ALBINISM - CONTROLLING GLARE WITH IRIS TINTED CONTACT LENSES
Rodney Stedall M.C. Optom (UK) Dip Optom FOA (SA)
Hazel Sacharowitz Dip Optom FOA (SA) FAAO
Ria Theotakanis Dip Optom FOA (SA)
Abstract: The authors proposed that
fi tting a Plano iris-tinted contact lens
(clear pupil) to a person with oculocutaneous
albinism will increase visual
comfort by reducing glare sensitivity.
The study concerns the hypothesis that
there will be an improvement in contrast
sensitivity as well as a reduction in
glare discomfort when using this mode
of treatment. Subjects were fi tted with
either a Plano iris tinted contact lens
with a clear pupil (experimental group)
or with a clear Plano contact lens (control
group). Contrast sensitivity was measured
in both groups with and without a
simulated glare source.
Results showed a signifi cant difference in contrast values in
the experimental group when comparing results with and
without the contact lens under glare conditions. For the
control group, no signifi cant difference was noted under
no glare conditions, yet under glare conditions, one eye
showed signifi cant difference. It was further noted that the
mean contrast sensitivity of the experimental group seemed
to improve in all settings (with and without glare) after the
fi tting of an iris tinted contact lens. Due to the small number
of subjects in this study, we cannot however conclusively say
that visual comfort was enhanced with the fi tting of iris tinted
is the most common type
of albinism in Africa1,2. Persons
albinism are characterised
by varying degrees of congenital
including a reduction in
the pigment melanin in the
hair, skin and eyes. Low vision
are often directed towards
controlling illumination with
tinted lenses, ultraviolet protection
or coloured contact lenses,
visors and hats to reduce
symptoms of photophobia.
In the normally pigmented
eye, iris pigmentation controls
the amount of light
entering the eye. However,
the lack of iris pigmentation
in a person with albinism
may result in the person
experiencing disabling glare
and reduced visual function
in bright surroundings. Rubin6
describes disability glare as
glare that reduces visibility of
a target due to the presence
of a light source elsewhere
in the visual fi eld. Light from
the glare source is scattered
by the ocular media and
forms a veiling luminance which reduces the contrast
and thus the visibility of the
target. Discomfort glare on
the other hand, refers to
the sensation experienced
when the overall illumination
is too bright, for example
when the sun is refl ected
off a shiny surface such as a
windscreen. The complaint
of sensitivity to light and
trouble seeing in the bright
sun in persons with albinism
was assumed to be as a
result of reduced contrast
sensitivity in the presence of
glare (disability glare). Disability
glare responses can
be obtained by comparing
conventional visual function
tests such as visual acuity
or contrast sensitivity in the
presence and absence of a
Methods and materials
Twenty four subjects between
the ages of 11 and
20 years where randomly
fi tted with either clear
(control group) or iris-tinted
(experimental group) Plano
soft contact lenses. All
subjects were scholars from
Prinshof School for the Visually Impaired and were identified as having oculocutaneous
albinism. Eleven of the subjects of mixed gender
where randomly allocated in the control group and the remaining
thirteen subjects formed the experimental group as
can be seen in Table 1.
Subjects wearing habitual spectacle corrections were instructed
not to remove the spectacles during all testing
procedures. Visual acuity was assessed using the EDTRS high
contrast acuity chart7 at standard illumination levels. Contrast
sensitivity was repeatedly measured with the Pelli-Robson
Contrast Sensitivity Chart8-10 Clement Clark at standard
room illumination with and without a glare source.
The assessment was divided into six stages and each stage
was administered and recorded by the same examiner throughout the study in order to maintain consistency and
increase accuracy. Visual acuity was assessed in the first
stage using the high contrast Lighthouse Distance Visual
Acuity Test Chart11 at the appropriate testing distance and
with standard illumination. A sequence of measuring right
eye distance visual acuity followed by measurement of the
left eye and then both eyes was followed throughout the
study. Results were scored12 by recording the total number
of letters read correctly. Each letter read added one point
to the score; each line added five points. This method follows
the ETDRS protocol and was shown by Raasch et al13
to provide greater accuracy when multiple measurements
have to be averaged, compared or otherwise statistically
Contrast sensitivity levels were then measured using the Pelli-
Robson letter sensitivity chart with and without a simulated
glare stimulus. Glare was simulated using a round 22 watt
fl uorescent 21cm bulb mounted in a black plastic cone that
was positioned at a distance of 15cm from the eye base as
can be seen in Figure 1.
The glare source can be a spot, bar, ring of light or an extended
bright background according to Rubin6. Extended
glare sources, such as the annulus produced by a circular
fl uorescent tube, cause fewer afterimage problems and are
said to be better accepted by patients14. Two charts with
different letter sequences but otherwise identical were positioned
at a distance of 1 meter from the subject at the level
of the subject's eyes. The luminance of the white areas was
approximately 100cd/m2. In keeping with the scoring protocol
of the Pelli- Robson chart, subjects were instructed to
read each letter across the chart starting with the dark letters
in the upper left-hand corner. A forced choice procedure
whereby the subject is asked to identify the letters and the
examiner determines whether the answers are correct or incorrect
was followed. Subjects were instructed to continue
until two of the three letters in a triplet were read incorrectly.
Forced-choice tests yield more reliable results than criteriondependent
tests, especially with unpracticed observers15.
The mean results were calculated for the right eye, left eye
and both eyes and are represented in Table 2.
Subjects were then randomly fitted with either a clear soft
contact lens or an iris-tinted soft contact lens illustrated in
Figure 2. The control iris-tinted contact lens used was a
disposable clear Plano Proclear lens with a light transmission at 560nm of 94%. The experimental subjects were fitted
with Plano Hydron Z6 contact lenses that were tinted in a
"doughnut" fashion using a dark amber brown tint with a
4.5mm clear pupil and 11.5mm outside diameter. The clear
pupil had a visible light transmission of 94% and the amber
tint measured 14% transmission at 560nm which is similar to
the 17% absorption of natural melanin pigment16 of the eye.
Pupil size and iris colour were noted. All subjects were given
a minimum of fi fteen minutes to adapt to the contact lenses
and then asked a series of questions as indicated in Table 3
relating to day-to-day adaptations to glare sensitivity. The
subjects were then reassessed for contrast sensitivity using
the Pelli-Robson sensitivity chart with the same non-glare
and glare test sequence and procedure as before the contact lens was inserted. The right contact lens was removed
standing near an external glare source and the subject
was asked to compare the two eyes and questioned as
to which eye was now more sensitive to light.
Disability glare can be modeled in terms of veiling luminance
scattered into the test target from a glare source. The veiling luminance
effectively reduces image contrast and the amount
of scattered glare light determines the magnitude of contrast
deduction. In a study of glare sensitivity with simulated
ocular turbidity, the glare light caused contrast sensitivity to
decline rapidly, while acuity remained near normal17. Tests
based on contrast sensitivity measures should therefore be
more sensitive to disability glare than tests based on acuity
alone. The Pelli-Robson chart has been widely used by
researchers and was chosen as it is easy for young subjects
to understand due to its similarity to letter acuity testing, it is
fast to administer and has proven18-20 reliability. This variable
contrast chart consists of 16 triplets of letters arranged in 8
rows of two triplets each. The letters remain constant in size
and each subtends 2.8 degrees at a 1 meter test distance.
As the subjects read across the chart the letters reduce in
contrast. The last triplet in which the subject reads 2 of 3 letters
correctly, determines the level of contrast sensitivity. Ruben6
reported that it makes sense to measure contrast sensitivity
to assess disability glare due to the phenomenon that disability
glare can be modeled in terms of veiling luminance scattered
into the test target from the glare source. The veiling
luminance effectively reduces image contrast. The amount of
scattered glare light will determine the magnitude of the contrast
reduction and thus contrast sensitivity is measured in order
to assess disability glare.
The reduction of pigment in both the anterior and the
posterior segment of an oculo-cutaneous albinotic eye produces
diffused intraocular light and increased ocular light
scatter within the eye. Van den Berg21 reported that people
with retinal hypopigmentation have increased intra-ocular
light scatter. Rosenblum et al22 used colored fi lters to study
their effect on visual function in visually impaired subjects
with different kinds of ocular pathology. All subjects including
those with albinism, reported subjective improvement including
reduction of photophobia, eyestrain and eye discomfort.
These results correlate with verbal responses to the questionnaire
in this study. Hoeft and Hughs23 found that subjects with
albinism benefi ted from amber tints with a gradual cut-off at
500nm. Dark amber fi lters which cut off the short-wave part
of the spectrum signifi cantly decrease light sensitivity and
diminish symptoms of photophobia and high glare sensitivity.
Barron24 suggested that opaque artifi cial iris lenses and
dark translucent tinted lenses may reduce photophobia and
glare by creating an artifi cial light stop. Iris tinted soft contact
lenses with an amber brown tint in a "doughnut-like" fashion
where thus designed for this preliminary study.
Statistical analysis using before and confounding variables
confi rmed no signifi cant difference in the experimental and
control groups. A comparison of the contrast sensitivity results
before a contact lens was fi tted with and without simulated
glare is presented in Table 4.
The mean value is represented. The bracketed value is the
standard deviation. Similarly, Table 5 represents the mean
value of the contrast sensitivity for each group after being
fi tted with either a clear or tinted contact lens. Statistically no
signifi cant difference was found between the control and
experimental groups thus making the groups comparable.
Table 6 represents outcome results when comparing the
mean results with and without an iris-tinted contact lens
under the different glare conditions. The value in brackets
represents the Signifi cance or "p" value. A "p value" less
than 0.05 in the experimental group represent a significant difference in results when comparing subjects with and without
the contact lens. A "p" value greater than 0.05 in the
control group represents a signifi cant difference in results
when comparing subjects with and without the contact lens.
The outcome results show a signifi cant difference in contrast
values in the experimental group when comparing results
with and without a contact lens under glare conditions. The
results without glare are not as conclusive possibly due to
the small number of subjects in the study. However, when
studying the slope in the Figures 3 and 4, the mean contrast
sensitivity of the experimental groups increased in all
settings (with and without glare) after the fi tting of an iristinted
contact lens. The gradient of the slope of the control group indicates that the clear contact lens had less effect
on the contrast sensitivity findings.
Eye care practitioners are aware that many patients with albinism
complain of visual discomfort in bright light. Responses
from the questionnaire confi rm this clinical impression and
reduced contrast sensitivity responses under simulated glare
confi rm a change in the visual system. However, we cannot
conclusively say that visual discomfort was improved with
the fi tting of iris tinted contact lenses probably due to the
small number of subjects in the study. The contact lenses
provided a natural appearance when indoors and outdoors
and were readily accepted by the subjects. Further research
is indicated to relate disability glare fi ndings to the subjective
visual comfort experienced.
We wish to thank Cooper Vision (SA) (Pty) Ltd for sponsoring
the contact lenses and Prinshof School for the Visually
Impaired for their support.
Kromberg JGR, Jenkins T. Prevalence of albinism in the South African Negro. SAMJ
1982 61 383-386.
Kromberg JGR. Albinism in Southern Africa. S Afr J Sc 1987 83 68.
Faye EE. Clinical low vision. Boston: Little, Brown and company. 1984 pp 259-261.
Kanski JJ. Clinical Ophthalmology: A synopsis. Butterworth Heinemann. 2004 pp287.
Brilliant RL. Essentials of low vision practice. Butterworth Heinemann. 1999. pp 83-84.
Schachat AP. Current practice in ophthalmology. Mosby. 1992. pp 153-162.
Brilliant RL. Essentials of low vision practice. Butterworth Heinemann. 1999. pp 25-27.
Pelli DG, Robson JG, Wilkins AJ. The design of a new letter chart for measuring contrast
sensitivity. Clinl Vision Sci 1988 2 3.
Pelli DG, Rubin GS, Legge GE. Predicting the contrast sensitivity of low vision observers.
J Opt Soc Amer 1986 3 56.
Rosenthal BP, Cole RG. Functional assessment of low vision. Mosby. 1996. pp 77-88
Rosenthal BP, Cole RG. Functional assessment of low vision. Mosby. 1996. pp 41-
Visual standards- aspects and ranges of vision loss. April 2002. ICO report Sydney
Raasch TW, Bailey IL, Bullimore MA. Repeatability of visual acuity measurement.
Optom & Vision Sci. 1998 75 5.
Legge GE, Rubin GS, Luebker A. The role of contrast in normal vision. Vision Res
1987 27 1165-1177.
Higgins KE, Jaffee MJ, Coletta NJ, Caruso RC, de Monasterio FM. Spatial contrast
sensitivity:Importance of controlling the patient's visibility criterion. Arch Ophthalmol
1984 102 1035-1041.
Hammond BR, Nanez JE, Fair C, Snodderly DM. Iris color and age related changes
in lens density Ophthal & Physiol Opt 2000 20 5.
Miller D, Jernigan ME, Molnar S, Wolf E, Newman J. Laboratory evaluation of a clinical
glare tester. Arch Ophthalmol 1972 87 324-332.
Rubin GS. Reliability and contrast sensitivity of clinical contrast sensitivity tests. Clin
Vision Sci 1988 2 3 169-177.
Woods RL, Wood JM. The role of contrast sensitivity charts and contrast letter charts
in clinical practice. Clin Exp Optom 1995 78 2.
Elliot DB, Sanderson K, Conkey A. The reliability of the Pelli-Robson contrast sensitivity
chart. Ophthal Physiol Opt 1990 10 21-24.
Van den Berg TSTP. Importance of pathological light scatter for visual disability.
Doc Ophthalmol 1986 61 327-333.
Rosenblum YZ, Zak PP, Ostrovsky MA, Smolyaninova L, Bora EV, Dyadina UV, Trofi -
mova NN, Aliyev AGD. Spectral fi lters in low-vision correction. Ophthal Physiol Opt
2000 20 334-341.
Hoeft WW, Hughes MK. A comparative study of low-vision patients: their ocular
disease and preference for one specifi c series of light transmission fi lters. Am J Optom
Physiol Opt 58 8.
Stuen C, Arditi A, Horowitz A, Lang MA,Rosenthal B, Seidman K. Vision Rehabilitation
: assessment, intervention and outcomes. Swets & Zeitlinger. 2000. Barron C.
Prosthetic contact lenses for people with blindness or partial sight. pp 173-176.