A total of 60 patients (60 eyes) with glaucoma, who underwent glaucoma surgery and had a stable postoperative mean IOP < 22 mmHg, were enrolled. The RNFL thickness was measured using spectral domain optical coherence tomography, before and at 3–6 months after surgery. The preoperative peak IOP, 37.4 ± 10.8 mmHg, decreased to a postoperative mean IOP of 14.8 ± 3.5 mmHg (p < 0.001). The average RNFL thickness was significantly reduced from 75.6 ± 17.7 μm to 70.2 ± 15.8 μm (p < 0.001). In subgroup analyses, only patients with a preoperative peak IOP ≥ median value (37 mmHg) exhibited significant RNFL thinning (9.7 ± 6.6 μm, p < 0.001) associated with a higher preoperative peak IOP (r = 0.475, p = 0.008). The RNFL thinning was evident for a few months after glaucoma surgery in patients with a higher preoperative peak IOP, although the postoperative IOP was stable.

Cross-sectional study of the retinal nerve fiber layer thickness at 7 years after an acute episode of unilateral primary acute angle closure

The purpose of this article is to investigate the long-term retinal nerve fiber layer (RNFL) status and determinants of RNFL thinning after an episode of unilateral primary acute angle closure (AAC). This cross-sectional study analyzed the medical records of consecutive patients with a single episode of unilateral AAC from 1999 to 2009 in Hong Kong. The peripapillary RNFL thickness was correlated with age, gender, presenting intraocular pressure (IOP), time to laser iridotomy, time to cataract extraction, follow-up duration, as well as the last IOP, vertical cup-to-disc ratio (CDR), and vision. The fellow uninvolved eye was used as a proxy comparison of RNFL loss in the attack eye. In 40 eligible patients, the mean age was 68.3 ± 8.7 years with a male-to-female ratio of 1:7. The mean presenting IOP was 49.2 ± 14.0 mm Hg and the time from presentation to laser iridotomy was 6.7 ± 6.9 days. Forty percent of subjects received a cataract extraction at 3.2 ± 2.9 years after the attack. The last IOP, CDR, and LogMAR vision were 16.0 ± 3.8 mm Hg, 0.6 ± 0.2, and 0.6 ± 0.6 LogMAR units, respectively, at 7.9 ± 2.4 years. The RNFL thickness in the attack eye (69.2 ± 19.1 μm) was 25.2 ± 17.9% thinner than the fellow eye (93.0 ± 17.8 μm) at 7.5 ± 2.9 years post-AAC. Using univariate analysis, the last vertical CDR (odds ratio [OR] = 17.2, P = 0.049) and LogMAR visual acuity (VA) (OR = 6.6, P = 0.03) were the only significant predictors for RNFL thinning whereas none of the other covariates showed significant associations (P > 0.1). At 7.5 years following unilateral AAC, the RNFL thickness was 25% thinner than the fellow eye. CDR enlargement and poor VA were the only significant predictors for RNFL loss.

The longitudinal changes of the visual field in an Asian population with primary angle-closure glaucoma with and without an acute attack

PURPOSE

To investigate the longitudinal changes of visual field (VF) in Asian patients with primary angle-closure glaucoma (PACG) occurring with and without an acute attack.

METHODS

In this retrospective case series, 87 consecutive patients diagnosed with bilateral PACG during the period from 2000 to 2010 were included. The eyes of the enrolled patients were categorized into 2 groups: PACG with 1 documented episode of an acute episode in the affected eye (APACG); PACG without a previous documented acute episode in the fellow eye (CPACG). The historical change in the VF in both groups was assessed every 3 months for >2 years.

RESULTS

Of the 174 eyes included in the study, 87 eyes belonged to the APACG group, and 87 eyes belonged to the CPACG group. The mean deviation (MD) in the APACG group decreased significantly from -6.22 to -6.73 dB between the 6- and 9-month follow-up periods (P=0.03). There were significant differences between the 2 groups in the MD index from the 9- to 24-month follow-up. The corrected pattern standard deviation (CPSD) in the APACG group increased significantly from 3.61 to 3.71 dB between the 6- and 9-month follow-up periods (P=0.04). The CPSD index was higher in the APACG group than in the CPACG group from the 9- to 24-month follow-up, which was a statistically significant difference.

CONCLUSIONS

Glaucomatous VF damage in Asian patients with APACG was detected after a 6-month follow-up period, despite the presence of laser peripheral iridotomy in this population. In the patients with CPACG, there was no significant difference in the MD and CPSD during the follow-up period. Patients with APACG would benefit from regular monitoring of the decline in the VF.

Measurement of retinal nerve fiber layer in primary acute angle closure glaucoma by optical coherence tomography

PURPOSE

To detect the objective structure changes of the retinal nerve fiber layer (RNFL) in primary acute angle closure glaucoma (PAACG) and to evaluate the efficacy of quantitative assessment of RNFL thickness with optical coherence tomography (OCT).

PATIENTS AND METHODS

Forty patients who had unilateral PAACG attack in the first 4 months after remission and 40 single eyes from 40 normal controls were enrolled in this cross-sectional study. For all cases, PAACG had resolved after treatment. Using the Stratus OCT, the RNFL was assessed in both eyes within 2 weeks after PAACG, and again after 4 months. The OCT parameters were compared among normal controls, the unaffected fellow eyes, and the attacked eyes within 2 weeks and at 4 months after remission. Of the 40 patients, 14 PAACG patients underwent 5 times measurements, respectively, within 2 weeks and at 1, 2, 3, and 4 months after intraocular pressure was controlled. Differences between affected eyes and fellow eyes for the mean RNFL thickness at various periods after remission were also compared.

RESULTS

RNFL of the PAACG eyes became thicker (average: 142.6+/-22.9 microm) within 2 weeks and thinner (average: 83.6+/-19.8 microm) at 4 months after acute strike compared with the fellow unaffected and normal eyes. Significant differences were demonstrated comparing the average and 4-quadrant RNFL thicknesses for the attacked eyes with those of the normal controls (P<0.001 to 0.001) and fellow eyes (P<0.001 to 0.002) using 1-way analysis both within 2 weeks and at 4 months after remission. There was significant difference in the RNFL thickness among the 5 time points after intraocular pressure controlled in the acute strike group (P<0.001).

CONCLUSIONS

Using OCT, RNFL thickness was found to increase in eyes immediately after an episode of PAACG followed by a decrease in RNFL thickness over time (up to 3 mo). This detection can aid in better understanding the pathologic retinal changes involved in PAACG, and help in the assessment and management of these patients.

Acute retinal ganglion cell injury caused by intraocular pressure spikes is mediated by endogenous extracellular ATP

Elevated intraocular pressure may lead to retinal ganglion cell injury and consequent visual deficits. Chronic intraocular pressure increase is a major risk factor for glaucoma, a leading blinding disease, and permanent visual deficits can also occur following acute pressure increments due to trauma, acute glaucoma or refractive surgery. How pressure affects retinal neurons is not firmly established. Mechanical damage at the optic nerve head, reduced blood supply, inflammation and cytotoxic factors have all been called into play. Reasoning that the analysis of retinal neurons soon after pressure elevation would provide useful cues, we imaged individual ganglion cells in isolated rat retinas before and after short hydrostatic pressure increments. We found that slowly rising pressure to peaks observed in trauma, acute glaucoma or refractive surgery (50-90 mmHg) did not damage ganglion cells, whereas a rapid 1 min pulse to 50 mmHg injured 30% of these cells within 1 h. The severity of damage and the number of affected cells increased with stronger or repeated insults. Degrading extracellular ATP or blocking the P2X receptors for ATP prevented acute pressure-induced damage in ganglion cells. Similar effects were observed in vivo. A short intraocular pressure transient increased extracellular ATP levels in the eye fluids and damaged ganglion cells within 1 h. Reducing extracellular ATP in the eye prevented damage to ganglion cells and accelerated recovery of their response to light. These data show that rapid pressure transients induce acute ganglion cell injury and unveil the causal role of extracellular ATP elevation in such injury.

Comparison of Glaucomatous Optic Nerve Damage in Primary Angle-Closure Glaucoma with and without Acute Attack

PURPOSE

To compare the glaucomatous optic nerve damage in primary angle-closure glaucoma (PACG) with acute attack (acute PACG; AACG) and PACG without acute attack (chronic PACG; CACG).

METHODS

The study subjects were 84 normal individuals, 130 AACG patients, and 86 CACG patients. Color optic disc photographs were evaluated for the presence or absence of 10 qualitative signs to differentiate between normal and glaucomatous optic discs.

RESULTS

Abnormally shaped rim width (alteration of ISN'T rule), bared circumlinear vessel, vessel bayonetting, rim width narrower than the temporal sector, and zone beta (nasal and superotemporal sectors) were detected more frequently in the CACG group than in the AACG group (P<0.05). The most accurate qualitative sign was abnormally shaped rim width in both groups. The specificity and sensitivity of abnormally shaped rim width were 71.4% and 60.8% for AACG, and 71.4% and 81.4% for CACG, respectively.

CONCLUSIONS

The optic disc damage is greater in CACG than in AACG.