The College of Optometrists

Keratometers measure the radius of curvature of the anterior (front) corneal surface of the eye. They should permit the quick and convenient measurement of the diameter of the cornea, which allows the practitioner to judge the volume of the eyeball. These instruments were particularly valuable when prescribing and fitting spectacles as the lens vertex and the corneal vertex must be in harmony. More latterly however they have been used mainly by contact lens practitioners.

 

Our oldest keratometer (on the left) is the Pfister & Streit Ophthalmometer, a Swiss keratometer from 1904 based on the classic design of Javal and Schiøtz (1881). Made of black metal, with a brass curving arm, the light units are propelled by a revolving balloon-shaped wooden knob. The sliding tripod stand is fixed to a wooden base with a head rest and chin rest adjustable for height. There is also a black metal swinging occluder and bakelite electical fittings which may have been added later. (Formerly in the Keeler Collection).

 

The Sutcliffe New Keratometer was a heavy beast on an iron tripod stand. Developing out of the Chambers-Innskeep (Chicago) model of 1899, it featured a head rest, single eyepiece, astigmatism dial and lamp unit on a swivelling base. The one at the top right is from circa 1907.

 

The object to the left is a slightly later development of the same instrument, dating from circa 1910. These instruments were designed by J.H. Sutcliffe, founder of the museum. They must have taken up a lot of space in the consulting room.

 

Sutcliffe's keratometers improved upon the Javal-Schiøtz designs up to that date in that both meridians could be measured simultaneously. It did this by means of prisms that could be moved parallel to the instrument's axis. In this way it countered any error that might occur if the patient's eye moved during the examination.

 

Look on the right again and you'll see the Sutcliffe Self-Recording Keratometer. It has a distinctively 'modern' look with its triangular base. There is a central spindle and revolving cylinder plus a brass circular scale marked in dioptric and radial units (c.1907-9).

 

The large parabolic bowl keratometer to the left is an example of another commonly found type.It was made in America by F.A. Hardy & Co. and comprises black painted metal with a polished brass stem, scale and draw tubes. The separate base has an adjustable wooden chin rest (on a brass spring ratchet), leather padding at forehead level, two swing-over occluders and four two-pin power fittings at each corner. (Formerly in the Keeler Collection).

 

By contrast Dr. Reid's Pocket Ophthalmometer is a miniature keratometer by Kelvin & James White Ltd, just 10cm long, in black metal and brass with a small ivory scale and milled edge wheel to adjust the pointer mechanism. This example was formerly used in the Glasgow Eye Infirmary and we would love to hear from anyone who can tell us more about its date and designer.

 

Probably the best known instrument in the post war period was still the Javal-Schiøtz Ophthalmometer, now known in the business simply as a 'Javal', which was available under the name of various suppliers including Haag-Streit and Woodlyn. In 2003 the Museum was given the model used at the Stepping Hill Hospital in Stockport.

 

 

---

 

The first Keratometer

 

Jesse Ramsden was the first English optician to produce a keratometer, expressly for the purpose of 'proving' Kepler's theory that accommodation of the eye was due to a change in corneal curvature. Ramsden threw it away when he discovered the sad truth. His instrument was apparently based on Ole Rømer's heliotrope, a split mirrored device for measuring the sun. The first Keratometer however was produced in Paris in 1728 though it could measure various other dimensions of the eye (for instance the anterior chamber) so it was truly an 'ophthalmometer' in a way that many of the keratometers that subsequently bore the ophthalmometer name were not.

 

A keratometer provides readings of corneal curvature in dioptrical values, but since contact lenses were ordered and manufactured on the basis of the radius curvature (in millimetres), a conversion was always needed.

 

 

Revolving cardboard conversion chart, double sided (for power readings 36.00-43.87 or 44-52.00) within three-part folder including instructions for the Bausch & Lomb Keratometer. 1960s