Evaluation of the optical effects of healthy and diseased ocular anterior segment structures on quality of vision

When a patient visits an ophthalmologist, usually only visual acuity is
measured, but quality of vision is influenced by more aspects than visual
acuity alone. One of these aspects is straylight. Straylight is the cause of
disability glare, hindrance by oncoming headlights, hazy vision and loss of
colour and contrast vision. Straylight is caused by intraocular scattering of
the light due to disturbances in the ocular media. This scattering of light
results in a veil of light over the retinal projection. Recent research has
shown that straylight and visual acuity contribute equally to quality of
vision.
Patients with ocular anterior segment disorders often complain of reduced
quality of vision, but visual acuity may remain at a normal level, causing
patients to feel misunderstood. It is possible that an increased amount of
straylight contributes to the complaints of these patients. The effect of the
(ab)normal anterior segment on visual quality is not yet sufficiently
investigated.
Until recently there was no reliable and reproducible method for straylight
measurement. In June 2005 a new instrument, the Oculus C-Quant, became
available. With this instrument the amount of intraocular straylight can be
documented quantitatively. This instrument is suitable for clinical use, as the
measurement is non-touch and takes about ten minutes. Currently, straylight
measurements are considered one of the standard ophthalmological examinations.

To document mean and range of straylight values in patients with anterior
segment disorders possibly under several visual angles

- observational case series of quality of vision in patients with anterior
segment disorders

Patients with dry eyes will undergo the following examinations:
1) documenting subjective complaints of reduced visual quality
2) measurement of best corrected visual acuity
3) straylight measurement and measurement of the natural pupil diameter
4) standard slitlamp investigation, with special attention for the tear
break-up time and damage to the anterior ocular segment (conjunctiva and
cornea) by dry eyes
5) schirmer test (meaurement of aqueous tear production)
(all examinations are standardly performed on patients with dry eyes visiting
the outpatient clinic of the department of Ophthalmology)
2) a pilot study will be performed on volunteers and will consist of the
following:
- the tear film will be made extremely turbid with the use of coffee creamer;
the visual effect will be measured with straylight measurements performed just
before the use of coffee creamer and during the 'wash out'-period
- with the use of an eyelid speculum the tear break-up time will be lengthened
to a maximum of 10 minutes (normal tear break-up time is 10 to 15 seconds); the
visual effect of this lengthened tear break-up time will be measured with
straylight measurements peformed at regular intervals during the time the
eyelid speculum is in situ.
- the visual effect of four commercially available lubricants (Hylocomod
eyedrops, optive eyedrops, liposic eye gel and oculentem simplex ointment) will
be measured by straylight measurements performed before the administration of
the lubricants and immediately after administration, as well as 10 minutes, 30
minutes and 60 minutes later.

The measurements will take place during a single visit to the outpatient clinic
of the department of Ophthalmology and will take approximately 1 hour.
No risk is attached to the measurements; the chance of ocular damage or side
effects is practically non-existent.