A detailed molecular map for eye disease

Understanding eye diseases is tricky enough. Knowing what causes them at the molecular level is even more confounding.

To understand eye diseases better, University of Iowa (UI) researchers have created the most detailed map to date of a region of the human eye long associated with blinding diseases, such as age-related macular degeneration. The high-resolution molecular map catalogs thousands of proteins in the choroid, which supplies blood and oxygen to the outer retina, itself critical in vision. By seeing differences in the abundance of proteins in different areas of the choroid, the researchers can begin to figure out which proteins may be the critical actors in vision loss and eye disease.

Technology to detect early diabetic retinopathy

Yissum Research Development Company, the technology transfer arm of the Hebrew University of Jerusalem, has introduced a method for detecting retinal micro-aneurysms that potentially pose a high risk for leakage of blood and blood products, which can lead to visual impairment in diabetic retinopathy (amongst other retinal vascular diseases). This method is likely to enable early diagnosis and treatment of the condition, potentially minimizing damage and saving vision. 

The technology has been patented by Yissum and is currently searching for an appropriate partner for the further development and commercialization of the invention. 

Dr. Yaakov Nahmias and his team from the Center for Bioengineering at the Hebrew University of Jerusalem developed a computational method to identify microvascular regions with high risk of leakage based on fluid dynamics. The method will enable ophthalmologists to identify microaneurysms with a high risk of leakage using adaptive optics. The scientists found that high risk is correlated with increased level of a protein called Von Willebrand factor (vWF), which has been associated with early development of diabetic retinopathy.

Retinal microaneurysms are dilations of small blood vessels in the retina, and an early feature of diabetic retinopathy, one of the leading causes of blindness worldwide. Retinal microaneurysms reduce vision because they eventually cause fluid leakage from blood vessels and retinal edema. Localized leakage can be detected and treated using laser ablation slowing the progression of diabetic blindness.

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Does space flight impact astronauts' eyes and vision?

A new study sponsored by NASA finds that space flights lasting six months or more can cause a spectrum of changes in astronauts' visual systems. Some problems, including blurry vision, appear to persist long after astronauts' return to Earth. The results are affecting plans for long-duration manned space voyages, such as a trip to Mars.

The study team included ophthalmologists Thomas H. Mader, MD, of Alaska Native Medical Center and Andrew G. Lee, MD, of The Methodist Hospital, Houston, Texas. Their report is published in October's Ophthalmology, the journal of the American Academy of Ophthalmology.

The researchers studied seven astronauts, all of whom were about age 50 and had spent at least six continuous months in space. All reported that their vision became blurry, to varying degrees, while on the space station. Vision changes usually began around six weeks into the mission and persisted in some astronauts for months after their return to Earth. Drs. Mader and Lee agree that the eye abnormalities appear to be unrelated to launch or re-entry, since they occurred only in astronauts who spent extended time in microgravity.

In-depth examination of the seven astronauts revealed several abnormalities. All of the subjects had one or more of the following changes in the tissues, fluids, nerves and other structures in the back of the eye:

• Flattening of the back of the eyeball (five subjects);
• Folds in the choroid, the vascular tissue behind the retina, which is the light sensitive area in the back of the eye (five subjects); and
• Excess fluid around and presumed swelling of the optic nerve (five subjects).

Such abnormalities could potentially be caused by increased intracranial pressure−that is, pressure inside the head. However, none of these astronauts experienced symptoms usually associated with intracranial pressure, such as chronic headache, double vision, or ringing in the ears. Researchers believe other factors may be involved, such as abnormal flow of spinal fluid around the optic nerve, changes in blood flow in the choroid, or changes related to chronic low pressure within the eye, which is known as intraocular pressure. They hypothesize that these changes may result from the fluid shifts toward the head that occur when astronauts spend extended time in microgravity.

The visual system changes discovered by the researchers may represent a set of adaptations to microgravity. The degree and type of response appear to vary among astronauts. Researchers hope to discover whether some astronauts are less affected by microgravity and therefore better-suited for extended space flight, such as a three-year round trip to Mars.

In their report, Drs. Mader and Lee also noted a recent NASA survey of 300 astronauts that found that correctible problems with both near and distance vision were reported by about 23 percent of astronauts on brief missions and by 48 percent of those on extended missions. The survey confirmed that for some astronauts, these vision changes continue for months or years after return to Earth. The possibility of near vision problems has been recognized for decades, and special "space anticipation glasses" to improve visual sharpness have been provided on all spacecraft dating back to John Glenn, who had a pair in his space capsule.

"In astronauts over age 40, like non-astronauts of the same age, the eye's lens may have lost some of its ability to change focus," said Dr. Mader. "In the space program's early days most astronauts were younger, military test-pilots who had excellent vision. Today's astronauts tend to be in their 40s or older. This may be one reason we've seen an uptick in vision problems. Also, we suspect many of the younger astronauts were more likely to 'tough out' any problems they experienced, rather than reporting them."

As part of ongoing research all astronauts now receive comprehensive eye exams and vision testing. Diagnostic tests include pre- and post-flight magnetic resonance imaging, optical coherence tomography, which magnifies cross-section views of parts of the eye, and fundus photography, which records images of the retina and back of the eye. Intraocular pressure measurement and ultrasound imaging take place in flight, as well as pre- and post-mission.

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Lasers may be increasing threat to the eye and the retina

An article in the New York Times by Christine Negroni refers to the increasing threat to vision and damage to the retina, by increasing access to the green laser.

Eye doctors around the world are warning of increasing number of cases of teenagers who suffer permanent eye damage while playing with high-powered green laser pointers.

The pointers, which have also been implicated in a ninefold increase over five years in reports of lasers’ being aimed at airplanes, are easier than ever to order online, even though they are 10 to 20 times as powerful as the legal limit set by the Food and Drug Administration.

A recent case highlights the problem: A high school student complained of a blind spot in his left eye, when a friend waved a green laser pointer in front of his face. The damage, as diagnosed by a retina specialist, was found to be severe and is not likely to completely heal, which means the high school student may end up with a permanent damage to his vision. The same retina specialist found out that the laser put out 50 milliwatts of power, 10 times more than the F.D.A. limit. And as he investigated his patient’s case, the doctor went online and bought a 100-milliwatt pointer for $28 (about Rs 1255) , and was hardly able to believe that he could buy an even more stronger laser without any controls or checks in place.

Like household lights, lasers are measured in watts, but the similarity ends there. A 100-watt incandescent bulb produces about five watts of visible light; the five-milliwatt laser is only one-thousandth as powerful. But because the light from a bulb is diffuse while a laser beam is concentrated, the effect of five milliwatts on the eye is 10,000 times as intense, according to laser experts. (For technical information on lasers, click here.) It also does not help that the eye tends to focus and intensify the laser, causing even more damage to the main part of the retina, the macula or the fovea, which is the center of the retina. The darker pigment present in the region absorbs the light as heat, quickly raising the temperature of the retina.

Some experts feel that the sale of laser pointers more than one milliwatt should be banned to the general public, since the stronger laser put people at risk of permanent visual impairment by the criminally minded or those who are unaware of the risks.

F.D.A., in its update, warned that a higher-powered laser gives less time to look away before injury can occur, and as power increases, eye damage may happen in a microsecond. One company that has come under scrutiny from the FDA is Wicked Lasers from Hong Kong.

Several laser experts feel that the enforcement of regulations is insufficient and ineffective. But any new restrictions being put in to contain the availability of such lasers will certainly meet resistance from the large community of laser enthusiasts, including those who use them professionally (like contractors and astronomers) and hobbyists.

Earlier, red lasers were used as laser pointers, Now, green lasers are more commonly used. But green lasers are also more dangerous. Green is more easily absorbed by the retina than red, so it requires less exposure to cause damage.

As a recommendation, please do not allow lasers to fall into the hands of unsuspecting children, who may find it easy to point the laser light at others, which can potentially be permanently damaging. Also, educate everyone who uses laser pointers to be more careful, including colleagues at work, who have the tendency of using the laser pointer during presentations, and who have the tendency of sweeping their hands around with the laser pointer turned on!