Normal tension glaucoma may be nocturnal disorder

NUSA DUA, Indonesia – Normal tension glaucoma is primary open-angle glaucoma in which risk factors other than, or in addition to, IOP are found to contribute to the condition, and common sleep disorders may play an important role in the disorder, according to a glaucoma expert speaking here at the Asia Pacific Academy of Ophthalmology/American Academy of Ophthalmology joint meeting.

In defining normal tension glaucoma, “what we are really talking about are risk factors in addition to IOP,” Robert Ritch, MD, said in the von Graefe Lecture.

Robert Ritch

Dr. Ritch said a host of other disorders contribute to the progression of glaucoma in addition to IOP. “About 20 years ago, people realized ischemia plays a role,” he said. “In the 21st century, we realize a whole slew of disorders are being investigated.” These include cytotoxicity, macular degeneration, genetic disorders, oxidative damage and many others.

Dr. Ritch said he hypothesized that mechanisms other than IOP are associated with systemic factors, and normal tension glaucoma itself is basically a nocturnal disorder associated with sleep disorders.

Studies have shown that there is decreased ocular blood flow in sleep apnea, as well as a 27% incidence of glaucoma in sleep apnea patients. Studies have also shown that the severity of sleep apnea correlates with the severity of glaucomatous damage, he said.

Dr. Ritch said he now takes a sleep history of all of his glaucoma patients, and he has found a “fair number of patients have been positive for sleep apnea syndrome.”

For these reasons and because of the well-documented IOP rise during sleep, Dr. Ritch said normal tension glaucoma patients with high blood pressure should not take beta-blockers before sleep.

He hypothesized that disc hemorrhages occur mainly at night, but they are not seen until patients come to the clinic during the day.

Lamellar keratoplasty for fungal keratitis

Lamellar keratoplasty may be a better option than penetrating keratoplasty in the treatment of fungal keratitis in which medical therapy is ineffective, according to a speaker.

In the Arthur Lim Award Lecture, Lixin Xie, MD, gave a detailed analysis of the benefits of lamellar keratoplasty over conjunctival flap and PK.

Lixin Xie

“The advantages of lamellar keratoplasty are a less than 10% graft rejection rate, only the infected tissue is eliminated from the cornea, and the recipient endothelium is preserved,” he said.

Complications associated with PK are immune rejection, fungal recurrence and chronic graft dysfunction. For these reasons, PK should be a last resort option, according to Dr. Xie.

“Penetrating keratoplasty is indicated when there is a full-thickness corneal infection, corneal perforation or recurrence after lamellar keratoplasty,” he said.

“Lamellar keratoplasty appears to be the best procedure for fungal keratitis,” Dr. Xie concluded. “Lamellar keratoplasty is the first option when the ulcer does not involve all corneal layers.”

Nerve head thickness in angle-closure eyes

A study examining the topography of the optic nerve head found greater thickness in rim volume and area in eyes with primary angle-closure glaucoma than normal eyes, according to a researcher.

“Between the primary angle-closure glaucoma eyes and the normative eyes, the rim area and rim volume were significantly larger in the primary angle-closure glaucoma eyes, particularly in the nasal side of the optic head,” Goji Tomita, MD, said.

Dr. Tomita presented the results of a study measuring the optic nerve head with the Heidelberg Retinal Tomograph II on 28 eyes of 28 patients with primary angle-closure glaucoma and 12 eyes of 12 patients with normal eyes matched for age, refractive error and optic disc area.

The nerve area was found to be 1.5 ± 0.32 mm² in the angle-closure group and 1.22 ± 0.32 mm² in the normative eyes. Rim volume was 0.37 ± 0.10 mm³ in the angle-closure eyes compared with 0.27 ± 0.10 mm³ in the normative eyes, Dr. Tomita showed.

“In primary angle-closure eyes, dimensions of the optic nerve head may be different from those of normative eyes,” Dr. Tomita said.

Near vision activities during occlusion

Amblyopic patients who perform near vision activities while occluded showed greater visual acuity improvement than those who underwent occlusion alone, a researcher said.

“Near visual activities enhance the effect of occlusion therapy, which results in better improvement of visual acuity than occlusion therapy without near activities,” Aldiana Halim, MD, said.

Dr. Halim presented a study looking at 60 children 4 to 10 years old with anisometropic amblyopia; they were randomly assigned to two groups and followed from May to October 2007. The children were all occluded for 2 hours daily for 5 weeks, but one group of 30 was occluded with the expectation of completing near vision activities and the second group of 30 was occluded without near activities. The two groups were analyzed using t-test.

Although visual acuity differences were not significant, the improvement in visual acuity was; the near visual activities group acuity improved by mean 0.26 logMAR units and the non-near visual activities group improved by 0.19 logMAR units.

Patients were monitored for compliance with calendar fulfillment, weekly phone calls and meetings, as well as completion of two pictures in a painting book for the near activities group.

RLE effective in hyperopia

Refractive lens exchange for moderate and high hyperopia was shown to be safe and successful in a long-term study.

“Clear lensectomy for hyperopia is predictable and extremely safe. Results are acceptable for monofocal lenses and extremely good for multifocal lenses,” Amit Tarafdar, MD, said.

The study looked at 153 eyes with a mean refraction of +5.29 D, mean age of 52 years and mean follow-up of more than 5 years. The researchers implanted the eyes with one of three IOLs.

Dr. Tarafdar showed that mean refraction improved from +5.29 D to 0.04 D, and near uncorrected visual acuity was J1 in more than 90% of patients. There were no intraoperative complications, no long-term postoperative complications and no retinal detachments.

“Retinal detachment after uncomplicated RLE seems to be nonexistent in moderate and high hyperopia,” he said.

Baseline VEGF levels predict resistance

Aqueous VEGF levels measured at baseline correlated to persistent leakage at 3 months, a small study showed, and a researcher suggested this could help tailor future treatments.

“Higher aqueous VEGF concentration at baseline was associated with an increased risk of persistent leakage at 3 months,” Timothy Y.Y. Lai, MD, FRCS, said.

Dr. Lai presented a study of 50 eyes of 50 patients with subfoveal CNV, all of whom underwent three monthly load doses of intravitreal Avastin (bevacizumab, Genentech). Fluorescein angiography was performed at baseline and month 3, and aqueous tap was performed before injections at baseline and then again at month 1 and month 3.

Eyes with persistent leakage on angiography had significantly higher baseline VEGF levels than those who showed no leakage; eyes within the highest quartile of VEGF at baseline were the most likely to have persistent leakage at 3 months. After examination with a logistic regression model, baseline aqueous VEGF level was the only significant factor associated with persistent leakage at 3 months.

“We might be able to use this VEGF level to tailor our anti-VEGF therapy. For example, we might consider offering more anti-VEGF injections in patients with high initial VEGF level and we have to offer closer monitoring in case they have a higher VEGF level,” Dr. Lai said.