If you want to know about hypermetropia and its type, you are in the right place. If you are a student of science stream and currently studying in 12th standard, then you have already come across this topic, right? Well, if not, then you will definitely get it in the chapter of optics. So today I’m going to share a few important details about hypermetropia which may be beyond your syllabus but important for you to know. Also, if you want to pursue Optometry in future for your higher studies then you may find this interesting too. So let’s get started.
The term hypermetropia was basically suggested by Kastner in 1755. The meaning of this term is derived from words hyper meaning excess, met meaning measure, and opia meaning eye, which togetherly stands as an excess measure of an eye.
Hypermetropia has also termed as long-sightedness as it is optically defined as the state of condition in which the parallel rays of light which are coming from infinity are basically focused behind the retina with a condition of the accommodation being at rest. As a result, the posterior focal point falls behind the retina, thereby receiving a blurry image.
Types are classified according to two categories, one being the etiological category and the other being clinical category.
This category depends on the mechanism of production and has six more subtypes –
i) Axial Hypermetropia – This is one of the most common forms in which the overall refractive power of our eyeball is normal but there are changes in axial length of the eyeball (shortening). About 1mm of shortening causes around 3 dioptre hypermetropia.
ii) Curvatural Hypermetropia – In this type, we actually see the curvature related refractive error due to change in curvature of certain parts of an eye like cornea, lens or both. Here, about 1mm of radial increase of curvature causes in around 6D of hypermetropia.
iii) Index Hypermetropia – Does the name sound relatable? Yes right? If not, let me tell you that you have already read about refractive index right? Well, this category of Hypermetropia occurs due to change in the refractive index of the lens with increasing age.
iv) Positional Hypermetropia – Though the name says it all but it may be a bit difficult for you to understand, so let me clear it out to you. Basically in this category, the lens is posteriorly subluxated and that may occur due to congenital or acquired trauma.
v) Aphakia – This is a new term for you all and was even a new term for me when I just pursued a bachelor of optometry after passing out from my school life. Well, the condition where our natural crystalline lens is absent is termed as Aphakia. It may be either congenital or acquired during surgery, which was specifically seen during cataract surgery of old times.
So basically this section is again subdivided into the following –
a. Over corrected myopia
b. Under corrected ocular lens during cataract surgery
So these were the etiological category having these types of Hypermetropia. But there’s another category which is named as clinical category. Basically the clinical types fall under this category. But I won’t share the details because that would become very high for a student of class 12 to understand as it includes certain mechanisms. But I would like to share that they are of 3 types mainly named as, Simple, Pathological and Functional Hypermetropia. Though there are a lot of subtypes in them too. So if you ever pursue Optometry, you will get to know about them. It’s not necessary that you have to pursue Optometry to know about the rest of the types, if you are interested enough, you can even Google them up in your free time. You can even check YouTube videos to learn more appropriately.
Now, before coming to an end to this article, I would like to share a very interesting fact about Hypermetropia which you probably may not know. So if you are reading this article still now then you can basically get to know about this. At birth, our eyeballs are short and grow to proper size along with increasing age up to 5 to 7 years. So during birth, every individual has around 2 to 3 dioptre plus Hypermetropia which gradually tends reduce with age and our eye becomes emmetropic (this condition is basically when people have a normal eye, with no refractive errors). Interesting isn’t it? Let’s know one more interesting fact. After we attain 50 years we again start going back to the 2 to 3 dioptre plus Hypermetropia due to changes in the accommodation power of our natural crystalline lens.
So I hope that I could make this article a bit interesting and it wasn’t as boring as you read in books. But if you found it boring then I’m extremely sorry for that. So if you have plus power then you may know the specific reason why you have such power right? And also, thank you for reading this article till the end.