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Scleral contact lenses: indications 

and current clinical methods 

Ken Pullum, Senior Optometrist, Moorfields Eye 

Hospital, London and Oxford Eye Hospital 

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Scleral contact lenses (ScCLs) predate rigid corneal and hydrogel lenses by 

seven decades, but still have a unique clinical role. The general perception is 

that they are only useful in the most advanced cases of ectatic corneal disease, 

the fitting process is cumbersome, they are uncomfortable to wear and they 

are the cause of hypoxic corneal changes. Professional instruction has become 

a low priority in recent years, hence relatively few practitioners have an 

understanding of sclerals’ unique advantages or the transformation in clinical 

methods and manufacturing techniques enabled by the introduction of rigid 

gas permeable (RGP) materials 1 . Contrary to popular belief, most RGP ScCL fitting 

is a straightforward and predictable process, so consequently, they are 

also a feasible option for very much lower levels of pathology, rather than at 

a stage which would be described as end point. For example, they may be 

offered when patients can still be fitted with corneal lenses, but are 

experiencing discomfort and excessive lens mobility. 

2 standard CET points 

1 CET point 

Module 5 Part 4 

Specialist contact lens 

fitting 

About the author 

Ken Pullum is a Senior 

Optometrist at Moorfields 

Eye Hospital with a special 

interest in medical indications 

for contact lenses and 

developments in modern 

scleral lens practice. 

Lens types: fenestrated or 

non-ventilated 

A ventilated ScCL includes a design feature 

which enables fresh oxygenated tears to 

access the cornea. The expression sealed 

has two conflicting meanings in ScCL practice. 

In reference to scleral lens categorisation, 

it is used to indicate a lens with no 

intended means of ventilation incorporated 

into the design. In a clinical context, its use 

describes the appearance in situ of a lens 

which beds down on the sclera so there is 

no or only an insignificant tear exchange. 

A fenestration 2 is the most widely used of 

ventilation and can be used for both preformed 

and impression lenses. Channels 

and slots are alternatives for impression 

lenses, but do not function well for preformed 

lenses as the improved scleral zone 

apposition and centration of impression 

lenses is required for either to function 

properly. 

It is quite possible that a non-ventilated 

coaxial ScCL may have a functional tear 

exchange if the underlying sclera is irregular, 

therefore is not sealed. Conversely, if an 

intended ventilation feature is non-functional 

for some reason, say if a fenestration 

is blocked, the lens may effectively be 

sealed. For clarification, use of the term 

sealed in the remainder of this text refers to 

a lens which bears on the sclera so that 

there is no or insignificant tear exchange, 

and non-ventilated to a lens constructed 

without a fenestration or other intentional 

means of ventilation. 

Lens types: impression or 

preformed 

ScCLs can be specified after preformed trial 

diagnostic lenses of known parameters 

have been evaluated in situ, or an individually 

bespoke lens may be produced on the 

basis of an eye impression. Impression lenses 

can be used virtually irrespective of irregular 

topography. Prior to the introduction of 

RGP materials this was the more versatile 

system as the great majority of the cases 

were fitted with ScCLs because of irregular 

corneal topography. 

The introduction of RGP materials shifted 

the emphasis back to preformed for two 

reasons. Firstly, RGP materials are not sufficiently 

thermoplastic to be pressed over a 

cast, which is the simple traditional method 

used for PMMA. It is possible to make RGP 

impression lenses, but the process is much 

more cumbersome requiring precision 

milling or moulding. Secondly, corneal 

swelling studies show that nonventilated 

high Dk RGP ScCLs reduce 

26 | October 20 | 2006 | OT



corneal swelling to a level comparable to 

normal overnight swelling, thus 

reintroducing the option of fitting ScCLs 

without the complicating impact of 

incorporating a fenestration 3,4,5 . 

Advantages and 

disadvantages of ScCLs 

Advantages 

The large size creates a scleral bearing surface 

and retains a pre-corneal fluid reservoir 

providing optical neutralisation of an astigmatic 

or irregular corneal surface and 

corneal hydration. Very high powers, up to 

+/- 40.00D, are possible because there are 

minimal lid traction and centre of gravity 

effects. They cannot be dislodged by the lids 

and are often relatively comfortable even 

for the unadapted eye because the lid 

margin is in contact with the surface of the 

lens rather than the edge. If RGP non-ventilated 

ScCLs are used, corneal contact can be 

minimal. 

ScCLs, including RGP lenses, can be kept 

dry when not being worn. There is no risk of 

contaminated storage solutions since none 

is used, so the risk of infections is reduced. 

They are robust, the surface can be polished 

or resurfaced periodically, and they are not 

easily lost. Less dextrous patients may 

find them easier to handle because they do 

not need to be precariously balanced 

on a fingertip. 

Disadvantages 

While not producing any lid sensation, there 

is a feeling and an appearance of bulk, and 

some people are intimidated by their large 

size. They cover a large area of the anterior 

globe, considerably reducing the oxygen 

available to the cornea, although the introduction 

of RGP materials has led to a major 

improvement. Because they are fitted with 

corneal clearance, the VA and the ability of 

the lens to reduce distortions in ectatic 

corneal conditions may be reduced compared 

to rigid corneal lenses. However, if an 

RGP ScCL can be worn when a corneal lens 

cannot, the comparison is not valid. 

Indications 

ScCLs are indicated simply when the unique 

advantages of ScCLs can be applied. They 

can be considered to manage any eye condition 

if there is a strong enough reason for 

contact lens correction, and in the management 

of some ocular surface disease. There 

have been a number of publications in 

recent years describing ScCL applications. 

6,7,8,9,10,11,12,13,14,15,16,17,18 

Irregular or abnormal 

corneal topography 

Corneal ectasia 

Keratoconus or other primary corneal 

ectasias (PCE) form the majority of current 

indications for ScCLs. RGP corneal lenses 

Figure 2 Irregular corneal topography 

as a consequence of a transplant that has 

unexpectedly sprung forward. There is a 

clear depression in the superior 

mid-periphery which would be a major 

problem for corneal lens fitting. A nonventilated 

RGP ScCL is unaffected by a 

localised irregularity like this provided it is 

sealed on the sclera 

may be simply impossible to fit in very 

advanced cases, for example, as shown in 

Figure 1, but there is also an application for 

ScCLs when corneal lenses persistently 

dislodge, or are not well tolerated due to 

excessive mobility or the formation of 

epithelial erosions. 

Corneal transplant 

The second largest group for which ScCLs 

are indicated are post-corneal transplants if 

there is a residual refractive error, or if the 

surface remains irregular, illustrated in 

Figure 2. Even if the astigmatism is very 

high, which still happens sometimes even 

with the most expert surgery, non-ventilated 

RGP ScCL fitting post-transplant is usually 

a comparatively straightforward exercise. 

The lenses are fitted with full corneal 

clearance irrespective of corneal topography, 

therefore the appearance is much the 

same whether the cylinder is 2.00D or in 

excess of 20.00D. 

Figure 1 Downwardly displaced apex in an advanced keratoconus. Many corneal 

lenses were tried, but all dislodged almost immediately. ScCL fitting was a straightforward 

process with only two lenses necessary to establish corneal clearance 

Corneal trauma or postsurgery 

The vision in traumatised eyes with corneal 

scarring may be improved with ScCLs if the 

injury has caused irregularities, but has left 

some areas of reasonably transparent 

cornea in the pupillary region. Some cases 

of unsuccessful refractive surgery may benefit 

if supplementary correction with rigid 

contact lenses is helpful in reducing visual 

disturbances such as starbursting and 

27 | October 20 | 2006 | OT



ghosting. Grossly abnormal topography 

would not be expected after refractive surgery, 

but some patients remain intolerant of 

corneal lenses, in which cases ScCLs 

could be tried. 

Normal topography with high 

refractive errors 

ScCLs may be indicated when high power 

rigid corneal lenses cause intractable problems 

of excessive mobility or poor centration. 

They may be used whatever the 

ametropia if there is intolerance to corneal 

or hydrogel lens wear in high myopia, or 

hypermetropia or significant non-pathological 

corneal astigmatism. 

Therapeutic or protective 

applications 

ScCLs uniquely retain a pre-corneal fluid 

reservoir providing corneal hydration in serious 

dry eye conditions, such as Stevens 

Johnson Syndrome or ocular cicatricising 

pemphigoid. A ScCL in situ may give an 

improved environment for corneal healing 

where newly formed epithelium is continually 

sloughed away by the action of the lids, 

or may prevent tear film evaporation with 

poor lid closure or lid absence. The lens 

retains a fluid reservoir which maintains 

some degree of corneal hydration and 

protects the cornea from trichiasis and lid 

margin keratinisation, and the front surface 

provides hugely improved refracting surface, 

giving a considerable visual benefit. 

There is also an application in less severe 

dry eye or tears dysfunction pathology. 

Sometimes the patient may describe very distressing 

and disproportionate ocular discomfort 

with very little visible corneal disruption. 

Mucus filaments adherent to the cornea are 

very painful when they pull on the epithelium 

or finally detach, but wave freely in the precorneal 

fluid reservoir behind a ScCL, and 

appear to float off into the fluid pool with little 

discomfort. ScCLs may be used as a prop 

for some cases of ptosis. 

Cosmetic shells 

A realistic iris can be encapsulated into 

PMMA scleral shells to mask unsightly blind 

eyes, or to relieve intractable diplopia or 

glare in cases of aniridia. 

Recreational or occupational 

applications 

Particles behind rigid corneal lenses in dusty 

work place environments are very troublesome. 

ScCLs eliminate this problem almost 

entirely. Most recreational activities are satisfactorily 

managed with the use of hydrogel 

lenses, but ScCLs are still indicated on 

occasions for contact or water sports. 

ScCL fitting options 

Ventilation by some means is a prerequisite 

for PMMA lenses whether impression or preformed, 

but non-ventilated designs are the 

preferred option for RGP. Some limitations 

still remain for irregular ocular topography 

with RGP preformed sclerals, but considerably 

more irregular eyes can be fitted using 

preformed RGP sclerals because of the tear 

reservoir compared to fenestrated PMMA. 

Impression lenses of some kind can be used 

virtually irrespective of irregular topography. 

All the following alternatives are possible, 

and have different applications. 

RGP 

RGP sclerals should now be considered the 

first choice for the great majority of ScCL 

cases. Some long-term wearers have worn 

the lenses for over 50 years, so these should 

be considered a long-term option for most 

new referrals. As the great majority of ScCL 

referrals are for PCE or corneal transplant, it is 

crucial to minimise the risk of corneal hypoxia. 

A transplant may have to be a future management 

option for any PCE referred for ScCL 

fitting. If so, corneal neovascularisation, while 

not necessarily sight-threatening in its own 

right in the early stages, may increase the risk 

of transplant rejection. 

Preformed non-ventilated RGP can be 

used for the great majority of cases, irrespective 

of corneal topography. There are more 

potential problems with the scleral topography, 

but if the scleral zone is well enough 

sealed, a pre-corneal fluid reservoir is 

retained without bubbles and with minimal 

settling on the globe. The optimum clearance 

at the visual axis is approximately 0.25mm, 

but can be more than twice that value at the 

limbus in some sectors without causing any 

problems provided it remains air free. 

The principal problem with preformed 

non-ventilated RGP ScCLs is that they have 

to be inserted filled with saline. This requires 

keeping the lens horizontal at the moment 

of insertion, so it is necessary also to have 

the patient’s head horizontal and facing the 

floor. This is a more difficult task for 

patients, and sometimes for the practitioner 

as well, compared to the relatively simple 

procedure for inserting a fenestrated lens, 

which can be inserted with the head in the 

normal upright posture. 

Preformed fenestrated RGP is indicated 

if a fenestration is beneficial, for 

example, if retention of the pre-corneal fluid 

reservoir at the moment of insertion is 

impossible. However, there is a serious limitation 

because air bubbles are admitted into 

the pre-corneal fluid reservoir and cross the 

visual axis if the pre-corneal fluid reservoir 

depth is greater than 0.1mm. It is unlikely 

that a tear pool of uniformly shallow depth 

can be maintained with even just a moderately 

irregular corneal topography. 

Impression non-ventilated RGP is an 

option if there is an intractable problem 

retaining an air free pre-corneal fluid reservoir 

with a non-ventilated preformed 

design. The ultimate fitting target is a flush 

back surface for the scleral zone and an 

optic zone clearance similar to that for a 

non-ventilated preformed RGP. As the scleral 

zone is fabricated from an eye impression, 

a very good alignment can be expected with 

effective sealing on the scleral zone, hence 

there is scope for increasing the optic zone 

clearance with a good prospect of retaining 

a pre-corneal fluid reservoir. 

Impression fenestrated RGP is a major 

undertaking because it is a departure from 

mainstream manufacturing and, in 

addition, requires very precise fabrication of 

the back surface to keep a uniform depth of 

the pre-corneal fluid reservoir. However, 

there may be a better chance than with a 

fenestrated preformed RGP lens because 

the optic zone is individually fabricated from 

the exact shape of the eye. 

PMMA 

PMMA ScCLs still have a role to play but 

there is an acknowledged long-term threat of 

hypoxic corneal changes, so these would not 

normally be the first choice for new ScCL 

wearers. However, if a PMMA lens has been 

worn successfully for some years without significant 

sequelae, there is no reason for a 

change is to be made. Most impression 

PMMA lenses for moderate or advanced 

corneal ectasias were ventilated, hence the 

initial clearance at the visual axis could not be 

much more than 0.1mm. After a period of 

settling on the globe, an almost universal 

occurrence with a ventilated lens, the result 

was apical contact. The author’s observation 

is that contact is better tolerated in PMMA 

than with RGP materials. The probable explanation 

is the increased co-efficient of friction 

28 | October 20 | 2006 | OT



for RGP materials compared to PMMA. 

For the same reason, there may be more 

surface/tarsal plate interaction with RGP 

compared to PMMA. Furthermore, the visual 

performance in terms of visual acuity, 

contrast and reduction of distortions or 

ghosting is reduced when there is a visual 

axis contact zone. 

Impression ventilated PMMA proved to 

be a successful option in many cases before 

RGP materials were available. A ventilated 

impression PMMA lens is easier to produce 

than RGP due to its superior thermoplasticity, 

and because it can be cut and polished 

with minimum risk of irreparable damage. 

Impression ventilated ScCLs very often have 

central corneal contact zones after settling 

back, irrespective of the material. If so, PMMA 

is more likely to be tolerated. Impression 

PMMA is arguably the method of choice for 

elderly aphakes. Centration is optimised with 

the impression method of fitting as there is a 

near glove fit on the sclera. Thus the front 

optic can be sited over the visual axis to 

minimise aberrations. 

Preformed fenestrated PMMA may be 

a preferable option to RGP fenestrated 

because it may be fitted with less initial 

clearance so that apical contact following 

any settling on the globe is better tolerated 

than if an RGP lens is similarly fitted. 

However, the chances of a successful outcome 

with a moderately or advanced ectasia 

and irregular topography remain limited 

for the reasons discussed previously. 

Impression or preformed nonventilated 

PMMA has no place for long 

term wear as the onset of hypoxia is very 

rapid. However, it is worth remembering that 

advanced keratoconus causes extremely poor 

unaided vision and spectacles may do next to 

nothing by way of correction. 

Therefore, all contact lens options should 

be borne in mind. If good vision to deal with 

a particular task is urgently required for a 

few minutes, a non-ventilated PMMA lens 

provides just that. 

The fitting and production are the simplest 

for all scleral lens types provided the 

scleral zone seals adequately on the sclera, 

which should be the case following an 

impression lens if not with a preformed lens. 

Preformed non-ventilated RGP 

ScCL fitting 

PMMA ScCLs, whether preformed or 

impression of preformed, are comparatively 

infrequently required nowadays. The fitting 

Figure 3 Optimum preformed lens fitting with scleral alignment and optic zone clearance 

Figure 4 Steep fitting scleral zone 

illustrating fluorescein encroaching almost 

to the periphery of the lens. There is also a 

small amount of blanching at the edge 

Figure 5 Flat fitting scleral zone on the 

same eye as seen in Figure 4. The 

fluorescein is only seen just beyond the 

limbus, and there is obvious blanching in 

the mid-periphery 

systems for both have been well documented 

in previous textbooks and summarised 

recently 19 , so it is not appropriate to expand 

further on the preceding discussion which 

outlines their role. 

However, the fitting processes for RGP 

ScCLs have been more recently developed, 

hence the principles are outlined in the following 

text. 

Lens diameter 

The diameter is chosen according to the 

appearance at the assessment and fitting 

process, and can be between 16mm and 

25mm. In fact, 18mm to 23mm is a more 

usual range for preformed lenses. Indeed, 

16mm is very small for a lens to be defined 

as a ScCL, that is, having a scleral bearing 

surface and essentially with corneal clearance. 

If the corneal diameter is taken to be 

12mm, and it is deemed desirable to allow 

an extra 1mm all round for limbal clearance, 

a 16mm total diameter only allows a 1mm 

scleral bearing annulus. The author 

acknowledges the valuable role for lenses 

with a diameter smaller than 16mm, but 

they do not conform to this definition of a 

ScCL and are fitted according to a different 

rationale. 

A small variation in the diameter may not 

make much difference, but if a lens were to 

be made progressively smaller the original 

bearing surface would eventually be eliminated. 

The new bearing surface would then 

be the sector of the sclera which was previously 

the transition zone with the larger 

diameter lens. The result is likely to be 

29 | October 20 | 2006 | OT



Figure 6 The optic zone sagitta, and consequently, the apical clearance, is increased 

by steepening the BOZR 

Figure 7 The optic zone parameters 

can be defined according to the projection 

of the optic zone from the continuation of 

the scleral curve measured axially at the 

apex and at the limbus 

increased settling back with reduction of 

the optic zone clearance. 

There are some comparative advantages 

and disadvantages of smaller and larger 

lenses. The author’s observation is that the 

scleral topography just outside the limbus is 

more regular and symmetrical than the 

more peripheral sclera. Smaller diameter 

ScCLs may be indicated when a tighter fitting 

is necessary. For example, they should 

be tried when a non-ventilated 23mm diameter 

lens fails to seal well enough on the 

sclera to prevent admission of an air bubble 

into the pre-corneal reservoir. Bearing on 

the most symmetrical region of the sclera 

leads to noticeably less decentration, which 

may reduce any prismatic effects. 

Smaller lenses can be made thinner than 

larger lenses because the rigidity is greater 

with smaller diameter lenses. The reduced 

mass, and less movement on the eye compared 

to larger lenses, may render a contact 

zone more tolerable. Hence they can be fitted 

with less corneal clearance, which may 

prove to be advantageous if the vision is 

improved with a visual axis contact zone. A 

final advantage of the improved centration 

and closer proximity to the cornea is a more 

even depth of the pre-corneal fluid reservoir, 

this increases the possibility that a fenestration 

can be more successful than with larger 

diameter lenses. However, on the downside, 

the increased tightness of the fitting on the 

eye and the reduced limbal clearance are significant 

drawbacks at times. Although such 

lenses are more likely to retain an air-free 

pre-corneal reservoir they are more difficult 

to insert without a bubble in the first place, 

and because they fit tighter on the eye, they 

are distinctly more difficult to remove than 

larger diameter lenses. 

Optimal scleral zone alignment 

The bearing surface should be spread as 

evenly as possible over the sclera, but with 

optic zone clearance. In fact, 13.50mm to 

14.50mm is a usual back scleral radius (BSR) 

range for most preformed ScCLs. The bearing 

surface is displaced away from the limbus 

if the scleral zone is too steep, and may 

cause the lens to vault as it rests only at the 

periphery, giving an appearance of excessive 

apical clearance. A flat fitting scleral zone 

shifts the bearing surface nearer to the limbus, 

but does not appreciably affect the apical 

clearance. Figure 3 diagrammatically 

illustrates scleral zone alignment and 

corneal clearance. Figures 4 and 5 are fluorescein 

photographs showing a steep and 

flat fitting scleral zone respectively. 

A glove fit on the sclera is not possible, 

nor essential, but the scleral zone needs to 

be sufficiently sealed to prevent the introduction 

of air bubbles into the pre-corneal 

fluid reservoir. An overall view of the scleral 

zone with a hand-held low magnification 

lamp is sufficient to see the extent of the 

clearance beyond the limbus. Any areas of 

conjunctival blood vessel blanching, which 

are due to localised compression while the 

lens is in situ, can be seen simultaneously 

with a white light source. 

Corneal and limbal clearance 

Achieving optimal clearance at the limbus 

and at the apex is determined by varying the 

back optic zone radius (BOZR) and the back 

optic zone diameter (BOZD) in combination 

to give the optic zone sagitta (OZS). Varying 

the BOZR with a constant BOZD gives rise to 

a precisely calculable change to the central 

corneal clearance, as in Figure 6, but varying 

the BOZD with a constant BOZR does not 

because the curvature of the scleral bearing 

surface is an unknown quantity. This is the 

same principle as traditional style PMMA 

ScCL fitting, but most modern fitting 

systems utilising the OZS principle calculate 

the combined specifications to give significant 

variations in apical and limbal 

clearance, therefore it is not necessary for 

the practitioner to try combinations of 

BOZRs and BOZDs. 

The corneal clearance can also be varied 

by changing the optic zone projection (OZP) 

in progressive increments but without reference 

to the BOZR or BOZD. Figure 7 illustrates 

OZP diagrammatically. The optic zone 

Figure 8 Off-axis apical contact zone in 

an advanced keratoconus wearing a nonventilated 

RGP scleral lens. This amount of 

contact was tolerated by the wearer and 

did not lead to any corneal erosion 

30 | October 20 | 2006 | OT



Figure 9 The same eye as seen in 

Figure 8 with a significant increment in the 

optic zone projection illustrating full 

corneal clearance. 

comparison to the corneal thickness, as 

shown in Figure 10. The fluorescence can 

be seen perfectly well with white light; 

cobalt blue filters reduce the brightness too 

much for the corneal thickness to be seen 

well. 

Apical clearance between 0.2mm and 

0.3mm is a satisfactory target for a nonventilated 

ScCL, approximately half a normal 

corneal thickness, with the pre-corneal 

fluid reservoir extending just beyond the 

limbus. The exact measurement of corneal 

clearance is not critical, although if excessive 

it is more difficult to maintain an 

air-free pre-corneal fluid reservoir or for the 

patient to insert the lens without an air 

methods consequent to the introduction of 

RGP materials. There are many fitting 

nuances which could not be covered, and 

there are significant problem areas which 

have only briefly been touched upon. 

However, it is emphasised that the fitting 

processes have become straightforward and 

predictable in most cases, with a rapid 

arrival at the end-point mostly using nonventilated 

preformed RGP designs. 

ScCLs may be lens-of-choice when a 

result is needed more than at any other 

time. There are no conditions for which they 

cannot be considered, so it is clearly necessary 

to preserve the clinical and manufacturing 

skills required . Since the introduction of 

is defined according to two axially measured 

parameters: the OZP from the extrapolation 

of the scleral curve measured at the apex 

and at the limbus. These increments are just 

clinically significant enough to keep the 

number of lenses in the fitting system 

manageable. OZP is a function of the BSR, 

hence if the BSR is flattened, the OZP needs 

to be increased to compensate. 

The OZS or OZP for an initial trial lens is 

selected from an assessment of the overall 

corneal profile with the naked eye. If inaccurately 

estimated, there is no major loss as 

the first lens inspected in situ gives a clear 

indication for subsequent lens selection. 

Keratometry and corneal topography are of 

limited value as neither provides any information 

about the peripheral cornea or the 

projection from the sclera. 

The parameters are assessed simultaneously 

with the lens in situ, but the initial decision 

must be to determine the optimum 

scleral zone specifications as the scleral zone 

has an impact on the optic zone clearance. 

The lens is inserted filled with saline and fluorescein 

so that areas where the lens is clear 

of the surface can be easily distinguished 

from areas where the lens is in contact. 

Figures 8 and 9 demonstrate the effect of 

increasing the OZP to reduce corneal contact. 

Slit lamp biomicroscopy 

assessment of the optic zone 

If fluorescein is added to the saline prior to 

insertion, inspection of the optic zone using 

a cobalt blue filter shows any corneal 

contact zones. A slit lamp optical section 

can be used to measure the optic zone 

clearance. A pachometer is not necessary 

but the depth of the pre-corneal reservoir 

can be estimated with sufficient accuracy by 

Figure 10 Slit lamp optical cross section demonstrating the pre-corneal fluid reservoir. 

The lens, the reservoir and the cornea are all clearly seen in cross section. The depth of 

the reservoir is just less than the corneal thickness at the visual axis, therefore 

approximately 0.35mm to 0.4mm. By comparison, the cornea is 0.5mm to 0.6mm in 

thickness. The reservoir is thinner superiorly, and thicker inferiorly, indicating a degree of 

downward displacement of the lens. This is a normal feature with non-ventilated RGP 

ScCL fitting and does not usually have any detrimental effect (Courtesy of Scott Hau) 

bubble. If there is insufficient clearance, 

corneal contact zones may reduce comfort 

and tolerance. Increasing the OZS or OZP by 

0.25mm alleviates a compressive central 

contact zone to give corneal clearance. 

Conclusion 

This is paper intended to provide an introduction 

to modern scleral contact lens practice, 

principally to outline changes in fitting 

RGP materials their application can be made 

at all grades of pathology where benefits 

can be seen. There remain some problems, 

and commitment to clinical practice is a 

prime requirement. The pathology may be 

active or progressive, so close liaison with 

ophthalmology is essential. A small number 

of practitioners are needed to maintain a 

functional service, but those who are not 

directly involved should also be aware of the 

significant developments in recent years. 

31 | October 20 | 2006 | OT



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Gas-permeable scleral contact lens 

therapy in ocular surface disease. Am J 

Ophthalmology, (2000), 130, 25 - 32. 

14) Rosenthal P, Cotter JM, Baum J. 

Treatment of persistent corneal 

epithelial defect with extended wear of 

a fluid-ventilated gas-permeable scleral 

contact lens. Am J Ophthalmology, 

(2000), 130, 33 - 41. 

15) Tappin MJ, Pullum KW, and Buckley RJ. 

Scleral contact lenses for overnight 

wear in the management of ocular sur 

face disorders. Eye, (2001). 15, 

168-172. 

16) Rosenthal P, Cotter J. The Boston 

scleral lens in the management of 

severe ocular surface disease. 

Ophthalmol Clin North Am 

(2003);16:89-93 

17) Fine P, Savrinski G, Millodot M. Contact 

lens management of a case of Stevens- 

Johnson syndrome: a case report. 

Optometry (2003) Oct; 74:659-64 

18) Looi AL, Lim L, Tan DT. Visual rehabili 

tation with new-age rigid gas-perme 

able scleral contact lenses - a case 

series. Ann Acad Med Singapore 

(2002);31:234-7 

19) Contact Lenses, edited by Anthony 

J Phillips and Lynne Speedwell, 

Publishers Elsevier, Chapter 15, Scleral 

Contact Lenses, by KW Pullum, 

pp 333 - 353. 

Acknowledgements 

The author is grateful for the assistance of 

the cornea consultants at Moorfields and 

Oxford Eye Hospitals, and for their support 

over many years in a long-term project 

modernising scleral lens practice and developing 

new clinical and manufacturing techniques. 

Figure 10 is courtesy of Scott Hau, 

senior optometrist, Moorfields Eye Hospital. 

For further information 

contact address: 

Ken Pullum, 73 Railway Street, Hertford, 

Hertfordshire, United Kingdom, SG14 1RP, 

(kenpullum@btinternet.com, 

kenpullum@tiscali.co.uk) 

Continuing 

education and 

training initiative 

For all CET 

Queries please 

contact: 

Jessica 

Buckingham 

CET, 

McMillan-Scott, 

9 Savoy Street 

London, 

WC2E 7HR 

Telephone: 

0207 878 2412 

Fax: 

0207 379 7118 

E-mail: 

jessica@mcms 

london.co.uk 

32 | October 20 | 2006 | OT



Module questions 

Course code: c-4090 

Please note, there is only one correct answer. Enter online or by form provided. 

1. For a highly irregular corneal topography would you 

try as first choice... 

a. Non-ventilated impression RGP scleral lens? 

b. Preformed fenestrated RGP scleral lens? 

c. Fenestrated impression PMMA scleral lens? 

d. Non-ventilated preformed RGP scleral lens? 

2. What is the optimum corneal clearance for a 

non-ventilated RGP scleral lens? 

a. Not more than 0.1mm 

b. Not less than 1.0mm 

c. Between 0.2mm and 0.3mm 

d. Between 0.4mm and 0.9mm 

3. If the BSR is changed from 13.50mm to 14.50mm 

without altering the OZP, would you expect... 

a. Increased apical clearance 

b. Reduced apical clearance 

c. There would be no difference 

d. There would be increased vaulting from the scleral zone 

4. What is the most probable objective when 

fenestrating an RGP scleral lens? 

a. To enable easier handling 

b. To increase apical clearance 

c. To create corneal contact 

d. To give a crescent-shaped bubble under the lens 

5. What is the usual objective when fenestrating a 

PMMA scleral lens? 

a. To give a crescent shaped bubble 

b. To increase apical clearance 

c. To facilitate oxygenated tear exchange 

d. To create corneal contact 

6. What would be the reason for considering a scleral 

lens in moderate keratoconus? 

a. To improve on vision achieved with a corneal lens 

b. To give increased oxygenation 

c. To alleviate corneal contact 

d. To create corneal contact 

7. Comparing small and large diameter non-ventilated 

scleral lenses, would you expect... 

a. More limbal clearance with the smaller lens? 

b. More apical clearance with the smaller lens? 

c. Better tear pool retention with the larger lens? 

d. The smaller lens to be more stable on the eye? 

8. What is the most common modern indication for 

scleral lenses? 

a. Aphakia 

b. High myopia 

c. Keratoconus 

d. Corneal transplant fitted post-operatively 

9. What is meant by the term sealed in the context of 

scleral lens practice? 

a. Near perfect alignment to the cornea 

b. Near perfect alignment to the sclera 

c. A lens retaining an air bubble-free tear pool 

d. A lens which is very difficult to remove 

10. Under what circumstances could a PMMA scleral be 

arguably preferable to an RGP scleral? 

a. For keratoconus 

b. Never 

c. For aphakia 

d. For work in dusty environments 

11. If the BSR is changed from 14.50mm to 13.50mm, & the OZP 

is increased one clinically significant step, would you expect... 

a. An 0.25mm increase in the apical clearance? 

b. A 0.50mm or greater increase in the apical clearance? 

c. No change in the apical clearance? 

d. A reduction in apical clearance of 0.25mm? 

12. What would be the probable outcome of reducing the diameter 

of a non-ventilated RGP scleral lens from 23mm to 18mm? 

a. Increased apical clearance 

b. More decentration of the lens 

c. An apical contact zone 

d. More chance of the lens falling out 

An answer return form is included in this issue. 

It should be completed and returned to: 

CET initiatives (c-4090), OT, McMillan Scott, 9 Savoy Street, London, WC2E 7HR by November 15. Under no circumstances will forms received after this date be 

marked – the answers to the module will be published in our December 15 issue. 

OT Book Shop 

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You can do this by calling our customer services team on 020 7878 2300 and ask for the Angela or Louise in the OT Bookshop. 

Also you can log on to www.optometry.co.uk and select OT Bookshop. 

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33 | October 20 | 2006 | OT

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