Glucose detection in 
Urinalysis from Avicenna's Al-Qanun shows a physician examining a sample of urine in a transparent vase. Avicenna noted the sweet taste of urine in patient with recurrent infection, wasting of body and foot gangrene.
50th Anniversary of the Discovery of 
Insulin. Benedict's test & a molecule 
of proinsulin. 
The white circle represents the C pep- 
tide which is connected to a molecule 
of insulin in black. The insulin has two chains of amino acids bound together 
by two disulfide bonds. The Benedict's solution was invented by the US 
physician Stanley Rossiter Benedict 
in 1907. It allows estimation of 
glucose in the urine. The solution is 
added to the patient's urine and 
heated then cooled. The colour of the 
resulting solution is compared to a 
colour chart for the amount of 
glucose presents.
National Diabetes Day. A humming 
bird in flight with a multi-colour long 
tail which is actually a strip used to 
test for glucose in urine.

Lions Club 25th Anniversary in 
St. Vincent. Blood glucose monitoring 
using a meter. Blood glucose meter 
is a big step forward in the self-
monitoring of blood glucose control 
providing a more accurate and 
immediate feedback than the urine 
test. The prototype was invented by Anton H. Clemens in the 1970s.
Section 10 Cataract
10.1 Surgery for cataract in diabetes
Cataract is a common complication of diabetes indeed it has been estimated 
that up to fifteen per cent of cataract surgery is performed on diabetics57
The main indications for surgery are the same as for non-diabetic patients. 
In addition, surgery is indicated if the lens opacity prevents an adequate 
examination of the fundus or produces excessive scatter of light during laser 
therapy. Standard surgical techniques are applicable eg. extracapsular 
cataract extraction or phacoemulsification. with posterior chamber intraocular 
flexible or non-flexible lens implantation. If phacoemulsification is performed, 
it is advisable to perform a large capsulorrhexis with a 7mm optic lens, thus 
allowing the better visualization of the fundus for PRP if required. Following 
surgery, the incidence of capsular opacification is greater in diabetics than in 
non-diabetics. Therefore, a large YAG capsulotomy to improve vision or 
improve visualization of the retina may become necessary. The results of 
surgery  best in those eyes with no retinopathy and worst in those eyes with 
active proliferative retinopathy58.

10.2 Complications of surgery

All forms of DR may become more severe following cataract surgery. In addition, 
surgery may be followed by a stormy post-operative course, particularly in those 
with active retinal disease. Complications include:
  • severe uveitis with or without a ‘fibrin response’ in the anterior chamber..

  • .
  • the development or progression of rubeosis iridis. In patients with 

  • existing rubeosis, this should be treated pre-operatively with panretinal 
    photocoagulation. If this is not possible, laser therapy should be 
    performed peroperatively or in the immediate postoperative period.
  • vitreous haemorrhage in patients with active new vessels. If preoperative 

  • laser is inadequate or impossible due to poor visualization through the lens
    opacity, peroperative laser therapy should be considered as for rubeosis.
    If peroperative laser is not possible, then evaluation of the retina and 
    adequate laser treatment should be performed in the immediate 
    postoperative period.
  • the development or worsening of active maculopathy. Evaluation and 

  • treatment of the maculopathy should be carried out at an early stage in 
    the postoperative period. Patients with diabetes are at slightly greater 
    risk of cystoid macular oedema which may be difficult to differentiate 
    from true diabetic maculopathy. In cystoid macular oedema there is 
    normally leakage of dye from the disc on fluorescein angiography which 
    helps to differentiate the two conditions.
Cataract in  patients with severe PDR or who require vitrectomy presents 
special therapeutic problems. The use of red or infra-red wavelengths allows
laser photocoagulation to be delivered through many nuclear sclerotic cataracts. 
Use of the laser indirect ophthalmoscope allows panretinal laser photocoagulation 
to be delivered at the time of cataract surgery (see above for indications for 
preoperative laser therapy). Post-operative laser photocoagulation can readily 
be delivered either using the hand held 90D or 78D lens at the slit-lamp or with 
contact lens after small incision (phacoemulsification) cataract extraction 
techniques. It is worth re-iterating that patients with significant ischaemic 
retinopathy or proliferative retinopathy may frequently require additional 
panretinal laser photocoagulation preoperatively or in the immediate post-
operative period to prevent rapidly progressive neovascular glaucoma and 
10.3 Lensectomy and vitrectomy
Patient with cataract and severe proliferative retinopathy (vitreous haemorrhage, 
widespread proliferative retinopathy, traction retinal detachment) requiring 
vitrectomy may undergo combined lens-vitreous surgery59. Cataract extraction 
with intra-ocular lens implant is performed (either manual expression extracapsular 
surgery or phacoemulsification cataract surgery), followed by a 3 port pars plana 
vitrectomy with delivery of full panretinal laser photocoagulation using the endolaser. 
Membrane dissection may be performed if needed60. In general, phacoemulsification 
is the preferred procedure in lensectomy/vitrectomy when they are performed as 
sequential procedures. 
Alternatively combined pars plan vitrectomy and lensectomy, with preservation of 
the anterior capsule, may be performed with pars plana delivery of endolaser. 
Insertion of a posterior chamber sulcus-fixated intra-ocular lens anterior to the 
anterior lens capsular, either a central anterior capsulotomy may be performed at 
the same surgical session or at a later date.
Epidemiology Clinical features Risk factors Screening
Lasers and lenses. NVD,, NVE.. Maculopathy
Vitrectomy. Cataract Special problems Counselling
References.. AAO guidelines Atlas of Retinopathy Contact lenses
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