Early U.S. cross-linking study results positive for treating keratoconus, ectasia

Marguerite B. McDonald

KOLOA, Hawaii – Interim results of the U.S. corneal cross-linking clinical trial are positive enough for one speaker here at Hawaiian Eye 2010 to conclude that the procedure will become the standard of care in ectatic corneal disease.

Marguerite B. McDonald, MD, presented early results of the prospective, block-randomized clinical trial of 292 eyes with either keratoconus or ectasia after LASIK or PRK. Maximum keratometric value, best corrected visual acuity, uncorrected visual acuity and manifest refraction are being measured in the study.

“The interim conclusions look pretty good,” she said. “[Corneal cross-linking] halts the progression of keratoconus and ectasia after LASIK.”

She said cross-linking also decreases corneal curvature and thickness and improves uncorrected and best corrected visual acuity to statistically significant degrees.

“We think it will become the standard of care for the treatment of corneal ectatic disease,” Dr. McDonald said.

Primary Care Optometry News Editorial Board member John A. Hovanesian, MD, commented that on an international basis, 10 years of favorable clinical experience with this procedure in keratoconus and post-LASIK ectasia have made this the standard of care.

“This U.S. Food and Drug Administration study of corneal cross-linking has also suggested that this procedure halts progressive keratoconus and may reverse some corneal steepening,” he said. “As a less invasive approach than lamellar or penetrating keratoplasty, cross-linking is likely to take an important place in the growing spectrum of procedures for ectatic disease.”

Novel therapeutics effective treatment for blepharitis

Both azithromycin ophthalmic solution and tobramycin and dexamethasone ophthalmic suspension have been shown to be effective in treating blepharitis and should be considered in clinical practice, a speaker said.

“Patients with acute exacerbations of meibomian gland disease need an effective treatment to address their signs and symptoms. If you are not already incorporating [AzaSite and TobraDex ST] into your practice, you should,” David A. Goldman, MD, said.

In clinical studies, AzaSite (1% azithromycin ophthalmic solution, Inspire Pharmaceuticals) “demonstrated significant improvements in meibomian gland plugging, meibomian gland secretions and eyelid redness,” Dr. Goldman said.

In a comparison of TobraDex (tobramycin and dexamethasone, Alcon) and its new suspension, TobraDex ST (tobramycin 0.3%, dexamethasone 0.05% ophthalmic suspension, Alcon), data have shown only a 3% settling of TobraDex ST compared with 61% in TobraDex after 24 hours, he said.

“TobraDex ST demonstrated improved suspension formulation characteristics, enhanced pharmacokinetic distribution … and improved bactericidal characteristics compared with TobraDex,” Dr. Goldman said.

Test helps identify conjunctivochalasis in stubborn dry eye

A simple thumb test may help diagnose conjunctivochalasis in recalcitrant dry eye cases and result in a satisfied patient after surgical treatment, a speaker said.

“Conjunctival chalasis is very easy to confuse with dry eye, and a simple thumb pressure test helps identify it,” John A. Hovanesian, MD, said.

While applying pressure to the lower outer eyelid with your thumb, have the patient move their eye up and down to identify the area of chemosis, Dr. Hovanesian said.

In a review of cases at his clinic, Dr. Hovanesian found eight patients who had a diagnosis of refractory dry eye who tested positive for conjunctivochalasis. He found that all patients were older than 50 years and had undergone previous ocular surgery. After a positive identification, all patients underwent an excision and amniotic membrane transplant with a fibrin tissue adhesive, and all patients had a complete resolution of symptoms.

“My take-home message today is to consider conjunctivochalasis in recalcitrant cases of ‘dry eye,’” he said.

Technology evolving toward continuous IOP monitoring

Technology is being rapidly developed to enable IOP monitoring outside of the clinic, but no technology currently available is ideal, according to one speaker.

Arthur J. Sit

Arthur J. Sit, MD, reviewed the current technologies being developed for continuous IOP monitoring. He said there are three primary paradigms to continuous IOP monitoring: self-tonometry, permanent continuous measurement and temporary continuous measurement.

“Self-tonometry is technically the easiest solution, but it is difficult for many patients, can be expensive and does not cover the nocturnal period,” Dr. Sit said.

Permanent continuous monitoring can be achieved with an implant and wireless device. It has a potential use for advanced glaucoma cases or glaucoma surgery and would use an alarm concept, he said.

Two concepts being developed for this are a bubble tonometer and an IOP-IOL device. Studies were presented on this technology at the 2009 Association for Research in Vision and Ophthalmology meeting.

“The problems with these devices are the sensitivity to the distance between the device and the orientation of the implant,” he said. Other problems include that the devices may be more prone to noise interference and that there could be long-term stability issues.

Contact lens-based temporary continuous monitoring is another promising technology, but there are issues with IOP noise, discomfort and patient adherence and variations in corneal thickness as well as pressure differences with eyes open vs. closed, Dr. Sit said.

Katrina Altersitz, Bryan Bechtel and David W. Mullin
PCON Correspondents

Retina 2010 focuses on diagnostics, AMD

KOLOA, Hawaii – Different image patterns on optical coherence tomography and fluorescein angiography may signify distinct causes of diabetic macular edema (DME), which may be a tip-off to the most effective treatment plan, according to a speaker here at Retina 2010.

“Is the biology different — and, therefore, the treatment different — between focal and diffuse leakage?” Scott W. Cousins, MD, asked.

A focal leakage pattern exemplified by speckled thickening on OCT and leakage on fluorescein angiography may typify a vasogenic mechanism, most likely due to leaking microaneurysms, Dr. Cousins said. These patients may respond best to laser therapy.

If OCT shows presence of cysts, and fluorescein angiography the presence of significant leakage, an underlying toxic mechanism may be the ultimate cause of DME, suggesting that pharmacotherapy may be appropriate, Dr. Cousins said. In these cases, the diffuse leakage pattern may result from the inability of Müller cells to pump blood into the vasculature, leading to the swollen appearance recognized as a cyst.

In diffuse presentations, poor peripheral perfusion of the retina appears to suggest overexpression of VEGF, indicating anti-VEGF therapy, whereas significant peripheral perfusion suggests an inflammatory etiology, which portends a better response to steroid therapy, he said.

Spectral-domain OCT may unveil findings missed by time domain

Broader bandwidth light sources that penetrate deeper into retinal tissue and faster scanning speeds available through spectral-domain optical coherence tomography may elucidate clinical findings relevant to age-related macular degeneration that time-domain technology might miss, according to another speaker.

Time-domain devices, because they produce an image by capturing six scans over the foveal center, map about 5% of the retina, whereas spectral-domain devices are capable of capturing 100% of the retina, Linda A. Lam, MD, said.

“Smaller lesions may fall between those six foveal scans,” Dr. Lam said.

In a retrospective review of 62 eyes of 45 patients imaged simultaneously with time-domain and spectral-domain OCT at the Doheny Eye Institute within 1 week of injection of Avastin (bevacizumab, Genentech) for treatment of neovascular AMD, Dr. Lam and colleagues noted a small but not insignificant error rate in time-domain scans.

Spectral-domain scanning detected at least one clinical feature in 12 eyes (19%) that was not discovered on time-domain OCT. In six cases (10%), the spectral-domain OCT finding would have prompted a re-treatment with bevacizumab.

“Spectral-domain OCT is more sensitive for the detection of neovascular AMD features than time-domain OCT due to its better macular coverage, higher resolution and higher sensitivity,” Dr. Lam said.

Katrina Altersitz , Bryan Bechtel and David W. Mullin
PCON Correspondents

Retina 2010 focuses on diagnostics, AMD

KOLOA, Hawaii – Different image patterns on optical coherence tomography and fluorescein angiography may signify distinct causes of diabetic macular edema (DME), which may be a tip-off to the most effective treatment plan, according to a speaker here at Retina 2010. “Is the biology different — and, therefore, the treatment different — between focal and diffuse leakage?” Scott W. Cousins, MD, asked. A focal leakage pattern exemplified by speckled thickening on OCT and leakage on fluorescein angiography may typify a vasogenic mechanism, most likely due to leaking microaneurysms, Dr. Cousins said. These patients may respond best to laser therapy. If OCT shows presence of cysts, and fluorescein angiography the presence of significant leakage, an underlying toxic mechanism may be the ultimate cause of DME, suggesting that pharmacotherapy may be appropriate, Dr. Cousins said. In these cases, the diffuse leakage pattern may result from the inability of Müller cells to pump blood into the vasculature, leading to the swollen appearance recognized as a cyst. In diffuse presentations, poor peripheral perfusion of the retina appears to suggest overexpression of VEGF, indicating anti-VEGF therapy, whereas significant peripheral perfusion suggests an inflammatory etiology, which portends a better response to steroid therapy, he said. Spectral-domain OCT may unveil findings missed by time domain Broader bandwidth light sources that penetrate deeper into retinal tissue and faster scanning speeds available through spectral-domain optical coherence tomography may elucidate clinical findings relevant to age-related macular degeneration that time-domain technology might miss, according to another speaker. Time-domain devices, because they produce an image by capturing six scans over the foveal center, map about 5% of the retina, whereas spectral-domain devices are capable of capturing 100% of the retina, Linda A. Lam, MD, said. “Smaller lesions may fall between those six foveal scans,” Dr. Lam said. In a retrospective review of 62 eyes of 45 patients imaged simultaneously with time-domain and spectral-domain OCT at the Doheny Eye Institute within 1 week of injection of Avastin (bevacizumab, Genentech) for treatment of neovascular AMD, Dr. Lam and colleagues noted a small but not insignificant error rate in time-domain scans. Spectral-domain scanning detected at least one clinical feature in 12 eyes (19%) that was not discovered on time-domain OCT. In six cases (10%), the spectral-domain OCT finding would have prompted a re-treatment with bevacizumab. “Spectral-domain OCT is more sensitive for the detection of neovascular AMD features than time-domain OCT due to its better macular coverage, higher resolution and higher sensitivity,” Dr. Lam said. Katrina Altersitz , Bryan Bechtel and David W. Mullin PCON Correspondents