Correlation of Corneal Sensation, but not of Basal or Reflex Tear Secretion, With the Stage of Diabetic Retinopathy

Abstract

Both corneal sensation and total or reflex tear secretion are reduced in individuals with diabetes. The decrease in corneal sensation, but not that in each tear secretion, was correlated with the stage of diabetic retinopathy. Given that loss of corneal sensation is a manifestation of diabetic polyneuropathy, these results are consistent with the notion that both diabetic retinopathy and polyneuropathy result from a basement membrane abnormality.

Optical quality of the diabetic eye: a review

“…[16][17][18][19][20][21][22][23][24][25][26] Some ocular manifestations of DM are associated with lachrymal gland dysfunction and have been related to dry eye. Several clinical studies have demonstrated that people with DM are more vulnerable to dry eye than healthy subjects.…”

“…[16][17][18][19] In people with DM, the most frequent and measurable alterations of the tear film function are reduced tear secretion, [16][17][18][19][20][21][22] tear film instability (tear film break-up time (TBUT)), 17,18,20,21 higher degree of conjunctival squamous metaplasia, [16][17][18]21 lower globet cell density, 17,21 and reduced corneal sensitivity. 17,19,21,22 Although the mechanisms of these changes in the ocular surface with DM are still unclear, some studies suggest that diabetic neuropathy affects the innervation of the lachrymal gland and that the fluctuation in the glycaemic control could affect the ocular surface and lachrymal gland secretory function, causing a decrease in basal tear secretion and TBUT. 17,20,21 However, other studies showed that basal tear secretion and TBUT values do not change, but total and reflex tear secretions are significantly reduced in subjects with DM, suggesting that the decreased reflex tearing is due to a diminished sensitivity in cornea and conjunctiva.…”

“…17,20,21 However, other studies showed that basal tear secretion and TBUT values do not change, but total and reflex tear secretions are significantly reduced in subjects with DM, suggesting that the decreased reflex tearing is due to a diminished sensitivity in cornea and conjunctiva. 16,22 Usually the aforementioned findings are accompanied by globet cell loss and conjunctival squamous metaplasia. Goebbels 16 suggested that a decrease in tear secretion together with a disturbed trophic function of the tear film, such as vitamin A and epithelial growth factors, might cause chronic conjunctival damage leading to conjunctival metaplasia.…”

“…29,40 Regarding endothelial cell hexagonality loss (pleomorphism), some authors reported a decrease in the percentage of hexagonal cells. 37,40 A number of studies have shown that people with DM have decreased corneal sensitivity, 17,19,21,22,27,28,33 make them more vulnerable to corneal trauma. Thickening and thinning of Schwann cell basal lamina, irregular distribution in the nerve beading pattern, and occasional axonal degeneration of the nonmyelinated corneal nerves have been found in people with DM.…”

“…86,87 Even though there are no studies evaluating the impact that these factors could have on HOAs in people with DM, these do have a thicker and more convex lens, [54][55][56] can develop premature cataracts, [9][10][11] and suffer a series of changes associated with lachrymal gland dysfunction and dry eye syndrome. [16][17][18][19][20][21][22][23][24][25][26] Patients with DM who undergo laser-assisted in situ keratomileusis are also at a significantly higher risk of developing postoperative epithelial complications, and refractive results tend to be worse compared with healthy people. 88 Few authors have investigated HOAs in people with DM.…”