MKSAP Quiz: Photocoagulation therapy
This month's quiz asks readers to evaluate a 62-year-old man before he has panretinal laser photocoagulation therapy in both eyes.
A 62-year-old man is evaluated before having panretinal laser photocoagulation therapy in both eyes. He has an 18-year history of type 2 diabetes mellitus. He also has diabetic neuropathy and hypertension. At his annual retinal eye examination last week, his vision had deteriorated to 20/30 in his right eye and 20/40 in his left eye; new blood vessels are seen growing on the optic discs of both eyes. Medications are metformin, insulin glargine, simvastatin, ramipril, enteric-coated aspirin, and hydrochlorothiazide.
On physical examination, temperature is 36.9 °C (98.4 °F), blood pressure is 147/86 mm Hg, pulse rate is 88/min, and respiration rate is 14/min; BMI is 34. Other than the presence of proliferative diabetic retinopathy, physical examination findings are unremarkable.
Which of the following is the most likely outcome of the planned procedure?
A. Diminished central vision with retention of peripheral vision
B. Diminished peripheral and night vision with retention of central vision
C. Improvement of vision (to 20/20) in both eyes
D. Loss of binocular vision and depth perception
MKSAP Answer and Critique
The correct answer is B. Diminished peripheral and night vision with retention of central vision. This item is available to MKSAP 16 subscribers as item 1 in the Endocrinology section. Part A of MKSAP 16 was released on July 31, 2012 and Part B on Feb. 1, 2013. More information is available online.
This patient will most likely have diminished peripheral and night vision but retained central vision after photocoagulation. Panretinal laser photocoagulation delivers several thousand small burns to the periphery of the retina, which results in the avascular scarring and shriveling of new vessels shown.
As a result, more retinal blood flow is available for the central part of the retina, which helps retain central vision. However, this procedure also causes deterioration of peripheral vision, which often is most noticeable at night.
This patient's overall visual acuity is unlikely to improve but should not get significantly worse, unless the proliferative retinopathy progresses.
Because central vision remains intact, neither binocular vision nor depth perception will be affected.
Key Point
- Panretinal laser photocoagulation therapy for diabetic retinopathy typically results in retained central vision but poorer peripheral and night vision.