Clinical News: Medical and Product Updates

AMD NEWS
TTT update

A new study has provided additional data on the use of transpupillary thermotherapy (TTT).

Researchers used TTT photocoagulation to treat choroidal neovascularization (CNV) secondary to AMD. The study validated previously published results on the effectiveness of TTT for occult CNV. It also showed favorable results in using TTT to treat predominantly classic CNV.

In the study, researchers used an Iris Medical OcuLight SLx laser on 44 eyes of 42 patients. Of the 44 eyes treated, 32 were predominantly occult CNV and 12 were predominantly classic CNV.

Data from a recent study involving 44 eyes of 42 patients suggest that transpupillary thermotherapy photocoagulation may be an effective treatment for predominantly classic age-related macular degeneration.

At 6 months follow-up, predominantly occult membranes were successfully closed in 78% of the eyes and were recurrent in 5% of the eyes.

Predominantly classic membranes were successfully closed in 75% of the eyes, with no recurrences.

Researchers associated this high closure rate with vision stabilization (+/-1 line) or vision improvement (>=2 lines) in 71% of patients with occult membranes and 67% of patients with classic membranes.

Br J Ophthalmol 2001; 85: 173-179.

DRY EYE
In the pipeline

Moving one step closer to FDA approval, Inspire Pharmaceuticals has initiated the Phase III clinical program for the P2Y(2) receptor agonist INS365 Ophthalmic. This drug is used for the treatment of dry eye.

INS365 Ophthalmic is a small-molecule drug that stimulates the P2Y(2) receptor, a key mediator of mucosal-surface hydration and lubrication. Accord-ing to the company, INS365 Ophthalmic enhances the eye's natural cleansing and protective systems by stimulating the release of salt, water, mucus and other natural tear components. INS365 Ophthalmic also provides hydration and lubrication of the ocular surface.

Following positive results from the Phase II program, the Phase III program will consist of two clinical trials. Approximately 1,000 patients with dry eye will enroll at 60 ophthalmology centers. The trials will compare two concentrations of INS365 Ophthalmic.

Inspire Pharmaceuticals will present the results of the Phase II study at the Association for Research in Vision and Ophthalmology meeting in April. The company anticipates that the results of the Phase III clinical trial will be available sometime next year.

German scientists believe they have discovered a link between cell phones and eye cancer.

The scientists, at the University of Essen, interviewed 188 patients suffering from uveal melanoma. They compared the cell phone use history of this group with the history of a control group of 475 people.

Results showed that those who regularly used a cell phone were three times more likely to develop uveal melanoma.

The German scientists claim this is the first study linking uveal melanoma to radio-frequency radiation exposure. However, they caution that their results need to be confirmed becasue of limitations in the study's methodology, such as the absence of data regarding ultraviolet radiation or other possible contributory variables.

Epidemiology 2001; 12: 7-12.

PRESBYOPIA
Treatment enters Phase I Trials

New technology designed to reverse presbyopia will soon enter FDA Phase I trials. The technology is in the form of an infrared laser, the IR-3000, made by SurgiLight, Inc. The IR-3000 features a proprietary infrared wavelength, a beam-shaping delivery unit and a computer-controlled scanning mechanism.

Pre-op procedures include measuring limbus thickness at various predetermined areas and opening the conjunctiva mechanically or by a laser. The IR-3000 removes holes in the scleral tissue outside the limbus to induce changes in zonular activity.

SurgiLight exhibited and demonstrated the IR-3000 at the European Society of Cataract and Refractive Surgeons conference in January. The founder of SurgiLight, J.T. Lin, Ph.D., presented two papers on the IR-3000 at the conference. Both papers stated that the IR-3000 is safe and effective for the treatment of presbyopia. Patients can be treated in both eyes and show almost no regression post-op.

SurgiLight says the surgery takes 5 to 10 minutes per eye.

ARTIFICIAL EYES
More realistic movement?

Canadian researchers believe they can make artificial eyes move in a more realistic way.

In a study published in Robotics and Autonomous Systems, researchers state that they've designed two different prototypes that detect the movement from a patient's good eye, allowing the prosthetic eye to move in tandem.

The first prototype includes a tiny motor placed in the socket behind the glass eye. Sensors on eyeglass frames pick up the movement of the good eye and transmit it to the artificial eye. The motorized eye moves accordingly.

In the second prototype, the researchers placed electrodes on the side of a patient's head, at eye level. The electrodes pick up brain waves that control eye movements. That signal pattern is transmitted to control the artificial eye.

The researchers state that their artificial eyes are still in the prototype phase. It's still too soon to assess what, if any, complications may result.

	At the Houston Veterans Affairs Medical Center, researchers measured the corneas of 83 white and 82 black Americans. They found that blacks tend to have thinner central corneas.

GLAUCOMA
Corneas differ by race

As you know, glaucoma strikes about six times as many blacks as whites. What you may not know is that blacks tend to have thinner corneas than whites. This means that intraocular pressure (IOP) readings in blacks may be inaccurate, which could lead to improper diagnosis and treatment.

At the Houston Veterans Affairs Medical Center, study authors measured the corneas of 165 men -- 83 whites and 82 blacks. Researchers detected that blacks had significantly thinner central corneas than whites. The differences were present both in men with glaucoma and in men without glaucoma.

The study authors don't know why blacks are at a greater risk than whites, or why blacks are diagnosed earlier than whites. However, the authors do know that a thinner cornea may result in a delayed diagnosis.

Arch. Ophthalmol. 2001; 119: 23-27.

LASIK
Ablation predictions may be inaccurate

Speaking of corneas, investigators in Denver have discovered that predictions of actual corneal flap thickness and the amount of tissue ablated in LASIK patients often prove inaccurate.

In their study, investigators used subtraction pachymetry to determine actual corneal flap thickness and corneal tissue ablation in 60 LASIK patients (102 eyes).

Actual flap thickness was significantly less than predicted before surgery:

• in 15 eyes, predicted flap thickness was 160 microns, but the mean actual thickness was only 105 microns
• in 64 eyes, predicted thickness was 180 microns, but mean actual thickness was only 125 microns
• in 17 eyes, predicted thickness was 200 microns, but mean actual thickness was only 144 microns.

Also, investigators used linear regression to measure the amount of tissue actually ablated during LASIK. They found that surgeons ablated significantly more corneal tissue than predicted.

Ophthalmology 2000: 107: 2140-2143.