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VCH-1 Corneal Hydrometer

Fast and accurate measurement of Corneal Refractive Index during Surgery..... 

All refractive surgery involving the cornea relies on an accurate measurement of corneal Refractive Index. Many procedures assume the Refractive Index is constant at around 1.376 and its value is unaffected by surgery.

In truth, the Refractive Index:
i) increases from the endothelium, across the stroma and into the epithelium.
ii) of the stroma is raised in older patients.

You have all the individual details of the eyes you treat but you do not have the individual Refractive Index.

This is closely associated with water content of the cornea. All forms of refractive surgery can alter the water content of the cornea - Excimer laser surgery dehydrates the cornea and the VCH-1 will tell you how much water has been lost.

The VCH-1 measures Refractive Index in a simple, minimally invasive fashion, with an extra readout of water content. It can be used in all forms of surgery involving either lasers, inlays or grafts. 

The future of refractive surgery calls for a simple device to measure the Refractive Index of the cornea:

i) to further customise and improve treatments.
ii) to enhance the accuracy of surgery.
iii) to reduce the rate and incidence of retreatment and gain a better understanding of the water balance of the individual cornea.

The VCH-1 has been designed and thoroughly tested in clinical trials to fulfil these goals.

All types of refractive surgery can affect the water content of the cornea. Changes in the water content, or hydration, can affect corneal biomechanics, influence the post operative refraction and optical quality of the eye.

The VCH-1 Corneal Hydrometer estimates the corneal water content by firstly measuring Refractive Index and from this, calculate the water content using an appropriate algorithm. The zone of measurement consists of a round, 4 millimetre wide, illuminated, flat, sterile glass region that is placed directly onto the tissue.

The VCH-1 Corneal Hydrometer is a critical angle refractometer that can display and continuously check the light distribution at the region of contact in order to derive a Refractive Index, hence the water content. Once the device detects the measurement, it emits an audible signal informing the surgeon to remove the probe. Both the Refractive Index and water content values are displayed.

When performing LASIK, after lifting the flap this hand held device can be placed directly onto the Stromal bed to check the water content of the individual cornea. By repeating the measurement after photoablation the device will indicate the amount of dehydration that occurred in this single case.

The VCH-1 Corneal Hydrometer can be used in other corneal procedures such as: LASEK, EpiLASIK, PRK, Intracorneal Inlays and Grafts. If required, the device can also be used to gauge the water content of Hydrogel contact lenses in-situ, for example in therapeutic cases involving Bandage lenses.

The device can assist in gaining a better understanding of the effects of surgical procedures in specific cases:

i) Stromal Hydration is reduced in older patients and confirmed using the VCH-1 Corneal Hydrometer.
ii) Anterior Stroma is relatively dehydrated compared with the Mid-Stroma and confirmed using the VCH-1 Corneal Hydrometer.
iii) In the future, a customised Refractive Surgery using the VCH-1 Corneal Hydrometer.

Technical Specifications Download Brochure
  • Measure Refractive Index of the cornea in vivo
  • Estimate water content of the cornea in vivo
  • Measure Refractive Index and water content of hydrogels in-situ
  • Measure Refractive Index and water content of synthetic corneal inlays
  • Validated against advanced lab and bench refractometers
  • Useful for clinical and lab based studies on all corneas
  • Fast and accurate



Index Instruments USA

Tel: +44 (0)1487 814313 Fax: +44 (0)1487 812789
Index Instruments Ltd. Bury Road Industrial Estate, Old Station Road,
RAMSEY, Huntingdon, Cambridgeshire, PE26 1NF, England

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