the eye blog
EYE CARE INFO & UPDATES
Naturally, when people have blurry vision they think they might need glasses. And yes, in many cases, glasses may be all they need to fix their blurred vision after having a thorough eye examination at an optometrist.
Sometimes, however, glasses cannot fix a person's blurred vision, at least not entirely. Most of the time this may be due to age-related eye changes such as cataracts, glaucoma and macular degeneration, but occasionally it can also happen to younger people.
Recently I had in my practice a young patient who came in for a second opinion about his eyes. He had seen an optometrist in a shopping centre a little while back and was prescribed glasses for the first time there. He was concerned that his vision was still blurry even with his glasses on.
After taking a detailed history I proceeded to test his eyes, and soon it became apparent to me what his eye issues were and why he was still having problems with his vision. He had a condition called keratoconus ('cone-shaped cornea') — a progressive eye condition that causes the front surface of the eye, the cornea, to become thin and distorted. Unlike normal astigmatism (unequal eye surface curvature across two meridians, like an egg shape), which is very common, in keratoconus the eye surface is vastly uneven and irregular. That means light entering the eye is scattered in many different directions, and not focused at a point or in one plane.
This eye surface irregularity means the lenses in the glasses he was prescribed with cannot fully correct his vision deficit and blur, as glasses can only bend (or refract) light in up to two meridians. Unfortunately he wasn't explained this by his previous optometrist. It's possible the other practice didn't have the instrument to properly diagnose his condition.
We use an instrument called a corneal topographer to accurately measure the shape of the eye surface when we suspect a case of keratoconus or other conditions that cause distortions in the cornea. With the data captured we can instantly produce a 3D topographical map of the cornea, as illustrated below, to show the contours of the eye surface and any irregularities present. This instrument is also used for advanced contact lens fitting, Ortho-K and dry eye analysis.
What can be seen in the images below (of the right and left eyes) are areas of surface distortion, with a steep area (in red) resembling a cone shape. This is a classic case of keratoconus. With this condition, the best way for him to see clearer (than what is possible with glasses) is to wear special rigid contact lenses, to effectively provide his eyes with a new, smooth optical surface. These specially made contact lenses are individually designed for each eye using the 3D topography maps, to ensure of ideal fitting lenses on the distorted eye surfaces.
EYECARE CONCEPTS — ADVANCED EYE CARE & CONTACT LENS PRACTITIONER — MELBOURNE
Philip Cheng - B.Optom (Melb) Ocular Therapeutics (GCOT). Optometrist at Eyecare Concepts Kew East, Melbourne. An experienced eye care & contact lens practitioner with expertise in myopia control & orthokeratology.