CONTACT LENSES

Ans. is ‘b’ i.e., Rifampicin

Rifampicin cuases permamnent staining of contact lens; hence use of contact lens should be discontinued.

C i.e. Pseudomonas infection

Soft Contact Lens Complications

A i.e. Acanthamoeba

Pseudomonas aeruginosa is the most common organism encountered in contact lens related acute keratitis & corneal ulcer.

Acanthamoeba is the 2nd most common cause.

Ans. Hard

Ans. Irregular astigmatism

Ans. B: 8%

1-2% image magnification is seen with the use of intraocular lenses for refractive correction of aphakia

• 8% image magnification is seen with the use of contact lenses for refractive correction of aphakia
• 20-30% image magnification is seen with the use of spectacles for refractive correction of aphakia

Ans. is ‘b’ i.e., HEMA

Types of contact lenses

Depending upon the nature of the material used in their manufacturing, the contact lenses can be divided into three types : –

i) Hard lenses : – Made of polymethylmethacrylate (PMMA).

ii) Rigid gas permeable (RGP) lenses : – Copolymer of PMMA, silicon containing vinyl monomer and cellulose acetate butyrate (CAB) are used to manufacture RGP lenses.

iii) Soft lenses : – These are made up of hydroxymethymethacrylate (HEMA).

Ans. is ‘d’ i.e., All of the above

Complications of contact lens wearing are : ‑

• Intolerance: – Some people find wearing contact lenses intolerable.
• Corneal complications: – Corneal abrasion, Corneal edema, Corneal vascularization, Microbial keratitis (Pseudomonas, acanthamoeba), Sterile corneal infiltrate.
• Giant papillary conjunctivitis.
• Hypoxia: – Cornea is deprived of oxygen from the tear film by the presence of the contact lens. The cornea becomes edematous and new vessels may develop in the timbal area.
• Sensitivity: – This may develop in response to the preservative (thiomersal) in the cleaning and soaking solution. This results in allergic conjunctivitis.

Ans. is ‘b’ i.e., Pseudomonas 

Complications of contact lens wear

• Complications of contact lens wearing are : ‑
• Intolerance :- Some people find wearing contact lenses intolerable.
• Corneal complications :- Corneal abrasion, Corneal edema, Corneal vascularization, Microbial keratitis (Pseudomonas, acanthamoeba), Sterile corneal infiltrate.
• Giant papillary conjunctivitis
• Hypoxia :- Cornea is deprived of oxygen from the tear film by the presence of the contact lens. The cornea becomes edematous and new vessels may develop in the limbal area.
• Sensitivity :- This may develop in response to the preservative (thiomersal) in the cleaning and soaking solution. This results in allergic conjunctivitis.

Ans. is’ i.e., Improved corneal oxygen supply

Advantages of contact lens

• Contact lens has several advantages over spectacles:-

1. Retain binocularity in Anisometropia owing to less magnification of size of the retinal image.
2. Irregular astigmatism can be corrected.
3. No peripheral distortion as it moves with eye and there is a normal field of vision.
4. Not subjected to moistening.
5. Several varieties of contact lens can aid in the treatment of the dry eye. A hard contact lens may stimulate reflex tearing and also prevent evaporation of tear.
6. Cosmetically superior.
7. Tinted contact lenses relieve photophobia in albinism.

Disadvantages of contact lens

• Complications of contact lens wearing are : ‑

1. Intolerance: – Some people find wearing contact lenses intolerable.
2. Corneal complications: – Corneal abrasion, Corneal edema, Corneal vascularization, Microbial keratitis (Pseudomonas, acanthamoeba), Sterile corneal infiltrate.
3. Giant papillary conjunctivitis.
4. Hypoxia: – Cornea is deprived of oxygen from the tear film by the presence of the contact lens. The cornea becomes edematous and new vessels may develop in the limbal area.
5. Sensitivity: – This may develop in response to the preservative (thiomersal) in the cleaning and soaking solution. This results in allergic conjunctivitis.

1. Hard lenses:

• Made of pokymethylmethacrylate (PMMA)

2. Rigid gas permeable (RGP) lenses:

• Copolymer of PMMA, silicon containing vinyl monomer & cellulose acetate butyrate (CAB) are used to manufacture RGP lenses.

3. Soft lenses: 

• These are made up of hydroxymethymethacrylate (HEMA)