KERATOPLASTY

Keratoplasty, also called corneal grafting or corneal transplantation, is an operation in which the patient's diseased cornea is replaced by the donor's healthy

ADULT INCLUSION CONJUNCTIVITIS

Adult Inclusion conjunctivitis is a type of acute follicular conjunctivitis associated with mucopurulent discharge. It usually affects the
sexually active young adults.

Etiology
Inclusion conjunctivitis is caused by serotypes D to
K of Chlamydia trachomatis. The primary source of
infection is urethritis in males and cervicitis in

Types of contact lenses

Depending upon the nature of the material used in
their manufacturing, the contact lenses can be divided
into following three types:
1. Hard lenses,
2. Rigid gas permeable lenses, and
3. Soft lenses.

1. Hard lenses are manufactured from PMMA
(polymethylmethacrylate). The PMMA has a high
optical quality, stability and is light in

CONTACT LENSES

what is contact lens

Contact lens is an artificial device whose front surface
substitutes the anterior surface of the cornea.
Therefore, in addition to correction of refractive error,
the irregularities of the front surface of cornea can
also be corrected by the contact lenses.
Parts, curves, and nomenclature for contact lens
To understand the contact lens specifications
following standard nomenclature has been recommended
(Fig. 1).

Fig. 1. A contact lens.

1. Diameters of the lens are as follows :
i. Overall diameter (OD) of the lens is the linear measurement of the greatest distance across the physical boundaries of 

SPECTACLES

The lenses fitted in a frame constitute the spectacles. It is a common, cheap and easy method of prescribing corrective lenses in patients with refractive errors and presbyopia. Some important aspects of the spectacles
are as follows:

Lens materials
1. Crown glass of refractive index 1.5223 is very commonly used for spectacles. It is ground to the appropriate curvature and then polished to await the final cutting that will enable it to

SPASM OF ACCOMMODATION

(continue  ACCOMMODATION ANOMALIES)

Spasm of accommodation refers to exertion of abnormally excessive accommodation.

Causes
1. Drug induced spasm of accommodation is known to occur after use of strong miotics such as echothiophate and DFP.

2. Spontaneous spasm of accommodation is occasionally found in

Regular astigmatism treatment

Symptoms
Symptoms of regular astigmatism include: (i) defective vision; (ii) blurring of objects; (iii) depending upon the type and degree of astigmatism, objects may appear proportionately elongated; and (iv) asthenopic symptoms, which are marked especially in small amount of astigmatism, consist of a dull ache in the eyes, headache, early tiredness of eyes and
sometimes nausea and even drowsiness.

Signs
1. Different power in two meridia is revealed on 

Regular Astigmatism Refractive types

Depending upon the position of the two focal lines in relation to retina, the regular astigmatism is further
classified into three types:

1. Simple astigmatism, wherein the rays are focused on the retina in one meridian and either in front (simple myopic astigmatism – Fig. 1 a) or behind (simple hypermetropic astigmatism  Fig. 1 b "BELOW") the retina in the

What are lenses?

A lens is a transparent refracting medium, bounded by two surfaces which form a part of a sphere (spherical lens) or a cylinder (cylindrical or toric lens).
Cardinal data of a lens
1. Centre of curvature (C) of the spherical lens is the centre of the sphere of which the refracting lens surface is a part.
2. Radius of curvature of the spherical lens is the radius of the sphere of which the refracting
surface is a part.

Cardinal points of a convex lens: optical centre
(O); principal focus (F); centre of curvature (C); and principal
axis (AB).

3. The principal axis (AB) of the lens is the

OPTICS and Refraction

LIGHT
Light is the visible portion of the electromagnetic radiation spectrum. It lies between ultraviolet and infrared portions, from 400 nm at the violet end of the spectrum to 700 nm at the red end. The white light consists of seven colours denoted by VIBGYOR (violet, indigo, blue, green, yellow, orange and red). Light ray is the term used to describe the radius of
the concentric wave forms. A group of parallel rays of light is called a