The importance of the precorneal tear film for the quality of optical imaging.

Abstract

The optical function of the eye critically depends on the presence of an intact precorneal tear film. Abnormalities of the tear film such as those occurring in the dry eye syndrome or in otherwise irritated eyes may interfere with vision. In 30 patients with dry eyes artificial tears were found to produce stastistically significant improvement of vision (p<0001) while no significant changes were seen in the untreated partner eyes. Static perimetry in another 30 patients using the 'macular programme' of the automatic Humphrey 620 perimeter showed artificial tears to increase mean thresholds significantly (p<O0OOl) whereas no significant differences were seen in the untreated partner eyes. One drop ofa 2% poly(vinylpyrrolidone) solution was applied to the right eye and vision was again tested 5 minutes later. Visual acuities before and after tear replacement were compared. Analyses were based on the difference in the number of correctly read optotypes. The untreated left eyes served as controls.In another group of 30 patients with dry eyes (19 females, 11 males; worst vision, 0 8) aged between 43 and 76 years (mean age 61 years) perimetric thresholds were determined 1 day after keratoconjunctivitis sicca had been diagnosed. Using the 'macular programme' of the Humphrey 620 computerised perimeter data were first obtained for the right eye. After instilling artificial tears into the right eye thresholds were determined for the left eye. Then fields were again tested for both eyes with the right eye being examined first. Thresholds in dBthat is, means of three readings, were evaluated. The sum total of all 16 measuring points before tear replacement was compared with that after tear replacement. Statistical analysis was performed with Wilcoxon's matched pair test.5 The untreated left eyes served as controls. ResultsIn the group of patients with tear replacement in OD 25 of the 30 eyes (83%) showed improved visual acuity by 1 to 4 optotypes (mean +2x6 optotypes). In five eyes (17%) visual acuity was unchanged.Of the 30 left eyes which served as untreated controls 17 (56%) showed no statistically significant improvement (1 to 4 optotypes (mean + 1-6 optotypes)). Six eyes (20%) were unchanged. In seven eyes acuity had slightly deteriorated by 1 to 2 optotypes (mean -1-4 optotypes).Statistical analysis using Wilcoxons's matched pair test showed a mean acuity gain of +2-33 optotypes after tear replacement. The difference was highly statistically significant (significance level 99-999%).In the control group a mean gain of +0 54 optotypes was seen, but the difference was not statistically significant (significance level 92-313%) (Fig 1).Macular thresholds determined by static computerised perimetry showed a similar pattern. Of the 30 patients with tear replacement in OD 20 (66-66%) were found to have gained between +1 and +39 dB (mean +11-75 dB), while 10 patients (33 3%) had lost between -1 and -18 dB (mean -8-3 dB).In the untreated controls (30 left eyes) thresholds had increased by + 1 to + 17 dB (mean +6 dB) i...

The effect of artificial tear administration on visual field testing in patients with glaucoma and dry eye

“…There is only one study which evaluates the effect of a tear substitute on visual field and it shows improvement of thresholds in automated perimetry. 12 This study was performed on central 10-2 visual field and there was a significant improvement in macular thresholds (mean þ 11.75 dB).…”

“…This wetting is provided by the tear film which is the 'polish' of the cornea. 12 Thus, any disturbance in tear film quality may result in poor visual quality and discomfort leading to erroneous visual tasks like visual field.…”

“…10,11 In addition to this, toxic and inflammatory effects of antiglaucoma drugs on ocular surface may cause variations of visual acuity and the occurrence of pseudoscotoma seen on perimetry. 12 Any disturbance of precorneal tear film may cause deterioration in visual quality, as cornea and precorneal tear film are the most important optic media of the eye. Reports presented in the literature that show improvement of contrast sensitivity, 13 corneal topography 14 and mean thresholds in automated perimetry 12 in patients with dry eye after artificial tear administration.…”

“…12 Any disturbance of precorneal tear film may cause deterioration in visual quality, as cornea and precorneal tear film are the most important optic media of the eye. Reports presented in the literature that show improvement of contrast sensitivity, 13 corneal topography 14 and mean thresholds in automated perimetry 12 in patients with dry eye after artificial tear administration. There is also one study which studies the tear substitute effect on 10-2 central visual field testing but there is no study which evaluates the effect of a tear substitute on 30-2 program, which is commonly used in patients with glaucoma, on subjects having both glaucoma and dry eye.…”

Tear fluid plasmin activity of dry eye patients with Sjögren's syndrome

“…Tear fluid flow is low, allowing inflammatory agents or topical ophthalmic preparations to remain long in contact with the corneal surface (Burnstein 1985) and enabling them to attain high local concentrations. Visual acuity may also be decreased due to the poor optical properties associated with defective tear film (Gobbels & Spitznas 1989;Reiger 1992;Lancet (1992).…”