Keratoconus - Keratoconus

Japanese: 円錐角膜 - えんすいかくまく（英語表記）Keratoconus

What is the disease?

The cornea is dome-shaped, but with this disease it protrudes into a cone shape and becomes thinner in the center.

Most cases begin in the teens and progress gradually thereafter, but usually do not progress significantly after the age of 30. Although there is a difference between the left and right eyes, it is basically bilateral.

What is the cause?

The cause has not yet been fully elucidated, but since there are many familial cases, it is certain that genetic factors play a role.

In addition, it is often accompanied by atopic dermatitis, and it is said that the external force of rubbing the eyes is a factor that worsens the condition.It is thought that the condition develops when a genetic predisposition to corneal bulging is combined with environmental factors.

How symptoms manifest

In the early stages, there is a decrease in vision at distances, but vision is sufficient with glasses, so there is not much difference between this and people with normal myopia or astigmatism. However, as the bulging progresses, glasses are no longer sufficient and vision can only be maintained with hard contact lenses. correction ( Resilience ) If the cornea continues to protrude, it will no longer be possible to wear contact lenses and vision will be severely impaired.

Also, during this process, suddenly, at the very back of the cornea, crack ( Crack ) This causes a large amount of Intraocular fluids ( Cancer Station ) ( Aqueous humor ( Guard ) ) may flow into the cornea, causing it to swell significantly ( Acute edema ( Freshwater fish ) At this point, the center of the cornea becomes cloudy and visible to the naked eye, and vision deteriorates further.

Testing and diagnosis

What has progressed Slit lamp ( Final stage ) A microscopic examination can diagnose the condition, but mild cases require examination with special equipment called a photokeratoscope or videokeratoscope, which analyzes the shape of the corneal surface. A pachymeter, which measures the thickness of the cornea, can also be used to help diagnose the condition.

Treatment methods

In mild to moderate cases, wearing hard contact lenses can provide a certain degree of vision, and wearing hard contact lenses also has the effect of slightly slowing the progression of keratoconus.

When acute edema occurs, contact lenses are not worn and the patient is monitored. Although there is severe swelling and cloudiness, the condition usually improves within 1-2 months. Therefore, even if vision is severely impaired, there is no need to undergo a corneal transplant at this time. In many cases, the patient will be able to wear contact lenses again after the condition improves.

If you have trouble continuing to wear contact lenses, such as them falling out or having a strong foreign body sensation, you may need to undergo a corneal transplant. Keratoconus is one of the corneal diseases that has the best prognosis after corneal transplantation.

What to do if you notice an illness

Recently, people with mild keratoconus have been undergoing surgery to correct myopia and other conditions. Refractive correction ( Customization ) There have been cases where people have had to undergo surgery (such as LASIK surgery, which uses a laser to modify the cornea), which has become a problem.

Current refractive surgery is performed by scraping the cornea, so for those with keratoconus, whose cornea is already thin and protruding, undergoing this surgery will only make the condition worse. Contraindications ( Kinki ) It is said that...

However, early keratoconus and strong astigmatism ( Ranshi ) It is difficult to distinguish between the two, so if keratoconus is suspected, then, as far as current refractive surgery methods are concerned, surgery should be refrained from.

Koji Inoue

Source: Houken “Sixth Edition Family Medicine Encyclopedia” Information about the Sixth Edition Family Medicine Encyclopedia

Japanese:

どんな病気か

　角膜はドーム状をしていますが、これが円錐状に突出してきて、中央が薄くなる病気です。

　多くは10代で発症し、以後少しずつ進行していきますが、30代以降は通常あまり大きく進行しません。左右差はありますが、基本的に両眼性です。

原因は何か

　原因はまだ十分に解明されていませんが、家族性の場合が少なからずあることから、遺伝的な因子が関与していることは確かです。

　また、アトピー性皮膚炎を合併していることも多く、眼をこするという外力が悪化の要因となっているといわれており、角膜が突出しやすい遺伝的素因に環境要因がプラスされて発症すると考えられています。

症状の現れ方

　初期は遠方の視力低下があるものの、眼鏡で十分に視力が出るので、普通の近視や乱視の人とあまり変わりません。ところが突出が進行してくると、眼鏡では無理で、ハードコンタクトレンズでないと視力矯正(きょうせい)ができなくなってきます。その後、さらに突出してくるとコンタクトレンズも装用できなくなり、強い視力低下を起こします。

　また、その経過中で突然、角膜のいちばん奥に亀裂(きれつ)が生じ、そこから角膜内に大量の眼内液(がんないえき)（房水(ぼうすい)）が流入して、角膜が著しくはれることがあります（急性水腫(きゅうせいすいしゅ)）。この時は、肉眼でも角膜の中央が白くにごっているのがわかるようになり、視力はさらに低下します。