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HomemieyecareDry Eye in Diabetic Patients

Dry Eye in Diabetic Patients

Diabetes mellitus may induce various kinds of ocular complications, including diabetic retinopathy and cataract. However, dry eye induced by diabetes is very often overlooked.

There are reports showing significantly higher prevalence of dry eye in diabetic patients – from 15.4 per cent in Type 1 diabetic children to 54.3 per cent in Type 2 diabetic adults (see Table 1). Symptoms of dry eye include ocular discomfort, dryness, foreign body sensation, unstable vision, excessive tearing and sensitivity to light.

How Does Diabetes Affect the Tear System?

Diabetes can disrupt tear secretion. Clinical studies demonstrated a reduction of Schirmer test measurement in diabetic patients.3-7 Evidence from animal studies showed histological and functional alterations in the lachrymal gland as the result of direct hyperglycemia related oxidative stress.8

Moreover, damage to the corneal nerves observed in many diabetic patients may block the feedback mechanism that controls the tear system, further reducing tear secretion.9

Diabetic patients should be advised to maintain a high standard of personal hygiene because their eyes are vulnerable to infections

On the other hand, glucose in the skin, mucous membrane and tears may promote the growth of microorganisms in the conjunctiva and eyelid margins of diabetic patients.10-13 Bacteria like Staphylococcus sp. can be found on the conjunctiva and eyelid of more than 80 per cent of diabetic patients, 10,12 making diabetes a risk factor of conjunctivitis and blepharitis.14,15 Inflammation of the conjunctiva and eyelid may then lead to deficiency of mucin and lipid, further destabilizing the tear film (see Diagram 1).

Clinical Appearance

The effect of diabetes on the anterior segment of the eye should not be overlooked. Patients with diabetes have been shown to have lower tear break-up time,3,5 reduced tear production,3-7 a higher level of Rose Bengal staining 5,7 and fluorescein staining,5 a lower level of lactoferrin and tear-specific prealbumin,5 a higher grade of conjunctival metaplasia,4,6 lower goblet cell density4 and reduced corneal sensitivity.12 Moreover, sustained hyperglycemia can disrupt the corneal endothelial fluid pump,16 causing corneal edema.17 Therefore, any signs and symptoms of corneal swelling should also be closely monitored.

Management

Eye care practitioners have a role in managing patients with diabetic dry eye. Here are some guidelines:

1. Assess tear film function of all diabetic patients regularly. This should include Schirmer test, tear-breakup time, corneal staining, meibomian gland function and other tear film function tests.

2. Diabetic patients should be advised to maintain a high standard of personal hygiene because their eyes are vulnerable to infections. Patients should wash their hands frequently and avoid touching their eyes with their hands.

3. Diabetic patients should be advised to undertake a proper lid-cleaning regimen every day. This helps to remove any crusts, scales and bacteria appearing on lid margins:

a. Wet a clean washcloth with warm water and wring it out. Close eyes and place the washcloth over eyelids for 3-5 minutes. This helps loosen scales and crusts.

b. Wet a clean cotton-tipped swab with water. Gently hold upper lid up and rub the swab over the area where the eyelashes grow out of the eyelid.

c. Gently hold the lower lid down and scrub the lower eyelid.

4. Eye drops are always useful. Formulas containing lubricants like PEG-400 can help relieve dryness and irritations significantly. Since the ocular surface of diabetic patients is compromised, patients are advised to use preservative-free unit dose or multi-dose eye drops that contain disappearing preservatives. These preservatives are decomposed when exposed to light and are safe to the eyes.

Table1: Prevalence of dry eye in different diabetic populations

Region

N

Age

prevalence

USA

392

Dec-84

52.9%

Asia

199

27-82

54.3%

Europe

104

<18

15.4%

Diabetic Patients and Contact Lenses

It appears that diabetes is a contraindication for contact lens wear due to the alterations in the cornea and tear system. However, since silicone hydrogel lenses are available in the market, hypoxia due to low oxygen permeability can be virtually eliminated, making contact lens wear possible for diabetic patients. Herse suggested five factors to determine whether a diabetic patient is a good candidate for contact lens wear:18

1. Tight control of blood glucose levels

2. Stable refraction

3. No evidence of corneal epithelial erosion

4. Good compliance with an approved cleaning and disinfection regimen

5. Regular aftercare visits

Blood glucose level of diabetic patients in contact lens wear should be closely monitored.

The ultimate goal of contact lens fitting is to preserve the function of corneal epithelium and endothelium in diabetic patients. I would suggest silicone hydrogel contact lenses with higher oxygen transmissibility worn on a daily wear basis if contact lenses are to be prescribed. This ensures that the oxygen supply to the endothelium is not interrupted and hence the risk of corneal edema can be minimised. I would also advise patients to use a hydrogen peroxide cleaning and disinfection, because laboratory studies suggest some multipurpose solutions (MPS’s) can induce significantly higher cell apoptosis and have negative effect on epithelial cells viability.19

However, if patients are using a MPS, make sure that toxicity staining is being assessed in regular aftercare visits. Recent findings suggested that the risk of corneal inflammatory events is three times higher in patients showing toxicity staining.20 Also, strict compliance to contact lens cleaning instructions including rub and rinse should be assured.

Dr. Gunter Wong graduated from the optometry program at the Hong Kong Polytechnic University. He gained his Master of Optometry degree from the University of New South Wales and his PhD from the University of Hong Kong. His research interest is orthokeratology, visual perception and dyslexia. He is currently the training manager of Abbott Medical Optics Inc.

References
1. Hom M, de Land P. Self-reported dry eyes and diabetic history. Optometry 2006;77:554-558.
2. Manaviat MR, Rashidi M, Afkhami-Ardekani M, et al. Prevalence of dry eye syndrome and diabetic retinopathy in type 2 diabetic patients. BMC Ophthalmol 2008 Jun 2;8:10.
3. Akinci A, Cetinkaya E, Aycan Z. Dry eye syndrome in diabetic children. Eur J Ophthalmol 2007;17:873-878.
4. Yoon K-C, Im S-K, Seo M-S. Changes of tear film and ocular surface in diabetes mellitus. Korean J Ophthalmol 2004;18:168-174.
5. Yu L, Chen X, Qin G, et al. Tear film function in type 2 diabetic patients with retinopathy. Ophthalmologica 2008;222:284-291.
6. Goebbels M. Tear secretion and tear film function in insulin dependent diabetes. Br J Ophthalmol 2000;84:19-21.
7. Rahman A, Yahya K, Ahmed T, et al. Diagnostic value of tear films tests in type 2 diabetes. J Pak Med Assoc 2007;57:577-581.
8. Modulo CM, Jorge AG, Dias AC, et al. Influence of insulin treatment on the lacrimal gland and ocular surface of diabetic rats. Endocr 2009;36:161-168.
9. Alves MC, Carvalheira JB, Modulo CM, et al. Tear film and ocular surface changes in diabetes mellitus. Arq Bras Oftalmol 2008;71(6 Suppl):96-103.
10. Martins EN, Alvarenga LS, Hofling-Lima AL, et al. Aerobic bacterial conjunctival flora in diabetic patients. Cornea 2004;23:136-142.
11. Clifford CW, Fulk GW. Association of diabtes, lash loss, and Staphylococcus aureus with infestation of eyelids by Demodex folliculorum. J Med Entomol 1990;27:467-470.
12. Schultz RO, Peters MA, Sobocinski K, et al. Diabetic corneal neuropathy. Trans Am Ophthalmol Soc 1983;81:107-124.
13. Bilen H, Ates O, Astam N, et al. Conjunctival flora in patients with type 1 or type 2 diabetes mellitus. Adv Ther 2007;24:1028-1035.
14. Kruse A, Thomsen RW, Hundborg HH, et al. Diabetes and risk of acute infectious conjunctivitis – a population-based case-control study. Diabet Med 2006;23:393-397.
15. Ghasemi H, Gharebaghi R, Heidary F. Diabetes as a possible predisposer for blepharitis. Can J Ophthalmol 2008;43:485.
16. Herse PR. Corneal hydration control in normal and alloxan-induced diabetic rabbits. Invest Ophthalmol Vis Sci 1990;31:2205-2213.
17. Oriowo OM. Profile of central corneal thickness in diabetics with and without dry eye in a Saudi population. Optometry 2009;80:442-446.
18. Herse PR.Diabetes mellitus and the anterior eye: a review of signs and biochemistry. Clin Exp Optom 1991;74:39-48.
19. Chuang EY, Li D-Q, Bian F, et al. Effects of contact lens multipurpose solutions on human corneal epithelial survival and barrier function. Eye Contact Lens 2008; 34:281-286.
20. Carnt N, Jalbert I, Stretton S, et al. Solution toxicity in soft contact lens daily wear is associated with corneal inflammation. Optom Vis Sci 2007;84:309-315.

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