This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cornea and sclera, Subject name: Ophthalmology
The central nebular corneal opacity is easily treated with -. 
Select and explain. 
A. Phototherapeutic keratectomy, B. Penetrating keratoplasty, C. Gas permeable contact lens, D. Soft contact lens
A: Phototherapeutic keratectomy
Answer: A: Phototherapeutic keratectomy 
Explanation: Nebular corneal opacity. It is a faint opacitywhich results due to superficial scars involvingBowman's layer and superficial stroma . A thin, diffuse nebula covering thepupillary area interferes more with vision than thelocalised leucoma away from pupillary area.Fuher, the nebula produces more discomfo topatient due to blurred image owing to irregularastigmatism than the leucoma which completelycuts off the light rays. Phototherapeutic keratectomy (PTK) performedwith excimer laser is useful in superficial (nebular)corneal opacities. REF:Comprehensive ophthalmology,AK Khurana,4th edition,pg no.122.