Eye Didn't Know!

Inexpensive post-Lasik glasses

Did you know? A company called Spare Specs is selling inexpensive, pre-fabricated glasses designed to fine tune the vision after monovision Lasik or cataract surgery, or contact lens wear. Many patients older than 40 years old elect to have monovision correction. This means that their contact lenses or surgery gives them one eye which is focused for distance and one eye focused at near. This enables spectacle-free vision for most daily activities. For those who desire even crisper vision for, say, driving, these glasses will correct the near-sighted eye for distance, giving crisper binocular vision. Similar prescriptions are available to correct the distance eye for reading.

I have not personally prescribed these lenses yet, but they seem like a promising, low-cost solution to improve the vision for monovision patients.

Did you also know? The same company claims that their pair of weak distance glasses will reduce halos and glare from the new multifocal lens implants. I am eager to see any publications confirming this!

More orthokeratology news

I recently posted on the topic of orthokeratology, the practice of prescribing rigid contact lenses to be worn overnight in order to not need corrective lenses in the daytime. I have never quite understood the rationale for this treatment, as one wears contacts at night, with an increased risk of corneal ulcers, and the correction wears off if you stop.

A new study from Japan, of 23 patients, shows that the lenses do correct refractive errors, but may, however, decrease the quality of vision. Higher order aberrations, which are visual imperfections not correctable with standard eyeglasses, increased considerably after orthokeratology usage. Also, contrast sensitivity, which is important for quality night vision, suffered. This corresponded to patient symptoms of poor visual quality despite seeing well on the eyechart.

It is worth noting that refractive surgery (e.g. Lasik) did not correct for higher order aberrations until a few years ago. The quality of vision, especially at night, has improved with this newer laser technology.

Orthokeratology: new and improved?

Did you know? Orthokeratology, or changing the refraction of the eye by overnight use of rigid contact lenses, is making a resurgence under the name of Corneal Refractive Therapy, or CRT.

Recently a friend of mine asked me about its efficacy in children. He was concerned that his daughter’s mild myopia would continue to progress. Since orthokeratology is not used by the vast majority of ophthalmologists, I could not immediately answer his question.

It so happens that the lead article and editorial in the May 2007 issue of Archives of Ophthalmology were about the dangers of orthokeratology! A study from Taiwan, (where myopia is extremely common and the interest in orthokeratology has grown), reported the risk factors for microbial keratitis, or corneal ulcers, which are serious and potentially sight-threatening infections of the cornea, the clear front surface of the eye. A major risk factor was orthokeratology. The authors stated that this risk was:

“...worthy of special attention given the increased popularity of overnight orthokeratology. Eye care practitioners who perform overnight orthokeratology have an obligation to warn their patients of this potential vision-threatening complication...”

The journal’s editors stated:

"The rationale for the ongoing use of overnight orthokeratology in the pediatric and adolescent population is therefore brought into question. Although these techniques can rapidly and effectively reduce myopia, albeit with limited range, accuracy, and precision... complete or near complete regression of effect is the rule, and this technique has not been demonstrated to have any infulence on mypopia progression due to [lengthening of the eye]."

In other words, orthokeratology temporarily reduces myopia, with limited precision, presents a risk of serious infection, and does nothing to reduce progression of near-sightedness.

Parents considering orthokeratology for their children should heed the messages in this article.

Furthermore, it should be pointed out that if you use orthokeratology, every time you stop wearing your overnight lenses, your refraction will be shifting, so that backup glasses will not be useful!

Did you also know? Parents should realize that by the time their children are adults, the science of refractive surgery will be even further refined, safe, predictable, and permanent, which cannot be said of orthokeratology, despite its appeal of being non-surgical.

Safer Lasik

Did you know? There are laser alternatives to LASIK. In Lasik, a flap is created in the cornea, either with a blade or with another type of laser, before the actual reshaping of the cornea takes place. The original laser procedure, called PRK, did not have this flap. In the past 18 months, there has been a dramatic shift in the number of doctors returning to the surface to perform the laser. These procedures go by many names: PRK, Advanced Surface Ablation, epi-lasik, Flapless Lasik, or LASEK. Why are doctors returning to the surface? Two reasons: safety, and visual results. Most complications of LASIK involve the flap. Without the flap, there are no flap complications. Also, without the small visual aberrations caused by the flap, the visual results may be slightly better. Read more here:

This chart shows the surge in interest in surface laser in the last 18 months:

Did you also know? In my practice, safety comes first. I have only performed surface laser ablation, and continue to do so.

Aloe Vera

Did you know? Aloe vera contains an ingredient which may someday prove useful to inhibit scarring in the cornea. Mannose-6-phosphate is a sugar derived from aloe vera. It has been recently shown to inhibit cultured corneal cells from transforming into scar-like tissue. This may reduce haze formation sometimes seen after injury or after refractive surgery. Read more here.

Did you also know? The haze which sometimes occurs after PRK (photorefractive keratectomy) surgery is very rare today with better lasers providing a smoother surface after surgery.